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An architecture for in situ production of bioplastics for habitats on Mars

Artistic representation of the Mars Seed biofoundry producing surface habitats. Abiotic infrastructure creates a feedstock entirely from in situ resources. Biotic infrastructure uses a bioprocess to convert this feedstock into bioplastic polymer. Radiation-shielded and pressure-holding surface habitats, safe for human habitation, are built with this bioplastic. Credits: Pioneer Labs, Figure 1 from paper entitled “Mars Seed: A Reference Architecture for Biomanufacturing Habitats from Martian Resources”

Pioneer Labs, a nonprofit startup in Emerville, California has developed a detailed plan called Mars Seed for making plastic building materials on Mars using local resources and specially engineered microbes, so Mars settlers don’t have to ship every kilogram of habitat material from Earth. In a paper on the company’s website, researchers Devon A. Stork, Harley Greene, and Una Nattermann describe a complete system that could autonomously turn Martian air, ice, and regolith into a bioplastic called polyhydroxybutyrate (PHB). The plastic would then be used by robots to build pressurized, radiation-shielded habitats before any crew arrives. The authors argue that the equipment needed for this process pays for itself, in terms of mass and power, within about two Earth-Mars launch synodic periods (roughly 52 months) compared with simply shipping finished plastic from Earth. After that, the system could keep producing material until the machines wear out (if not maintained), without needing more supplies from home.

Human installations on Mars will need huge amounts of materials for habitats, life support, and other uses. As we know, shipping everything from Earth is extremely expensive because every kilogram launched and delivered to Mars costs a great deal of fuel and money. For decades, mission planners have been researching in situ resource utilization (ISRU) using materials sourced on Mars. The most famous example is MOXIE, a device on the Perseverance rover that turned Martian atmospheric carbon dioxide into oxygen. Biological ISRU could make plastics, food, or medicines, but until now no one had shown a full, numbers-based analysis proving that biology could actually produce useful amounts of material at a competitive cost. Mars Seed does exactly that by focusing on one end product: bioplastic for habitats.

The overall idea is straightforward. A lander delivers about 20 metric tons of equipment to a mid-latitude site on Mars where shallow ice is available under a few meters of soil. Robots unload and assemble everything, including a 40-kilowatt nuclear fission reactor ( in line with NASA’s Fission Surface Power project) that supplies the needed electricity. The system then makes a liquid feedstock from three local source materials: water from melted ice, acetate (a salt derived from acetic acid) made from atmospheric carbon dioxide, and minerals leached from Martian regolith. Four 1,000-liter bioreactors grow an engineered bacterium that turns the feedstock into PHB-rich biomass. Half of that biomass is mixed with more regolith and extruded into a strong outer shell; the other half is purified into pure plastic and formed into a flexible inner liner that holds air pressure. The finished habitat is a half-cylinder about 5 meters wide and 15 meters long, that is subsequently buried under two meters of loose regolith for radiation and thermal protection. Each habitat provides about 75 square meters of floor space, enough for two people under NASA standards of roughly 35 square meters per person. After about 1,500 Martian sols (roughly 50 Earth months), the system has built 870 square meters of livable area—more than an equal mass of shipped plastic could provide.

PHA is not a boutique lab polymer. Many acetate-using, oxygen-respiring bacteria make it natively as a carbon-storage granule. After harvest, the granules can be extracted with relatively little consumable chemistry, or in some schemes extruded with the biomass itself. Copolymers span a useful mechanical range, from stiff to elastomeric. Proposed uses for application on Mars include 3D-printable filament, films, fibers, greenhouse coverings that transmit visible light while blocking UV, and even airtight structural elements.

Back to the Mars scenario details: setup takes about 90 sols. The reactor is up and running in the first 30–40 sols. A Rodriguez well (Rodwell) melts a cavity in the ice using waste heat from the reactor and pumps up liquid water. The first complete habitat appears around sol 210. Robots based on designs like the Astrolab FLEX rover or NASA’s RASSOR excavator haul roughly 4 tonnes of regolith per day: 800 kilograms for leaching nutrients, 50 kilograms as filler for the shell, and 3,200 kilograms for the radiation overburden. These vehicles are budgeted at about 1,000 kilograms and 1.4 kilowatts continuous power.

Water is essential initially but is mostly recycled. The Rodwell is sized for up to 400 liters per day, though the system only needs about 200 liters of fresh water daily once recycling is running. Mechanical vapor recompression is used to boil the spent culture liquid under low pressure and recondense it into clean water, recovering 80–90 percent (about 1,800 liters per day). The equipment for this step is estimated at 650 kilograms consuming 1.3 kilowatts. The leftover brine might later be useful for making acids or bases.

Carbon and oxygen are extracted from the atmosphere, which is 95 percent carbon dioxide. A two-stage electrolysis process converts it into acetate and oxygen. The overall daily reaction is roughly 48.4 kilograms of CO₂ plus 19.8 kilograms of water yielding 33 kilograms of acetic acid and 35.2 kilograms of oxygen. Stage 1 is a solid-oxide electrolyzer similar to a scaled-up MOXIE; it splits CO₂ into carbon monoxide and oxygen, drawing 6.6 kilowatts and weighing 850 kilograms. Stage 2 takes the carbon monoxide, mixes it with water in an alkaline electrolyzer, and produces acetate (plus more oxygen). This step draws about 20 kilowatts and, with spares for membranes that wear out, accounts for roughly 5,250 kilograms. Excess oxygen beyond the 11 kilograms per day needed by the bacteria can be used for breathable air in habitats. The process is based on commercial Earth technology being developed for sustainable “electro-agriculture,” but it still needs work to run reliably and robotically on Mars.

Minerals come from simply leaching the Martian soil. Mixing 400 grams of regolith with one liter of water and letting the solids settle produces a liquid medium that supports growth of the chosen microbe, even though it contains about 30 millimolar toxic perchlorate. Two 1,000-liter batches per day require an 1,200-liter stirred tank weighing about 550 kilograms and using 0.5–1 kilowatt. No complex chemical processing is needed because near-surface Martian fines are already fine enough.

The microbe is Pioneer Labs’ evolved strain of Cupriavidus necator called sPL.001. Lets pause here for a deep dive, because this engineered bacteria is the linchpin in the company’s strategy. In a September 2026 preprint on bioRxiv another team from the company (Fatima R. Martin, Max G. Schubert, and Harley Greene) describe how they engineered sPL.001 and validated production of bioplastics using simulated 100% in situ Mars resources. The end products proposed in the September paper were greenhouses made of bioplastics, an obvious need for growing crops to support the Mars Seed installation.

Minimal infrastructure for bioplastic production from Martian resources. A bioreactor deployed to Mars could support biomanufacturing microorganisms entirely from Mars derived resources: inorganic nutrients from the regolith, water from ice, and oxygen and a carbon sourced from the atmosphere. Microbially produced bioplastic from these in situ resources could be used to construct greenhouses or other structures. Credit: Figure 1 with minor edits from preprint published on bioRxiv. Copyright Pioneer Labs, CC BY-NC 4.0

sPL.001 started as Cupriavidus necator H16, a common soil bacterium that already makes PHB plastic from acetate. The team first used a parent strain that was slightly engineered by inserting a small piece of DNA into its genome, which modestly improved its tolerance to the toxins in Martian regolith simulant. The insert also carried a kanamycin-resistance marker so they could spot contamination. It did not add a new plastic-making pathway.

They then evolved that parent for about six weeks. Cultures were grown in flasks of harsh Defined Mars Media (a Martian regolith simulant developed by Pioneer Labs) infused with acetate and transferred into fresh medium every 48 hours. For the first three weeks the mix was 14 x DMM (14 times the baseline concentration) and 1.25% acetate. For the last three weeks it was raised to 20 x DMM and 1.75% acetate. They estimate about 10¹² cell divisions in total.

From the final populations they picked individual colonies, sequenced them, and kept the one that grew to the highest density under the harshest conditions. That isolate is sPL.001. Its extra plastic output comes mostly from surviving and multiplying where the parent stalled, not from a redesigned PHA pathway.

On Earth this species can store up to 90 percent of its dry weight as PHB. In the Pioneer Labs tests with acetate and a Mars-simulant medium, it produced about 5 grams of PHB per liter in 29 hours, with cells that were 70 percent PHB by weight. Scaled to 2,000 liters of medium and 33 kilograms of acetate per day, the four bioreactors are expected to yield about 14 kilograms of biomass containing 10 kilograms of PHB daily—an efficiency of 0.3 grams of PHB per gram of acetate. Each bioreactor is a tall, thin stainless-steel tank (about 3 meters high and 0.75 meters in diameter) weighing 550 kilograms and drawing 0.4 kilowatts, for a total of 2,200 kilograms and 1.6 kilowatts.

Each habitat needs about 1,300 kilograms of PHB (or 1,800 kilograms of biomass). The outer shell is a corrugated composite of 13 percent biomass and 87 percent regolith, printed in a thin wall with deep corrugations so it can support two meters of loose overburden. Under Martian gravity that overburden exerts about 11 kilopascals; the design aims for a safety factor of 1.5. The shell uses roughly 860 kilograms of biomass and 5,800 kilograms of regolith and has a mass of about 6,600 kilograms. Precedent comes from vacuum extrusion tests of regolith mixed with plastic. The inner liner has two parts: a 1.5-millimeter cast film membrane (about 440 kilograms) and woven PHB fiber straps (about 220 kilograms) that take the pressure load. The habitat atmosphere is planned at 57 kilopascals (in accordance with NASA exploration standards) with a safety factor of four. The straps are sized using measured fiber strengths around 740 megapascals. Forming equipment for both shell and liner is estimated at roughly 2,000 kilograms and under 3 kilowatts combined.

The full equipment list totals 20,000 kilograms and stays within the 40-kilowatt reactor output. The reactor itself is 6,000 kilograms (30 percent of the mass). Acetate electrolysis is the next largest item and consumes about two-thirds of the electricity. All biological equipment together is only about 15 percent of the mass and less than 10 percent of the power. Most of the cost is therefore in the abiotic systems that any crewed mission would need anyway, i.e. power, water, oxygen, and robotics.

Compared with shipping plastic, the advantage appears after roughly 1,400 sols. An alternative mission that lands the same 20 tonnes but uses most of it as raw polymer (plus a smaller power system and the same construction robots) can build about 810 square meters before the plastic runs out. Mars Seed reaches 870 square meters by the two-synodic mark and, if it keeps running, reaches 2,100 square meters in ten years—the equivalent of shipping another 43 tonnes of polymer and equipment. A smaller “Mini Mars Seed” version sized only for a six-person crew (210 square meters) needs about 8,100 kilograms and 10 kilowatts of power and still beats an equivalent mass of plastic transported to Mars once the shipped stock is exhausted.

Sensitivity checks show that improving the microbe’s yield or speed gives the most practical gains. Better reactor or electrolyzer efficiency, or stronger thinner habitat walls, also help, but some of those improvements are harder to achieve. The same core hardware could later make other products—different bioplastics, chemicals, or even proteins—by changing the organism or downstream steps, though sugar-based or photosynthetic routes would need extra equipment.

What I found amazing is that Pioneer Labs CEO Erika Debenedictis, who has graced SSP previously on terraforming Mars, claims in a blog post that after landing just one rocket on Mars, the process utilizing sPL.001 could build a city over a period of just 4 years. And crucially, the organism dies quickly if spilled on the Martian surface and has an extremely low chance of spreading (around 10-24 per cell), so NASA’s Office of Planetary Protection will likely consider the risk manageable compared with a human crew’s microbiome.

“…we chose an organism that would be tremendously useful when fed by humans and grown inside a bioreactor on Mars, but that has absolutely no chance whatsoever of growing outside.” – Erika Debenedictis

The paper lists open questions: how much regolith chemistry varies by site, whether the microbe stays productive over years of reseeding, how well yields hold at full scale, how much cleaning the tanks need, what robotics are truly required, how the finished plastic and composite perform under Mars conditions (gas leaks, strength, UV, perchlorate residues), and how the design compares with ice or sulfur binders. Many subsystems already have Earth or flight precedents, but all need further development for long autonomous operation on Mars.

The Mars Seed concept shows that a biology-centered system can be competitive with shipping materials from Earth when taking into account every step in the ISRU process flow, from local feedstock to finished habitat. The bacteria themselves are a small part of the mass and power budget; the real enabling components are nuclear power, locally sourced water, and atmospheric carbon fixation. By making the equipment costs explicit, the architecture gives mission planners a concrete baseline which they can adapt or improve upon.

Several members of the Pioneer Labs Team are contributors to Green Mars, a group of scientists exploring what it will take to enable life to thrive on The Red Planet.

Panorama of the Martian landscape at dawn captured by the Mastcam on NASA’s Curiosity’s rover on Aug. 11, 2026. With the right equipment and the Pioneer Labs engineered microbe sPL.001 delivered by a single rocket, these resources could be converted into bioplastics to build a city on Mars. Credits: NASA/JPL-Caltech/Malin Space Science Systems

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Bridging the silicon gap for autonomous lunar manufacturing

Systemic flowchart depicting a lunar machine ecology. The diagram illustrates the thermodynamic coupling between a 150 kW sodium-cooled nuclear reactor and the industrial processing blocks [molten regolith electrolysis (MRE), vacuum distillation (VDM), alongside the hierarchical control pathways from the Broodmother (BM) to the Constructive Automata (CA) swarm. Credits: Velin Yordanov and Georgi Sotirov. Figure 1 from open access article in Acta Astronautica with minor text edits / Used under CC BY 4.0

An autonomous factory on the Moon cannot be sustainable if all the components have to be shipped from Earth because, as we all know, the cost of launching mass off our planet and landing it on the Moon can be punishing. Traditional plans assume that high-tech components will be continuously resupplied from the home world. A recent journal pre-proof in Acta Astronautica by Velin Yordanov and Georgi Sotirov from the Space Research and Technology Institute at the Bulgarian Academy of Sciences describes a more elegant solution. They call the core problem the “Silicon Gap” and propose a hierarchical autonomous architecture designed to narrow it dramatically during the early stages of lunar industrialization.

What Exactly Is the Silicon Gap?

Modern electronics, precision sensors, radiation-tolerant processors, high-tolerance actuators, seals, and reactor control hardware require purity levels, cleanrooms, and fabrication chains that early lunar infrastructure simply cannot reproduce. Conventional silicon chips are also vulnerable to radiation-induced single-event upsets (bit flips). The authors define the Silicon Gap as the mismatch between the full set of high-complexity subsystems required for long-duration autonomous growth and the much smaller set of bulk materials and simple components that an initial in-situ resource utilization (ISRU) system could realistically manufacture.

They partition components of the model into three categories:

  • Earth-supplied high-complexity items: reactor core and controls, radiation-tolerant processors, precision sensors and communications, high-tolerance bearings and seals, initial rover electronics and spares. These stay imported.
  • In-situ producible low- and medium-complexity items: iron, nickel, aluminum, silicon feedstocks, oxygen, hydrogen, potassium hydroxide (KOH) electrolyte precursor, structural chassis, panels, pylons, wires, mirrors, rails, and selected battery and frame elements. These are explicitly modeled in the production chain.
  • Hybrid components: motors, relays, simple logic carriers, sensor housings, battery assemblies. Structural mass is sourced locally; precision inserts remain Earth-supplied.

The goal is not zero imported mass. It is to decouple the recurring replacement burden from the linear growth of total infrastructure. As the colony expands, most of the increasing mass (structures, batteries, simple robots) comes from local regolith while Earth resupply is reserved for the high-value cores (e.g. CPUs) and inserts that cannot yet be made on the Moon. At some point, companies like Besxar will be manufacturing semiconductors in space, which could significantly lower the cost of transporting these components to the Moon. But until lunar surface chip production infrastructure matures, the silicon gap needs to be addressed.

The Hierarchical Architecture: Broodmother, Praetorian, and Constructive Automata

The solution modelled by Yordanov and Sotirov concentrates scarce complexity in a protected central node called the Broodmother (BM). This is not the arachnid horror queen of video games, but a benevolent machine overseer – an industrial and control hub that retains the imported processors, precision metrology, reactor controls, and the manufacturing tools needed to turn regolith into usable parts. It houses the energy system, material inventories, job scheduler, and assembly capability.

Repetitive field work such as excavation, loading, and transporting of regolith plus other construction support activities are handed off to a swarm of simpler robots dubbed Constructive Automata (CA). These are deliberately limited robotic machines. Instead of full onboard microprocessors, they rely on physically encoded instruction media—essentially optomechanical readers and relays with finite-state execution. The BM writes or rewrites the physical “scripts” (duty cycles, movement routes, construction sequences) when a CA returns for charging or servicing. This keeps high-level planning centralized and reduces the imported high-complexity microprocessor content in each field unit. In the optimistic target scenario, a CA could be up to 95% ISRU-sourced by mass, with only about 5% precision chip inserts supplied from Earth.

An intermediate rover, what the authors call a Praetorian (again, not the malevolent elite imperial guard in ancient Rome, but a middleware mobile extension of the BM), which handles scouting, heavy logistics, marker placement, and recovery of failed or blocked CAs. The overall control flow is hierarchical: the BM issues task orders, CAs execute them via finite-state machines, and physical cues (tracks, rails, piles of regolith, markers) provide a low-bandwidth stigmergic layer that complements direct commands.

The authors acknowledge up front that the architecture has a major risk: the BM is a single-point-of-failure node. Partial failures might be repairable by the Praetorian replacing modules or reconnecting interfaces. Critical failure of power control, the scheduler, or the main manufacturing interface would strand the local colony. Future robustness would require duplicated nodes or greater manufacturing capability which are not addressed by the present model.

Power: A Compact Sodium-Cooled Fission Reactor

Continuous and sufficient baseload power independent of the two-week lunar night is essential, so solar energy and battery storage would not work on their own. The design for this model uses a sodium-cooled nuclear reactor (SNR) with a nominal electrical cap of 40 kWe inside a 150 kWe thermal envelope. Effective conversion efficiency is targeted in the 25–30 % range typical of Stirling-based compact fission surface power concepts already studied by NASA. Roughly 850 kg is allocated to the reactor and power-conversion envelope inside the BM. Admittedly, this is an aggressive approach that assumes partial regolith shielding after landing and does not include a full multi-ton human-rated system with long transmission lines and extensive redundancy.

Thermal energy is coupled directly to high-temperature processing. Radiator area estimates are optimistic (around 20 m² at high temperature) because a substantial fraction of heat is absorbed by the industrial processes rather than rejected to space. The model treats power as a scheduling constraint: jobs start only when both materials and instantaneous electric margin are available.

The Broodmother only works well on activities in its local vicinity. To facilitate work farther away and to augment the nuclear power source, the design adds an extra solar heating system: a mirror grid made from simple reflective panels that direct sunlight onto the processing equipment. TransAstra is already developing a similar component called the Sun Flower Power Tower. During the lunar day this extra heat and light helps melting, electrolysis, and other high-temperature work, so the reactor does not have to supply all of the energy.

Iron-nickel (Fe-Ni) batteries based on tried and true Edison chemistry are chosen for CA mobile storage. They offer far lower energy density than lithium-ion (30–50 Wh/kg versus 150–250) but exceptional cycle life (5,000+), tolerance to abuse, and high lunar manufacturability. Anode and cathode plates are formed from refined Fe and Ni; KOH electrolyte comes from local potassium processing. A 15 kg CA needs roughly 240 Wh for a 12-hour duty cycle at 20 W average draw, translating to a battery mass of about 6.8 kg, nearly half the robot’s mass.

Turning Regolith into Feedstocks

To convert the resources in lunar soil into useful materials the processing chain is modelled in three stages:

  1. Molten Regolith Electrolysis (MRE) heats regolith above 1400 K and applies electrical potential to dissociate oxides, producing oxygen and a mixed metallic melt. Phase separation by density yields an Fe-rich fraction and a secondary stream. Modeled throughput is roughly 100–120 kg of regolith per day under realistic duty factors (not the theoretical 120–180 kg at continuous full power). I’ve explored this process in previous posts here and here.
  2. Vacuum Distillation (VDM) and Molten Salt Electrolysis (MSE) refine the metals further. VDM separates the components in regolith by heating the mixture in lunar vacuum so impurities and metals separate by their respective vapor pressure. It is used to refine the metals further (e.g. Iron for chassis, pylons, rails, panels, other structures: Nickel for Fe–Ni battery electrodes and motor-related parts). MSE produces higher-purity silicon and aluminum. The aluminum is used in mirrors, panels, wires, optical/reflective parts, and thin films in the next process. The silicon is used in glass/optical substrates, logic carriers, and refractory-related parts.
  3. Vapor Deposition Assembly (VDA) takes the aluminum output from MSE and creates thin aluminum films used as substrates for the physical instruction media of the CAs. This method is similar Blue Alchemist, a process under development by Blue Origin for fabricating solar cells from lunar regolith.

The physical instruction media are the CA’s programs stored as a physical object, not as code in a microprocessor memory. In the architecture, each CA is a simple finite-state machine. It does not carry a radiation-hardened computer that stores tasks in RAM or flash. Instead, the Broodmother writes a task script onto a replaceable carrier. When the CA returns for charging or service, that carrier can be swapped or rewritten so the robot gets a new job. The VDA’s only role is to produce the substrate: refined aluminum is vacuum-deposited as ~50 µm film on a rotating surface. That film is the blank “tape” or card on which the instructions are then encoded.

Daily model yields using the scenario parameters include approximately 18.5 kg Fe, 8 kg Al, 0.8 kg Ni, 4.2 kg Si, 45 kg H₂O, plus oxygen, hydrogen, and a critical 0.15 kg of potassium. Potassium is a sharp bottleneck because it feeds KOH production for the Fe-Ni batteries. Without enough potassium, battery fabrication stalls and CA growth slows even if bulk metal inventories look healthy.

The approximate CA fabrication rate—one ~15 kg unit every 1–2 days—is a downstream scheduling result, not a direct conversion of regolith into robots. It requires simultaneous availability of refined metals, Ni and KOH for batteries, silicon-bearing feedstock for logic carriers, free manufacturing queue time, and sufficient electric power.

Mission Profile and Site Selection

The initial landing mass is assumed to be roughly 1,500 kg (850 kg reactor/power, 650 kg manufacturing and mobility). Site selection uses an orbital “Triple-Lock” remote sensing strategy combining neutron spectrometry and synthetic aperture radar for detection of hydrogen/water ice, gamma-ray spectrometry to find potassium (KREEP regions), and X-ray spectrometry to prospect for nickel enrichment. Polar locations such as Malapert Massif (South) or Mons Peary (North) are favored for proximity between the illuminated peaks and permanently shadowed regions containing water ice, an ideal location to supplement power from the nuclear reactor with reflected sunlight. Solar-assisted heating can offset part of the electrolysis power demand.

NASA’s Lunar Reconnaissance Orbiter image of Malapert Massif (left), an Artemis IV candidate landing region near the lunar south pole, captured on March 3, 2023. Credits: NASA Goddard Spaceflight Center/Arizona State University

Deployment proceeds in phases: orbital reconnaissance, landing and initialization, reactor activation and regolith shielding, initial MRE, first CA production, swarm expansion, and industrial expansion with mirror arrays and simplified transport infrastructure.

The Simulation Framework

An agent-based (CAs, Praetorian rovers), queue-based (BM job waiting list) reduced-order model coded using Python 3, couples energy supply, material inventories, manufacturing jobs, terrain, resource fields, and CA logistics on a 220 × 220 cell lunar grid. The terrain is a smoothed random field (i.e. statistically generated but spatially correlated topography, used as a first-order stand-in for rolling lunar hills); resources are grouped in clustered deposits, meaning the materials sit in patches, like pockets of ore or ice rather than a uniform distribution.

The BM runs a primarily deterministic scheduler with TinyML-style priority biasing based on energy margin, scarcity, utilization, and backlog. As stated previously, CAs are finite-state machines with several core states (e.g., idle, travel, harvest, return, charge, assist, failed) plus a few contingency states.

Success criteria were chosen to be deliberately narrow:

  • Energy closure (no persistent deficit).
  • No permanent scheduler deadlock.
  • Local production of the CA parts and infrastructure.
  • Completion of milestones in a staged progression (first CA, multi-CA operation, shelter, mirror field, stable power-supported growth).
  • Bounded, recoverable CA failures via redundancy or Praetorian rescue.

A baseline 180-day run at 40 kWe with nominal resource abundance shows gradual rather than explosive growth. Power is not the dominant bottleneck near baseline. Lower electrical caps (20–30 kWe) produce zero CAs in the first 30 days and hundreds of power-blocked jobs. At 35 kWe partial recovery appears; at 40 kWe the system reaches nine CAs with no power blocks. Potassium scarcity creates a different failure mode: bulk processing continues but battery and CA production stall. A stress case disabling Praetorian recovery after day 12 and accelerating motor failures shows that even with a powered BM producing six CAs, unrecovered faults can drive operational worker count to zero.

The model therefore identifies distinct limiting mechanisms: electrical power, process energy intensity, K/Ni availability (especially for batteries), BM manufacturing queue capacity, and mobile-agent logistics and recovery. Growth follows the narrowest link in the chain: resource access → MRE/refinement → KOH/Ni → batteries → CA assembly → deployment.

The Importance of the Physical-Logic Approach

By replacing full microprocessor stacks in the CAs with optomechanical readers and relay-based finite-state machines, the architecture shifts the dominant failure modes from radiation-induced bit flips toward mechanical wear, dust contamination, contact degradation, and actuator faults. High-complexity planning and metrology stay inside the protected BM. The simulation demonstrates that agents with only about ten active states, when properly coordinated, re-tasked, repaired, and supplied by the central node, can still contribute to colony-scale growth. The key takeaway being: low-complexity field units do not need independent high-level intelligence if they are embedded in a hierarchical production and logistics loop.

Caveats, Boundaries, and the Road Ahead

The paper is clear on its limits. It is a system-level architectural study and reduced-order simulation, not a high-fidelity engineering design or flight-ready blueprint. The variables are scenario parameters chosen for internal consistency. The results show architectural plausibility within the model, not validated reactor performance, process chemistry, or real-world guarantees. In addition, the reactor mass, radiator sizing, MRE yields, manufacturing tolerances, and CA reliability are not validated engineering results. The 40 kWe figure is aligned with NASA-class fission surface power studies, but the overall envelope is an optimistic estimate. Future work must add detailed electrochemistry, thermal-fluid dynamics, stochastic reliability, explicit BM partial-failure modeling, dust and thermal-cycling effects, and a full mass-ledger that quantifies how resupply flights can be avoided.

With those caveats firmly in place, the concept is worth examining in detail for planning lunar industrial operations. The proposed architecture is valuable, providing a clear partitioning of the system components that quantifies the residual Silicon Gap, reproducible simulation criteria, and an identification of the critical bottlenecks. The choke points are potassium for batteries and the system’s ability to rescue, tow, repair, or replace failed CAs so that individual robot failures, if not planned for and addressed, could accumulate into a collapse of operations.

The results of the study indicate that, under the stated assumptions, a hierarchical ISRU-driven bootstrap layer can maintain internal consistency: energy budgets close, the scheduler does not deadlock, local parts and infrastructure are produced, milestones are reached, and failures remain reasonably bounded.

In short, the work shows that early lunar industrialization need not wait for a complete terrestrial supply chain to be replicated on the Moon. By protecting the high-complexity core, manufacturing the bulk of the growing mass locally, and coordinating simple finite-state machines through a central node, a reduced-resupply architecture becomes conceptually plausible. Whether that approach survives the transition from reduced-order simulation to engineering reality is the next, much harder question. Clearly, more work is needed, but the framework at least gives future designers a coherent place to start.

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Pioneering the growth of space settlements

Conceptual illustration of Station 520, a 320 meter diameter rotating orbital space settlement constructed from Stellamer, a plant-based thermoset mixed with plant fiber fillers extruded via an additive manufacturing system. Credit: Orbital Construction Pioneers

At a presentation at ISDC 2026, Orbital Construction Pioneers (OCP) introduced the First Step Manufacturing System (FSMS): an orbital additive manufacturing system that could potentially produce segments for very large structures (on the order of a few hundred meters long) using a bio-material derived from plants grown and processed in orbit.

Why is this important? Humanity’s long-term expansion into the solar system cannot be sustained by continuous resupply from Earth. The cost, complexity, and sheer mass penalties of launching every kilogram of food, water, oxygen, fuel, structures, and spare parts out of Earth’s gravity well become prohibitive as missions move farther out from low Earth orbit. In situ resource utilization (ISRU) has long been recognized as the only practical path to sustainability.

OCP has developed the FSMS as a promising architectural response to this challenge. FSMS is an orbital fabrication platform whose core innovation is biological additive manufacturing. Hydroponic and aquaponic farms operating inside a rotating space station would generate plant biomass that serves as both binder and filler for Stellamer, a bio-derived thermoset polymer. This material could enable continuous, large-scale additive manufacturing of structural components in an artificial-gravity environment. The system simultaneously produces life-support commodities and specialized mission components, creating a symbiotic industrial-ecological ecosystem.

George Tyson, CEO of OCP, came on The Space Show on July 28th to discuss the company’s plans and progress to date with David Livingston and me, along with several members of The Space Show Advisory Board. Tyson spoke with us from his lab in Colorado City, Texas, on the development of Stellamer and showed samples of the material he’s tested. When asked about the technology readiness level of flight-ready hardware and plans for orbital demonstration flights, Tyson indicated that it was still in the early research stages but as soon as they have optimized the Stellamer formulation and are satisfied with the performance of their prototype printer, the next milestone would be validation of the equipment under microgravity conditions on a parabolic flight platform.

Tyson also made an exclusive media announcement. In partnership with Hawaii-based Exo-Scientific, the companies are forming the Interplanetary Regen Network (IRN), a multi-party consortium focused on the collaborative development of bioregenerative systems, advanced in-space construction techniques, and ISRU technologies to sustain human presence beyond Earth. Exo-Scientific provides integrated solutions in engineered aquatic life systems for closed-cycle cultivation, ISRU management, and the practical application and adaptation of Earth-proven sustainability principles to offworld environments. I asked Tyson if Exo-Scientific would provide the life support systems for OCP’s space stations via their aquaponic ecosystems, but he was under an NDA at this juncture, so could not comment on the question. Exo-Scientific was also a presenter at ISDC2026 on their Coral Wetlab concept. Clearly, the company’s systems could be synergistic and complementary to OCP’s technology and plans.

The IRN is soliciting discussions with potential consortium members, government partners, research institutions, and commercial clients interested in advancing bioregenerative systems, in-space construction, and ISRU capabilities for cislunar, lunar, and Mars applications.

OCP’s long-term plan for full-scale implementation of FSMS is to start with the construction of Station 520 in medium Earth orbit (MEO), a 320-meter-diameter rotating habitat that would generate lunar-level artificial gravity at one revolution per minute. The pressurized volume would be approximately 774,000 cubic meters, sufficient to house extensive farms, processing equipment, habitation quarters, and specialized manufacturing functions such as pharmaceutical production and thin-film fabrication. A large-format 3D printer would sit at the geometric center, capable of producing structural segments up to 50 meters across and 6 meters thick. These segments would clad the station’s primary truss frame and enable the fabrication of additional modules.

OCP envisions construction beginning with the launch of seven Version 3 Starship-sized vehicles (or equivalent) that would deliver the essential components for assembly. These vehicles would contain enough scaffolding for the station skeleton, hydroponics and aquaponics materials, the necessary items for the construction of the 3D printer located at the center, plant processing equipment, food, water, air, tools, and EVA suits used by the construction crew. A repair station for EVA suit and equipment maintenance would also be provided, including a small startup crew’s quarters and work area.

Once the vehicles reach MEO, the scaffolding would be employed to build the station skeleton while incorporating the seven vehicles themselves into the emerging framework. Appropriate items such as propulsion systems, electronics, pumps, and related equipment would be relocated from the vehicles to their permanent placement on the scaffolding. The tanks and cargo areas of the vehicles would then be connected to provide pressurized sections that serve as the initial farms. With these foundational elements in place, the station could be spun up to one-third rotation, allowing the hydroponic and aquaponic systems to be mounted and activated.

As plant material becomes available, the plant processing system would be assembled and activated. This system creates the material—thermoset epoxy and plant fibers—required for use in the printer. Using a mix of the station-produced thermoset and plant material, the outside skin and inside bulkheads would then be printed. As the outside of the station is skinned, additional sections would be enclosed and pressurized to accommodate new hydroponic and aquaponic farms. When the construction of the station is complete, rotation is increased to one rpm, and tenants could then be allowed to move in.

As stated previously, central to this entire sequence is the FSMS 3D printer, which would be integrated into the structure of the station. The printer will utilize materials grown and processed on the station. Printed items up to 50 meters across and 6 meters thick will be used to sheet the truss frame of the station. Beyond these large segments, the printer is also capable of printing other shaped parts of varying size, such as I-beams, triangles, tubes, tanks, and similar components, thereby creating various pressurized modules that will increase the size and volume of the station as well as support other applications. The printer will rely exclusively on station-derived thermoset bio-binder and plant-derived fillers, both of which would be hydroponically grown and processed on the station.

Illustration of Station 520 under construction in MEO. The top is in the process of being enclosed, exposing the internal scaffolding. Credit: Orbital Construction Pioneers

Once operational, Station 520 would become a self-sustaining ecosystem. Waste streams would be fully recycled; oxygen and water continuously regenerated; methane produced from biological waste; and plant fibers would become industrial feedstock. It is believed that outputs will exceed the station’s own needs and could be traded with visiting spacecraft, providing refueling, resupply, and waste-processing services. In this way, FSMS will transform Station 520 into a renewable manufacturing hub that could produce structural mass, life-support commodities, and mission-specific modules. It could become the first practical foundation for a non-Earth-centric orbital economy and simultaneously offer the United States a strategic industrial and defense platform in orbit. It is being positioned as a gateway to the Moon and Mars.

Tyson’s vision doesn’t stop in low Earth orbit. He shared with me a draft paper that he intends to submit for consideration as a presentation at ISDC 2027, of an economic model based on FSMS that lays the foundation for a space-based economy that could extend throughout the solar system. The rest of this post is based on his insights from that paper, with his generous permission.

Progression of Orbital Economic Development

Orbital economic development will follow a predictable sequence analogous to the terrestrial progression from subsistence agriculture to industry and then to commerce. The sequence will be shaped by mass constraints, the necessity of closed-loop life support, and the requirement for continuous production. FSMS will supply the architecture that will enable an orbital station to advance through each stage without reliance on Earth-supplied resources.

The initial stage will be biological sustainability. Hydroponic and aquaponic systems will generat food, oxygen, water, and biomass, forming the ecological base required for long-duration habitation. This stage mirrors early agricultural settlements in which reliable food production enabled population growth and the beginnings of specialization.

The second stage is industrial capability. FSMS converts biological output into structural mass, life-support commodities, and manufacturing feedstock. The transition is analogous to terrestrial industrialization, in which local production of steel, concrete, and machinery enabled large-scale construction and economic expansion. In orbit, manufacturing will break the launch vehicle fairing-size constraint and permit the creation of large rotating habitats, industrial modules, and specialized stations.

The third stage is economic expansion. Once primary and secondary outputs become established, tertiary services will emerge—logistics, crew support, data services, defense infrastructure, and interstation trade. These services will create economic gravity that attracts additional stations, missions, and commercial operators. Over time, specialized stations will form clusters, and clusters will form networks, producing a resilient orbital economy capable of supporting interplanetary operations. This progression will transform Station 520 from a single manufacturing node into a central hub of orbital commerce and will lay the foundation for sustained human presence in cislunar space and eventual expansion to Mars, the asteroid belt, and beyond.

Station 520 as the First Orbital Industrial Hub

Station 520 is designed from the outset to function as an industrial hub rather than a research outpost or mere logistics waypoint. Its scale, closed-loop ecology, and manufacturing capability will allow it to operate as a self-sustaining economic engine. The ability to produce more than it consumes is intentional. Visiting spacecraft will be able to offload waste, receive processed commodities, refuel, resupply, and acquire custom-fabricated components. These exchanges will create predictable traffic patterns and establish the station as a focal point for orbital logistics. Subsequent stations will rely on Station 520 for structural modules, life-support commodities, and specialized manufacturing services. The role is analogous to that of early industrial cities that anchored regional economies by supplying essential goods and services. Station 520 will perform the same function in orbit, serving as the first node in a network of infrastructure that will eventually support interstation trade, defense operations, scientific research, and interplanetary missions.

Cluster Formation and Interstation Trade

When Station 520 begins production, it will naturally attract additional stations seeking reliable supply, fabrication services, and ecological support. Orbital clusters will form through economic gravity rather than centralized planning. Stations will appear where production, logistics, and habitation needs intersect, creating dense regions of activity similar to terrestrial industrial districts. The first cluster will form around Station 520 because it will supply the essential goods required for orbital expansion. Research stations, agricultural modules, logistics depots, defense platforms, and specialized manufacturing nodes will locate nearby to minimize transit time and maximize access to FSMS outputs. As each station specializes, interstation trade will increase, strengthening the entire cluster.

Trade flows will follow predictable patterns. Structural modules will move outward from Station 520 to new construction sites. Life-support commodities will circulate among habitation stations. Waste streams will move inward for processing and conversion into fuel, fertilizer, and industrial feedstock. Data, navigation, and timing services will flow across the cluster, supporting operations and defense. Over time, these exchanges will create a resilient economic ecosystem capable of supporting large populations and complex industrial activity. Cluster formation will mark the transition from isolated stations to interconnected economies, enabling specialization, efficiency, and scalability. As clusters grow, they will become staging points for expansion to lunar orbit, Mars transit routes, and eventually the asteroid belt.

Expansion Beyond Earth Orbit

Once an orbital cluster becomes self-sustaining, expansion beyond Earth orbit will be economically viable. The historic limiting factor for deep-space missions has been mass: every kilogram launched from Earth carries a cost penalty that compounds with distance. By producing structural mass, life-support commodities, and fuel precursors in orbit, FSMS will eliminate much of this penalty and enable missions that would otherwise be infeasible.

The first stage is cislunar expansion. Stations positioned at Earth–Moon Lagrange points or in lunar orbit will rely on Station 520 for construction modules, ecological support, and resupply. These stations will specialize in mining, scientific research, logistics, or defense. Their proximity will permit efficient trade and form the first interorbital economic corridor.

The second stage is Mars transit. Large rotating habitats fabricated in orbit will provide artificial gravity, radiation protection, and closed-loop life support for long-duration missions. Instead of launching fully assembled transit vehicles from Earth, FSMS will enable modular construction in orbit, reducing launch mass while increasing mission size and flexibility. Transit vehicles will be refueled, repaired, and upgraded at Station 520 before departure.

The third stage is the asteroid belt. Resource extraction becomes economically viable only when processing and manufacturing occur near the source. FSMS-derived technologies such as large rotating habitats, closed-loop ecology, and modular fabrication will enable industrial operations in deep space. Stations built in orbit will become templates for asteroid-based manufacturing hubs capable of producing metals, volatiles, and industrial feedstock. Expansion beyond Earth orbit will therefore be the natural consequence of establishing a functional orbital economy. Once mass can be produced in space, the solar system will become accessible in a manner that Earth-launched missions alone cannot achieve.

Strategic Implications for the United States

A functional orbital economy will be both an industrial achievement and a strategic asset. Nations that control orbital manufacturing, logistics, and closed-loop ecological systems will shape the future of space commerce, defense, and exploration. Station 520 will provide the United States with the first platform capable of sustaining large-scale orbital operations without continuous Earth resupply, establishing a durable advantage in cislunar space.

Manufacturing in orbit will break the launch-vehicle constraint that currently limits the size and capability of U.S. orbital assets. Large rotating habitats, industrial modules, and defense platforms can be built and maintained without the limitations of Earth’s gravity well. This strengthens national security by enabling resilient infrastructure that cannot be easily disrupted by terrestrial launch bottlenecks or adversary interference. Closed-loop ecological systems will provide strategic endurance: stations that produce food, water, oxygen, and fuel locally can operate indefinitely, supporting long-duration missions, rapid response, and persistent presence in critical orbital regions. They also allow the United States to support allied missions, humanitarian operations, and scientific research without overburdening terrestrial logistics. Interstation trade and cluster formation will create strategic depth. A distributed network of specialized stations will support defense, commerce, and exploration while reducing vulnerability and increasing operational flexibility. The same capabilities extend beyond Earth orbit, enabling construction of Mars transit vehicles, asteroid-belt industrial hubs, and deep-space research stations. By establishing the first functional orbital economy, the United States positions itself to lead the next era of human expansion into the solar system.

The Economic Path to a Solar-System Civilization

The emergence of an orbital economy will mark a fundamental shift in humanity’s relationship with space. For six decades, orbital activity has been constrained by Earth’s gravity well, limited launch mass, and the absence of local production. FSMS will break these constraints by enabling continuous, renewable manufacturing in orbit. With Station 520 the United States could establish the first platform capable of producing structural mass, life-support commodities, and industrial feedstock without reliance on Earth-supplied resources.

This capability will transform orbital stations from isolated outposts into interconnected economic actors. Primary outputs will create the foundation for habitation and construction. Secondary outputs will expand industrial capability and ecological resilience. Tertiary outputs will generate logistics, services, and strategic infrastructure. Together, these layers will form a scalable economic architecture capable of supporting clusters, trade networks, and deep-space missions. Once mass can be produced in orbit, expansion beyond Earth will become economically inevitable. Cislunar stations, Mars transit vehicles, and asteroid-belt industrial hubs will follow naturally from the ability to fabricate large structures and sustain crews without continuous resupply. The solar system will become accessible not primarily through larger rockets but through the emergence of a functional orbital economy.

Station 520 is the first step in this transformation. It will supply the United States with a durable industrial foothold in orbit, generate economic gravity that attracts additional stations, and lay the foundation for a solar-system civilization built on renewable orbital manufacturing. The path forward is clear: build the economy first, and the civilization will follow. Orbital Construction Pioneers is blazing the trail with FSMS.

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National Space Society announces Orbital Space Settlement Design Project

Artist’s impression of the interior of a 500m diameter cylindrical spin-gravity space settlement, whose detailed engineering design is one possible output of the NSS Orbital Space Settlement Design Project. Credits: Bryan Versteeg / Spacehabs.com

In a presentation at this year’s International Space Development Conference, which took place in McLean, Virginia, June 4th through June 7th, National Space Society (NSS) COO/SVP Dale Skran announced the kickoff of an open-source Orbital Space Settlement Design (OSSD) Project. The initiative has been under active development for over a year within the NSS Space Settlement Advocacy Committee (SSAC) and the newly forming NSS Board of Scientific and Technical Advisors (BSTA). Full disclosure: Yours truly is a member of the SSAC. It was officially approved as an NSS Project last March. The content of this post is based on Skran’s presentation, supplemented with subsequent material presented to the SSAC, with permission.

The current OSSD project Study Group core team consists of Dale Skran, Frederick (Rick) Jenet, PhD, and Bryce Meyer, with all BSTA and SSAC members actively involved in review and discussion. Work is currently focused on establishing a foundational set of design inputs in the form of “Questions” (see below). A dedicated workshop to refine these questions will be held at the NSS Space Settlement Summit taking place at the University of Central Florida, October 25th and 26th. This will be followed by a public announcement and formal request for comment from the broader community. In addition, the “OSSD Terms of Reference” (TOR) and the design input Questions will be located on a dedicated NSS website. The final recommendations will be published in the NSS Space Settlement Journal.

What are Terms of Reference?
The TOR is a formal document that defines the mandate, scope, responsibilities, boundaries, and working methods of the OSSD project. TORs are recursive — a large project such as this one can be subdivided, with each subdivision having its own TOR. This powerful technique is derived from the International Telecommunications Union (ITU) standards development process.

What is the Objective of the OSSD Project?

The core goal is to produce the first complete buildable engineering design for a rotating space settlement. The project is primarily an engineering and systems-design effort, not a policy activity, although legal and economic aspects are necessarily included because they affect feasibility.

Why Pursue This Project?

Rotating space settlements as envisioned by Gerard K. O’Neill will remain an empty dream until they become buildable realities. To many observers, it has not yet been fully established that such settlements are feasible. A fully realized engineering design will be a huge leap forward in making the case that settlements in free space lie in humanity’s future. The research and development required could also address many important issues back on Earth (e.g., closed-loop systems, resource efficiency, energy production, materials science, and robotics).

Why Should the NSS Lead This Effort?

The NSS is uniquely positioned because it is:

  • Non-partisan.
  • Not aligned with any particular company or region.
  • Interested in broadening access to space for all of humanity.
  • Possesses the necessary contacts to convene such a project.
  • Has the longevity and reputation to be taken seriously.
  • Can serve as a respected “honest broker” between different companies, products, technologies, and design approaches.
  • Operates as a non-profit.

Why Now?

Several converging factors make 2026 the right moment:

  • It is over 50 years since the landmark 1975 NASA-Ames space settlement summer study and since the founding of the L5 Society, which later merged with the National Space Institute in 1987 to form the NSS.
  • The NSS laid critical groundwork with the invitation-only Space Settlement 2021 Workshop (SSW), resulting in the book “A Dream Renewed: O’Neill’s Vision in the 21st Century,” a paperback/magazine provided to NSS members, ISDC attendees, and coming out in hardcover on August 25, 2026, available for pre-order.
  • Sufficient knowledge has accumulated, and technology has improved over five decades, such that O’Neill’s original concepts can be updated to a buildable design.
  • Low-cost, fully reusable launch vehicles — which existed only on paper in 1975 — are now a reality on the launch pad.
  • The open-source movement has demonstrated a path to the democratization of technology that was not envisioned in O’Neill’s era.
  • Increasingly powerful artificial intelligence tools now enable a relatively small science and engineering team to address large, complex design questions at a level impossible during O’Neill’s time.

Scope and Boundaries of the OSSD Project

Scope of the Engineering Design:

  • A place where people, including families, can safely live on a permanent, economically self-sustaining basis.
  • Nominal population target: 1,000, with analysis covering populations from 100 to 10,000 for comparison.
  • Designed for direct comparison to the 10,000-person NASA Ames summer study and the British Interplanetary Society (BIS) Avalon project.
  • Positioned as a component in a cislunar economic network (not required to be autarkic or totally biologically self-sufficient).
  • Assumes the baseline human species; human modification or enhancement is explicitly out of scope.
  • Design target: 1 gravity or a high fraction of 1g (since humans have evolved over millions of years on Earth, and the minimum gravity level for long-term human thriving in space has not been firmly established).

What’s included:

  • Engineering design for a rotating space settlement.
  • Examination and development of assumptions related to available construction materials and their costs.
  • Exploration of the legal, treaty, and economic prerequisites needed for the engineering design to be feasible.
  • Investigation of resilience to both natural and artificial assaults, with particular attention to electromagnetic hazards, biological threats, and meteor/space debris strikes.

What’s excluded (The idea being “Don’t boil the ocean”; i.e., focus only on the space settlement design, not all the other ancillary infrastructure and supply chains):

  • Lunar mass drivers
  • Lunar mining technology
  • Construction shacks
  • Asteroid mining technology
  • Launch vehicles
  • In-space transport vehicles
  • Detailed design of robotic construction equipment
  • Weapons systems for settlement defense that are not necessary to protect against natural phenomena
  • Military plans relating to settlement defense

What Happens Next? The Five-Year Roadmap

The project will proceed through disciplined, question-driven workshops rather than attempting to design everything at once:

  • NSS, led by the BSTA, will organize high level workshops to define specific design input questions, to be drafted at this fall’s Space Settlement Summit and subsequently flowed down to subordinate working groups.
  • The questions will be categorized into a few topic areas to help assign subject matter experts, such as High-level Requirements, Agriculture/Biological, and Physical/Construction.
  • The BSTA will assign Rapporteurs to lead these working groups in each question area.

NOTE: Each Rapporteur is expected to organize their work as they see fit and report at least annually to the BSTA with a readout of their progress, including draft recommendations. The normal working method will be workshops, but other means can be used. Unlike the ITU-T, which rotates its meetings across continents, workshops will typically be held in the USA, although this is not strictly required. Rapporteurs are unpaid volunteers, typically with jobs in the space industry

  • In a workshop, carefully framed draft questions will be presented and tagged with a dependency (i.e., TOR, Economic Model, Location, etc.) The questions form the intellectual backbone driving the entire OSSD project.
  • The workshop groups will do the hard work to define good questions with the core philosophy that “Good questions drive good answers.”
  • Workshops will cover a focused set of questions and continue until a Recommendation is produced to define a design output.
  • Target: After five years, the accumulated Recommendations will add up to a complete, buildable engineering design.

The Questions:

The following list is an evolving work in progress as of the date of this post, of potential questions to be finalized by the BSTA and then flowed down to the working groups to flesh out the details. It is by no means complete.

  1. What is the target reliability/safety standard? (Depends on TOR)
    Options range from aviation-like to nuclear-plant-like, to “ISS-like”. Telecom, chip, or automotive standards? This decision drives redundancy, inspection cadence, acceptable risk to children, and the critical safety-vs-uptime trade-off (space habitats cannot have downtime). It also requires choosing a reliability level target (e.g., 5-sigma vs. 6-sigma) and deciding which parts of the habitat are held to which standards.
  2. What are the core services provided to residents? (Depends on TOR – for discussion)
    Includes housing space per person, privacy, recreation, food variety, internet latency, and governance/rights baseline. The question invites comparison to services provided by a small town on Earth and asks how to avoid the tragedy of the commons for “free goods,” while also defining the proper limits of what planners/designers should dictate.
  3. What is the Economic Model? (Depends on Q4)
    This involves answering fundamental questions like: How will settlers add economic value? How will the settlement be economically sustainable?
  4. Where exactly in cislunar space will the settlement be located? (Depends on TOR)
    Candidate locations: Near-Rectilinear Halo Orbit (NRHO), distant retrograde orbit, Earth-Moon Lagrange (EML)1/EML2 halo, high lunar orbit, or EML4/EML5. Location dramatically affects eclipses, station-keeping, communications, debris environment, thermal design, and the economic model itself.
  5. What is the logistics doctrine with Earth? (Depends on Q3, Q4)
    Covers cadence for spares and consumables, allowed lead times, acceptable downtime, and precisely which items must be “topped off” and how often. Items such as trace elements, pharmaceuticals, replacement electronics, specialty foods, nitrogen/argon, etc. need to be defined. Spares/consumables strategy may itself be an outcome of the economic model rather than a question per se.
  6. What population size and target demographics are required for social stability? (No dependency)
    Includes sex ratio, age distribution, and other demographic factors. Questions about non-cisgender humans are out of scope. This is not to exclude them explicitly, but the intent of the question is to focus on critical biological issues.
  7. What population size is required for operational stability? (No dependency)
    Focuses on skill sets, trades, and degree of automation needed for settlers to maintain safe operations. May depend on downstream recommendations about agriculture and other operations.
  8. What population size is required for economic viability? (Depends on Economic Model)
    Considers export/service revenue versus internal labor needs, degree of specialization, downtime tolerance, training pipeline, and explicitly excludes a small population of the very rich as a viable model.
  9. What population size, including pets, is required for mental health? (No dependency)
    Studies have found that 1 in 20 people who overwinter in Antarctica develop serious mental health issues. This suggests that a population of ~200 (typical Antarctic winter-over size) may be too small, or that aspects of the Antarctic station model need correction for space application.
  10. Therefore, what is the minimum viable steady-state population? (Depends on the Q6, Q7, Q8, Q9)
    A synthesizing question that derives a minimum that satisfies the criteria from the related questions, with a suggested floor of 100 occupants.
  11. What governance model applies? (Depends on TOR)
    The TOR states that the settlement is assumed to be under the legal jurisdiction of the launching state. The question explores issues arising from applying the laws of the launching state to the settlement and how those issues can be resolved.
  12. What Ownership Model Applies? (Depends on Economic Model)
    This question is strongly linked to the economic purpose of the settlement, and should cover corporate ownership/company townships, co-ops, condominiums, employee-owned corporations, and other models.
  13. What international legal regime is required to allow the first settlement to be funded? (Depends on TOR)
    Focuses on what legal interpretation of the Outer Space Treaty is necessary to permit construction of a settlement in orbital space.
  14. What maximum rotation rate (rpm) is acceptable for a multi-generation population? (Depends on TOR)
    Because artificial gravity is fixed at approximately 1g, the rotation rate directly sets the required radius, which in turn drives structural mass and construction approach. Why 1g? The TOR states: “Since the minimum gravity level for human thriving has yet to be firmly established, the design target will be either 1 gravity or a high fraction of 1 gravity…” I’ve posted on the topic previously.
  15. What radius/geometry follows from the g level and rpm? (Depends on Radius, also TBD)
    Explores torus vs. cylinder vs. multi-ring vs. hammerhead configurations, habitable deck layout, and zoning.
  16. What is the docking/visiting vehicle strategy relative to rotation? (Depends on Q15)
    Will there be total spin-down? Will there be a non-rotating hub, and if so, how will the transfer from rotating-to-nonrotating spaces be accomplished?
  17. What radiation standard do we design to for families/children? (Depends on Q1)
    Annual dose targets, pregnancy limits, and Solar Particle Event shelter requirements need to be specified. Note that Medevac doesn’t help for chronic exposure to Galactic Cosmic Radiation.
  18. What shielding approach meets Q17 at minimum mass/cost? (Depends on Q17, Q4)
    Decisions on how bulk shielding (e.g. water and/or regolith) will be distributed, need to be made, accounting for storm shelters. Shielding-as-storage, active shields, and layered shields should be considered.
  19. Where does shielding mass come from? (Depends on Q4, Q18)
    Weigh the options of Earth-launched vs lunar-derived vs extracted from an asteroid, keeping in mind that sourcing material for initial habitats may change for future growth.
  20. What closure level is required to be “permanent” with imports allowed? (Depends on Q2, Q3, Q4, Q5)
    Define which consumables must be recycled (e.g., water, oxygen, nitrogen) vs what can be imported.
  21. What food system meets nutrition, variety, and psychological considerations at minimum mass/power? (Depends on Q10, Q20, Q25)
    The hydroponics/vertical farming mix, lighting strategy, protein plan, and storage buffers all need to be determined, fully considering the recycling system and ecological balance of the biosphere.
  22. What will be the atmosphere model and fire safety regime? (Depends on Q1, TOR)
    The total pressure, O₂ fraction, diluents (N₂/Ar), toxic pollutants control, and fire suppression doctrine all need to be determined.
  23. What water/waste architecture achieves Q20 with acceptable failure modes? (Depends on Q1, Q2, Q20)
    Water recovery, sanitation, pathogen control, waste processing, and a plan for “what if” contingencies need to be defined.
  24. How can an overly clean habitat environment be avoided? (TBD)
    Children who grow up on farms have very low allergy rates; we want to make sure kids in the settlement are exposed to diseases to develop their immune systems.
  25. What total power level is required (steady state and peak)? (Depends on Q1, Q3, Q21, Q23)
    This will be a cumulative summing the contributions from the habitat, agriculture, industry, propulsion, and reserves.
  26. What power source architecture is optimal in cislunar space?(Depends on Q4, Q25)
    Solar vs nuclear vs hybrid, taking into account storage needs, safety considerations, and maintenance.
  27. What thermal rejection system is required? (Depends on Q25, TBD)
    This will drive radiator design, cooling system loops, heat reuse, zoning, and orientation constraints.
  28. What minimum local manufacturing/repair capability is required? (Depends on Q5, Q9)
    Operations to consider include, but are not limited to, planning for spare parts, maintenance of seals/filters, facilities for machining, electronics repair, additive manufacturing, and QA.
  29. What structural concept meets loading requirements, while taking into account micrometeoroids, internal pressure, and rotation rate, and minimizing mass? (Depends on Q4, Q15, Q18, Q22)
    At a minimum, requires consideration of materials, compartmentalization approach, Whipple shielding design, and pressure hull segmentation.
  30. What is the assembly and spin-up strategy? (Depends on Q4, Q15, Q18, Q29)
    Requires decisions on which modules are preassembled vs built on-orbit. Will the construction be carried out robotically or by crew? What is the optimal timing of when shielding is added, taking into account how balance will be maintained when rotation is initiated?
  31. What is the fault-tolerant operations concept? (Depends on Q1, Q10, Q28)
    This will help determine the staffing requirements, levels of training, emergency response procedures, maintenance cycles, inspection needs, spares policy, and cross-training.
  32. What are the top “design basis accidents” and how are they handled? (Depends on Q1, Q22, Q23, Q29, Q31)
    Scenarios include, but are not limited to, fire, depressurization, toxic release, collision, loss of rotation control, and loss of power.
  33. What is the growth path from the minimum viable system to a larger one? (Depends on Q15, Q18, Q29, Q30)
    This question will help to decide when to add rings/modules, how governance and economy scale, and how to avoid redesign.

O’Neill’s Vision of Free Space Settlements is Closer Than Ever

The OSSD project is a major strategic step for the NSS. After completing and publishing the foundational 2021 workshop proceedings in both accessible paperback and soon-to-be-released premium hardback formats, the organization is now moving from vision and discussion to disciplined, engineering-driven action. By framing the project around a rigorous, design input question methodology with clear scope boundaries, plans to assign rapporteurs, workshop processes, and a five-year horizon for producing buildable recommendations, the NSS is taking the lead as the honest broker and convening authority capable of coordinating the complex, multi-disciplinary work required to turn O’Neill’s dream of rotating space settlements into engineering reality.

The interactive workshop approach using carefully crafted design questions demonstrates a commitment to grassroots community input and iterative refinement rather than a top-down prescription. The careful separation of in-scope engineering/systems issues from excluded topics (launch vehicles, mining technology, mass drivers, etc.) shows a mature project management philosophy designed to keep the effort focused and achievable.

In summary, the OSSD Project will bridge the inspirational legacy of Gerard K. O’Neill and the 1975 NASA-Ames study with the practical realities of 2026: reduced launch costs via reusable rockets, open-source methodology, powerful leverage of AI, accumulated knowledge, and an organized NSS ready to lead the next phase of space settlement engineering. This initiative is positioned as the logical next step after the SSW book — turning the “long list of areas for future research” identified in that publication into concrete, actionable engineering questions whose answers will collectively constitute the first credible, buildable design for a rotating space settlement.

I cohosted The Space Show with Dr. David Livingston on August 7 when Dale Skran was our guest, sharing more details about the project. You can watch the archived Zoom recording of the show on The Space Show Substack page or listen to an audio recording on The Space Show website. Visit the NSS OSSD project website for the latest updates. Let’s make this happen!

Artist’s rendering of what the interior of a 125m diameter rotating space settlement might look like; another possible outcome from the NSS OSSD project. Credits: Bryan Versteeg / Spacehabs.com
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3D printing Mars habitats using in-situ resources

Conceptual illustration of a habitat on Mars being 3D printed with a regolith-based mixture using a direct ink writing technique. The configuration is inspired by the MARSHA habitat concept proposed by SpaceFactory. Credit: Marcelo Tramontin Souza, Figure 1 from open access article in Acta Astronautica with minor text edits / Used under CC by 4.0

Imagine trying to build a house on Mars. All the materials you need would have to be imported from Earth on a rocket that costs tens of thousands of dollars per kilogram to launch. Aerospace engineers and advocates for space settlement know that in-situ resource utilization (ISRU)—using materials already on Mars instead of shipping everything from home – is the key to sustainable and affordable settlement of Mars (and elsewhere in the solar system, for that matter). A review paper by Brazilian researcher Marcelo Tramontin Souza in the forthcoming issue of the journal Acta Astronautica, pulls together the latest research on one of the most promising ways to do this: 3D printing (additive manufacturing) habitats directly from Martian regolith. This post explains the paper’s main ideas, why they matter, the biggest challenges, and what the future might look like.

Why Mars Habitats Would Benefit from 3D Printing Using Local Materials

Sending humans to Mars is currently incredibly expensive. One early estimate puts the cost of the first crewed mission at around $500 billion, with most of that money going toward hardware, launch, and operations. This estimate has the caveat that it was made prior to SpaceX significantly reducing launch costs through the company’s continuous optimization of the reusability of its Falcon 9 launch vehicle and the anticipated $100M/ton delivered to the Martian surface with Starship. Even if the cost may be quite a bit lower, it will still be cost-prohibitive to bring everything from Earth.

The biggest single issue is, of course, Mass. Every kilogram of building material launched from Earth adds huge costs in rocket fuel. Once on Mars, astronauts will need safe places to live that protect them from the planet’s deadly environment: a paper-thin carbon-dioxide atmosphere (only about 0.6% of Earth’s pressure), average temperatures of –60 °C with swings up to 100 °C in a single day, no magnetic field to block cosmic radiation, toxic perchlorate salts in the soil, and dust storms that can last for months.

Traditional ideas—shipping pre-built modules and assembling them on the surface—still require launching tons of material. ISRU flips the script by mining and processing local resources on site. Souza’s paper focuses on additive manufacturing, or 3D printing, because it can be automated easily, wastes almost no material, and can create complex shapes layer by layer from digital designs. In this scenario, robots would excavate regolith, mix it into printable “ink,” and build protective shells around inflatable living quarters. This approach could let early outposts grow into self-sustaining colonies without constant resupply from Earth.

The paper reviews three main categories of 3D-printing technologies adapted for Mars: low-temperature extrusion (like giant concrete printers), medium-temperature thermoplastic (sulfur-based “Martian concrete”), and high-temperature sintering (melting or fusing regolith with solar, microwave, or laser heat). It also covers habitat designs, radiation shielding, structural engineering under Mars conditions, energy needs, and remaining technology gaps.

What Martian Regolith Is Really Like—and Why It’s Both Useful and Tricky

The loose, dusty regolith on Mars formed from billions of years of meteorite impacts, wind erosion, and limited chemical weathering of the planet’s basaltic crust. Chemically, it is roughly 40–50% silica (SiO₂), 10–15% aluminum oxide, 10–20% iron oxides, plus magnesium, calcium, sulfur, and traces of other elements—very similar to Earth basalt but with more variability from site to site. Grain sizes are mostly silt to fine sand, which helps flow in printers but can clump in low gravity. About 25–60% of it is amorphous (non-crystalline) material, which is great for chemical reactions but unpredictable.

Key challenges include:

  • Perchlorates (0.5–1% by weight) are toxic to humans and plants and can interfere with binders.
  • Low pressure (~600 Pa) makes water boil or freeze instantly, so water-based materials are hard to use on the open surface.
  • Temperature swings cause cracking from repeated expansion and contraction.
  • Radiation: Surface dose is ~200–250 mSv per year—far above Earth’s safe limits. Regolith is a good shield, but you need about 1–3 meters of it to cut exposure dramatically.
  • Dust and wind: Fine particles stick to everything and abrade surfaces.

The paper provides a summary of regolith properties: bulk density 1.1–1.6 g/cm³, solid density ~3 g/cm³, angular particles for good interlocking and low thermal conductivity when gathered in loose piles (good for insulation).

To model Martian soil with these characteristics, regolith simulants like JSC Mars-1A, MGS-1, and HIT-MRS-1 are used on Earth to test ISRU scenarios because they match these properties with respect to chemistry and grain size.

The Three Main 3D Printing Approaches for Mars Construction

Souza organizes the technologies by temperature and binder needs. Each has strengths for different mission phases.

1. Extrusion-Based Printing (Low-Temperature, ~20–80 °C curing) – The Most Mature Option
This is like the giant concrete printers already used on Earth for houses. A robotic arm or gantry extrudes a thick paste of regolith mixed with a geopolymer binder (alkali-activated, similar to ancient Roman concrete but made from local minerals). Studies like one of the references in the paper by Ma et al. (2022) mixed HIT-MRS-1 simulant with sodium silicate and NaOH, then added basalt fibers for toughness. They printed bio-inspired shapes—honeycomb, helical, suture-like patterns—that turn brittle material into damage-tolerant structures achieving up to 32 MPa compressive strength.

The major problems on Mars for this method include:

  • Needs water and imported alkaline chemicals (hard to make locally at scale).
  • Curing fails in vacuum and cold: water evaporates or freezes, creating weak, porous parts.
  • Solution: Print inside a pressurized, heated inflatable enclosure (like the MARSHA concept from AI SpaceFactory) and use localized heaters or microwaves to speed curing.

Pros: Scalable for large structures, proven on Earth analogs like NASA’s Mars Dune Alpha (ICON’s 3D printed habitat).
Cons: High Earth-dependence early on; slow curing (hours to days).

2. Thermoplastic Extrusion – Sulfur “Martian Concrete” (120–150 °C)
Sulfur is abundant on Mars in sulfates. It can be melted, mixed with ~50% regolith, extruded or casted, and it will harden in minutes as it cools—no water needed. Wan et al. (2016) and Giwa et al. (2024) showed compressive strengths of 35–60 MPa, with additives like dicyclopentadiene (DCPD) improving flexibility and reducing sublimation in vacuum

Advantages: Fully ISRU-compatible once sulfur is extracted, can be processed quickly, is recyclable by remelting, and works in a vacuum. Domes and blocks are easy to print or cast.
Drawbacks: Brittle at low temperatures; may crack during thermal cycles of Martian days, which can have temperature swings of up to 100 °C; sulfur can sublimate (turn directly from solid to gas) if hot. Long-term durability under repeated freeze-thaw cycles is poor without modifiers.

3. Binder-Free Sintering (High-Temperature, >1000 °C) – Solar, Microwave, or Laser
Heat regolith until particles fuse like pottery or glass. No imported binders—just pure local dirt.

  • Solar sintering: Concentrate sunlight with lenses or mirrors. Mars gets less sunlight than Earth (~590 W/m² at the top of the atmosphere vs. 1361 W/m²), but the thin atmosphere means almost no convective cooling, so efficiency is surprisingly good. A study by Deng et al. (2025) showed basaltic regolith sinters well with optimized particle size. Layer-by-layer printing could build graded structures (dense outside for strength, porous inside for insulation).
  • Microwave sintering: Iron-rich regolith absorbs microwaves volumetrically (heats from inside out). Fast but hard to control; risks cracking from uneven heating.
  • Laser sintering: Great for small, precise parts (tools, brackets) inside a habitat, but too slow and energy-hungry for full-size buildings.

These methods depend fully on ISRU but are energy-intensive (10–100 MJ per kg vs. ~1–2 MJ/kg for extrusion) and sensitive to dust on optics or variations in regolith chemistry.

Robotic systems (rovers for excavation, gantry arms for printing, sensors for real-time monitoring) and energy sources (solar + nuclear backup) are critical across all methods.

Habitat Designs: From Inflatable Cores to Printed Shells

Early habitats will likely be hybrid: lightweight inflatable modules flown from Earth, then covered by 3D printed or piled regolith for protection. Inflatable pressure vessels handle internal Earth-like air pressure (~50–100 kPa). Regolith overburden (1–3 m thick) blocks radiation, insulates against temperature swings, and stops micrometeorites and dust.

  • Loose regolith burial: Fast and cheap but risks settling, dust infiltration, and uneven loading.
  • Consolidated regolith shells: 3D print a rigid outer layer first, then pile loose dirt on top. This distributes loads, stops dust migration, and allows graded porosity for better shielding.
  • Fully printed or subsurface options: Lava tubes or excavated trenches offer natural shielding; printed domes or cylinders provide long-term durability.

Radiation modeling (using GEANT4 simulations) shows that a one-meter layer of regolith cuts the dose by ~70%; 3 meters brings the exposure down near Earth background levels. Thermal buffering from regolith also reduces heating/cooling needs.

Structural Challenges Under Martian Conditions

Mars is not Earth (obviously):

  • Internal pressure: The habitat must hold ~1 atm inside against near-vacuum outside. Printed layers must be airtight (often needing internal liners).
  • Low gravity (0.38g): Implies less structural loads but also less compaction during printing; soil bearing capacity changes may arise.
  • Marsquakes: The InSight Lander, which sent its last transmission December 15, 2022 after a successful four-year mission, recorded hundreds of small events (magnitude ~1–4). They last minutes with low damping, so long vibrations could fatigue structures, but they are too weak to cause collapse.
  • Thermal cycling and dust abrasion: Printed layer interfaces are weak points.

Habitat designers must use finite-element modeling, taking into account the above environmental factors, consider interactions between the soil and structure, and build in redundancy. To the authors’ knowledge, no studies have yet performed integrated simulations combining all these factors, which is a major research gap.

Energy, Scalability, and Real-World Trade-Offs

Energy is the hidden killer. Extrusion is relatively inexpensive with respect to power needs, but requires imported binders. Sintering uses only local materials but demands 10–100 times more energy per kilogram. Early missions will favor low-energy extrusion inside enclosures, while later ones can go fully solar-sintered. Robots must work autonomously for years in dust and cold—this is still a significant engineering hurdle.

In comparing the main Martian habitat design approaches, Souza summarizes their advantages, limitations, and associated trade-offs in terms of construction complexity, radiation protection, structural performance, and operational feasibility. Loose burial will be the fastest for initial crews; hybrid printed shells offer the best long-term balance; full subsurface or printed habitats are the ultimate goal, but need mature ISRU technologies.

Prospects, Gaps, and the Road Ahead

Souza is optimistic but realistic. 3D printing combined with ISRU is the most promising path to sustainable Mars habitats because it significantly reduces launch mass and enables rapid expansion. Near-term wins could come from sulfur concrete for quick protective barriers and geopolymer printing inside controlled environments. In the long term, binder-free sintered regolith has the potential to create entire self-repairing cities.

Conceptual illustration of an autonomous 3D printing system constructing a Martian shelter using sulfur-based concrete, deposited layer by layer from locally sourced materials. Credit: Marcelo Tramontin Souza, Figure 3 from open access article in Acta Astronautica with minor text edits / Used under CC by 4.0

The key remaining challenges include:

  • Making binders 100% from Mars resources.
  • Proving long-term durability (thermal cycling, radiation protection, perchlorate mitigation).
  • Scaling robots and energy systems.
  • Sealing printed structures for pressurization.
  • Integrating life support, greenhouses, and expansion.

The paper calls for more analog testing on Earth (e.g., in deserts and vacuum chambers), international collaboration, and hybrid approaches that combine the best of each method. Dual-use benefits for Earth include better disaster-resistant 3D printed buildings in remote areas.

In the end, Souza’s review shows that Mars habitats won’t arrive fully formed, delivered from Earth on rockets. They will be grown, layer by layer, from the Red Planet’s own dirt—made robust and resilient by smart engineering, powered by the Sun and nuclear energy, and built by tireless robots. This technology will enable humans to live on the Red Planet permanently and, one day, turn humanity into a true multi-planetary species. The next decade of research will decide how quickly that vision becomes reality.

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Homing in on the Gravity Prescription

Image of the JAXA Kibo module on the International Space Station which houses the MARS short arm centrifuge for artificial gravity studies. Credit: NASA/JAXA

The Gravity Prescription (GRx), a term first coined by Dr. Jim Logan, refers to the minimum “dosing” of gravity (level and duration of exposure) to enable healthy conception, gestation, birth and normal, viable development to and throughout adulthood as a human being…over multiple generations. It should be noted that the GRx can be broken down into at least three components: the levels needed for healthy pregnancy (conception through birth), early child development, and adulthood.

The Japan Aerospace Exploration Agency (JAXA) has been studying the adult gravity prescription for mitigation of mammalian physiological issues that arise in space due to microgravity using mice for about a decade. To conduct this research, they’ve been using the Multiple Artificial-gravity Research System (MARS) short arm centrifuge in the Kibo module on the International Space Station (ISS). This will help us understand what dosing level of gravity is required to prevent the myriad of health issues (e.g., serious reduction in bone and muscle mass, ocular changes, weakening of the immune system – there are many more) that arise in mature adults when exposed for long periods to microgravity, to inform countermeasures for long-duration spaceflight and settlement.

By way of background, I reported back in 2021 on JAXA’s first long-term mouse study comparing mice reared under microgravity conditions to a cohort raised under 1g artificial gravity in the MARS centrifuge, which found that Earth-normal artificial gravity appears to prevent the negative health effects of microgravity. In the same post, I provided an update upon publication of the results of a second experiment executed a couple of years later, which tested mice in Moon gravity and found that 1/6g prevents muscle atrophy in mice, with the downside that this level of artificial gravity cannot prevent changes in muscle fiber (myofiber) and gene modification induced by microgravity. There appeared to be a threshold between 1/6g and Earth-normal gravity, yet to be determined, for skeletal muscle adaptation. Then in 2023 we got a few more data points helping us zero in on the right dose, at least for the adult GRx, between Moon and Earth levels of gravity.

I mentioned this new preliminary data in my presentation at ISDC 2024 on how the GRx may impact the future of space settlement. The results came from a NASA-funded experiment in cooperation with JAXA, headed by Dr. Mary Bouxsein and collaborators, that studied adult mice launched to the ISS on SpaceX CRS-27. The mice were split into four groups and dosed in the MARS centrifuge at four levels of gravity (microgravity, 0.33g, 0.67g, and 1g). The results were presented at the American Society for Gravitational and Space Research (November 2023). Still, no formal paper had been published at that time, only an abstract from the conference talk. Preliminary results showed that hindquarter muscle strength increased commensurate with the level of artificial gravity, indicating that spaceflight-induced atrophy can be mitigated with artificial gravity – more is better. Now the full study has finally been published in Scientific Advances with further details.

After each of the cohorts were individually treated to the four gravity levels in the MARS centrifuge and returned to Earth, the mice were euthanized and the researchers examined their soleus muscle (the calf muscle which is very sensitive to gravity levels), along with strength tests and blood biomarkers.

Key findings included:

  • Muscle shrinkage (atrophy): In microgravity, the soleus muscle fibers shrank noticeably. At 0.33g, the muscle cross-sectional area was largely preserved—meaning it didn’t lose much mass. Higher gravity (0.67g and 1g) also protected muscle size.
  • Muscle fiber type: Muscles have different fiber types—slow-twitch (good for endurance) and fast-twitch. Microgravity causes slow fibers to switch to fast ones. 0.33g partially prevented this switch, but 0.67g fully stopped it, keeping the muscle composition closer to normal.
  • Muscle function: Strength tests (like grip strength) and electrical measurements showed that 0.67g was enough to maintain overall muscle performance. Lower gravity levels did not fully protect function.

The study also found 11 blood metabolites (small molecules that are intermediate or end products of metabolism) that changed depending on gravity level. These could serve as future biomarkers to monitor astronauts’ health without invasive tests.

Why does this matter? This is the first experiment to identify the adult GRx thresholds for muscle health. It suggests that 0.33g (close to Mars-level) helps prevent muscle weakening, but titrating to 0.67g is needed to fully maintain strength and normal muscle condition. For future space stations or vehicles with rotating sections to create artificial gravity, this information is valuable: partial gravity helps, but at least 0.67g is better for long-term missions. Crucially, these results could inform the spin-rate specifications for a Mars Cycler to generate artificial gravity to maintain muscular function for travelers to and from Mars.

In short, the paper shows that even moderate artificial gravity could mitigate the musculoskeletal problems astronauts face in space, helping keep crews healthier on deep-space journeys. The research used careful controls, multiple measurement methods, and advanced analysis to reach these clear conclusions.

The bigger question is what is the GRx for reproduction? If permanent settlements are to be established in space, they should be (in the long run) at destinations that enable biological self-sustainability, meaning we will want to have healthy children and raise families there as we expand out into the solar system.

One study conducted by Japanese researchers in 2019 aboard the ISS suggested that mouse embryonic growth may be possible in microgravity. But this experiment was only 4 days of embryo development, which took place after conception. Another study of pregnant mice from the shuttle era found serious issues with brain development after exposure to microgravity. These are just snapshots of embryo and later fetus development, and only in microgravity. There still have not been rigorous scientific experiments covering the full mammalian reproductive cycle through all its phases under variable gravity conditions mimicking the Moon, Mars, or higher levels below that of our home planet.

Conceptual AI generated image of an expectant mother in Earth orbit under appropriate GRx dosing conditions after mammalian reproduction has been validated via higher animal models through all stages of pregnancy for a safe level of artificial gravity. An appropriate level of radiation shielding would also be required and is not shown in this illustration. Credit: MS Designer

It is vitally important as the private space stations begin to replace the ISS and space tourism takes off (including maybe even hotels on the Moon), that we understand the risks and implications for having babies off Earth in lower gravity environments. Alex Layendecker, the founder of the nonprofit Advanced SpaceLife Research Institute (ASRI), told me the following in an interview about his Green Paper on Sex in Space: Consideration of uncontrolled human conception in emerging space tourism:

“With mass access to space, we’ll soon have groups of individuals going up solely for vacation/leisure purposes, and you can be assured some of them will be engaging in sexual activity.  While it would be absurd to try to implement or enforce laws preventing sexual activity in those environments, the dangers associated with potential conception still exist.  What is critically needed at this point is a better collective understanding of those dangers, their mitigation, and for space companies to be able to provide those paying customers with enough information that informed consent can be established – space is inherently dangerous already, and people launching into space are briefed on that.”

Besides JAXA and some limited research by NASA, there are just a couple of organizations dedicated to studying the GRx for reproduction. ASRI based at Cape Canaveral and a Dutch company called SpaceBorn United. SpaceBorn has space missions planned in the next few years using their ARTIS (Assisted Reproductive Technology in Space) platform, focused on mammalian conception and early embryo development, with a prototype “space-embryo-incubator” capable of treating samples with adjustable artificial gravity. Initial missions will send this device to space with male and female mouse gametes, where in vitro conception and 5-6 day embryo development will proceed under artificial gravity conditions. The embryos will then be cryogenically frozen and returned to Earth where, if approved, they will be implanted in natural wombs, where the pregnancy will progress on Earth. If successful, subsequent phases over the next couple of decades will focus on increasing stages of pregnancy in space and early embryo development on the Moon.

But SpaceBorn’s platform is a small, automated self-contained centrifugal device operated in microgravity. To really study the GRx for mammalian reproduction, a fully equipped (preferably crewed) variable gravity biolab large enough to rear lower organisms from conception through pregnancy to birth, maturing into adulthood – over multiple generations and progressing successively in higher mammals – would be required. A very tall order! But there are reasonable and well-thought-out concepts for such facilities I’ve explored here previously.

Currently, there are only a couple of companies with rotating space stations in their strategic plans to provide larger-scale artificial gravity laboratories that could be used for reproductive studies. Vast Inc., a well funded, privately held startup, explicitly lists an Artificial Gravity Station targeted for around 2035 in its official product roadmap, a long cylindrical design that will rotate end-over-end at ~3.5 RPM to create artificial gravity for long-term habitation. It would build on their modular (non-rotating) Haven-1 module currently planned for launch in 2027 and the follow-on Haven-2 station which would gradually add units, eventually leading to a 9-module configuration slated for 2032.

Conceptual illustration of Vast Space Haven-2 nine module configuration space station that could be placed in Earth orbit as soon as 2032. Credit: Vast Space

Above Space, with aspirations for rotating wheel type space stations in the 2030s, has significant engineering and funding hurdles, but is the only other player that has plans for variable gravity facilities in space.

In my presentation at ISDC2024 linked earlier in this post, I advocated for determining the GRx for reproduction sooner rather than later, especially given Elon Musk’s timelines for colonizing Mars. As Musk has made clear for years and with his recently revealed SpaceX compensation package tied to it, his vision for the company is to make humanity multiplanetary and build a city on Mars with a million people. Up until recently, he was projecting mid-century to achieve that milestone. His shifting focus from Mars to the Moon aside, does he expect the population of his Martian colony to be composed of just adults? Musk, who has warned of population collapse and low fertility rates here on Earth as one of humanity’s biggest challenges, has been quoted as saying, “People are going to have to revive the idea of having children as a kind of social duty. If you can, and are so inclined, you should. Otherwise civilization will just die.”

Image of Elon Musk holding his son X AE X-II after Grimes gave birth to him in May 2020. Credit: Elon Musk

I’m pretty sure he envisions that the people occupying his city on Mars will want to have children there. And he’d probably want to know the GRx for reproduction well before significant numbers of people began migrating there to stay. A variable gravity research facility in low Earth orbit dedicated to studying mammalian physiology, including reproduction in less than 1g, could be built using SpaceX hardware and would not cost much more than Musk’s pocket change, but I’ve seen no indication that this is a priority for him.

Of course, there are others, affectionately called O’Neillians, who say we know 1g works, so let’s not waste time and just get started building rotating space settlements like Kalpana One, a 500m diameter starter unit located in equatorial low Earth orbit. Shielded by Earth’s magnetic field and therefore requiring less mass for radiation shielding, it would be much easier to accomplish than the enormous miles-long settlements O’Neill envisioned to be placed out at Earth-Moon Lagrange Point L5. The attractiveness of this approach (in LEO) may be waning with the rise of AI and what will likely be a proliferation of orbital data centers in the next few years. Cowboy Space has just filed with the FCC for a literal Stampede of 20,000 satellites adding to the queue of companies seeking regulatory approval for their megaconstellations, including Blue Origin’s Project Sunrise (51,600), Starcloud (88,000), and SpaceX’s 1 million satellites, all in sun-synchronous orbits ranging from 500 to 2000 kilometers. It may be getting pretty crowded up there soon, increasing the risk of collision with large cross-section space stations that are not easily maneuvered out of the way.

Personally, my view has evolved on the urgency for determining the GRx for reproduction on the Moon or Mars. I still hold that healthy human reproduction in lower-gravity environments is highly uncertain, given millions of years of evolution in Earth’s gravity, and carries a substantial risk of complications at every stage of reproduction. Being inspired by O’Neill, I was admittedly biased toward his approach to mitigate these risks and had a preference for spacious artificial gravity worlds. This led me to believe that if we confirmed through studies of the GRx for reproduction that having children in less than 1g could lead to dangerous complications and, therefore, be morally wrong, the information might bend the arc of space development toward free space settlements. Knowing we could not have children on the Moon or Mars might start to change the mindset of many space settlement advocates, whom the great science fiction author Isaac Asimov called planetary chauvinists, leading to diversion of resources toward building the infrastructure needed to construct rotating space settlements like Kalpana. I’m old enough to remember that O’Neill invented one of the key technologies for building these huge structures: a mass driver intended to be placed on the Moon to launch massive amounts of lunar regolith into space so that it could be processed into radiation shielding for these colonies. Advances in robotics, in situ resource utilization (ISRU), in-space assembly, life support systems, and many other technologies are needed to enable O’Neill colonies. Many of them are proceeding at pace anyway, but I thought that if we found the GRx for reproduction was not less than 1g, it would put a sense of urgency around these efforts.

However, it looks like market forces may be changing all this. I did not anticipate Elon Musk advocating for mass drivers on the Moon. Though he says they would be used for launching SpaceX’s AI satellites, the infrastructure for ISRU and electromagnetic launchers looks like it may be coming to Luna sooner than we expected and can certainly be retooled to fling regolith into space for shielding rotating space settlements, even larger ones, if the drive (and markets) are there.

But rather than the GRx for reproduction being the determining factor for where we settle space – planetary surfaces or free space colonies – a split life cycle may be the solution. This approach, credited to Kelly and Matt Weinersmith in their book A City on Mars, suggests using both destinations! As clarified in a presentation at ISDC2024 by Dale Skran, Chief Operating Officer & Senior Vice President of the National Space Society, this new way of thinking (not an official position of NSS) acknowledges that we probably need Earth normal gravity for having children and suggests that a rotating space station birthing center be placed in orbit above surface colonies on the Moon or Mars. Couples would conceive, bear children, and raise them in a healthy artificial gravity crèche, allowing them to mature to early adulthood, after which families or individuals may choose to remain in space or relocate to the low-gravity surface communities below.

So research by Dr. Bouxsein et al. may be homing in on the adult GRx, with the results from their study paving the way for practical countermeasures against health issues adult astronauts will face in microgravity on long-duration missions in space. But the artificial gravity dose level for reproduction needs much further study before we can safely say biologically self-sustaining space settlements in less than 1g will be possible. Until then (and after, if the answer is no), split life cycle communities may be the strategy for an expanding population migrating out into the solar system and beyond.

Artist’s impression of the interior of Kalpana One, a cylindrical rotating colony providing Earth normal artificial gravity for healthy living in space. With the coming proliferation of AI orbital data centers later this decade, this approach may lose favor in LEO, but could be one possible in-space component of a split life cycle solution for settlement of the Moon or Mars. Credits: Bryan Versteeg / spacehabs.com

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Extraction of oxygen from lunar regolith using solar pyrolysis

Experimental apparatus of an experiment to characterize solar pyrolysis of lunar regolith simulant, a) Flowchart of the setup with the reactor, solar concentrating system and the various peripheral equipment, b) Picture of the pyrolysis reactor during sample exposure to concentrated solar energy. Note glass reactor clouding due to the deposition of the vaporized materials. Credits: Figure 2 with minor text edits from article by Jack Robinot et al. / Used under CC by 4.0

A team of European researchers have for the first time, quantified oxygen production via solar pyrolysis, a process that uses concentrated sunlight to heat lunar soil to release oxygen as a gas. Jack Robinot and collaborators report their results in Advances in Space Research. The findings of this study mark a significant milestone in space manufacturing technology, providing the first-ever direct experimental quantification of oxygen yield from the thermal decomposition of lunar regolith using focused solar energy.

As space settlement advocates are aware, the primary bottleneck for long-term human habitation on the Moon and elsewhere in the solar system is the logistical challenge of resupply of resources from Earth. They know that In-Situ Resource Utilization (ISRU) is the key to long term sustainability by harvesting and processing local materials into valuable resources like oxygen, water, and metals.

Oxygen is obviously of particular importance, not only because it’s needed for human life support, but also for rocket fuel. Liquid oxygen typically constitutes approximately 80% of the mass of rocket propellant. Producing oxygen directly on the Moon could dramatically reduce the cost of lunar and deep-space missions by eliminating the need to transport heavy fuel up from Earth’s gravity well. And of course it is a component of breathable air for settlers.

The lunar surface is covered in regolith composed mainly of silicate minerals and metal oxides. Despite the absence of an atmosphere, oxygen is the most abundant element on the Moon, making up about 45% of the regolith by weight.

When comparing the over twenty techniques that have been proposed for oxygen extraction—including carbothermal reduction and molten salt electrolysis—most require imported consumables like hydrogen or methane. Solar vacuum pyrolysis is advantageous because it:

  • Requires no consumables as it utilizes only solar energy and natural vacuum, both in abundance on the Moon.
  • Reduces logistics as there are no reagents to recycle or transport from Earth.
  • Lowers reaction temperatures because the low pressure of a vacuum environment favors the reduction of metal oxides, allowing the process to occur at more manageable temperatures.
  • Provides high efficiency via solar concentrators which can deliver high thermal power densities (up to 350 W/kg) without the energy conversion steps required by electrical systems.

By way of historical context, the concept of vaporizing lunar regolith was first explored in 1971 using samples of lunar soil returned by Apollo 12. Early researchers like Steurer (1982) proposed the theory of solar pyrolysis, calculating potential yields of 17%, but no solar experiments were conducted at that time.

Subsequent studies by Senior (1992) and Šeško (2024) successfully heated simulants and observed qualitative evidence of oxygen release, such as pressure increases or changes in material composition. However, technical challenges—including glass window breakage and the limitations of mass spectrometry—prevented these researchers from precisely quantifying the amount of oxygen produced. The current study bridges this gap by introducing a new analytical method using a trace analyzer to quantify oxygen within a carrier gas.

Before conducting experiments, the researchers modeled the behavior of heated lunar regolith through thermodynamic analysis of EAC-1 simulant (European Astronaut Centre-1, a high-fidelity lunar regolith simulant developed by the European Space Agency). They used the Gibbs energy minimization method via HSC Chemistry 10 (a process modeling platform widely used in the metallurgical and chemical industry). The model simulated the behavior of EAC-1 regolith simulant—which closely matches the oxygen content of real lunar soil (approx. 44%)—under temperatures up to 3000°C and pressures ranging from 10 mbar to 3 X 10-15 bar.

The key findings of the analysis included:

  • Temperature Dependence: At a pressure of 10-2 bar, the optimal reaction temperature was roughly 2600°C.
  • Pressure Impact: Lowering the pressure significantly reduces the required reaction temperature. At lunar surface pressures, the reaction could occur at temperatures as low as 950°C.
  • Oxygen Species: High temperatures and low pressures promote the formation of monoatomic oxygen (O), though this study focused on quantifying diatomic oxygen (O2).

The researchers noted that while the model provides a “target” for yield, it assumes a closed system at equilibrium. In practice, the experimental reactor will be an open system where species are constantly removed, shifting the equilibrium to promote further reduction via Le Chatelier’s principle.

Digging in to the setup and methodology, the experiments were conducted using a specialized solar reactor at the French national laboratory PROMES (Procédés, Matériaux et Énergie Solaire, or in English, Processes, Materials and Solar Energy), which is managed by the French National Centre for Scientific Research (CNRS).

The components of the apparatus included:

  • Solar Concentrator: A 2-meter diameter parabolic dish focusing sunlight into a 2 cm focal spot.
  • Tracking and Control: A heliostat provided real-time solar tracking, and a system of shutters precisely modulated the solar flux delivered to the sample.
  • Reactor Chamber: A glass vacuum sphere where the regolith pellet sat on a water-cooled steel holder.
  • Gas Analysis: An argon carrier gas was injected to sweep released oxygen into a high-precision oxygen trace analyzer (0.1 ppm to 1% range).
  • Condensation System: A refrigerated copper condenser and a porous stainless steel filter captured volatilized metal species to protect the vacuum pump.

The procedure was initiated by placing a 3.38-gram pellet of EAC-1 simulant in the reactor. The chamber was evacuated and then pressurized with 10 mbar of argon. Solar power was increased in stages with the following observations:

  1. 380 W: Initial melting was observed, but no oxygen was released.
  2. 650 W: A brief oxygen peak occurred, likely due to the reduction of volatile oxides like Na2O and K2O.
  3. 1200 W – 1460 W: Sustained oxygen production began as the sample reached approximately 1800°C.

The key results of the experiment achieved the first direct determination of oxygen reaction yield for this process:

  • Total Oxygen Extracted: 35 mg.
  • Mass Yield: 1.05% of the total processed sample weight.
  • Extraction Efficiency: This represents 2.47% of the total oxygen available within the regolith simulant.
  • Energy Yield: Approximately 31 mg of O2 per kWh.

The study observed that oxygen production happens in distinct stages: an early release during initial melting followed by a more sustained extraction period at peak temperatures. During the process, the vaporized material caused visible “opacification” (clouding) of the reactor’s glass window, which likely reduced the amount of solar energy reaching the sample toward the end of the run.

For characterization of the by-products, after the experiment the researchers analyzed the remaining residue and the deposits found throughout the reactor using SEM/EDS, XRD, and Raman spectroscopy.

With respect to mass balance, of the original 3.38 g sample, 1.82 g remained as a “glassy residue” on the holder, while approximately 1.1 g was vaporized and deposited elsewhere. The final mass recovery was 92%.

An elemental and phase analysis revealed:

  • Residue: Contained non-volatile elements like Aluminum (Al), Calcium (Ca), and Titanium (Ti), along with some Magnesium (Mg) and Silicon (Si).
  • Deposits:
    • On the holder: High concentrations of Sodium (Na) and Iron (Fe).
    • On the window: Primarily Silicon (Si) and Iron (Fe).
    • On the condenser: Mostly Silicon, with some Iron and Magnesium.
  • Crystalline Phases: XRD analysis of the original EAC-1 sample showed it was highly crystalline (containing minerals like augite, forsterite, and anorthite), whereas the residue present in the experiment was largely amorphous glass.

In the Discussion section of the paper the researchers found that the experimental yield of 1.05% was slightly lower than the 1.37% predicted by the thermodynamic model for conditions of 10 mbar at 1800°C. The discrepancy was attributed to several factors:

  1. Open vs. Closed System: The model assumes everything stays in the reactor, while the experiment continuously pumps gases out.
  2. Kinetics: Real-world reaction rates and temperature distributions within the pellet are not accounted for in basic equilibrium models.
  3. Argon Dilution: The argon carrier gas is a “double-edged sword.” While it allows for accurate quantification and prevents oxygen from recombining with metals, its presence increases the total pressure, which works against the pyrolysis reaction.

Although these numbers do not sound significant, the study demonstrates that solar vacuum pyrolysis is a viable, reagent-free method for extracting oxygen from lunar regolith. Beyond oxygen, the results suggest that fractional separation of metals is possible, as different elements vaporize and condense at different locations and temperatures. These findings are promising to inform follow-on studies to develop in-situ metal refining processes to provide feedstock for building lunar infrastructure.

Future work will focus on lowering operating pressures to further increase oxygen yield, customizing the reactor to allow for high carrier gas flow without increasing total chamber pressure, and development of advanced kinetic models that account for temperature gradients within the regolith.

By successfully quantifying the oxygen yield, this research achieves an important benchmark for designing the next generation of hardware intended to support a sustainable human presence on the Moon. Once scaled up, solar pyrolysis factories could supply breathable air in situ for hotels like those planned by GRU Space and other dwellings in communities envisioned by Lunar Cities, a StellarWorld company.

Illustration depicting a stroll down a boulevard with shops, cafes and restaurants in an underground lunar community called District 1 planned by the company Lunar Cities, which could be supplied with oxygen harvested from lunar regolith via solar pyrolysis. Credit: Lunar Cities

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Room with a view on the Moon

Artist rendering of what could be the first hotel on the Moon. Credit: Galactic Resource Utilization Space

Galactic Resource Utilization (GRU) Space published a white paper in January outlining their ambitious plans for a combination lunar base and hotel on the Moon. They believe this plan will accelerate humanity’s transition to an interplanetary species. Authored by the founder of the startup Skyler Chan (a recent UC Berkeley graduate with experience in space hardware and software), the document critiques the current state of the space industry and proposes a private-sector-led approach centered on lunar tourism as the catalyst for broader infrastructure development. GRU Space, backed by Y Combinator, was founded last year.

Chan asserts that humanity stands at a pivotal moment where becoming an interplanetary civilization is achievable within our lifetimes. He argues that the current legacy space ecosystem relies heavily on two pillars: government-subsidized exploration (such as NASA’s Artemis program) and massive launch capabilities (e.g. the Space Launch System and SpaceX’s Starship). However, a true commercial “lunar economy” remains virtually nonexistent. The industry suffers from a stagnation cycle—companies wait for government contracts to fund development, while agencies demand proven hardware before committing funds. This creates a deadlock where advanced technologies (e.g. lunar robotics, power systems, comms) exist in isolation without real customers or demand drivers.

GRU Space rejects this dependency on slow government timelines and “customer discovery” phases. Instead, the company aims to create immediate, tangible value for people on Earth to jumpstart economic activity off-world. Their core thesis: space tourism, specifically a lunar hotel, is the fastest and most practical “wedge” to bootstrap a self-sustaining lunar economy. Chan’s proposed solution: GRU Space’s flagship project to build and operate the first hotel on the Moon, initially as a high-end tourism destination for short multi-day stays. This hotel would serve paying customers (with reservations already open for deposits ranging from $250,000 to $1 million) while simultaneously demonstrating and de-risking technologies essential for permanent lunar infrastructure. GRU’s innovations and phased approach include:

  • Mission I (2029): A small ~10 kg payload delivered via a Commercial Lunar Payload Services (CLPS) lander to test core habitation technologies, particularly an inflatable structure featuring an airtight bladder, structural fabric, micrometeoroid shielding, and thermal/UV protection layers.
  • Mission II (2031): Deployment of a lunar cave base using inflatable systems positioned near a lunar pit or lava tube skylight for natural radiation shielding and resource access. Although not in their current plans, this could pave the way for eventual pressurization of a lava tube for habitation, a concept that has already had preliminary studies completed and covered by SSP.
  • Mission III (2032): Delivery of the first operational lunar hotel via a heavy-lift launch vehicle and lander, accommodating up to four guests initially (with plans to scale to 10 in later versions) located in scenic locals, featuring stunning views of Earth and thrilling extravehicular activities.

The initial hotel will be constructed from inflatable modules shipped from Earth. Future expansions will transition to in-situ resource utilization (ISRU)—processing lunar regolith into durable bricks or structures using automated robotic systems. This reduces launch costs dramatically and enables scalable construction of roads, warehouses, mass drivers (proposed by Elon Musk recently), and other base elements including locally sourced oxygen. GRU’s team is staffed perfectly for these technologies. Cofounder and Member of Technical Staff Kevin Cannon is a planetary geologist and an authority on ISRU. He’s been the source for several posts on SSP and will know exactly where and how to access lunar resources needed for the effort.

The lunar hotel is envisioned to be a high-end destination that generates revenue from customers coming up from Earth, while simultaneously validating ISRU, habitation and life support technologies for more expansive infrastructure.

GRU Space’s broader vision after the hotel positions the company as an architect of long-term human presence on the Moon and Mars with a technical roadmap progressing as follows:

  • Solve the problem of off-world surface habitation via the hotel
  • Expand to support a full base with infrastructure including roads, resource processing, and storage.
  • Replicate the model for population centers on Mars for millions of people.

The approach leverages commercial transportation (e.g., from SpaceX or Blue Origin) and focuses on creating goods/services with Earth-side value (tourism experiences) to generate revenue and prove viability. This contrasts with government-led efforts by prioritizing private customers and rapid iteration.

Overall, the document combines technical roadmap details with economic philosophy, emphasizing self-reliance, revenue-driven development, and urgency in seizing the current window for interplanetary expansion. While ambitious and early-stage (with no operational hardware as of yet), it reflects a startup mindset applied to space settlement, backed by expertise in ISRU, robotics, and space systems from the founding team.

Chan concludes the white paper with a bold claim: by building the first lunar hotel, GRU Space will outflank the traditional space industry, create the initial spark for a lunar economy, and lay the groundwork for humanity’s multi-planetary future. He frames the project not merely as tourism but as a civilizational necessity—turning the Moon into a stepping stone for permanent, expanding human settlement beyond Earth. The last step in his “Top Secret” GRU Master Plan is humanity becoming a Kardashev Type III civilization! Now we know how he came up with the name!

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Wohrad: The first serious design of an artificial gravity space station

The Habitat Wheel (Wohrad). Redrawing of Fig. 84 from The Problem of Space Travel (Noordung, 1929). Color codes identify various categories of human activities – Blue: Sleep; Yellow: Hygiene; Green: Food; Red: Work and leisure, Grey: Circulation and ancillary spaces. Image and minor edits to text based on Figure 16 of the author’s paper. Credits: Fig. 16, from paper by Sandra Häuplik-Meusburger / Used under CC by 4.0

Before O’Neill’s Stanford Torus. Before Stanley Kubrick’s Space Station V in 2001: A Space Odyssey. Before Von Braun’s Space Wheel. There was Hermann Potočnik’s “Wohnrad”, or Habitat Wheel. Writing under the pseudonym Herman Noordung, his 1929 book Das Problem der Befahrung des Weltraums (The Problem of Space Travel) lays out the first serious architectural design of a rotating space station intended to incorporate artificial gravity for human habitation. In the forthcoming issue of Acta Astronautica coming out in April, space architect Sandra Haeuplik-Meusburger examines the early space station architecture via a digital and physical reconstruction. Noordung’s design is considered a milestone in space habitat concepts predating practical spaceflight by many decades.

Noordung’s Wohnrad provided one of the earliest fully developed technical designs for a rotating space station. Unlike speculative ideas before it, his design included three components with specific functions — a rotating Habitat Wheel spinning to create artificial gravity for living spaces at the rim. A free flying lab called the Observatory for scientific discovery. And a much larger sun facing solar power plant (Machine Room), also free flying, which would provide power and life support for the Observatory. Earlier scientists (e.g., Konstantin Tsiolkovsky, Hermann Oberth) suggested early ideas for space stations, but Noordung was the first to produce comprehensive architectural and mechanical drawings of one.

Noordung’s rotating wheel was the first space station intended to provide centrifugal force artificial gravity — a hugely influential idea that foreshadowed decades of later space habitat concepts including Von Braun’s Space Wheel in the 1950s, space station depictions in seminal science fiction movies such as Kubrick’s 2001: A Space Odyssey and of course, O’Neill’s Stanford Torus which didn’t come along until 1975. His design not only addressed physiological needs (countering weightlessness) but architecturally integrated human life support, observation, and workspaces into one cohesive structure — a novel systems-level vision at the time.

Artist impression of the interior of a Stanford Torus. Credits: Don Davis / NASA

Haeuplik-Meusburger’s paper underscores how Noordung’s concept was architecturally rich — detailing spatial organization, functional modules, interior arrangements, including the logic for transitions between rotating and non-rotating sections. Her reconstruction work though modern digital modeling and 3D printed archetypes reveals architectural relationships between modules in more detail than prior historical treatments. Digital reconstruction of the original design provides new insights into proportional relationships, functional layout, and how Noordung envisioned human interactions in space. 3D printing prototypes helped the author reinterpret design logic in ways not possible from 2D archival drawings.

Lets dive in to the details. The author uses a mixed-method architectural and design research approach combining historical analysis with digital and physical reconstruction of Noordung’s original space station concept. She starts by collecting and studying the original material from Noordung’s 1929 book Das Problem der Befahrung des Weltraums — including diagrams, plans, textual descriptions, and images of the Wohnrad (Habitat Wheel) and associated modules (Observatory and Machine Room). The historical review also places the design in the context of other early spaceflight concepts and later influences (e.g., von Braun’s work and science-fiction imagery). This established a baseline understanding of the original design intent and the architectural logic behind the space station.

Next, Haeuplik-Meusburger created a virtual reconstruction taking historical, two-dimensional drawings and texts and translating the original figures into a detailed 3D digital model, probably using CAD or architectural modeling tools (the paper did not specify the software explicitly). This digital reconstruction allowed her to visualize and analyze the spatial layout, proportions, and structural relationships that aren’t obvious in the original flat plans.

After the digital model was created, the author 3D printed a physical prototype enabling tangible exploration of how spaces and modules relate — a method often used in architecture to test and critique design concepts. Moving between digital and physical forms helped identify aspects of the design that might be missed solely through drawing interpretation. Throughout the reconstruction, she provided an architectural interpretation of the design informed by human factors to understand how people would live, move, and interact with spaces under rotational artificial gravity — a layer of analysis beyond mere geometric reconstruction.

The author’s 3D modeling revealed the relationships between modules more clearly than the original drawings. Her findings included unexpected details about occupant circulation in the Habitat Wheel (e.g., access paths, stairs/elevator placement) and how spaces might feel or operate under rotation. This is significant because Noordung’s original descriptive text and flat plans alone could not convey the experience of inhabiting these spaces — a key gap filled by the reconstruction method.

The Habitat Wheel interior is partitioned into activity spaces and individual rooms in the outer rim structure accessed via a central corridor. This is where the crew would spend most of their time close to Earth-like conditions. In the illustration provided above by the author, the layout of the functional areas is shown color coded by the activities envisioned by Noordung.

His original design pegged the radius of the Habitat Wheel at 15 meters with a spin rate of 7.5 rpm resulting in level of artificial gravity of 0.94g. What we know now from many decades of research on human physiology under spin gravity conditions, this arrangement was impractical. The rate of rotation and relatively short radius of the station would likely result in significant Coriolis effects causing vestibule discomfort and disorientation in the occupants. Still, Haeuplik-Meusburger’s analysis places Noordung’s work on firm architectural and design grounds including the practicality of the Habitat Wheel as a concept with enduring lessons for how we might design rotating habitats in the future.

Realizing the issue with the Habitat Wheel’s short radius and high rotation rate, Haeuplik-Meusburger makes use of a Comfort Chart developed by Theodore Hall, a space architect and recognized expert on artificial gravity. The tool is a graph with habitat radius plotted against angular velocity with comfort zones where disorientation is minimized mapped on the plane of the chart. Armed with this information, the author proposes increasing the radius and reducing the rotation rate to a tolerable level, or even considering partial gravity levels of 0.2 to 0.5 g. Incidentally, Hall coauthored a paper on a Mars Cycler with artificial gravity covered by SSP last November.

Exploded axonometric view of the Habitat Wheel components with dimentions according to The Problem of Space Travel (Noordung, 1929). Credit: Fig 14 from paper (with minor caption text edits) by Sandra Häuplik-Meusburger / Used under CC by 4.0

Haeuplik-Meusburger’s use of physical and virtual models helps us better interpret how Noordung imagined habitability and use. For example, spatial organization suggests how living quarters, laboratories, and circulation were meant to function under artificial gravity conditions. In addition, her research clarified how functional logic (like the location of service spaces versus leisure or observation spaces) reflected deliberate design choices, not just schematic ideas.

The Observatory was intended primarily for scientific observation and microgravity research. It was designed to be free flying tethered to the Machine Room which provided power and breathable air via cables and flexible tubes, respectively. The weightless environment would minimize motion enabling equipment to operate more effectively in the absence of vibration. The facility would be equipped with instruments for astronomical observations, Earth monitoring, and telecommunications. The low-gravity environment made precise pointing of telescopes easier and instrument mounting simpler. In addition, there was a laboratory for performing experiments in microgravity. Noordung envisioned the station not just as a place to live but as a scientific platform in orbit, decades before orbital observatories and research facilities became reality.

One notable aspect of the Observatory was that the facility was intended to be placed in geostationary orbit 35,900 km above the Earth’s surface completing one orbit per day fixing it in the sky above the same location. Noordung suggested it could be used as a telecommunications relay station seventeen years before Arthur C. Clark introduced the concept of a communications satellite in a 1945 article in Wireless World.

The Machine Room was the station’s primary power plant, the earliest know example of a solar thermal-engine for use in space. The system featured a 120 meter concave mirror permanently facing the sun and focusing sunlight on heat pipes, whose working fluid would drive a turbine to generate electricity. The condenser and radiator in the thermal-engine circuit would be located at the back of the facility shielded from sunlight. Noordung chose nitrogen as the working fluid for the system over water as it results in significantly lower condenser temperature, leveraging the extreme cooling of the vacuum of space. The Machine Room was the largest facility of the space station containing the main solar power plant with storage batteries, a large transmission station, and a ventilation system serving the Observatory. Noordung’s design was remarkably forward-thinking, addressing real thermodynamic and space-environment challenges in a way that holds up conceptually even now.

One of the most innovative aspects of the space station was the design of the airlock located at the hub of the Habitat Wheel. In addition to addressing the core functions of maintaining internal atmospheric pressure during ingress/egress, allowing safe transition to vacuum and conserving breathable air, Noordung had a novel solution for resolution of the rotating-to-inertial frame problem created by a spinning space station – a rotating airlock chamber capable of counter-rotation.

Since the station’s rim would be rotating to generate artificial gravity and is mechanically connected to the hub, obviously the airlock would be rigidly attached to this rotating structure and have the same angular momentum as the station. Docking spacecraft or individuals on EVAs would have to synchronize their rotational motion to match the door of the airlock, which complicates entry or exit. Noordung’s solution was a system in which the astronaut would enter the airlock (e.g. when exiting the station) while it is rotating with the the habitat wheel. The chamber would be then mechanically driven to de-spin in the opposite direction of the station’s spin. When its angular velocity cancels out the station’s rotation, the airlock would become inertially stationary relative to space outside of the ship, upon which the outer hatch could be safely opened. Noordung’s design included ball-bearing systems, rotational drive mechanisms and sealed rotational interfaces implying that there would be a structural ring allowing relative motion between rotating and non-rotating sections, a mechanical transmission capable of controlled deceleration and a pressure sealing mechanism across a rotating joint. The latter requirement is mechanically demanding and remains challenging even in modern engineering – but he anticipated the mechanical need even though he did not mathematically model these issues in modern terms.

As an aside, the airlock concept was not the first ever conceived (airlocks were already used in mining, tunneling, and civil engineering projects on Earth in those times), but it is one of the earliest detailed proposals of an airlock in spaceflight literature of that period, specifically designed for a space station and EVA-type operations.

Since the station’s life support system was not intended to be ecologically closed and the facility was not intended to be crewed permanently, Noordung understood that supplies needed to be conserved as resupply from Earth would be expensive, especially prior to the advent of reusable rockets. Thus, his design pumped precious air in the airlock back into the station rather then vent it to space upon exit.

Original illustration of Noordung’s airlock concept (Figure 76 in The Problem of Space Travel, Noordung, 1929) Top view of the exterior door and section through the rotating airlock of the Habitat Wheel.  Credit: text by Sandra Häuplik-Meusburger with minor modification / Used under CC by 4.0

Haeuplik-Meusburger’s modeling and 3D printed physical reproductions reveal clearer spatial and operational insights about how the airlock access points functioned within the overall station layout showing relationships to the hub, circulation paths, and machinery areas. These aspects were not apparent in Noordung’s original 2D drawings as they compressed depth and circulation in ways that are hard to interpret from flat figures. For example, the air lock’s position in the axial hub is not incidental. It sits in a circulation node, not an isolated compartment. Her reconstruction reinforces that the airlock was not an accessory to the station but was embedded in a carefully organized hub as part of a systems cluster including machinery, life-support infrastructure, low-gravity workspace and external access. Seeing that integration clearly in 3-D strengthens the argument that Noordung was thinking in systems-architectural terms, one of the main conclusions of the paper. This systems integration is easier to recognize when viewing the station as a volumetric structure rather than separate diagrams.

Haeuplik-Meusburger’s analysis is innovative in how it reconstructs Noordung’s foundational ideas that deeply influenced both the technical lineage of space habitat design, and the cultural imagery of space stations in science and fiction. Her methods demonstrate how digital/physical reconstruction can deepen understanding of design concepts that were never constructed. Finally, the work reveals architectural details and ergonomic considerations that had previously been obscured in the original diagrams. By re-evaluating Noordung’s work with new modeling techniques, the paper provides both historical clarity and design insight that enriches our understanding of Noordung’s prescient visions for living in space, many of which were ahead of his time.

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A vision for industry on the Moon

Credits: Michael Nayak / Air University Press

Air University Press, the academic publisher of the U.S. Air Force, this last July published the The Commercial Lunar Economy Field Guide: A Vision for Industry on the Moon in the Next Decade, edited by Michael Nayak. The document presents a revolutionary blueprint for the transformation of the Moon from a scientific curiosity into a vibrant, self-sustaining industrial marketplace in the 2030s. Central to this vision is DARPA’s 10-Year Lunar Architecture (LunA-10) initiative, which seeks to establish integrated, interoperable infrastructure that lowers the barrier to entry for all lunar users. This may help with execution of the Trump Administration’s recent Executive Order (EO) which aims to establish a space policy “… that will extend the reach of human discovery, secure the Nation’s vital economic and security interests, unleash commercial development, and lay the foundation for a new space age”. The Field Guide and the EO are not perfectly aligned but the former provides an architectural blueprint to implement the strategic mandate prescribed by the latter. The EO provides the authority and deadlines (e.g., returning to the Moon by 2028), while the Field Guide provides the technical and economic pathways (LunA-10) to achieve those goals in a manner that will add value for taxpayers. While diving into the specifics of the Field Guide, along the way I’ll highlight how it will help implement the EO.

A Strategic Vision Beyond Unsustainable Symbolism

For decades, lunar exploration has followed a “Flags and Footprints” paradigm—symbolic, government-funded missions that are entirely self-reliant, bringing every gram of power, water, and data storage from Earth. The Field Guide argues that this approach, while scientifically valuable and a display of national pride, is economically unsustainable at the current “million-dollar-per-kilogram” cost of delivery. This is in alignment with the EO which calls for enhancing cost-effectiveness of exploration architectures while establishing initial elements of a permanent lunar outpost by 2030 to ensure a sustained American presence on the Moon, which will lay the groundwork for the exploration of Mars.

The Role of LunA-10

LunA-10 serves as a catalyst to seed the foundational nodes of a future economy on the Moon and in cislunar space. Similar to how DARPA fostered development of the internet and GPS, LunA-10 identifies “scalable nodes” where government investment can accelerate commercial capability. The goal is to move toward a model where NASA and commercial industry can purchase utilities—like power and data—as services, rather than owning the hardware.

Four Economic Ages of the Moon

The Field Guide identifies four distinct stages of development for the lunar economy:

  1. The Exploration Age (2025–2030): Characterized by one-of-a-kind, government-backed missions. Infrastructure is limited, confined to individual landers which are non-extendable.
  2. The Foundational Age: An era of “trail-building” where lunar surface transportation infrastructure is built out and users begin to subscribe to pilot services for power and communications.
  3. The Industrial Age (Target: 2035): Scaling through commoditization. Multi-service hubs provide consolidated thermal and power management, and large-scale manufacturing begins.
  4. The Jet Age: A state of self-sufficiency where In-Situ Resource Utilization (ISRU) will produce services such a propellent depots (lunar hydrogen and oxygen) to enable frequent, low-cost “rocket hop” transport across the lunar surface, servicing permanent settlements and supporting missions headed for deep space.

Pillars of Commercial Lunar Infrastructure

To achieve this vision, the Field Guide details several critical technology sectors that must transition from their experimental phases to full scale industrialization.

Power and Thermal as a Service

In the Exploration Age, not being able to survive the 14-day lunar night is a primary mission-killer. LunA-10 proposes Infrastructure Hubs—massive solar power towers, some taller than the Statue of Liberty, placed at the peaks of eternal light at the Moon’s south pole, a concept that SSP has explored previously. Here is where the Field Guide diverges a bit from the EO, as the latter calls for surface nuclear reactors as a source of reliable power, prioritizing this initiative to be implemented by 2030. The authors of the Lunar Power chapter were operating under the assumption that NASA’s nuclear Fission Surface Power project would not produce hardware soon based on current TRLs, so this source of power was outside the LunA-10 timeline. Of course solar power could be complementary to nuclear power sources. With this approach these hubs would include:

  • Multi-Service Nodes: The power towers do more than collect solar energy; they serve as “Swiss army knives,” on the Moon providing wireless power transmission, communication relays, and hosting Positioning, Navigation, and Timing (PNT) signals.
  • Thermal Microgrids: Just as Earth-based buildings use central HVAC systems, lunar thermal hubs will manage heat for multiple users. They can recycle waste heat from high-energy activities (like mining) to keep nearby robotic assets warm during the lunar night, significantly reducing the mass each mission must carry for thermal survival. This aligns with the EO’s call to deploy nuclear reactors on the Moon which will need to dissipate waste heat that can be put to use.

Logistics: The Lunar Rail Network

Transportation is the lifeblood of any economy. Initially, lunar rovers will be slow and inefficient; moving the cargo of a single heavy lander over long distances could take thousands of hours.

  • The Lunar Railroad: The Field Guide details a plan for a lunar rail network that dramatically increases the speed and volume of cargo transport.
  • Multi-Use Corridors: These rail lines would serve as integrated infrastructure conduits. Alongside the tracks, corridors would include wired power lines, data cables, and pipelines for gas and/or fluid transport. This “bundling” of services reduces the amortized cost for every company operating along the route.

Mining and the Metal Ecosystem

Sustainable settlement requires moving away from Earth-dependency through ISRU.

Conceptual illustration of the Lunar OXygen In-situ Experiment (LOXIE) Production Prototype, part of the Pioneer Astronautics (now part of Voyager Space Holdings) MMOST system. Credits: Mark Berggren / Pioneer Astronautics
  • The Circular Economy: The vision is a “reduce, reuse, recycle” ecosystem where expended rocket stages or other used assets are repurposed for storage and scrap metal is forged into new products on-site.

Orbital Infrastructure: Cislunar Supply Hubs

The economy extends beyond the Moon’s surface into cislunar space.

  • Space Harbors: Orbital aggregation hubs would act as deep-space analogs to terrestrial maritime ports hosting multiple value streams. Services would include rocket gas stations featuring robotic propellent transfer of stored hydrogen, oxygen, and methane; consolidated edge computing centers providing high-performance computing as a service such as autonomous docking calculations or mineral analysis by the hub’s more powerful servers; commodity sharing allowing arriving spacecraft to plug into the harbor to share excess solar power or fuel. By centralizing these activities, a space harbor would lower the mass of payloads a company must launch from Earth, effectively lowering the barrier to entry for any new commercial lunar venture. Arkisys has already begun to develop this type of infrastructure with The Port.
Conceptual illustration of The Port, a modular orbital platform under development by Los Alamitos, California-based Arkisys that will provide services for space assets such as refueling, battery recharging, thruster installation, repair, etc., laying the ground work for large-scale space harbors. Credit: Arkisys
  • Satellite “Retirement”: This model moves away from the “one-and-done” satellite paradigm toward a symbiotic system where older assets are repurposed as sharable resources contributing to the growth of the hub.

Economic and Legal Enablers

The Field Guide emphasizes that technology alone cannot build an economy; a transparent and predictable market framework will be needed.

Property Rights and Law

Under current international law (i.e. the Outer Space Treaty), nations cannot “own” the Moon. However, the Field Guide argues for “Continued Use” and “Allocated” rights, where companies can have exclusive control over the specific resources they extract and the infrastructure they build. The Artemis Accords provide the foundation for global consensus on these principles.

The Commodities Exchange and Board of Trade

To attract serious private capital, the Moon needs market transparency. The Field Guide recommends establishing a Space Commodities Exchange and a Lunar Board of Trade to define the quality and value of lunar resources like oxygen and regolith. This would allow for trading, hedging, and financing similar to terrestrial commodities like gold or oil.

Interoperability via the LOGIC Consortium

A major risk to a nascent economy is vendor lock-in where different companies’ hardware cannot communicate or share power without significant switching costs. To prevent this, DARPA established the Lunar Operating Guidelines for Infrastructure Consortium (LOGIC). LOGIC focuses on creating voluntary consensus standards for docking ports, power connectors, and communication protocols, ensuring the Moon becomes an open platform rather than a fragmented collection of proprietary systems.

Artist’s concept of commercial lunar infrastructure that would benefit from accelerating interoperability standards via LOGIC. Credits: DARPA

The Path to 2035

The Commercial Lunar Economy Field Guide concludes that while the engineering challenges of the Moon are “DARPA-hard,” they are solvable. By 2035, the goal is to reach break-even where the economy becomes self-sustaining and the risk for private investors is sufficiently lowered.

Successfully building this infrastructure will do more than just unlock the Moon; it will provide the operational experience, fuel and infrastructure (via ISRU) necessary for humanity to expand throughout the Solar System and eventually, to the stars. The Moon will no longer be just a destination for flags and footprints, but a key stepping stone on the path to becoming a spacefaring civilization.

Execution of the EO in Alignment with the Field Guide

To implement the Executive Order using the principles of the Field Guide the following actions should be prioritized with the caveat that the deadlines specified in the EO will be challenging to meet using many of the technologies in the Field Guide, given they’re current TRLs. Still, regardless of aspirational timelines that may be pushed out, the actions below will ensure that when commercial lunar development comes together in the 2030s, it will be cost effective and sustainable.

Action 1: Immediate Transition to Lunar Commodity Contracts

  • The Problem: Procurement of traditional government-owned hardware is slow and expensive.
  • Implementation: Within the 180-day window mandated by the EO, NASA and the Dept. of Commerce should issue Multi-Service RFPs. Instead of buying a rover, the government should buy “Kilometers of Cargo Transport” or “Megawatts of Night-time Power” from commercial infrastructure nodes described in the Field Guide.
  • Lead Agency: NASA (Commercial Moon to Mars Program).

Action 2: Deploy the Lunar Rail Pilot Program

  • The Problem: The EO’s 2030 call for a permanent outpost cannot be sustained long term by slow, battery-limited rovers.
  • Implementation: Accelerate the Field Guide’s Lunar Rail concept to connect the 2028 landing site to the 2030 outpost location. This would create an industrial corridor that bundles multiple services, e.g. power, data, and transportation, to reduce the cost of individual missions. Such linear easements along railroads would serve as the logistical spine for moving massive cargo fostering economic development in accordance with the EO.
  • Lead Agency: DARPA (transitioning to Space Force/NASA).

Action 3: Codify the Lunar Board of Trade

  • The Problem: The EO seeks $50B in private investment, but investors need price certainty.
  • Implementation: Use the Field Guide’s framework to establish a Lunar Commodities Exchange. Define the “Lunar Standards” for oxygen and water purity. This allows private companies to “pre-sell” resources they will mine in the near future to finance their current operations.
  • Lead Agency: Department of Commerce (Office of Space Commerce).

Action 4: Integrate “Defense-by-Commerce” in Cislunar Space

  • The Problem: The EO calls for US superiority and threat detection in cislunar space.
  • Implementation: Equip the Field Guide’s Infrastructure Hubs with Space Situational Awareness (SSA) sensors. By hosting defense sensors on commercial power/comms nodes, the U.S. achieves the responsive and adaptive architecture required by the EO at a fraction of the cost of dedicated military satellites.
  • Lead Agency: U.S. Space Force.

Conclusion

The Commercial Lunar Economy Field Guide is a ready-made roadmap for implementation of the Whitehouse’s Executive Order on Ensuring American Space Superiority. By treating the Moon as an industrial zone the administration can meet the prescribed milestones through commercial leverage and ISRU rather than massive new government spending. Execution of the plan should focus on contractual reform—buying services from the infrastructure nodes as defined in the Field Guide. With power, comms and security systems in place, companies like Galactic Resource Utilization (GRU) Space can build hotels on the Moon starting in the early 2030s to house scientists, entrepreneurs and maybe even tourists as described in their white paper.

Artist rendering of GRU Space’s hotel on the Moon. Credit: GRU Space