Above – Mars Cycler exploded section. Below – Cruise ship-sized Mars Cycler booster (left) and docking configuration (right). Credits: Offworld Industries Corp.
At the 54th International Conference on Environmental Systems held in Prague, Czechia, this past July, a paper was presented describing an innovative design of a large-scale Mars Cycler. The authors, A. Scott Howe, John Blincow, Theodore W. Hall, and Colin Leonard, make the assumption that a significant planetary migration to Mars will happen in the near future, citing Elon Musk’s often stated goal of establishing a one-million person colony on the Red Planet by 2050. The authors argue that Starship will not be a suitable transportation method for a large, non-professional clientele on what has historically been a six-month journey due to the physiological and psychological health risks of a long-duration mission (not withstanding a recent paper penned by University of Santa Barbara physics undergrad Jack Kingdon proposing two trajectories that reduce transit times to between 90 to 104 days each way).
Instead, they envision a “cruise ship” approach using a large, robotically constructed Mars Cycler that would continuously travel between Earth and Mars. The concept for a Mars Cycler was first conceived by Buzz Aldrin in a 1985 paper, and in recognition of his invention, is often referred to as an Aldrin cycler. This particular cycler design is advantageous because it would use minimal propellant to maintain its trajectory. The concept features a dual-torus structure, with a non-rotating outer torus for docking and a rotating inner torus to provide artificial gravity. The paper lays out in detail the specifications for a minimal-sized version with crew capacity of 52-61 people, and calculates the mass and equipment required for the vessel. The authors estimate that it would take 63 Starship launches (version 3) to deliver the construction materials and propellant to low Earth orbit (LEO). A scaled up larger cruise ship-sized version with a capacity of 1000 occupants would take 428 Starship version 3 launches, which is within the range of engineering possibility and certainly within the launch rate of thousands of Starships Elon Musk envisions as part of his Mars colonization plans.
The Mars Cycler would be assembled using Offworld Industries Corporation’s Sargon System, a family of new construction machines the company claims could build an entire space station in half a year (Blincow is CEO of Offworld Industries Corp). The novel construction technology autonomously assembles preformed hull panels loaded in a magazine, robotically dispensed, formed and welded into large toroidal (or other shaped) space stations ready to be pressurized.
The paper advocates for the cycler to provide artificial gravity to mitigate the deleterious health impacts of microgravity allowing occupants to maintain healthy muscle and bone density throughout the journey. The proposed design decouples an inner artificial gravity centrifuge from an outer non-rotating torus, which offers several operational benefits:
Distributed docking ports: The non-rotating outer torus can accommodate multiple visiting vehicles docking at various points around its perimeter.
Fixed systems: Solar panels and radiators can be mounted without the need for gimbals or motorized mounts, simplifying the design.
Seamless transfer: Crew and cargo can be transferred between visiting vehicles and the cycler without the need for spin-up or spin-down procedures.
The paper identifies several challenges to overcome in order to realize an operational Mars Cycler. The top five include:
Large-scale space construction: The project requires the construction of very large orbital structures. A key challenge is maintaining tolerance control during assembly, ensuring panels fit together precisely and the torus closes properly.
Attitude control and maneuvering: The paper assumes, but does not detail, that maneuvering large quarter-toroids in proximity to each other will be possible without “exotic solutions’. This is a significant challenge because each section would have its own center of mass and orbit, creating strain on connected elements.
Artificial gravity implementation: A number of difficulties are discussed, including economic spin-up/spin-down, docking procedures while the structure is spinning, and performing extra-vehicular activities (EVAs) under rotation. The paper also notes that transferring power, control, information, and liquids between the rotating and non-rotating segments would be challenging.
Mars surface infrastructure: The paper acknowledges that a major challenge is the “big elephant in the room of Mars surface infrastructure”. The entire concept is based on the assumption that the necessary infrastructure, such as propellant production facilities, will be in place on Mars by the time the cycler is ready.
Life Support Systems: Sustaining human crews on a cycler for extended periods (e.g., months-long transits) requires robust life support systems for air, water, food, and waste management. The paper underscores the challenge of maintaining these systems with minimal resupply over multiple cycles.
Assuming these challenges could be solved, this interplanetary cruise ship design of a Mars Cycler is a new approach to deep-space travel, elegant in its simplicity. It offers a potential solution to the challenges of long-duration missions by providing artificial gravity via a rotating inner torus to ensure the health and well-being of future Mars colonists.
In addition to these cyclers providing a mode of safe space transportation, such large artificial gravity space stations could be permanently located in orbit around planets or moons that have surface communities in split life cycle space settlements which SSP covered recently. Such a facility could have duel use as an Earth-normal gravity crèche, providing birthing centers and early child development for families settling in the region. Colonists could choose to split their lives between rearing their young in healthy normal gravity settings until their offspring are young adults, then moving down to live out their lives in lower gravity surface settlements – or they may choose to live permanently in free space.
Artist rendering of a robotic space farm on Mars controlled by a computer network utilizing artificial intelligence. Credits: Bryan Versteeg / Spacehabs.com
In an article in the National Space Society Space Settlement Journal, Bryce Meyer examines the integration of Artificial Intelligence (AI) into computer networks for space settlements. Meyer, an aerospace engineer, computer scientist and biologist is the founder and CEO of Cyan React, LLC, a startup that designs compact photobioreactors and provides expertise in space agriculture and life support for space habitats.
The paper describes the critical role of AI networks will play in enabling sustainable space settlements whether they be on the Moon, Mars, or in free space. These colonies, envisioned to minimize Earth resupply and achieve self-sustaining commercial operations, will face challenges due to limited human occupants (often under 100) and the absence of specialized expertise. AI systems can provide a solution that will bridge knowledge gaps, manage complex operations, and ensure rapid responses to critical issues, such as life support failures, where human reaction times may be insufficient.
The article categorizes AI into distinct families suited for space applications. Neural networks, good at pattern recognition, could help identify equipment anomalies. Generative AI (GAI), excellent at diagnostics and creative problem-solving, could propose solutions for crop failures in space farms or other equipment failures. Regression models would be leveraged for predictive analytics like forecasting resource needs.
These AI systems require robust integration with settlement infrastructure, using standard protocols like TCP/IP for communication. Training of AI agents involves learning from a pre-settlement knowledge base, periodic updates from Earth, and real-time inputs from sensors monitoring environmental conditions, equipment, and biological systems. Error management will be managed with AI outputs cross-checked by other AIs, rule-based systems, or human oversight to prevent cascading failures in critical systems.
Network architectures are key, with Local Area Networks (LANs) enabling low-latency, high-speed communication for real-time tasks like alarms and life support, while Wide Area Networks (WANs) connect settlements to external systems, such as orbital infrastructure or Earth-based servers . AI placement is strategic, positioned near action points within habitats (e.g., farms, life support systems) to minimize latency and ensure reliability in harsh extraterrestrial environments. Power constraints and radiation hardening are critical considerations for AI hardware.
The article presents a detailed scenario illustrating AI coordination in a mass flow system, as would be required in space farm. For example, crop wilting is detected by sensors, triggering a cascade of AI-driven actions: neural networks diagnose the issue, GAI suggests solutions (e.g., adjusting nutrient levels), and regression models predict outcomes. Human settlers, guided by augmented reality interfaces, validate and implement solutions, ensuring effective collaboration. The scenario underscores the need for AI to operate at multiple scales—individual plants, farm systems, and settlement-wide networks.
Bryce agreed to be interviewed via email on this enabling technology for space settlement. I am very grateful for him taking the time to dive deeper into the topic and for his detailed responses to my questions. Here is our discussion:
SSP: You mentioned that many of these AI systems are already in use in indoor farms and factories. Can you provide some examples of these instances?
BM…Not trying to pump a particular company but here are common examples: Siemens is one of many companies that make networks of these AI enabled control systems, with control center software now: Siemens Industrial Copilot and SmartTron as well as AIRLOCK(InterLock) Systems.
There are also many new entry startups in this area, such as AGEYE (see below), and others, many have already tried and failed as businesses. Emerson Process is similar, with many offerings and architectures in Chemical Process Automation and Response. BASF is another with it’s xarvio® Digital Farming Solutions. Monnit makes Internet of Things (IoT) plant sensors and sensor reporting software.
It is a very active business area bridging strict rules based to AI enabled rules based and GAI systems with IoT.
SSP: In your example of an AI farm agent detecting a wilting problem with a tomato plant and coming up with a solution, you acknowledged that there are many ways in which ecosystem failures could a occur in a space farm and these scenarios would have to be anticipated to train the AI systems. Has work already been started on an AI controlled farm fault tree analysis, perhaps by the entities running the indoor farms you mentioned in Item 1?
BM…Absolutely! IoT and AI are used in combination in many indoor farms now, just not all the way to the point as shown in the paper, including the ‘recreational plant’ market and for food plants. This is in active work now by many companies, AGEYE is one company that does have integrated solutions like the farm part of the paper (or very close to it). With a little development, automated control will combine the systems in #1, with the farm systems, with more advanced and trained systems, IoT sensors and controllers, to get to the settlement level. It will take a merger of these to get there, but we are very close. Have parts, just need to integrate to get to the vision in the paper.
SSP:Prior to implementation for safe use in a space colony, AI systems would have to be trained on a variety of settlement functions in ground-based analogs. Perdue University’s Resilient ExtraTerrestrial Habitats Institute is doing work in this area as well as the Space Analog for the Moon and Mars at the Biosphere 2 facility in Arizona, and of course MELISSA in the EU. Are you aware of any other teams in academia or government working on this now?
BM…Really miss Ray Wheeler’s et al. NASA Biomass Production Chamber, which was the right size and type, would just need updates.
South Pole research station would work well for testing these systems…in a harsh place, limited human presence.
I know Space Development Network is proposing an inflatable farm to develop this technology too, though it needs funding.
AI control for factories and indoor farming is an active corporate area and they have their own extensive facilities, including near my home in St. Louis with Bayer (formerly Monsanto), though they aren’t focused on the particulars of space, per se, yet.
China also has extensive analog labs, since they do seek to beat the USA to long term Moon and Mars settlement. They occasionally publish.
Many colleges have funded work on vertical and indoor farming, several in my home state including at [University of Missouri-St. Louis] UMSL’s planned Yield Lab. Technical Schools like Ranken also teach and develop methods for indoor farming that could help development of these AIs. All of these facilities can be used to shake out AI systems too.
SSP: In private industry, a few companies are actively involved in developing space-based agriculture. I’ve covered one such company, Orbital Farms, which leverages Earth’s “Dark Ecosystem”, the food chain based on bacteria that are chemotrophic, i.e. deriving their energy from chemical reactions rather than photosynthesis. An example of these type of organisms are bacteria that live near volcanic sulfur vents at the bottom of the ocean. The energy inputs and material flows of these ecosystems are 100 times more efficient in water and energy use per unit volume when compared to conventional photosynthetic food production. The very same organisms can be engineered to make pharmaceuticals, plastics, and a variety of other useful complex organic compounds. Have you considered this approach to optimize mass flows and utility in space farm ecosystems?
BM…Of course. I have considered bioreactors, both photobioreactors and non-light based systems, for a decade. They are the Swiss Army Knife of mass balancing, though I don’t see them as primary food source except in emergencies unless 3d printing and other methods become far better in the culinary sense. Food is critical for psychology too. As is the need to see green and feel and smell plants and crops. Bioreactors have many profiles and uses on Earth now, and the dark cycle chemosynthetic systems are among these. I don’t see a lack of electrical power a problem, just my 2 cents, due to nuclear reactors or space solar power in long term settlements, so I see gardens and farms. Carbon is the problem in a mass cycle. However, the dark cycle systems would be essential for making biochemicals that are either lacking from farms and algae or needed to control the mass cycling in systems. Since we are minus the huge soil ecosystem on Earth for a long while, and may need time sensitive production, the dark cycle systems would be a must just to control the overall system. I do see those on spacecraft that have limited volume, that provide bulk calorie cycling, along with smaller plant systems.
SSP: In your example in Figure 12 of a small settlement of 10 people where the mass flows are 22kg per day to and from the farm, how big is the farm in cubic meters and what would be grown there to provide enough sustenance and oxygen for the occupants?
BM…Around 1400 square meters, 2400 cubic meters (very pessimistically) assuming a VERY diverse crop mix including a few shrimp, multiple veggies and crops like potatoes or peanuts/soy, and bioreactor array with tanks, and walking areas, with continuous crop production ad infinitem. Sounds big, but that is about the size of two three-story healthy midwestern suburban houses, very roughly. Less diverse crop sets can shrink the farm drastically, to around 25% of the size, but with less dietary diversity.
SSP:With respect to training AI systems to be “space rated”, the first iterations to be implemented off Earth will not be entirely autonomous (as you have shown in your examples) and will have humans in the loop until error rates can be reduced to some tolerable level. With the speed at which AI and robotics are progressing today, while at the same time, settlement of the Moon and Mars seems to be advancing at a snail’s pace, do you see the two technologies converging in the near future so that when permanent colonies are finally established, AI networks will be able to autonomously control most critical functions without human intervention?
BM…I never will fully trust AI for everything, and I don’t think the settlers will either, at a minimum due to cybersecurity. That said, the advances in both systems and software will continue to allow more complex settlements monitored by fewer people. Automation will really will be a core technology in expanding settlements, and starting them. Farms could be growing and operating steady state before the first long term residents arrive, and as a settlement expands, it could add modules and let AI get it started and growing before bolting it onto a smaller settlement. Some things will see robotics as repair agents. The AI technology expansion will allow for more long term optimization as well, and continue to add resiliency to the settlement.
You could see a retirement home or factory on the moon with only a few human workers to keep the settlement running, a few medical technicians that are AI assisted, and robots that fix many things without bothering the staff.
SSP:You have suggested in a previous post on SSP that space farms on Mars could be the bread basket for the outer solar system. Another space farm advocate, retired software engineer Marshall Martin, has proposed a roadmap for their implementation starting with ground based analogs, but progressing mainly to rotating free space settlements, eventually resulting in millions of farms feeding billions of people throughout the solar system. When do you think we’ll see the first prototype closed loop farm implemented in space?
BM…I want farms everywhere, grounded and floating [in free space], because I want to see Trillions of Happy, Smiling Babies everywhere.
I would bet either Artemis, a company, or China fields one in the next 35 years for sure, likely sooner, just to prove the concept. Orbital factories could drive the need as much as a lunar base, just to limit resupply, but a Mars base or space station that is beyond cis lunar space will have to have such a close[d] cycle farm as a must due to limited resupply. So, when depends on if the cost to orbit gets very cheap, and cost to [the] Moon gets cheap. Cheap lift in cislunar space would limit the need to fully recycle, but beyond that distance the case gets much stronger. If it stays expensive to [get to] the Moon, the Moon would drive the need, and the farm gets built sooner.
In his conclusion to the article Meyer holds that AI complexity must align with settlement needs, balancing sophistication with reliability. Interdisciplinary collaboration is essential to refine these systems through scenario-based testing and practical implementation. By empowering minimally trained settlers, AI networks enhance sustainability, safety, and mission success, laying a foundation for long-term human presence in space.
AI generated image of Mars in the process of being terraformed. Credit: Gemini
The concept of terraforming Mars was first proposed by John B. S. Haldane in his 1927 essay “On Being the Right Size”, where he touches on the idea of altering planetary environments to make them habitable for humans, including Mars. However, the term “terraforming” itself was coined later by science fiction author Jack Williamson in his 1942 story “Collision Orbit”, where he described transforming alien worlds into Earth-like environments. Haldane’s speculative mention in 1927 is generally considered the earliest recorded proposal of the concept applied to Mars, though it was not detailed or Mars-specific. More technical discussions of Mars terraforming emerged in the mid-20th century with advancements in space science.
Carl Sagan discussed terraforming Mars in his scientific work and popular writings. In a 1971 paper, “The Long Winter Model of Martian Biology: A Speculation”, published in Icarus, Sagan explored the idea of making Mars habitable by using dark-colored plants or microorganisms to reduce the planet’s albedo, leading to better absorption of sunlight to warm the surface, which would release water and carbon dioxide from the polar caps and regolith. This would thicken the atmosphere and create conditions suitable for life. His ideas influenced later science fiction, including Kim Stanley Robinson’s magnus opus Mars trilogy, and remain a foundation for modern terraforming discussions.
The research up until now indicate that it is a complex, long-term project, taking hundreds of years and could be controversial due to ethical challenges. In an article in Nature Astronomy, a fresh look using innovative terraforming methods is presented which could accelerate the warming of Mars by at least 30°C within a few decades, although complete habitability for human flourishing would likely take at least a century. The paper emphasizes the need for scientific research to understand if and how this could be done. Ethical concerns are also addressed with care in the paper.
The article suggests that terraforming Mars should progress in three phases: first, warming the planet; then, introducing hardy organisms to start an ecosystem; and finally, engineering a biosphere with enough oxygen to support human life. The technology proposed to facilitate warming of the planet in the first phase includes orbiting solar sails, silica aerogels, nanocellulose, and engineered aerosols.
Large, lightweight reflective solar sails deployed in space would act as mirrors to reflect solar radiation on to the Martian surface, increasing the amount of heat the planet absorbs. The paper notes that the current insolation of Mars is ~130 W/m², with net absorbed energy at ~125 W/m², resulting in an average surface temperature of about -63°C. By redirecting additional sunlight, reflectors in orbit could significantly boost this energy input which would raise the surface temperature.
Ultra-light, porous silica aerogels with excellent insulating properties could be deployed in transparent or translucent blankets over Martian ice deposits, particularly in polar or high-latitude regions with abundant frozen water reserves. Aerogels trap heat by allowing sunlight to penetrate while preventing infrared radiation from escaping, creating a localized greenhouse effect. This would warm the underlying ice, potentially melting it without requiring global atmospheric changes. The paper emphasizes the aerogel’s biocompatibility, ensuring they would not harm the existence of a potential Martian ecosystem.
Nanocellulose is a lightweight, strong, and renewable nanomaterial derived from cellulose, It could be spread over the Martian surface acting as a thermal blanket similar to aerogels, or as a component in structures that trap heat. The paper suggests it could be tailored to maximize solar absorption in the visible spectrum while reflecting infrared to retain heat, contributing to localized or regional warming. Nanocellulose could support targeted warming, potentially complementing aerogels in creating habitable microenvironments. Its lightweight nature makes it practical for transport and deployment, aligning with the paper’s focus on mass-effective solutions.
Engineered aerosols are fine particles designed to be released into Mars’ thin atmosphere to enhance its greenhouse effect. Unlike older fluorocarbon proposals, which were less efficient and environmentally risky, these aerosols are optimized for biocompatibility and ease of control. These aerosols absorb and scatter solar radiation, trapping heat in the atmosphere. They can be tailored to target specific wavelengths, maximizing heat retention while minimizing harmful effects on potential biology. The paper notes that Mars’ low heat capacity allows these aerosols to warm the planet faster than on Earth, potentially achieving a 30°C increase within a century. By thickening the atmosphere’s greenhouse layer, aerosols could raise global or regional temperatures, facilitating the melting of ice and the release of water vapor, which further enhances warming because water vapor itself is a greenhouse gas.
Another option to facilitate atmospheric warming, proposed in a paper in Scientific Advances last year, would be to engineer and mass produce “nanorods” from Martian regolith tuned to strongly absorb infrared radiation, thereby supercharging a greenhouse effect.
Figure 3 from paper on a nanoparticle warming method for Mars terraforming efforts. Credits: Aaron M. Geller, Northwestern, Center for Interdisciplinary Exploration and Research in Astrophysics via Scientific Advances
Mid-term, anaerobic organisms tolerant to Mars’ harsh conditions could be introduced, initiating ecological succession and producing oxygen. The lead author on the Nature Astronomy paper is Erika Alden DeBenedictis, CEO of the San Francisco based nonprofit Pioneer Labs, who’s mission is to engineer microbes that can thrive in extreme environments. As stated on the website, “These new pioneer species can pave the way to greener planets by remediating soil, upcycling waste streams, and making harsh areas more friendly to life.”
SSP has covered a similar approach to terraforming the Red Planet with introduction of pioneer species such as the desert moss Syntrichia caninervis, an organism that can survive the frigid temperatures, low ambient pressure and harsh radiation on Mars while helping to boost oxygen levels and fostering soil fertility.
This middle phase would be ideal for para-terraforming, a more limited approach to making localized regions of Mars habitable, prior to fully terraforming the entire planet. It involves creating enclosed, controlled environments—such as domed habitats or sealed craters—where temperature, atmosphere, and other conditions are artificially maintained to support human life or simple ecosystems. Kent Nebergall, chairman of the Mars Society Steering Committee, has proposed this approach by building an enclosure over Hebes Chasma, a canyon the size of Lake Erie just north of Valles Marineris.
Top: Artist concept of kilometer scale arches built above space settlements and enclosing a Martian canyon to provide a para-terraformed environment. Bottom: Magnificent view from below depicting these domes at cloud level on a typical summer day. Credits: Kent Nebergall / Aarya Singh
The paper suggests terraforming in this middle phase could support upwards of 10,000 people per site with automated farming, while the end goals are constrained by physical, chemical, and biological limits, perhaps necessitating a multicentury timeline. This phased approach highlights the gradual, research-driven nature of the project, acknowledging the long timescales involved.
The final phase involves establishing a sustainable, oxygen-rich ecosystem capable of supporting advanced plant life and, eventually, the ability to support human settlements without life support systems. Atmospheric oxygen would be increased to at least 0.1 bar to enable humans to breathe without pressure suits. This would be achieved through the widespread propagation of photosynthetic organisms like engineered plants or cyanobacteria. The paper notes that this slow oxygen build-up, potentially taking over a century, requires sustained energy inputs, possibly from multi-terawatt power sources or solar concentrators, to accelerate the process. The project would need ongoing climate engineering to maintain temperature and pressure, such as controlled greenhouse gas releases. Because Mars does not have a magnetic field to deflect solar particle events and galactic cosmic rays, engineered solutions would be required to prevent loss of oxygen and to shield Martian settlers from radiation. Through deployment of large-scale electromagnetic coils or magnetic shields in orbit or on the surface, a localized or planetary magnetic field could be created, mimicking Earth’s magnetosphere. This concept has been proposed by Dr. James Green, former chief scientist at NASA who retired from that role in 2022.
With respect to ethical concerns, there is considerable debate over preserving Mars as a pristine environment versus transforming it, with implications for potential Martian life that may exist there. The paper notes that human presence during exploration and/or settlement will introduce orders of magnitude more Earth microbes (then those that may have been present on probes that have already landed there), necessitating a search for extant Martian life through sample returns and deep aquifer exploration prior to initiation of terraforming efforts. The authors suggest that terraforming technologies could benefit Earth, such as developing desiccation-resistant crops, but emphasize the need for science-informed engagement with stakeholders. The long timescale for terraforming is noted as a constraint for politics and science, highlighting the need for long-term planning and international cooperation.
There are more audacious proposals such as Robert Zubrin and Chris McKay’s plan for terraforming Mars in 50 years. Zubrin, a prominent advocate for Mars exploration and terraforming, argues that there is no extant life on Mars, thus alleviating ethical concerns about altering the planet’s environment soon. In his view put forward in his book The Case for Mars, extensive scientific investigations analyzing data from Mars rovers and orbiters, have found no conclusive evidence of current microbial or other life forms, suggesting Mars is a barren world. He contends that the absence of indigenous life eliminates moral objections to terraforming, as there are no ecosystems to disrupt or native species to harm. Zubrin emphasizes that terraforming Mars into a habitable environment for humans, would foster scientific advancement and human expansion without ethical conflicts, provided ongoing searches for life—such as soil sample returns—continue to yield negative results. This position is echoed in the paper which notes the need to confirm the absence of life through further exploration but supports initiating terraforming research given the evidence to date.
As Mars terraforming efforts advance, the viability of the planet as a sustainable environment for surface settlements may progress according to the Pancosmorio Theory which posits that ecosystems necessary to sustain life gradually acquire sufficient area and availability of resources (e.g. sources of energy) as their circular economies evolve toward closure such that dependency on supply chains from Earth begins to diminish.
The paper makes a compelling case for prioritizing Mars terraforming research, aligning with current exploration priorities while informing future decisions about an eventual human presence on Mars. The authors acknowledge the complexity, controversy, and long-term nature of the project, advocating for a science-driven approach to address feasibility, ethics, and potential benefits for both Mars and Earth.
Artist impression of a lunar habitat designed for resiliency and autonomy. Credit: Resilient ExtraTerrestrial Habitats Institute
The Resilient ExtraTerrestrial Habitats Institute (RETHi) is at the forefront of developing autonomous and resilient habitats essential for space settlement. The NASA-funded organization just released its Impact Report summarizing work completed to date. SSP reported on RETHi back in 2020.
A key driver for RETHi’s imperative of autonomy in these habitats is the increasing communication delays and limited bandwidth that will severely restrict interaction with controllers on Earth as habitats are established further from home. These limitations necessitate new approaches for managing space habitats autonomously, fundamentally shifting the operational philosophy for future missions. Unlike near-Earth operations where Mission Control provides real-time oversight and intervention, the remote and harsh environment of deep space demands that habitats become self-sufficient entities. This means that intelligence, diagnostic capabilities, and decision-making must reside on-board, transforming the paradigm from remote control to local autonomy. This is a critical design constraint that permeates all of RETHi’s research, influencing everything from structural design to life support systems and robotics.
RETHi’s research is organized into three interrelated thrusts, each addressing a critical aspect of a comprehensive framework for self-managing systems:
Resilience (Architecture): This thrust focuses on the fundamental design of habitats. It involves choosing design features and tools to maximize resilience, assessing safety controls, and developing a resilience-based design procedure aligned with NASA’s processes. This ensures that resilience is embedded into the very fabric of the habitat from its inception, making it inherently robust.
Awareness (Detection + Diagnosis + Decisions): Addressing the need for autonomy in operations, this thrust aims to detect damage and disruptions, diagnose issues, and support decision-making autonomously. This represents a significant departure from traditional human space flight operations, which rely heavily on large Mission Control teams. The goal is to enable the habitat to “understand” its own state and the nature of any anomalies.
Robotics (Enable Action): This thrust is dedicated to expanding the capabilities of autonomous systems by increasing the scope of interventions that can be carried out automatically by robots. This is crucial for construction, maintenance, and repair in hazardous environments where human presence might be limited or too risky.
RETHi’s research is supported by three complementary testbeds, each serving a distinct but integrated purpose, forming an efficient iterative design and validation pipeline:
HabSim: This is a computational model of core space habitat subsystems. It incorporates damageable and repairable properties, sensors, and agents for anomaly detection and repair. HabSim can simulate various disruption scenarios, including micrometeorite impacts, fires, Moonquakes, and nuclear leakage. It primarily helps users learn to create and maintain resilient habitats by assessing decision strategies and resilience through simulation-based design, which can reduce mission costs and increase crew safety.
CDCM (Control-oriented Dynamic Computational Model): This capability provides a specialized language for rapid prototyping of machine-readable models that capture causal relationships in complex systems. This enables automatic diagnostic reasoners and uncertainty quantification, which are crucial for developing intelligent, self-diagnosing systems.
HARSH(Human-Centered Autonomous Resilient Space Habitats): This testbed is a cornerstone of RETHi’s research, providing a unique cyber-physical platform for validating the complex interplay of hardware and software in autonomous space habitat systems. As the physical validation layer, HARSH takes the insights, algorithms, and models developed and refined in HabSim and CDCM, and tests them in a hardware-in-the-loop environment to confirm their real-world efficacy.
These three complementary testbeds provide a sophisticated, multi-stage approach to research and development. HabSim allows for broad, rapid computational exploration of scenarios and design strategies, providing initial insights. CDCM provides the formal language and tools for precise diagnostic reasoning and model building. HARSH then serves as the high-fidelity, cyber-physical validation platform, where the most promising concepts from the computational realm are rigorously tested against physical realities. This iterative process—from broad simulation to precise modeling to hardware validation—minimizes risk, optimizes design, and accelerates the development cycle for a mature engineering pipeline of complex, safety-critical systems.
The RETHi Impact Report summarized the status of many of the Institute’s research initiatives. Although all are important, this post will highlight progress in two key areas of interest: The HARSH testbed and the design of a habitat’s Environmental Control and Life Support System (ECLSS).
Purpose and Unique Capabilities of HARSH
HARSH is a cyber-physical testbed designed to investigate advanced systems health management capabilities for complex systems with deep informational dependencies. The facility bridges the gap between digital simulation and physical reality, allowing for a more comprehensive understanding of system behavior.
The platform’s unique strength lies in its ability to trigger realistic disruption scenarios using hardware and test autonomous recovery. This capability distinguishes HARSH from purely computational models by enabling real-world interaction, sensor feedback, and the validation of autonomous responses against actual physical system behavior. While computational models like HabSim and CDCM are invaluable for initial design and rapid prototyping, HARSH serves as the crucial validation bridge from simulation to reality. It is where theoretical models and algorithms are put to the ultimate test against physical realities, including hardware limitations, sensor noise, latency, and real-world environmental interactions. This is an indispensable step for ensuring reliability and eventual flight certification of autonomous systems.
Facilitating Investigation of Advanced Systems Health Management
HARSH’s cyber-physical nature allows for the investigation of advanced systems health management capabilities, which are crucial for maintaining complex space habitats, especially those with deep informational dependencies. This entails a focus on integrated diagnostics, prognostics, and self-healing mechanisms across multiple interconnected subsystems. In a deep space habitat, a failure in one system, such as a power supply, can quickly cascade to others, like the ECLSS or communication networks.
The ability to test autonomous recovery under realistic hardware-induced disruptions is central to HARSH’s role in validating the Awareness (detection, diagnosis, decision) and Robotics (enable action) thrusts in a practical, integrated setting. To attain advanced systems health management capability, a focus that transcends simple fault detection is required. It implies a sophisticated ability to continuously monitor, diagnose, and predict the health of complex, interconnected systems. HARSH’s ability to test deep informational dependencies and autonomous recovery provides a proactive approach to resilience, where the system not only identifies a problem but also takes corrective action to prevent cascading failures and restore functionality, thereby minimizing the need for human intervention and ensuring mission continuity.
Advancing Life Support Systems for Deep Space: RETHi’s ECLSS Research
As we all know, the ECLSS is critical for sustaining human life in the hostile, closed environment of deep space settlements. The life support system provides essential functions such as breathable air revitalization, water recovery, waste management, and thermal control, directly impacting crew health and performance. The extended durations of deep space missions (and eventual evolution to permanent communities) necessitate a highly reliable and resilient ECLSS, capable of operating autonomously and recovering from disruptions without immediate help from Earth, given the significant communication delays and the unlikelihood of the success of rescue operations due to long transit times.
While a habitat’s structural integrity and autonomous systems are vital, the ECLSS provides the breathable air, potable water, and stable thermal environment necessary for human survival. Any significant failure in these systems directly jeopardizes the safety of the habitat’s occupants, making them the ultimate determinant of mission duration and crew survivability. Therefore, the resilience of an ECLSS will directly dictate how long a mission can last and whether the crew can survive unforeseen events, particularly when autonomous recovery is the only option.
Development of High-Fidelity, Physics-Based Simulation Models
RETHi has developed a high-fidelity, physics-based simulation model for an ECLSS, a sophisticated approach that accounts for the underlying physical principles governing the system’s behavior, allowing for a deep and accurate understanding of its performance.
This advanced model is specifically designed to predict interior conditions under nominal and disruptive scenarios. This capability is vital for understanding how the habitat’s internal environment responds to various stresses, from equipment failures to external impacts, and for evaluating the effectiveness of mitigation strategies. This method of modeling can predict interior conditions under nominal and disruptive scenarios, enabling a proactive, rather than reactive, approach to resilience. Instead of waiting for failures to occur and then responding, RETHi is developing tools to anticipate how the ECLSS will behave under various forms of stress. This predictive capability allows designers to identify vulnerabilities, optimize system responses, and develop robust contingency plans before a space habitat is established, significantly enhancing safety, reliability, and the potential for autonomous recovery. It moves beyond simple performance modeling to detailed stress-testing and failure mode analysis in a virtual environment.
Evaluation of ECLSS Resilience Under Nominal and Disruptive Scenarios
The ECLSS simulation model allows for the evaluation of system resilience. This means the model can assess the system’s ability to withstand disturbances, adapt to changing conditions, and recover from various challenges, ensuring continuous life support. By simulating disruptive scenarios, researchers can understand the precise impact of failures, optimize control strategies, and develop autonomous recovery protocols for critical life support functions, minimizing the need for human intervention during emergencies.
Evaluating system resilience under disruptive scenarios goes beyond merely ensuring individual ECLSS components are reliable. It validates that the system has the ability to maintain its critical functions even when components fail or external disturbances occur. This shifts the focus from preventing individual failures to ensuring the overall system can adapt and recover, which is a hallmark of true resilience in complex, high-stakes environments where human intervention may be limited. This holistic view is essential for long-duration deep space missions, where adaptability is paramount.
SSP covered similar research by Curt Holmer in his master degree thesis modelling the stability of an ECLSS back in 2021. That work attempted to capture the complex web of interactions between biological, physical and chemical processes and detecting early warning signs of critical transitions between systems so that appropriate mitigations can be taken before catastrophic failure occurs. RETHi’s approach takes stability modelling to a deeper level, enabling ECLSS designers to understand the complex interdependencies and vulnerabilities of the system to determine proactive countermeasures.
Conclusion: Paving the Way for Future Space Habitats
The Resilient ExtraTerrestrial Habitats Institute at Purdue University is playing an indispensable role in driving the design and development of resilient and autonomous habitats, which are critical for the future of space colonization. The institute’s integrated, multi-faceted approach to autonomous resilience, exemplified by the HARSH cyber-physical testbed and its pioneering ECLSS research, is foundational for achieving long-duration human presence off Earth.
RETHi’s strategic organization into resilience, awareness, and robotics initiatives address the complex challenges of human survival in deep space, where communication delays necessitate on-board intelligence and self-sufficiency. HARSH serves as the crucial validation bridge, transforming theoretical models and algorithms into tested, real-world solutions for autonomous recovery and systems health management. Concurrently, the high-fidelity ECLSS models ensure that the fundamental life support functions remain robust and adaptable under stress, directly impacting crew safety and settlement longevity.
The comprehensive nature of RETHi’s work positions it as a leader in future large-scale, interdisciplinary research initiatives for resilient space habitats. The Institute’s holistic understanding of the complex challenges of space colonization fosters integrated solutions across multiple scientific and engineering domains, supported by robust testing infrastructure. The Institute’s current research findings are a blueprint for effective advanced research and development needed for the next frontier of human expansion into the solar system, emphasizing a paradigm shift towards self-sufficient extraterrestrial settlements.
Illustration of a cylindrical rotating space settlement in Low Earth Orbit. Credits: Grok 3
A paper by German astrophysicist Rainer Rolffs titled Rotation of Space Habitats published last October has been uploaded to the National Space Society (NSS) Space Settlement Journal. The study aims to quantify how much structural mass is required to support both the artificial gravity and the internal pressures in various designs of a rotating habitat. It expands on previous work the author completed on energy flow in such habitats, integrating considerations of cooling, energy collection (via mirrors and photovoltaics), and the distribution of interior mass.
Habitat Geometry and Design Options Rolffs analyzes several geometric configurations, including: – Cylinder: A habitat rotating about its central axis, with design trade-offs between compactness and rotational stability. – Tube: A cylindrical structure rotating perpendicular to its length, featuring rounded endcaps to ensure uniform gravity. – Oblate Spheroid: A sphere that is flattened along the rotation axis, offering a different balance between structural mass and interior volume. – Torus: A ring-like structure where the habitat’s thickness is a fraction of the overall rotational radius. – Dumbbell and Dumbbell with Tube: Two-sphere configurations connected either by cables or a tube; these shapes offer flexibility in managing rotational radius and gravity distribution, especially at smaller scales.
Scaling and Habitat Sizing The analysis scales the design by considering a constant interior volume per person, leading to a range of populations from very small (few individuals) to billions. Lower limits on habitat size are determined by constraints such as acceptable rotation rates (to maintain human comfort) and the mass needed for shielding against radiation. Upper limits are set by the challenges of maintaining co-rotation of critical components like mirrors for sunlight collection and the growing demands on structural integrity and cooling systems as size increases.
Gravity Distribution and Structural Considerations The paper provides detailed methods to compute the gravity distribution inside the habitat by dividing the interior into floors with heights that vary inversely with gravity. Rolffs examines how the structural mass must not only counteract the centrifugal forces (to create artificial gravity) but also support the self-weight of the structure, with different methods for vertical (hanging) versus horizontal (standing) support. A “critical co-rotational radius” is introduced, beyond which certain components (like non-rotating mirrors or photovoltaics) can no longer be kept in co-rotation with the habitat without incurring prohibitive mass penalties.
Trade-Offs in Mass Budget and Optimization Not surprisingly, shielding against radiation is identified as a dominant mass component for small habitats, while for larger habitats, the structural and cooling masses become more significant. The study shows that there exists an optimum size range—between tens of thousands and tens of millions of cubic meters of interior volume—where the payload (interior mass per person) dominates the overall mass budget, and the design can be optimized for cost and functionality. Rolffs finds that different shapes yield different trade-offs; for example, the dumbbell shape is preferable at smaller sizes due to its flexible rotational radius, whereas spheroidal shapes may offer lower structural mass for very large habitats.
Detailed Derivations and Appendices The work includes extensive mathematical derivations provided in three appendices: – Appendix A: Details the geometric parameters and derivations for determining the rotational radius and interior volume for each habitat shape. – Appendix B: Focuses on the gravity distribution within the habitat, explaining how the artificial gravity varies across different floors and regions. – Appendix C: Deals with structural integrity, deriving the requirements for supporting both the artificial gravity forces and the habitat’s own self-weight, including considerations for both vertical and horizontal support systems.
Rolffs’ analysis provides design guidelines that are critical for planning future space settlements, especially in the context of reducing launch costs and using in-situ resources (e.g., processed asteroid matter) for construction. He concludes that while very large habitats are theoretically possible (even accommodating populations in the billions), practical constraints related to cooling, light distribution, and structural integrity likely favor habitats in the medium-size range with optimized shapes such as the dumbbell or oblate spheroid.
Overall, Rolffs provides an in-depth exploration of the physical and engineering challenges associated with rotating space habitats, providing both theoretical foundations and practical design criteria that could inform future developments in space settlement engineering, earning the top spot on SSP’s Artificial Gravity Section as of this post.
Left: Artist impression of the inside of Kalpana One, a free space settlement providing artificial gravity. Credits: Bryan Veerseeg / Spacehabs.com; Right: Conceptual illustration of a colony on the surface of Mars. Credits: SpaceX.
Until recently, space settlement advocates have typically split into two camps: those who favor building colonies on the surfaces of the Moon or Mars, and those who prefer constructing O’Neill cylinders in free space, spinning to provide artificial gravity outside of planetary gravity wells. Readers of this blog know I lean toward the latter, mainly because colonies on worlds with gravity lower than Earth’s could pose problems for human physiology, particularly reproduction. Truthfully, we won’t know if humans can reproduce in less than 1g until we conduct long-term mammalian reproduction experiments under those conditions. It would be far cheaper and quicker to perform these experiments in Low Earth Orbit (LEO) rather than waiting for sufficient infrastructure to be established on the Moon or Mars for biological research.
Another approach involves not sending humans into space at all, instead entrusting space colonization to human-level artificial general intelligence (HL-AGI) and conscious machines—a non-biological strategy. With recent advancements in AGI and automation, conscious HL-AGI robots may become feasible in the near future (though the exact timeline—whether decades or longer—remains a matter of debate). This prospect might disappoint many space advocates who view migration beyond Earth as the next phase of natural biological evolution hopefully starting within our lifetimes. Deploying sentient machines would effectively remove humanity from the equation altogether.
If you’ve been following space colonization in the press you’ve most likely heard of the book A City on Mars by Kelly and Matt Weinersmith. I have not purchased the book but I’ve read several reviews and heard the authors interviewed by Dr. David Livingston on The Space Show to get an understanding of the Wienersmith’s overall viewpoint, which is at the very least skeptical, and to some space advocates downright anti-settlement. The book is very pessimistic taking the position that the science and engineering of space settlements for large populations of people is too challenging to be realized in the near future.
Peter Hague, an astrophysicist in the UK, wrote an excellent three part review setting the record straight correcting some of the critical facts that the Wienersmith’s get wrong. But in my opinion the best critique by far was written by Dale Skran, Chief Operating Officer & Senior Vice President of the National Space Society (NSS). In a recent post on the NSS blog, he links to a 90 page Critique of “A City on Mars” and Other Writings Opposing Space Settlement in the Space Settlement Journal where he provides a chapter-by-chapter, section-by-section response to the entire book as well as rebuttals to a few other naysayer publications [“Dark Skies” (2021) by Daniel Deudney; “Why We’ll Never Live in Space” (2023) in Scientific American by Sarah Scholes; “The Case against Space” (1997) by Gary Westfahl].
However, Skran credits the Weinersmiths with an innovative idea he hadn’t encountered before, one that addresses the challenge of human reproduction in low gravity. They suggest establishing orbital spin-gravity birthing centers above surface colonies on the Moon or Mars, where children would be born and raised in an artificial gravity environment—essentially a cosmic crèche. Skran builds on this concept, proposing that the life cycle of Moon or Mars colonists could be divided into phases. The first phase would take place in space, aboard rotating settlements with Earth-normal gravity, where couples would conceive, bear children, and raise them to a level of physical maturity—likely early adulthood—determined by prior research. Afterward, some individuals might opt to relocate to the low-gravity surfaces of these worlds. There, surface settlements would focus on various activities, including operations to extract and process resources for building additional settlements.
Skran elaborated on this split life cycle concept and outlined a roadmap for implementing it to settle low-gravity worlds across the solar system during a presentation at the 2024 International Space Development Conference. He granted me permission to share his vision from that presentation and emphasized that the opinions expressed in his talk were his own and did not reflect an official position or statement from the NSS.
Taking a step back, the presentation summarized research that has been performed to date on mammalian physiology in lower gravity, e.g. studies SSP covered previously on mice by JAXA aboard the ISS in microgravity and in the Kibo centrifuge at 1/6g Moon levels. The bottom line is that studies show some level of gravity less then 1g (artificial or otherwise) may be beneficial to a certain degree but microgravity is a horrible show stopper and much more research is needed in lower gravity on the entire reproduction process, from conception through gestation, birth and early organism development to adulthood. The question of reproduction in less then 1g is the elephant in the space station living room. In my presentation at ISDC last year, I took the position that the artificial gravity prescription for reproduction could impact the long term strategy for where to establish biologically self-sustaining space settlements leading to a fork in the road: a choice between O’Neill’s vision of free space rotating settlements vs. lower gravity surface colonies (because outside of the Earth all other solar system worlds where it is practical to establish surface settlements have less then 1g – e.g. the Moon, Mars, Asteroids and the moons of the outer planets – I exclude cloud settlements in Venus’s atmosphere as not realistic). I’ve been swayed by Skran’s proposal and have come to the realization that we don’t need to be faced with a choice between surface settlements or free space artificial gravity habitats – we can and should do both with this split life cycle approach.
How would Skran’s plan for settling the solar system work? He suggests we start small with rotating space settlements in LEO like Kalpana Two, an approach first conceived by Al Globus and popularized in his book coauthored by Tom Marotta The High Frontier: an Easier Way. Locating the habitats in LEO leverages the Earth’s protective magnetic field, shielding the occupants from radiation caused by solar particle events. This significantly reduces their mass and therefore costs because heavy radiation shielding does not need to be launched into orbit. In addition, the smaller size simplifies construction and enables an incremental approach. Kasper Kubica came up with a real estate marketing plan for Kalpana in his Spacelife Direct scenario.
Skran promoted a different design which won the Grand Prize of the NSS O’Neill Space Settlement Contest, Project Nova 2. The novel space station, conceived by a team of high school students at Tudor Vianu National High School of Computer Science, Bucharest Romania, slightly resembles Space Station V from the film 2001: A Space Odyssey. Many other designs are possible.
Project Nova 2 rotating space settlement, one possible design of a rotating space settlement initially built in LEO then moved out to the Moon and beyond. Credit: Tudor Vianu National High School Research Centre Team / NSS O’Neill Space Settlement Contest 2024 Grand Prize Winner
But to get there from here, we have to start even smaller and begin to understand the physics of spin gravity in space. To get things rolling Kasper Kupica has priced out Platform 0, a $16M minimum viable product artificial gravity facility that could be an early starting point for basic research.
These designs for space habitats will evolve from efforts already underway by private space station companies like Vast, Above, Axiom Space, Blue Origin (with partner Sierra Space) and others. Vast, which has for years had AG space stations on its product roadmap, recently revealed plans to use its orbital space station Haven-1 to be launched in 2026 to study 1/6g Moon level AG in a few years, albeit without crew. And of course let’s not forget last month’s post which featured near term tests proposed by Joe Carroll that could be carried out now using a SpaceX Falcon 9 as an orbital laboratory where researchers could study human adaptation to AG.
Illustration depicting a SpaceX Crew Dragon spacecraft tethered to a Falcon 9 second stage which could be spun up (in direction of down arrow) to test centrifugal force artificial gravity. Credit: Joe Carroll
Back the plan – once the rotating space habitat technology has been proven in LEO, a second and third settlement would be built near the Moon where lunar materials can be utilized to add radiation shielding needed for deep space. The first of these facilities becomes a factory to build more settlements. The second one becomes a cycler, the brilliant idea invented by Buzz Aldrin, initially cycling back and forth in the Earth Moon system providing transportation in the burgeoning cislunar economy just around the corner. The next step would be to fabricate three more copies of the final design. Two would be designated as cyclers between the Earth and Mars. Building at least two makes sense to establish an interplanetary railroad that provides transportation back and forth on a more frequent basis then just building one unit.
Here’s the crown jewel: the third settlement will remain in orbit around Mars as an Earth normal gravity crèche, providing birthing centers and early child development for families settling in the region. Colonists can choose to split their lives between rearing their young in healthy 1g habitats until their offspring are young adults then moving down to live out their lives in settlements on the surface of Mars – or they may choose to live permanently in free space.
This approach enhances the likelihood that settlements on the Moon or Mars will succeed. The presence of an orbiting crèche significantly reduces the risks associated with establishing surface communities by providing an orbital station that can support ground settlements and offer a 1g safe haven to where colonists can retreat if something goes wrong. This alleviates the pressure on initial small crews on the surface, meaning they wouldn’t have to rely solely on themselves to ensure their survival. Finally, an incremental strategy, involving a series of gradual steps with technology readiness proven at each stage through increasingly larger iterations of orbital settlements, offers a greater chance of success.
The final step in this vision for humanity to become a truly spacefaring civilization is to rinse and repeat, i.e. cookie cutter duplication and dispersal of these space stations far and wide to the many worlds beyond Mars with abundant resources and settlement potential. There’s no need to choose between strategies focused solely on surface communities versus spin-gravity colonies in free space. We can pursue both, as they will complement each other, providing families with split life cycle settlement options to have and raise healthy children while tapping the vast resources of the solar system.
Images of resource rich lower gravity worlds beyond Mars with potential for split life cycle settlement (not to scale). Top: the asteroid Ceres. Middle: Jupiter’s Moons, from left to right, Io, Europa, Ganymede, and Callisto. Bottom left: Saturn’s moon Titan. Bottom right: Neptune’s moon Triton. Credits: NASA.
Artist’s depiction of a space farm in a 56m radius rotating space settlement. Credits: Bryan Versteeg / Spacehabs.com
Editors Note: This post is a summary of a presentation by Marshall Martin that was accepted by the Mars Society for their conference that took place August 8 – 11th in Seattle, Washington. Marshall was not able to attend but he gave me permission to publish this distillation of his talk. There are minor edits made to the original text with his permission. Marshall is an accomplished Software Engineer with decades of experience managing multiple high tech projects. He has Bachelor’s Degree in Mathematics and Physics from Northwestern Oklahoma State University and an MBA in Management of Information Systems from Oklahoma City University. He is currently retired and farms with his in-laws in Renfrow, Oklahoma. The views expressed by Marshall in this post are his own.
The Earth is a Biosphere supporting life which has evolved and thrived on sunlight as an energy source for more than 3.4 billion years.
Therefore!
You would think a few smart humans could reverse engineer a small biosphere that would allow life to exist in deep space on only sunlight.
Furthermore, eventually the sun will run short of hydrogen and transition into a red giant making the Earth uninhabitable in a few hundred mission years. Long before that time, we need to have moved into biospheres in space growing crops for food. But for now….
The cost of food in space (when launched from Earth) is too high. My Estimates: [1,2]
Launch Vehicle/Mission
Cost/pound (USD)
Cost/Person/Day* (USD)
Space Shuttle to ISS
$10,000
$50,000
Falcon 9 to ISS
$1134
$5670
Atlas V[3] to Mars (Perseverance[4] Mars Rover)
>$100,000
$500,000
2 year mission to Mars based on Atlas V costs
>$100,000
$365,000,000
* Assuming average consumption rate of 5 pounds/day
If we assume that the SpaceX Starship will reduce launch costs to Mars by at least two orders of magnitude, the cost/person/day for a two year mission would still exceed $3 million dollars.
Solution: farming in space
Starting with a rough estimate, i.e. a SWAG (Scientific wild-ass guestimate): – A space station farm sized at 1 acre producing 120 bushels per acre of wheat, 60 pounds per bushel, 4 crops per year, yields 28,000 pounds of wheat per year. Using Falcon 9 launch costs, this produces a crop valued at $31.7M per year. If your space farm is good for 50 years, the crops would be worth $1.585B when compared to an equivalent amount of food boosted from Earth at current launch costs.
SWAG #2 – I believe a space farm of this size can be built using the von Braun “Wet Workshop” approach applied to a spin gravity space station composed of several Starship upper stages at a projected cost of $513M. More on that later.
Do we know how to build a space farm? NO!
So how do we get there?
Biosphere X would be the next generation of ground-based Biospheres. You may consider the original Biosphere 2[5] as the first prototype. As an initial SWAG, it was marginally successful. As the design basis of a working space farm, it is nowhere close.
Image of the iconic Biosphere 2 experiment that attempted two missions, between 1991 and 1994, sealing a team of nine and seven Biospherians, respectively, inside the glass enclosure. The facility is now used for basic research to support the development of computer models that simulate the biological, physical and chemical processes to predict ecosystem stability. Credits: Biosphere 2 / University of Arizona
Biosphere Y will be placed in Equatorial Low Earth Orbit (ELEO) and will be based on the best iteration of Biosphere X.
Biosphere Z will be a radiation hardened version of Biosphere Y for deep space operations.
Key Metrics:
People per acre is an important metric. Knowing how many people are going to be on a space station or spaceship will imply the size of the farming operations required. [6]
Labor per acre is important. It determines how many farm workers are needed to feed the space population (assuming there will be no automation of farm operations). Note: every American farmer feeds about 100 people. Obviously, if it takes 11 farmers to support 10 people in the biosphere, that is a failure. If it takes 2 farmers to support 10 people that implies that 8 workers are available to work on important space projects. Like building the next biosphere that is bigger and better.
Cost per acre will be the major cost of supporting a person in space. There will be a huge effort to reduce the cost of space farmland.
Water per acre required to grow the crops. Since there is a metric for people per acre, the water per acre would include the water in the sewage system. I would think the water for fish farming would be separate or an option.
Soil per acre is literally the amount of dirt needed in tons. This gets fun. Will Biosphere X use hydroponics, aeroponics, light weight dirt, or high quality top-soil? It could be just standard sandy loam. The quality of the soil will have a big impact on what crops can be grown, which in turn, has a big impact on People per acre.
Watts per acre is the power required to operate a farm. Another major cost of food grown in space. Direct sunlight should be very cheap via windows, at least for biospheres in ELEO. In deep space far removed from the protection of Earth’s magnetic field, radiation would pose a problem for windows unless some sort of angled mirror configuration could be used to reflect sunlight adjacently. Electricity from solar panels has been proven by ISS. Power from a small modular nuclear reactors might be a great backup power for the first orbiting biosphere. Note, diesel fuel would be extremely expensive and emissions would cause pollution to the biosphere in space; that implies, farming would be done using electrical equipment.
Improvements based on the Biosphere 2 experience to make a successful Biosphere X:
Updated computers for: better design, data collection, environmental control systems, subsystem module metrics, communication.
Humans: I suggest 2 men & 2 women and work up from there.
Remote ground support: start big and reduce as fast as possible, goal = zero.
Testing Biosphere X:
Can a team live in the biosphere for two years? (See Biosphere 2 test which was 2 years, i.e. a round trip to Mars and back) How much food was produced? Debug the biosphere. Make upgrades and repeat the tests. Calculate Mean Time to Failure (MTTF), Mean Time to Repair (MTTR), system flexibility, cost of operations, farming metrics (see above). etc.
With enough debugging, Biosphere X will become a comfortable habitat for humans of all ages. This will include old people, children, and perhaps babies. I think a few babies should be born in a Biosphere X (e.g. a few dozen?) before proceeding to Biosphere Y. Obviously, it may be challenging to find motivated families willing to make the generational commitment for long term testing required to realize this noble goal of space settlement. Alternatively, testing of Biosphere X could be simplified and shortened by skipping having babies, deferring this step to the next stage.
Biosphere Y potential configuration:
Once a reasonably well designed Biosphere X has been tested it will be time to build a Biosphere Y. This will require figuring out how to launch and build the first one – not easily done! Let’s posit a reasonably feasible design using orbital spacecraft on the near-term horizon namely, the SpaceX Starship. Using nine upper stages with some modifications to provide spin gravity, sufficient volume could be placed in ELEO for a one acre space farm. Here’s one idea on what it would look like:
A central hub which we will call the 0G module will be composed of three Starship upper stages. Since they would not be returning to Earth, they would not need heat shield tiles, the aerodynamic steerage flaps, nor the three landing rockets. Also, there would not be a need for reserve fuel for landing. These weight reductions would allow the engineers to expand Starship and/or make more built-in structure and/or carry more startup supplies.
We will assume the current length of 165 feet with a 30 foot diameter. Three units placed nose-to-tail make 495 feet. But internally there would be 3 workspaces per unit: Oxygen tank, methane tank, and crew cabin. Times three units makes 9 chambers for zero gravity research.
The three units are connected forward and aft by docking hatches. Since the return to Earth engines have been deleted, the header tanks in the nose of Starship (the purpose of which is to offset the weight of the engines) would be eliminated allowing a docking port to be installed in front. In addition, with the 3 landing engines eliminated, there should be room for a tail end docking port. This will allow crew to move between the three Starship units in the 0G hub.
An aside: I am assuming that the nose of the station is always pointing towards the sun. The header tanks in the nose of the first unit could be retained and filled with water to provide radiation shielding to block solar particle events for the trailing units.
The 0G-units will need access ports on each of their sides to allow a pressurized access and structural support tube extending out to the 1G-units located at 100 meters on either side of the hub. This distance is calculated using Theodore W. Hall’s SpinCalc artificial gravity calculator with a spin rate of 3 rpm. There would be three access tubes extending out to connect to each of the 3 Starship 1G units. I assume the standard Starship has an access door which can be modified to connect to the tube.
Conceptual illustration of a possible configuration of an initial Biosphere Y in LEO using modified SpaceX Starship upper stages docked nose to tail. The station spins at 3 rpm around the central 0G hub with the outer modules providing 1G artificial gravity and enough volume for an acre of space farm. Credits – Starship images: SpaceX. Earth image: NASA
One or more standard Starships would deliver supplies and construction materials. They would also collect the three Raptor engines from each modified unit (36 in total) for return to Earth.
I note that the engineering modifications, methods and funding for operations in space to construct Biosphere Y have yet to be determined. However, applying a SWAG for launching the primary hardware to LEO:
This would require 18 starship missions. Using Brian Wang’s estimates of $37M per Starship[21] we get the following cost:
9 Starships times $37M per starship = $333M
18 Starship launches times $10M per launch = $180M
Total SWAG cost: $513M
What’s on the inside?
As mentioned previously, the interior of Biosphere Y will be a Wet Workshop utilizing the empty oxygen and methane tanks in addition to the payload bay volume (roughly 60ft + 39ft + 56ft long, respectively, based on estimates from Wikipedia), for a total length of 155 feet by 30 feet wide for each individual Starship unit. With six 1G Starship units this amounts to about 657, 000 cubic feet of usable volume for our space farm experiencing normal gravity and its associated support equipment (half that for the 0G hub).
Note: Biosphere Y is designed to be placed in Equatorial Low Earth Orbit (ELEO). This orbit is below the Van Allen belts where solar particle events and galactic cosmic ray radiation are reasonably low due to Earth’s protective magnetic field.
Since the first Biosphere Y will spin to produce 1G, eventually experiments will need to be performed to determine the complete Gravity Prescription[12, 13]: 1/2g, 1/3g, 1/6g and maybe lower. You would think this would be required before trying to establish a permanent colony on the Moon and/or Mars in which children will be born. This will probably require several iterations of Biosphere Y space stations to fine tune the optimum mix of plants, animals, and bio-systems.
What other things can be done with a Biosphere Y?
Replace International Space Station
Astronomy
Space Force bases in orbit
Repair satellites
Fueling station
De-orbit space junk
Assemble much larger satellites from kits (cuts cost)
Lunar material processing station
Families including children and babies[13] in space
Biosphere Z:
Once Biosphere Y is proven, it is ready to be radiation hardened to make a Biosphere Z. I assume the radiation hardening material would come from lunar regolith. It is much cheaper than launching a lot of radiation shielding off Earth.
Biosphere Z will be able to do everything that Biosphere Y can do – just further away from Earth.
After an appropriate shake-down cruise (2 years orbiting the Moon, Lagrange 1, and/or Lagrange 2), a Biosphere Z design should be ready to go to Mars. Note several problems will have been solved to ensure positive outcomes for such a journey: • What does the crew do while going to Mars — farming. • Building Mars modules to land on Mars • The crew has been trained and tested for long endurance flights • Other typical Biosphere Y, Z activities
Biosphere S — Major Milestone:
Eventually a biosphere will be manufactured using only space material, thus the designation Biosphere S. Regolith can be processed into dirt. Most metals will come from the Moon and/or Mars surface material. Oxygen is a byproduct of smelting the metals. Carbon and Oxygen can come from the Martian atmosphere. Water can be obtained from ice in permanently shadowed regions at the Moon’s poles or from water bearing asteroids. The first Biosphere S units will probably get Nitrogen from Mars. Later units could get nitrogen, water, and carbon-dioxide from Venus[14]. From the Moon we get KREEP[15]. (potassium, Rare Earth Elements, and Phosphorus) found by the Lunar Prospector mission.
People, plants, livestock, microbes, etc. will come from other Biospheres.
Electronics will probably still come from Earth, at least initially, until technology and infrastructure matures to enable manufacturing of integrated circuits in space.
Artist’s depiction of an agricultural section of Biosphere S, which could be of the Stanford Torus design built mostly from space resources. Credits: Bryan Versteeg / Spacehabs.com
At this point, humans will have become “A space faring species”
In a century, the number of Biospheres created will go from zero to one hundred per year.
Marshall’s Conjecture:
“400 years after the first baby is born in space, there will be more people living in space than on Earth.” After all, from the time of the signing of The Mayflower Compact to present day is about 400 years and we have 300+ million US citizens vs. the United Kingdom’x 68 million.
The explosion of life:
On Earth there are relationships between the number of humans, the number of support animals and plants. There are currently 8 billion people on Earth and about 1 billion head of cattle. I estimate that there are 100 billion chickens, a half billion pigs, etc.
As the number of Biospheres increases in number, so will the number of people, and the number of support plants and animals. To state it succinctly, there will be an explosion of life in space.
So how many Biosphere S colonies can we build?
Let us assume that they will be spread out evenly in the solar “Goldilocks Zone” (GZ). Creating a spreadsheet with Inputs: inside radius (IR), outside radius (OR) and minimum spacing; Output: Biosphere slot count.
Using: IR of 80,000,000 miles, OR of 120,000,000 miles, (120% to 33% Earth light intensity[16], respectively) and spacing of 1000 miles between Biospheres (both on an orbit and between orbits) you get: 40,000 orbits with the inner orbit having 502,655 slots and the outer orbit having 753,982 slots. This works out to over 25 billion slots for Biospheres to fill this region. Assuming 40 people per Biosphere S implies a space population of over a trillion people. And that is only within the GZ. With ever advancing technology like nuclear power enabling settlement further from the sun, there is no reason that humans can’t expand their reach and numbers throughout the solar system, implying many trillions more.
Can we build that many Biospheres?
Let us assume each Biosphere S has a mass of one million tons (10 times larger than a nuclear powered aircraft carrier[17]) That implies 25.1×1015 tons of metal for all of them. 16 Psche’s mass is estimated at 2.29×1016 tons[18]. There are the larger asteroids, e.g. Ceres (9.4×1017tons), Pallas, Juno, Vesta (2.5×1017 tons) and several others. Assuming the Moon (7.342×1019 tons) is reserved for near Earth use. If the asteroids are not enough, there are the moons of Mars and Jupiter. The other needed elements are readily available throughout the solar system, e.g. nitrogen from Venus, water from Europa, dirt from everywhere, so…
YES! My guess is that it will take 100,000 years to fill the GZ assuming a construction rate of about 250,000 Biospheres per year. That implies an expansion of the population by about 2 million people a year ( I acknowledge these estimates don’t take into account technological advances which will undoubtedly occur over such long stretches of time that may lead to drastically different outcomes. Remember! Its a SWAG!)
Is this Space Manifest Destiny? Is it similar to the Manifest Destiny[19] in America from 1840 to 1900? In my opinion, yes! But this is a very high-tech version of Manifest Destiny. The bottom line assumption is that the Goldilocks Zone is empty — therefore — we must go fill it! Just like the frontiersman of the 1800s.
The First Commandment:
This gives a new interpretation of the phrase from the Book of Genesis,
“Go forth, be fruitful and multiply“[20].
Not only are we people required to have children; but we are required to expand life in many forms wherever we go. For secular readers, this may be interpreted as the natural evolution of life to thrive in new ecosystems beyond Earth. Therefore, the big expansion of life will be in space.
It all starts with Biospheres X, Y, and Z optimized for farming in space
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When considering humanity’s expansion out into the solar system, look at the concepts put forward above and ask: “Is this proposal missing a key step or two in the development of biospheres in space?”
Editor’s Note: Marshall appeared on The Space Show on August 27 to talk about his space farming vision. You can listen to the archived episode here.
G.K. O’Neill, The High Frontier, 1976, p. 71 – based on Earth-base agriculture – 25 People/Acre; p72 – Optimized for space settlement (i.e. predictable, controlled climate) – 53 People/Acre.
Artist rendering of a family living in a rotating free-space settlement based on the Kalpana Two design, with a length of 110m and diameter of 125m. Credits: Bryan Versteeg / Spacehabs.com
This post summarizes my upcoming talk for the Living in Space Track at ISDC 2024 taking place in Los Angeles May 23 – 26. The presentation is a distillation of several posts on the Gravity Prescription about which I’ve written over the years.
Lets start with a couple of basic definitions. First, what exactly is a space settlement? The National Space Society defined the term with much detail in an explainer by Dale L. Skran back in 2019. I’ve extracted this excerpt with bolded emphasis added:
Space Settlement is defined as:
“… a habitation in space or on a celestial body where families live on a permanent basis, and that engages in commercial activity which enables the settlement to grow over time, with the goal of becoming economically and biologically self-sustaining …”
The point here is that people will want to have children wherever their families put down roots in space communities. Yes, a “settlement” could be permanent and perhaps inhabited by adults that live out the rest of there lives there, such as in a retirement community. But these are not biologically self-sustaining in the sense that settlers have offspring that are conceived, born and raised there living out healthy lives over multiple generations.
Next we should explain what is meant by the Gravity Prescription (GRx). First coined by Dr. Jim Logan, the term refers to the minimum “dosing” of gravity (level and duration of exposure) to enable healthy conception, gestation, birth and normal, viable development to 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 pregnancy (conception through birth), early child development, and adulthood. The focus of this discussion is primarily on the GRx for reproduction.
We should also posit some basic assumptions. First, with the exception of the GRx, all challenges expected for establishment of deep space settlements can be solved with engineering solutions (e.g. radiation protection, life support, power generation, etc…). The one factor that cannot be easily changed impacting human physiology after millions of year of evolution on Earth is gravity. We may find it difficult or even impossible to stay “healthy enough” under hypogravity conditions on the Moon or Mars, assuming all other human factors are dealt with in habitat design.
Lets dive into what we know and don’t know about the GRx. Several decades of human spaceflight have produced an abundance of data on the deleterious effects of microgravity on human physiology, not the least of which are serious reduction in bone and muscle mass, ocular changes, and weakening of the immune system – there are many more. So we know microgravity is not good for human health after long stays. Clearly, having babies under these conditions would not be ethical or conducive for long term settlement.
The first studies carried out on mammalian reproduction in microgravity took place in the early 1990s aboard the Space Shuttle in a couple of experiments on STS-66 and STS-70. 10 pregnant rats were launched at midpregnancy (9 days and 11 days, respectively) on each flight and landed close to the (22 day) term. The rat pups were born 2 days after landing and histology of their brain tissue found spaceflight induced abnormalities in brain development in 70% of the offspring.
It was not until 2017 that the first mammalian study of rodents with artificial gravity was performed on the ISS. Although not focused on reproduction, the Japan Aerospace Exploration Agency (JAXA) performed a mouse experiment in their Multiple Artificial-gravity Research System (MARS) centrifuge comparing the impact of microgravity to 1g of spin gravity. The results provided the first experimental evidence that mice exposed to 1g of artificial gravity maintained the same bone density and muscle weight as mice in a ground control group while those in microgravity had significant reductions.
Diagram depicting an overview of the first JAXA Mouse Project in the MARS centrifuge with photos of the experiment on the ISS. Credits: Dai Shiba et al. / Nature. http://creativecommons.org/licenses/by/4.0/
In 2019 JAXA carried out a similar study in the MARS centrifuge adding lunar gravity levels to the mix. This study found that there were some benefits to the mice exposed to 1/6g in that Moon gravity helped mitigate muscle atrophy, but it did not prevent changes in muscle fiber or gene expression.
Just last year, a team led by Dr. Mary Bouxsein at Harvard Medical School conducted another adult mouse study on the MARS centrifuge comparing microgravity, .33g, .67g and 1g. They found that hind quarter muscle strength increased commensurate with the level artificial gravity concluding, not surprisingly, that spaceflight induced atrophy can be mitigated with centrifucation. The results were reported at the American Society for Gravitational and Space Research last November.
Returning to mammalian reproduction in space, an interesting result was reported last year in the journal Cell from an experiment by Japanese scientists at the University of Yamanashi carried out on the ISS in 2019. The team, headed up by Teruhiko Wakayama, devised a way to freeze mouse embryos post conception and launch them into space where they were thawed by astronauts and allowed to develop in microgravity. Control samples were cultured in 1g artificial gravity on the ISS and Earth normal gravity on the ground. The mouse embryos developed into blastocysts and showed evidence of cell differentiation/gene expression in microgravity after 4 days. The researchers claimed that the results indicated that “Mammals can thrive in space”. This conclusion really can’t be substantiated without further research.
Which brings us to several unknowns about reproduction in space. SSP has explored this topic in depth through an interview with Alex Layendecker, Director of the Astrosexological Research Institute. Yet to be studied in depth is (a) conception, including proper transport of a zygote through the fallopian tube to implantation in the uterus. Less gravity may increase the likelihood of ectopic pregnancy which is fatal for the fetus and could endanger the life of the mother; (b) full gestation through all stages of embryo development to birth; and (c) early child development and maturation to adulthood in hypogravity. All these stages of mammalian reproduction need to be validated through ethical clinical studies on rodents progressing to higher primate animal models before humans can know if having children in lower gravity conditions on the Moon or Mars will be healthy and sustainable over multiple generations.
AI generated image of an expectant mother with her developing fetus in Earth orbit after mammalian reproduction has been validated via higher animal models through all stages of pregnancy for a safe level of gravity. An appropriate level of radiation shielding would also be required and is not shown in this illustration. Credit: DALL-E-3
Some space advocates for communities on the Moon or Mars have downplayed the importance of determining the GRx for reproduction with the logic that a fetus in a woman’s uterus on Earth is in neutral buoyancy and thus is essentially weightless. Therefore, why does gravity matter? I discussed this question with Dr. Layendecker and he had the following observations paraphrased here: True, gravity may have less of an impact in the first trimester. But on the cellular level, cytoskeletal development and proper formation/organization of cells may be impacted from conception to birth. Gravity helps orient the baby for delivery in the last trimester and keeps the mother’s uterine muscles strong for contractions/movement of the baby through the birth canal. There are many unknowns on what level of gravity is sufficient for normal development from conception to adulthood.
Why does all this matter? Ethically determining the right level of gravity for healthy reproduction and child development will inform where families can safely settle space. The available surface gravities of bodies where we can establish communities in space cluster near Earth, Mars and Moon levels. These are our only GRx options on solar system bodies.
Gravity level clustering of solar system bodies available for space settlement. Credit: Joe Carroll
The problem is that we don’t yet know whether we can remain healthy enough on bodies with gravity equivalent to that on the Moon or Mars, so we can’t select realistic human destinations or formulate detailed plans until we acquire this knowledge. Of course we can always build rotating settlements in free space with artificial gravity equivalent to that on Earth. Understanding the importance of the GRx and determining its value could change the strategy of space development in terms of both engineering and policy decisions. The longer we delay, the higher the opportunity costs in terms of lost time from failure to act.
What are these opportunity cost lost opportunities? Clearly, at the top of Elon Musk’s list is “Plan B” for humanity, i.e. a second home in case of cataclysmic disaster such as climate change, nuclear war, etc. This drives his sense of urgency. From Gerard K. O’Neill’s vision in The High Frontier, virtually unlimited resources in space could end hunger and poverty, provide high quality living space for rapidly growing populations, achieve population control without war, famine, or dictatorships. And finally, increase freedom and the range of options for all people.
If humans can’t have babies in less than Earth’s gravity then the Moon and Mars may be a bust for long term (biologically sustainable) space settlement. There will be no biologically sustainable cities with millions of people on other worlds unless they can raise families there.
Spin gravity rotating space settlements providing 1g artificial gravity may be the only alternative. If Elon Musk knew that the people he wants to send to Mars can’t have children there, would he change his plans for a self-sustaining colony on that planet? Having and raising children is obviously important to him. As Walter Isaacson wrote in his recent biography of Musk, “He feared that declining birthrates were a threat to the long-term survival of human consciousness.”
So how could he determine the GRx quickly? One solution would be to fund a partial gravity facility in low Earth orbit to run ethical experiments on mammalian reproduction in hypogravity. Joe Carroll has been refining a proposal for such a facility, a dual dumbbell Moon/Mars low gravity laboratory which SSP has covered, that could also be marketed as a tourist destination. Spinning at 1.5 rpm, the station would be constructed from a combination of Starship payload-sized habitats tethered by airbeams allowing shirt sleeve access to different gravity levels. Visitors would be ferried to the facility in Dragon capsules and could experience 3 gravity levels with various tourist attractions. The concept would be faster, cheaper, safer and better than establishing equivalent bases on the Moon or Mars to quickly learn about the GRx. The facility would be tended by crews at both ends that live & collect health data for up to a year or more. And of course, ethical experiments on the GRx for mammalian reproduction would be carried out, first on rodents and then progressing to higher primates if successful.
Left: Conceptual illustration depicting a LEO Moon-Mars dumbbell partial gravity facility constructed from Starship payload-sized habitats tethered by airbeams and serviced by Dragon capsules. Rectangular solar arrays deploy by hanging at either end as spin is initiated via thrusters at Mars module. Center: Image of an inflated airbeam demonstration. Right: diagram of an airbeam stowed for transport and after deployment. Credit: Joe Carroll
What if these experiments determine that having children in lower gravity is not possible and our only path forward are free-space rotating settlements? Physics and human physiology require that they be large enough for settlers to tolerate a 1g spin rate to prevent disorientation. As originally envisioned by O’Neill, the diameter of his Island One space settlement would be about 500 meters.
Conceptual illustration of an Island One space settlement. The living space sphere is sized at about 500m in diameter. Credits: Rick Guidice / NASA
As originally proposed, these settlements would be located outside the Earth’s magnetic field at the L5 Earth-Moon Lagrange Point necessitating that they be shielded with enormous amounts of lunar regolith to protect occupants from radiation. Their construction requires significant technology development and infrastructure (e.g. mass drivers on the Moon, automated assembly in space, advances in robotics, power sources, etc…). Much of this will eventually be done anyway as space development progresses…however, knowing the GRx (if it is equal to 1g) may foster a sense of urgency.
Some may take the alternative viewpoint that if we know that Earth’s gravity works just fine we could proceed directly to free-space settlements if we could overcome the mass problem. This is the approach Al Globus and Tom Marotta took in their book The High Frontier: An Easier Way with Kalpana One, a 450m diameter cylindrical rotating free-space settlement located in equatorial low Earth orbit (ELEO) protected by our planet’s magnetic field, thereby reducing the mass significantly because there would be far less need for heavy radiation shielding.
Artist impression of Kalpana One rotating free-space settlement located in equatorial low Earth orbit. Credits: Bryan Versteeg / Spacehabs.com
Artist rendering of the inside of a rotating free-space settlement based on the Kalpana Two design, with a length of 110m and diameter of 125m. Credits: Bryan Versteeg / Spacehabs.com
Even though these communities would be lower mass, they will still require significant increases in launch rates to place the needed materials in LEO, especially near the equator. Offshore spaceports, like those under development by The Spaceport Company, could play a significant role in this infrastructure. Legislation providing financial incentives to municipalities to build spaceports would be helpful, such as The Secure U.S. Leadership in Space Act of 2024 introduced in Congress last month. The new law (not yet taken up in the Senate) would amend the IRS Code to allow spaceports to issue tax-exempt Muni bonds for infrastructure improvements.
Wouldn’t orbital debris present a hazard for settlements in ELEO? Definitely yes, and the National Space Society is shaping policy in this area. The best approach is to emphasize “light touch” regulatory reform on salvage rights, with protection and indemnity of the space industry to encourage recycling and debris removal. Joe Carroll has suggested a market-based approach that would impose parking fees for high value orbits, which would fund a bounty system for debris removal. This system would incentivize companies like CisLunar Industries, Neumann Space and Benchmark Space Systems, firms that are developing space-based processes to recycle orbital debris into useful commodities such as fuel and structural components.
Further down the road in technology development and deeper into space, advances in artificial intelligence and robotics will enable autonomous conversion of asteroids into rotating space settlements, as described by David Jensen in a paper uploaded to arXiv last year. This approach significantly reduces launch costs by leveraging in situ resource utilization. Initially, small numbers of “seed” tool maker robots are launched to a target asteroid along with supplemental “vitamins” of components like microprocessors that cannot be easily fabricated until technology progresses, to complete the machines. These robotic replicators use asteroid materials to make copies of themselves and other structural materials eventually building out a rotating space settlement. As the technology improves, the machines eventually become fully self-replicating, no longer requiring supplemental shipments from Earth.
Artist impression of a rotating space settlement constructed from asteroid materials. Credits: Bryan Versteeg, spacehabs.com
Leveraging AI to enable robots to build space settlements removes humans from the loop initially, eliminating risk to their health from exposure to radiation and microgravity. Send it the robot home builders – families then safely move in later. There are virtually unlimited supplies in the asteroid belt to provide feedstock to construct thousands of such communities.
Artist impression of the interior of Stanford Torus free-space settlement. Advances in artificial intelligence and robotics will enable autonomous self replicating machines that could build thousands of such communities from asteroid material. Credits: Don Davis / NASA
If rotating space settlements with Earth-normal gravity become the preferred choice for off-Earth communities, where would be the best location, the prime real estate of the solar system? Jim Logan has identified the perfect place with his Essential Seven Settlement Criteria.
Low Delta-V – enabling easy access with a minimum of energy
Lots of RESOURCES … obviously!
Little or No GRAVITY WELL – half way to anywhere in the solar system
At or Near Earth Normal GRAVITY for People, Plants and Animals - like what evolved on Earth
Natural Passive 24/7 RADIATION Protection – for healthy living
Permit Large Redundant Ecosystem(s) – for sustenance and life support
Staging Area for Exploration and Expansion (including frequent, recurrent launch windows)
Using this criteria, Logan identified Deimos, the outermost moon of Mars, as the ideal location. As discussed above, AI and robotic mining technology improvements will enable autonomous boring machines to drill a 15km long core through this body with a diameter around 500 meters – sized for an Island One space settlement to fit perfectly.
Conceptual illustration of a 500 meter wide by 15km long core bored through Deimos. Credit: Jim Logan
In fact, 11 Island One space colonies (minus the mirrors) strung end to end through this tunnel would provide sea level radiation protection and Earth normal artificial gravity for thousands of healthy settlers.
Left: Artist impression of an Island One space settlement. Credits: Rick Guidice / NASA. Right: To scale depiction of 11 Island One space settlements strung end-to-end in a cored out tunnel through Deimos providing sea level radiation protection and Earth normal artificial gravity. Credit: Jim Logan
In conclusion, the GRx for reproduction will inform where biologically self-sustaining healthy communities can be established in space. If we find that the GRx is equal to Earth’s normal level, free-space settlements with artificial gravity will be the safest and healthiness solution for humans to live and thrive throughout the solar system. The sooner we determined the GRx the better, for current plans for settling the Moon or Mars may need to be altered to consider rotating space colonies, which will require significant infrastructure development and regulatory reform. Alternatively, since we know Earth’s gravity works just fine, we may choose to skip determination of the GRx and start small with Kalpana in low Earth orbit. Eventually, artificial intelligence will enable safe, autonomous self-assembly of space settlements from asteroids. The interior of Deimos would be the perfect place to build safe, healthy, biologically self-sustaining space settlements for thousands of families to raise their children, establishing a beachhead from which to explore the rest of the solar system and preserve the light of human consciousness.
Update June 3, 2024: Here is a recording of my presentation on this topic at ISDC 2024.
A fictional depiction of an ore ship servicing mining operations on an asteroid. Credits: DALL∙E 3
The clean energy transition away from fossil fuels promoted by the Biden Administration and other world governments will require significant increases in mining of critical materials for clean energy technology. To support the huge projected growth in solar, wind, and battery technologies over the next few decades, demand for key minerals such as lithium, graphite, nickel and rare-earth metals will balloon significantly according a 2021 report by the International Energy Agency: The Role of Critical Minerals in Clean Energy Transitions. When compared to current supply levels, sourcing of these materials will need to grow by several hundred percent, with lithium in particular predicted to explode by 4,200% to keep pace with the needed battery production for EVs and other energy storage systems. There is insufficient mining capability in the world today to meet this demand, and if capacity were ramped up to these levels, there would be serious environmental and economic consequences. If we ignore other promising alternatives (which SSP does not advocate) such as ramping up licensing of new nuclear fission power plants and funding development of fusion energy or space solar power, what can be done?
In the journal PNAS, a research article makes the case for why mining in space may be a viable solution and help lay the foundation for sustainable growth on Earth. The author’s* objective for the paper was to perform a trade study on the economic outcomes associated with the environmental and social impacts of terrestrial mining compared to the costs of sourcing from asteroids, focusing primarily on metals required for the clean energy technologies such as copper, nickel cobalt and lithium. The methodology of the paper used a neoclassical Ramsey economic model to predict economic growth under those two scenarios. The study quantifies the economic benefits and projected timelines of mining in space for increasing metal use in clean technologies on Earth for the rest of this century and concludes that the reduction in costs due to environmental damage to our planet’s biosphere may be worth the investment in asteroid mining.
Along similar lines another economic analysis by Matthew Weinzierl makes the potential case for an expanding space economy as a solution to secular stagnation, that condition that some economists fear is happening in the US: a chronic lack of demand as if the economy is operating below capacity even when it appears to be booming. Weinzierl says “In simple terms, secular stagnation is the idea that a sluggish outlook for the economy causes people to save more and firms to invest less, and if interest rates cannot fall enough to spur investment (perhaps because of the sluggish outlook), the lack of investment makes the low-growth prospects all the more likely to be fulfilled, initiating a vicious cycle.” How could space development help prevent this problem? Space settlement, i.e. world building, would unlock abundant resources in the solar system to sustain not only capital investment in expanding economic activity, but robust population growth without limits.
An interesting perspective on off-Earth mining as a commercial engine driving a space economy, with a focus on a thriving Martian colony, was proposed a few years ago in a paper by Robert Shishko and others. The study examined the role of space mining in an economy based on mineral extraction, ice/water, and other resources obtained in situ on the Red Planet. The analysis provided a better understanding of the market conditions and technology requirements for that economy to grow and prosper. This approach would definitely benefit from the recent discovery of massive amounts of subsurface water ice under the Medusae Fossae Formation near the equator of Mars.
Mars Express radar image of subsurface water ice beneath the Medusae Fossae Formation near the equator of Mars. Credits: ESA
If an economic case can be made for space mining and funding secured, it will be dependent on the location of the most profitable and accessible space resources in terms of energy and abundance of useful material. Where will this motherlode for space mining be? SSP has covered this debate.
One of the companies on this frontier is UK based Asteroid Mining Corporation which has the goal of becoming the first profitable space resources business. The startup is working on an autonomous robotic platform call Space Capable Asteroid Robot Explorer with a roadmap that plans for revenue payout at each milestone with eventual return of asteroid resources in the mid-2030s.
Asteroid Mining Corporation’s Space Capable Asteroid Robotic Explorer. Credits: Asteroid Mining Corporation.
And of course readers of SSP are familiar with AstroForge, the company focusing on returning precious metals to Earth from asteroids.
Artist impression of a rotating space settlement under construction using material from an asteroid.Credits: Bryan Versteeg, spacehabs.com
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* Authors of research article in PMAS Mining in Space Could Spur Sustainable Growth: Maxwell Fleming, Ian Lange, and Sayeh Shojaeinia of the Colorado School of Mines; Martin Stuermer of the International Monetary Fund.
An engineer pondering chemical processes for use in space learned in an advanced postgraduate course in Astrochemical Engineering. Credits: DALL∙E 3
In a paper in the journal Sustainability a global team of researchers has created a two year curriculum to train the next generation of engineers who will design the chemical processes for the new industrial revolution expected to unfold on the high frontier in the next few decades.
Current chemical engineering (ChE) training is not adequate to prepare the next generation of leaders who will guide humanity through the utilization of material resources in space as we expand out into the solar system.
Astrochemical Engineering is a potential new field of study that will adapt ChE to extraterrestrial environments for in situ resource utilization (ISRU) on the Moon, Mars and in the Asteroid Belt, as well as for in-space operations. The body of knowledge suggested in this paper, culminating in Master of Science degree, will provide training to inform the design ISRU equipment, life support systems, the recycling of wastes, and chemical processes adapted for the unique environments of microgravity and space radiation, all under extreme mass and power constraints.
The first year of the program focuses on theory and fundamentals with a core module teaching the physical science of celestial bodies of the solar system, low gravity processes, cryochemistry (extremely low temperature chemistry), and of particular interest, circular systems as applied to environmental control and life support systems (ECLSS) to recycle materials as much as possible. Students have the option to specialize in either process engineering or a more general concentration in space science.
For the process engineering option in year one, students will learn how materials and fluids behave in the extreme cold of space. This will include the types of equipment needed for processes in a vacuum environment including microreactors and heat exchangers, as well as methods for separation and mixing of raw materials.
In the space science specialization, year one will include production of energy and its utilization in space. Applications include solar energy capture and conversion to electricity, nuclear fission/fusion energy, artificial photosynthesis, and the role of energy in life support systems.
In the second year, students learn basic chemical processes for ISRU on other worlds. Processes such as electrolysis for cracking hydrogen and oxygen from water; and the reactions Sabatier, Fischer-Tropsch and Haber-Bosche for production of useful materials.
The second year process engineering specialization focuses on ISRU on the Moon with ice mining, processing regolith and fluid transport under vacuum conditions. Propulsion systems are also covered including methane/oxygen engines, hydrogen logistics, cryogenic propellent handling in space and both nuclear thermal and electric propulsion. Space science specialization in year two covers life support systems and space agriculture.
A design project is required at the end of each year to demonstrate comprehension of the concepts learned in the curriculum, and is split between an individual report and a group project.
