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A vision for industry on the Moon

Credits: Michael Nayak / Air University Press

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

A Strategic Vision Beyond Unsustainable Symbolism

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

The Role of LunA-10

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

Four Economic Ages of the Moon

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

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

Pillars of Commercial Lunar Infrastructure

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

Power and Thermal as a Service

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

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

Logistics: The Lunar Rail Network

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

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

Mining and the Metal Ecosystem

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

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

Orbital Infrastructure: Cislunar Supply Hubs

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

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

Economic and Legal Enablers

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

Property Rights and Law

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

The Commodities Exchange and Board of Trade

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

Interoperability via the LOGIC Consortium

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

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

The Path to 2035

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

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

Execution of the EO in Alignment with the Field Guide

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

Action 1: Immediate Transition to Lunar Commodity Contracts

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

Action 2: Deploy the Lunar Rail Pilot Program

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

Action 3: Codify the Lunar Board of Trade

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

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

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

Conclusion

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

Artist rendering of GRU Space’s hotel on the Moon. Credit: GRU Space
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Neumann Drive successfully tested in space

Company images of a Neumann Drive at upper left with it’s plasma discharge produced in the lab at upper right overlayed above the Earth from space. Credits: Neumann Space / NASA

Neumann Space has announced completion of initial on-orbit tests of its innovative electric propulsion system, the first of its kind utilizing solid metal as propellent to fuel a cathodic arc discharge to generate thrust via plasma exhaust. The commissioning campaign for the system confirmed that the electronics worked properly and that the thruster fired. Next up: following last December’s launch of the company’s second experiment in space, an engineering demonstration later this year will test that the propulsion system can change the orbit of a satellite.

Neumann Space has already lined up both a customer and a potential space-based source of fuel through a partnership with CisLunar Industries. In this symbiotic relationship, CisLunar will utilize Neumann’s thruster to propel their servicing vehicle that hunts down chunks of metallic space debris which will be captured and delivered to a salvage platform to be recycled into metal propellent via CisLunar’s Modular Space Foundry (previously called Micro Space Foundry). The servicing vehicle can then refuel itself to proceed to its next target. SSP reported previously on this propulsion ecosystem which could literally turn trash into treasure while cleaning up orbital debris.

Conceptional illustration of propulsion ecosystem based on CisLunar Industries Modular Space Foundry process for recycling orbital debris. Credits: CisLunar Industries

The orbital debris issue not only poses a serious threat to human spaceflight in Earth orbit, unless policies and standard practices are implemented to mitigate the issue, remote sensing, climate monitoring, weather forecasting and all commercial activities in space could be at risk, not to mention long term sustainable space settlement. The on-orbit recycling partnership between Neumann Space and CisLunar Industries will help implement the remediation pillar of the National Orbital Debris Mitigation Plan promulgated in 2022 by the White House Office of Science and Technology Policy.

In other news, CisLunar Industries was one of fourteen other companies selected by DARPA for its LunA-10 program, a lunar architecture study that will define commercial activities in an integrated infrastructure for lunar development over the next 10 years. CisLunar will collaborate with industry partners to develop what they call METAL, a framework for Material Extraction, Treatment, Assembly & Logistics in a lunar economy based on in situ resource utilization.

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The prospects for mining precious metals and structural materials from asteroids

Artist impression of an asteroid smelting operation. Credits: Bryan Versteeg / spacehabs.com

When humanity migrates out into the solar system we’ll need a variety of elements on the periodic table to build settlements and the infrastructure needed to support them such as solar power satellites. But before that future becomes a reality, there may be a near term market on Earth for precious metals sourced in space as transportation costs come down. There is also the added benefit of moving the mining industry off planet to preserve the environment. Could the asteroid belt provide these materials? Kevin Cannon, assistant professor at the Space Resources Program at the Colorado School of Mines describes the prospects for mining precious metals and building materials for space infrastructure asteroids in a recent paper in Planetary and Space Science. Coauthors on the paper Matt Gialich and Jose Acain, are CEO and CTO, respectively, at the asteroid mining company AstroForge which just came out of stealth mode last year.

The asteroids have accessible mining volume that exceeds that available on the Moon or Mars. This is because only the thin outer crust of these bodies is reachable by excavation, whereas the asteroids are small enough to be totally consumed resulting in higher accessible mining volume.

To-scale accessible mining volume of terrestrial bodies, calculated as the total volume for the asteroids (main belt mass of 2.39 x 1023 kg, mean bulk density of 2000 kg/m3), and as the volume for an outer shell 1.2 km in thickness for the Moon, Mercury, and Mars, equivalent to the deepest open pit mine on Earth. Note the combined volume of the near-Earth asteroids (~5 x 1012 m3) is too small to be visible at this scale. Figure 1 in paper. Credits K.M. Cannon et al.

The authors take a fresh look at available data from meteorite fragments of asteroids. Their analysis found that for Platinum Group Metals (PGMs), the accessible concentrations are higher in asteroids than ores here on Earth making them potentially profitable to transport back for use in commodity markets.

“Asteroids are a promising source of metals in space, and this promise will mostly be unlocked in the main belt where the Accessible Mining Volume of bodies greatly exceeds that of the terrestrial planets and
moons”

PGMs are indispensable in a wide range of industrial, medical, and electronic applications. Some examples of end-use applications include catalysts for the petroleum and auto industries (palladium and platinum), in pacemakers and other medical implants (iridium and platinum), as a stain for fingerprints and DNA (osmium), in the production of nitric acid (rhodium), and in chemicals, such as cleaning liquids, adhesives, and paints (ruthenium).

It has been pointed out by some analysts that flooding markets here on Earth with abundant supplies of PGMs from space will cause prices to plummet, but the advantage of reducing carbon emissions and environmental damage associated with mining activities may make it worth it. The authors also point out that there are probably various uses where PGMs offer advantages in material properties over other metals but are not being used because they are currently too expensive.

Asteroids are rich in other materials such as silicon and aluminum which would be economically more useful for in-space applications. As the authors point out, some companies are already planning for use of metals and manufacturing in space such as Redwire Corporation with their On-Orbit Servicing, Assembly and Manufacturing (OSAM) and Archinaut One, which will attempt to build structural beams in LEO. Another example mentioned in the paper has been covered by SSP: the DARPA NOM4D program with aspirations to develop technologies for manufacturing megawatt-class solar arrays and radio frequency antennas using space materials. Finally, another potential market for aluminum sourced in space is fuel for Neumann Thrusters (although spent upper stage orbital debris may provide nearer term supplies). And of course, silicon will be needed to fabricate photovoltaic cell arrays for space-based solar power.

AstroForge will test their asteroid mining technology on two missions this year. Brokkr-1, a 6U CubeSat just launched on the SpaceX Transporter 7 mission last April, will validate the company’s refinery technology for extracting metals by vaporizing simulated asteroid materials and separating out the constituent components. Brokkr-2 will launch a second spacecraft on a rideshare mission chartered by Intuitive Machines attempting their second Moon landing later this year. Brokkr-2 will hitch a ride and then fly on to a target asteroid located over 35 million km from Earth. The journey is expected to take about 11 months and will fly by the body and continue testing for two years to simulate a roundtrip mission.

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Space development on the Moon, Mars and beyond featured in 2023 NIAC Phase I Grants

Conceptual illustration of an oxygen pipeline located at the lunar south pole. Credits: Peter Curreri

This year’s list of NASA Innovative Advanced Concepts (NIAC) Phase I selections include a few awards that look promising for space development. For wildcatters (or their robotic avatars) drilling for water ice in the permanently shadowed craters at the lunar south pole and cracking it into hydrogen and oxygen, Peter Curreri of Houston, Texas based Lunar Resources, Inc. describes a concept for a pipeline to transport oxygen to where it is needed. Clearly oxygen will be a valuable resource to settlers for breathable air and oxidizer for rocket fuel if it can be sourced on the Moon. The company, whos objective is to develop and commercialize space manufacturing and resources extraction technologies to catalyze the space economy, believes that a lunar oxygen pipeline will “…revolutionize lunar surface operations for the Artemis program and reduce cost and risk!”.

Out at Mars, Congrui Jin from the University of Nebraska, Lincoln wants to augment inflatable habitats with building materials sourced in situ utilizing synthetic biology. Cyanobacteria and fungi will be used as building agents “…to produce abundant biominerals (calcium carbonate) and biopolymers, which will glue Martian regolith into consolidated building blocks. These self-growing building blocks can later be assembled into various structures, such as floors, walls, partitions, and furniture.” Building materials fabricated on site would significantly reduce costs by not having to transport them from Earth.

A couple of innovations are highlighted in this NIAC grant. First, Jin has studied the use of filamentous fungi as a producer of calcium carbonate instead of bacteria, finding that they are superior because they can precipitate large amounts of minerals quickly. Second, the process will be self-growing creating a synthetic lichen system that has the potential to be fully automated.

In addition to building habitats on Mars, Jin envisions duel use of the concept on Earth. In military logistics or post-disaster scenarios where construction is needed in remote, high-risk areas, the “… self-growing technology can be used to bond local waste materials to build shelters.” The process has the added benefit of sequestration of carbon, removing CO2 from the atmosphere helping to mitigate climate change as part of the process of producing biopolymers.

Graphical depiction of biomineralization-enabled self-growing building blocks for habitats on Mars. Credits: Congrui Jin

To reduce transit times to Mars a novel combination of Nuclear Thermal Propulsion (NTP) with Nuclear Electric Propulsion (NEP) is explored by Ryan Gosse of the University of Florida, Gainesville.

Conceptual illustration of a bimodal NTP/NEP rocket with a wave rotor enhancement. Credits: Ryan Gosse

NTP technology is relatively mature as developed under the NERVA program over 50 years ago and covered by SSP previously. NTP, typically used to heat hydrogen fuel as propellant, can deliver higher specific impulse then chemical rockets with attractive thrust levels. NEP can produce even higher specific impulse but has lower thrust. If the two propulsion types could be combined in a bimodal system, high thrust and specific impulse could improve efficiency and transit times. Gosse’s innovation couples the NTP with a wave rotor, a kind of nuclear supercharger that would use the reactor’s heat to compress the reaction mass further, boosting performance. When paired with NEP the efficiency is further enhanced resulting in travel times to Mars on the order of 45 days helping to mitigate the deleterious effects of radiation and microgravity on humans making the trip. This technology could make an attractive follow-on to the NTP rocket partnership just announced between NASA and DARPA.

Finally, an innovative propulsion technology for hurling heavy payloads rapidly to the outer solar system and even into interstellar space is proposed by Artur Davoyan at the University of California, Los Angeles. He will be developing a concept that accelerates a beam of microscopic hypervelocity pellets to 120 kilometers/s with a laser ablation system. The study will investigate a mission architecture that could propel 1 ton payloads to 500 AU in less than 20 years.

Artist depiction of pellet-beam propulsion for fast transit missions to the outer solar system and beyond. Credits: Artur Davoyan

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A brief history of starship pioneering

The photon rocket on an interstellar voyage exploring exoplanets. Credit: © David A. Hardy / www.astroart.org

Eventually we will get to the stars. It may not happen in our lifetime but its going to happen some day. Adam Crowl has provided a nice historical review of the interstellar pioneers from the last century that worked out the physics of the starships that will take us there. He does this in a chapter he wrote for James and Gregory Benford’s ground-breaking anthology Starship Century which was based on the findings of the 100‐Year Starship Symposium seeded by a DARPA solicitation and executed by NASA back in 2011.

Crowl begins the story with the early days of rocketry pioneered by Tsiolkovsky determining the rocket equation and Goddard and others experimenting with liquid fueled rockets. Tsiolkovsky was the first to come up with the idea of a generation starship (sometimes referred to as a worldship) when he realized that existing chemical propellants would be insufficient to fuel a space ship for interstellar travel.

Artist depiction of an interstellar worldship. Credits: Michel Lamontagne / Principium, Issue 32, February 2021

More practical interstellar craft don’t come on the scene until after WWII when advanced propulsion concepts really take off. The possibility of harnessing light to “push” a rocket, feasible because photons carry momentum, first appeared in science fiction. As it turned out, physicists realized that to generate the needed thrust with light pressure would require enormous amounts of energy, the waste heat of which would vaporized the vessel. Nevertheless, the photon rocket was still being discussed as late as 1972 when I first saw the rendering at the top of this post by David Hardy in the book he coauthored with Patrick Moore called Challenge of the Stars. Fast forward to today, Dr. Young K. Bae’s Photonic Laser Thruster shows great promise if it can be scaled up for interstellar travel.

Diagram depicting the layout of the Photonic Laser Thruster. Credits: Young K. Bae, Ph.D.

In the latter half of the last century, as the physics of nuclear energy and laser technology progressed, we see a proliferation of many concepts for star travel, including various forms of fusion rockets, laser sails, antimatter propulsion and my personal favorite, the Bussard ramjet. Conceived by the physicist Robert Bussard in 1960, the ship eliminates the need to carry fuel by collecting hydrogen from the interstellar medium using a magnetic field as a ram scoop and compresses the gas to fusion temperatures to create thrust. Crowl summarizes some of the physical limitations of the original concept and discusses several physicist’s alternative designs to address them.

One concept that didn’t make it into Crowl’s piece was developed recently by Leif Holmlid and Sindre Zeiner-Gundersen. Called the laser induced annihilation drive, it uses a pulsed laser to initiate “antimatter-like” annihilation reactions in hydrogen fuel producing high velocity K meson elementary particles at relativistic speeds to generate thrust.

Diagram of a laser-induced annihilation generator for space propulsion. Credit: Leif Holmlid and Sindre Zeiner-Gundersen, Acta Astronautica 23 May 2020

When I asked Crowl if he had any updates to some of the starship propulsion concepts he sent me an article penned by an unknown author for Medium that came up with another alternative to address the limitations of the original Bussard Ramjet. The author, who goes by the pseudonym “deepfuturetech”, reminds us like Crowl discussed in his piece, that the cross section ( i.e. the probability that a given atomic nucleus or subatomic particle will undergo a nuclear reaction in relation to the species of the incident particle) of the Bussard ramjet proton-proton fusion reaction is too low to be useful. Deepfuturetech proposes a different fusion mechanism via (p,n) reactions which involve a nucleus capturing a proton and subsequently emitting a neutron. These type of reactions have higher cross sections and could be tested in reactors in the near future. Further analysis is needed to confirm whether these reactions could produce neutrons at sufficiently low energy cost to enable profitable hydrogen fusion.

Artist depiction of a Bussard ramjet. Credits: NASA

Incidentally, Crowl talked about many of these starship concepts at a subsequent Starship Century Symposium held in 2013 by the Arthur C. Clarke Center for Human Imagination in collaboration with the Benford brothers who shared the highlights from their Starship Century anthology summarizing scientific results from the 100‐Year Starship project. You can also get a “Deeper Future View” of his independent research on interesting items not typically covered by the mainstream science media at his blog Crowlspace.

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Update on the Photonic Laser Thruster and the interplanetary Photonic Railway

Diagram depicting the layout of the Photonic Laser Thruster (PLT). Credits: Young K. Bae, Ph.D.

SSP reported last year on the promise of an exciting new Photonic Laser Thruster (PLT) that could significantly reduce travel times between the planets and enable a Phonic Railway opening up the solar system to rapid exploration and eventual settlement. The inventor of the PTL, Dr. Young K. Bae has just published a paper in the Journal of Propulsion and Power (behind a paywall) that refines the mathematical underpinnings of the PLT physics and illuminates some exciting new results. Dr. Bae shared an advance copy of the paper with SSP and we exchanged emails in an effort to boil down the conclusions and clarify the roadmap for commercialization.

Illustration of a Photonic Railway using PLT infrastructure for in-space propulsion established at (from right to left, not to scale) Earth, Mars, Jupiter, Pluto and beyond. Credits: Young K. Bae.

In the new paper, Dr. Bae refines his rigorous analysis of the physics behind the PLT confirming previous projections and discovering some exciting new findings.

As outlined in the previous SSP post linked above, the PLT utilizes a “recycled” laser beam that is reflected between mirrors located at the power source and on the target spacecraft. Some critical researchers have argued that upon each reflection of the beam off the moving target mirror, there is a Doppler shift causing the photons in the laser light to quickly lose energy which could prevent the PLT from achieving high spacecraft velocities. The new paper conclusively proves such arguments false and confirming the basic physics of the PLT.

There were two unexpected findings revealed by the paper. First, the maximum spacecraft velocity achievable with the PLT is 2000 km/sec which is greater than 10 times the original estimate. Second, the efficiency of converting the laser energy to the spacecraft kinetic energy was found to approach 50% at velocities greater than 100 km/s. This is surprisingly higher than originally thought and is on a par with conventional thrusters – but the PLT does not require propellent. These results show conclusively that once the system is validated in space, the PLT has the potential to be the next generation propulsion system.

I asked Dr. Bae if anything has fundamentally changed recently in photonic technology that will bring the PLT closer to realization. He said that the interplanetary PLT can tolerate high cavity laser energy loss factors in the range of 0.1-0.01 % that will permit the use of emerging high power laser mirrors with metamaterials, which are much more resistant to laser induced damage and are readily scalable in fabricating very large PLT mirrors.

With respect to conventional thrusters, he said the PLT can be potentially competitive even at low velocities on the order of 10 km/s, especially for small payloads. This is because system does not use propellant which is very expensive in space and because the PLT launch frequency can be orders of magnitude higher than that of conventional thrusters. Dr. Bae is currently investigating this aspect of the system in terms of space economics in depth.

The paper acknowledges that one of the most critical challenges in scaling-up the PLT would be manufacturing the large-scale high-reflectance mirrors with diameters of 10–1000m, which will likely require large-scale in-space manufacturing. Fortunately, these technologies are currently being studied through DARPA’s NOM4D program which SSP covered previously and Dr. Bae agreed that they could be leveraged for the Photonic Railway.

Artist’s concept of projects, including large high-reflectance mirrors, which could benefit from DARPA’s (NOM4D) plan for robust manufacturing in space. Credits: DARPA

I asked Dr. Bae about his timeline and TRL for a space based demo of his Sheppard Satellite with PLT-C and PLT-P propellantless in-space propulsion and orbit changing technology. He responded that such a mission could be launched in five years assuming there were no issues with treaties on space-based high power lasers. There is The Treaty on the Prevention of the Placement of Weapons in Outer Space but I pointed out that the U.S. has not signed on to this treaty. Article IV of the Outer Space Treaty states that “…any objects carrying nuclear weapons or any other kinds of weapons of mass destruction…” can not be placed in orbit around the Earth or in outer space. Dr. Bae said “We can argue that the [Outer Space] treaty regulation does not apply to PLT, because its energy is confined within the optical cavity so that it cannot destroy any objects.  Or we can design the PLT such that its transformation into a laser weapon can be prevented.”

He then went on to say: “For space demonstration of PLT spacecraft manipulation including stationkeeping, I think using the International Space Station platform would be one of the best ways … I roughly estimate it would take $6M total for 3 years for the demonstration using the ISS power and cubesats. The Tipping Point [Announcement for Partnership Proposals] would be a good [funding mechanism] …to do this.”

Once the technology of the Photonic Railway matures and is validated in the solar system Dr. Bae envisions its use applied to interstellar missions to explore exoplanets in the next century as described in a 2012 paper in Physics Procedia.

Conceptual illustration of the Photonic Railway applied to a roundtrip interstellar voyage to explore exoplanets around Epsilon Eridani. This application requires four PLTs: two for acceleration and two for deceleration. Credits: Young K. Bae

Be sure to listen live and call in to ask Dr. Bae your questions about the PLT in person when he returns to The Space Show on March 29th.

Update May 9, 2025: Dr. Bae has further refined his concept in a new book, Photonic Laser Propulsion. He returned to The Space Show to talk about it with Dr. David Livingston.

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DARPA announces Novel Orbital and Moon Manufacturing, Materials and Mass-efficient Design (NOM4D) program

Artist’s concept of projects which could benefit from DARPA’s (NOM4D) plan for robust manufacturing in space. Credits: DARPA

Pronounced “NOMAD” the Defense Advanced Research Projects Agency plan aims to develop technologies for adaptive, off-earth manufacturing to fabricate large structures in space and on the Moon.

Bill Carter, program manager in DARPA’s Defense Sciences Office explains in an announcement of the program, “We will explore the unique advantages afforded by on-orbit manufacturing using advanced materials ferried from Earth. As an example, once we eliminate the need to survive launch, large structures such as antennas and solar panels can be substantially more weight efficient, and potentially much more precise. We will also explore the unique features of in-situ resources obtained from the moon’s surface as they apply to future defense missions. Manufacturing off-earth maximizes mass efficiency and at the same time could serve to enhance stability, agility, and adaptability for a variety of space systems.”

The program will be split into three 18 month phases driven by metrics associated with progressively challenging exemplars such as respectively, a 1-megawatt solar array, a 100m diameter RF reflector, and finally IR reflective structures suitable for use in a segmented long-wave infrared telescope.

Lessons learned from the program could be applied to on-orbit manufacturing operations by commercial space companies as launch costs come down and access to cislunar space becomes more routine for both government and commercial entities.