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Minerva Space Settlement and University of Space Exploration

Conceptual illustration of the Minerva Space Settlement in orbit around Jupiter’s moon Ganymede. Credits: Minerva Project Team

Space Settlement Progress typically features the latest advancements in technology that are enabling the settlement of space.  This post will be a little different.  When attending the International Space Development Conference last May I was impressed by a team of students from Highschool Colegiul National Andrei Saguna in Romania, who had conceived of a space settlement in orbit around Jupiter’s satellite Ganymede which they call Minerva.  The project was an entry in the National Space Societies’ Space Settlement Contest, and for which they won a second place award for 9th graders.  While admiring their poster I was approached by Maria Vasilescu, who proudly described their project and agreed to collaborate with me on this post. She spoke perfect English, shared marketing materials (key chains, buttons and bookmarks with QR codes linking to their website) and explained that the primary purpose of Minerva would be a deep space location for a University of Space Exploration.  I was intrigued by the concept and was struck by Maria and her teammates’ enthusiastic vision of humanity’s future in space.  I wanted to know more about what motivated this group of teenagers to come together and create such an imaginative project, as youths like them will be future pioneers on the High Frontier.  Maria agreed to coordinate with her team on an interview via email about Minerva.

The Minerva Project Team and their poster session at ISDC 2023, a second prize winner for 9th graders of the NSS Space Settlement Contest. Credits: Minerva Project Team: clockwise from lower right: Bodean Mircea-Sorin, Ana Radus, Andrei Ioan Prunea, Alexandra Nica, Alexandra Maria Nemes, Maria Vasilescu

SSP: How did the team come up with this Minerva concept?

Minerva: We took inspiration from our school which gave us a lot of opportunities to which we owe a lot and we wanted to build such a university in the final frontier.

SSP: You mentioned stumbling across some obstacles during your journey but sticking together by motivating each other.  Is this an experience you feel comfortable sharing?

Minerva: One of the hardest things was to think about all the aspects that go into making a space settlement as ninth graders, such as the form [Forum on the website], which was decided in the last week, or the economical part. But we managed to meet often and brainstorm to come up with better ideas.

SSP: You said that the project helped you discover your true selves. Can you explain how this came about?

Minerva: We developed ourselves and our passions and we found out what we like because it covers a broad area of subjects beyond science. We managed to see by which area we are drawn to and enjoy actually researching.

SSP: You’ve stated that one of the reasons for building Minerva is to invent new lifestyles different from those that exist on Earth. How do you envision lifestyles changing in space?

Minerva: The university can prepare you for life in space, which will be an important part in the humans’ future, therefore we don’t want to invent new lifestyles, but incorporate space in the ones that already exist.

SSP: You’ve proposed auctioning a Minerva NFT to fund your efforts and future experiments.  Would this be the sole source of financing for the project, and will it be sufficient?  What about simply charging tuition for the USE?

Minerva: Everything on our settlement is given and made by us for the people so they don’t need to have money to buy material things. And because we have worked to make almost everything renewable and green, the funds MinervaNFT will bring are more than sufficient for everything else. And as for tuition, we feel like putting students through an exam such as the one that defines their attendance to USE is stressful enough as it is. However, the students will need to pay for the transport from Earth to the settlement.

SSP: There does not appear to be any trade or economic activity on Minerva, only academic studies. Students may choose to return to Earth or stay on the space station after they complete their studies. If they stay, have you considered the possibility of graduates developing and marketing other industries such as software development, robotics, mining water from Ganymede as rocket fuel, intellectual property on life support systems, or many other potential industries that could arise from scientific innovation that would take place on a space settlement? Or would this be totally an academic institution?

Minerva: It is not a totally academic institution because we have two thirds of the ship which will be occupied by students that remained on the settlement. But here, you don’t need money, everything being provided by us, so people don’t work for money, they work to occupy time, for enjoyment. If they do develop other industries, it will be fully for the greater good of humanity and the future of our kind, not for money.

SSP: The location chosen for Minerva is very challenging from an engineering perspective.  Although Ganymede is not deep in Jupiter’s magnetosphere, and has its own magnetic field which could help mitigate exposure, the location will still have high levels of radiation if unprotected, which complicates the design because much more mass is needed to provide adequate shielding to be safe for humans.  In addition, travel times to Jupiter are quite long even with improved propulsion which you’ve indicated would be as high as four years for students wanting to make the journey.  Finally, solar energy at Jupiter’s remote distance from the sun requires that photovoltaic arrays be enormous to provide sufficient energy. A good compromise might be the asteroid Ceres, which is believed to be 25% water and does not have a magnetic field generating high radiation like what would be experienced at Jupiter.  Others have proposed this asteroid as a good destination for space settlement.  Why not locate the settlement in a more accessible and hospitable environment that might reduce costs? 

Minerva: The main reason we chose such a far away location is precisely because we want to explore as much as possible of the cosmos. It’s not that we don’t want a closer location, it’s just that we know very little about Jupiter and its surrounding moons and further and this university can offer humanity an opportunity to explore it and send the research back to Earth. At the same time, we have taken the radiation into consideration and just how today’s spaceships have protection against it, so how [sic] our settlement, but ten times more efficient.

SSP: The sources of power for Minerva include solar arrays and nuclear fission, but you excluded fusion energy because it is currently experimental.  By the time it will be technologically possible to travel to Jupiter and establish infrastructure that far out in the solar system, we will have developed fusion energy for use on Earth as well as in space.  The preliminary design work for a Direct Fusion Drive for rapid transit to the outer planets has been started by Princeton Satellite Systems and the Fusion Industry Association just came out with their third annual report stating that the industry has now attracted over $6 billion in investment.  When it is feasible to begin work on Minerva, fusion power sources will likely be available. Will you be updating your project plan as new technologies become available? 

Minerva: Of course, we are sure that many aspects of our settlement can be improved by future developments in science, engineering and many other fields. As much as possible, we will incorporate them into our settlement. As mentioned in our paper, when talking about technological advances that may happen, we have to keep up with innovation and incorporate them to help us fulfill every need when travelling to space.

SSP: You raised the concern that Earth is approaching a major crisis with population growth putting a strain on Earth’s vital resources.  You also said that the purpose of the space community is to sustain humanity if Earth’s environment became unfavorable for life.  In selecting the location of Minerva, when considering Mars and its orbital distance, you said that even though it fulfills most of your requirements “…the disadvantage of Mars its it proximity to Earth…” and it “…is too close to our planet in order for us to choose it as the proper placement for the spacecraft.”  Why must Minerva be distant from Earth if the planet is in crisis in the future and why isn’t the orbit of Mars, at 56 million kilometers, considered not far enough away?

Minerva: Mars wasn’t a viable option because, as we have stated before, the purpose of the USE is to gather information and scientific news that can only be found in the farther cosmos. We already know a lot about Mars and planets in close proximity to Earth, we want to venture further, discover and experiment with more than we already have.

SSP: Some surveys say that young people live in fear of the future due to climate change.  Many media outlets amplify this doom and gloom.  However, some economists point out that using the United Nation’s own data from the Intergovernmental Panel on Climate Change, with the predicted increase in temperature by the year 2100, global GDP will be reduced by only 4% to deal with climate related impacts.  Although it is clear that we should eventually reduce our dependance on fossil fuels this is not an existential threat.   Plus, technological innovation continues to improve efficiency in resource utilization, energy development and agriculture, enabling higher standards of living notwithstanding increasing population growth. 

The viewpoint that the Earth is in “crisis” is closely aligned with Elon Musk’s motivation, who believes it is urgent that we become a multiplanetary species, to have a “Plan B” in case of a planetwide catastrophe.  Jeff Bezos has a different perspective, that heavy industrial activity could be moved off world to preserve the Earth’s natural environment and to improve humanities’ standard of living though utilization of unlimited space resources.  

Gerard K. O’Neill saw the promise of space settlement as a way to solve Earth’s problems through the humanization of space.  He saw it as a way to end poverty for all humans, provide high-quality living space that would continue to grow robustly, to moderate population growth without war, famine, dictatorship or coercion; and to increase individual freedom.  Does your team share the same anxiety about the future as other young people: that life on Earth is doomed and therefore, we need to build Minvera as a sanctuary to preserve humanity?  Or do you see it as one among many options for space settlement to improve life on Earth and beyond, as outlined in O’Neill’s vision?

Minerva: We see Minerva as a place where people that are smart and passionate about space have a chance to make scientific discoveries that would be impossible to do on Earth. Aligned with Gerald O’Neil’s [sic] view, we believe that humans should expand into space whether it is as a Plan B or by harvesting resources from other planets or celestial objects. With the help of Minerva, the smartest children of their generation will be able to experience these scenarios and be closer to the future. We don’t see Minerva as a Plan B for humanity, students that have finished their 4 years being able to return to earth, but rather as a place where people can enjoy a stress free and enjoyable environment. Therefore Minerva is preparing smart youngsters to be able to take advantage of any of the two cases. If they choose to remain on Earth, the knowledge that they acquired while in the USE will definitely increase humanity’s survivability against the existential threats mentioned.

SSP: You’ve created a survey [what was earlier referred to as a “Form” and can be found at the “Forum” link on the Minerva website] for anyone to express their opinion about your project and the prospect of living in space.  Will you use this feedback to improve your project? 

Minerva: Maybe in the future, yes. We have encouraged people to complete the survey honestly and there’s always place for improvement for anything. And the second reason is to observe humanity’s view on such a settlement. In creating such a complex space settlement, you need to align your view with the society’s beliefs, them being the ones who will eventually populate it.

SSP: Does your team expect to remain engaged with the project as you progress in your education and after you eventually establish your careers here on Earth?

Minerva: It was certainly an experience we will treasure for a long time, but not everything has to be drawn out. I think this project took a lot of work and effort and we want to invest into something new, see this contest from as many angles as possible while we can. This project like no other can incorporate so many aspects of society from which you can discover your biggest passions. Talking to everyone in our group, we found that each one of us enjoyed a different part of the project and we believe that that was the key to our win. We were all doing something we are passionate about and therefore worked even harder for the final result. Now that we’ve learned what topics intrigue us, we can start doing even more work in that domain. We believe that this project is the perfect opportunity and will open numerous doors in any future career path. We strongly recommend this contest to anyone wondering whether they should put their effort into it or not.

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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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The thorium molten salt reactor for Earth and space applications

Schematic of the Thorium Molten Salt Reactor for space propulsion applications. Credits: Ajay Kothari / The Space Review

President Joe Biden recently signed into law a sweeping climate bill that will have very little (if any) impact on addressing global warming (a reduction of 0.028 degrees F by 2100). While there are tax credits in the bill for construction of new nuclear power plants over the next 10 years, only two are planned to add to the existing 93 facilities operating today which provide 18% of the U.S. energy production. Most of the funding in the bill is targeted at tax credits for EVs and incentives for renewable sources such and wind and solar which are subject to interruption. Nuclear energy holds enormous promise to offset the carbon emissions associated with fossil fuel energy production and can provide reliable base load power, but it is still plagued by negative public perceptions related to safety and the potential for weapons proliferation.

Is it time to reimagine our approach to sourcing clean energy in general, and nuclear power in particular while at the same time addressing climate change? Ajay Kothari thinks so – by research and development and eventual commercialization of nuclear power plants fueled by thorium rather than uranium. Dr. Kothari describes his vision in the August 1, 2022 issue of The Space Review. He believes that this powerful and sustainable power source “…will solve the world’s energy problem a thousand times over with zero carbon dioxide emission during operation, and it may be the cheapest form of energy production for us.”

“One ton of thorium is roughly equivalent to five million barrels of oil”

Thorium is abundant in the Earths crust making it relatively cheap and therefore, more affordable. It is only slightly radioactive, far less so then uranium and does not contain fissile material making it much safer and easier to moderate (i.e. switch off) in the case of an accident. This would prevent meltdowns unlike conventional reactors which have coolants that operate at much higher pressures and need far more complicated engineering safeguards to prevent disasters.

Thorium molten salt reactors are inherently safe. Flibe Energy is designing a Liquid Fluoride Thorium Reactor (LFTR) and according to the company’s website, “…any increase in operating temperature reduces the density of the salt which in turn, causes the reaction to slow and the temperature to fall. LFTR is also designed with a simple frozen salt plug in the bottom of the reactor core vessel. In the event of power loss to the reactor, the frozen salt plug quickly melts and the fuel salt drains down into a storage tank below – causing a termination in the fission process.”

Once developed for energy production on Earth, the same technology has applications in space. While it would not be used in a booster during launch, a molten salt thorium reactor upper stage, like that shown in the illustration above, could provide an efficient 700 second specific impulse by heating hydrogen as fuel for advanced propulsion for the next few decades until fusion energy comes on line. An added benefit would be that the upper stage reactor could also be used to provide energy at the destination, for example on the Moon or Mars.

“One kilogram of thorium taken from Earth [to the Moon] … can support a 2.6 thermal megawatt plant for a year.”

A thorium reactor was developed at Oak Ridge National Laboratory (ORNL) back in the 1960s but was never commercialized after the then Atomic Energy Commission favored plutonium fast-breeder reactors.

Diagram of the thorium fuel cycle in molten salt reactors. Credits: Flibe Energy

There are challenges to overcome. For example, the thorium fuel cycle is complicated and still produces some radioactive waste, but far less and with much shorter half life when compared to conventional uranium nuclear reactors. But the benefits of this clean, abundant and affordable energy source could make investment by the public and private sector worth the effort.

“With US reserves at 595,000 tons of thorium, we have enough to last us 600 years at current rates.”

Kothari has been a long time proponent of Thorium reactors. He recently gave a talk on the molten salt thorium reactor via Zoom for the University of Maryland now available on YouTube. You can also hear an in-depth discussion of the technology on The Space Show when he was a guest back in October 2021 and when he returns to the show September 13, 2022.

Dr. Kothari agreed to take a deeper dive with SSP into what he calls “Thor – The Life-Saver” through an email interview. If you have questions I didn’t cover about thorium molten salt reactors please leave a comment.

SSP: Dr. Kothari, thank you for taking the time to answer my questions. With respect to the public’s fear of nuclear power in general, the safety of thorium molten salt reactors is certainly an argument in favor to the technology. But aren’t there still risks of nuclear proliferation?

AK: We have more than 400 reactors in more than 40 countries worldwide. We found ways to have countries develop their reactors but have proliferation controls. This idea, the TMSR, creates no Plutonium, and would be easier to monitor. Besides, whether we want [to] or not, other countries WILL do it. Many are. Also we can develop the technology for ourselves and [for] friendly countries OR at the very least, USE IT FOR OURSELVES! How can we deny this incredible opportunity for our (US) populace? Is that fair?

SSP: Flibe Energy appears to be the only U.S. company pursuing LFTR technology. Chicago based Clean Core is focusing on thorium-based fuels to be used in existing pressurized heavy-water reactor designs. What do you think of these two company’s approaches and are you aware of any other thorium reactor development efforts in the U.S, either in private industry or academia?

AK: MIT is developing tech to resolve some of the TMSR issues that would be quite helpful [SSP found this story from MIT Nuclear Reactor Laboratory on deployment of its “…nuclear reactor (MITR) and related testing apparatus as a proving ground for the materials and processes critical to molten-salt-cooled reactors.”]. Others are shown in the chart below with some of them being US based (bottom right).

Color coded map showing global molten salt reactor technology development activities and the sponsoring country/entities. FHR= Fluoride salt-cooled high-temperature reactor. LEU = Low Enriched Uranium. HEU= Highly Enriched Uranium. TRU=Transuranic wastes, i.e. heavier elements than Uranium. Credits: Oak Ridge National Laboratory

SSP: How difficult would it be to adapt this technology for space propulsion and power applications and is it so far off that fusion energy may be available by the time development efforts come to fruition?

AK: In my opinion, …. controlled fusion may be 100, 200 or 50 years away. We have a valley of death … between now and then. This TMSR can fill the gap but can also be used for space propulsion as my diagram above shows. Sure, the TRL of it needs to be brought up, but that’s what we are here for. It would be less heavy than [the] NERVA idea, especially if the chemical processing plant is separated and U233 is used for space propulsion rather than Th232. This would be the idea. The rate of fission is then controlled by the graphite rod moderators/controllers.

SSP: China has been working on a LFTR since 2011 and was recently cleared to start operating the reactor which is a direct descendent of the original experimental design that ORNL studied in the 1960s. It would appear that the Chinese have a significant head start. Is this concerning?

AK; Absolutely. All I can say is that we are idiots.

SSP: One of the disadvantages of thorium reactors is that large upfront costs are needed due to the significant amount of testing and licensing work for qualification of commercial reactors. The reactors also involve high fuel fabrication and reprocessing costs. How would you address these issues to attract investors?

AK: This idea really is a golden nugget, so to speak. The way to attract investors is to bring the TRL up with government (DoE, NASA and DoD) funds. When the light at the end of the tunnel is seen by investors, they will jump in with both feet. It may still be 5-10 years away but if we do not do it soon, (1) it will always remain so, and (2) some other country (China) or many other countries will DEFINITELY move ahead of us!

SSP: Another disadvantage is the presence of a significant level of gamma ray emissions due to Uranium-232 in the fuel cycle. How will this be dealt with safely?

AK: The Gamma ray radiation occurs from Protactinium 233 absorbing another neutron (before it Beta decays) to become Pa234 If it is separated in a chemical processing plant, it would remain easier to handle. From Wiki[pedia]: “The contamination could also be avoided by using a molten-salt breeder reactor and separating the 233Pa before it decays into 233U)”.

SSP: What regulatory and policy changes are needed to realize this technology in the U.S.?

AK: [The] NRC and DoE should allow smaller (~2 MW) size experimental reactors at Universities and research institutions right now.

SSP: On a related note, what efforts can leaders in private industry, academia and government undertake to begin the research and technology needed to commercialize thorium molten salt reactors.

AK: There are a few uncertain items in this nuclear process that Universities, small businesses and government research institutions can resolve. Government agencies need to fund SBIR/STTR type of initiatives to address the following technical issues:

  1. The sustainability of the heat exchangers whether they are to be made of Hastelloy-N or some other composite. This characterization is needed w.r.t. neutron flux intensity, temperature reached and time exposed (in months to years)
  2. The same as above for reactor containment vessels and pipes carrying the hot molten salt.
  3. Chemical separation for in-line or off-line work for Protactinium and U233.
  4. Tritium mitigation ideas (probably using CO2 in closed loop for electricity generation) or sequestration of it for later use in fusion when and if available. Designing and demonstrating tritium separators are key elements of DOE’s solid fuel MSR program at both universities and national laboratories
  5. Gamma ray mitigation or reduction

Thorium doesn’t spontaneously undergo fission – when an atom’s nucleus splits and releases energy that can generate electricity. Left to its own devices it decays very slowly, giving off alpha radiation that can’t even penetrate human skin, so holidaymakers don’t need to worry about sunbathing on thorium-rich beaches.

We don’t have as much experience with Thorium. The nuclear industry is quite conservative, and the biggest problem with Thorium is that we are lacking in operational experience with it. When money is at stake, it’s difficult to get people to change from the norm.

Irradiated Thorium is more dangerously radioactive in the short term. The Th-U cycle invariably produces some U-232, which decays to Tl-208, which has a 2.6 MeV gamma ray decay mode. Bi-212 also causes problems. These gamma rays are very hard to shield, requiring more expensive spent fuel handling and/or reprocessing.

Thorium doesn’t work as well as U-Pu in a fast reactor. While U-233 an excellent fuel in the slow-neutron regime, it is between U-235 and Pu-239 in the fast spectrum. So for reactors that require excellent neutron economy (such as breed-and-burn concepts), Thorium is not ideal.

Proliferation Issues

Thorium is generally accepted as proliferation resistant compared to U-Pu cycles. The problem with plutonium is that it can be chemically separated from the waste and perhaps used in bombs. It is publicly known that even reactor-grade plutonium can be made into a bomb if done carefully. By avoiding plutonium altogether, thorium cycles are superior in this regard.

Besides avoiding plutonium, Thorium has additional self-protection from the hard gamma rays emitted due to U-232 as discussed above. This makes stealing Thorium based fuels more challenging. Also, the heat from these gammas makes weapon fabrication difficult, as it is hard to keep the weapon pit from melting due to its own heat. Note, however, that the gammas come from the decay chain of U-232, not from U-232 itself. This means that the contaminants could be chemically separated and the material would be much easier to work with. U-232 has a 70 year half-life so it takes a long time for these gammas to come back.

The one hypothetical proliferation concern with Thorium fuel though, is that the Protactinium can be chemically separated shortly after it is produced and removed from the neutron flux (the path to U-233 is Th-232 -> Th-233 -> Pa-233 -> U-233). Then, it will decay directly to pure U-233. By this challenging route, one could obtain weapons material. But Pa-233 has a 27 day half-life, so once the waste is safe for a few times this, weapons are out of the question. So concerns over people stealing spent fuel are largely reduced by Th, but the possibility of the owner of a Th-U reactor obtaining bomb material is not.

Molten Salt Reactors

See our full page on Molten Salt Reactors for more info.

One especially cool possibility suitable for the slow-neutron breeding capability of the Th-U fuel cycle is the molten salt reactor (MSR), or as one particular MSR is commonly known on the internet, the Liquid Fluoride Thorium Reactors (LFTR). In these, fuel is not cast into pellets, but is rather dissolved in a vat of liquid salt. The chain reaction heats the salt, which naturally convects through a heat exchanger to bring the heat out to a turbine and make electricity. Online chemical processing removes fission product neutron poisons and allows online refueling (eliminating the need to shut down for fuel management, etc.). None of these reactors operate today, but Oak Ridge had a test reactor of this type in the 1960s called the Molten Salt Reactor Experiment [Wikipedia] (MSRE). The MSRE successfully proved that the concept has merit and can be operated for extended amounts of time. It competed with the liquid metal cooled fast breeder reactors (LMFBRs) for federal funding and lost out. Alvin Weinberg discusses the history of this project in much detail in his autobiography, The First Nuclear Era [amazon.com], and there is more info available all over the internet. These reactors could be extremely safe, proliferation resistant, resource efficient, environmentally superior (to traditional nukes, as well as to fossil fuel obviously), and maybe even cheap. Exotic, but successfully tested. Who’s going to start the startup on these? (Just kidding, there are already like 4 startups working on them, and China is developing them as well).

Loss of coolant accident consequences are significantly different than for Light Water Reactors

– Low driving pressure and lack of phase change fluids

– Guard vessels employed on some designs

– Planned vessel drain down to cooled, criticality-safe drain tanks on some designs

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Dennis Wingo’s strategy for development of cislunar space and beyond

Image credit: NASA/Goddard/Arizona State University

The Cislunar Science and Technology Subcommittee of the White House Office Science and Technology Policy Office (OSTP) recently issued a Request for Information to inform development of a national science and technology strategy on U.S. activities in cislunar space.

Dennis Wingo provided a response to question #1 of this RFI, namely what research and development should the U.S. government prioritize to help advance a robust, cooperative, and sustainable ecosystem in cislunar space in the next 10 to 50 years?

In a prolog to his response Wingo reminds us that historically, NASA’s mission has focused narrowly on science and technology.  What is needed is a sense of purpose that will capture the imagination and support of the American people.    In today’s world there seems to be more dystopian predictions of the future than positive visions for humanity.  We seem to be dominated by fear of “…doom and gloom scenarios of the climate catastrophe, the degrowth movement, and many of the most negative aspects of our current societal trajectory.”  This fear is manifested by what Wingo defines as a “geocentric” mindset focused primarily within the material limitations of the Earth and its environs.

“The question is, is there an alternative to change this narrative of gloom and doom?”

He recommends that policy makers foster a cognitive shift to a “solarcentric” worldview: the promise of an economic future of abundance through utilization of the virtually limitless resources of the Moon, Asteroids, and of the entire solar system.  An example provided is to harvest the resources of the asteroid Psyche which holds a billion times the minable metal on Earth, and to which NASA had planned on launching an exploratory mission this year but had to delay it due to late delivery of the spacecraft’s flight software and testing equipment.

Artist rendering of NASA’s Psyche Mission spacecraft.  Credits: NASA/JPL-Caltech/Arizona State Univ./Space Systems Loral/Peter Rubin

Back to the RFI, Wingo has four recommendations that will open up the solar system to economic development and address many of the problems that cause the geocentrists despair. 

First, we should make the Artemis moon landings permanent outposts with year long stays as opposed to 6 day “camping trips”. This should be possible with resupply missions by SpaceX as they ramp up Starship launch rates (assuming the launch vehicle and lander are validated in the same timeframe, which seems reasonable). Next, we need power and lots of it – on the order of megawatts.  This should be infrastructure put in place by the government to support commerce on the Moon.  By leveraging existing electrical power standards and production techniques, large scale solar power facilities could be mass produced at low cost on Earth and shipped to the moon before the capability of in situ utilization of lunar resources is established.  Some companies such as TransAstra already have preliminary designs for solar power facilities on the Moon.

Which brings us to ISRU.  The next recommendation is to JUST DO IT.  This technology is fairly straightforward and could be used to split oxygen from metal oxides abundant in lunar regolith to source air and steel.  Pioneer Astronautics is already developing what they call Moon to Mars Oxygen and Steel Technology (MMOST) for just this application.

Conceptual illustration of the Lunar OXygen In-situ Experiment (LOXIE) Production Prototype. Credits: Mark Berggren / Pioneer Astronautics

And lets not forget the wealth of in situ resources that could be unlocked via synthetic geology made possible by Kevin Cannon’s Pinwheel Magma Reactor.

Conceptual depiction of the Pinwheel Magma Reactor on a planetary surface in the foreground and in free space on a tether as shown in the inset. Credits: Kevin Cannon

Of course there is water everywhere in the solar system just waiting to be harvested for fuel and life support in a water-based economy.

Illustration of an ice extraction concept for collection of water on the Moon. Credits: George Sowers / Colorado School of Mines

Wingo’s final recommendation is industrialization of the Moon in preparation for the settlement of Mars followed by the exploration of the vast resources of the Asteroid Belt.  He makes it clear that this is more important than just a goal for NASA, which has historically focused on scientific objectives, and should therefore be a national initiative.

“…for the preservation and extension of our society and to preclude the global fight for our limited resources here.”

With the right vision afforded by this approach and strong leadership leading to its implementation, Wingo lays out a prediction of how the next fifty years could unfold. By 2030 over ten megawatts of power generation could be emplaced on the Moon which would enable propellant production from the pyrolysis of metal oxides and hydrogen production from lunar water.  This capability allows refueling of Starship obviating the need to loft propellent from Earth and thereby lowering the costs of a human landing system to service lunar facilities.  From there the cislunar economy would begin to skyrocket.

The 2040s see a sustainable 25% annual growth in the lunar economy with a burgeoning Aldrin Cycler business to support asteroid mining and over 1000 people living on the Moon.

By the 2050s, fusion reactors provide power and propulsion while the first Ceres settlement has been established providing minerals to support the Martian colonies.

“The sky is no longer the limit”

By sowing these first seeds of infrastructure a vibrant cislunar economy will enable sustainable settlement across the solar system. A solarcentric development mythology may be just what is needed to become a spacefaring civilization.

Artist’s concept of an O’Neill space colony. Credits: Rachel Silverman / Blue Origin

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Converting orbital trash to treasure with CisLunar Industries’ Micro Space Foundry

Illustration of orbital debris recycling. Instead of deorbiting after a few missions, debris removal spacecraft can refuel themselves with metal propellant using the Micro Space Foundry extending the lifespan and lowering costs. Credits: CisLunar Industries

CisLunar Industries is developing an innovative way to clean up Earth orbit by recycling spent rocket stages and other orbital debris using their Micro Space Foundry (MSF). In a March 2 presentation to the Future In-Space Operations telecon, CisLunar CEO Gary Calnan described the technology and markets for the MSF, development of which was funded by an SBIR/STTR grant from NASA. There is a vast untapped value chain of metals high above our heads. Over the last 60 years as satellites have been launched into space, the used upper stages have been cluttering up low Earth orbit and beyond. But the trash has value because it is useful material in orbit that has already incurred the launch cost.

The system works by robotically cutting aluminum feedstock off of derelict satellites and then processing the metal through the MSF using electromagnetic levitation furnace technologies originally proven on the ISS for virtually contactless metal recycling and reuse in a weightless environment. The MSF spits out rods of “fuel” to feed a Neumann Thruster on the debris removal spacecraft, which can then be powered to deorbit the target satellite and move on to its next destination. Rinse and repeat. The architecture has the potential to change the economics of the cislunar economy by harvesting a valuable in situ resource while cleaning up Earth orbit at the same time.

The Neumann Thruster, invented by Dr. Patrick “Paddy” Neumann, is an electric propulsion system for in-space use which is a highly adjustable, efficient and scalable method for moving satellites where they are needed. The Neumann Drive uses solid metal propellant and electricity to produce thrust via a pulsed cathodic arc system analogous to an arc welder. Neumann, who created the company Neumann Space to commercialize his invention, explains the physics behind the thruster in a video of an early prototype.

CisLunar Industries has other applications planned for the MSF in an emerging in-space ecosystem. In addition to extruding metallic rods as propellant, the system can fabricate long tubes for large-scale space structures or wires for additive manufacturing enabling an in-space commodities value chain and creating demand for processed metals.

Conceptual illustration of the MSF core processing unit, utilizing a modular design to enable lower cost flexible deployment and multiple products in an emerging cislunar economy. Credits: CisLunar Industries

So how mature is the technology? CisLunar has already demonstrated component validation in the lab taking the system to TRL 4. You can see a video documenting the experiment at timestamp 35:54 here. A parabolic flight to run an experiment in simulated weightlessness is scheduled for later this year. Actual in-space end-to-end demonstration with a Neumann Thruster is planned in 2024 via an agreement with Australian space services company Skykraft.

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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.

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Wind Rider propellentless space drive for rapid transit across the solar system

Conceptual illustration of the Wind Rider plasma magnet drive: Credits: Brent Freeze

When humanity eventually moves out into the galaxy to settle new worlds, we will need to take stock of potentially habitable planets capable of sustaining life as we know it to identify potential new homes. The James Webb Space Telescope will have the capability to search for exoplanets in the habitable zones of stars in our local neighborhood by using spectroscopy to reveal biosignatures in the planet’s atmosphere as starlight filters through it when transiting across the disk of the host star. But to discern more detail on the surfaces of these distant new Earths, much more powerful methods for imaging will be needed.

One such method could be to utilize a solar gravitational lens (SGL), a property arising from the Theory of Relativity where large gravitating masses bend light resulting in the possibility of a natural telescope capable of very powerful magnification and significant angular resolution. This would require placing a detector beyond 550 astronomical units from the sun. Such an instrument could potentially resolve the size and shape of continents adjacent to oceans on exoplanets orbiting TRAPPIST-1 or other nearby stars. Located 40 light years away, this star is an ultra-cool red dwarf with seven rocky planets, three of which are in the habitable zone where liquid water can exist.

But getting out to this distance with conventional rockets would take over a hundred years. Voyager 1 is currently over 150 AU from the sun and was launched back in 1977. Enter the Wind Rider plasma magnet drive. A pathfinder mission using this concept to demonstrate the technology of a mission out to the SGL to image planets in the TRAPPIST-1 system will be presented by Brent Feeze, an AIAA mechanical engineer, in a poster session at the American Geophysical Union meeting this month. Calculations show that a spacecraft using this drive could sprint to the SGL focal plane in about eight years. The Wind Rider was also described recently by Alex Tolley on Centauri Dreams.

Originally conceived by John Slough at the University of Washington under a NASA NIAC grant from 2004 – 2005, the system is a propellentless drive that works by creating a rotating magnetic field that traps the charged particles in the solar wind to create a large circular electric current, inducing a large scale magnetosphere. Thrust is imparted to the craft via magnetic fields, analogous to the coupling induced in an electric motor. Unlike a solar sail, the trajectory of the craft is a straight line out from the sun toward its destination, with no gravity assists from other planets and a rapid acceleration to a velocity approaching that of the solar wing (400 km/s).

Jeff Greason, Board Chairman of the Tau Zero Foundation covered the technology during a presentation at the Tennessee Valley Interstellar Workshop back in 2017. He called it a “Ridiculously high thrust to weight magnetic sail” that by chemical propulsion standards is “blindingly fast”. Greason was looking into how Tau Zero could help support a small technology demonstrator on a ride share launch but it would have to be on payloads headed out toward cislunar space to be free of the Earth’s magnetosphere which deflects the solar wind.

Alex Tolley: “If it works as advertised, it would open up the solar system to exploration by fast, cheap robotic probes and eventually crewed ships.”

To be able to image a potentially new world for interstellar settlement is an exciting technology. The hardware required is not expensive and the scientific payoff of such a mission would be valuable from an astrophysical perspective. However, what we already know about the TRAPPIST-1 system is that life as we know it would have a tough time getting started and persisting because these worlds are bathed in intense ultraviolet radiation as they orbit within a range of about 3 – 6 million kilometers from TRAPPIST-1. That said, a pathfinder mission of a Wave Rider to send imaging equipment to the SGL could help prove the technology for rapid transit to the outer solar system as well as validating imaging techniques which could be used on more promising exoplanet candidates for eventual settlement. And expanding our knowledge of planetary systems in the galaxy would be icing on the cake.

TRAPPIST-1e – JPL Travel Poster. Beautiful but life is unlikely due to intense radiation from stellar winds: Credits: Jet Propulsion Laboratory

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Saving Earth and opening the solar system with the nuclear rocket

The NERVA solid core nuclear rocket engine. Credits: NASA

James Dewar believes it is time to reconsider the solid core nuclear thermal rocket, like what was developed in the 1960s under the NASA’s Nuclear Engine for Rocket Vehicle Application (NERVA) Project, as a high thrust cargo vehicle for opening up the solar system and for solving problems here on Earth. A tall order, as he explained in his appearance on The Space Show (TSS) October 26, because nuclear propulsion within the atmosphere and close to the Earth was taken off the table by NASA over 60 years ago and research on nuclear rockets was put on ice after 1973 until recently. Dewar worked on nuclear policy at the Atomic Energy Commission and its successor agencies, the Energy Research and Development Administration and the Department of Energy. He has documented his views in a paper linked on TSS blog.

What is old could be new again. NERVA had a very light high power solid core reactor with Uranium 235 fuel in a graphite matrix creating nuclear fission to heat hydrogen to produce rocket thrust. The specific impulse (efficiency in conversion of fuel to thrust) of the first iteration of NERVA was about 825 seconds, or almost twice that of chemical rockets. More efficient versions were on the drawing board. The compact design (35×52-inch core) lends itself to low development costs and would be inexpensive to fabricate and operate. It has the potential to lower launch costs significantly and research could pick up where it left off nearly 50 years ago.

So why is NASA announcing development of new nuclear thermal propulsion systems for missions to Mars in the distant future? The reactor cores like those used in Project NERVA are known technologies that can it be adapted for other useful applications and it can be done safely on Earth. There could be a large niche market for energy production in remote rural areas such as Alaska or Canada, or supplementing base load utilities during power disruptions due to severe weather events. With their high operating temperatures, these reactors can replace fossil fuel power generation for manufacturing industries that require process heat such as steel/aluminum or chemical production, which cannot be powered efficiently by wind or solar energy. There may also be a cost advantage and environmental benefit to replacing carbon based fuels for powering maritime oceangoing vessels.

“Even the Greens may support it…What if a reestablished program included making a nuclear propelled 1000-foot tanker sized skimmer to rid the oceans of plastic?”

Additionally, a nuclear reactor of this type could service manufacturing centers in both space and on Earth. It could inexpensively launch satellites and provide power for environmental and solar weather stations to monitor and protect Earth’s health. Dewar even thinks that the solid core nuclear reactor could be used to address the growing global problem of industrial waste by melting it down to its chemical constituents and then separating out commercially valuable components from the actual waste prior to permanent disposal. The low launch costs of the nuclear rocket may actually make disposal of waste off Earth economically feasible. Whole clean industries could spring up around these process centers. So this type of reactor could address many national goals and objectives rather than just crewed missions to Mars or deep space.

But what about the elephant in the room? Safety, radiation and fear of all things “nuclear”? Would the public support ground based testing if a NERVA type solid core nuclear thermal rocket program were restarted? Dewar covers this in detail in his book The Nuclear Rocket, Making Our Planet Green, Peaceful and Prosperous. As reported by the EPA in 1974, “…It is concluded that off-site exposures or doses from nuclear rocket engine tests at [the] NRDS [Nuclear Rocket Development Station] have been below applicable guides.”

What about regular launches of a nuclear rocket in the Earth’s atmosphere? First, the launch range proposed would be in an isolated ocean area over water to eliminate the possibility of failure or impact in populated regions. Second, the nuclear core would be enclosed in a reentry vehicle type cocoon for safe recovery in the event of an accident. Third, the nuclear engine is envisioned as an upper stage and would not be “turned on” until boosted high in the stratosphere, thus emission of gamma rays and neutrons from the fission reaction would not be any different then the radiation already impinging on our atmosphere from cosmic and solar radiation.

“…the best way to banish fear is for citizens to profit from the program.”

There is also the potential for the U.S. and its citizens to profit from this venture. Dewar suggests a governance framework for creating a public/private corporation in which the private sector is in charge, but leases assets from NASA and DOE. The government would support the venture via isolated testing sites, providing technical advice, supplying the uranium fuel and security to guard against potential nuclear proliferation. The public/private partnership would be set up to incentivize citizen participation through stock purchases and distribution of dividends in addition to providing jobs and funding the missions.

“Another source of funding would exist beyond the government or private billionaires: the public now has access”

Dewar concludes his paper with an inspirational statement: “…a new space program emerges based on science, not emotion, one that maximizes the technology for terrestrial applications, one that neuters the rocket equations and democratizes the space program, allowing citizens to participate and profit, and one that ever integrates Earth into the Solar System.”

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Where is the mother lode of space mining? The Moon or near-Earth asteroids?

Conceptual rendering of TransAstra Honey Bee Optical Mining Vehicle designed to harvest water from near-Earth asteroids: Credits: TransAstra Corporation

Advocates for mining the Moon and asteroids for resources to support a space based economy are split on where to get started. Should we mine the Moon’s polar regions or would near-Earth asteroids (NEAs) be easier to access?

Joel Sercel, founder and CEO of TransAstra Corporation, is positioning his company to be the provider of gas stations for the coming cislunar economy. In a presentation on asteroid mining to the 2020 Free Market Forum he makes the case (about 10 minutes into the talk) that from an energy perspective in terms of delta V, NEAs located in roughly the same orbital plane as the Earth’s orbit may be easier to access for mining volatiles and rare Earth elements.

Scott Dorrington of the University of New South Wales discusses an architecture of a near-Earth asteroid mining industry in a paper from the proceedings of the 67th International Astronautical Congress. He models a transportation network of various orbits in cislunar space for an economy based on asteroid water-ice as the primary commodity. The network is composed of mining spacecraft, processing plants, and space tugs moving materials between these orbits to service customers in geostationary orbit.

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Illustration depicting the layout of a transportation network in an asteroid mining industry in cislunar space. Credits: Scott Dorrington

On the other side of the argument, Kevin Cannon of the Colorado School of Mines in a post on his blog Planetary Intelligence lays out the case for the Moon being the best first choice. All of the useful elements available on asteroids are present on the Moon, and in some cases they are easier to access in terms of concentrated ore deposits. Although delta V requirements are higher to lift materials off the Moon, its much closer to where its needed in a cislunar economy. Trips out to a NEA would take a long time with current propulsion systems. In addition, he thinks mining NEAs would be an “operational nightmare” as most of these bodies are loose rubble piles of rocks and pebbles with irregular surfaces and very low gravity. This makes it hard to “land” on the asteroid, or difficult to capture and manipulate them. In an email I asked him if he was aware of SHEPHERD, a concept for gentle asteroid retrieval with a gas-filled enclosure which SSP covered in a previous post, but he had not heard of it. TransAstra’s Queen Bee asteroid mining spacecraft has a well thought out capture mechanism as well, although this concept like SHEPHERD are currently at very low technology readiness levels.

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SHEPHERD-Fuel variant harvesting ice from a NEA and condensing it into liquid water in storage tanks, then subsequent separation into hydrogen and oxygen (top). These tanks become the fuel source for a self-propelling tanker block (bottom) which can be delivered to a refueling rendezvous point in cislunar space. Credits: Concept depicted by: Bruce Damer and Ryan Norkus with key design partnership from Peter Jenniskens and Julian Nott

Cannon also makes the point that there is very little mass in the accessible NEAs when compared to the abundance of elements on the Moon.

“There’s more than enough material for near-term needs on the Moon too, and it’s far closer and easier to operate on.”

Finally, he believes that the Moon would be a better stepping stone to mining the asteroids then NEAs would be. This is because most of the mass in the asteroid belt is located in the largest bodies Ceres and Vesta. Operations for mining on these worlds would be more akin to activities on the Moon then on near-Earth asteroids.

asteroid-nasa-2011-09-29
Image of Vesta taken from the NASA Dawn spacecraft. Credit: NASA/JPL

What about moving a NEA to cislunar space as proposed by NASA under the Obama Administration with the Asteroid Redirect Mission? Paul Sutter, an astrophysicist at SUNY Stony Brook and the Flatiron Institute, investigates this scenario and suggests that at least the argument for these asteroids being too far away might be mitigated by this approach, although it would take a long time to retrieve them using solar electric propulsion, as recommended in the article. The trip time might be reduced with advanced propulsion such as nuclear thermal rockets currently under investigation by NASA.

It should be noted that TransAstra has both bases covered. They are working on innovations such as their Sun Flower™ power tower for harvesting water at the lunar poles as well as the company’s Apis™ family of spacecraft for asteroid capture and mining of NEAs.

Conceptual illustration of TransAstra’s Sun Flower™ power towers collecting solar energy above a permanently shadowed region on the Moon to provide power for ice mining operations. Credits: TransAstra Corp.

Update 28 August 2021: Take a deep dive into TransAstra’s future plans with Joel Sercel interviewed by Peter Garretson, Senior Fellow in Defense Studies at the American Foreign Policy Council podcast Space Strategy.