A cylindrical, spin gravity space settlement constructed from asteroid rubble like that from the Near Earth Asteroid Bennu. The regolith provides radiation shielding contained by a rigid container beneath the solar panels. The structure is spun up to provide artificial gravity for people living on the inner surface. Credits: Peter Miklavčič et al.*
Scientists and engineers* at the University of Rochester have conceived of an innovative way to capture a Near Earth Asteroid (NEA) and construct a cylindrical space colony using it’s regolith as shielding. In a paper in Frontiers in Astronomy and Space Sciences they propose a spin gravity habitat called Bennu after the NEA of the same name. Readers will recall that NASA’s OSIRIS-REx spacecraft launched in September 2016, traveled to Bennu, collected a small sample in October 2018 and is currently in transit back to Earth where the sample return capsule will reenter the atmosphere and parachute down in Utah later this year.
Near Earth Asteroid Bennu imaged by the spacecraft OSIRIS-REx. Credit: NASA Goddard Space Flight Center
It would be ideal if an asteroid could be hollowed out for radiation shielding and spun up to create artificial gravity. However, it is shown in this paper that this would not work for larger solid rock asteroids because they don’t have the tensile strength to withstand the rotational forces and smaller rubble pile asteroids (like Bennu) would fly apart because they are too loosely conglomerated.
The problem is solved by containing the asteroid in a carbon fiber collapsible scaffolding that initially has the same radius of the asteroid. As the container is spun up, the centrifugal force will cause the disintegrating rubble to push open the expandable cylinder to its final diameter.
“…a thick layer of regolith is created along the interior surface of this structure which forms a shielded interior volume that can be developed for human occupation.”
The mechanism to initiate the rotation of the structure is interesting. Solar arrays on the outer surface would power mass driver cannons which eject rubble tangentially exerting torque to produce spin.
Detailed engineering analysis and simulations are performed to calculate the stresses on a Bennu sized asteroid to create a cylindrical space colony 3 kilometers in diameter. This structure would have a shielded livable space of 56 square kilometers, an area roughly equivalent to Manhattan.
The authors conclude that the physics of harvesting small asteroids and converting them into rotating space settlements is feasible. They note that this approach would cost less and be easier from an engineering standpoint then fabrication of classic O’Neill cylinders. Concepts for asteroid capture and utilization have already been covered on SSP such as TransAstra’s Queen Bee and SHEPHERD.
The University of Rochester News Center provided a good write up of the paper last December.
* Authors of cited paper: Miklavčič PM, Siu J, Wright E, Debrecht A, Askari H, Quillen AC and Frank A – (2022) Habitat Bennu: Design Concepts for Spinning Habitats Constructed From Rubble Pile NearEarth Asteroids. Front. Astron. Space Sci. 8:645363. doi: 0.3389/fspas.2021.645363
Artist’s rendering of a farming settlement on Mars. Credits: HP Mars Home Planet Rendering Challenge via International Business Times.
Space settlement will eventually require space farming to feed colonists and to provide life support. It’s clear that we will replicate our biosphere wherever we go. In that spirit, Bryce L. Meyer envisions Mars as the breadbasket of the outer solar system. In a presentation at Archon 45, a science fiction and fantasy convention held annually by St. Louis area fans, he makes the case for why the fourth planet would be the ideal spot to grow crops and feed an expanding population as part of the roadmap to agriculture in space.
Carbon dioxide and subsurface water ice are plentiful on Mars, critical inputs for crop photosynthesis. There is also evidence of lava tubes there which could provide an ideal growing environment protected from radiation, micrometeorite bombardment and temperature extremes. The regolith should provide good nutrients and there is already research on methods to filter out perchlorates, a toxic chemical compound in the Martian soil.
Image of Lava tubes on the surface of Mars as photographed by ESA’s Mars Express spacecraft. Credits: ESA/DLR/FU Berlin/G Neukum / NewScientist
Another advantage that Mars holds as a food production hub for the asteroids and beyond is its placement further out in the solar system. Since it is higher up in the sun’s gravity well, Meyer calculates that it would take less than 43% of the fuel needed to transport goods from Mars outward than from Earth. He even suggests that with its lower gravity and recent advancements in materials research, a space elevator at Mars could be economically feasible to cheaply and reliably transport foodstuff off the planet.
Meyer keeps a webpage featuring space agriculture, terraforming, and closed cycle microgravity farming where he poses the question “Why settle space?” I like his answer: “Trillions of Happy Smiling Babies!!!”
Basic input/output diagram of an environmental control and life support system like what would be expected in a space farm. Credits: Bryce L. Meyer
Meyer is the founder and CEO of Cyan React, LLC, a startup that designs compact photobioreactors and provides expertise in closed-cycle farming and life support especially for space settlement and space habitats. He is also a National Space Society Space Ambassador doing his part to educate the public about the potential benefits to humanity through the use of the bountiful resources in space. In a presentation at this year’s International Space Development Conference, he describes his research on bioreactors explaining how settlers will grow food and recycle waste sustainably on the high frontier.
Diagram depicting the flow of materials in a closed space farm habitat utilizing bioreactors. Credits: Bryce L. Meyer
Complete closure and stability of an environmental control and life support system (ECLSS) is challenging and not without limitations. As launch and space transportation costs come down in the near future and off-Earth supply chains become more reliable, complete closure will not be required at least initially. In situ resource utilization will provide replacement of some ECLSS consumables where available for colonists to live off the land. As missions go deeper into space reaching the limits of supply chain infrastructure and even out to the stars, closure of habitat ECLSS and resource planning will become more important. Meyer has done the math for farms in space to provide food and air for trillions of smiling babies…and their families as they move out into the solar system.
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
Conceptual illustration of Mag Mell, a rotating space settlement in the asteroid belt in orbit around Ceres – grand prize winner of the NSS Student Space Settlement Design Contest. Credits: St. Flannan’s College Space Settlement design team*
In this post I summarize a few selected presentations that stood out for me at the National Space Society’s International Space Development Conference 2022 held in Arlington, Virginia May 27-29.
First up is Mag Mel, the grand prize winner of the NSS Student Space Settlement design contest, awarded to a team* of students from St. Flannan’s College in Ireland. This concept caught my eye because it was in part inspired by Pekka Janhunen’s Ceres Megasatellite Space Settlement and leverages Bruce Damer’s SHEPHERD asteroid capture and retrieval system for harvesting building materials.
The title Mag Mell comes from Irish mythology translating to “A delightful or pleasant plain.” These young, bright space enthusiasts designed their space settlement as a pleasant place to live for up to 10,000 people. Each took turns presenting a different aspect of their design to ISDC attendees during the dinner talks on Saturday. I was struck by their optimism for the future and hopeful that they will be representing the next generation of space settlers.
Robotically 3D printed in-situ, Mag Mell would be placed in Ceres equatorial orbit and built using materials mined from that world and other bodies in the Asteroid Belt. The settlement was designed as a rotating half-cut torus with different angular rotation rates for the central hub and outer rim, featuring artificial 1G gravity and an Earth-like atmosphere. Access to the surface of the asteroid would be provided by a space elevator over 1000 km in length.
* St. Flannan’s College Space Settlement design team: Cian Pyne, Jack O’Connor, Adam Downes, Garbhán Monahan, and Naem Haq
Conceptual illustration of a habitat on Mars constructed from self-replicating greenhouses. Credits: GrowMars / Daniel Tompkins
Daniel Tompkins, an agricultural scientist and founder of GrowMars, presented his Expanding Loop concept of self replicating greenhouses which would be 3D printed in situ on the Moon or Mars (or in LEO). The process works by utilizing sunlight and local resources like water and waste CO2 from human respiration to grow algae for food with byproducts of bio-polymers as binders for 3D printing blocks from composite concretes. Tompkins has a plan for a LEO demonstration next year and envisions a facility eventually attached to the International Space Station. He calculates that a 4000kg greenhouse could be fabricated from 1 year of waste CO2 generated by four astronauts. An added bonus is that as the greenhouse expands, an excess of bioplastic output would be produced, enabling additional in-space manufacturing.
Diagram depicting GrowMars Expanding Loop algae growing process to create greenhouse blocks and byproducts such as proteins and fertilizer. Credits: GrowMars / Daniel Tompkins.Illustration of a portion of the Spacescraper tethered ring from the Atlantis Project. Credits: Phil Swan
Phil Swan introduced the Atlantis Project, an effort to create a permanent tethered ring habitat at the limit of the Earth’s atmosphere, which he calls a Spacescraper. The structure would be placed on a stayed bearing consisting of two concentric rings magnetically attached and levitated up to 80 km in the air. In a white paper available on the project’s website, details of the force vectors for levitation of the device, the value proposition and the economic feasibility are described. As discussed during the talk at ISDC, potential applications include:
Electromagnetic launch to space
Carbon neutral international travel
Evacuated tube transit system
Astronomical observatories
Communication and internet
Solar energy collection for electrical power
Space tourism
High rise real estate
Phil Swan will be coming on The Space Show June 21 to provide more details.
Conceptual illustration of a Mars city design with dual centrifuges for artificial gravity. Credits: Kent Nebergall
Finally, the Chair of the Mars Society Steering committee and founder of MacroInvent Kent Nebergall, gave a presentation on Creating a Space Settlement Cambrian Explosion. That period, 540 million years ago when fossil evidence goes from just multicellular organisms to most of the phyla that exist today in only 10 million years, could be a metaphor for space settlement in our times going from extremely slow progress to a quick expansion via every possible solution. Nebergall suggests that we may be on the verge of a similar growth spurt in space settlement and proposes a roadmap to make it happen this century.
He envisions three settlement eras beginning with development of SpaceX Starship transportation infrastructure transitioning to robust cities on Mars with eventual para-terraforming of that planet. He also has plans for how to overcome some of the most challenging barriers – momentum and money. Stay tuned for more as Kent has agreed to an exclusive interview on this topic in a subsequent post on SSP as well as an appearance on The Space Show July 10th.
Illustration showing concept of operations of the RedWater mining system for water extraction on Mars developed by Honeybee Robotics. Credits: Mellerowicz et al. via New Space
The editorial in the latest issue of New Space, coauthored by two of SSP’s favorite ISRU stars, Kevin Cannon and George Sowers, describes the dawning age of space resource utilization. Cannon, who guest edits this issue, and Sowers are joined by the rest of the leadership team of the graduate program in Space Resources at the The Colorado School of Mines: Program Director Angel Abbud-Madrid and professor Chris Dreyer. The program, created in 2017, has over 120 students currently enrolled. These are the scientists, engineers, economists, entrepreneurs and policymakers that will be leading the economic development of the high frontier, creating the companies and infrastructure for in situ resource utilization that will enable affordable and prosperous space settlement.
How can regolith on the Moon and Mars be refined into useful building materials? What are the methods for extracting water and oxygen from other worlds for life support systems and rocket fuel? Is it legal to do so? Will private property rights be granted through unilateral legislation? What will space settlers eat? The answers to all these questions and more are addressed in this issue, many of the articles free to access.
One of my favorite pieces, the source of this post’s featured image, is on the RedWater system for harvesting water on Mars. This technology, inspired by the proven Rodwell system in use for sourcing drinking water at the south pole, was developed by Honeybee Robotics, just acquired by Blue Origin earlier this year. End-to-end validation of the system under simulated Mars conditions demonstrated that water could be harvested from below an icy subsurface and pumped to a tank up on the surface.
We need to start thinking about these technologies now so that plans are ready for implementation once a reliable, affordable transportation system comes on line in the next few years led by companies such as SpaceX and others. Sowers has been working on thermal ice mining on cold worlds throughout the solar system for some time, predicting that water will be “the oil of space”. Cannon has been featured previously on SSP with his analytical tools related to lunar mining, the Pinwheel Magma Reactor for synthetic geology and plans for feeding millions of people on Mars.
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.
A fully autonomous self replicating factory in space requires significant advancements in artificial intelligence, robotics, and other fields. Such facilities are mainly theoretical at this point and may not be feasible for many decades. But if humans could “guide” the operation remotely via computer control, a colony on the Moon could be started relatively soon. This could be the proving ground for establishing such facilities on other worlds which Shubov believes could be set up on Mercury, Mars and in the Asteroid Belt eventually leading to exponential growth allowing humanity to expand out into the solar system and beyond. He suggests that rather then using the usual definition of self-replication in which a factory would make a duplicate copy of itself, until this capability is realized, a better figure of merit would be the “doubling time”. This is how long it takes to double the facility’s mass, energy production, and machine production.
I reached out to Dr. Shubov about this article and discovered that he has been busy with a variety of scholarly papers on several technologies needed for space settlement. He agreed to a wide ranging interview via email about these topics and his vision of our future in space.
SSP: Thank you Dr. Shubov for taking the time for this interview. With respect to your work on Guided Self Replicating Factories (GSRF), there are already companies developing semiautonomous robots for in situ resource utilization on other worlds. OffWorld, Inc. states that “We envision millions of smart robots working under human supervision on and offworld, turning the inner solar system into a better, gentler, greener place for life and civilization.” Their business model is focused on developing a robotics platform for mining and construction on Earth, then leveraging the technology for use in space. Do you think this is a good approach to get started?
MS: Thank you Mr. John Jossy for taking interest in my work!
In my opinion, remotely guided robots will be very effective for construction of a colony on the Moon. These robots could be guided by thousands of remote operators on Earth. They would be linked to Earth’s Internet via Starlink which is already being deployed by Elon Musk via SpaceX. Starlink will consist of thousands of satellites linked by lasers and providing broadband Internet on Earth. About 1,646 satellites are already orbiting the Earth.
Hopefully, it would be possible to produce [an] Earth-Moon Internet Connection of about a Terabit per second. That would enable people on Earth to remotely operate hundreds of thousands of robots.
Using these robots on Asteroids and other planets of Solar System will be much more difficult due to low bandwidth and high delay of communication. For example, latency of communication between Earth and Mars is 4 to 21 minutes.
SSP: Obviously, establishing outposts on other worlds where astronauts could teleoperate robots to build a GSRF would eliminate the latency problem, which you address in your paper.
You’ve envisioned four elements of a GSRF: an electric power plant, a material production system (ore mining, beneficiation, smelting), an assembly system in which factory parts are shaped and fabricated, and a space transportation system. With respect to the space transportation system you cover both launch vehicles and in-space propulsion systems. The space transportation element of a GSRF, although vital for its implementation, seems to be an external part of the system. In fact, you stated that “Initially, spaceships will be built on Earth. Fuel for refueling spaceships will be produced in space colonies from the beginning.” So, when calculating the doubling time of a GSRF, we are not including the production of space transportation systems, correct?
MS: In my opinion, [the] space transportation system may become part of GSRF at later stages of development. How soon space transportation becomes a part of GSRF depends on the speed of development of different technologies.
If inexpensive space launch from Earth becomes available, then there will be less reliance on self-replication and more reliance on transportation of materials from Earth. In this case, space transportation system will not be part of GSRF for a long time.
If rapid growth of a Space Colony by utilization of in situ resources is possible, then many elements of space transportation system would be produced at the colony. In this case, [the] space transportation system will become a part of GSRF relatively soon.
SSP: You suggest that an important product produced by a GSRF in the Asteroid Belt would be platinum group metals to be delivered to Earth, and that they would help finance expansion of space colonization. Some space resource experts, including John C. Lewis, believe that “…there is so vast a supply of platinum-group elements in the NEA [Near Earth Asteroids] … that exploiting even a tiny fraction of them would cause the market value to crash, bringing to an end the economic incentive to mine and import them.” Some suggest the market for these precious metals may be in space not on Earth. When you say “delivered to Earth” what markets were you envisioning to generate the profits needed to finance the GSRF?
MS: In my opinion the main applications of platinum group metals would be in industry. First, PGM are very important as chemical reaction catalysts. In particular, platinum is used in hydrogen fuel cells and iridium is a catalyst in electrolytic cells. It is likely that demand for platinum, iridium and other PGM will grow along with hydrogen economy. Second, platinum and palladium is used in glass fiber production.
Third, Iridium-coated rhenium rocket thrusters have outstanding performance and reusability. Rhenium is also used in jet engines. These thrusters will also provide a market for iridium and rhenium metals.
SSP: As the need for PGM grows exponentially in the future, especially with energy and battery production needs on Earth in the near future, the environmental impacts of mining these materials on Earth may be another reason to source these materials off world.
Mining water to produce hydrogen for rocket fuel is a theme throughout your writings. In a paper submitted to the arXix.org server last month entitled Feasibility Study For Hydrogen Producing Colony on Mars, you propose that a technologically mature Martian factory could produce and deliver at least 1 million tons of liquid hydrogen per year to Low Earth Orbit. Does placing a hydrogen production facility on Mars for fuel used in near-Earth space make sense from a delta-v perspective? You acknowledge that initially it will be cheaper and easier to access the Moon’s polar ice to produce hydrogen. But in the long term, Near Earth Asteroids (NEA) or even the Asteroid Belt are easier to access and they include CI Group carbonaceous chondrites which contain a high percentage (22%) of water. Can you reconcile the economics of sourcing hydrogen on Mars over NEAs?
MS: Delivery of Martian hydrogen into the vicinity of Earth may be necessary only when the space transportation technology is relatively mature. In particular, as I mention in my work, Lunar ice caps contain between 48 million and 73 million tons of easily accessible hydrogen. Until at least 16 million tons of Lunar hydrogen is used, hydrogen from other sources would not be needed.
As I calculate in my work, delta-v for transporting hydrogen from Low Mars Orbit to LEO is 3.5 km/s accomplished by rocket engines plus about 3.2 km/s accomplished by aerobreaking. This would be economic if vast amounts of electric energy will be produced on Mars easier than on asteroids. An important and renewable resource on Mars is the heat sink in the form of dry ice. This may enable production of vast amounts of electric energy by nuclear power plants.
Even if delivery of hydrogen from Low Mars Orbit to Earth turns out to be economically infeasible, hydrogen depots in near-Mars deep space would still play a very important role in transportation to and from Asteroid Belt as well as [the] Outer Solar System.
SSP: Your first choice of a power source for the colony on Mars is an innovative heat engine utilizing dry ice harvested from the vast cold reservoirs at the planet’s polar caps. You suggest that the initial heat source for this sublimation engine be a nuclear reactor. Why not simply use the nuclear reactor to produce electricity? Nuclear reactors coupled to high efficiency Stirling engines for electricity generation like NASA’s Kilopower project have very high power density per unit weight and the technology will be relatively mature soon. Your second choices are solar and wind which are not as reliable as a nuclear power source, especially with reduced solar flux at Mars’s orbit and the problem caused by dust in the atmosphere. Why was a more mature nuclear power technology for direct electricity production not considered?
MS: Thank you. As I understand now, a regular nuclear reactor with a heat engine using water or ammonia as a working fluid is the best choice for energy production on Mars. Dry ice should only be used as a heat sink and not as working fluid. Given the very low temperature and ambient pressure of Martian dry ice, it is likely that power plants will have thermal efficiency of at least 50%.
Almost all components of Martian power stations can be manufactured from in situ resources. Only the reactors themselves and the nuclear fuel will have to be delivered from Earth.
SSP: A booming space transportation economy will need cryogenic fuel depots to store hydrogen for rocket fuel in strategic locations throughout the inner solar system. You’ve got this covered in your recent paper Hydrogen Fuel Depot in Space. Some start ups like Orbit Fab have already started work in this area, albeit on a smaller scale, and United Launch Alliance integrated cryogenic storage into their Cislunar-1000 plans a few years back, but this initiative seems to have slowed down due to delays in ULA’s next generation Vulcan launch vehicle. In this paper you calculate the required energy to refrigerate hydrogen in one smaller (400 tons) and another larger (40,000 tons) depot. In both cases, a sun shield is required to block sunlight to prevent boil off. You don’t mention the method of power generation to provide energy for the refrigeration units. Could the sun shield have a dual use function by incorporating photovoltaic solar cells on the sun facing side to generate electricity to power the refrigeration system?
Diagram depicting a cryogenic liquid hydrogen storage depot with 40,000 ton capacity. Credits: Mikhail Shubov
MS: Power for the refrigeration system will be provided by an array of solar cells placed on the sun shield. As I mention in my work, the 400 ton depot requires 80 kW electric power for the refrigeration system, while the 40,000 ton depot requires 840 kW electric power. This power can be easily provided by photovoltaic arrays.
SSP: SpaceX has proven what was once believed impossible: that rockets could be reused and that turnaround times and reliability could approach airline type operations. Although we are not there yet, costs continue to come down. In your paper entitled Feasibility Study For Multiply Reusable Space Launch System you calculate that with your proposed system in which the first two stages are reusable and the third stage engine can be returned from orbit, launch costs could be reduced to $300/kg. Musk is claiming that with the projected long term flight cadence, eventually Starship costs could be as low as $10/kg. Even if he is off by a factor of 10 that is still lower than your figure. What advantages does your system offer over Starship?
MS: The main advantage of the Multiply Reusable Space Launch System is the relatively light load placed on each stage. As I mention on p. 10, the first stage has delta-v of 2.6 km/s and the second stage has delta-v of 1.85 km/s. The engines have high fuel to oxidizer ratio and a low combustion chamber temperature of 2,100oC. These relatively light loads on the rocket airframes and engines should make these rockets multiply reusable similar to airliners. The launch system should be able to perform about 300 space deliveries per year.
Hopefully Elon Musk would succeed [in] reducing launch costs to at least $100 per kg. Unfortunately, many previous attempts at drastic reduction of launch costs did not succeed. Hence, we may not be sure of Starship’s success yet.
SSP: You state in several of your papers that:
“A civilization encompassing the whole Solar System would be able to support a population of 10 quadrillion people at material living standards vastly superior to those in USA 2020. Colonization of the Solar System will be an extraordinary important step for Humankind.”
Why do you think that colonization of the solar system is important for humanity and when do you think the first permanent settlement will be established on the Moon or in free space? Here I use the National Space Society’s definition of a space settlement:
‘ “A space settlement” refers to a habitation in space or on a celestial body where families live on a permanent basis, and that engages in commercial activity which enables the settlement to grow over time, with the goal of becoming economically and biologically self-sustaining as a part of a larger network of space settlements. “Space settlement” refers to the creation of that larger network of space settlements. ‘
MS: In my opinion colonization of Solar System will bring unlimited resources and material prosperity to Humankind. The human population itself will be able to grow by the factor of a million without putting a strain on the available resources.
As for the time-frame of establishment of human settlements on the Moon and outer space, I have both optimistic and pessimistic thoughts. On one hand, Humankind already possesses technology needed to establish rapidly growing space settlements. This means that Solar System colonization can start at any time. On the other hand, such technology already existed in 1970s. This technology is discussed in Gerard K. O’Neill’s 1976 book “The High Frontier: Human Colonies in Space”. Thus, space colonization can be indefinitely delayed by the lack of political will. Hopefully space colonization will start sooner rather then later.
Credits: Gerard K. O’Neill / Space Studies Institute Press
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.”
A tongue-in-cheek Freedom Engineering poster encouraging space settlers to produce oxygen through plant growth as an alternative to dependency on centralized oxygen production facilities. Credits: Charles Cockell
At the 24th Annual International Mars Society Convention held October 14 – 17, Dr. Charles Cockell, professor of Astrobiology in the School of Physics and Astronomy at the University of Edinburgh, gave a talk on what he calls Freedom Engineering. His viewpoint was also published in a paper via the journal Space Policy in August of 2019. Cockell makes the case that due to the extreme constraints imposed by the laws of physics on living conditions in space settlements, freedom of movement will necessarily be restricted. Such conditions could be exploited by tyrannical governments to limit social, political and economic freedoms as well. To address these concerns Cockell suggests that colony designers utilize proactive engineering measures in planning off Earth communities to maximize liberty in the space environment. For example, rather then one centralized oxygen production facility or method that may be leveraged by a despot to control the population, it is suggested that settlements be designed with multiple facilities distributed widely and if possible, other types of oxygen production (e.g. greenhouses) be employed to minimize the chance of monopolization.
This engineering philosophy raised many questions among colleagues of mine so I reached out to Dr. Cockell for an interview via email to provide answers. He graciously agreed and I’m very grateful for his responses.
SSP: How is Freedom Engineering different from standard engineering practices of designing for redundancy to prevent single point failure?
CC: There is a strong overlap. For example, if you want redundancy, you multiply oxygen production. That would also be a desired objective to minimize the chances of monopolistic control over oxygen. So often the objectives are the same. However, I suggest that freedom engineering is a specific focus on engineering solutions that cannot be used to create coercive extraterrestrial regimes, which is not always the same as redundancy. For example, we might minimize the use of cameras and audio devices to monitor habitats for structural integrity, an objective consistent with general engineering demands, but potentially antithetical to human freedoms.
SSP: Since the added costs are significant and we may not be able to follow these practices initially, how do we get around the problems you mention after being on the Moon a decade or two? Wouldn’t the forces of tyranny have already won?
CC: Liberty is never cheap in resources and human effort. You can take a cost-cutting approach and hope that tyrannical regimes don’t take hold in a settlement or you can plan before hand to minimize their success, even if that involves more cost. However, as many freedom engineering solutions are compatible with redundancy, it is not necessarily the case that introducing measures like maximizing oxygen production and spacesuit manufacture motivated by considerations on liberty would add significantly to a cost already incurred by ensuring redundancy.
Liberty is never cheap in resources and human effort.
SSP: How do we avoid centralized control of transportation? Will we have two or more landing pads, several sets of rockets? – e.g., Musk, Bezos, and ULA?
CC: I would say that maximizing the number of entities with transportation capabilities is a good idea. Here too, we would want to achieve this for redundancy, but it would also reduce the chances of monopolization and the isolation of a settlement (particularly if leaving the settlement can only be achieved with one provider). This could also include multiplying the physical number of rocket launch and arrival points.
SSP: There are always non-redundant systems, which you acknowledge. At some level there are critical infrastructures that cannot be made redundant because then we get into an infinite loop. If a tyrannical power wanted to control everything on the Moon, for example, that is where they would focus their control. Can you comment?
CC: That’s true. It goes without saying that, as on Earth, a determined despot with enough support can find ways to take over a society. However, as the framers of the US Constitution understood, if you can introduce enough checks and balances you can make tyranny an outcome that requires many of those to fail. You reduce the risk. So by minimizing the number of single point controls in an extraterrestrial society you never eliminate the chances of tyranny, but you reduce the number of options open to those with tyrannical tendencies.
It goes without saying that, as on Earth, a determined despot with enough support can find ways to take over a society.
SSP: How would a tyrannical off-Earth settlement get its citizens when moving to such a settlement would seem like a terrible idea?
CC: It’s true that an overtly tyrannical settlement may eventually find it difficult to recruit people and might therefore fail. One might hope that this would be a feedback loop that would discourage tyranny in space. However, when building free government[s], it’s a good idea to assume the worse to achieve the best, i.e. assume that people will attempt to, and can, create a tyranny, and then build a system that minimizes this possibility. It’s also worth pointing out that once people are in a settlement, they will be physically isolated under some governance power. Just as it isn’t trivial to remove a tyranny on Earth that has a population corralled under it once it is established, it may not be easy to free a settlement once it has a population under its control. It is worthwhile to attempt to design societies that avoid this possibility from the beginning.
SSP: Would a space settlement economy with multiple competing companies providing essential needs such as life support, obviate the requirement for engineering redundancy since it would be more difficult for a tyrannical government to take over all the means of production?
CC: Yes, I think in many ways multiple competing companies is a form of redundancy – providing many conduits for production and minimizing single points of control or failure. Maximizing productive capacity is essential. I would mandate some basic level of oxygen production capability, for example, that any settlement must be capable of producing to keep people alive, and then try and stimulate a private market in fashionable oxygen machines of various kinds, different oxygen production methods etc. Of course, one should not be utopian. A coercive monopoly could still control a lot of this, but in general the more entities that produce vital resources, the more likely real choice can emerge in some form.
SSP: One reasonable measure that can be taken that doesn’t fall under normal engineering approaches is standardizing data transparency. It might make sense that it should be a matter of public record, and easily assessable, the records of who does what with vital resources and how activities that seriously impact human safety are managed. This can be done without compromising anyone’s intellectual property. The full light of day can be good protection especially when used proactively, and establishing such standards would head off the opportunity to wave things away as bias or smear campaigns. Open-source approaches to data are already a big thing for all the space agencies and may be the best course of action. Do you have an opinion on this philosophy?
CC: I think this is essential. The freedom engineering approach I suggest is just one mechanism for reducing coercive governance, but a free society is constructed from many other needs. In some of my previous papers I have discussed exactly this – the need for transparency in information about oxygen production, who is funding it, and how etc. A general culture of openness is necessary. There may be some novel approaches such electing members of the settlement by lot to take part in meetings to do with oxygen or water production, for instance, and write public reports. Corporations will find all this very annoying of course, but the wider culture of liberty will be enhanced by a very ‘leaky’ society with respect to information. Other essential things are a free press (even if that is just informal lunar or Martian newspapers), transparency in elections for running the settlement, and perhaps maximum terms on people involved in health and safety tasks to create fluidity in the network of officialdom that oversees the potentially large number of health and safety concerns with respect to radiation, dust, production of essential items.
Corporations will find all this very annoying of course, but the wider culture of liberty will be enhanced by a very ‘leaky’ society with respect to information.
Diagram depicting the market sectors of the nascent in-space economy. Credits: Erik Kulu / Factories in Space
Erik Kulu, a Senior Systems Engineer in the satellite industry, has a passion for emerging technologies…especially those in the in-space manufacturing field. He’s created the largest public database of companies active in the emerging in-space economy. Called Factories in Space, it tracks companies engaged in microgravity services, space resources, in-space transport services, the economies of LEO, cislunar space, the Moon and much more.
Kulu provides an overview of commercial microgravity applications for both terrestrial and in-space use. His listing and analysis of potential business ventures provides a comprehensive summary of unique profitable commodities manufactured in microgravity, including fiber optics, medical products, exotic materials and many more.
Breakdown of the in-space manufacturing sector of the space economy. Credits: Erik Kulu / Factories in Space
“This is the missing piece to speed up development for the exciting Star Trek-like future. I believe in-space manufacturing will be the kickstarter and foundation.”
In a recent industry survey examining the commercial landscape of space resources in 2021, Kulu renders a statistical breakdown of the currently evolving development stages of in-space manufacturing companies, levels of funding by market sector, timing of company founding and geographical location of the main players. His analysis shows a marked increase in the formation of companies from 2016 – 2018 dropping off over the last 3 years.
Prominent founding peak of space resource companies in 2018 with drop at end of the last decade. Credits: Erik Kulu / Factories in Space
I asked Kulu about what he thought caused the downward taper because it seemed to have started before the COVID-19 pandemic, and so was probably unrelated. He agreed, and offers this explanation:
“Primarily, I think the decline is a mix of following:
There was a boom of some sorts, which has slowed down in terms of very new startups. Similar graphs [indicate the same trend] for nanosatellite, constellation and launcher companies. Funding boom is continuing though.
As many of those space fields do not have obvious markets, some potential new actors might be in wait mode, because they want to see what happens financially and technically to existing companies.
Startups could be in stealth mode or very early stage and as such I have not become aware of them yet. They will likely partially backfill.”
“While there was a decline, I forecast Starship and return to the Moon will kick off another wave in about 2-3 years.”
Kulu also tracks NewSpace commercial satellite constellations, small satellite rocket launchers and NewSpace funding options through his sister site NewSpace Index. But he doesn’t stop there. The world’s largest catalog of nanosatellites containing over 3200 nanosats and CubeSats can be found in his Nanosats database.
Learn more about how Erik Kulu got started tracking the in-space economy in this interview from earlier this year over on Filling Space. And be sure and tune in live to The Space Show next month when I cohost with David Livingston for his debut appearance, exact date to be determined. You can call the show and ask Erik questions directly. Check TSS Newsletter, updated weekly, for the show date once its set. This post will be updated when the schedule is finalized, so readers can check back here as well.
