SSP has addressed the gravity prescription (GRx) in previous posts as being a key human factor affecting where long term space settlements will be established. It’s important to split the GRx into its different components that could effect adult human health, child development and reproduction. We know that microgravity (close to weightlessness) like that experienced on the ISS has detrimental effects on adult human physiology such as osteoporosis from calcium loss, degradation of heart and muscle mass, vision changes due to variable intraocular pressures, immune system anomalies…the list goes on. But many of these issues may be mitigated by exposure to some level of gravity (i.e. the GRx) like what would be experienced on the Moon or Mars. Colonists may also have “health treatments” by brief exposures to doses of 1G in centrifuge facilities built into the settlements if the gravity levels in either location is found to be insufficient. We currently have no data on how human physiology would be impacted in low gravity (other then microgravity).
The most important aspect of the GRx with respect to space settlement relates to reproduction. How would lower gravity effect embryos during gestation? Since humans have evolved in 1G for millions of years, a drastic change in gravity levels during pregnancy could have serious deleterious effects on fetal development. Since fetuses are already suspended in fluid and can be in any orientation during most of their development, it may be that they don’t need anywhere near the number of hours of upright, full gravity that adults need. How lower gravity would affect bone and muscle growth in young children is another unknown. We just don’t know what would happen without a clinical investigation which should obviously be done first on lower mammals such as rodents. Then there are ethical questions that may arise when studying reproduction and growth in higher animal models that could be predictive of human physiology, not to mention what would happen during an accidental human pregnancy under these conditions.
Right now, we only know that 1G works. If space settlements on the Moon or Mars are to be permanent and sustainable, many space settlement advocates believe they need to be biologically self-sustaining. Obviously, most people are going to want to have children where they establish permanent homes. If the gravity of the Moon or Mars prevents healthy pregnancy, long term settlements may not be possible for people who want to raise families. This does not rule out permanent settlements without children (e.g. retirement communities). They just would not be biologically self-sustaining.
SSP has suggested that it might make sense to determine the GRx soon so that if we do determine that 1G is required for having children in space, we begin to shape our strategy for space settlement around free space settlements that produce artificial gravity equivalent to Earth’s. Fortunately, as Joe Carroll has mentioned in recent presentations, the force of gravity on bodies where humanity could establish settlements throughout the solar system seems to be “quantized” to two levels below 1G – about equal to that of the Moon or Mars. All the places where settlements could be built on the surfaces of planets or on the larger moons of the outer planets have gravity roughly at these two levels. So, if we determine that the GRx for these two locations is safe for human health, we will know that we can safely raise families beyond Earth in colonies on the surfaces of any of these worlds. Carroll proposes a Moon/Mars dumbbell gravity research facility be established soon in LEO to nail down the GRx.
But is there an argument to be made for skipping the step of determining the GRx and going straight to an O’Neill colony? After all, we know that 1G works just fine. Tom Marotta thinks so. He discussed the GRx with me on The Space Show recently. Marotta, with Al Globus coauthored The High Frontier: An Easier Way. The easier way is to start small in low Earth orbit. O’Neill colonies as originally conceived by Gerard K. O’Neill in The High Frontier would be kilometers long in high orbit (outside the Earth’s protective magnetic field) and weigh millions of tons because of the amount of shielding required to protect occupants from radiation. The sheer enormity of scale makes them extremely expensive and would likely bankrupt most governments, let alone be a challenge for private financing. Marotta and Globus suggest a step-by-step approach starting with a far smaller version of O’Neill’s concept called Kalpana. This rotating space city would be a cylinder roughly 100 meters in diameter and the same in length, spinning at 4 rpm to create 1G of artificial gravity and situated in equatorial low Earth orbit (ELEO) which is protected from radiation by our planet’s magnetic field. If located here the settlement does not require enormous amounts of shielding and would weigh (and therefore cost) far less. Kasper Kubica has proposed using this design for hosting $10M condominiums in space and suggests an ambitious plan for building it with 10 years. Although the move-in cost sounds expensive for the average person, recall that the airline industry started out catering to the ultra-rich to create the initial market which eventually became generally affordable once increasing reliability and economies of scale drove down manufacturing costs.
What about all the orbital debris we’re hearing about in LEO? Wouldn’t this pose a threat of collision with a free space settlement given their larger cross-sections? In an email Marotta responds:
“No, absolutely not, I don’t think orbital debris is a showstopper for Kalpana.
… First, the entire orbital debris problem is very fixable. I’m not concerned about it at all as it won’t take much to clean it up: implement a tax or a carbon-credit style bounty system and in a few years it will be fixed. Another potential historical analogy is the hole in the ozone layer: once the world agreed to limit CFCs the hole started healing itself. Orbital debris is a regulatory and political leadership problem, not a hard technical problem.
Second, even if orbital debris persists, the technology required to build Kalpana…will help protect it. Namely: insurance products to pay companies (e.g. Astroscale, D-Orbit, others) to ‘clear out’ the orbit K-1 will inhabit and/or mobile construction satellites necessary to move pieces of the hull into place can also be used to move large pieces of debris out of the way. In fact, I think having something like Kalpana…in orbit – or even plans for something that large – will actually accelerate the resolution of the orbital debris problem. History has shown that the only time the U.S. government takes orbital debris seriously is when a piece of debris might hit a crewed platform like the ISS. Having more crewed platforms + orbital debris will drastically limit launch opportunities via the launch collision avoidance process. If new satellites can’t be launched efficiently because of a proliferation of crewed stations and orbital debris I suspect the very well-funded and strategically important satellite industry will create a solution very quickly.”
To build a space settlement like the first Kalpana, about 17,000 tons of material will have to be lifted from Earth. Using the current SpaceX Starship payload specifications this would take 170 launches to LEO. By comparison, in 2021 the global launch industry set a record of 134 launches. Starship has not even made it to orbit yet, but assuming it eventually will and the reliability and reusability is demonstrated such that a fleet of them could support a high launch rate, within the next 20 years or so there will be considerable growth in the global launch industry. If larger versions of Kalpana are built the launch rate could approach 10,000 per year for space settlement alone, not to mention that needed for rest of the space industry. This raises the question of where will all these launches take place? Are there enough spaceports in the world to support it? Marotta has an answer for this as well. As CEO of The Spaceport Company, he is laying the groundwork for the global space launch infrastructure that will be needed to support a robust launch industry. His company is building distributed launch infrastructure on mobile offshore platforms. Visit his company website at the link above for more information.
Conceptual illustration of a mobile offshore launch platform. Credits: The Spaceport Company
For quite some time there has been a spirited debate among space settlement advocates on what destination makes the most sense to establish the first outpost and eventual permanent homes beyond Earth. The Moon, Mars or free space O’Neill settlements. Each location has its pros and cons. The Moon being close and having ice deposits in permanently shadowed craters at its poles along with resource rich regolith seems a logical place to start. Mars, although considerably further away has a thin atmosphere and richer resources for in situ utilization. Some believe we should pursue all the above. However, only O’Neill colonies offer 1G of artificial gravity 24/7. With so many unknowns about the gravity prescription for human health and reproduction, free space settlements like Kalpana offer a safe solution if the markets and funding can be found to make them a reality.
I met Kent Nebergall during a cocktail reception at ISDC which took place May 27-29. He chairs the Steering Committee for the Mars Society (MS) and gave a fascinating talk Sunday afternoon on Creating a Space Settlement Cambrian Explosion. We had a wide-ranging discussion on some of his visions for space settlement and he agreed to collaborate on this post. We’ll do a deep dive into some of the topics he covered in his talk, which is available on his website at MacroInvent.
In summary, he breaks down some of the key challenges of space settlement and proposes economic models for sustainable growth. His roadmap lays out a series of space settlement architectures starting with a variant of SpaceX Starship used as a building block for large rotating habitats and surface bases for the moon, Mars, and asteroids. Next, he presents his Eureka Mars Settlement design which was entered in the MS 2019 Mars Colony Design Contest addressing every technical challenge. Finally, an elegant system for para-terraforming Martian canyons in multi-layered habitats is proposed, “…with the goal of maximizing species diversity and migration beyond our finite world. We not only preserve and diversify species across biomes, but engineer new species for both artificial and exoplanetary habitats. This is an engine for creating technology and biological revolutions in sequence so that as each matures, a new generation is in place to keep driving expansion across the solar system and beyond.”
Here’s my interview with Kent conducted via email. I hope you enjoy it!
SSP: You created a checklist of the required technologies needed to enable space settlement where each row is sorted by increasing necessity while the columns are sorted by greater isolation from Earth.
Credits: Kent Nebergall
Musk has started to crack the cheap access to space nut and large vehicle launch at upper left with Starship but we’re not there yet. Given that Musk’s timelines always should be taken with a grain of salt, and the challenge of planetary protection (bottom of column 3) could potentially prevent Musk from obtaining a launch license for a crewed mission before scientists have a chance to robotically search for signs of life, what is your estimation of the probability that Humans will land on Mars by 2029, in accordance with your proposed timeline (see below)?
KN: Elon time is real, definitely. My outside analysis implies that SpaceX is using Agile development systems borrowed from the software industry. The benefit of Agile is that technological progress is as fast as humanly possible. The bad news is that it largely ignores things that traditional management styles value, such as being able to predict the date something is really finished. At any rate, my general conclusion is that anything Elon predicts will be off by 43 percent as a baseline, assuming no outside factors are involved. Starship has slid more because the specifications kept changing, much as they did with Falcon Heavy.
We seem to be locked in on the early orbital design, which seems to be purely for getting Starlink 2 satellites in place and providing return on investment while getting the core flight systems refined. It doesn’t need solar panels, crew space, or the ability to stay on orbit more than a day. Crewed Starship may take another few years and use a smaller than expected cabin with a large payload bay. 2029 is the most recent year of a crewed Mars landing from Elon (as of March, 2022). If we allow for Elon Time, we could expect cargo in that launch window. I suspect one vehicle may try to return to prove out that flight range, like return to Earth from deep space. The first mission would largely be watching Optimus Prime robots setting up a farm of solar panels to make fuel for the return trip.
“The irony is that Elon could just pack the ship with Tesla humanoid robots for the first few missions…”
The planetary protection regulatory barrier is quite possible, yes. We just saw the regulatory findings for Bocca Chica. That requires several frivolous preconditions for flight, like writing an essay on historic monuments and accommodating ocelots, which haven’t been seen in the area in forty years. I doubt the capacity of political Simon Says playground games like has been exhausted yet.
What we’ve seen historically is that those who cannot compete will throw up regulatory and legal barriers. However, we’ve also seen that these efforts eventually burn out after a few years. This has been true with paddle wheel river ships, steam ships, railroads, and airlines. It’s playing out with Tesla and the big three domestic automakers now as well. Most of those tricks were already pulled with Falcon 9, so I think that path is largely burned through. I’m nearly certain they will try the planetary protection argument later. We have already seen with the ocelots that they are willing to protect absent species.
The irony is that Elon could just pack the ship with Tesla humanoid robots for the first few missions and build a base while running life searches in the area. The base could be built with nearly the same productivity as a human crew, and the cultural pressure to move humans into it would be quite high if no life is found in the meantime. It would be great marketing for the Tesla robots as well.
SSP: The table seems comprehensive and covers just about everything. Has it changed or been updated in 18 years? I noticed “Spacesuit Lifespan”. Why is this a challenge for space settlement?
KN: The table is fairly solid in terms of subject matter, but I’ve started a project to rebuild it. I only found out recently that NASA’s term for this is RIDGE (Radiation, Isolation, Distance, Gravity and Environment). My slicing into 26 categories is more precise – literally an alphabet of categories.
First, if it were a true “periodic table” analog, it would transpose the columns. But it’s much easier to fit in PowerPoint this way. Second, I have used this principle for other challenge sets and found interesting implications, so I may make a more advanced version in the future with far more depth. I’ll still use this for PowerPoint, though, because it can be read from the back row in under a minute. Third, each “challenge” is actually a family of challenges. There are multiple health problems with microgravity, for example, but one root cause – the absence of gravity. So, while each challenge in the table has many sub-factors, there is a single root cause and a solution that eliminates that cause also eliminates all sub-sets of problems. If a solution cannot fix the root cause, than separate solutions are needed for each child challenge like bone loss.
Spacesuit lifespan for the ISS is an issue because the suits are often older than the station itself. On the moon, the spacesuits picked up abrasive moon dust in the joints and could have eventually lost flexibility or pressure integrity if they’d been used much longer. A Mars suit is in some ways easier because the soil is more weathered and therefore less abrasive. Space settlement hits a standstill if you can’t go outside. Unfortunately, efforts to replace them have cost a billion dollars so far and have just been restarted for an even higher price tag. It seems to be the classic example of doing as little progress as possible while spending as much money as possible. There have been some great technologies developed but there has been no pressure to finish a completed suit. As the old saying goes, “One day, you just have to just shoot the engineer and cut metal”.
At one point, SpaceX outright said, “We can do it.” But NASA showed no interest, and SpaceX apparently didn’t bid on the moon suit designs this time. They have been converting the ascent suit from Dragon to one able to do spacewalks in the 1960’s Gemini sense for launch this year. I wouldn’t be surprised if they develop a moon suit just because they can, and on their own dime. It would be quite embarrassing for all involved, including SpaceX, if we had a 100 tonne payload moon lander capable of holding dozens of people, and not have a single suit capable of letting them leave the ship.
SSP: You mentioned orbital debris being a potential barrier for your plan’s LEO operations and you’ve come up with methods for shielding early orbital habitats, but they may not be effective against larger debris fragments. The X-prize Foundation is considering an award for ideas to solve this problem and there are numerous startups on the verge of addressing the issue. Such a solution would have to be implemented quickly and on a massive scale for your timeline to be achieved. If orbital debris looks like it may still be a problem for larger orbital settlements until they can be established in higher orbits, could your plan be modified to perhaps include debris removal as an economic driver? [SpaceX president and COO Gwynne Shotwell has suggested that Starship could be leveraged to help clean up LEO]
The problem must be sliced up, just as the other grand challenges are sliced up. We need several approaches at once. First, refueling starship is a bit risky, and the risk rises with prolonged exposure to the debris hazard. SpaceX originally wanted to launch the Mars vehicle, then refuel it on orbit over several tanker flights. More recently, they are implying they would fly a tanker up, fill it with several other tankers, then refuel the Mars or Lunar vehicle in one go. This makes a lot more sense. A tanker or depot hit by debris would be a space junk hazard, but it wouldn’t cost lives or science hardware.
We need to de-orbit the largest items, many of which are spent rocket stages. SpaceX has offered to gobble them up with Starship, but that means a lot of delta V in terms of altitude, inclination, elliptical elements, and so on. I could see a sort of penny jar approach where they drop off a satellite, then pick up an old one or two (the satellite and old rocket stage) before returning. Realistically, though, old rocket stages and satellites that haven’t vented every single tank (main and RCS [reaction control system]) will be hazardous to approach.
It seems the best solution would be mass-produced mini-satellites with ion drive and electrodynamic tethers. Each mini-sat would find a spent rocket stage or defunct satellite and add an electrodynamic tether to drag it down using Earth’s magnetic field while also powering an ion engine to assist in de-orbiting. You would have to do a few at a time because the tethers themselves would become a hazard if we had thousands of them cutting through space like razor ribbons.
I could also see a spider robot that would grab larger satellites with propellant still on board, wrap them up like a spider wrapping a bug in silk, and then puncturing the tanks carefully to both refill itself and render the satellite inert. It would then be safe to grab with a Starship or de-orbit with a drag or propellant system [Another concept for debris removal could be Bruce Damer’s SHEPHERD which we covered a year ago. Although originally conceived for asteroid capture, a pathfinder application could be satellite servicing/decommissioning].
We didn’t create the problem in a day, and we can’t solve it quickly either. But we can take an approach of de-orbiting two tons for every ton launched once we have mass produced systems for doing so. Maybe other launch providers can grab defunct satellites with their orbital launch stages before dragging them both into the Pacific.
That said, we can’t get every paint chip and bolt out of orbit this way. We will hit a law of diminishing returns. Anything below that line will require a technology to survive impacts. The pykrete ice shield I proposed could be much smaller, such as just one hexagonal hangar big enough for 2-3 starships in LEO at a time. Once refueled, the craft would go to the much safer L5 point or directly to the moon if that is the destination. Keeping a ring at L5 would not require a massive ice shield or centrifuge habitat to be a useful waystation. But those would be designed into it up front to give room for expansion.
If we decided that a Mars mission had to wait for all the infrastructure I proposed, we’d be in the same trap that Von Braun would have fell into of wanting massive infrastructure before the first crewed lunar mission. You need a balance of infrastructure and exploration to give both meaning.
“We can democratize early if we give some participation method in the initial investments in time, technology, and financing.”
SSP: Musk says he needs 100s of starships to deliver millions of tons of materials to support large cities on Mars by mid-century (his timeline). You’ve created a somewhat more reasonable timeline for Starship round trip logistics for this effort based on Hohmann transfer orbits and Mars orbital launch windows (i.e. every 2 years).
Credits: Kent Nebergall
What will be the economic driver for such an ambitious project besides Musk just “making it so”? I saw later in your presentation that you proposed an initial sponsorship and collectables market followed by MarsSpec competitions. How will these initiatives kickstart sufficient market enthusiasm to support such an enormous fleet of Starships?
KN: It’s a complex topic, and easily a book in itself. To cut to the core of it, any major discovery or invention that is not democratized becomes historic or esoteric rather than revolutionary. Technology revolutions do not take place in particle accelerators any more than music revolutions take place in symphony orchestra pits. Things that don’t impact people constantly are simply curiosities. Even many things taken for granted like GPS and running water are ignored, but they remain transformative. When the furnace filter factory worker sends part of his month’s labor to Mars, we have space settlement. We can democratize early if we give some participation method in the initial investments in time, technology, and financing. But these waves will go from new and novel to basic and ignored rather quickly, and this is especially true if they succeed.
Imagine being a medieval merchant and getting an opportunity to send a bag of grain on a voyage to Cabot or some other explorer. In return you get a rock from the opposite side of the world, a certificate saying what you gave and authenticating what you got back, and a tiny bit of participation in the history of your era that you can share with your children. A decade later, your son is working in a smelting plant in a port city and making hardware for houses in the new world. In another decade your grandchildren are growing crops in Maryland. It’s a bit like that. Each wave will fund and create the industrial and skill base for the next wave before becoming culturally ubiquitous. The last child has no interest in a rock from his Maryland backyard. But to the grandfather living a generation or two beforehand, it may as well be from the moon. The wave of sponsorship, followed by specifications for space-rated products, followed by biological engineering in lower gravity worlds will each create benefits and enthusiasm back on Earth. After that last wave, the economic ecosystem becomes permanently multi-planetary.
Everything else about space is a simple engineering problem. Minds, trends, budgets, and so on are not so well behaved as atoms or heat, but they have a lot of history that we can use to model workable solutions. This is the one I came up with.
“The problem with any grand engineering venture is that every design looks good until it comes in contact with reality.”
SSP: The Eureka Space Settlement concept features dual centrifuges providing artificial gravity equivalent to the Moon and Mars.
Eureka settlement duel centrifuge facility providing lunar gravity on the inner ring and Mars gravity on the outer one. Credits: Kent Nebergall
I like the idea of using variable gravity to study biological effects on plant and mammalian physiology, adapting species to be multi-planetary and prepping for settlements that will need gravity as we move out into the outer solar system, but this can be done more cheaply in LEO or in cislunar space as outlined earlier in your architecture. Why not simplify the Eureka settlement by eliminating the centrifuge and going with normal Mars gravity?
KN: The problem with any grand engineering venture is that every design looks good until it comes in contact with reality. You can’t model every issue up front, and one of the hardest to work out without experience are multi-generational ecosystems. If we build a $100 billion Mars city and the kids have birth defects, we have a huge liability issue and a city that will be turned over to robots or dust.
The advocates assume all will be fine, but they tend to downplay issues. The critics assume all will go poorly, but they never want to venture past the status quo. Reality will be a mixed bag of data points on a bell curve between the two with both unknown threats and opportunities waiting for discovery. This unknown is a big reason for the enthusiasm to try in the first place.
I came up with the steelman methodology by taking all the criticisms and range of danger possibilities and cranking the bell curve values up a few sigma to the nasty side. The idea is that if you can STILL make an affordable design that pays for itself when the universe is coming after you with a hammer, you probably will be fine when the bell curve is realized. You should always have a back-down plan to have surface domes with no centrifuges, or simply use the centrifuges for pregnant mammals and trees that need to fight gravity to have enough limb strength to bear fruit. That said, another beauty of this design is that a Pluto colony or asteroid colony will almost certainly need centrifuges for multigenerational life. Prototyping it on Mars may be overkill for Mars, but perfect for Pluto or Enceladus. This makes it much easier for Mars settlers to think about colonizing the outer solar system. Even the children of our dreams need dreams, after all.
“A space outpost must bring materials to itself, so a system like that without surface outposts or asteroid mining is a dead end.”
SSP: In the proposed first wave of the architecture, rotating settlements are created from Starship building blocks in high orbit to create “…deep space industrial outposts in the O’Neill tradition with a thousand inhabitants each. On the lunar and Martian surface, we simply take a slice of the ring architecture with starships inside as an outpost.” With the amount of investment needed to build the infrastructure to transport materials and people for large settlements on Mars, and given that the biggest grand challenge on your chart is reproduction (which may not be possible in less than Earth’s gravity), why wouldn’t it make more sense to focus efforts on building larger 1G rotating free space settlements where we know having children is possible?
KN: It’s not so much a roadmap of first this structure here, then that one there. It’s a draft set of compatible building standards for everywhere. Think about the standard sizes for bricks, pipes, and wiring and how entire continents use them interchangeably over a hundred years or more. My goal was to lay out what the maximum amount of infrastructure would look like with the minimum number of parts.
There is a false dichotomy between structures like space stations made entirely from material from Earth, and local materials formed with 3D printers that can do everything with complete reliability. Both are impractical extremes, and to some degree strawman designs. Importing everything is prohibitively expensive even with Starship. Conversely, creating structures from random conglomerates of whatever material is at the landing site will be too brittle. By proposing bags that can be made of basalt cloth but that will initially come from Earth, I’m bridging the two extremes. They can be filled with dust, water, sand, or whatever is fine grained enough and can be either sintered or cemented in place. Such structures don’t have to be aligned with absolute precision and can follow soft contours or whatever is needed. You also don’t need four meters of shielding for cosmic rays if you augment it with magnets. They can be scaled in layers or levels as needed, just like bricks or two by four boards are in homes.
A space outpost must bring materials to itself, so a system like that without surface outposts or asteroid mining is a dead end.
Centrifuges for surface settlements are a bit awkward, to be sure. A train system that keeps the floor below you when spinning or de-spinning is a better system at first. Eureka was mainly done with fixed pitch decks just to show that the scale of a centrifuge for a large torus L5 ring could be done on a surface with some clever engineering. My original design goal was to make the cars, car beds, rails, and buildings swappable without stopping the ring rotation. In the same way, the pressure shell has inner and outer walls that can in theory be replaced while the other keeps pressure. It’s probably not necessary, but the goal is to remove all design barriers early in the thought process so that future engineers aren’t painted into corners.
SSP: After the first settlements are established on Mars, you suggest starting to adapt the Mars environment to Earth-like conditions through “para-terraforming” small parts of the planet such as the Hebes Chasma, a canyon the size of Lake Erie just north of Valles Marineris. This feature has the advantage of being right on the equator and closed at both ends so that kilometer sized arch structures could enclose the valley to warm the local environment with many Eureka settlements below.
Top: Artist concept of kilometer scale arches built above space settlements and enclosing a Martian canyon to provide a para-terraformed environment. Bottom: Magnificent view from below depicting these domes at cloud level on a typical summer day. Credits: Kent Nebergall / Aarya Singh
Planetary protection was mentioned as one of the grand challenges to be overcome. Some space scientists are advocating for robotic missions to answer the question of whether life existed (or still exists) on Mars before humans reach Mars. No such missions are planned prior to Musk’s timeline for putting humans on Mars at the end of this decade. Are you assuming that by the time humans are ready for para-terraforming that the question of life on Mars will be answered?
KN: We would certainly know if active, widespread, indigenous life was an issue by the time of building canyon settlements the size of Lake Erie. Even isolated pockets would leave fossil traces in broader zones.
The bigger question is that of whether or not it is possible to settle Mars if there is a risk of crossing into a local biome accidently. Eureka is built entirely on the surface, so it doesn’t cross the sterilized surface soils if it doesn’t have to. We should be able to mine from Mars with sterile equipment and be able to sterilize further after robotic extraction. We can extract water ice, volcanic rock, and surface dust and build the entire settlement from those basic materials. We can avoid sedimentary materials until we are confident they are not biologically active.
I suspect any life on Mars is from Earth, and brought by meteors. The cross-traffic of meteors throughout the solar system may mean bacterial and possibly slightly more complex life all over the solar system from the late bombardments of Earth. We should consider this no more exotic than breathing in Australia or swimming in the ocean. Microbes adapted for those environments would not be adapted to be pathogenic because why spend billions of generations preparing for a food source that may never arrive? We would have a bigger problem with random toxins that hadn’t leached out or reacted to life billions of years ago than with life itself. I respect the work of those who want sterile capsules of pristine soil captured by the current Mars rover prior to human arrival. That certainly makes sense. I like Carol Stoker’s Icebreaker mission concept. I think NASA and universities would be smart to work with SpaceX on simple rack-mount instrumentation that could be flown to planetary destinations en masse and serviced by Optimus Prime Tesla robots.
“My goal is to build the next generation of the quiet heroes of the dinner table. And certainly a few of those will be leaders too.”
SSP: You’re writing a book about creating an inventor mindset to enable a million “mini-Musks” – people who are not necessarily rich, but who shake up the world in constructive and innovative ways. Tell us more about this philosophy.
KN: The core concept is that if you could get a thousand people to do a hundredth of what Elon has accomplished, it would be a tenfold increase in what we’ve seen in terms of his contribution to technology. That’s not a very big ask individually, even if it’s more garage labs than factories for now. I looked deeply into what Elon Musk does and what other inventors like him have done. I’ve looked at technology revolutions and what key things spark the massive growth waves of innovation. Obviously, there are intersections between the two.
I’m writing a short book this summer to document Elon’s methodologies in an approachable and comprehensive reference. If it attracts enough interest, I can take that core module into different directions. One is digging more into how the mind invents. Another is breaking down how technology revolutions work. A third is all this work on space settlement. I’ve also come up with intellectual property around the root of these concepts that would be valuable software and services. I guess we’ll see what reaction the Elon book gets and see where that goes. It’s a bit heartbreaking to see millions spent on NFTs and other random “stupid money” projects when I’m coming up with concepts for trillion-dollar companies as a hobby.
While we talk a lot about Musk, there are thousands of people who work just behind the spotlight. My father was a production test pilot who put his life on the line to ensure that bombers were flyable for national security, and that the technology that became the commercial jet airliner a decade later would be safe for billions of travelers. He worked with some historic figures of aviation, and his dinner stories were amazing. The Mars Society gave me a way to repeat a little of this history for myself in this dawn of the Mars Age.
Technology revolutions may celebrate a few leaders. But without thousands of talented people several feet behind these inventors, they are little more than curiosities – Di Vinci notebooks or Antikythera mechanisms. My goal is to build the next generation of the quiet heroes of the dinner table. And certainly a few of those will be leaders too. That is my hope. To fill the diaries of pioneers that give permanent cultural bedrock to the accomplishments of people like Elon. Otherwise, even a moon landing is a short story written in water.
Don’t miss Kent’s appearance on The Space Show coming up on Sunday July 10 where you can call in and ask him in person your own questions about these and other visions for space settlement.
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.
Roadmap for research and infrastructure development for growing crops in space for human sustenance and life support, from the ISS to Mars. Credits: Grace L. Douglas, Raymond M. Wheeler and Ralph F. Fritsche
Space settlement advocates know that we will have to take our biosphere with us to space to produce food, provide breathable air and recycle wastes. Completely closing the system, i.e. recycling everything is a huge technological challenge, especially on a small scale like what is planned for settlements in free space or on the surfaces of the Moon or Mars. Fortunately, there are plenty of raw materials in the solar system for in situ resource utilization so we can live off the land, so to speak, until our bioregenerative life support system efficiencies improve.
Early research into crop production in space has been performed on the ISS. But the road ahead for space agriculture in the context of life support systems needs careful planning to pave the way toward biologically self-sustaining space settlements. A team of scientists at NASA is working on a roadmap toward sustainability with a step-by-step approach to bioregenerative life support systems (BLSS) that will provide food and oxygen for astronauts during the space agency’s mission plans in the decades ahead. In a paper in the journal Sustainability they identify the current state of the art, resource limitations and where gaps remain in the technology while drawing parallels between ecosystems in space and on Earth, with benefits for both.
Simulation and modeling of BLSS concepts is important to predict their behavior and help inform actual hardware designs. A team at the University of Arizona performed a study recently analyzing the inputs and outputs of such a system to improve efficiencies and apply it to food production on Earth in areas challenged by resource limitations and food insecurity. Sustainable ecosystems for supporting humans on and off Earth have similar goals: minimizing growing space, water usage, energy needs and waste production while simultaneously maximizing crop yields. The team presented their findings in a paper presented at the 50th International Conference on Environmental Systems held last July. In the study, a model of an ecosystem was created consisting of various combinations of plants, mushrooms, insects, and fish to support a population of 8 people for 183 days with an analysis of total growing area, water requirements, energy consumption and total wastes produced. The study concluded that “In terms of resource consumption, the strategy of growing plants, mushrooms, and insects is the most resource-efficient approach.”
At the same conference, an update was provided on a Scalable, Interactive Model of an Off-World Community (SIMOC). SIMOC was described in a previous post on the Space Analog for the Moon and Mars (SAM) located at Biosphere 2 in Arizona. SIMOC is a platform for education meeting standards for student science curriculum. Pupils or citizen scientists can customize human habitats on Mars by selection of mission duration, crew size, food provisions as well as choosing types of plants, levels of energy production, etc.. Users gain an understanding of the complexity of a BLSS and the tradeoffs between mechanical and biological variables of life support for long duration space missions. There is much to be learned on the limitations and stability of closed biospheres, as discussed last year.
Image of Biosphere 2, a research facility to support the development of computer models that simulate the biological, physical and chemical processes to predict ecosystem stability. Credits: Biosphere 2 / University of Arizona
A BLSS based on plant biology could be augmented with dark ecosystems, the food chain based on bacteria that are chemotrophic, i.e. deriving their energy from chemical reactions rather then photosynthesis, which could significantly reduce the inputs of energy and water.
A concept for a lunar farm called Lunar Agriculture, Farming for the Future was published in 2020 by an international team of 27 students participating in the Southern Hemisphere Space Studies Program at the International Space University.
Layout of a potential subsurface lunar farm. Credits: International Space University and University of South Australia
As a treat to cap off this post, a retired software engineer and farmer named Marshall Martin living in Oklahoma provided his perspective on crops in space on The Space Show recently. A frequent caller to the program, this was his first appearance as a guest where, like the NASA team mentioned earlier, he recommends a phased approach to space farming starting with small orbital facilities, testing inputs and outputs as we go, to ensure the economics pay off at each stage of our migration off Earth. He even envisions chickens and goats as sources of protein and milk, although the weight limitations for inclusion of these animals in space-based ecosystems may not be possible for quite some time. Its unlikely that cows will ever make it to space but cultured meat production is a real possibility for the carnivores among us which is being studied by ESA.
Cattle in the cargo bay of the Firefly-class transport spaceship Serenity. Cows probably won’t make it to space because of weight, volume and resource limitations but cultured meat is a real possibility. Image from the television series Firefly. Credits: Josh Whedon/ Mutant Enemy, Inc. in associations with Twentieth Century Fox Television
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.
Conceptual illustration depicting the deployment sequence of a LEO Moon-Mars dumbbell partial gravity facility serviced by SpaceX’s Starship. Left: Starship payloads being moored by a robot arm. Center: 1.6 m ID inflatable airbeams (yellow) play out from spin access and mate with dumbbell end modules. Rectangular solar arrays deploy by hanging at either end as spin is initiated via thrusters at Mars module. Right: Full deployment with Starship and Dragon docked at spin axis hub. Credits: Joe Carroll via The Space Review
There may be no single human factor more important to understand on the road to long term space settlement than determination of the gravity prescription (GRx) for healthy living in less than Earth normal gravity. What do we mean by the GRx? With over 60 years of human space flight experience we still only have two data points for stays longer than a few days to study the effects of gravity on human physiology: microgravity aboard the ISS and data here on the ground. Based on medical research to date, we know that significant problems arise in human health after months of exposure to microgravity. To name a few, osteoporosis, immune system degradation, diminished muscle mass, vision problems due to changes in interocular pressure and cognitive impairment resulting memory loss and lack concentration. Some of these problems can be mitigated with a few hours of daily exercise. But recovery upon return to normal gravity takes considerable time and we don’t know if some of these problems will become irreversible after longer term stays. We have virtually no data on human health at gravity levels of the Moon and Mars, as shown in this graph by Joe Carrol:
The more important question for permanent space settlements is can humans have babies in lower gravity? If we go by the National Space Societies’ definition, an outpost will never really become a permanent space settlement until it is “biologically self-sustaining”. We evolved over millions of years at the bottom Earth’s gravity well. How will amniotic fluid, changes in cell growth, fetal development and human embryos be affected during gestation under lower gravity conditions on the Moon or Mars? There are already indications that problems will arise during mammalian gestation, at least in microgravity as experienced aboard the ISS.
To answer these questions, Joe Carroll suggests the establishment of a crewed artificial gravity research facility in LEO which he described last month in an article in The Space Review. He proposes a Moon-Mars dumbbell with nodes spinning at different rates to simulate gravity on both the Moon and Mars, which covers most of the planetary bodies in the solar system where settlements would be established if not in free space. The facility could be launched and tended by SpaceX’s Starship once the spacecraft is flight worthy in the next few years in parallel with Elon Musk’s plans to establish an outpost on Mars. Musk may even want to fund this facility to inform his long term plans for communities on Mars. If his goal is for the humanity to become a multiplanetary species, surely will want to know if his settlers can have children.
Carroll’s design connects the Moon and Mars modules with radial structures called “airbeams” which will allow crew to access the variable gravity nodes in a shirtsleeve environment. The inflatable members are composed of polymer fiber fabric which can be easily folded for storage in the Starship payload bay. Crews would be initially launched aboard Dragon until the Starship is human rated.
“Eventually, rotating free-space settlements will get massive enough to use other shapes, but dumbbells plus airbeams seem like the key to useful early ones.”
The paper addresses details on key operating concepts, docking procedures, emergency protocols, and the implications for long term settlement in the solar system.
There may even be a market for orbital tourism to experience lower gravity that could make funding for the facility attractive to space venture capitalists, especially if it is located in an equatorial orbit shielded from ionizing radiation by the Earth’s magnetic fields. As the technology matures, older tourists may even want to retire in orbital communities that offer the advantage of lower gravity as their bodies become frail in their golden years.
Humankind’s expansion out into the solar system depends on where we can survive and thrive in a healthy environment. If ethical clinical studies on lower mammals in a Moon/Mars dumbbell clears the way for a healthy life in lunar gravity then we can expand out to the six largest moons including our own plus Mars. If the data shows we need at least Mars gravity, then the Red Planet or even Mercury could be potential sites for permanent settlement. But if nothing below Earth normal gravity is tolerable, especially for mammalian gestation, it may be necessary to build ever larger rotating O’Neillian free space settlements to expand civilization across the solar system. There are vast resources and virtually unlimited energy if we need to do that. But it will take considerable time and careful planning to establish the vast infrastructure needed to build these settlements. If human physiology is constrained by Earth’s gravity then space settlers will want to know this information soon so that the planning process can be integrated into space development activities about to unfold on the Moon and beyond. If Musk finds out that Mars inhabitants cannot have children and wants to establish permanent communities beyond Earth, would he change course and switch to O’Neillian free space settlements?
“If we do need sustained gravity at levels higher than that of Mars, it seems easier to develop sustainable rotating settlements than to terraform any near-1g planet.”
Listen to Joe Carroll answer my questions about his Moon/Mars dumbbell facility from earlier this month on this archived episode of The Space Show.
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.
