Creating a Space Settlement Cambrian Explosion – Interview with Kent Nebergall

Credits: Kent Nebergall

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.

Highlights from the International Space Development Conference

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.

NewSpace features the dawn of the age of space resources

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.

Self-replicating “living” machines for lunar settlement

Conceptual illustration of a self-replicating machine. Source: Wikipedia

In a 2020 paper in the journal Biomimetics, Alex Ellery who heads the Space Exploration Engineering Group in the Department of Mechanical & Aerospace Engineering at Carleton University, Ottawa, lays out a case for engineering mechanical systems that emulate biological life in the same vain as a Von Neumann universal constructor. This concept, conceived by the Hungarian-American mathematician John von Neumann in 1940s prior to the invention of the computer, is a machine that can make copies of itself given a set of instructions, sufficient materials and a source of energy.

Ellery begins by examining theories on the origin of life on Earth to distill down the essence of how inanimate material was transformed into living systems. He then goes on to define the basic characteristics of how organisms use energy to process materials to evolve and reproduce. Applying these principles to mechanical systems he envisions bioinspired machines be used to propagate self-replicating factories on the Moon in a lunar industrial ecology. Materials mined in situ by robots would be processed using solar energy via automated additive manufacturing processes analogous to living organisms reproducing to expand the facility.

“Adopting the notion of a biological ecosystem, we can envisage a modest self-sustained metabolism.”

In an examination of what life is, Ellery makes the analogy between ribosomes, the basic macromolecular machine that performs protein synthesis in living cells, and a 3D printer called the Replicating Rapid Prototyper (or RepRap), a key element of his research. Through additive manufacturing this device can print some of its own plastic components.

RepRap 3D printer comprising a Cartesian robot with extruder head (Figure 2 in the paper) capable of printing copies of some of its own plastic components.. Credits: Alex Ellery

Eventually, Ellery’s goal is for the device to be able to fabricate most of its own parts including the metal components. However, a fully autonomous self-replicating machine will required considerable advancements in artificial intelligence and automation. Initially, prefabricated complex components such as electronic circuitry, actuators, and sensors may be supplied independently as “vitamins” from Earth and assembled automatically during fabrication to enable automatic manufacture of the robots. Ellery introduces his team and describes his research at Carlton University in this short video.

Self-replicating factories designed for the production of space settlement infrastructure have been covered previously by SSP. Hybrid approaches that include humans in the loop to guide the process may be a near term solution until AI and robotic technologies become fully autonomous.

Some have postulated that if Von Neumann probes have been used by alien civilizations to colonize the galaxy there may be ways to detect them.

Crops in space: providing sustenance and life support for settlers

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

Across the Pond, our European friends at LIQUIFER Systems Group are working on greenhouses for the Moon and Mars derived from the EDEN ISS simulation facility in Antarctica.

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

Finally, for those thinking long term of eventual settlement of the galaxy, there are even some people modeling life support systems for interstellar arks.

Image of the interior of a worldship habitat for interstellar travel. Credits: Michel Lamontagne / Principium, Issue 32, February 2021

Charon: a reusable single-stage to orbit shuttle for Mars

Conceptual illustration depicting the Charon single-stage to Mars orbit mission architecture. Credits: Jérémie Gaffarel et al.* – image from Graphical Abstract with addition of text.

In the next few decades a settlement on Mars will be established, either by Elon Musk or other spacefaring entities (or both). To enable an economically viable supply chain to support a prosperous colony on Mars, an affordable and sustainable transportation system will be needed. Musk is designing Starship for what he originally called an interplanetary transportation system. But his design is just the first step and is expected to evolve over time. As originally conceived Starship may not make long term economic sense for launch from Earth, travel across interplanetary space, landing on Mars, lift off again and finally, return and safe landing on Earth. Even though the Starship User Guide says the the vehicle is designed to carry more than 100 tons to Mars, the enormous amount of cargo and crew required to be transported to support a prospering and sustainable Martian colony if done only with repeated Starship launches directly from Earth will likely be too expensive.

A better approach might be to limit Starship to an in-space transportation system which cycles back and forth between Earth and Mars orbits without a (Mars) landing capability. Not knowing how Starship may evolve, this could be a starting point. Eventually, a more efficient interplanetary transportation system may be an Aldrin cycler. Either scenario would require a shuttle at Mars for delivery of payloads from low orbit to the surface and back to space again. A team* at Delft University of Technology, The Netherlands has come up with a design for a reusable singe-stage to orbit vehicle they call Charon that would reliably address this final leg of the Mars supply chain. They described the mission architecture in an article in the journal Aerospace last year.

The team identified 80 key design requirements for Charon, but three stood out as the most important. At the top of the list was the capability of transporting 6 people and 1200 kg of cargo to and from low Mars orbit. Next, any consumables needed for the vehicle would have the capability of being produced in situ on Mars. Finally, because of the human rating, the reliability of the system would have to be high – with loss of crew less than 0.5% or 1 out of 270, which is equivalent to SpaceX’s Crew Dragon.

With safety being a high priority an abort subsystem is included to address each anticipated flight phase and the associated abort modes. The SpaceX Starship design does not have an abort system, so the authors believe that Charon would be safer for launch from Mars given the high flight rate anticipated to and from Mars low orbit. They suggest that Starship be limited to launch from Earth and interplanetary transportation to Mars orbit.

Cutaway illustration of the layout of the Charon vehicle adapted from Figure 5 in article. Credits: Jérémie Gaffarel et al.*

Cutaway view of the capsule adapted from Figure 4 in article. Credits: Jérémie Gaffarel et al.*

Significant infrastructure will be needed on Mars to support operations, especially in situ resource utilization for production of methane and oxygen for Charon’s propulsion system. This pushes out the timeline for implementation a few decades (to at least 2050) when a Mars base is expected to be well established with appropriate power sources and equipment to handle mining, propellant manufacturing, maintenance, communications and other needed facilities.

Upon a thorough analysis of Charon’s detailed design, reliability and budgets the team concluded that “The program for its development and deployment is technologically and financially feasible.”

* Gaffarel, Jérémie, Afrasiab Kadhum, Mohammad Fazaeli, Dimitrios Apostolidis, Menno Berger, Lukas Ciunaitis, Wieger Helsdingen, Lasse Landergren, Mateusz Lentner, Jonathan Neeser, Luca Trotta, and Marc Naeije. 2021. “From the Martian Surface to Its Low Orbit in a Reusable Single-Stage Vehicle—Charon” Aerospace 8, no. 6: 153. https://doi.org/10.3390/aerospace8060153

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

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

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

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

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

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

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

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

Update on the Photonic Laser Thruster and the interplanetary Photonic Railway

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Leveraging Starship for lunar habitats

Conceptual overview of the lunar Rosas Base derived from a SpaceX Starship tipped on its side and covered with regolith. Credits: International Space University, Space Studies Program 2021 Team*. The name of the base is in memory of Oscar Federico Rosas Castillo

SSP has examined some of the implications of SpaceX’s Starship achieving orbit, such as an imminent tipping point in U.S. human spaceflight and launch policy. We’ve also discussed how if its successful, Starship will bring about a paradigm shift in the settlement of Mars and how the spacecraft could be used to determine the gravity prescription.

During Elon Musk’s recent Starship update from Boco Chica, Texas he said that he was “highly confident” that Starship would reach orbit this year. He also predicted that the cost of placing 150 tons in LEO could eventually come down to as low as $10 million per launch, and that “…there are a lot of additional customers that will want to use Starship. I don’t want to steel their thunder. They’re going to want to make their own announcements. This will get a lot of use, a lot of attention….”

“Once we make this work, its an utterly profound breakthrough in access to orbit….the use cases will be hard to imagine.” – Elon Musk

One such potential use case was worked out in detail by a team* of students last year during the International Space University’s (ISU) Space Studies Program 2021 held in Strasbourg, France. Called Solutions for Construction of a Lunar Base, the project used the version of Starship currently under development by SpaceX for the Human Landing System component of NASA’s Artemis Program as the basis for a habitat on the Moon. The concept was also described in a paper at the 72nd International Astronautical Congress in Dubai last October. The mission of the project was:

“To develop a roadmap for the construction of a sustainable, habitable, and permanent lunar base. This will address regulatory and policy frameworks, confront technological and anthropological challenges and empower scientific and commercial lunar activities for the common interest of all humankind.”

The team did an impressive job working out solutions to some of the most challenging issues facing humans living in the harsh lunar environment like radiation, micrometeorites, and hazardous lunar dust. They also dealt with human factors, physiological and medical problems anticipated under these conditions. Finally, the legal aspects as well as a rigorous financial analysis was conducted to support a business plan for the base in the context of a sustainable cislunar economy. The report is lengthy and challenging to summarize but here are some of the highlights.

A decommissioned Starship forms the primary core component of the outpost having its fuel tanks converted to living space of considerable volume. This has precedent in the U.S. space program when NASA modified an S-IVB stage of a Saturn V to create Skylab. The team envisions extensive use of a MOdular RObotic Construction Autonomous System (MOROCAS) outfitted with specific tools to perform a variety of activities autonomously which would reduce the need for extravehicular activities (EVA) thereby minimizing risks to crew. The MOROCAS would be utilized to tip the Starship on its side, pile regolith over the station for radiation protection and a range of other useful functions.

Medical emergencies were considered for accidents anticipated for construction activities in the high risk lunar environment. The types of injuries that could be expected were assessed to inform plans for needed medical equipment and facilities for diagnosis and treatment.

As discussed by SSP in a previous post, hazards from lunar regolith must be mitigated in for any activities on the moon. The solutions proposed included limiting dust inhalation through monitoring and smart scheduling EVAs, the use of dust management systems utilizing electrostatic removal mechanisms and intelligent design of equipment. In addition, landing sites and travel routes would be prepared either through sintering of regolith or compaction to prevent damage to structures by rocket plumes.

Funding of the Rosas Base was envisioned to be implemented via a public/private partnership administered by an international authority called the Rosas Lunar Authority (RLA). The RLA management would be structured as an efficient interface between participating governments while being capable of responding to policy and legal challenges. It would rely on public financing initially but eventually shift to private financing supplemented by rental of the base to stakeholders and interested parties.

Finally the team examined the value proposition driving establishment of the base. Sociocultural benefits, scientific advancements and technology transfer would be the primary driving factors. Initial market opportunities would be targeted at the scientific community in the form of data and lunar samples. Follow-on commercial activities that would attract investors could include launch services to orbit, cislunar spacecraft services, propellent markets in lunar orbit and LEO, communications networks in cislunar space and commercial activities on the surface such as supplies of transportation and mining equipment, habitats, and ISRU facilities.

The surface of the Moon provides exciting opportunities for scientific experimentation, medical research, and commerce in the cislunar economy about to unfold in the next decade. The unique capabilities of Starship and the solutions proposed in this report support a sustainable business model for a permanent outpost like the Rosa Base on the Moon.

Conceptual illustration of an emerging cisluar economy. Credits: International Space University, Space Studies Program 2021 Team*

An executive summary of the project is also available.

__________

* ISU Space Studies Program 2021 participants:

Dark ecosystems for food production in space

Artist concept of industrial hubs of circular food production including vertical farming, bioreactors, greenhouses, water treatment and energy production. The same technology has duel use and could be leveraged for life support systems in space settlements. Credits: Mark Goerner / Orbital Farm

Typical plans for space settlements include greenhouses for growing plants as a source of food as well as a key component of ecological closed life support systems to help produce air and recycle water. There are efforts to make these space farms as compact and efficient as possible utilizing hydroponics and LED lighting. But the energy, volume, water and labor requirements can still be a challenge. A new approach is described in a paper in New Space by Michael Nord and Scot Bryson that is based on Earth’s dark ecosystem, the food chain based on bacteria that are chemotrophic, i.e. deriving their energy from chemical reactions rather then photosynthesis. An example of these type of organisms are bacteria that live near volcanic sulfur vents at the bottom of the ocean. They synthesize organic molecules from hydrogen sulfide, carbon dioxide and oxygen which in turn nourish giant tube worms.

Giant tube worms nourished by organic molecules synthesized by chemotrophic bacteria near deep undersea sulfur vents. Credits: Biology Dictionary

“Earth’s dark ecosystem affords us an elegant solution.”

This is not new technology. Fermentation is an example of this biological process which humans have been using for thousands of years in the production of food and drink. NASA explored this option in the 1960s in their plans for sources of food to sustain astronauts on long duration space flights. Synthetization of “single-celled proteins” showed promise for astronaut sustenance but NASA’s priorities shifted after Apollo putting less emphasis on manned spaceflight leading to funding cuts, which put these efforts on hold.

Fast forward to today, there are many companies focusing on using dark ecology as an alternative source of protein both for an ever increasing human population and for animal agriculture. The single-celled proteins are produced by fermentation in bioreactors to produce products mainly used in animal feed but at least one firm, Quorn, is focused on human consumption.

Mycoprotein for human consumption produced by fermentation of the fungus Fusarium venenatum. Credits: Quorn

Others in both government and industry are transitioning Earth’s agricultural approach to a circular economy for food, where food waste is designed out, food by-products are re-used at their highest value, and food production regenerates rather than degrades natural systems. Innovations by companies involved in this type of farming here on Earth have direct applications in bioregenerative life support systems in space. Orbital Farm, who’s CEO Scot Bryson coauthored the paper, is one such company exploring commercialization opportunities in this field.

The authors performed an analysis of energy inputs and material flows for conventional photosynthetic food production when compared to a dark ecosystem and found that the latter is 100 times more efficient in water and energy use, and 1000 times better in terms of volume. But that is not all. There is an added benefit in that “…the very same organisms can be engineered to make pharmaceuticals, plastics, and a variety of other useful complex organic compounds.”

The advantages for space settlement are clear. Although photosynthetic plant growth will play a role in life support systems including the added benefit to humans of the aesthetic value of living among plants, dark ecology can augment food from photosynthetic plants with efficient and sustainable protein production.

“…for bulk production of calories, chemotrophic organisms have enormous efficiencies over production with staple crops, which will be nearly impossible to ignore for mission designers.”