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The impact of the Gravity Prescription on the future of space settlement

Artist rendering of a family living in a rotating free-space settlement based on the Kalpana Two design, with a length of 110m and diameter of 125m. Credits: Bryan Versteeg / Spacehabs.com

This post summarizes my upcoming talk for the Living in Space Track at ISDC 2024 taking place in Los Angeles May 23 – 26. The presentation is a distillation of several posts on the Gravity Prescription about which I’ve written over the years.

Lets start with a couple of basic definitions. First, what exactly is a space settlement? The National Space Society defined the term with much detail in an explainer by Dale L. Skran back in 2019. I’ve extracted this excerpt with bolded emphasis added:

Space Settlement is defined as: ​

​“… 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 …”

​The point here is that people will want to have children wherever their families put down roots in space communities. Yes, a “settlement” could be permanent and perhaps inhabited by adults that live out the rest of there lives there, such as in a retirement community. But these are not biologically self-sustaining in the sense that settlers have offspring that are conceived, born and raised there living out healthy lives over multiple generations.

Next we should explain what is meant by the Gravity Prescription (GRx). First coined by Dr. Jim Logan, the term refers to the minimum “dosing” of gravity (level and duration of exposure) to enable healthy conception, gestation, birth and normal, viable development to adulthood as a human being…over multiple generations. It should be noted that the GRx can be broken down into at least three components: the levels needed for pregnancy (conception through birth), early child development, and adulthood. The focus of this discussion is primarily on the GRx for reproduction.

We should also posit some basic assumptions. First, with the exception of the GRx, all challenges expected for establishment of deep space settlements can be solved with engineering solutions (e.g. radiation protection, life support, power generation, etc…)​. The one factor that cannot be easily changed impacting human physiology after millions of year of evolution on Earth is gravity. We may find it difficult or even impossible to stay “healthy enough” under hypogravity conditions on the Moon or Mars, assuming all other human factors are dealt with in habitat design.

Lets dive into what we know and don’t know about the GRx. Several decades of human spaceflight have produced an abundance of data on the deleterious effects of microgravity on human physiology, not the least of which are serious reduction in bone and muscle mass, ocular changes, and weakening of the immune system – there are many more. So we know microgravity is not good for human health after long stays. Clearly, having babies under these conditions would not be ethical or conducive for long term settlement.

The first studies carried out on mammalian reproduction in microgravity took place in the early 1990s aboard the Space Shuttle in a couple of experiments on STS-66 and STS-70. 10 pregnant rats were launched at midpregnancy (9 days and 11 days, respectively) on each flight and landed close to the (22 day) term. The rat pups were born 2 days after landing and histology of their brain tissue found spaceflight induced abnormalities in brain development in 70% of the offspring.

It was not until 2017 that the first mammalian study of rodents with artificial gravity was performed on the ISS. Although not focused on reproduction, the Japan Aerospace Exploration Agency (JAXA) performed a mouse experiment in their Multiple Artificial-gravity Research System (MARS) centrifuge comparing the impact of microgravity to 1g of spin gravity. ​The results provided the first experimental evidence that mice exposed to 1g of artificial gravity maintained the same bone density and muscle weight as mice in a ground control group while those in microgravity had significant reductions.

Diagram depicting an overview of the first JAXA Mouse Project in the MARS centrifuge with photos of the experiment on the ISS. Credits: Dai Shiba et al. / Nature. http://creativecommons.org/licenses/by/4.0/

In 2019 JAXA carried out a similar study in the MARS centrifuge adding lunar gravity levels to the mix. This study found that there were some benefits to the mice exposed to 1/6g in that Moon gravity helped mitigate muscle atrophy, but it did not prevent changes in muscle fiber or gene expression​.

Just last year, a team led by Dr. Mary Bouxsein at Harvard Medical School conducted another adult mouse study on the MARS centrifuge comparing microgravity, .33g, .67g and 1g. They found that hind quarter muscle strength increased commensurate with the level artificial gravity concluding, not surprisingly, that spaceflight induced atrophy can be mitigated with centrifucation. The results were reported at the American Society for Gravitational and Space Research last November.​

Returning to mammalian reproduction in space, an interesting result was reported last year in the journal Cell from an experiment by Japanese scientists at the University of Yamanashi carried out on the ISS in 2019. The team, headed up by Teruhiko Wakayama, devised a way to freeze mouse embryos post conception and launch them into space where they were thawed by astronauts and allowed to develop in microgravity. Control samples were cultured in 1g artificial gravity on the ISS and Earth normal gravity on the ground. The mouse embryos developed into blastocysts and showed evidence of cell differentiation/gene expression in microgravity after 4 days​. The researchers claimed that the results indicated that “Mammals can thrive in space”. This conclusion really can’t be substantiated without further research.

Which brings us to several unknowns about reproduction in space. SSP has explored this topic in depth through an interview with Alex Layendecker, Director of the Astrosexological Research Institute. Yet to be studied in depth is (a) conception, including proper transport of a zygote through the fallopian tube to implantation in the uterus. Less gravity may increase the likelihood of ectopic pregnancy which is fatal for the fetus and could endanger the life of the mother; (b) full gestation through all stages of embryo development to birth​; and (c) early child development and maturation to adulthood in hypogravity​. All these stages of mammalian reproduction need to be validated through ethical clinical studies on rodents progressing to higher primate animal models before humans can know if having children in lower gravity conditions on the Moon or Mars will be healthy and sustainable over multiple generations.

AI generated image of an expectant mother with her developing fetus in Earth orbit after mammalian reproduction has been validated via higher animal models through all stages of pregnancy for a safe level of gravity. An appropriate level of radiation shielding would also be required and is not shown in this illustration. Credit: DALL-E-3

Some space advocates for communities on the Moon or Mars have downplayed the importance of determining the GRx for reproduction with the logic that a fetus in a woman’s uterus on Earth is in neutral buoyancy and thus is essentially weightless. Therefore, why does gravity matter? ​ I discussed this question with Dr. Layendecker and he had the following observations paraphrased here: True, gravity may have less of an impact in the first trimester. But on the cellular level, cytoskeletal development and proper formation/organization of cells may be impacted from conception to birth​. Gravity helps orient the baby for delivery in the last trimester​ and keeps the mother’s uterine muscles strong for contractions/movement of the baby through the birth canal​. There are many unknowns on what level of gravity is sufficient for normal development from conception to adulthood.

Why does all this matter? Ethically determining the right level of gravity for healthy reproduction and child development will inform where families can safely settle space​. The available surface gravities of bodies where we can establish communities in space cluster near Earth, Mars and Moon levels​. These are our only GRx options ​on solar system bodies.

Gravity level clustering of solar system bodies available for space settlement. Credit: Joe Carroll

The problem is that we don’t yet know whether we can remain healthy enough on bodies with gravity equivalent to that on the Moon or Mars, so we can’t select realistic human destinations or formulate detailed plans until we acquire this knowledge​. Of course we can always build rotating settlements in free space with artificial gravity equivalent to that on Earth. Understanding the importance of the GRx and determining its value could change the strategy of space development in terms of both engineering and policy decisions. The longer we delay, the higher the opportunity costs in terms of lost time from failure to act​.

What are these opportunity cost lost opportunities​? Clearly, at the top of Elon Musk’s list is “Plan B” for humanity, i.e. a second home in case of cataclysmic disaster such as climate change, nuclear war, etc. This drives his sense of urgency. From Gerard K. O’Neill’s vision in The High Frontier, virtually unlimited resources in space could end hunger and poverty, provide high quality living space for rapidly growing populations​, achieve population control without war, famine, or dictatorships​. And finally, increase freedom and the range of options for all people​.

If humans can’t have babies in less than Earth’s gravity then the Moon and Mars may be a bust for long term (biologically sustainable) space settlement.​ There will be no biologically sustainable cities with millions of people on other worlds unless they can raise families there​.

Spin gravity rotating space settlements providing 1g artificial gravity may be the only alternative​. If Elon Musk knew that the people he wants to send to Mars can’t have children there, would he change his plans for a self-sustaining colony on that planet?​ Having and raising children is obviously important to him. As Walter Isaacson wrote in his recent biography of Musk, “He feared that declining birthrates were a threat to the long-term survival of human consciousness.”

So how could he determine the GRx quickly? One solution would be to fund a partial gravity facility in low Earth orbit to run ethical experiments on mammalian reproduction in hypogravity. Joe Carroll has been refining a proposal for such a facility, a dual dumbbell Moon/Mars low gravity laboratory which SSP has covered, that could also be marketed as a tourist destination. Spinning at 1.5 rpm, the station would be constructed from a combination of Starship payload-sized habitats tethered by airbeams allowing shirt sleeve access to different gravity levels​. Visitors would be ferried to the facility in Dragon capsules and could experience 3 gravity levels with various tourist attractions​. The concept would be faster, cheaper, safer and better than establishing equivalent bases on the Moon or Mars to quickly learn about the GRx​. The facility would be tended by crews at both ends that live & collect health data for up to a year or more​. And of course, ethical experiments on the GRx for mammalian reproduction would be carried out, first on rodents and then progressing to higher primates if successful.

Left: Conceptual illustration depicting a LEO Moon-Mars dumbbell partial gravity facility constructed from Starship payload-sized habitats tethered by airbeams and serviced by Dragon capsules. Rectangular solar arrays deploy by hanging at either end as spin is initiated via thrusters at Mars module. Center: Image of an inflated airbeam demonstration. Right: diagram of an airbeam stowed for transport and after deployment. Credit: Joe Carroll

What if these experiments determine that having children in lower gravity is not possible and our only path forward are free-space rotating settlements? Physics and human physiology require that they be large enough for settlers to tolerate a 1g spin rate to prevent disorientation. As originally envisioned by O’Neill, the diameter of his Island One space settlement would be about 500 meters.

Conceptual illustration of an Island One space settlement. The living space sphere is sized at about 500m in diameter. Credits: Rick Guidice / NASA

As originally proposed, these settlements would be located outside the Earth’s magnetic field at the L5 Earth-Moon Lagrange Point necessitating that they be shielded with enormous amounts of lunar regolith to protect occupants from radiation. Their construction requires significant technology development and infrastructure (e.g. mass drivers on the Moon, automated assembly in space, advances in robotics, power sources, etc…)​. Much of this will eventually be done anyway as space development progresses…however, knowing the GRx (if it is equal to 1g) may foster a sense of urgency​.

Some may take the alternative viewpoint that if we know that Earth’s gravity works just fine we could proceed directly to free-space settlements if we could overcome the mass problem. This is the approach Al Globus and Tom Marotta took in their book The High Frontier: An Easier Way with Kalpana One​, a 450m diameter cylindrical rotating free-space settlement located in equatorial low Earth orbit (ELEO) protected by our planet’s magnetic field, thereby reducing the mass significantly because there would be far less need for heavy radiation shielding.

Artist impression of Kalpana One rotating free-space settlement located in equatorial low Earth orbit. Credits: Bryan Versteeg / Spacehabs.com

But there may be an even easier way. Kasper Kubica has proposed a 10 year roadmap to the $10M condo in ELEO based on Kalpana Two, a scaled down version of the orbital settlement described by Al Globus in a 2017 Space Review article.

Artist rendering of the inside of a rotating free-space settlement based on the Kalpana Two design, with a length of 110m and diameter of 125m. Credits: Bryan Versteeg / Spacehabs.com

Even though these communities would be lower mass, they will still require significant increases in launch rates to place the needed materials in LEO, especially near the equator​. Offshore spaceports, like those under development by The Spaceport Company, could play a significant role​ in this infrastructure. Legislation providing financial incentives to municipalities to build spaceports would be helpful, such as The Secure U.S. Leadership in Space Act of 2024 introduced in Congress last month. The new law (not yet taken up in the Senate) would amend the IRS Code to allow spaceports to issue tax-exempt Muni bonds for infrastructure improvements.

Wouldn’t orbital debris present a hazard for settlements in ELEO?​ Definitely yes, and the National Space Society is shaping policy in this area. The best approach is to emphasize “light touch” regulatory reform on salvage rights, with protection and indemnity of the space industry to encourage recycling and debris removal.​ Joe Carroll has suggested a market-based approach that would impose parking fees for high value orbits, which would fund a bounty system for debris removal. This system would incentivize companies like CisLunar Industries, Neumann Space and Benchmark Space Systems, firms that are developing space-based processes to recycle orbital debris into useful commodities such as fuel and structural components.

Further down the road in technology development and deeper into space, advances in artificial intelligence and robotics will enable autonomous conversion of asteroids into rotating space settlements, as described by David Jensen in a paper uploaded to arXiv last year.​ This approach significantly reduces launch costs by leveraging in situ resource utilization. Initially, small numbers of “seed” tool maker robots are launched to a target asteroid​ along with supplemental “vitamins” of components like microprocessors that cannot be easily fabricated until technology progresses, to complete the machines. These robotic replicators use asteroid materials to make copies of themselves and other structural materials eventually building out a rotating space settlement. As the technology improves, the machines eventually become fully self-replicating, no longer requiring supplemental shipments from Earth.

Artist impression of a rotating space settlement constructed from asteroid materials. Credits: Bryan Versteeg, spacehabs.com

Leveraging AI to enable robots to build space settlements removes humans from the loop initially, eliminating risk to their health from exposure to radiation and microgravity​. Send it the robot home builders – families then safely move in later. There are virtually unlimited supplies in the asteroid belt to provide feedstock to construct thousands of such communities.

Artist impression of the interior of Stanford Torus free-space settlement. Advances in artificial intelligence and robotics will enable autonomous self replicating machines that could build thousands of such communities from asteroid material. Credits: Don Davis / NASA

If rotating space settlements with Earth-normal gravity become the preferred choice for off-Earth communities, where would be the best location, the prime real estate of the solar system? Jim Logan has identified the perfect place with his Essential Seven Settlement Criteria.

  • Low Delta-V​ – enabling easy access with a minimum of energy
  • Lots of RESOURCES​ … obviously!
  • Little or No GRAVITY WELL​ – half way to anywhere in the solar system
  • At or Near Earth Normal GRAVITY for​
    People, Plants and Animals ​- like what evolved on Earth
  • Natural Passive 24/7 RADIATION Protection​ – for healthy living
  • Permit Large Redundant Ecosystem(s)​ – for sustenance and life support
  • Staging Area for Exploration and Expansion​
    (including frequent, recurrent launch windows)​

Using this criteria, Logan identified Deimos, the outermost moon of Mars, as the ideal location. As discussed above, AI and robotic mining technology improvements will enable autonomous boring machines to drill a 15km long core through this body with a diameter around 500 meters – sized for an Island One space settlement to fit perfectly.

Conceptual illustration of a 500 meter wide by 15km long core bored through Deimos. Credit: Jim Logan

In fact, 11 Island One space colonies (minus the mirrors) strung end to end through this tunnel would provide sea level radiation protection and Earth normal artificial gravity for thousands of healthy settlers.

Left: Artist impression of an Island One space settlement. Credits: Rick Guidice / NASA. Right: To scale depiction of 11 Island One space settlements strung end-to-end in a cored out tunnel through Deimos providing sea level radiation protection and Earth normal artificial gravity. Credit: Jim Logan

In conclusion, the GRx for reproduction will inform where biologically self-sustaining healthy communities can be established in space. If we find that the GRx is equal to Earth’s normal level, free-space settlements with artificial gravity will be the safest and healthiness solution for humans to live and thrive throughout the solar system. The sooner we determined the GRx the better, for current plans for settling the Moon or Mars may need to be altered to consider rotating space colonies, which will require significant infrastructure development and regulatory reform​. Alternatively, since we know Earth’s gravity works just fine, we may choose to skip determination of the GRx and start small with Kalpana in low Earth orbit. Eventually, artificial intelligence will enable safe, autonomous self-assembly of space settlements from asteroids. The interior of Deimos would be the perfect place to build safe, healthy and biologically self-sustaining space settlements.

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Mars as breadbasket for the outer solar system

Artist’s rendering of a farming settlement on Mars. Credits: HP Mars Home Planet Rendering Challenge via International Business Times.

Space settlement will eventually require space farming to feed colonists and to provide life support. It’s clear that we will replicate our biosphere wherever we go. In that spirit, Bryce L. Meyer envisions Mars as the breadbasket of the outer solar system. In a presentation at Archon 45, a science fiction and fantasy convention held annually by St. Louis area fans, he makes the case for why the fourth planet would be the ideal spot to grow crops and feed an expanding population as part of the roadmap to agriculture in space.

Carbon dioxide and subsurface water ice are plentiful on Mars, critical inputs for crop photosynthesis. There is also evidence of lava tubes there which could provide an ideal growing environment protected from radiation, micrometeorite bombardment and temperature extremes. The regolith should provide good nutrients and there is already research on methods to filter out perchlorates, a toxic chemical compound in the Martian soil.

Image of Lava tubes on the surface of Mars as photographed by ESA’s Mars Express spacecraft. Credits: ESA/DLR/FU Berlin/G Neukum / NewScientist

Another advantage that Mars holds as a food production hub for the asteroids and beyond is its placement further out in the solar system. Since it is higher up in the sun’s gravity well, Meyer calculates that it would take less than 43% of the fuel needed to transport goods from Mars outward than from Earth. He even suggests that with its lower gravity and recent advancements in materials research, a space elevator at Mars could be economically feasible to cheaply and reliably transport foodstuff off the planet.

Meyer keeps a webpage featuring space agriculture, terraforming, and closed cycle microgravity farming where he poses the question “Why settle space?” I like his answer: “Trillions of Happy Smiling Babies!!!”

Basic input/output diagram of an environmental control and life support system like what would be expected in a space farm. Credits: Bryce L. Meyer

Meyer is the founder and CEO of Cyan React, LLC, a startup that designs compact photobioreactors and provides expertise in closed-cycle farming and life support especially for space settlement and space habitats. He is also a National Space Society Space Ambassador doing his part to educate the public about the potential benefits to humanity through the use of the bountiful resources in space. In a presentation at this year’s International Space Development Conference, he describes his research on bioreactors explaining how settlers will grow food and recycle waste sustainably on the high frontier.

Diagram depicting the flow of materials in a closed space farm habitat utilizing bioreactors. Credits: Bryce L. Meyer

Complete closure and stability of an environmental control and life support system (ECLSS) is challenging and not without limitations. As launch and space transportation costs come down in the near future and off-Earth supply chains become more reliable, complete closure will not be required at least initially. In situ resource utilization will provide replacement of some ECLSS consumables where available for colonists to live off the land. As missions go deeper into space reaching the limits of supply chain infrastructure and even out to the stars, closure of habitat ECLSS and resource planning will become more important. Meyer has done the math for farms in space to provide food and air for trillions of smiling babies…and their families as they move out into the solar system.

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Starship changes the space settlement paradigm

Artist rendering of an earlier version of Starship (formerly BFR, Interplanetary Transport System) approaching Mars. Credits: SpaceX

A mission architecture for Starship is described in a preprint open access article published online December 2 to be released in the next issue of the New Space Journal. The paper lays out a proposed strategy for using the yet to be validated SpaceX reusable spacecraft to establish a self sustaining colony on Mars. The authors* are a mix of space practitioners from NASA, the space industry and academia. No doubt Elon Musk may be thinking along these lines as he lays his company’s plans to assist the human race in becoming a multi-planet species.

Starship is a game changer. It is being designed from the start to deposit massive payloads on The Red Planet. It will be capable of delivering 100 metric tons of equipment and/or crew to the Martian surface, and after refueling from locally sourced resources, returning to Earth. This capability will not only enable extensive operations on Mars, it will open up the inner solar system to affordable and sustainable colonization.

Some of the assumptions posited for the mission architecture are based on Musk’s own vision for his company’s flagship space vehicle as articulated in the New Space Journal back in 2017, namely that two uncrewed Starships would initially be sent to the surface of Mars with equipment to prepare for a sustainable human presence.

“These first uncrewed Starships should remain on the surface of Mars indefinitely and serve as infrastructure for building up the human base.”

The initial landing sites will be selected based on where the water is. The priority will be finding and characterizing ice deposits so that humans will eventually be able to locally source water for life support and to produce fuel for the trip home. The automated payloads of these initial missions will be mobile platforms similar in design to equipment planned for upcoming robotic missions to the Moon in the next couple of years. One such spacecraft, the Volatiles Investigating Polar Exploration Rover (VIPER) is discussed with its suite of instruments that will be used to assess the composition, distribution, and depth of subsurface ice to inform follow-on ISRU operations.

“The use of water ice for ISRU has been determined as a critical feature of sustainability for a long-term human presence on Mars.”

VIPER Searches for Water Ice on the Moon
Conceptual depiction of the NASA VIPER rover planned for delivery to the Moon’s south pole in late 2023. A mobile platform with a similar suite of instruments based on this design could be launched to Mars aboard Starship. Credits: NASA

To harvest water from subsurface ice the authors suggest using proven technology such as a Rodriguez Well (Rodwell). In use since 1995, a Rodwell has been providing drinking water for the U.S. research station in Antarctica. The U.S. Army Engineer Research and Development Center’s (ERDC) Cold Region Research and Engineering Laboratory (CRREL)  has been working with NASA to prove the technology for use in space in advance of a human outpost on Mars.

Diagram depicting how a Rodriquez Well works. Credits: U.S. Army Engineer Research and Development Center

“Rodwell systems are robust and still in routine use in polar regions on Earth.”

The next order of business is power generation. The authors suggest using solar power as a first choice because the technology readiness level is the most mature at this time. Autonomous deployment of a photovoltaic solar array would be carried out on the initial uncrewed missions. But due to frequent dust storms that could diminish the array reliability, nuclear power may be a more appropriate long term solution once space based nuclear power is proven. NASA’s Glenn Research center is working on Fission Surface Power with plans for a lunar Technology Demonstration Mission in the near future. A solid core nuclear reactor is also an option as the technology is well understood.

These initial missions will robotically assess the Martian environment at the landing sites to inform designs of subsequent equipment to be delivered by crewed Starship missions in future launch windows occurring every 26 months. Weather monitoring will be performed as well as measurements of radiation levels and geomorphology to inform designs of habitats and trafficability. Remotely controlled experiments on hydroponics will also be performed to understand how to produce food. Testing will be needed on excavation, drilling, and construction methods to provide data on how infrastructure for a permanent colony will be robustly designed.

Starship’s ample payload capacity will allow prepositioning of supplies of food and water to support human missions before self sustaining ISRU and agriculture can be established. Communication equipment will be deployed and landing sites prepared for the arrival of people. Much of these activities will be tested on the Moon ahead of a Mars mission.

Production of methane and oxygen in situ on Mars will enable refueling of Starship for the trip home, as envisioned in 1990 by Robert Zubrin and David Baker with their Mars Direct mission architecture. Zubrin’s Pioneer Astronautics may even play a role through provision of equipment for ISRU as they are already working on hardware that could be tested on the Moon soon. One could envision a partnership between Zubrin and Musk as their organizations have common visions, and Zubrin has written about the transformative potential of Starship. When people arrive on Starship during a subsequent launch window after the placement of uncrewed vehicles, further testing of ISRU and life support equipment will be performed with humans in the loop to validate these technologies that will enable Mars settlements to sustain themselves.

If Musk is successful in establishing a permanent self-sustaining colony on Mars will it be a true settlement? The National Space Society in their definition says that a space settlement “..includes where families live on a permanent basis, and…with the goal of becoming…biologically self-sustaining…”, i.e. capable of human reproduction. The definition is agnostic as to if the settlement is in space or on a planetary surface. Musk wants to established cities on the planet housing millions of people by mid century. But does this make sense if settlers can’t have healthy children in the lower gravity of Mars? SSP explored this question in a recent post. Hopefully, once Starship becomes operational, an artificial gravity research facility in LEO will be high on Musk’s priority list to answer this question before he gets too far down the Martian urban planning roadmap. Would he ever consider a change in space settlement strategy in favor of O’Neill type free space colonies? Starship could certainly help facilitate the realization of that vision.

If all goes according to plan, SpaceX will attempt the first orbital flight of a Starship prototype sometime next year, which also happens to be when the next launch window opens up for trips to Mars. Obviously, nothing in rocket development goes according to plan, so the initial flight ready design is at least a year away optimistically. And we know Musk’s timelines are notoriously aspirational. As ambitious as Musk is in driving his company toward the goal of colonizing Mars, it seems unlikely that an initial uncrewed mission with all its flight ready automated hardware as described above could be ready by the next launch window in 2024. But what about 2026? NASA’s current plans for return to the Moon call for a human rated version of Starship as a lunar lander “…no earlier then 2025”. However, Japanese billionaire Yusaku Maezawathe’s Dear Moon mission sending 8 crew members around Luna with a crewed Starship is still planned for 2023. A lot of details are yet to be worked out and we still have not covered the topic of Planetary Protection nor the granting of a launch license to SpaceX by the FAA, but could a Starship human mission to Mars take place in 2028? Let me know what you think.

“The SpaceX Starship vehicle fundamentally changes the paradigm for human exploration of space and enables humans to develop into a multi-planet species.”

* Authors of Mission Architecture Using the SpaceX Starship Vehicle to Enable a Sustained Human Presence on Mars Jennifer L. Heldmann, Margarita M. Marinova, Darlene S.S. Lim, David Wilson, Peter Carrato, Keith Kennedy, Ann Esbeck, Tony Anthony Colaprete, Rick C. Elphic, Janine Captain, Kris Zacny, Leo Stolov, Boleslaw Mellerowicz, Joseph Palmowski, Ali M. Bramson, Nathaniel Putzig, Gareth Morgan, Hanna Sizemore, and Josh Coyan

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Moonwards: making our future on the Moon

Conceptual illustration looking up the length of a Moon Town residential habitat built in a trench going down the crater wall. Plants cover its roof, walls, and foundation. Credits: Kim Holder, CC-BY 4.0. NOTE: all images are similarly credited

SSP has posted about Moonwards in the past.  Kim Holder, creator of the realistic virtual lunar colony online game was recently interviewed on Hotel Mars by John Bachleor of CBS Eye on World and David Livingston of The Space Show.  Kim’s website is starting to mature to a point where I thought it was time to get an update and a deeper dive into her vision of our future living on the Moon. I caught up with Kim last week via email.

SSP: Thanks for taking the time to collaborate on this post Kim.  You’ve said that accurately depicting and roleplaying the activities of living on the Moon in a colony called Moon Town built by, and shared by, the players will help show the world the benefits of space development and a positive future.  Why do you think a role-playing online game is the best vehicle to accomplish this vision?

KH: Because interacting over time with a detailed simulation allows people to absorb what it means. It allows people to pick up knowledge about space development as they play. That’s a kind of learning that sticks. And the more players expand the vision, creating an ever cooler place with more things to see and do, the more they will feel a connection with that vision. They will naturally think about it more, talk about it more, pass on things about it to their friends and family. The kinds of dialogues they are able to have about it will gain depth and breadth, the more they work on it and see how others have worked on it.

“We need to understand what’s coming and make sure we do this right.”

It’s long been said that simulations of this kind will become a major means of education and research once the software and hardware to make them matures. Well, we’re arriving at that day. It’s a question of properly designing them now, to best serve our needs. I think space development is clearly the best choice of theme for the first such simulated environment, and a game based on creation and collaboration is the best design paradigm for it. I’d say there is no issue in the world so misunderstood and undervalued. We need to understand what’s coming and make sure we do this right. Otherwise it will take longer to see the massive benefits, and there are lots of things that could go really wrong.

Depiction of an android accompanying a resident in the shared kitchen, dining area, and spa facility of a neighborhood in Moon Town

SSP: You’ve done a lot of research to make the future technology of Moonwards scientifically accurate to give users a realistic prediction of what it will be like to live and work in space.   Why is this important?

KH: There’s lots of places out there where people can enjoy a space fantasy, and I’m a fan of a bunch of them. But to bring home why it’s important to devote big resources to space development, we have to leave no doubt that the benefits we portray will really happen once enough space infrastructure exists. I’ve generally been conservative about what’s portrayed so there’s no gap where someone could say it’s not gonna happen because this or that is fanciful. This is of course difficult because there’s so much we don’t know.

It’s the medical stuff that’s especially hard to account for, as you well know, John. In order for people to enjoy the game it has to portray a beautiful, exciting place. If it doesn’t do that nobody will be interested and it won’t achieve anything. I decided not to build the town in a lava tube, the place widely recognized as the safest, easiest place to build at scale on the moon. The most important reason I chose a large, young crater instead was to present that beautiful, exciting place. However huge a cavern is – and lava tubes on the moon could be hundreds of meters wide and thousands long, in theory – I didn’t feel it could be filled with a city nearly as attractive as one in a crater. No matter that it gives complete protection from radiation and dust, and it’s relatively easy to pressurize the entire thing. Once we can, I’m pretty sure we’ll make big fancy cities in craters or mountains, not tunnels. We’ll do what it takes to create a healthy place to live that has the sunshine and big outdoor views humans have evolved with. I’ve had arguments with people about that but I stick to it. It gives me an opportunity to discuss what systems would be needed and how they could be made on the moon. It gives people a relatable way to learn about such things, and to ponder both the vast scale of this undertaking, and that it’s entirely feasible.

“This isn’t about exploring space. This is about changing human existence. We have to demonstrate this can really be done.”

As people play this game, I want real questions to well up in them for the game world to properly answer. If you want people to really question whether this kind of vast industry and construction is both possible and desirable in space, a place of beauty and wonder has to instill those questions. Then, they must be answered thoroughly with the best science we have. Moonwards isn’t shy about scale, we show things that couldn’t be built without a robotic workforce rivaling the human workforce that built the Panama Canal. When someone is convinced something like that can really be made, that person becomes a true convert. This isn’t about exploring space. This is about changing human existence. We have to demonstrate this can really be done.

Image of a Moon Town resident outside in a capsule spacesuit, on the roof of the first park, with its giant window. The main park is in the distance, its giant stone arches protecting the space from radiation but letting in lots of sun

SSP: Moonwards is open source to encourage collaboration among “Makers” to build out the community of Moon Town.  Who are these Makers and what qualifications do they need to participate?

KH: The communities we’ll be wooing directly will be those of space science and industry, and amateur game developers. We need a few more things done before actively bringing in a select few from those communities. The first set of Makers will advise us on design and test our collaboration tools. They’ll use those tools to add things to the game world once we’ve got the version that makes the process a pleasure. Beyond that point, the task is to grow a culture of Makers who decide themselves how the town develops. We just support that process – giving them more and better tools, adding new game destinations for them to work on (eventually starting with an O’Neill cylinder once Moonwards is established), helping polish what they make, and building a rapport with them so together we make the best vision of the future we can.

“Makers develop the major parts of the town, all the things that really require sound engineering.”

So, while initially we’ll be seeking out a small group of people with qualifications that leave no doubt they know how to design this simulation properly, once that group takes the lead in creating content, it will be their opinion of submissions that determines who joins the Maker ranks. We’ll set up the means for anyone to submit proposed content. A critique process will assist with refinements. If your submission meets standards, it’ll be approved and you become a Maker, with all the privileges that go with that. Anyone who does their homework and learns from feedback can acquire that status.

You see, Makers develop the major parts of the town, all the things that really require sound engineering. All such things need good review before being included, and also an active community that integrates new stuff into the whole, considering the overall design and needs of the town. There will be plenty of things that are the ordinary day to day parts of a living town that any player can create and add, and that’s just up to them, and anyone else who shares a space with them. They can make their own home and its contents, things for their neighborhood, shops and markets, even things like animals, robots, and human characters. Makers are a different deal. They expand the town itself and have a big voice in new cities. where to locate them, and how to portray them.

View from outside the ecosystem research lab, showing the ilmenite reactors producing iron and oxygen in the distance. Two robotic rovers are visible center right.

SSP: In the (hopefully near) future when the Full Town Life is realized, visitors will be able to cooperate using a Collaboration App to develop ideas and projects in a workshop space with a suite of 3D modeling tools.  How do you envision this functionality furthering space development?  Can you give some examples of how it would be used?

KH: (Rubs hands.) Well, I talked above about how Makers will be a culture of informed people able to make good realistic designs for space. So, let’s say a few of them are playing with ideas for systems to transport ore from mines to processing reactors. We’ll start with trucks designed for that. Maybe they wonder if conveyor belts are better for production beyond a certain scale. They draft something for that, and once they are done for the day, the work-in-progress is on display in the studio section of the main habitats. Someone passing by looks at it and realizes they haven’t accounted for the dust that will be flying around in much greater quantities in mining areas. They attach a note about it to the gears that are too exposed, perhaps including a quick 3D sketch of a protective casing, or a link to a library item that could be adapted for a fix. Someone else passes by, thinks it over, and leaves a note with a calculation of what production level would justify this and whether it makes sense. A third person takes a look, and adds a comment to the note about production levels concerning how ore quality could impact the calculation.

“…nothing stops real researchers from using our code and assets to help create simulations adequate for real engineering modeling.”

By the time the original team comes back to work on it some more, someone has proposed an alternate solution using a sort of cable car system with movable posts, and begun working on it in a nearby area of the studio. Someone’s suggested different kinds of buckets used to get the ore from the trench or shaft to the conveyor belt that then clip onto the belt and are taken away. They ask to officially join the team. Someone has provided a miniature map of the main mining zones for use in mocking up the routes for the conveyor belts so they can be optimized, and attached it to the project.

These things can all happen because people actually walk past other people’s work in the game. When they do, they are already in an environment that allows them to play around with the model and attach all sorts of things to it, without changing the version the team behind it is working on. Good design will create the best possible environment for collaboration we’ve ever had.

How much of that will transfer directly to the real world is impossible to say. We have hopes that with growth the quality and capabilities of the simulation aspect of the game will be so high, things created this way will genuinely shape real world designs. This is one of the reasons for the main project to be open source – that way nothing stops real researchers from using our code and assets to help create simulations adequate for real engineering modeling. Then, that can be contributed back to Moonwards and we can adapt it so the game is a better simulation. It can become a virtuous cycle.

Aside from whether real technology might actually be drafted in Moonwards, definitely people will pick up how to engineer by playing. There is huge potential for mentorship, training in creative problem solving, and evaluation of concepts in an environment that makes communicating complex ideas so much easier.

SSP: Eventually, there will be the capability of hosting events such as concerts, live plays, gallery displays, special interviews or discussions.  Why would this be an attractive place for visitors to experience events like these?

KH: The kinds of events that I imagine being really successful will draw on the environment, and the nature of the community. Let’s focus on large events, on a scale that requires high bandwidth to work. It’ll take a while to create that capability, but it’s the part that’s really fun.

“With amazing realism quickly becoming possible even in real time 3D rendering, … such events could be fantastic.”

If you go to a concert or a play, the avatars of the audience could be scaled down to be an inch tall, and be free to fly around a space half a meter high by 10 meters wide by 3 deep, arching around the front of the stage just a meter from the performers. You could see the avatars of the viewers closest to you, and anyone you came with, but those farther away could appear just as little lights. The performers could jazz up the event by switching at will between all kinds of avatars, and adding anything they want to the environment. With amazing realism quickly becoming possible even in real time 3D rendering, and live recording of real people in full 3D also quickly maturing, such events could be fantastic.

Of course, Moonwards is a tiny project compared to other ventures pushing into 3D platforms. But we have two advantages that could be a big deal. First, we are the first venture of this kind to be principally open source. Add-ons can be proprietary (some of ours will be, as will the server code), but the main bulk of the project will remain open source. This is attractive to people wishing to experiment with the medium, or who wish to be sure their personal data isn’t being exploited, or who would rather the Metaverse (aka the 3D web) doesn’t grow up to be dominated by a few giant companies, like social media is. It’s possible that could be a decisive factor in who grows over the next decade.

Second, our tribe is those who love space and futurism. If you want to hang out at events with our kind of people, then come to our events. Nobody else will offer a lecture about the formation of Lalande Crater in which the audience is inside a simulation of the impact event.

SSP: In May Moonwards launched a contest to begin upgrades to the virtual infrastructure of Moon Town.  Called “Create Lunar Infrastructure in Moonwards Baby!” or CLIMB!, the initiative was intended to draw in Makers to bring the game alive, with proposals submitted over the summer to compete for prizes.  How is the contest going?

KH: OK, part of me is tempted to skip this, but another part thinks it’s better to answer. Making this game has been hard up to now. Really, it’s going a lot better than it was – a lot – and we’ve already gotten farther along than most startup video game ventures get at this point. Still, we are a small team on a shoestring budget who go through many unexpected turns. Other tasks meant we were obliged to launch the contest later than we should have, with less resources than we’d have liked. Then an opportunity appeared to enter a business plan contest run by the National Space Society, taking place during the same time as CLIMB!. (Check it out – https://spacebizplan.nss.org/details/). That meant the person working on the contest – me – instead turned full time to writing the business plan. That includes moving up some revisions to the layout of Moon Town so they can be shown off in the plan.

We made some good contacts during the brief time we were actively promoting CLIMB!, but it seems clear there won’t be submissions this year. We’ll take what we’ve learned and make a bigger, better contest next year. We feel having regular contests for new content of various kinds will really help bring in Makers and spread the word.

SSP: Much of the laborious tasks in Moon Town are done by robots.  What will the inhabitants do there and what will be the economic benefits and incentives for average people to want to migrate there permanently?

“The answer to what people will do there is, what they are passionate about.”

KH: Ah the future – so much to think about. To scale up industry and transport in the Earth-moon system to the point where some goods from the moon can be sold for a profit on Earth, you really have to go all out with automation. You have to make maximum use of the fact the moon has no biosphere to harm, and turn all labor over to robots that can work in really dangerous environments. Once you manage to have robots make more robots using materials on the moon, and energy beamed from space solar power arrays powers the factories and transport, prices will drop and drop until you can compete with industry on Earth. Ok, if you buy that, then Moon Town is going to be the robot Mecca of the future. Robots don’t just do most of the laborious tasks, they do them all. Running a closed ecosystem on a world so hostile an unprotected person would die in less than a minute requires great care. People just plain aren’t trusted to always do everything important right. Robots do all that. The answer to what people will do there is, what they are passionate about.

I mean, it isn’t like robots won’t have taken most jobs on Earth by that time too. We’re going to have to decide how to assign value to things in a way that rewards merit in a world like that. What can humans do that even intelligent robots can’t? Things that have great emotional value to other humans. Things that help us define who we are. Arts. Sports. Caregiving. Spirituality. Exploration.

Now, that isn’t necessarily to say that a lot of average people will migrate permanently. At least, not to the town we are portraying first. It’s not a huge place, there is a lot a person would have to give up to live there. [See next question]. The city that comes after it would be better suited to welcome average people. The human population of Moon Town will be researchers and top engineers who benefit from being able to take a close look at their work on-site, artists, athletes, and a few administrators. Moon Town plans to embed depictions of their lives as stories woven into the world. Oh, also people with major disabilities who are taking advantage of how Moon Town permits body alteration on a level not legal on Earth, especially advantageous in a controlled, low gravity environment. And some people taking a shot at immortality. Literally.

SSP: Its been said that a space settlement will not be completely self-supporting and independent of Earth until children can be born and raised there.  Moonwards deals with human health in the Moon’s 1/6 gravity environment through the use of centrifuges to dose inhabitants for 3 hours a day of 1G conditioning to mitigate the known deleterious effects of lower gravity to human health.  But there appears to be no mention of children in Moonwards culture.  Given Moonward’s rigorous scientific accuracy, is the lack of children because of our knowledge gaps with respect to the gravity prescription?  Will this evolve over time as the Moonwards community is informed by advances in space medicine?

KH: Yes, it’s because of the knowledge gaps. It’s definitely completely unclear whether it’s possible to bear and raise healthy children on the moon. We also can’t anticipate in any way how we might work around that, if it isn’t possible. I’ll be comfortable depicting children in the O’Neill cylinder in orbit. We’ll get to that simulation in due course. With that option sitting there, why get into how to do it on the moon?

(PS – 3 hours a day is of course a total guess and was chosen to be relatively easy to work into gameplay. Media in the game will explain things like this.)

SSP: Speaking of centrifuges for human health in low gravity environments, your design of the health “Carousel” assumes a radius of 16 meters.  This relatively small size, as you have acknowledged, could lead to severe Coriolis effects potentially resulting in severe disorientation and nausea.  Have you considered a larger centrifuge design such as the one proposed by Gregory Dorais with a radius of 75 meters which could reduce the impact of Coriolis effects, and since Moonwards is depicted far enough in the future that this type of technology could be achievable?

KH: To be fair, the centrifuge portrayed right now is one of the first, in a hab that can’t accommodate anything bigger. The bet is that people who use the apparatus regularly adapt to the way it affects the inner ear, and then are able to use it without issue. This is the theory Al Globus puts forth, with a decent amount of evidence to back it up, based on experiments with centrifuges over the years. But as the town expands, centrifuges are made bigger and bigger.

I’m currently planning a thorough revisit to the town’s design. We are at a juncture in development where it makes sense to change and refine the models of the town, and I intend to take that pretty far. This time, the first habs built will be upright cylinders with rounded ends such that it’s possible to ride a bike around the walls so fast that you are pressed towards the wall with a force of one gravity. Nod of the hat to Jeff Greason for pointing that out. Then the first centrifuge will go in, not sure of the radius but at a guess, 40 meters. The bigger habs will be able to accommodate ones much larger still. But those will be in the hands of the Makers. I’m just making the first few things, and giving ample space for others to expand.

SSP: Currently, space exploration and development is primarily funded by government entities and is regulated by the Outer Space Treaty.  As such, these activities are by nature geo-political.  You’ve chosen not to deal with these challenges that will inevitably shape our future in space, and leap frogged ahead with the assumption that those issues have been solved.  Is the hope that people will be so attracted to the abundant resources and opportunities that Moonwards has to offer, that they will overcome their differences and come together to make it happen?

“Let’s focus on getting across how much better life will be if we pull this off. That’s what matters.”

KH: Heck, I don’t just assume they’ve been solved. I assume the very best decisions have been made along the whole journey, to lead to the very best outcome for space development.

The exercise here is to explore our potential. It’s also important to see how this could go wrong, but as soon as you get into that, you fail to communicate the thing that matters most. This isn’t another chapter in geopolitical expansion, akin to the colonial era. This goes right off the map of anything humanity has ever experienced.  Let’s focus on getting across how much better life will be if we pull this off. That’s what matters.

Visit Moonwards to download the game free of charge and start collaborating. Although somewhat dated, check out Kim’s appearance with Dr. Livingston, Haym Benaroya and myself on the Moonwards Panel at the 2017 Icarus Interstellar Starship Congress in Monterey, California.

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National Space Society publishes NRL research on opportunities and challenges for Space Solar Power

One of many proposed space solar concepts; depiction is not to scale. Image credit: Naval Research Laboratory

NSS just posted a link to a recent NRL report outlining the next steps needed to make space solar power a reality. We’ve linked to the report on our Space Solar Power page. The report concludes with six recommendations:

(1) Mature space solar’s functional technologies and develop advanced concepts, particularly for power beaming.

(2) Monitor and maintain parity with foreign developments to avoid technological surprise, and to reduce the chances of being faced with a breakout capability.

(3) Advance robotic in-space assembly and manufacturing technology. Investment in these fields could have spin-off dividends in areas as diverse as astronomy, intelligence, and space industrialization.

(4) Address regulatory hurdles, especially in the area of spectrum identification for power beaming.

(5) Track technological progress regularly in areas such as launcher reuse and satellite mass production.

(6) Strengthen relationships between defense and civilian agencies, as well as international partners.

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A definition of space settlement

Dale L. Skran of the National Space Society breaks down the term differentiating between individual permanent habitats and the general creation of a grander association of colonies:

“ ‘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.”