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Biosphere X, Y and Z: The future of farming in space – guest post by Marshall Martin

Artist’s depiction of a space farm in a 56m radius rotating space settlement. Credits: Bryan Versteeg / Spacehabs.com

Editors Note: This post is a summary of a presentation by Marshall Martin that was accepted by the Mars Society for their conference that took place August 8 – 11th in Seattle, Washington. Marshall was not able to attend but he gave me permission to publish this distillation of his talk. There are minor edits made to the original text with his permission. Marshall is an accomplished Software Engineer with decades of experience managing multiple high tech projects. He has Bachelor’s Degree in Mathematics and Physics from Northwestern Oklahoma State University and an MBA in Management of Information Systems from Oklahoma City University. He is currently retired and farms with his in-laws in Renfrow, Oklahoma. The views expressed by Marshall in this post are his own.

The Earth is a Biosphere supporting life which has evolved and thrived on sunlight as an energy source for more than 3.4 billion years.

Therefore!

You would think a few smart humans could reverse engineer a small biosphere that would allow life to exist in deep space on only sunlight.

Furthermore, eventually the sun will run short of hydrogen and transition into a red giant making the Earth uninhabitable in a few hundred mission years. Long before that time, we need to have moved into biospheres in space growing crops for food. But for now….

The cost of food in space (when launched from Earth) is too high. My Estimates: [1,2]

Launch Vehicle/MissionCost/pound
(USD)		Cost/Person/Day*
(USD)
Space Shuttle to ISS $10,000 $50,000
Falcon 9 to ISS $1134 $5670
Atlas V [3] to Mars (Perseverance[4] Mars Rover) >$100,000 $500,000
2 year mission to Mars based on Atlas V costs >$100,000 $365,000,000
* Assuming average consumption rate of 5 pounds/day

If we assume that the SpaceX Starship will reduce launch costs to Mars by at least two orders of magnitude, the cost/person/day for a two year mission would still exceed $3 million dollars.

Solution: farming in space

Starting with a rough estimate, i.e. a SWAG (Scientific wild-ass guestimate): – A space station farm sized at 1 acre producing 120 bushels per acre of wheat, 60 pounds per bushel, 4 crops per year, yields 28,000 pounds of wheat per year.  Using Falcon 9 launch costs, this produces a crop valued at $31.7M per year.  If your space farm is good for 50 years, the crops would be worth $1.585B when compared to an equivalent amount of food boosted from Earth at current launch costs.

SWAG #2 – I believe a space farm of this size can be built using the von Braun “Wet Workshop” approach applied to a spin gravity space station composed of several Starship upper stages at a projected cost of $513M. More on that later.

Do we know how to build a space farm?    NO! 

So how do we get there?

Biosphere X would be the next generation of ground-based Biospheres.  You may consider the original Biosphere 2[5] as the first prototype.  As an initial SWAG, it was marginally successful.  As the design basis of a working space farm, it is nowhere close.

Image of the iconic Biosphere 2 experiment that attempted two missions, between 1991 and 1994, sealing a team of nine and seven Biospherians, respectively, inside the glass enclosure. The facility is now used for basic research 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

Biosphere Y will be placed in Equatorial Low Earth Orbit (ELEO) and will be based on the best iteration of Biosphere X.

Biosphere Z will be a radiation hardened version of Biosphere Y for deep space operations.

Key  Metrics:

People per acre is an important metric.  Knowing how many people are going to be on a space station or spaceship will imply the size of the farming operations required. [6]

Labor per acre is important.  It determines how many farm workers are needed to feed the space population (assuming there will be no automation of farm operations).  Note: every American farmer feeds about 100 people.  Obviously, if it takes 11 farmers to support 10 people in the biosphere, that is a failure.  If it takes 2 farmers to support 10 people that implies that 8 workers are available to work on important space projects.  Like building the next biosphere that is bigger and better.

Cost per acre will be the major cost of supporting a person in space.  There will be a huge effort to reduce the cost of space farmland.

Water per acre required to grow the crops.  Since there is a metric for people per acre, the water per acre would include the water in the sewage system.  I would think the water for fish farming would be separate or an option.

Soil per acre is literally the amount of dirt needed in tons.  This gets fun.  Will Biosphere X use hydroponics, aeroponics, light weight dirt, or high quality top-soil?  It could be just standard sandy loam.  The quality of the soil will have a big impact on what crops can be grown, which in turn, has a big impact on People per acre.

Watts per acre is the power required to operate a farm.  Another major cost of food grown in space.  Direct sunlight should be very cheap via windows, at least for biospheres in ELEO. In deep space far removed from the protection of Earth’s magnetic field, radiation would pose a problem for windows unless some sort of angled mirror configuration could be used to reflect sunlight adjacently.  Electricity from solar panels has been proven by ISS.  Power from a small modular nuclear reactors might be a great backup power for the first orbiting biosphere.  Note, diesel fuel would be extremely expensive and emissions would cause pollution to the biosphere in space; that implies, farming would be done using electrical equipment.

Improvements based on the Biosphere 2 experience to make a successful Biosphere X:

  • Updated computers for: better design, data collection, environmental control systems, subsystem module metrics, communication.
  • Oxygen production:  Greenfluidics[7] (algae farm subsystem)
  • Improved windows:  2DPA-1 polycarbonate[8]  vs. ISS windows[9]
  • Robots vs. manual labor.  (and better tools)
  • Soil vs. regolith vs. aeroponics vs. hydroponics vs. ??
  • Improved animal and plant selections

Cost of a Biosphere X compared with other ground-based facilities:

FacilityArea
(Acres)		Cost
(USD)
Biosphere 23.14$150M[12]
Regional Mall5.7$75M [13]
Walmart0.22$2.5M
Biosphere X1.0$10M 
Special building issues – SWAG: $20M

Biosphere X design options:

  • Crops: Wheat, Oats, Barley, Rye, Corn, Rice, Milo, Buckwheat, Potato, …
  • Animals: Fish, Goats, Chickens, Sheep, “Beyond Meat”, cultured meat …
  • Insects: Honeybees, edible Insects, Meal worms, Butterflies, …
  • Humans: I suggest 2 men & 2 women and work up from there.
  • Remote ground support: start big and reduce as fast as possible, goal = zero.

Testing Biosphere X:

Can a team live in the biosphere for two years?  (See Biosphere 2 test which was 2 years, i.e. a round trip to Mars and back)  How much food was produced?  Debug the biosphere.  Make upgrades and repeat the tests.  Calculate Mean Time to Failure (MTTF), Mean Time to Repair (MTTR), system flexibility, cost of operations, farming metrics (see above). etc.

With enough debugging, Biosphere X will become a comfortable habitat for humans of all ages.  This will include old people, children, and perhaps babies.  I think a few babies should be born in a Biosphere X (e.g. a few dozen?) before proceeding to Biosphere Y. Obviously, it may be challenging to find motivated families willing to make the generational commitment for long term testing required to realize this noble goal of space settlement. Alternatively, testing of Biosphere X could be simplified and shortened by skipping having babies, deferring this step to the next stage.

Biosphere Y potential configuration:

Once a reasonably well designed Biosphere X has been tested it will be time to build a Biosphere Y.  This will require figuring out how to launch and build the first one – not easily done! Let’s posit a reasonably feasible design using orbital spacecraft on the near-term horizon namely, the SpaceX Starship. Using nine upper stages with some modifications to provide spin gravity, sufficient volume could be placed in ELEO for a one acre space farm. Here’s one idea on what it would look like:

A central hub which we will call the 0G module will be composed of three Starship upper stages. Since they would not be returning to Earth, they would not need heat shield tiles, the aerodynamic steerage flaps, nor the three landing rockets. Also, there would not be a need for reserve fuel for landing. These weight reductions would allow the engineers to expand Starship and/or make more built-in structure and/or carry more startup supplies.

We will assume the current length of 165 feet with a 30 foot diameter. Three units placed nose-to-tail make 495 feet. But internally there would be 3 workspaces per unit: Oxygen tank, methane tank, and crew cabin. Times three units makes 9 chambers for zero gravity research.

The three units are connected forward and aft by docking hatches. Since the return to Earth engines have been deleted, the header tanks in the nose of Starship (the purpose of which is to offset the weight of the engines) would be eliminated allowing a docking port to be installed in front. In addition, with the 3 landing engines eliminated, there should be room for a tail end docking port. This will allow crew to move between the three Starship units in the 0G hub.

An aside: I am assuming that the nose of the station is always pointing towards the sun. The header tanks in the nose of the first unit could be retained and filled with water to provide radiation shielding to block solar particle events for the trailing units.

The 0G-units will need access ports on each of their sides to allow a pressurized access and structural support tube extending out to the 1G-units located at 100 meters on either side of the hub. This distance is calculated using Theodore W. Hall’s SpinCalc artificial gravity calculator with a spin rate of 3 rpm. There would be three access tubes extending out to connect to each of the 3 Starship 1G units. I assume the standard Starship has an access door which can be modified to connect to the tube.

Conceptual illustration of a possible configuration of an initial Biosphere Y in LEO using modified SpaceX Starship upper stages docked nose to tail. The station spins at 3 rpm around the central 0G hub with the outer modules providing 1G artificial gravity and enough volume for an acre of space farm. Credits – Starship images: SpaceX. Earth image: NASA

One or more standard Starships would deliver supplies and construction materials. They would also collect the three Raptor engines from each modified unit (36 in total) for return to Earth.

I note that the engineering modifications, methods and funding for operations in space to construct Biosphere Y have yet to be determined. However, applying a SWAG for launching the primary hardware to LEO:

This would require 18 starship missions. Using Brian Wang’s estimates of $37M per Starship[21] we get the following cost:

9 Starships times $37M per starship = $333M

18 Starship launches times $10M per launch = $180M

Total SWAG cost: $513M

What’s on the inside?

As mentioned previously, the interior of Biosphere Y will be a Wet Workshop utilizing the empty oxygen and methane tanks in addition to the payload bay volume (roughly 60ft + 39ft + 56ft long, respectively, based on estimates from Wikipedia), for a total length of 155 feet by 30 feet wide for each individual Starship unit.  With six 1G Starship units this amounts to about 657, 000 cubic feet of usable volume for our space farm experiencing normal gravity and its associated support equipment (half that for the 0G hub).

Note: Biosphere Y is designed to be placed in Equatorial Low Earth Orbit (ELEO).  This orbit is below the Van Allen belts where solar particle events and galactic cosmic ray radiation are reasonably low due to Earth’s protective magnetic field.

Since the first Biosphere Y will spin to produce 1G, eventually experiments will need to be performed to determine the complete Gravity Prescription[12, 13]: 1/2g, 1/3g, 1/6g and maybe lower.  You would think this would be required before trying to establish a permanent colony on the Moon and/or Mars in which children will be born.  This will probably require several iterations of Biosphere Y space stations to fine tune the optimum mix of plants, animals, and bio-systems.

What other things can be done with a Biosphere Y?

  • Replace International Space Station
  • Astronomy
  • Space Force bases in orbit
  • Repair satellites
  • Fueling station
  • De-orbit space junk
  • Assemble much larger satellites from kits (cuts cost)
  • Lunar material processing station
  • Families including children and babies[13] in space

Biosphere Z:

Once Biosphere Y is proven, it is ready to be radiation hardened to make a Biosphere Z.  I assume the radiation hardening material would come from lunar regolith.  It is much cheaper than launching a lot of radiation shielding off Earth.

Biosphere Z will be able to do everything that Biosphere Y can do – just further away from Earth.

After an appropriate shake-down cruise (2 years orbiting the Moon, Lagrange 1, and/or Lagrange 2), a Biosphere Z design should be ready to go to Mars. Note several problems will have been solved to ensure positive outcomes for such a journey:
• What does the crew do while going to Mars — farming.
• Building Mars modules to land on Mars
• The crew has been trained and tested for long endurance flights
• Other typical Biosphere Y, Z activities

Biosphere S  —  Major Milestone:

Eventually a biosphere will be manufactured using only space material, thus the designation Biosphere S.  Regolith can be processed into dirt.  Most metals will come from the Moon and/or Mars surface material.  Oxygen is a byproduct of smelting the metals.  Carbon and Oxygen can come from the Martian atmosphere.  Water can be obtained from ice in permanently shadowed regions at the Moon’s poles or from water bearing asteroids.  The first Biosphere S units will probably get Nitrogen from Mars.  Later units could get nitrogen, water, and carbon-dioxide from Venus[14].  From the Moon we get KREEP[15].  (potassium, Rare Earth Elements, and Phosphorus) found by the Lunar Prospector mission.

People, plants, livestock, microbes, etc. will come from other Biospheres.

Electronics will probably still come from Earth, at least initially, until technology and infrastructure matures to enable manufacturing of integrated circuits in space.

Artist’s depiction of an agricultural section of Biosphere S, which could be of the Stanford Torus design built mostly from space resources. Credits: Bryan Versteeg / Spacehabs.com

At this point, humans will have become “A space faring species”

In a century, the number of Biospheres created will go from zero to one hundred per year.

Marshall’s Conjecture:

“400 years after the first baby is born in space, there will be more people living in space than on Earth.”  After all, from the time of the signing of The Mayflower Compact to present day is about 400 years and we have 300+ million US citizens vs. the United Kingdom’x 68 million.

The explosion of life:

On Earth there are relationships between the number of humans, the number of support animals and plants.  There are currently 8 billion people on Earth and about 1 billion head of cattle.  I estimate that there are 100 billion chickens, a half billion pigs, etc.

As the number of Biospheres increases in number, so will the number of people, and the number of support plants and animals.  To state it succinctly, there will be an explosion of life in space.

So how many Biosphere S colonies can we build?

Let us assume that they will be spread out evenly in the solar “Goldilocks Zone” (GZ).  Creating a spreadsheet with Inputs: inside radius (IR), outside radius (OR) and minimum spacing; Output: Biosphere slot count.

Using: IR of 80,000,000 miles, OR of 120,000,000 miles, (120% to 33% Earth light intensity[16], respectively) and spacing of 1000 miles between Biospheres (both on an orbit and between orbits) you get: 40,000 orbits with the inner orbit having 502,655 slots and the outer orbit having 753,982 slots. This works out to over 25 billion slots for Biospheres to fill this region.  Assuming 40 people per Biosphere S implies a space population of over a trillion people. And that is only within the GZ. With ever advancing technology like nuclear power enabling settlement further from the sun, there is no reason that humans can’t expand their reach and numbers throughout the solar system, implying many trillions more.

Can we build that many Biospheres?

Let us assume each Biosphere S has a mass of one million tons (10 times larger than a nuclear powered aircraft carrier[17])  That implies 25.1×1015 tons of metal for all of them.  16 Psche’s mass is estimated at 2.29×1016 tons[18].  There are the larger asteroids, e.g. Ceres (9.4×1017tons), Pallas, Juno, Vesta (2.5×1017 tons) and several others.  Assuming the Moon (7.342×1019 tons) is reserved for near Earth use.   If the asteroids are not enough, there are the moons of Mars and Jupiter.  The other needed elements are readily available throughout the solar system, e.g. nitrogen from Venus, water from Europa, dirt from everywhere, so…

YES!  My guess is that it will take 100,000 years to fill the GZ assuming a construction rate of about 250,000 Biospheres per year.  That implies an expansion of the population by about 2 million people a year ( I acknowledge these estimates don’t take into account technological advances which will undoubtedly occur over such long stretches of time that may lead to drastically different outcomes. Remember! Its a SWAG!)

Is this Space Manifest Destiny?  Is it similar to the Manifest Destiny[19] in America from 1840 to 1900?  In my opinion, yes! But this is a very high-tech version of Manifest Destiny.  The bottom line assumption is that the Goldilocks Zone is empty — therefore  — we must go fill it!  Just like the frontiersman of the 1800s.

The First Commandment:

This gives a new interpretation of the phrase from the Book of Genesis,

             “Go forth, be fruitful and multiply“[20].

Not only are we people required to have children; but we are required to expand life in many forms wherever we go.  For secular readers, this may be interpreted as the natural evolution of life to thrive in new ecosystems beyond Earth. Therefore, the big expansion of life will be in space.

It all starts with Biospheres X, Y, and Z  optimized for farming in space

========

When considering humanity’s expansion out into the solar system, look at the concepts put forward above and ask: “Is this proposal missing a key step or two in the development of biospheres in space?”

Editor’s Note: Marshall appeared on The Space Show on August 27 to talk about his space farming vision. You can listen to the archived episode here.

References:

  1. B. Venditti, The Cost of Space Flight Before and After SpaceX, The Visual Capitalist, January 27, 2022
  2. M. Williams, How to make the food and water Mars-bound astronauts will need for their mission, , Phys.org, June 1, 2020, Paragraph 4
  3. Perseverance (Rover)/Cost, Wikipedia
  4. Perseverance (Rover) – Dry Mass, Wikipedia
  5. Biosphere 2, Wikipedia
  6. G.K. O’Neill, The High Frontier, 1976, p. 71 – based on Earth-base agriculture – 25 People/Acre; p72 – Optimized for space settlement (i.e. predictable, controlled climate) – 53 People/Acre.
  7. L. Blain, Algae Biopanel Windows Make Power, Oxygen and Biomass, and Suck Up CO2, New Atlas, July 11, 2022
  8. A. Trafton, New Lightweight Material is Stronger than Steel, MIT News, February 2, 2022
  9. Cupola (ISS module) -Specifications, Wikipedia
  10. Biosphere 2 (Planning and Construction), Wikipedia
  11. How much does it cost to develop a shopping mall?, Fixr, October 13, 2022
  12. J. Jossy, The Space Show with Dr. David Livingston, Broadcast 4061, July 25, 2023
  13. J. Jossy, The Impact of the Gravity Prescription on the Future of Space Settlement, Space Settlement Progress, March 29, 2024; J. Jossy and T. Marotta, The Space Show with Dr. David Livingston, Broadcast 3852, April 5, 2022
  14. Atmosphere of Venus (Structure and Composition), Wikipedia, “…total nitrogen content is roughly four times higher than Earth’s…”
  15. KREEP, Wikipedia
  16. Habitable zone (i.e. “Goldilocks Zone”), Wikipedia, Picture/graph, Top-right.
  17. Gerald R. Ford-class aircraft carrier (Design features, displacement), Wikipedia
  18. 16 Psyche (Mass and bulk density), Wikipedia – Note: the mass of all main asteroids are available on Wikipedia
  19. D. M. Scott, The Religious Origins of Manifest Destiny, Divining America, TeacherServe©. National Humanities Center, 2024
  20. Bible: Genesis 1:28 (Adam & Eve), Genesis 9:1 (Noah), Genesis 35:11 (Jacob), and generally repeated elsewhere in the book.
  21. B. Wang, Mass Production Rate of SpaceX Starship Costs, May 28, 2020

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The benefits of artificial gravity for space settlements

AI generated image of a rotating space station in Earth orbit providing 1g of artificial gravity in the outer ring, with partial gravity in the inner ring and microgravity at the central hub. Credits: Microsoft Designer

SSP has been covering research on artificial gravity (AG) and its impact on space settlement for years. Many of these posts have focused on the Gravity Prescription for human physiology with particular interest in reproduction as humanity will want to ensure that our space settlements are biologically self sustaining (meaning we will want to have children and raise them there). Should we discover that gravity levels on the Moon or Mars are not conducive to couples raising healthy offspring, rotating space settlements with AG may be our only long term option. But there are many other benefits that spin gravity cities can provide for settlers. In a position paper published online last May in Acta Astronautica, gravity researcher Jack J.W.A. van Loon leads a team of European scientists in an exploration of the possibilities and advantages of rotating space stations providing AG. Van Loon founded and manages the Dutch Experiment Support Center (DESC), which provides user support for gravity related research. This study posits a toroidal orbital station large enough and rotating at a sufficient rate to provide 1g of AG in an outer ring, with an intermediate location for partial gravity laboratories and a nonrotating microgravity research facility in a central module.

From an engineering and human factors perspective, pre-flight training would be simplified because practice operations and procedure planning can be performed on the ground in Earth’s normal gravity. Microgravity environments present challenges for physical phenomena like fluid flow, condensation, and heat convection. Provision of a gravity vector eliminates many of these problems simplifying design and use of equipment. This would also reduce development time.

Life support systems utilizing plants to provide breathable air and nutritional sustenance function more naturally and would be less complex in a biosphere with AG. Since plants evolved on Earth to develop gravitropism with roots growing down relative to a gravity vector and shoots sprouting upward, there is no need to develop complex systems to function in microgravity for proper water and nutrient supply as was necessary for NASA’s Passive Nutrient Delivery System aboard the ISS. There would be easier application of hydroponics systems and vertical farming could be leveraged in habitats with AG while harvested fruits and vegetables can be easily rinsed prior to consumption.

With respect to operations, tasks are similar to normal ground based activities so again, less training would be required. Clutter would be reduced and tie downs for tools that tend to float away in microgravity are not necessary. Schedule management would be improved because there would be less time spent on the extra exercise necessary to counteract health problems induced by exposure to microgravity. Activities like showering and sleeping can be challenging in the absence of gravity, so AG would improve the quality of life in regard to these and other routines we take for granted on Earth.

As readers of SSP are aware, the well documented deleterious effects of exposure to microgravity would be mitigated for crews in an AG environment. Such exposure could preserve crew health by preventing losses in bone and muscle mass, cardiovascular deconditioning, weakening of the immune system, vision changes, cognitive degradation and many other spaceflight induced pathologies as documented in the paper’s references. For tourists or visiting researchers, disorientation and days-long adjustment to microgravity due to Space Adaption Syndrome would be prevented.

Safety would be enhanced as well. For instance, combustion processes and flames behave very differently in microgravity making fire suppression less well understood when compared to normal gravity, necessitating development of new safety procedures. Free floating liquids and tools tend to move around unrestricted causing hazards that could potentially short out electrical equipment. Microorganisms and mold could present a health hazard as humidity control is problematic without a gravity vector. Surgery and medical procedures have not been developed for weightless conditions, requiring specially designed equipment and processes. Liquids drawn from vials containing drugs behave differently in microgravity because of surface tension effects. As mentioned above, training for all activities and equipment designed for use in Earth-normal gravity can be performed ahead of time on the ground. Testing of flight hardware would be simplified as it would not need to be redesigned for use in microgravity. Finally, decades of health studies on astronauts in space under microgravity conditions have found that pathological microorganisms are less responsive to antibiotics while at the same time, become more virulent. AG could make these microbes respond as expected on Earth.

The space station proposed in this paper would include an inner ring housing hypogravity facilities where AG equivalent to levels of the Moon and Mars could be provided for investigators to study and tourists to experience. Mammalian reproduction could be studied in ethical clinical experiments to determine if conception, gestation, birth and maturation to adulthood is possible in lower gravity over multiple generations, starting with rodents and progressing to higher primates. The central module would provide a microgravity science center for zero-g basic research or manufacturing where scientists could perform experiments then return to the outer ring’s healthy 1g conditions.

The author’s budgetary analysis found that the cost of such a facility would be about 5% higher than a microgravity habitat due to increased mass for propulsion and supplementary structures, but the benefits outlined above would be an acceptable trade off enabling a better quality of life for tourists and permanent inhabitants. This concept could be the first step in validating health studies and living conditions in artificial gravity informing the design of larger free space settlements.

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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, biologically self-sustaining space settlements for thousands of families to raise their children, establishing a beachhead from which to explore the rest of the solar system and preserve the light of human consciousness.

Update June 3, 2024: Here is a recording of my presentation on this topic at ISDC 2024.

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Progress on mammalian reproduction in microgravity

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. Credits:DALL∙E 3

We are one step closer to determining the gravity prescription for human reproduction in space. Okay, so we still don’t have the green light for having children at destinations in space with less than normal Earth gravity or higher radiation environments….yet. But a team of Japanese scientists report positive results after running an experiment aboard the International Space Station in 2019 that examined mouse embryos cultured in both microgravity and artificial gravity in space, then compared them to controls on Earth after a few days of development. The researchers published their results in a paper in iScience.

The researchers developed equipment and a protocol for freezing two-cell embryos after fertilization on the ground and launching them to the ISS where they were thawed then split into two groups, one allocated to growth in microgravity, the other treated with spin gravity to artificially simulate 1g. A control group remained on Earth. The procedure was designed to be executed by untrained astronauts. Cultured growth continued for 4 days after which the samples were preserved and refridgerated until they could be returned to Earth for analysis.

The samples were also monitored for radiation with a dosimeter and as expected aboard the ISS, were exposed to radiation levels higher then developing fetuses experience on the ground but far lower than those known to exist in deep space outside the Earth’s atmosphere and protective magnetic field. Still, this can be a “worst case” data point for radiation exposure to developing embryos as it is unlikely that pregnancy would be ethically sanctioned at higher levels.

Upon thawing by astronauts, the embryos were cultured through initial mitosis to eventual cell differentiation and blastocyst formation. A blastocyst is the multicellular structure of early embryonic development consisting of an an outer layer of cells called the trophectoderm surrounding a fluid-filled cavity in which an inner cell mass (ICM) called the embryoblast eventually develops into the embryo.

The study was concerned with how gravity may influence cell differentiation, the placement of the ICM within the blastocyst and if radiation effects gene expression in the these cells which will later develop into the fetus. Gene expression within the trophectoderm is also critical for proper development of the placenta.

The results were very promising as the data showed that there were no significant effects on early cell differentiation during embryo development and that proper gene expression manifested in microgravity when compared to 1g artificial and normal Earth gravity.

A human blastocyst with the inner cell mass at upper right. Credits: Wikipedia

A highlight of the paper implied that the results indicate that “Mammals can thrive in space.” It is too early to make such a bold statement with only this one study. It should be noted that this experiment only focuses on one early stage of embryo development. Conception in microgravity is not addressed and as pointed out by Alex Layendecker of the Astrosexological Research Institute, may have a whole other set of problems that raise ethical concerns as may the effects of lower gravity on later stages of gestation, in actual live birth and in early child development.

No matter how positive these recent results appear to be for early embryo development, as was determined by a landmark experiment on pregnant mice during the Shuttle era, we already have a data point on mammalian fetal development in later stages of gestation in microgravity: serious brain developmental issues were discovered in mice offspring born after exposure to these conditions. So mammalian reproduction in microgravity may start out relatively normally (assuming conception is successful) but appears to have problems in later stages, at least according to the limited data we have so far. On the bright side, the recent study found that 1g artificial gravity had no significant effects on embryo development.

Clearly more data is needed to determine which level of gravity will be sufficient for all stages of mammalian reproduction in space. Fortunately, SpaceBorn United is working on this very problem. They have plans for research into all stages of human reproduction in space to enable independent human settlements off Earth. SpaceBorn CEO Egbert Edelbroek in a recent appearance on The Space Show described upcoming missions later this decade that will study mammalian conception and embryo development using the company’s assisted reproductive technology in space (ARTIS). They have developed a space-embryo-incubator that will contain male and female mouse gametes, which upon launch into orbit, will initiate conception to create embryos for development in variable gravity levels. After 5-6 days the embryos would be cryogenically frozen for return to Earth where they would be inspected and if acceptable, placed in a natural womb for the rest of pregnancy and subsequent birth. If successful with mice the the company plans experiments with human stem cell embryos and eventually human gametes.

The gravity prescription for human reproduction in less than normal Earth gravity is still not known. But at least researchers are starting to gather data on this critical factor for long term biologically sustainable space settlement.

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Sex in space and its implications for space tourism and settlement

AI generated image of an amorous couple embracing in a space tourist destination. Credits: DALL-E

Last April, an international team of researchers published a green paper to solicit public consultation on the urgent need for dialogue concerning uncontrolled human conception which will be problematic for space tourism when it takes off in the near future.   A coauthor on the paper, Alex Layendecker of the Florida based Astrosexological Research Institute (ASRI) studied the subject for his PhD thesis. Layendecker gave a talk at ISDC 2023 entitled Sex in Space in the Era of Space Tourism in which he emphasized the huge knowledge gap we have on mammalian conception, gestation and birth in the high radiation and lower gravity environments of outer space.  Since humans evolved for millions of years in Earth’s gravity protected from radiation by our planet’s magnetic field and atmosphere, there is a significant risk of developmental abnormalities in offspring which could result in legal liability and potential impacts on commerce if conception occurs in space without consideration of the potential hazards.  After his talk, I discussed these matters and the implications for space settlement with Alex who agreed to continue our discussion in an interview by email for this post.

SSP: Alex, it was a pleasure meeting you at ISDC and thank you for taking the time to answer my questions on this important topic.  The green paper is attempting to foster discussion from relevant stakeholders on addressing “uncontrolled human conception”.  Uncontrolled is defined in the paper as “…without societal approval for human conception – i.e. without regulatory approval from relevant bodies representing a broad societal consensus.” I am not aware of any regulatory authority on these matters at this time and there will likely be considerable challenges to obtain consensus across the space community before tourism becomes mainstream. The intent of the paper appears to be to help develop a framework for regulations (or guidelines) before space tourism takes off. Given how long it takes for regulations to be implemented and the challenges of international consensus, will there be enough time to implement sufficient controls before conception happens in space?

AL:  Great question – short answer up front, no, I don’t believe any “controls” will be implemented before the first incidence of human conception in space, given the timelines we’re currently looking at.  As you mentioned, regulations can take a long time to come into effect and you need to have a basis for establishing regulations/law – space law itself is still being developed.  Our knowledge of reproduction in space is minimal at this stage, certainly not at the level it needs to be at this point of history.  We’re also in virtually unexplored territory when it comes to mass space tourism – there have been space tourists in the past, Dennis Tito being the first “official” space tourist in history over 20 years ago – but all previous individuals that went into space for tourism purposes have done so while integrated into the crew, typically with very little privacy and a considerable amount of training.  With mass access to space, we’ll soon have groups of individuals going up solely for vacation/leisure purposes, and you can be assured some of them will be engaging in sexual activity.  While it would be absurd to try to implement or enforce laws preventing sexual activity in those environments, the dangers associated with potential conception still exist.  What is critically needed at this point is a better collective understanding of those dangers, their mitigation, and for space companies to be able to provide those paying customers with enough information that informed consent can be established – space is inherently dangerous already, and people launching into space are briefed on that.  They will need to be briefed on the dangers associated with conception in space as well, which could not only potentially threaten the life of the baby but also that of the mother, depending on the times and distances involved.

SSP: Will this be a government effort (since a green paper typically implies government sponsorship) or a self-imposed industry-wide trade association consensus approach like CONFERS? Or a combination?

AL: I think in the immediate sense, there will need to be a self-imposed industry consensus on establishing informed consent among space tourism customers. Sex and potential conception in space is currently a blind spot for would-be space tourism companies, because up to this point many of them haven’t considered the dangers it could pose to their customers, and corporate liability here is also an issue. It’s their responsibility to keep their passengers safe, and to inform them of any dangers to the max extent possible. I don’t necessarily see governments being able to implement or enforce any regulations in this regard, because regulating people doing what they want with their own bodies in the privacy of their own bedrooms typically doesn’t fare well over the long term. Where governments may get involved is if any medical situation develops to the point of needing rapid rescue, but Space Rescue capabilities is another topic.

SSP: Space tourism is likely to attract thrill seekers and risk-takers who are likely to have rebellious personalities with a reluctance to follow rules and regulations, let alone respect for societal norms. If this is the case, will pre-flight consultations on the risks of uncontrolled conception and legal waivers be sufficient to prevent risky behavior? Can the effectiveness of this approach be tested prior to implementation?

AL: Prevent risky behavior? Absolutely not. As you point out, these are folks who are intentionally undertaking an enormously risky endeavor in flying to space already, and at least in the early years, will be primarily comprised of your limits-pushing, boundary-breaking types. So they’re already about risk as individuals. However, legal waivers will of course be part of the whole operation, likely to include waivers around the risks of conception. Waivers or not, people are still going to engage in sex in space, and relatively soon, and if the individuals in question are capable of conception, the act itself brings that risk. Not to mention that there are individuals out there who will be vying for the title of “first couple to officially have sex in space,” despite speculation over the years that it could have occurred in the past. To be part of the first publicly declared coupling in outer space will land their names in history books. Now, there will be individuals who decide that they don’t want to deal with those risks after a thorough briefing on the potential dangers, but not everyone – probably not even a majority, knowing humans – will be deterred.

SSP: The paper highlights concerns about pregnancy in higher radiation and microgravity environments. From a space settlement perspective, radiation is less of a problem as there are engineering solutions (i.e. provision for adequate shielding) to address that issue. The bigger challenge will be pregnancies in microgravity, or in lower gravity on the Moon and Mars. The physiology of human fetus development in less than 1g is a big unknown. Some space advocates such as Robert Zubrin brush this off with the logic that a fetus in vivo on Earth is developing in essentially neutral buoyancy, and is therefore weightless anyway, so gestation in less than 1g probably won’t matter. Setting aside the issues associated with conception in lower gravity, if a woman can become pregnant in space, do you think this logic may be true for gestation or are there scientific studies and/or physiological arguments on the importance of Earth’s gravity in fetal development that refute this position?

AL: I’ve heard the neutral buoyancy argument before but it doesn’t address all the issues by a long shot. There is more neutral buoyancy during the first trimester of gestation but in the second and third gravity is very important, even just logistically speaking. Gravity helps the baby orient properly for delivery, and helps keep the mother’s uterine muscles strong enough to provide the necessary level of contractions to safely move the baby through the birth canal. On a more cellular level, cytoskeletal development is impacted by gravity, so even proper formation and organization of cells can be affected by microgravity throughout the span of gestation, from conception to birth. Gravity has a huge impact on postnatal development as well – in the small handful of NASA experiments we’ve conducted using mammalian young (baby rat and mouse pups), there were significant fatality rates among younger/less developed pups against ground control groups when exposed to microgravity during key postnatal phases. The youngest pups (5 days old) suffered a 90% mortality rate, and any of the survivors had significant developmental issues. So gravity is crucial not just to fetal development but to newborns and children as well, that much is evident from the data we do have.

SSP: Following up on your response, the Moon/Mars settlement advocates will say partial gravity levels on these worlds may be sufficiently higher than in microgravity to address the issues you mentioned – baby orientation, cytoskeletal development, cellular formation/organization, postnatal development – and a full 1g may not be needed for healthy reproduction.  The mammalian studies you mentioned with detrimental postnatal development were in microgravity.   We now have a data point at the lunar gravity level from JAXA with their long awaited results of a 2019 study on postnatal mice subjected to 1/6g partial gravity in a paper in Nature that was published last April. The good news is that 1/6g partial gravity prevents muscle atrophy in mice. The downside is that this level of artificial gravity cannot prevent changes in muscle fiber (myofiber) and gene modification induced by microgravity. There appears to be a threshold between 1/6g and Earth-normal gravity, yet to be determined, for skeletal muscle adaptation.  Have you seen these results, can you comment on them and do you think they may rule out mammalian postnatal development in lunar gravity?  

AL: With regard to the JAXA study, I think I’ve seen a short summary of preliminary results but haven’t gotten to read the full study yet. What I will comment for now is that there’s at least some promise in those results from a thousand foot view. While we still need to determine/set parameters for what we as a society/species consider medically/ethically acceptable for level of impact (obviously there was gene modification in the JAXA mice), there are clearly still some benefits to even lower levels of gravity.

SSP: With respect to risk mitigation and the paper’s recommended area of research: “Consolidation of existing knowledge about the early stages of human (and mammalian) reproduction in space environments and consideration of the ensuing risks to human progeny”, SSP has covered off-Earth reproduction and highlighted the need for ethical clinical studies in LEO to determine the gravity prescription (GRx) for mammalian (and eventually human) procreation.  During our personal discussions at ISDC, you mentioned ASRI’s plans for such studies in space.  Can you elaborate on your vision for mammalian reproduction studies in variable gravity?  What would be your experimental design and proposed timeline?

AL:  Well, with regard to timelines, humanity as a whole is already behind, so we’ll need to move as quickly as we possibly can while still upholding safe medical and ethical standards.  We’re approaching an inflection point where human conception in space is more probable to occur, and we still have vast data gaps that need to be filled on biological reproduction.  I’d advocate that the best way to go about filling those gaps would be a systematic approach using mammalian test subjects to determine safe and ethically acceptable gravity parameters for reproduction.  We already know a decent amount about the impacts of higher radiation levels on reproduction from data gathered on Earth, but with microgravity we’ve still got a long way to go, and we don’t know what the synergistic effects of microgravity and radiation are together either.  With regard to experiments, NASA researchers have actually already designed extensive mammalian reproduction experiments with university partners, but those experiments haven’t been funded by the agency.  There was a comprehensive experiment platform called MICEHAB (Multigenerational Independent Colony for Extraterrestrial Habitation, Autonomy and Behavior) that was proposed back in 2015, around the time I was completing my PhD dissertation.  It would effectively be a robot-maintained mini space station that would study the microgravity and radiation effects on rodents in spaceflight over multiple generations, which of course requires sexual reproduction.  That experiment alone would prove enormously beneficial to data collection efforts.  It would be important to study said generations and physiological impacts at variable gravity levels as you mentioned – think the Moon, Mars, 0.5 Earth G, 0.75 Earth G and so on, so we could fine tune what level of impact we as a species are medically and ethically willing to accept in order to settle new worlds.  With regard to ASRI’s experiment roadmap, our intent is to start with smaller, simpler experiments that will garner us more data on individual stages of reproduction first using live mice and rats, with the hope of eventually moving on to complex and comprehensive experiments like MICEHAB.  Once we have a good plot of data over the course of many experiments, we can hopefully move on to primate relative studies to establish safe parameters for human trials.  I anticipate the small mammal experiments alone will take at least five years were we to launch our first mission at this very moment – though speed is often dependent on level of funding, as happens with most science.

SSP: If contraceptives are recommended to prevent conception during space tourism voyages, the paper calls for validation of the efficacy of these methods in off-world environments.  Do your plans for variable gravity experiments include such studies and how would you design the protocol?

AL: Well, the first important thing to remember is that contraceptives are known to fail occasionally on Earth – condoms can break (especially if used incorrectly), and even orally-taken birth control pills aren’t considered 100% effective. Currently ASRI doesn’t have plans for contraception studies because that’s further forward than we can reasonably forecast at this point. Frankly we need to establish medical parameters first regarding conception in space and know where the risk lines are before we implement birth control studies using humans. We have to take many small steps before we get there. Once we do have established limits for safe reproduction in space environments, we would look to operate any birth control studies within those parameters to determine efficacy. That way if the contraceptives do fail, we at least know the resulting pregnancy has a reasonable chance of success.

SSP: Should experiments on mammalian reproduction in variable gravity determine that fetal developmental or health issues arise after conception and gestation in less than 1g, do you think this may lead to a significant shift in the long-term strategy for space settlement (e.g. toward O’Neill type artificial gravity space settlements) if children are to be born and raised in space?

AL:  I certainly think so.  There’s a lot at stake here.  If we can’t safely birth and grow new generations of humans at a Martian gravity level (0.38 Earth G), then we’ve largely lost Mars as a destination for permanent multigenerational settlement. Fully grown adults can live and work down on the planet itself, but we’d need to come up with an alternate nearby solution for pregnant mothers and children growing up to certain age.  From an engineering perspective, artificial gravity space settlements like an O’Neill cylinder make the most sense to me personally, so long as there’s Earth-level radiation shielding and gravity, and you can recreate Earth-like environments within those structures.  During our conversation at ISDC I referred to it as an “Orbital Incubator” concept, though I’m of course not the first person to ever discuss something like that.

SSP: I appreciate you sharing your PhD Thesis with me. In that work you developed the Reproduction and Development in Off-Earth Environments (RADIO-EE) Scale to provide a metric that could help future researchers identify potential issues/threats to human reproduction in space environments, i.e. microgravity and radiation. Respecting your request that the images of the metric not be published at this time, qualitatively, the scale plots the different phases of reproduction, fetal development, live birth and beyond against levels of gravity or radiation in outer space environments encompassing the range from microgravity all the way up to 1g (and even higher). The scale displays green, amber, and red areas mapping safe, cautionary, and forbidden zones, respectively, dependent on location (e.g. Moon, Mars, free space, etc.). When I originally read your thesis I thought you included both gravity and radiation on the same chart but after our discussions I understand that they would have to be separated out. I also acknowledge that we have no data at this time and the metric is a work in process to be filled in as experiments are performed in space. Have you considered using three dimensions (gravity on x-axis, radiation on the y-axis, viability on the z-axis) and create a surface function for viability. Does that make sense?

AL: I’m totally with you on the 3D model scale (I’ve always thought of it like navigating a “tunnel” made up of green data points to reach the end of the reproductive cycle safely).  The scale was originally envisioned as separate graphs for Microgravity/Hypergravity and Radiation, but obviously we couldn’t combine those in 2D because those two different factors can vary wildly depending on where you’re physically located in the solar system/outer space in general.  So the best answer is to effectively plot green, amber, and red “zones” on each chart (again based on location), then make sure that wherever we’re trying to grow/raise offspring (of any Earth species) we’re keeping our expectant mothers and children in double-green zones (for both gravity, and radiation).  Now the third axis would actually be time (i.e. what point are you at in the reproductive cycle), with viability being determined by where all three axes meet in a green/amber/red zone.

I’d like to thank Alex for this informative discussion and look forward to further updates as his research progresses. We urgently need his insights to inform ethical policies and practices regarding reproduction for the space tourism industry in the short term, and eventually for having and raising healthy children wherever we decide to establish space settlements. Readers can listen to Alex describe his research live and talk to him in person when he appears on The Space Show currently scheduled for August 27.

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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.

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* ISU Space Studies Program 2021 participants:

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Tube Town – Frontier: Living beneath the surface of the Moon

A lunar sinuous rille (probable collapsed lava tube) Credit: NASA/Lunar Reconnaissance Orbiter (LRO)

SSP featured a post in 2020 on the promise of lava tubes as ideal natural structures on the Moon or Mars in which space settlements could be established. Some are quite voluminous and could contain very large cities. Lava tubes provide excellent protection from radiation, micrometeorite bombardment and temperature extremes while being very ancient and geologically stable.

How would a city be established inside a lava tube? What would it be like to live and work there? Brian P. Dunn paints a scientifically accurate picture of such a future in Tube Town – Frontier, a hard science fiction book visualizing life beneath the surface of the Moon. Dunn recently appeared on The Space Show where he provided tantalizing details on his book scheduled to be published later this year. You can also get a taste of the story through excerpts available on his website.

I’ve had the opportunity to get an advanced copy of his book and will be providing feedback to Dunn prior to publication. He agreed to an interview via email, summarized below, answering some of my initial questions:

SSP: Your first chapter of the book takes place in 2028 and starts out with teleoperated “SciBots” networked together in swarms to explore and prospect for resources at the Moon’s south pole.  They are battery powered and need to periodically recharge at stations at the base of solar power towers at the Peaks of Eternal Light, similar to what Trans Astronautical Corp. is planning with their Sunflower system.  This time frame seems overly optimistic given that NASA’s Artemis program won’t return astronauts to the Moon until the mid 2020s and Jeff Foust reported recently that a second landing won’t take place until 2 years later.  Would it be more realistic to move out the timeline 5-10 years?

BPD: As Kathy Lueders at NASA has said, our strategy with both Moon and Mars is ‘Bots then Boots’. There is much scientific and ISRU work that can be done before the humans arrive. (See the article on my blog “The Mother of All CLPS Missions.”)  With the Moon’s close proximity and communications satellites, we can teleoperate rovers much easier than on Mars. Regarding the SLS/Artemis timeline, I don’t believe it will ever reach full fruition. The Artemis/Gateway architecture is too expensive and too slow. There is a paradigm shift happening now as the concept of large, re-usable, re-fuel able, high payload, quick launch cadence rockets is being proven out with SpaceX’s Starship.

SSP: After discovery of the lava tube in which Tube Town is eventually established, the public “was clamoring for more” and the “excitement of the discovery of the tube breathed new life into lunar and space exploration”.  I know that I would be excited, and most space cadets would be as well, but why would the general public be so supportive of space exploration because of the discovery of a lava tube on the Moon?  A recent poll found that a majority of people think that sending astronauts to the moon or Mars should be either low or not a priority.

BPD: Now that we’re starting to get the rockets, the American public will soon see landers and rovers return to the Moon. This time it will be in HD TV. At some point Americans will return to the Moon. This will be must-see TV. Taikonauts will eventually land on the Moon. This will definitely light a fire under the Americans. Interest in the Moon and lunar exploration will go up. The problem will be sustaining interest (We have an incredibly short attention span). After the world record TV event, interest will wane. We will only be able to put a few astronauts in small habitats on the surface for short periods of time. Upon discovery of an intact lava tube people will know that we could actually build a town on the Moon. Even better than that guy described in that book… what was it called?

SSP: Tube Town is operated by an umbrella organization of national space programs led by NASA called the International Space Program.  How do you envision this cost sharing structure getting started?

BPD: Although much cheaper than a comparable sized surface base, outfitting a lava tube for human habitation will not be cheap. Much of the materials can be made in situ, such as aluminum sheeting for the floors and airlocks, waterless concrete, steel for pressure vessels to hold volatile gasses, but much will need to come from Earth such as Factory machines, computers, electronics, medical equipment, etc.

In Tube Town, this cost is spread among the space programs of 27 countries of the International Space Program (NASA, ESA plus 9 countries that signed the Artemis Accords).

US, Canada, Australia, New Zealand, Japan, South Korea, India, Brazil, Israel, United Arab Emirates, and the 17 member countries of the European Space Agency (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain Sweden, Switzerland and the United Kingdom). Notable holdouts were China (CNSA) and Russia (Roscosmos).

The ISP is a cost and opportunity sharing umbrella organization for building and maintaining a large Moon base and robotic creation of a Mars base and the first crewed mission to Mars.

NASA would be the lead partner of the ISP, but project decisions were approved and administered by the ISP Board of Directors consisting of the member countries of the organization with weighted voting rights proportionate to their contribution. Many countries wanted to get in on the ground floor of a new space economy but couldn’t afford to duplicate the resources and infrastructure that already existed at NASA. With their combined buying power, the ISP could source rockets, landers, robotics, space suits, etc. from the most efficient and innovative private suppliers. In return, ISP countries received habitation services (shelter, atmosphere, food, water) and discounted rates for:

  • leasing habitation space in the Tube for scientific or commercial enterprise,
  • buying propellant and other in situ resources, and
  • payload return to Earth

ISP construction costs of the Tube are initially off-set by lunar tourism and bespoke mining. Tourism licenses are issued by the ISP to private companies. The contracts include revenue sharing, ISP Code of Conduct compliance and Space Heritage sites preservation requirements. In exchange, the licensees get transportation, medical emergency and habitation services on the Moon.

In Tube Town, the first ISP tourism licensee is with Lunar Experience, LLC. LE licensed 50 seats for a seven Earth day stay. They ran two tours per Earth month to take advantage of the Nearside lunar day (in early days, most of the popular attractions were on the Nearside). LE agreed to give away 25% of the seats to people who could not afford the price. So, of the 50 seats per trip, 12 were free and 38 were paying customers. Assuming a ticket price of $5m for a trip to the Moon for a week, a flight made $190m. The revenue sharing agreement with the ISP was 60/40 (LE 60%, ISP 40%) so for that $190m flight, LE earned $114m and ISP $76m. If only two trips were completed per month, the yearly income would be LE $1.3B and ISP $912m. The ticket price would double to watch the uncrewed launches to Mars and the price would triple to be a part of history to witness the crewed launch to Mars.

In addition, the ISP or commercial customers could take advantage of very reasonable freight rates to backhaul refined payload on the returning tourist rockets to Earth. When would the price become affordable for regular people? Probably after the third tube is discovered. I could see an ISP member like UAE opening a large lava tube exclusively as a vacation resort.

SSP: The main product produced by Tube Town’s factory is spacecraft for Mars exploration and the eventual establishment of an outpost on the Red Planet.  Presumably, at least at first, not all electronic components can be made on the Moon so will have to be imported from Earth via a space-based supply chain.  Elon Musk is designing Starship to go directly to Mars from Earth.  Why does building spacecraft on the Moon for a Mars mission make economic sense when compared to “going direct” like Starship, and why isn’t Starship mentioned in the book? 

BPD: The book is a work of fiction so I try not to use real names or products. Although I think Starship is the first of its class of big, reusable rockets, I also think the concept will be replicated (like airliners) and hopefully there will be several options in the Earth to Moon supply chain. If you can make a big re-usable rocket on a beach in Texas, you can make one inside a nice lava tube on the Moon. We will also need to get lots of bots and machinery to Mars before the humans. This can also be manufactured on the Moon. When you launch, you don’t have to fight the giant gravity well of Earth  (12.6 km/s vs 2.6 km/s) and you may not even have to re-fuel to head for Mars. Huge payloads will be much more economical from the Moon.

Artist conception of a spacecraft manufacturer inside a lava tube. Credit: Riley Dunn

SSP: Tube Town has a Farm devoted to food production, waste re-cycling, and ice processing.  However, without insects or wind pollination it is not possible to grow desirable fruits and vegetables like apples, squash, melons and many more.  You devised an innovative way to pollinate the plants.  Tell us about that!

BPD: Nearly all of the technology described in the book is based on existing technology, whether in the lab or in production. Harvey’s pollinating space bees are based on a combination of miniature drone-delivered soap bubble pollination and AI image recognition software.

SSP: In your book, the Apollo 11 landing site becomes a tourist destination.  What steps are taken to preserve this fragile heritage site?

BPD: I think the Apollo 11 site is the must-see tourist attraction on the Moon. Part of that attraction is that you can still see the boot prints of the astronauts in the regolith. On the moon, boot prints are forever- unless another human destroys them. It only takes one knucklehead.

In my book, a regolith wall is built around the site to protect from plume drift from vehicles. The entrance is a good distance away from the site. Access into the site is in a plexiglass pod that is suspended above the surface. A cable system mounted on tall towers maneuvers pods of tourists through the site from above, giving them a close-up encounter, yet not disturbing the artifacts nor the regolith.

There should be multiple Space Heritage Sites on the Moon consisting of artificial artifacts from multiple countries and natural wonders like Schroter’s Valley. They should be identified and preserved by the tourist licensees that will profit from them.

Vallis Schröteri (Schroter’s Valley), believed to be volcanic in origin, is the largest sinuous rille on the Moon seen here as imaged by Apollo 15. Credits: NASA via Wikipedia

SSP: Tube Town has a centrifuge in the Rec Section to provide artificial gravity for residents to maintain their physical health, but very little detail is provided.  How often do residents use this facility, on average, and is it’s radius optimized to minimize Coriolis forces?  You might consider this well thought out design for a centrifuge.

BPD: I love this design for a lunar lava tube environment! The Rec section of Tube Town is over 400m wide so this is the perfect place for a floor mounted Dorais Gravity Train. In my book, this would be used for scientific study of the effects of artificial gravity treatment in a low gravity environment. They would do studies on both animals, plants and humans. I see crewmembers and tourists using the gravity train as a health spa and treatment against ‘gravity sickness’.

SSP: There are a couple of resident dogs in Tube Town and one them actually becomes pregnant.  This has huge implications for biomedical research on mammalian reproduction in lunar gravity and in particular, determination of the gravity prescription for healthy human gestation.  In my opinion, determination of the gravity prescription is one of the most significant questions to be answered for long term space settlement.  Tell us about how this research is carried out in Tube Town in an ethical manner?

BPD: The studies would start with mice. Only when and if the studies show that mammalian reproduction in low gravity is safe, would the crew move up to higher level mammals. If safe, the female dog would be taken off the canine birth control medication she is on. BTW, all the ISP crewmembers and commercial residents must agree to be on birth control medication while living on the Moon. Many may choose to freeze eggs or sperm on Earth before a long deployment in space.

SSP: Where on the Moon should we look for lava tubes?

BPD: Nearly all of the volcanic activity of the Moon was on the Nearside, not the Farside. So we should definitely concentrate on the Nearside. We can see lots of collapsed lava tubes on the surface of the Moon, the intact ones are probably in the same regions.

Global mosaic map of sinuous rilles identified across the Moon by the LRO Wide Angle Camera. Credits: NASA / D. Hurwitz, J. Head, H. Hiesinger, Planetary and Space Science via Semantics Scholar

My suggestion is to look for them where we would like to find them, in other words, lets look in strategic lunar base locations where there is water and power and easy access to other useful minerals (like metals).

 Multiple sinuous rilles (Aristarchus plateau area) Credit: NASA/LRO

I’m sure NASA knows better than me, but my target priorities would be:

  1. North Pole – because its near water and solar power and metals (the Northern Oceanus Procellarum and the highlands between the maria).
  2. South Pole – because its near water and solar power. The South Pole-Aitken basin is a large impact crater but apparently there was some later volcanic activity so it is possible to find tubes in the South Pole area but they may be smaller in size and length than the ones in the Maria.
  3. Marius Hills (southwest of Schroter’s Valley in Oceanus Procellarum) – because there is lots of volcanic activity and collapsed tubes and it is near minerals and metals.

SSP: Thanks Brian for your exciting vision of our future on the Moon and for the opportunity to get a sneak peek. I’m enjoying the story of Tube Town and wish you much success with the release of the book.

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Reproduction off Earth and its implications for space settlement

Launch of the Space Shuttle Atlantis (STS-66) on November 3, 1994. The mission carried an experiment called NIH.Rodent 1, the first of only two study’s to date on rats launched at mid-pregnancy and landed close to full term to study the effects of microgravity on reproduction. Credits: NASA

In a MDPI Journal Life paper, Alexandra Proshchina and a team* of Russian researchers summarize the research that has been performed thus far on reproduction of invertebrates in space. As mentioned in the article, the only data we have on mammalian reproduction in microgravity since the dawn of the space age is from two experiments carried out over 26 years ago. The studies looked at pregnant rats launched aboard the Space Shuttle on missions STS-66 and STS-70 in 1994 and 1995 respectively, and there have never been any births of mammals in space. This huge knowledge gap on reproduction in space is problematic for human space settlement. Yet Elon Musk, The Mars Society, and other groups are charging ahead with plans for cities on Mars. What if we discover that humans cannot have healthy babies in 0.38g? SSP has covered the quest for determining the gravity prescription before looking at JAXA’s effort to at least start experimenting with artificial gravity in space, albeit on adult mammals (mice). We are still waiting for JAXA’s published results of 1/6g experiments carried out in 2019.

The data from the Space Shuttle program only looked at part of the gestation period (after 9 days) and only in microgravity. The results did not bode well for reproduction in space. Some findings “…clearly indicate that microgravity, and possibly other nonspecific effects of spaceflight, can alter the normal development of the brain itself.”

Histological cross section through a representative rat brain from NIH.Rodent 1 experiment from STS-66. Left side (a) is low magnification and right side (b-d) are high magnification. Red arrows show areas of neurodegeneration. 1 – Nasal cavity, 2 – olfactory nerve, 3 – olfactory bulb, 4 – eye, 5 – cortex telencephali, 6 – hippocampus, 7 – fourth ventricle, 8 – cerebellum. Credits: Alexandra Proshchina et al.*

So we have this one piece of data for reproduction in microgravity and nothing in higher gravitational fields except what we know here on Earth in 1g.

Would partial gravity like on the Moon or Mars be sufficient for normal fetal development in rats (or mammals in general, especially humans) during the full gestation period? If problems are identified could it be extrapolated to human reproduction? The fact that homo sapiens and their ancestors evolved on Earth in 1g for hundreds of thousands of years is a big red flag for future space colonists that hope to settle on the surface of planetary bodies and have children.

We don’t know how lower gravity conditions could affect embryonic cell growth. How would the changes in surface tension and embryo cell adhesion be altered in these environments? We have very little data on cellular mechanisms and embryonic alterations that lower gravity may induce that could affect fetal development.

“There are also many other questions to be answered about vertebrate development under space flight conditions.”

A recent report on giving birth in space by SpaceTech Analytics looks at many of the factors that need to be considered for human reproduction off Earth. Most problems could be potentially mitigated through engineering solutions such as radiation protection, medical innovations tailored for space use, life support technology, etc. In this entire presentation the authors gave very little consideration to partial gravity affects on human embryos and child birth. One slide (number 70) out of 85 discusses these issues.

It is clear that more and longer term experiments will be necessary to determine how partial gravity affects the reproduction and development of mammals before humans settle space. Some researchers are actually considering genetic modification to allow healthy reproduction in space, and the ethical considerations associated with this course of action. Obviously, such a drastic methods would come only if there was no other alternative. One would think that building O’Neill type habitats rotating to produce 1g of artificial gravity would be preferable to such extreme measures.

Clearly, we need a space based artificial gravity laboratory to carry out ethical clinical studies on the gravity prescription for human reproduction, starting with rodents and other lower organisms. SSP recently covered a kilometer long version of such a facility that could be deployed in a single Falcon Heavy launch. And don’t forget Joe Carroll’s proposal for a LEO partial gravity test facility. Doesn’t it make sense to invest in such a facility and do the proper research before (or at least in parallel to) detailed engineering studies of colonies on the Moon or Mars intended for long term settlement? This research could inform decision making on where we will eventually establish permanent space settlements: on the surface of smaller worlds or in free space settlements envisioned by Gerard K. O’Neill. Elon Musk may want to consider such a facility before he gets too far down the road to establishing cities on Mars.

* Authors of Reproduction and the Early Development of Vertebrates in Space: Problems, Results, Opportunities: Alexandra Proshchina, Victoria Gulimova, Anastasia Kharlamova, Yuliya Krivova, Nadezhda Besova, Rustam Berdiev and Sergey Saveliev.

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When will the first human be born off Earth?

Space baby. Credits: scienceabc.com

One of the biggest challenges of space settlement facing humanity is procreation off world. We simply don’t know if its possible for a baby to be carried to term in less then one gravity. There are obvious ethical considerations of simply going there and trying it out. NASA is studying the problem but until we have a variable gravity centrifuge facility in space that will enable us to determine the “gravity prescription”, it will be a while before we have an answer.

In an article in The Space Review, Fred Nadis discusses some of the medical challenges of human reproduction in space and why one company, SpaceLife Origin, who’s mission was to enable human reproduction in space decided to suspend its planned missions for “Serious ethical, safety and medical concerns …”

These medical unknowns about reproduction in any gravitational field less then 1g is the obvious attraction of O’Neill type free space settlements which provide Earth normal gravity. But the huge scale and investment necessary to build such large scale settlements puts this approach far in the future. Al Globus thinks a better way might be to start with smaller spinning habitats in low earth orbit.

Asgardia’s has a key scientific goal of facilitating the first human childbirth in space which they believe is a crucial step on humanity’s “path to immortality as a species”. In preparation for that goal, the organization is creating the first sovereign nation in space. A good introduction to their plans can be found in an interview with Dr. Lena De Winne, the Head of Administration to the Head of Nation of Asgardia, who appeared on the Space Show recently.

Artist’s impression of the first human born in space. Credits: Asgardia