The economic benefits of the Variable-Pitch Screw Launch system

Conceptual illustration of the Variable-Pitch Screw Launch system showing a launch vehicle (white) being accelerated by an adaptive nut (orange) that magnetically couples to variable pitch screws in an evacuated tube. Credits: Phil Swan and Alastair Swan.

The Variable-Pitch Screw Launch (VPSL) system, is a revolutionary ground-based electromagnetic launch technology that leverages magnetic coupling and variable-pitch leadscrews to accelerate payloads to very high exit velocities (e.g., >11,000 m/s) at a fraction of the cost of traditional chemical rockets. In a paper authored by Phil Swan and Alastair Swan of the Atlantis Project, details are presented on how VPSL overcomes limitations of existing mass drivers, such as the switching constraints of linear motors and rail wear in railguns. Phil Swan appeared on The Space Show last January to discuss the concept with Dr. David Livingston.

The capital cost of a VPSL system scales with the square of exit velocity (ΔV2), a significant improvement over the exponential cost growth of chemical propulsion (exp(ΔV/ΔVe )) and the cubic scaling (ΔV3 ) of some linear motor components in mass drivers. The authors present results from a parametric model that estimates a $33 billion USD capital cost (2024 dollars) for a human-rated system capable of accelerating vehicles to escape velocity for Mars missions, positioning VPSL as a game-changer for cost-effective space exploration.

As humans begin to explore and develop space beyond low Earth orbit (LEO), missions to the Moon, Mars, asteroids and beyond will demand significantly higher delta-v than those needed for LEO operations, especially for human round-trips, which nearly double the velocity requirements. High delta-v missions also reduce crew exposure to cosmic radiation and optimize provisions, but the rocket equation—where fuel mass grows exponentially with delta-v—makes traditional rockets increasingly expensive. VPSL is presented as a scalable, infrastructure-based solution that mitigates these costs, offering both economic and environmental benefits. By reducing reliance on chemical propellants, it aligns with global climate goals, marking a pivotal shift toward sustainable spaceflight.

As a starting point for economic considerations the Swans provided a historical context for exploration costs (in 2020 USD) of the Apollo Program ($257 billion), Space Shuttle ($197 billion) and the International Space Station annual costs ($500 million per-person-year; total of $150B to date); with an estimate that the Artemis Program will cost $93 billion through the end of FY2025 (likely over $100 billion by the time Artemis III returns to the Moon according to ChatGPT). Since the dawn of human spaceflight these programs demonstrate the immense financial burden associated with traditional (chemical rocket) spaceflight, yet their broader benefits—economic stimulus, technological innovation, and geopolitical prestige—justify the investment. The aim of VPSL is to reduce these costs dramatically.

The analysis then moves to a cost comparison of all rocket systems using empirical data that show an exponential relationship between launch cost and delta-v reflecting the “tyranny of the rocket equation” where higher velocities require exponentially more fuel, driving up costs for missions beyond LEO, which will become increasingly important as global space agencies push out into the solar system toward high delta-v destinations.

The paper contrasts the economics of rockets with mass drivers where the latter scale as the cube of the velocity (ΔV3) due to increased power demands at higher velocities. VPSL avoids this by converting electrical energy into rotational energy in screws, then transferring it magnetically to the payload, minimizing expensive pulsed-power electronics. For example, scaling a traditional mass driver from 100 m/s to 10,000 m/s increases costs by a million-fold as ΔV3 dominates, but a well designed VPSL mitigates this issue.

Cost curve generated from a digital twin computer model for the Variable Pitch Screw Launcher (dark blue) versus empirical curve fit for all-rocket systems (light blue) showing significant cost savings. Credits: Phil Swan and Alastair Swan

The specific implementation of a VPSL system is presented with an architecture targeting a 22-year Mars outpost program, with launches during Mars transfer windows. The payload is human-rated, assuming fit crews and acceleration couches, and is designed with sufficient capacity for life support, power generation systems, and rocket propulsion for in-space maneuvering as well as decent to the Martian surface.

This VPSL system includes a 774 km submerged floating underwater section, an 83 km underground ramp curving upward, and a 122 km aeronautically supported elevated tube with the exit aperture at an altitude of 15 km. The entire 979 km launching conduit would be evacuated to minimize drag with air locks at both ends, and face East to take advantage of the Earth’s rotation. For a Mars transfer orbit the exit velocity was calculated to be 11,129 m/s taking into account the Earth’s rotation.

VPSL system scale compared to the Hawaiian Islands, the site under consideration for implementation. Credits: Phil Swan and Alastair Swan

VPSL outperforms rockets for high delta-v missions, leveraging fixed infrastructure costs and low marginal launch costs. It’s quadratic cost scaling and sustainable design make it a transformative option when compared to rockets for high delta-v missions.

I reached out to Phil Swan after his appearance on The Space Show to discuss VPSL and he graciously agreed to participate in an interview with me via email to dive deeper into some of the challenges for implementation of the architecture of the Mars mission. His outstanding responses below are backed up with rigorous engineering reasoning and I thank him for his time collaborating with me on this post.

Many of my interview questions arose from public feedback he received from over 125,000 YouTube views of his presentation on VPSL at the International Space Development Conference last May (Section F of the paper). This approach will hopefully help ascertain what actions are needed to realize the system as well as further engineering development needed to advance it’s technical readiness level. The first two questions involve funding mechanisms for implementation.

SSP: There didn’t appear to be a funding mechanism proposed for the VPSL system although there were a few references to features that would provide incentives for investors. Do you envision the project to be funded by private venture capital, governmental sources or a combination through public/private partnerships?

PS: Our funding strategy is designed to attract private investment through a phased development approach, where some liquidity and financial flexibility is offered by allowing employees and early-stage investors to sell shares to later-stage investors as key technical and engineering milestones are met, similar to staged investment rounds in deep-tech ventures. It would be like many other tech startups where for many years the company’s primary focus is growth as opposed to profits. While we anticipate private venture capital to play a significant role, we are also exploring potential government grants or public-private partnerships to support critical advancements. Revenue generation from early-stage prototypes and other technologies we develop along the way may provide additional funding streams, but the most significant returns will come when we enable affordable interplanetary spaceflight.

SSP: The $33.3B price tag included capital and operations costs but I did not see research and development included. While your calculations show that VPSL costs are very competitive and environmentally beneficial when compared to rockets, this system will require significant development costs to reach TRL 9. Do you have an estimate of the R&D budget?

PS: We anticipate the R&D budget to be 10% of the total estimated capital and operational costs. Our research and development efforts thus far have led to substantial reductions in the estimated costs, so strategic investment in R&D can drive down capital expenditures and improve overall system profitability. For example, a while ago our R&D work led to an improvement where we placed grapplers on both sides of the screws instead of just on one side. This innovation dramatically reduces the forces transmitted to the brackets that support the screws. In this sense, R&D serves as a cost-reduction mechanism. If we do the right amount of R&D and focus it on the most important problems, it could end up paying for itself.

SSP: The remainder of interview questions probe deeper into issues identified through public feedback in Section F of your paper. With respect to constructing a 979 km long vacuum tube and designing fast-acting doors to maintain vacuum while allowing high-speed exit of the vehicle, what are the specific engineering requirements and cost estimates for designing and maintaining fast-acting airlock doors capable of sealing a vacuum tube after a vehicle exits at 11,129 m/s, and how do these compare to existing vacuum systems like LIGO (Laser Interferometer Gravitational-Wave Observatory)?

PS: To exit the tube, the vehicle will pass through an already open fast-acting door first, and that door will start closing immediately. The other end of the airlock is covered with a burst disk. The ambient air pressure at the airlock’s altitude (15km) is around 12000 Pa and the pressure inside the tube is 5 Pa. When the vehicle breaks through the burst disk, the rarified outside air will start travelling into the tube at the speed of sound. The fast-acting door needs to finish closing before the ambient air rushing into the tube reaches it. The math in the model estimates that to meet these requirements the airlock needs to be at least 288 m long if the fast-acting door is engineered to close in 1 second. I should add that the fast-acting door can be backed by a second slower door that is designed to achieve a better vacuum seal.

After the vehicle exits, a new membrane needs to be stretched over the end of the tube to from a new burst disk, and then the airlock needs to be pumped down again from 12000 Pa to 5 Pa. Our current model estimates that it will take 10 minutes and cost 312 dollars to pump the air out of the airlock each time we cycle it.

For LIGO, the exterior pressure is roughly 100,000 Pa and its interior pressure is 1.33 × 10⁻⁷ Pa to 2.67 × 10⁻⁷ Pa – which is a vacuum that it has maintained for 25 years. That’s a ratio of ~7e11 to 1. For VPSL, the exterior pressure is 12000 Pa and it has an interior pressure of 5 Pa for a ratio of only ~2.4e3. So, in one sense, LIGO’s vacuum engineering problem is eight orders of magnitude harder than the problem for VPSL. So, what we’re proposing here falls comfortably within established engineering capabilities. But, VPSL introduces operational dynamics that LIGO does not face – such as repeated venting and sealing at the airlocks and high-speed vehicle interaction. So, in another sense, we will be facing some new challenges that LIGO doesn’t have to deal with.

SSP: To address skepticism about sourcing materials robust enough to endure the high speeds, heat, and magnetic forces cost-effectively, you asserted that the choice of steel and aero-grade aluminum would have sufficient engineering margins when compared to rockets. What are the maximum stresses, thermal loads, and electromagnetic forces experienced by steel screws and aluminum tubes at peak speeds, and can existing manufacturing processes scale these materials to a 979 km system without cost escalation?

PS: This question assumes that extreme forces or heat are unavoidable, but that’s not how we approached the problem. From both an engineering and architectural perspective, we began with the constraints of existing materials and designed a system that stays within those limits.

For example, let’s start with the mechanical stresses. If we want a launcher for sending missions to Mars, this creates a requirement – we will need to launch vehicles at a speed of ~11,129 m/s relative to the surface of the spinning Earth. This is the speed at which the maximum mechanical stresses will occur.

The idea is that the spinning screws drive the adaptive nut. It’s basically a leadscrew and nut with a certain gear ratio. To figure out what that ratio needs to be, we first need to figure out how fast we can turn the screws without exceeding the stress limits of existing affordable materials. To ballpark that, we know that the yield strength for M2 High-Speed Steel can reach 1,300 to 2,200 MPa. But let’s assume we use a cheaper steel with a yield strength of 700 MPa and a density, ρ, of 7850 kg/m3. If we apply an engineering factor of 1.5, then we can set the maximum stress, σ, that we want to see in the steel to a value of 467 MPa. The rate that you can spin a spinning pipe without exceeding this level of stress is

[ref] where ω is in radians-per-sec, and ri and ro are the inner and outer radii in meters. Multiplying ω by ro gives the max rim speed of 404 m/s. This is a value similar to what the tips of airliner fans blades reach during takeoff.

From this value we can calculate the maximum slope of the screw flights, which is 11129/404=27. This means that the total force of the screw flights needs to be ~27 times higher than the force you need to accelerate the spacecraft, sled, and adaptive nut.

Since the coupling is magnetic, you can work out the coupling force across the “airgap” per square meter (see math in above linked paper). This works out to be 795775 N/m2, or less than 1 MPa (about 1/500th the internal tensile stress due to the centrifugal forces).

While you didn’t ask about this in the question, I feel that it’s important to mention that for this to work the screws and rails need to be very straight. To achieve that we will need automatic alignment actuators and something akin to an ultra-high-precision GPS system to achieve the required straightness.

You also asked about heating. This is a good question to use to validate the practicality of a launch architecture. For example, if a launcher was 1000 km long and it was made up of 1 million 1-meter segments, and each of those segments heated up by, say, 5 degrees each launch, then you could estimate how much energy was being dissipated as heat rather than being converted into kinetic energy—and it could be a lot. If each segment weighed one ton, heated up by 5°C, and had the heat capacity of water (about 4,200 J/kg·°C), then the total energy lost to heat would be:

1,000,000 segments × 1,000 kg × 5°C × 4,200 J/kg·°C = 21,000,000,000,000 J. That’s 2.1 × 10¹³ joules, or about 5.8 gigawatt-hours of energy lost to heating per launch.

By comparison, the kinetic energy of a 10-ton spacecraft (10,000 kg) in low Earth orbit at 7.8 km/s is:

(1/2) × 10,000 kg × (7,800 m/s)² ≈ 3.0 × 10¹¹ joules

So, the energy lost to heating in this example would be about 70 times greater than the kinetic energy delivered to the payload. In other words, such a launcher would not be very energy efficient.

In other architectures, this heat is generated because the segments rapidly convert energy from one form to another in the process of accelerating the vehicle, and such high-power conversions invariably generate heat. But the VPSL doesn’t rapidly convert energy from one form to another. The kinetic energy in spinning screws is directly channeled into the kinetic energy of the vehicle through what is essentially a magnetic worm gear. So, the screws and guideway will not heat up significantly during a launch because they are not heated up by the process of rapid high-power energy conversion.

Now there is still some friction that generates heat. Even a train on rails will generate some heat due to friction between its wheels and the rails, but the friction and heat generation associated with magnetic levitation systems is low enough that most people think of them as being “frictionless” – even though that’s not entirely true – maglev tracks and magnetic bearings are really just “very low” friction technologies.

SSP: Concerns were raised about potential eddy currents from the spinning screws and electromagnetic interactions causing energy losses and heat buildup which could reduce efficiency. In view of your acknowledgement that more engineering work is needed to quantify these interactions, have you calculated the magnitude of eddy current losses in a VPSL system at peak velocity, and have you designed experiments or computer code to run simulations or small-scale tests to determine how effective uniform magnetic fields and laminated components would be in reducing these losses?

PS: There are devices that are designed to use Eddy currents for braking, and there are technologies, such as magnetic bearings and maglev trains, that are designed to generate far less friction and wear than their mechanical counterparts. We’ve certainly designed devices to explore the limits of the low-friction high-speed magnetic levitation, but given the high speeds involved, we’ve chosen to implement these designs later on our prototyping roadmap. For one of them, we worked with a well-credentialed Ph.D. and an ASME Fellow in the field of rotordynamics and magnetic bearings. We shared our concerns with him about venturing into uncertain or poorly understood engineering territory. He reassured us that he was not aware of any engineering or physics reasons why our proposed technology would not work, and wrote us a letter of support where he stated, “I am confident in the merits of the proposed research.” That said, pushing beyond the speeds already achieved with maglev trains, the world-record-holding magnetic levitation rocket sled track at Holloman Airforce Base, energy storage flywheels, etc. certainly will involve doing more research and experimentation.

In addition to building physical prototypes, we plan to license advanced engineering software and bring on specialized talent to develop a multi-physics simulation using finite element analysis (FEA) techniques. These simulations will be validated through data collected from instrumented small-scale prototypes. They will give us more visibility on a wide variety of performance metrics.

SSP: Regarding fast-acting components, to ensure operational reliability and test real-world applicability of existing technology to VPSL’s extreme speeds, how reliably can electromagnetic grappler pads and actuators maintain synchronization and stability at speeds up to 11,129 m/s, and what are the failure rates of similar systems (e.g., magnetic bearings) under comparable conditions?

PS: It becomes easier to maintain synchronization as the vehicle approaches the muzzle of the launcher because the screw geometry changes more slowly at the muzzle end. Near the beginning, the geometry changes quickly and the grapplers need to reposition more rapidly, but the forces that they need to manage are also much smaller. If you haven’t yet seen Isaac Arthur’s video, “Mass Drivers Versus Rockets”, you should check it out. It has some good clips that show how the screw geometry changes and how the grapplers reposition during a launch.

Compared to ball and roller bearings, magnetic bearings exhibit extremely low failure rates in industrial use due to the lack of mechanical contact. Although, I suppose there must be some failures due to, for example, defective solid-state electronics in the controllers, power surges, corrosion of wires, fouling of sensors, etc.

Getting the failure rate to the level we need it to be at is a well-understood engineering exercise – like perfecting jet engines or building fault tolerance into hard drives. You need to test, iterate, and apply good engineering practices—refinement, redundancy, early fault detection, and so on. We will be building upon a substantial amount of experience that already exists within other industries – we’re not starting from scratch here.

SSP: You mentioned that to maintain investor confidence, you had a roadmap for developing the technology using a combination of physical prototypes and simulated “digital twin” prototypes. To address scalability physics and ensure the system can handle larger payloads effectively, how does magnetic field strength and consistency vary across a 979 km screw system compared to a small prototype, and what payload mass thresholds trigger performance degradation in digital twin simulations?

PS: Magnetic fields are not generated by the launcher’s guideway or screws’ flights (there are fields inside the magnetic bearings and electric motors that support and spin the screws though). Magnetic fields are generated by the adaptive nut and the sled. The strength of the fields between the grappler pads and the screw flights does peak as the vehicle approaches the muzzle end of the launcher. The strength of the fields between the sled and the guideway’s rail is constant during forward acceleration, and then it jumps up to its peak when the vehicle is on the ramp. Some of the small-scale prototypes will explore the same peak field strengths so that we can avoid surprises later as we scale up.

The system’s cost is expected to scale linearly with payload mass and payload mass will not trigger performance degradation. But if we were to go in the other direction, and scale down too far, that may introduce challenges – particularly with respect to vehicle stability and thermal protection during reverse reentry.

In the paper we said that cost scales with the square of delta-v – which is a lot better than the way that chemical rocket cost scales with the exponent of delta-v. However, we haven’t really explored how cost will scale at speeds much beyond 11,129 m/s. If we try to go much faster than that we’ll probably start running into material limits. Switching to more exotic materials will likely alter the cost-versus-delta-v relationship. We certainly do not want to suggest that the technology can scale up to the speeds needed for interstellar travel or anything like that.

SSP: To validate the economic and efficiency claims of VPSL when compared to existing rockets using energy data, have you done a detailed breakdown of the system’s $33.3 billion capital cost compared to the lifecycle cost of a chemical rocket program delivering 9.6 million kg to Mars, showing how much energy is saved by regenerative braking in real-world conditions?

PS: Yes, the capital and operating costs are computed by code within the digital twin and this includes the power savings from regenerative braking. While there has been some analysis of chemical rocket costs, much of our discussion in the public sphere revolves around addressing and correcting overly optimistic claims—particularly those made by Elon Musk—which are often repeated uncritically by some space enthusiasts. For example, this paper attempts to demonstrate that based on empirical evidence there is clearly an exponential relationship between cost and delta-v. As a widely circulated quote attributed to Peter Diamandis says, “Our brains are wired for linear thinking in an exponential world, and its causing us a great deal of strife.”

Personally, I haven’t felt it was in our best interests to publish a study that emphasizes how prohibitively expensive a permanently manned outpost—or a city—on Mars would be using chemical rockets. While some people argue that attempting to settle Mars is fundamentally misguided, I personally don’t share that view since I believe in the potential of launch infrastructure.

But if you think that rockets are the only option available to us, then right now the cost-per-kg to Mars is on the order of 1.2 million USD. While many are excited about Starship and the potential of full reusability, we’re far more cautious about its ability to fundamentally change the cost of spaceflight for the delta-v’s and mission durations required for one-way and round trips to Mars. We’ve shared some of our reasoning and the available data on this – see: https://youtu.be/Apu6nDahjB4 and https://youtu.be/GvqAM9p4hss. In the absence of a game-changing development, sending a million tons to Mars with chemical rockets will cost on the order of ($1.2 x 106 /kg )(1 x 109 kg) = $1.2 x 1015, or 1200 trillion dollars. This isn’t the kind of problem that will “fix itself” anytime soon through experience curve effects.

SSP: Related to your preferred site of Hawaii’s Big Island, the ongoing legal, cultural, and logistical hurdles encountered by Caltech and the University of California in getting approval to build the Thirty Meter Telescope (TMT) seem insurmountable. Native Hawaiian groups and environmentalists who consider Mauna Kea a sacred site have caused a decade of delays. The telescope’s future is still uncertain so a project of the scale of a VPSL system seems very challenging. While your plan to engage with the community in a respectful and productive manner by clearly communicating benefits to the indigenous people like economic opportunity and cultural legacy make sense, it has likely already been tried by the TMT team. Have you identified specific alternate coastal sites with high elevation, low latitude, and access to large bodies of water that may not present such difficult environmental and cultural challenges?

PS: The summit of Mauna Kea is a culturally sensitive area. For many Native Hawaiians, the numerous telescopes located there are seen as an incursion on sacred land. Additionally, the U.S. military has used portions of the mountain’s slopes for training exercises, causing ecological damage. As a result, the local population is particularly sensitive to further disruption and, in many cases, would prefer the mountain be restored to its original, undisturbed state.

The VPSL system’s acceleration segment would be located offshore and underwater, while the ramp portion would be on the island but almost entirely contained within a tunnel. The tunnel would exit well below the summit—away from the existing observatories—through a small opening situated to avoid culturally significant sites. The elevated, evacuated launch tube would be a temporary structure, deployed every two years for a few weeks during Mars transfer windows.

A potential path forward could involve a three-way agreement: the launcher could be used to deploy multiple space telescopes. These offer a path to eventually phase out the existing summit observatories without impacting the scientific community that relies on them. In return, the Hawaiian community would agree to permit the construction and limited use of the launcher, for example during Mars transfer windows and on a few other occasions.

Over time, the Hawaiian people may come to see the launcher not only as a less intrusive alternative but as a source of enduring pride—an opportunity to contribute to humanity’s next great era of exploration. Rather than diminishing their culture, it could elevate it, building upon the proud legacy of the Polynesian navigators who first discovered and settled the islands. This vision, however, must be informed by dialogue with Native Hawaiian leaders and cultural practitioners – not just outreach – to ensure the project is shaped in a way that reflects and respects their values. In this way, Hawai‘i’s role in space exploration could be seen as a modern extension of their deep tradition of voyaging and discovery.

But, if Hawaii choses to pass on the opportunity, there are many alternative sites around the world that would suffice. Developing and characterizing alternative sites simply hasn’t received priority yet.

SSP: What are the projected environmental impacts (e.g., land use, wildlife disruption) and cultural consultation costs for siting a VPSL system on Hawaii, and how do these compare to alternative sites like desert-mountain regions in terms of construction feasibility and community acceptance?

PS: We don’t expect there to be a significant amount of environmental disruption but with an ecology that’s very sensitive, we will need to be careful. The launcher is underwater and should not impede marine life. The ramp is within a shallow tunnel, so it shouldn’t affect ecologies on the surface, but we’d need to come up with a good plan for dealing with the excavated material generated during tunneling. I expect that birds would tend to avoid the elevated evacuated tube. Vehicles will exit the system far offshore and at an altitude of 15 km, so they shouldn’t generate a lot of noise. Rockets, on the other hand, generate a lot of noise and a lot of pollution from their exhaust. By eliminating the need for rocket launches, VPSL’s net benefit to the environment would be enormously positive.

To close out, we view VPSL not just as an engineering challenge, but as a test case for a new kind of sustainable, infrastructure-led approach to spaceflight – one grounded in realism, openness to critique, and collaborative development.

Split life cycle approach to settling the solar system

Left: Artist impression of the inside of Kalpana One, a free space settlement providing artificial gravity. Credits: Bryan Veerseeg / Spacehabs.com; Right: Conceptual illustration of a colony on the surface of Mars. Credits: SpaceX.

Until recently, space settlement advocates have typically split into two camps: those who favor building colonies on the surfaces of the Moon or Mars, and those who prefer constructing O’Neill cylinders in free space, spinning to provide artificial gravity outside of planetary gravity wells. Readers of this blog know I lean toward the latter, mainly because colonies on worlds with gravity lower than Earth’s could pose problems for human physiology, particularly reproduction. Truthfully, we won’t know if humans can reproduce in less than 1g until we conduct long-term mammalian reproduction experiments under those conditions. It would be far cheaper and quicker to perform these experiments in Low Earth Orbit (LEO) rather than waiting for sufficient infrastructure to be established on the Moon or Mars for biological research.

Another approach involves not sending humans into space at all, instead entrusting space colonization to human-level artificial general intelligence (HL-AGI) and conscious machines—a non-biological strategy. With recent advancements in AGI and automation, conscious HL-AGI robots may become feasible in the near future (though the exact timeline—whether decades or longer—remains a matter of debate). This prospect might disappoint many space advocates who view migration beyond Earth as the next phase of natural biological evolution hopefully starting within our lifetimes. Deploying sentient machines would effectively remove humanity from the equation altogether

If you’ve been following space colonization in the press you’ve most likely heard of the book A City on Mars by Kelly and Matt Weinersmith. I have not purchased the book but I’ve read several reviews and heard the authors interviewed by Dr. David Livingston on The Space Show to get an understanding of the Wienersmith’s overall viewpoint, which is at the very least skeptical, and to some space advocates downright anti-settlement. The book is very pessimistic taking the position that the science and engineering of space settlements for large populations of people is too challenging to be realized in the near future.

Peter Hague, an astrophysicist in the UK, wrote an excellent three part review setting the record straight correcting some of the critical facts that the Wienersmith’s get wrong. But in my opinion the best critique by far was written by Dale Skran, Chief Operating Officer & Senior Vice President of the National Space Society (NSS). In a recent post on the NSS blog, he links to a 90 page Critique of “A City on Mars” and Other Writings Opposing Space Settlement in the Space Settlement Journal where he provides a chapter-by-chapter, section-by-section response to the entire book as well as rebuttals to a few other naysayer publications [“Dark Skies” (2021) by Daniel Deudney; “Why We’ll Never Live in Space” (2023) in Scientific American by Sarah Scholes; “The Case against Space” (1997) by Gary Westfahl].

However, Skran credits the Weinersmiths with an innovative idea he hadn’t encountered before, one that addresses the challenge of human reproduction in low gravity. They suggest establishing orbital spin-gravity birthing centers above surface colonies on the Moon or Mars, where children would be born and raised in an artificial gravity environment—essentially a cosmic crèche. Skran builds on this concept, proposing that the life cycle of Moon or Mars colonists could be divided into phases. The first phase would take place in space, aboard rotating settlements with Earth-normal gravity, where couples would conceive, bear children, and raise them to a level of physical maturity—likely early adulthood—determined by prior research. Afterward, some individuals might opt to relocate to the low-gravity surfaces of these worlds. There, surface settlements would focus on various activities, including operations to extract and process resources for building additional settlements.

Skran elaborated on this split life cycle concept and outlined a roadmap for implementing it to settle low-gravity worlds across the solar system during a presentation at the 2024 International Space Development Conference. He granted me permission to share his vision from that presentation and emphasized that the opinions expressed in his talk were his own and did not reflect an official position or statement from the NSS.

Taking a step back, the presentation summarized research that has been performed to date on mammalian physiology in lower gravity, e.g. studies SSP covered previously on mice by JAXA aboard the ISS in microgravity and in the Kibo centrifuge at 1/6g Moon levels. The bottom line is that studies show some level of gravity less then 1g (artificial or otherwise) may be beneficial to a certain degree but microgravity is a horrible show stopper and much more research is needed in lower gravity on the entire reproduction process, from conception through gestation, birth and early organism development to adulthood. The question of reproduction in less then 1g is the elephant in the space station living room. In my presentation at ISDC last year, I took the position that the artificial gravity prescription for reproduction could impact the long term strategy for where to establish biologically self-sustaining space settlements leading to a fork in the road: a choice between O’Neill’s vision of free space rotating settlements vs. lower gravity surface colonies (because outside of the Earth all other solar system worlds where it is practical to establish surface settlements have less then 1g – e.g. the Moon, Mars, Asteroids and the moons of the outer planets – I exclude cloud settlements in Venus’s atmosphere as not realistic). I’ve been swayed by Skran’s proposal and have come to the realization that we don’t need to be faced with a choice between surface settlements or free space artificial gravity habitats – we can and should do both with this split life cycle approach.

How would Skran’s plan for settling the solar system work? He suggests we start small with rotating space settlements in LEO like Kalpana Two, an approach first conceived by Al Globus and popularized in his book coauthored by Tom Marotta The High Frontier: an Easier Way. Locating the habitats in LEO leverages the Earth’s protective magnetic field, shielding the occupants from radiation caused by solar particle events. This significantly reduces their mass and therefore costs because heavy radiation shielding does not need to be launched into orbit. In addition, the smaller size simplifies construction and enables an incremental approach. Kasper Kubica came up with a real estate marketing plan for Kalpana in his Spacelife Direct scenario.

Skran promoted a different design which won the Grand Prize of the NSS O’Neill Space Settlement Contest, Project Nova 2. The novel space station, conceived by a team of high school students at Tudor Vianu National High School of Computer Science, Bucharest Romania, slightly resembles Space Station V from the film 2001: A Space Odyssey. Many other designs are possible.

Project Nova 2 rotating space settlement, one possible design of a rotating space settlement initially built in LEO then moved out to the Moon and beyond. Credit: Tudor Vianu National High School Research Centre Team / NSS O’Neill Space Settlement Contest 2024 Grand Prize Winner

But to get there from here, we have to start even smaller and begin to understand the physics of spin gravity in space. To get things rolling Kasper Kupica has priced out Platform 0, a $16M minimum viable product artificial gravity facility that could be an early starting point for basic research.

Conceptual illustration of Platform 0, a habitable artificial gravity minimum viable product. Credits: Platform 0 – Kasper Kubica / Earth image – Inspiration4

These designs for space habitats will evolve from efforts already underway by private space station companies like Vast, Above, Axiom Space, Blue Origin (with partner Sierra Space) and others. Vast, which has for years had AG space stations on its product roadmap, recently revealed plans to use its orbital space station Haven-1 to be launched in 2026 to study 1/6g Moon level AG in a few years, albeit without crew. And of course let’s not forget last month’s post which featured near term tests proposed by Joe Carroll that could be carried out now using a SpaceX Falcon 9 as an orbital laboratory where researchers could study human adaptation to AG.

Illustration depicting a SpaceX Crew Dragon spacecraft tethered to a Falcon 9 second stage which could be spun up (in direction of down arrow) to test centrifugal force artificial gravity. Credit: Joe Carroll

Back the plan – once the rotating space habitat technology has been proven in LEO, a second and third settlement would be built near the Moon where lunar materials can be utilized to add radiation shielding needed for deep space. The first of these facilities becomes a factory to build more settlements. The second one becomes a cycler, the brilliant idea invented by Buzz Aldrin, initially cycling back and forth in the Earth Moon system providing transportation in the burgeoning cislunar economy just around the corner. The next step would be to fabricate three more copies of the final design. Two would be designated as cyclers between the Earth and Mars. Building at least two makes sense to establish an interplanetary railroad that provides transportation back and forth on a more frequent basis then just building one unit.

Here’s the crown jewel: the third settlement will remain in orbit around Mars as an Earth normal gravity crèche, providing birthing centers and early child development for families settling in the region. Colonists can choose to split their lives between rearing their young in healthy 1g habitats until their offspring are young adults then moving down to live out their lives in settlements on the surface of Mars – or they may choose to live permanently in free space.

This approach enhances the likelihood that settlements on the Moon or Mars will succeed. The presence of an orbiting crèche significantly reduces the risks associated with establishing surface communities by providing an orbital station that can support ground settlements and offer a 1g safe haven to where colonists can retreat if something goes wrong. This alleviates the pressure on initial small crews on the surface, meaning they wouldn’t have to rely solely on themselves to ensure their survival. Finally, an incremental strategy, involving a series of gradual steps with technology readiness proven at each stage through increasingly larger iterations of orbital settlements, offers a greater chance of success.

The final step in this vision for humanity to become a truly spacefaring civilization is to rinse and repeat, i.e. cookie cutter duplication and dispersal of these space stations far and wide to the many worlds beyond Mars with abundant resources and settlement potential. There’s no need to choose between strategies focused solely on surface communities versus spin-gravity colonies in free space. We can pursue both, as they will complement each other, providing families with split life cycle settlement options to have and raise healthy children while tapping the vast resources of the solar system.

Images of resource rich lower gravity worlds beyond Mars with potential for split life cycle settlement (not to scale). Top: the asteroid Ceres. Middle: Jupiter’s Moons, from left to right, Io, Europa, Ganymede, and Callisto. Bottom left: Saturn’s moon Titan. Bottom right: Neptune’s moon Triton. Credits: NASA.

A potpourri of artificial gravity topics

Conceptual illustration of three stages in the construction of an Artificial Gravity Orbital Station (AGOS), envisioned to be a potential replacement for the International Space Station. Credits: Werner Grandl and Clemens Böck

In this month’s post we explore a few concepts and challenges related to artificial gravity (AG) that when explored and understood will enable human’s to live healthy lives and thrive in space. First up, Austria-based architect and civil engineer Werner Grandl, a researcher of space stations and space colonies, and mechanical engineer Clemens Böck describe their concept for the evolving construction of a spinning Artificial Gravity Orbital Station (AGOS) in this Research Gate working paper. AGOS is envisioned as a potential successor to the International Space Station (ISS).

The primary aim of AGOS is to mitigate the adverse health effects of microgravity on humans by providing AG. This includes preventing bone density loss, muscle atrophy, and other physiological issues associated with long-duration spaceflight (more on this later). The station would also serve as a platform for scientific research under varying gravity conditions, potentially including zero-gravity, Mars-like gravity (0.38 g), and Earth-like gravity.

AGOS is proposed as a modular, rotating space station with an initial stage composed of four living modules for a crew of 24 and four zero-gravity central modules. The station is designed to be 78 meters in length, span 102 meters, have a rotation radius of 40 meters and rotate at 4.2 rpm to provide approximately 0.9 g of AG for comfortable living conditions. A non-rotating central hub would carry solar panels providing power as well as docking modules, connecting tubes, and a structural framework to maintain stability. The next stage would double the living quarter modules to eight for 48 occupants. The final configuration would finish out the station with 32 modules for 180 inhabitants.

While the ISS operates in microgravity, which is ideal for certain types of research, AGOS would provide a dual environment where both microgravity and AG conditions can be studied. This dual capability could enhance research in life sciences, materials research, and space technology development.

There are difficulties associated with the concept though, which will have to be resolved. The paper acknowledges that the engineering complexities of maintaining a rotating structure in space, ensuring stability, and dealing with the dynamics of spin gravity on the human body, especially disorientation caused by Coriolis forces, will be quite challenging to overcome.

Still, the future benefits made possible by AGOS will make overcoming these challenges worth the effort. When realized, AGOS would help enable more ambitious space exploration goals, including using the facility for human missions to Mars, where AG may be necessary and beneficial for long-term crew health during transit. It also could open avenues for commercial space ventures in Low Earth Orbit (LEO), including tourism and manufacturing under partial gravity conditions. Ultimately, AGOS could be a significant leap in space station design, enhancing both the scientific output and the prospects for human health in space for extended periods.

In a recent update on their concept penned by Grandl in ResearchOutreach, along with collaborator Adriano V. Autino, CEO of Space Renaissance International, they extend the possibility of constructing self-sustaining colonies in space via utilization of lunar and asteroid materials. Asteroids, in particular, could be hollowed out to serve as natural shields against cosmic radiation and micrometeoroids while mining for resources like metals and water.

Grandl describes a feasible design where a mined-out asteroid provides radiation shielding for a rotating toroidal habitat built inside the body for a population of 2000 people. Rotationally driven by magnetic levitation and natural lighting provided by reflected sunlight, the facility would mimic Earth gravity and environmental conditions for healthy living. This colony could sustainably support human life with integrated systems for air, water, food, and waste management.

Artistic rendition and cross sectional layout of an asteroid habitat for 2,000 colonists with a rotating torus driven by magnetic levitation while sunlight is reflected into the enclosure along the central axis illuminating the living space via a mirror cone. Credits: Werner Grandl

This approach would only work for larger solid body asteroids which are fewer in abundance and tend to be further away from Earth in the main asteroid belt. Smaller “rubble pile” bodies that are loose conglomerations of material like the Near Earth Object (NEO) Bennu recently sampled by the spacecraft OSIRIS-REx, could be utilized in an innovative concept covered a couple of years ago by SSP. The asteroid material is “bagged” with an ultralight carbon nanofiber mesh enclosure creating a cylindrical structure spun to create AG on the inner surface. Physicist and coauthor on this work Adam Frank, mentioned this approach when he recently appeared on the Lex Friedman podcast (timestamp 1:01:57) discussing (among many other space related topics) the search for life in the universe and alien civilizations that may have established space settlements throughout the galaxy and beyond (highly recommended).

A cylindrical, spin gravity space settlement constructed from asteroid rubble like that from the NEO Bennu. The regolith provides radiation shielding contained by a flexible mesh bag made of ultralight and high-strength carbon nanofibers beneath the solar panels. The structure is spun up to provide artificial gravity for people living on the inner surface. Credits: Michael Osadciw / University of Rochester

SSP has covered a scenario conceived by Dr. Jim Logan similar to Grandl’s but going big using several O’Neill Island One rotating colonies strung end-to-end in a tunnel drilled through the Martian moon Deimos.

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

The authors see the creation of these permanent spin gravity settlements in space as the next step in human evolution. This vision, once considered science fiction, is grounded in realistic engineering and scientific principals.

Back to the near future, Joe Carroll addresses two topics pertinent to how AG might help mitigate deterioration of human health in space in a couple of articles in the December 9, 2024 issue of the Space Review. In the first piece, Carroll poses the provocative question “What do we need astronauts for?”, and argues that robotic spacecraft have surpassed human astronauts in space exploration due to their ability to travel farther, endure harsher conditions, and deliver more data over longer periods at lower costs. This advantage will become even greater as robotic technology and AI progress in the near future.

As an aside, for the foreseeable future there will be a debate over humans vs. machines in space. Regardless of concerns related to risks to safety, costs, and physical limitations, humans will still have the edge over robots for a while when it comes to adaptability/problem solving, complex task execution, spontaneous scientific decisions and public inspiration. A collaborative approach, leveraging the strengths of both humans and robots to achieve more efficient and effective outcomes may be better for space development in the near term.

That being said, Carroll suggests that human spaceflight activities should be focused on assessing the viability of settlements off Earth, particularly by studying human health in lunar and Martian gravity. He emphasizes the lack of data on long-term health effects in low-gravity environments and proposes the use of AG systems in LEO to simulate lunar and Martian gravity for research purposes. Carroll concludes that understanding human health in low-gravity environments is crucial for future space settlements and that humans will play a vital role in this research.

This leads into his second article which provides suggestions on how to quickly test AG in LEO. He suggests launching and deploying a long, duel dumbbell variable gravity station composed of a Crew Dragon capsule tethered to a Falcon 9 second stage that rotates to produce AG. Providing lunar gravity at one end and Martian gravity at the other, the facility would provide an on orbital laboratory where researchers could study human adaptation to these conditions. Such tests would be more cost-effective and less risky than conducting experiments directly on the Moon or Mars.

Illustration depicting a SpaceX Crew Dragon spacecraft tethered to a Falcon 9 second stage which could be spun up (in direction of down arrow) to test centrifugal force artificial gravity. Credit: Joe Carroll

But there are challenges associated with determining appropriate spin rates. This is vital as they influence the station’s radius and cost. Previous studies using vertical-axis rotating rooms on Earth have shown that higher spin rates can cause discomfort, including nausea and headaches. However, these ground-based tests may not accurately represent the sensory effects experienced in space-based AG facilities, where the spin axis is perpendicular to the direction of gravity.

This approach, on which Joe graced the pages of SSP previously, could help determine whether human settlements on the Moon or Mars are feasible and sustainable, especially when it comes to human reproduction and agriculture in lower gravity levels. Incidentally, he contributed to my piece on the impact of the human Gravity Prescription on space settlement presented last May at the International Space Development Conference 2024.

And in case you missed it, Kasper Kupica shared with SSP his Spacelife Direct approach to quickly getting started by selling AG real estate in LEO.

Implementing AG in space habitats could enhance human health and improve various aspects of space station operations (e.g. fluid flow, heat conduction, fire safety) while enabling studies of human physiology under low gravity conditions. Conducting AG tests in LEO is a prudent step toward understanding human health, determining biology related requirements for future lunar or Martian colonies and may ultimately determine the long term strategy for space settlement.

Space solar power developments in 2022

Conceptual illustration of ESA’s SOLARIS space based solar power system. Credits: ESA

This year there were a lot of announcements and commentary regarding government support for studies that may lead to actual development activities for space solar power. These events, as well as some efforts by private companies, have been prompted by global initiatives to reduce carbon emissions toward net zero by midcentury in the hope of mitigating climate change.

Last January Japan codified into law an aggressive timetable to launch an end-to-end space solar power demonstration flight in LEO by 2025. From an English translation of Japan’s Basic Space Law provided by the National Space Society, the exact text reads “Each ministry will work together to promote the realization of space solar power generation. Concerning microwave-type space solar power generation technology, the aim will be to demonstrate by 2025 energy transmission from low Earth orbit to the ground.” If implemented on time, this would be the first such technical demonstration to be performed from space. Also, the fact that the initiative is codified into Japan’s laws means they are serious.

At a Royal Aeronautical Society conference last April in London called Toward a Space Enabled Net-Zero Earth, chairman of the Space Energy Initiative Martin Soltau outlined a 12-year timeline that would provide gigawatts of power from space for the UK by 2035. The Initiative, which is a collection of over 50 British technology organizations, has selected a space solar power satellite design called CASSIOPeiA after a cost benefit analysis performed by Frazer-Nash Consultancy initially covered by SSP. Incidentally, links to the final report by Frazer-Nash Consultancy completed in September 2021 and to the CASSIOPeiA system are available on the SSP Space Solar Power page.

At the International Space Development Conference in Washington D.C. last May, Nickolai Joseph of the NASA Office of Technology Policy, and Strategy (OTPS) announced an effort by the space agency to reexamine space based solar power. The purpose of the study is to assess the degree to which NASA should support its development.  Joseph said the report was to be completed by the end of September but as this post goes to press, it had not been released. Head of the OTPS, Bhavya Lal, tweeted last month that the report was in final review but this Tweet has been deleted without explanation. We are still waiting.

Three items on space solar power came up in September. First, John Bucknell returned to The Space Show to give an update on Virtus Solis, his space-based power system that SSP covered previously in an interview. With the novel approach of a Molynia sun-synchronous orbit, Bucknell claims that Virtus Solis will provide baseload capacity at far lower cost. In addition, the choice of orbits allow sharing orbital assets globally enabling solutions for multiple countries and regions. Bucknell hopes to have a working prototype to test in space within the next few years.

Schematic illustration of a three-array Virtus Solis constellation in Molniya orbits serving Earth’s Northern Hemisphere and a two-array constellation serving the Southern Hemisphere of Luna. Credits: Virtus Solis

Later in the month, the American Foreign Policy Council published a position paper on space based solar power in the organization’s publication Space Policy Review. From the introduction, author Cody Retherford writes that space solar power “…satellites are a critical future technology that have the potential to provide energy security, drive sustainable economic growth, support advanced military and space exploration capabilities, and help fight ongoing climate change.”

Overview of Space-based Solar Power from Figure 1 in American Foreign Policy Council report. Credits: AFPC and U.S. Department of Energy.

Also in September, the European Space Agency proposed a preparatory program called SOLARIS to inform a future decision by Europe on space-based solar power. The proposal was submitted for consideration in November at the ESA Council at Ministerial Level held in Paris.

The goal of SOLARIS, conceptualized in the illustration at the top of this post, would be to lay the groundwork for a possible decision in 2025 to move forward on a full development program to realize the technical, political and programmatic viability of a space solar power system for terrestrial needs.

Upon the conclusion of the ESA Council at Ministerial Level meeting SOLARIS was approved as a program. The Council confirmed full subscription to the General Support Technology Programme, Element-1, which requested funding for SOLARIS development.  The activities performed under Element 1 support maturing technologies, building components, creating engineering tools and developing test beds for ESA missions, from engineering prototype up to qualification.  Still to be determined: how much funding will be allocated by each member of the EU.

Then in October an article published in Science asks the question “Has a new dawn arrived for space-based solar power?” The authors bring to light what many advocates have already realized: that better technology and falling launch costs have revived interest in the technology.  Also in October, MIT Technology Review issued a report “Power Beaming Comes of Age”. Based on interviews with researchers, physicists, and senior executives of power beaming companies, the report evaluated the economic and environmental impact of wireless power transmission to flush out the challenges of making the technology reliable, effective and secure.

China announced in November that it plans to test space solar power technologies outside its Tiangong space station. Using the robotic arms attached to the station, they plan to evaluate on-orbit assembly techniques for a space-based solar power test facility which will eventually then orbit independently to verify solar energy collection and wireless power transmission. The China Academy of Space Technology has already articulated plans for development of their own space solar power system culminating in a 2 Gigawatt facility in geostationary orbit by 2050.

To cap off the year, aerospace engineer and founder of The Spacefaring Institute Mike Snead published a four-part series on evaluation of green energy alternatives including space solar power which he calls Astroelectricity. In the first part, he covers the history of humanity’s energy use and the dawn of fossil fuel use over the last century pointing out the fragility of the current system with respect to energy security. A gradual transition to fossil fuel free alternatives is needed to provide enough time for technology development and conversion over to green energy sources while not creating shocks to an economy based mostly on coal, oil and gas.

Next, nuclear power is addressed (and dismissed) as a green alternative with the next generation of smaller modular fission nuclear reactors currently under development. Due to waste heat challenges and nuclear weapons proliferation issues plus problems with scaling up enough of these power plants as base load supply to supplement intermittent wind and solar, this alternative is rejected as a viable green alternative. No mention is made of some the numerous fusion energy development activities in process or the promise of thorium molten salt reactors, so some readers may take issue with Snead’s position on this point.

In the third installment, if it is assumed that nuclear power is not a viable option, Snead examines to what extent wind and terrestrial based solar power has to be scaled up to replace fossil fuels in the latter part of this century given population growth and resulting energy needs. Not surprisingly, given the intermittent nature of wind and solar he finds these sources lacking, and they “… are not practicable options for America to go green.” Enter space solar power to fill the void.

In the last article in his series, Snead provides guidance for establishing a national energy security strategy for an orderly transition to green energy. He concludes that, “With America’s terrestrial options for going green not providing practicable solutions, the time for America to develop space solar power-generated astroelectricity has arrived. America now needs to pursue space solar power-generated astroelectricity to ensure that our children and grandchildren enjoy an orderly, prosperous transition to green energy.”

Finally, we close out the year with this: Northrop Grumman announced plans for an end to end space to ground demo flight in 2025 of their Space Solar Power Incremental Demonstrations and Research (SSPIDR) project funded by the Air Force Research Laboratory. SSP reported on the SSPIDR system previously. This development sets up a race between Japan, Virtus Solis (both mentioned above) and the U.S. government to be the first to beam power from space to the ground by the middle of this decade.

Mars as breadbasket for the outer solar system

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

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

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

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

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

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

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

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

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

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