Image of ice in a crater on the Martian plain Vastitas Borealis captured by the European Space Agency’s Mars Express orbiter. Credits: ESA/DLR/Freie Universitat Berlin (G. Neukum)
When we establish outposts and eventually, settlements on the Moon or Mars it would be economically beneficial if we did not have to create supply chains from Earth for water, breathable air and the fuel we will need for our rockets. This is why sources of water ice in the permanently shadowed craters at the lunar poles and in glaciers in the equatorial regions on Mars are so attractive as early destinations. Once we get there what equipment will we need to process this valuable resource? The typical way envisioned for cracking water in situ on the Moon or Mars to produce oxygen and hydrogen is through electrolysis. But this method requires a lot of power. There may be a more efficient way. New ESA sponsored research by scientists* in the UK and Europe examines a novel method that mimics photosynthesis in plants using a photoelectrochemical (PEC) device. The findings were published June 6 in Nature Communications.
PEC reactors are currently being studied on Earth for water splitting to produce green hydrogen from sunlight. Since they only rely on solar energy for power they are ideal for space applications. One type of device consists of a semiconductor photocathode immersed in an electrolyte solution that absorbs solar energy for a reaction to split hydrogen from water molecules. Oxygen is produced at the anode of the cell. PEC devices can be fabricated as panels similar to photovoltaic arrays. For use on Mars, the authors analyze another similar PEC technology using a gas-diffusion electrode to reduce atmospheric carbon dioxide in a reaction producing methane for rocket fuel.
The authors modeled the performance of these devices subjected to the expected environmental conditions on the Moon and Mars. Specifically, they looked at attenuation from the accumulation of dust on the PEC cells caused by micrometeorites pulverizing the lunar surface, coupled with the solar wind inducing an electrostatic charge in the resulting dust. And of course dust storms are relatively frequent on Mars which could significantly degrade performance. To address this problem self cleaning coatings are suggested as a solution. Solar irradiance was also considered as it would be reduced at the orbit of Mars. It was concluded that the PEC performance could be significantly boosted with solar concentrators by a factor of 1000 enabling higher production rates and power densities, especially on Mars.
An added advantage for space-based application of this technology is the elements needed to construct PEC devices are readily available on these worlds obviating the need to transport them from Earth and thereby significantly reducing costs.
“…in-situ utilization of elements on both, the Moon and Mars, is feasible for the construction of PEC devices.”
The technology is ideal to augment the production of oxygen in environmentally controlled life support systems of habitats that may not initially be 100% closed and cannot easily be resupplied with consumables from Earth. A competing technology for oxygen production which was recently demonstrated on Mars is the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) which functions via solid oxide electrolysis of carbon dioxide. This process requires high temperatures and therefore, more energy presenting a challenge when increased production of oxygen will be required for large settlements. The author’s analysis show that the PEC devices are more energy efficient and can easily be scaled up.
“Oxygen production via unassisted PEC systems can … be carried out at room temperature … suitable to be housed in temperature controlled space habitats.”
* Authors of the Nature Communications article Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars: Byron Ross at the University of Warwick, UK; Sophia Haussener at Ecole Polytechnique Fédérale de Lausanne, Switerland; Katharina Brinkert, University of Bremen, Germany
Artist impression of an asteroid smelting operation. Credits: Bryan Versteeg / spacehabs.com
When humanity migrates out into the solar system we’ll need a variety of elements on the periodic table to build settlements and the infrastructure needed to support them such as solar power satellites. But before that future becomes a reality, there may be a near term market on Earth for precious metals sourced in space as transportation costs come down. There is also the added benefit of moving the mining industry off planet to preserve the environment. Could the asteroid belt provide these materials? Kevin Cannon, assistant professor at the Space Resources Program at the Colorado School of Mines describes the prospects for mining precious metals and building materials for space infrastructure asteroids in a recent paper in Planetary and Space Science. Coauthors on the paper Matt Gialich and Jose Acain, are CEO and CTO, respectively, at the asteroid mining company AstroForge which just came out of stealth mode last year.
The asteroids have accessible mining volume that exceeds that available on the Moon or Mars. This is because only the thin outer crust of these bodies is reachable by excavation, whereas the asteroids are small enough to be totally consumed resulting in higher accessible mining volume.
To-scale accessible mining volume of terrestrial bodies, calculated as the total volume for the asteroids (main belt mass of 2.39 x 1023 kg, mean bulk density of 2000 kg/m3), and as the volume for an outer shell 1.2 km in thickness for the Moon, Mercury, and Mars, equivalent to the deepest open pit mine on Earth. Note the combined volume of the near-Earth asteroids (~5 x 1012 m3) is too small to be visible at this scale. Figure 1 in paper. Credits K.M. Cannon et al.
The authors take a fresh look at available data from meteorite fragments of asteroids. Their analysis found that for Platinum Group Metals (PGMs), the accessible concentrations are higher in asteroids than ores here on Earth making them potentially profitable to transport back for use in commodity markets.
“Asteroids are a promising source of metals in space, and this promise will mostly be unlocked in the main belt where the Accessible Mining Volume of bodies greatly exceeds that of the terrestrial planets and moons”
PGMs are indispensable in a wide range of industrial, medical, and electronic applications. Some examples of end-use applications include catalysts for the petroleum and auto industries (palladium and platinum), in pacemakers and other medical implants (iridium and platinum), as a stain for fingerprints and DNA (osmium), in the production of nitric acid (rhodium), and in chemicals, such as cleaning liquids, adhesives, and paints (ruthenium).
It has been pointed out by some analysts that flooding markets here on Earth with abundant supplies of PGMs from space will cause prices to plummet, but the advantage of reducing carbon emissions and environmental damage associated with mining activities may make it worth it. The authors also point out that there are probably various uses where PGMs offer advantages in material properties over other metals but are not being used because they are currently too expensive.
Asteroids are rich in other materials such as silicon and aluminum which would be economically more useful for in-space applications. As the authors point out, some companies are already planning for use of metals and manufacturing in space such as Redwire Corporation with their On-Orbit Servicing, Assembly and Manufacturing (OSAM) and Archinaut One, which will attempt to build structural beams in LEO. Another example mentioned in the paper has been covered by SSP: the DARPA NOM4D program with aspirations to develop technologies for manufacturing megawatt-class solar arrays and radio frequency antennas using space materials. Finally, another potential market for aluminum sourced in space is fuel for Neumann Thrusters (although spent upper stage orbital debris may provide nearer term supplies). And of course, silicon will be needed to fabricate photovoltaic cell arrays for space-based solar power.
AstroForge will test their asteroid mining technology on two missions this year. Brokkr-1, a 6U CubeSat just launched on the SpaceX Transporter 7 mission last April, will validate the company’s refinery technology for extracting metals by vaporizing simulated asteroid materials and separating out the constituent components. Brokkr-2 will launch a second spacecraft on a rideshare mission chartered by Intuitive Machines attempting their second Moon landing later this year. Brokkr-2 will hitch a ride and then fly on to a target asteroid located over 35 million km from Earth. The journey is expected to take about 11 months and will fly by the body and continue testing for two years to simulate a roundtrip mission.
AI generated image depicting a propellant factory on the Moon. Credits: DALL-E
The economics of an in-space industry based on lunar-derived rocket propellant was examined by Florida Space Institute planetary physicist Philip Metzger in a prepublication paper submitted to arXiv on March 16 . The study will be published in the June issue of Acta Astronautica. Many skeptics of this approach believe that with launch costs plummeting, driven down primarily due to reusability pioneered by SpaceX, it will be cheaper to power the nascent cislunar economy with propellant launched from Earth rather then fuel derived from lunar ice mining.
In his analysis, Metzger examines a cislunar economy of companies that operate geostationary satellites which need to purchase boost services using orbital transfer vehicles fueled by cryogenic hydrogen and oxygen. The question is, would sourcing H2/O2 from ice mined on the Moon be competitive with launching propellant from Earth. He notes that previous studies that favored Earth to solve this problem were flawed because they compared the different technologies for mining water on the Moon (e.g. strip mining, borehole sublimation, tent sublimation, or excavation with beneficiation) rather than analyzing the economics of the cis-lunar economy as a sector.
With that approach in mind, Metzger develops an economic model with figures of merit to assess how various technologies for ice mining compare to Earth sourced propellant. One such parameter is the “gear ratio” G, which in the parlance of orbital dynamics, is the ratio of the mass of hardware and propellant before versus after moving between two locations in accordance with the rocket equation. The other key metric is the production mass ratio Ø, which is the mass of propellant delivered to a specific location divided by the mass of the capital equipment needed to produce the fuel.
The “tent sublimation technology” mentioned in the paper was invented by George Sowers and is featured in his 2019 NIAC Phase I Final Report on ice mining from cold bodies in the solar system covered by SSP previously.
Although G is constrained by the laws of physics, reasonable values are possible and a value of Ø ≥ 35 is the threshold above which lunar propellant wins out. The tent sublimation technology is estimated to have Ø over 400, an order of magnitude higher than the minimum to gain an advantage. Metzger’s new approach took into account that launch costs will eventually come down as far as possible but even then, found that lunar propellant can be produced at a competitive advantage. The only caveat is validation of the TRL and reliability of ice mining technologies.
“Lunar-derived rocket propellant can outcompete rocket propellant launched from Earth, no matter how low launch costs go.”
Although not included in Metzger’s study, a method for extraction of water from lunar regolith is heating by low power microwaves. A recent study found that this technology is effective for extracting water from simulated lunar soil laced with ice. It would be interesting to see if Ø for this technique exceeds the advantage threshold.
Developing the business case for lunar water is the first step in rapidly bootstrapping an off-Earth economy. Metzger has written about this previously where he sees robotics, 3D printing and in situ resource utilization being leveraged to accelerate growth of a solar system civilization.
Conceptual rendering of a Blue Alchemist solar cell fabrication facility on the Moon. Credits: Blue Origin
Jeff Bezos’ new initiative called Blue Alchemist made a splash last month boasting that the team had made photovoltaic cells, cover glass and aluminum wire from lunar regolith simulant. This is an impressive accomplishment if they have defined the end-to-end process which (with refinements for flight readiness) would essentially provide a turnkey system to fabricate solar arrays to generate power on the Moon. The announcement claimed that the approach “…can scale indefinitely, eliminating power as a constraint anywhere on the Moon.” Actually, this may not be possible at first for a single installation as surface based solar arrays can only collect sunlight during the lunar day and would have to charge batteries for use during the 14 day lunar night, unless they were located at the Peaks of Eternal Light near the Moon’s south pole. But if scaling up manufacturing is possible, coupled with production of transmission wire as described, a network of solar power stations in lower latitudes could be connected to distribute power where it is needed during the lunar night.
Very few details were revealed about the design outputs of the end products (not surprisingly) in Blue Origin’s announcement, particularly the “working prototype” solar cell. An image of the component was provided but it was unclear if the process fabricated the cells into a solar array or if the energy conversion efficiency was comparable to current state of the art (around 21%). Nor do we know how massive the manufacturing equipment would be, how much periodic maintenance is needed or if humans are required in the process. Still, if a turnkey manufacturing plant could be placed on the Moon and it’s output was solar arrays sourced from in situ materials, it would significantly reduce the costs of lunar settlements by not having to transport the power generation equipment from Earth. This particular process has the added benefit of producing oxygen as a byproduct, a valuable resource for life support and propulsion.
Research into production of solar cells on the Moon from in situ materials is not new. NASA was looking into it as recently as 2005 and there are studies even dating back to 1989. Blue’s process produces iron, silicon, and aluminum via electrolysis of melted regolith, using an electrical current to separate these useful elements from the oxygen to which they are chemically bound. Solar cells are produced by vapor deposition of the silicon. The older studies referenced above proposed similar processes.
It would be interesting to perform an economic analysis comparing the cost of a solar power system supplied from Earth by a company focusing on reducing launch costs (say, SpaceX) with that of a company like Blue Origin that fabricated the equipment from lunar materials. Peter Hague has done just that in a blog post on Planetocracy using his mass value metric.
Hague runs through the numbers comparing SpaceX’s predicted cost per kilogram delivered to the Moon by Starship with that of Blue Origin’s New Glenn. At current estimates the former is 5 times cheaper than the latter. Thus, to best Starship in mass value, Blue Alchemist would have to produce 5kg of solar panels for every 1kg of equipment delivered to the Moon, after which it would be the economic winner. Siting a recent analysis of lunar in situ resource utilization by Francisco J. Guerrero-Gonzalez and Paul Zabel (Technical University of Munich and German Aerospace Center (DLR), respectively) predicting comparable mass output rates, Hague believes this estimate is reasonable.
Perhaps we should not get ahead of ourselves as Blue Origin’s timeline for development of their New Glenn heavy-lift launch vehicle is moving a glacial pace and one wonders if they have the cart before the horse by siphoning off funds for Blue Alchemist. Jeff Bezos is free to spend his money any way he wishes and definitely seems to be in no hurry.
Conceptual illustration of New Glenn heavy-lift launch vehicle on ascent to orbit. Credits: Blue Origin
But SpaceX’s Starship has not made it to space yet either and after we see the first orbital flight, hopefully as early as next week, the company will have to demonstrate reliable reusability with hundreds of flights to achieve economies of scale commensurate with their predicted launch cost of $2M – $10M. As SpaceX has demonstrated with it’s launch vehicle development process it is not a question of if, it is one of when.
Image of full stack Starship at Starbase in Boco Chica, TX. Credits: SpaceX
As both companies refine their approach to space development, will it be the tortoise or the hare that wins the mass value price race for the cheapest approach to power on the Moon? Or will each company end up complementing each other with energy and transportation infrastructure in cislunar space? Either way, it will be exciting to watch.
Artist’s impression of a lunar landing pad. Credits: SEArch+
When humanity returns to the Moon and begins to build infrastructure for permanent settlements, propulsive landings will present considerable risk because rocket plumes can accelerate lunar dust particles in the bare regolith to high velocities which could result in considerable damage to nearby structures. Obviously, nothing can be done about the first spacecraft that will return to the moon later this decade unless they use their own rocket plume to create a landing pad like the concept proposed in a NIAC Grant by Masten Space Systems (now part of Astrobotic).
Flight Alumina Spray Technique (FAST) instant landing pad deployment during lunar landing. Source: Matthew Kuhns, Masten Space Systems Inc (now Astrobotic)
Therefore, before significant operations can begin on the Moon that require lots of rockets, a high priority will be construction of landing pads to prevent sandblasting by rocket plume ejecta of planned structures such as habitats, science experiments and other equipment. Several methods are currently being studied. Some require high energy consumption. Others could take a long time to implement. Still others are technologically immature. Which technique makes the most economic sense? Phil Metzger and Greg Autry examine options for the best approach to this urgent need in a November 2022 paper in New Space.
A lunar landing pad should have an inner and outer zone. The inner zone will have to withstand the intense heat of a rocket plume during decent and ascent. The outer zone can be less robust as the expanding gases will cool rapidly and decrease in pressure but will still be expanding rapidly, so erosion will have to be mitigated over a wider area.
Landing pad layout showing inner and outer zone measurements proposed in this study (Figure 1 in paper). Credits: Philip Metzger and Greg Autry / New Space – Lunar surface image credit: NASA.
Several processes of fabricating landing pads were examined by the authors. Sintering of regolith is one such technique, where dust grains are heated and fused by a variety of methods including microwave heating or focused solar energy. SSP has reported on the latter previously, but in this study it was noted that that technology needs further development work. Fabricating pavers by baking in ovens in situ was also examined in a addition to infusion of a polymer into the regolith to promote particle adhesion.
An economic model was developed to support construction of landing pads for NASA’s Artemis Program based on experimental data and the physics for predicting critical features of construction methods. Factors such as the equipment energy consumption, the mass of microwave generators compared to the power output needed to sinter the soil to specified thickness, and the mass of polymer needed to infuse the regolith to fabricate the pads were included in the model. Other factors were considered including the costs associated with program delays, hardware development, transportation of equipment to the lunar surface, and reliability.
When varying these parameters and comparing different combinations of manufacturing techniques, the trade study optimized the mass of construction equipment to balance the costs of transportation with program delays. The authors found that from a cost perspective, microwave sintering makes the most sense for both the inner and outer regions of the landing pad, at least initially. When transportation costs come down to below a threshold of $110K/kg then a hybrid combination of microwave sintering in the inner zone and polymer infusion of regolith in the outer zone makes the most sense.
Once astronauts land safely and begin EVAs on the lunar surface, they can keep from tracking dust into their habitat by taking an electron beam shower.
Other lunar dust problems and their risks can be mitigated with solutions covered previously on SSP.
Conceptual illustration of an oxygen pipeline located at the lunar south pole. Credits: Peter Curreri
This year’s list of NASA Innovative Advanced Concepts (NIAC) Phase I selections include a few awards that look promising for space development. For wildcatters (or their robotic avatars) drilling for water ice in the permanently shadowed craters at the lunar south pole and cracking it into hydrogen and oxygen, Peter Curreri of Houston, Texas based Lunar Resources, Inc. describes a concept for a pipeline to transport oxygen to where it is needed. Clearly oxygen will be a valuable resource to settlers for breathable air and oxidizer for rocket fuel if it can be sourced on the Moon. The company, whos objective is to develop and commercialize space manufacturing and resources extraction technologies to catalyze the space economy, believes that a lunar oxygen pipeline will “…revolutionize lunar surface operations for the Artemis program and reduce cost and risk!”.
Out at Mars, Congrui Jin from the University of Nebraska, Lincoln wants to augment inflatable habitats with building materials sourced in situ utilizing synthetic biology. Cyanobacteria and fungi will be used as building agents “…to produce abundant biominerals (calcium carbonate) and biopolymers, which will glue Martian regolith into consolidated building blocks. These self-growing building blocks can later be assembled into various structures, such as floors, walls, partitions, and furniture.” Building materials fabricated on site would significantly reduce costs by not having to transport them from Earth.
A couple of innovations are highlighted in this NIAC grant. First, Jin has studied the use of filamentous fungi as a producer of calcium carbonate instead of bacteria, finding that they are superior because they can precipitate large amounts of minerals quickly. Second, the process will be self-growing creating a synthetic lichen system that has the potential to be fully automated.
In addition to building habitats on Mars, Jin envisions duel use of the concept on Earth. In military logistics or post-disaster scenarios where construction is needed in remote, high-risk areas, the “… self-growing technology can be used to bond local waste materials to build shelters.” The process has the added benefit of sequestration of carbon, removing CO2 from the atmosphere helping to mitigate climate change as part of the process of producing biopolymers.
Graphical depiction of biomineralization-enabled self-growing building blocks for habitats on Mars. Credits: Congrui Jin
To reduce transit times to Mars a novel combination of Nuclear Thermal Propulsion (NTP) with Nuclear Electric Propulsion (NEP) is explored by Ryan Gosse of the University of Florida, Gainesville.
Conceptual illustration of a bimodal NTP/NEP rocket with a wave rotor enhancement. Credits: Ryan Gosse
NTP technology is relatively mature as developed under the NERVA program over 50 years ago and covered by SSP previously. NTP, typically used to heat hydrogen fuel as propellant, can deliver higher specific impulse then chemical rockets with attractive thrust levels. NEP can produce even higher specific impulse but has lower thrust. If the two propulsion types could be combined in a bimodal system, high thrust and specific impulse could improve efficiency and transit times. Gosse’s innovation couples the NTP with a wave rotor, a kind of nuclear supercharger that would use the reactor’s heat to compress the reaction mass further, boosting performance. When paired with NEP the efficiency is further enhanced resulting in travel times to Mars on the order of 45 days helping to mitigate the deleterious effects of radiation and microgravity on humans making the trip. This technology could make an attractive follow-on to the NTP rocket partnership just announced between NASA and DARPA.
Finally, an innovative propulsion technology for hurling heavy payloads rapidly to the outer solar system and even into interstellar space is proposed by Artur Davoyan at the University of California, Los Angeles. He will be developing a concept that accelerates a beam of microscopic hypervelocity pellets to 120 kilometers/s with a laser ablation system. The study will investigate a mission architecture that could propel 1 ton payloads to 500 AU in less than 20 years.
Artist depiction of pellet-beam propulsion for fast transit missions to the outer solar system and beyond. Credits: Artur Davoyan
Conceptual illustration of a lunar base in Mare Tranquilitatis Hole, believed to be an entrance to a lava tube about 100 meters below the lunar surface. Credits: Dipl.-Ing. Werner Grandl
In a new paper in Acta Astronautica Raymond P. Martin, a propulsion test engineer at Blue Origin and Haym Benaroya, a professor of mechanical and aerospace engineering at Rutgers describe the former’s research he carried out as a graduate student under the latter analyzing the structural integrity of lunar lava tubes after pressurization with breathable air. As reported previously on SSP, subterranean lava tubes on the Moon and Mars hold much promise as naturally occurring enclosures that are believed to be structurally sound, thermally stable and would provide natural protection from micrometeoroids as well as radiation. If they could be sealed off for habitation and filled with breathable air, life could be simplified for colonists as they would not have to don space suits for routine activities.
“This paper makes the argument that … lunar lava tubes present the most readily available route to long-term human habitation of the Moon”
Two views of a lunar skylight revealing a potential subsurface lava tube in Mare Ingenii. Credit: NASA/Goddard Space Flight Center/Arizona State University
Martin opens the paper with a history of the discovery and physical characteristics of lunar lava tubes tapping geological data dating back to the Apollo program. The existence of a lava tube is sometimes revealed by the presence of a “skylight”, a location where the roof of the tube has collapsed, leaving a hole that can be observed from space. Using an engineering simulation software called ANSYS, he developed a computer model to assess the structural integrity of these formations when subjected to internal atmospheric pressure.
Martin creates a model for his simulation based on the morphology of a relatively small lava tube known to exist from imagery taken by the Chandrayaan-1 spacecraft, the first lunar probe launched by the Indian Space Research Organisation . This structure averages 120 meters in diameter and was chosen because it has a rille-type opening level to the surface and could be sealed off at two locations. This approach makes sense as a starting point because the cavern would be easy to access and less energy would be be required to pressurize a smaller enclosure. Thus, the amount of infrastructure needed to establish early settlements would be minimized.
The goal of the simulation was to assess the integrity of the enclosed space under varying roof thicknesses and pressurization levels. Failure conditions were defined using commonly employed methods of assessing stability of tunnels in civil engineering and based on lunar basaltic rock general material properties known from testing of samples brought back from the Moon in the Apollo program and lunar meteorites. Finally, a formula was derived for safety factors associated with the failure conditions to ensure robustness of the design.
When running the simulation over various roof thicknesses and internal pressures, an optimum solution was found indicating that it is possible to pressurize a lava tube with a roof thickness of 10 meters with breathable air at nearly a fully atmosphere while maintaining its structural integrity. This would would feel like sea level conditions to people living there.
Being able to pressurize a lava tube for habitation could significantly simplify operations on the Moon as the infrastructure needed to make surface dwellings safe from radiation, micrometeorite bombardment and thermal extremes would be extensive adding costs to the settlement.
“A habitat within a pressurized tube would offer large reductions in weight, complexity, and shielding, as compared to surface habitats.”
Once a permanent settlement has been established and engineering knowledge advances to enable expansion into larger lava tubes, we can imagine how cities could be built within these spacious caverns, and what it would be like to live and work there. SSP explored just this scenario with Brian P. Dunn, who painted 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 envisions a thriving cislunar economy with factories producing spacecraft for Mars exploration.
Conceptual illustration of a spacecraft manufacturer inside a lava tube. Credit: Riley Dunn
Martin and Benaroya dedicated their paper to the memory of Brad Blair, a mining engineer who was a widely recognized authority on space resources.
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.
Conceptual illustration of Olympus, a lunar construction system based on in situ resource utilization. Credits: ICON
In a press release, the Austin based company reports how the Phase III award under NASA’s Small Business Innovation Research (SBIR) program will be used to adapt its existing additive manufacturing process for home building on Earth to the Olympus system using lunar regolith for fabrication of structures on the Moon. ICON envisions the system to be integrated into a rover that will be delivered to the Moon via a lander. The rover will then autonomously drive to a target site where the Olympus laser 3D printer will process lunar regolith into useful structures. The system can be used for fabricating roads, landing pads and habitats out of local resources without having to bring building materials from Earth, thereby significantly lowering costs. Once the system is proven on the Moon, perhaps in the later stages of Artemis, the same technology can be applied on Mars as well.
ICON plans to test the system “…via a lunar gravity simulation flight” although no details were revealed on such a mission. Presumably, this would be a parabolic flight in the Earth’s atmosphere. The company would use samples of lunar soil brought back during the Apollo missions and lunar regolith simulant to tune the process variables of their laser 3D printing equipment operating under these conditions. Once optimized, Olympus would be placed on the Moon “…to establish the critical infrastructure necessary for a sustainable lunar economy including, eventually, longer term lunar habitation.”
“The final deliverable of this contract will be humanity’s first construction on another world, and that is going to be a pretty special achievement.”
SSP has addressed the gravity prescription (GRx) in previous posts as being a key human factor affecting where long term space settlements will be established. It’s important to split the GRx into its different components that could effect adult human health, child development and reproduction. We know that microgravity (close to weightlessness) like that experienced on the ISS has detrimental effects on adult human physiology such as osteoporosis from calcium loss, degradation of heart and muscle mass, vision changes due to variable intraocular pressures, immune system anomalies…the list goes on. But many of these issues may be mitigated by exposure to some level of gravity (i.e. the GRx) like what would be experienced on the Moon or Mars. Colonists may also have “health treatments” by brief exposures to doses of 1G in centrifuge facilities built into the settlements if the gravity levels in either location is found to be insufficient. We currently have no data on how human physiology would be impacted in low gravity (other then microgravity).
The most important aspect of the GRx with respect to space settlement relates to reproduction. How would lower gravity effect embryos during gestation? Since humans have evolved in 1G for millions of years, a drastic change in gravity levels during pregnancy could have serious deleterious effects on fetal development. Since fetuses are already suspended in fluid and can be in any orientation during most of their development, it may be that they don’t need anywhere near the number of hours of upright, full gravity that adults need. How lower gravity would affect bone and muscle growth in young children is another unknown. We just don’t know what would happen without a clinical investigation which should obviously be done first on lower mammals such as rodents. Then there are ethical questions that may arise when studying reproduction and growth in higher animal models that could be predictive of human physiology, not to mention what would happen during an accidental human pregnancy under these conditions.
Right now, we only know that 1G works. If space settlements on the Moon or Mars are to be permanent and sustainable, many space settlement advocates believe they need to be biologically self-sustaining. Obviously, most people are going to want to have children where they establish permanent homes. If the gravity of the Moon or Mars prevents healthy pregnancy, long term settlements may not be possible for people who want to raise families. This does not rule out permanent settlements without children (e.g. retirement communities). They just would not be biologically self-sustaining.
SSP has suggested that it might make sense to determine the GRx soon so that if we do determine that 1G is required for having children in space, we begin to shape our strategy for space settlement around free space settlements that produce artificial gravity equivalent to Earth’s. Fortunately, as Joe Carroll has mentioned in recent presentations, the force of gravity on bodies where humanity could establish settlements throughout the solar system seems to be “quantized” to two levels below 1G – about equal to that of the Moon or Mars. All the places where settlements could be built on the surfaces of planets or on the larger moons of the outer planets have gravity roughly at these two levels. So, if we determine that the GRx for these two locations is safe for human health, we will know that we can safely raise families beyond Earth in colonies on the surfaces of any of these worlds. Carroll proposes a Moon/Mars dumbbell gravity research facility be established soon in LEO to nail down the GRx.
But is there an argument to be made for skipping the step of determining the GRx and going straight to an O’Neill colony? After all, we know that 1G works just fine. Tom Marotta thinks so. He discussed the GRx with me on The Space Show recently. Marotta, with Al Globus coauthored The High Frontier: An Easier Way. The easier way is to start small in low Earth orbit. O’Neill colonies as originally conceived by Gerard K. O’Neill in The High Frontier would be kilometers long in high orbit (outside the Earth’s protective magnetic field) and weigh millions of tons because of the amount of shielding required to protect occupants from radiation. The sheer enormity of scale makes them extremely expensive and would likely bankrupt most governments, let alone be a challenge for private financing. Marotta and Globus suggest a step-by-step approach starting with a far smaller version of O’Neill’s concept called Kalpana. This rotating space city would be a cylinder roughly 100 meters in diameter and the same in length, spinning at 4 rpm to create 1G of artificial gravity and situated in equatorial low Earth orbit (ELEO) which is protected from radiation by our planet’s magnetic field. If located here the settlement does not require enormous amounts of shielding and would weigh (and therefore cost) far less. Kasper Kubica has proposed using this design for hosting $10M condominiums in space and suggests an ambitious plan for building it with 10 years. Although the move-in cost sounds expensive for the average person, recall that the airline industry started out catering to the ultra-rich to create the initial market which eventually became generally affordable once increasing reliability and economies of scale drove down manufacturing costs.
What about all the orbital debris we’re hearing about in LEO? Wouldn’t this pose a threat of collision with a free space settlement given their larger cross-sections? In an email Marotta responds:
“No, absolutely not, I don’t think orbital debris is a showstopper for Kalpana.
… First, the entire orbital debris problem is very fixable. I’m not concerned about it at all as it won’t take much to clean it up: implement a tax or a carbon-credit style bounty system and in a few years it will be fixed. Another potential historical analogy is the hole in the ozone layer: once the world agreed to limit CFCs the hole started healing itself. Orbital debris is a regulatory and political leadership problem, not a hard technical problem.
Second, even if orbital debris persists, the technology required to build Kalpana…will help protect it. Namely: insurance products to pay companies (e.g. Astroscale, D-Orbit, others) to ‘clear out’ the orbit K-1 will inhabit and/or mobile construction satellites necessary to move pieces of the hull into place can also be used to move large pieces of debris out of the way. In fact, I think having something like Kalpana…in orbit – or even plans for something that large – will actually accelerate the resolution of the orbital debris problem. History has shown that the only time the U.S. government takes orbital debris seriously is when a piece of debris might hit a crewed platform like the ISS. Having more crewed platforms + orbital debris will drastically limit launch opportunities via the launch collision avoidance process. If new satellites can’t be launched efficiently because of a proliferation of crewed stations and orbital debris I suspect the very well-funded and strategically important satellite industry will create a solution very quickly.”
To build a space settlement like the first Kalpana, about 17,000 tons of material will have to be lifted from Earth. Using the current SpaceX Starship payload specifications this would take 170 launches to LEO. By comparison, in 2021 the global launch industry set a record of 134 launches. Starship has not even made it to orbit yet, but assuming it eventually will and the reliability and reusability is demonstrated such that a fleet of them could support a high launch rate, within the next 20 years or so there will be considerable growth in the global launch industry. If larger versions of Kalpana are built the launch rate could approach 10,000 per year for space settlement alone, not to mention that needed for rest of the space industry. This raises the question of where will all these launches take place? Are there enough spaceports in the world to support it? Marotta has an answer for this as well. As CEO of The Spaceport Company, he is laying the groundwork for the global space launch infrastructure that will be needed to support a robust launch industry. His company is building distributed launch infrastructure on mobile offshore platforms. Visit his company website at the link above for more information.
Conceptual illustration of a mobile offshore launch platform. Credits: The Spaceport Company
For quite some time there has been a spirited debate among space settlement advocates on what destination makes the most sense to establish the first outpost and eventual permanent homes beyond Earth. The Moon, Mars or free space O’Neill settlements. Each location has its pros and cons. The Moon being close and having ice deposits in permanently shadowed craters at its poles along with resource rich regolith seems a logical place to start. Mars, although considerably further away has a thin atmosphere and richer resources for in situ utilization. Some believe we should pursue all the above. However, only O’Neill colonies offer 1G of artificial gravity 24/7. With so many unknowns about the gravity prescription for human health and reproduction, free space settlements like Kalpana offer a safe solution if the markets and funding can be found to make them a reality.
