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 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.
Eventually we will get to the stars. It may not happen in our lifetime but its going to happen some day. Adam Crowl has provided a nice historical review of the interstellar pioneers from the last century that worked out the physics of the starships that will take us there. He does this in a chapter he wrote for James and Gregory Benford’s ground-breaking anthology Starship Century which was based on the findings of the 100‐Year Starship Symposium seeded by a DARPA solicitation and executed by NASA back in 2011.
Crowl begins the story with the early days of rocketry pioneered by Tsiolkovsky determining the rocket equation and Goddard and others experimenting with liquid fueled rockets. Tsiolkovsky was the first to come up with the idea of a generation starship (sometimes referred to as a worldship) when he realized that existing chemical propellants would be insufficient to fuel a space ship for interstellar travel.
Artist depiction of an interstellar worldship. Credits: Michel Lamontagne / Principium, Issue 32, February 2021
More practical interstellar craft don’t come on the scene until after WWII when advanced propulsion concepts really take off. The possibility of harnessing light to “push” a rocket, feasible because photons carry momentum, first appeared in science fiction. As it turned out, physicists realized that to generate the needed thrust with light pressure would require enormous amounts of energy, the waste heat of which would vaporized the vessel. Nevertheless, the photon rocket was still being discussed as late as 1972 when I first saw the rendering at the top of this post by David Hardy in the book he coauthored with Patrick Moore called Challenge of the Stars. Fast forward to today, Dr. Young K. Bae’s Photonic Laser Thruster shows great promise if it can be scaled up for interstellar travel.
Diagram depicting the layout of the Photonic Laser Thruster. Credits: Young K. Bae, Ph.D.
In the latter half of the last century, as the physics of nuclear energy and laser technology progressed, we see a proliferation of many concepts for star travel, including various forms of fusion rockets, laser sails, antimatter propulsion and my personal favorite, the Bussard ramjet. Conceived by the physicist Robert Bussard in 1960, the ship eliminates the need to carry fuel by collecting hydrogen from the interstellar medium using a magnetic field as a ram scoop and compresses the gas to fusion temperatures to create thrust. Crowl summarizes some of the physical limitations of the original concept and discusses several physicist’s alternative designs to address them.
One concept that didn’t make it into Crowl’s piece was developed recently by Leif Holmlid and Sindre Zeiner-Gundersen. Called the laser induced annihilation drive, it uses a pulsed laser to initiate “antimatter-like” annihilation reactions in hydrogen fuel producing high velocity K meson elementary particles at relativistic speeds to generate thrust.
Diagram of a laser-induced annihilation generator for space propulsion. Credit: Leif Holmlid and Sindre Zeiner-Gundersen, Acta Astronautica 23 May 2020
When I asked Crowl if he had any updates to some of the starship propulsion concepts he sent me an article penned by an unknown author for Medium that came up with another alternative to address the limitations of the original Bussard Ramjet. The author, who goes by the pseudonym “deepfuturetech”, reminds us like Crowl discussed in his piece, that the cross section ( i.e. the probability that a given atomic nucleus or subatomic particle will undergo a nuclear reaction in relation to the species of the incident particle) of the Bussard ramjet proton-proton fusion reaction is too low to be useful. Deepfuturetech proposes a different fusion mechanism via (p,n) reactions which involve a nucleus capturing a proton and subsequently emitting a neutron. These type of reactions have higher cross sections and could be tested in reactors in the near future. Further analysis is needed to confirm whether these reactions could produce neutrons at sufficiently low energy cost to enable profitable hydrogen fusion.
Artist depiction of a Bussard ramjet. Credits: NASA
Incidentally, Crowl talked about many of these starship concepts at a subsequent Starship Century Symposium held in 2013 by the Arthur C. Clarke Center for Human Imagination in collaboration with the Benford brothers who shared the highlights from their Starship Century anthology summarizing scientific results from the 100‐Year Starship project. You can also get a “Deeper Future View” of his independent research on interesting items not typically covered by the mainstream science media at his blog Crowlspace.
Hubble Space Telescope image of Mars showing clouds in atmosphere near the poles and the extinct volcano Olympus Mons at right. The primary constituents of the Martian air are carbon dioxide (95%) and nitrogen (~3%). Credits: NASA
A new technology funded by ESA is under development in Belgium and Portugal that could produce breathable air, oxidizer for rocket fuel and nitrogen for fertilizer out of thin air on Mars. Using a high energy plasma, researchers at the University of Antwerp and the University of Lisbon published independent results that look promising as a source of oxygen for life support and propulsion, plus nitrogen oxides as fertilizer to grow crops.
Team Antwerp heated simulated Martian atmosphere with microwaves in a plasma chamber. The electrical energy cracked the carbon dioxide and nitrogen in the gas into highly reactive species generating oxygen which, in addition to creating breathable air and oxidizer for fuel, was combined with the nitrogen to create useful fertilizer.
The scientists in Lisbon used direct current to excite the gases into a plasma state, literally creating lightning in a bottle. This team focused only on the production of oxygen.
The efficiency of these processes is quite impressive. For example, when compared to the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) on NASA’s Perseverance rover, the Antwerp system uses the same input power, about 1kWh, but produces 47 g per hour which is about 30 times faster. MOXIE uses solar energy to electrochemically split carbon dioxide into oxygen ions and carbon monoxide, then isolates and recombines the oxygen ions into breathable air.
Image of the toaster-sized Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) being installed on the Perseverance rover at the Jet Propulsion Laboratory prior to launch. Credit: NASA/JPL-Caltech
The research is in early days but has the potential for benefits on Earth too. The amount of energy needed to fix nitrogen in fertilizer for terrestrial crops is significant and releases considerable amounts of carbon dioxide to support worldwide agriculture. This plasma technology, if it can be commercialized, has the potential to reduce the carbon footprint of Earth-based fertilizer production. The fact that the process has duel-use provides a profit motive for development of the equipment and scaling up production, which could lead to improvements in efficiency and reduction in the mass for space applications.
We love ISRU technology that facilitates production of consumables using local resources at space destinations, thereby reducing the mass that needs to be transported to support space settlements and enabling them to become self-sustaining.
Roadmap for research and infrastructure development for growing crops in space for human sustenance and life support, from the ISS to Mars. Credits: Grace L. Douglas, Raymond M. Wheeler and Ralph F. Fritsche
Space settlement advocates know that we will have to take our biosphere with us to space to produce food, provide breathable air and recycle wastes. Completely closing the system, i.e. recycling everything is a huge technological challenge, especially on a small scale like what is planned for settlements in free space or on the surfaces of the Moon or Mars. Fortunately, there are plenty of raw materials in the solar system for in situ resource utilization so we can live off the land, so to speak, until our bioregenerative life support system efficiencies improve.
Early research into crop production in space has been performed on the ISS. But the road ahead for space agriculture in the context of life support systems needs careful planning to pave the way toward biologically self-sustaining space settlements. A team of scientists at NASA is working on a roadmap toward sustainability with a step-by-step approach to bioregenerative life support systems (BLSS) that will provide food and oxygen for astronauts during the space agency’s mission plans in the decades ahead. In a paper in the journal Sustainability they identify the current state of the art, resource limitations and where gaps remain in the technology while drawing parallels between ecosystems in space and on Earth, with benefits for both.
Simulation and modeling of BLSS concepts is important to predict their behavior and help inform actual hardware designs. A team at the University of Arizona performed a study recently analyzing the inputs and outputs of such a system to improve efficiencies and apply it to food production on Earth in areas challenged by resource limitations and food insecurity. Sustainable ecosystems for supporting humans on and off Earth have similar goals: minimizing growing space, water usage, energy needs and waste production while simultaneously maximizing crop yields. The team presented their findings in a paper presented at the 50th International Conference on Environmental Systems held last July. In the study, a model of an ecosystem was created consisting of various combinations of plants, mushrooms, insects, and fish to support a population of 8 people for 183 days with an analysis of total growing area, water requirements, energy consumption and total wastes produced. The study concluded that “In terms of resource consumption, the strategy of growing plants, mushrooms, and insects is the most resource-efficient approach.”
At the same conference, an update was provided on a Scalable, Interactive Model of an Off-World Community (SIMOC). SIMOC was described in a previous post on the Space Analog for the Moon and Mars (SAM) located at Biosphere 2 in Arizona. SIMOC is a platform for education meeting standards for student science curriculum. Pupils or citizen scientists can customize human habitats on Mars by selection of mission duration, crew size, food provisions as well as choosing types of plants, levels of energy production, etc.. Users gain an understanding of the complexity of a BLSS and the tradeoffs between mechanical and biological variables of life support for long duration space missions. There is much to be learned on the limitations and stability of closed biospheres, as discussed last year.
Image of Biosphere 2, a research facility to support the development of computer models that simulate the biological, physical and chemical processes to predict ecosystem stability. Credits: Biosphere 2 / University of Arizona
A BLSS based on plant biology could be augmented with dark ecosystems, the food chain based on bacteria that are chemotrophic, i.e. deriving their energy from chemical reactions rather then photosynthesis, which could significantly reduce the inputs of energy and water.
A concept for a lunar farm called Lunar Agriculture, Farming for the Future was published in 2020 by an international team of 27 students participating in the Southern Hemisphere Space Studies Program at the International Space University.
Layout of a potential subsurface lunar farm. Credits: International Space University and University of South Australia
As a treat to cap off this post, a retired software engineer and farmer named Marshall Martin living in Oklahoma provided his perspective on crops in space on The Space Show recently. A frequent caller to the program, this was his first appearance as a guest where, like the NASA team mentioned earlier, he recommends a phased approach to space farming starting with small orbital facilities, testing inputs and outputs as we go, to ensure the economics pay off at each stage of our migration off Earth. He even envisions chickens and goats as sources of protein and milk, although the weight limitations for inclusion of these animals in space-based ecosystems may not be possible for quite some time. Its unlikely that cows will ever make it to space but cultured meat production is a real possibility for the carnivores among us which is being studied by ESA.
Cattle in the cargo bay of the Firefly-class transport spaceship Serenity. Cows probably won’t make it to space because of weight, volume and resource limitations but cultured meat is a real possibility. Image from the television series Firefly. Credits: Josh Whedon/ Mutant Enemy, Inc. in associations with Twentieth Century Fox Television
Conceptual overview of the lunar Rosas Base derived from a SpaceX Starship tipped on its side and covered with regolith. Credits: International Space University, Space Studies Program 2021 Team*. The name of the base is in memory of Oscar Federico Rosas Castillo
During Elon Musk’s recent Starship update from Boco Chica, Texas he said that he was “highly confident” that Starship would reach orbit this year. He also predicted that the cost of placing 150 tons in LEO could eventually come down to as low as $10 million per launch, and that “…there are a lot of additional customers that will want to use Starship. I don’t want to steel their thunder. They’re going to want to make their own announcements. This will get a lot of use, a lot of attention….”
“Once we make this work, its an utterly profound breakthrough in access to orbit….the use cases will be hard to imagine.” – Elon Musk
One such potential use case was worked out in detail by a team* of students last year during the International Space University’s (ISU) Space Studies Program 2021 held in Strasbourg, France. Called Solutions for Construction of a Lunar Base, the project used the version of Starship currently under development by SpaceX for the Human Landing System component of NASA’s Artemis Program as the basis for a habitat on the Moon. The concept was also described in a paper at the 72nd International Astronautical Congress in Dubai last October. The mission of the project was:
“To develop a roadmap for the construction of a sustainable, habitable, and permanent lunar base. This will address regulatory and policy frameworks, confront technological and anthropological challenges and empower scientific and commercial lunar activities for the common interest of all humankind.”
The team did an impressive job working out solutions to some of the most challenging issues facing humans living in the harsh lunar environment like radiation, micrometeorites, and hazardous lunar dust. They also dealt with human factors, physiological and medical problems anticipated under these conditions. Finally, the legal aspects as well as a rigorous financial analysis was conducted to support a business plan for the base in the context of a sustainable cislunar economy. The report is lengthy and challenging to summarize but here are some of the highlights.
A decommissioned Starship forms the primary core component of the outpost having its fuel tanks converted to living space of considerable volume. This has precedent in the U.S. space program when NASA modified an S-IVB stage of a Saturn V to create Skylab. The team envisions extensive use of a MOdular RObotic Construction Autonomous System (MOROCAS) outfitted with specific tools to perform a variety of activities autonomously which would reduce the need for extravehicular activities (EVA) thereby minimizing risks to crew. The MOROCAS would be utilized to tip the Starship on its side, pile regolith over the station for radiation protection and a range of other useful functions.
Medical emergencies were considered for accidents anticipated for construction activities in the high risk lunar environment. The types of injuries that could be expected were assessed to inform plans for needed medical equipment and facilities for diagnosis and treatment.
As discussed by SSP in a previous post, hazards from lunar regolith must be mitigated in for any activities on the moon. The solutions proposed included limiting dust inhalation through monitoring and smart scheduling EVAs, the use of dust management systems utilizing electrostatic removal mechanisms and intelligent design of equipment. In addition, landing sites and travel routes would be prepared either through sintering of regolith or compaction to prevent damage to structures by rocket plumes.
Funding of the Rosas Base was envisioned to be implemented via a public/private partnership administered by an international authority called the Rosas Lunar Authority (RLA). The RLA management would be structured as an efficient interface between participating governments while being capable of responding to policy and legal challenges. It would rely on public financing initially but eventually shift to private financing supplemented by rental of the base to stakeholders and interested parties.
Finally the team examined the value proposition driving establishment of the base. Sociocultural benefits, scientific advancements and technology transfer would be the primary driving factors. Initial market opportunities would be targeted at the scientific community in the form of data and lunar samples. Follow-on commercial activities that would attract investors could include launch services to orbit, cislunar spacecraft services, propellent markets in lunar orbit and LEO, communications networks in cislunar space and commercial activities on the surface such as supplies of transportation and mining equipment, habitats, and ISRU facilities.
The surface of the Moon provides exciting opportunities for scientific experimentation, medical research, and commerce in the cislunar economy about to unfold in the next decade. The unique capabilities of Starship and the solutions proposed in this report support a sustainable business model for a permanent outpost like the Rosa Base on the Moon.
Conceptual illustration of an emerging cisluar economy. Credits: International Space University, Space Studies Program 2021 Team*
SSP featured a post in 2020 on the promise of lava tubes as ideal natural structures on the Moon or Mars in which space settlements could be established. Some are quite voluminous and could contain very large cities. Lava tubes provide excellent protection from radiation, micrometeorite bombardment and temperature extremes while being very ancient and geologically stable.
How would a city be established inside a lava tube? What would it be like to live and work there? Brian P. Dunn paints a scientifically accurate picture of such a future in Tube Town – Frontier, a hard science fiction book visualizing life beneath the surface of the Moon. Dunn recently appeared on The Space Show where he provided tantalizing details on his book scheduled to be published later this year. You can also get a taste of the story through excerpts available on his website.
I’ve had the opportunity to get an advanced copy of his book and will be providing feedback to Dunn prior to publication. He agreed to an interview via email, summarized below, answering some of my initial questions:
SSP: Your first chapter of the book takes place in 2028 and starts out with teleoperated “SciBots” networked together in swarms to explore and prospect for resources at the Moon’s south pole. They are battery powered and need to periodically recharge at stations at the base of solar power towers at the Peaks of Eternal Light, similar to what Trans Astronautical Corp. is planning with their Sunflower system. This time frame seems overly optimistic given that NASA’s Artemis program won’t return astronauts to the Moon until the mid 2020s and Jeff Foust reported recently that a second landing won’t take place until 2 years later. Would it be more realistic to move out the timeline 5-10 years?
BPD: As Kathy Lueders at NASA has said, our strategy with both Moon and Mars is ‘Bots then Boots’. There is much scientific and ISRU work that can be done before the humans arrive. (See the article on my blog “The Mother of All CLPS Missions.”) With the Moon’s close proximity and communications satellites, we can teleoperate rovers much easier than on Mars. Regarding the SLS/Artemis timeline, I don’t believe it will ever reach full fruition. The Artemis/Gateway architecture is too expensive and too slow. There is a paradigm shift happening now as the concept of large, re-usable, re-fuel able, high payload, quick launch cadence rockets is being proven out with SpaceX’s Starship.
SSP: After discovery of the lava tube in which Tube Town is eventually established, the public “was clamoring for more” and the “excitement of the discovery of the tube breathed new life into lunar and space exploration”. I know that I would be excited, and most space cadets would be as well, but why would the general public be so supportive of space exploration because of the discovery of a lava tube on the Moon? A recent poll found that a majority of people think that sending astronauts to the moon or Mars should be either low or not a priority.
BPD: Now that we’re starting to get the rockets, the American public will soon see landers and rovers return to the Moon. This time it will be in HD TV. At some point Americans will return to the Moon. This will be must-see TV. Taikonauts will eventually land on the Moon. This will definitely light a fire under the Americans. Interest in the Moon and lunar exploration will go up. The problem will be sustaining interest (We have an incredibly short attention span). After the world record TV event, interest will wane. We will only be able to put a few astronauts in small habitats on the surface for short periods of time. Upon discovery of an intact lava tube people will know that we could actually build a town on the Moon. Even better than that guy described in that book… what was it called?
SSP: Tube Town is operated by an umbrella organization of national space programs led by NASA called the International Space Program. How do you envision this cost sharing structure getting started?
BPD: Although much cheaper than a comparable sized surface base, outfitting a lava tube for human habitation will not be cheap. Much of the materials can be made in situ, such as aluminum sheeting for the floors and airlocks, waterless concrete, steel for pressure vessels to hold volatile gasses, but much will need to come from Earth such as Factory machines, computers, electronics, medical equipment, etc.
In Tube Town, this cost is spread among the space programs of 27 countries of the International Space Program (NASA, ESA plus 9 countries that signed the Artemis Accords).
US, Canada, Australia, New Zealand, Japan, South Korea, India, Brazil, Israel, United Arab Emirates, and the 17 member countries of the European Space Agency (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain Sweden, Switzerland and the United Kingdom). Notable holdouts were China (CNSA) and Russia (Roscosmos).
The ISP is a cost and opportunity sharing umbrella organization for building and maintaining a large Moon base and robotic creation of a Mars base and the first crewed mission to Mars.
NASA would be the lead partner of the ISP, but project decisions were approved and administered by the ISP Board of Directors consisting of the member countries of the organization with weighted voting rights proportionate to their contribution. Many countries wanted to get in on the ground floor of a new space economy but couldn’t afford to duplicate the resources and infrastructure that already existed at NASA. With their combined buying power, the ISP could source rockets, landers, robotics, space suits, etc. from the most efficient and innovative private suppliers. In return, ISP countries received habitation services (shelter, atmosphere, food, water) and discounted rates for:
leasing habitation space in the Tube for scientific or commercial enterprise,
buying propellant and other in situ resources, and
payload return to Earth
ISP construction costs of the Tube are initially off-set by lunar tourism and bespoke mining. Tourism licenses are issued by the ISP to private companies. The contracts include revenue sharing, ISP Code of Conduct compliance and Space Heritage sites preservation requirements. In exchange, the licensees get transportation, medical emergency and habitation services on the Moon.
In Tube Town, the first ISP tourism licensee is with Lunar Experience, LLC. LE licensed 50 seats for a seven Earth day stay. They ran two tours per Earth month to take advantage of the Nearside lunar day (in early days, most of the popular attractions were on the Nearside). LE agreed to give away 25% of the seats to people who could not afford the price. So, of the 50 seats per trip, 12 were free and 38 were paying customers. Assuming a ticket price of $5m for a trip to the Moon for a week, a flight made $190m. The revenue sharing agreement with the ISP was 60/40 (LE 60%, ISP 40%) so for that $190m flight, LE earned $114m and ISP $76m. If only two trips were completed per month, the yearly income would be LE $1.3B and ISP $912m. The ticket price would double to watch the uncrewed launches to Mars and the price would triple to be a part of history to witness the crewed launch to Mars.
In addition, the ISP or commercial customers could take advantage of very reasonable freight rates to backhaul refined payload on the returning tourist rockets to Earth. When would the price become affordable for regular people? Probably after the third tube is discovered. I could see an ISP member like UAE opening a large lava tube exclusively as a vacation resort.
SSP: The main product produced by Tube Town’s factory is spacecraft for Mars exploration and the eventual establishment of an outpost on the Red Planet. Presumably, at least at first, not all electronic components can be made on the Moon so will have to be imported from Earth via a space-based supply chain. Elon Musk is designing Starship to go directly to Mars from Earth. Why does building spacecraft on the Moon for a Mars mission make economic sense when compared to “going direct” like Starship, and why isn’t Starship mentioned in the book?
BPD: The book is a work of fiction so I try not to use real names or products. Although I think Starship is the first of its class of big, reusable rockets, I also think the concept will be replicated (like airliners) and hopefully there will be several options in the Earth to Moon supply chain. If you can make a big re-usable rocket on a beach in Texas, you can make one inside a nice lava tube on the Moon. We will also need to get lots of bots and machinery to Mars before the humans. This can also be manufactured on the Moon. When you launch, you don’t have to fight the giant gravity well of Earth (12.6 km/s vs 2.6 km/s) and you may not even have to re-fuel to head for Mars. Huge payloads will be much more economical from the Moon.
Artist conception of a spacecraft manufacturer inside a lava tube. Credit: Riley Dunn
SSP: Tube Town has a Farm devoted to food production, waste re-cycling, and ice processing. However, without insects or wind pollination it is not possible to grow desirable fruits and vegetables like apples, squash, melons and many more. You devised an innovative way to pollinate the plants. Tell us about that!
BPD: Nearly all of the technology described in the book is based on existing technology, whether in the lab or in production. Harvey’s pollinating space bees are based on a combination of miniature drone-delivered soap bubble pollination and AI image recognition software.
SSP: In your book, the Apollo 11 landing site becomes a tourist destination. What steps are taken to preserve this fragile heritage site?
BPD: I think the Apollo 11 site is the must-see tourist attraction on the Moon. Part of that attraction is that you can still see the boot prints of the astronauts in the regolith. On the moon, boot prints are forever- unless another human destroys them. It only takes one knucklehead.
In my book, a regolith wall is built around the site to protect from plume drift from vehicles. The entrance is a good distance away from the site. Access into the site is in a plexiglass pod that is suspended above the surface. A cable system mounted on tall towers maneuvers pods of tourists through the site from above, giving them a close-up encounter, yet not disturbing the artifacts nor the regolith.
There should be multiple Space Heritage Sites on the Moon consisting of artificial artifacts from multiple countries and natural wonders like Schroter’s Valley. They should be identified and preserved by the tourist licensees that will profit from them.
Vallis Schröteri (Schroter’s Valley), believed to be volcanic in origin, is the largest sinuous rille on the Moon seen here as imaged by Apollo 15. Credits: NASA via Wikipedia
SSP: Tube Town has a centrifuge in the Rec Section to provide artificial gravity for residents to maintain their physical health, but very little detail is provided. How often do residents use this facility, on average, and is it’s radius optimized to minimize Coriolis forces? You might consider this well thought out design for a centrifuge.
BPD: I love this design for a lunar lava tube environment! The Rec section of Tube Town is over 400m wide so this is the perfect place for a floor mounted Dorais Gravity Train. In my book, this would be used for scientific study of the effects of artificial gravity treatment in a low gravity environment. They would do studies on both animals, plants and humans. I see crewmembers and tourists using the gravity train as a health spa and treatment against ‘gravity sickness’.
SSP: There are a couple of resident dogs in Tube Town and one them actually becomes pregnant. This has huge implications for biomedical research on mammalian reproduction in lunar gravity and in particular, determination of the gravity prescription for healthy human gestation. In my opinion, determination of the gravity prescription is one of the most significant questions to be answered for long term space settlement. Tell us about how this research is carried out in Tube Town in an ethical manner?
BPD: The studies would start with mice. Only when and if the studies show that mammalian reproduction in low gravity is safe, would the crew move up to higher level mammals. If safe, the female dog would be taken off the canine birth control medication she is on. BTW, all the ISP crewmembers and commercial residents must agree to be on birth control medication while living on the Moon. Many may choose to freeze eggs or sperm on Earth before a long deployment in space.
SSP: Where on the Moon should we look for lava tubes?
BPD: Nearly all of the volcanic activity of the Moon was on the Nearside, not the Farside. So we should definitely concentrate on the Nearside. We can see lots of collapsed lava tubes on the surface of the Moon, the intact ones are probably in the same regions.
My suggestion is to look for them where we would like to find them, in other words, lets look in strategic lunar base locations where there is water and power and easy access to other useful minerals (like metals).
I’m sure NASA knows better than me, but my target priorities would be:
North Pole – because its near water and solar power and metals (the Northern Oceanus Procellarum and the highlands between the maria).
South Pole – because its near water and solar power. The South Pole-Aitken basin is a large impact crater but apparently there was some later volcanic activity so it is possible to find tubes in the South Pole area but they may be smaller in size and length than the ones in the Maria.
Marius Hills (southwest of Schroter’s Valley in Oceanus Procellarum) – because there is lots of volcanic activity and collapsed tubes and it is near minerals and metals.
SSP: Thanks Brian for your exciting vision of our future on the Moon and for the opportunity to get a sneak peek. I’m enjoying the story of Tube Town and wish you much success with the release of the book.
Artist rendering of an earlier version of Starship (formerly BFR, Interplanetary Transport System) approaching Mars. Credits: SpaceX
A mission architecture for Starship is described in a preprint open access article published online December 2 to be released in the next issue of the New Space Journal. The paper lays out a proposed strategy for using the yet to be validated SpaceX reusable spacecraft to establish a self sustaining colony on Mars. The authors* are a mix of space practitioners from NASA, the space industry and academia. No doubt Elon Musk may be thinking along these lines as he lays his company’s plans to assist the human race in becoming a multi-planet species.
Starship is a game changer. It is being designed from the start to deposit massive payloads on The Red Planet. It will be capable of delivering 100 metric tons of equipment and/or crew to the Martian surface, and after refueling from locally sourced resources, returning to Earth. This capability will not only enable extensive operations on Mars, it will open up the inner solar system to affordable and sustainable colonization.
Some of the assumptions posited for the mission architecture are based on Musk’s own vision for his company’s flagship space vehicle as articulated in the New Space Journal back in 2017, namely that two uncrewed Starships would initially be sent to the surface of Mars with equipment to prepare for a sustainable human presence.
“These first uncrewed Starships should remain on the surface of Mars indefinitely and serve as infrastructure for building up the human base.”
The initial landing sites will be selected based on where the water is. The priority will be finding and characterizing ice deposits so that humans will eventually be able to locally source water for life support and to produce fuel for the trip home. The automated payloads of these initial missions will be mobile platforms similar in design to equipment planned for upcoming robotic missions to the Moon in the next couple of years. One such spacecraft, the Volatiles Investigating Polar Exploration Rover (VIPER) is discussed with its suite of instruments that will be used to assess the composition, distribution, and depth of subsurface ice to inform follow-on ISRU operations.
“The use of water ice for ISRU has been determined as a critical feature of sustainability for a long-term human presence on Mars.”
Conceptual depiction of the NASA VIPER rover planned for delivery to the Moon’s south pole in late 2023. A mobile platform with a similar suite of instruments based on this design could be launched to Mars aboard Starship. Credits: NASA
To harvest water from subsurface ice the authors suggest using proven technology such as a Rodriguez Well (Rodwell). In use since 1995, a Rodwell has been providing drinking water for the U.S. research station in Antarctica. The U.S. Army Engineer Research and Development Center’s (ERDC) Cold Region Research and Engineering Laboratory (CRREL) has been working with NASA to prove the technology for use in space in advance of a human outpost on Mars.
Diagram depicting how a Rodriquez Well works. Credits: U.S. Army Engineer Research and Development Center
“Rodwell systems are robust and still in routine use in polar regions on Earth.”
The next order of business is power generation. The authors suggest using solar power as a first choice because the technology readiness level is the most mature at this time. Autonomous deployment of a photovoltaic solar array would be carried out on the initial uncrewed missions. But due to frequent dust storms that could diminish the array reliability, nuclear power may be a more appropriate long term solution once space based nuclear power is proven. NASA’s Glenn Research center is working on Fission Surface Power with plans for a lunar Technology Demonstration Mission in the near future. A solid core nuclear reactor is also an option as the technology is well understood.
These initial missions will robotically assess the Martian environment at the landing sites to inform designs of subsequent equipment to be delivered by crewed Starship missions in future launch windows occurring every 26 months. Weather monitoring will be performed as well as measurements of radiation levels and geomorphology to inform designs of habitats and trafficability. Remotely controlled experiments on hydroponics will also be performed to understand how to produce food. Testing will be needed on excavation, drilling, and construction methods to provide data on how infrastructure for a permanent colony will be robustly designed.
Starship’s ample payload capacity will allow prepositioning of supplies of food and water to support human missions before self sustaining ISRU and agriculture can be established. Communication equipment will be deployed and landing sites prepared for the arrival of people. Much of these activities will be tested on the Moon ahead of a Mars mission.
Production of methane and oxygen in situ on Mars will enable refueling of Starship for the trip home, as envisioned in 1990 by Robert Zubrin and David Baker with their Mars Direct mission architecture. Zubrin’s Pioneer Astronautics may even play a role through provision of equipment for ISRU as they are already working on hardware that could be tested on the Moon soon. One could envision a partnership between Zubrin and Musk as their organizations have common visions, and Zubrin has written about the transformative potential of Starship. When people arrive on Starship during a subsequent launch window after the placement of uncrewed vehicles, further testing of ISRU and life support equipment will be performed with humans in the loop to validate these technologies that will enable Mars settlements to sustain themselves.
If Musk is successful in establishing a permanent self-sustaining colony on Mars will it be a true settlement? The National Space Society in their definition says that a space settlement “..includes where families live on a permanent basis, and…with the goal of becoming…biologically self-sustaining…”, i.e. capable of human reproduction. The definition is agnostic as to if the settlement is in space or on a planetary surface. Musk wants to established cities on the planet housing millions of people by mid century. But does this make sense if settlers can’t have healthy children in the lower gravity of Mars? SSP explored this question in a recent post. Hopefully, once Starship becomes operational, an artificial gravity research facility in LEO will be high on Musk’s priority list to answer this question before he gets too far down the Martian urban planning roadmap. Would he ever consider a change in space settlement strategy in favor of O’Neill type free space colonies? Starship could certainly help facilitate the realization of that vision.
If all goes according to plan, SpaceX will attempt the first orbital flight of a Starship prototype sometime next year, which also happens to be when the next launch window opens up for trips to Mars. Obviously, nothing in rocket development goes according to plan, so the initial flight ready design is at least a year away optimistically. And we know Musk’s timelines are notoriously aspirational. As ambitious as Musk is in driving his company toward the goal of colonizing Mars, it seems unlikely that an initial uncrewed mission with all its flight ready automated hardware as described above could be ready by the next launch window in 2024. But what about 2026? NASA’s current plans for return to the Moon call for a human rated version of Starship as a lunar lander “…no earlier then 2025”. However, Japanese billionaire Yusaku Maezawathe’s Dear Moon mission sending 8 crew members around Luna with a crewed Starship is still planned for 2023. A lot of details are yet to be worked out and we still have not covered the topic of Planetary Protection nor the granting of a launch license to SpaceX by the FAA, but could a Starship human mission to Mars take place in 2028? Let me know what you think.
“The SpaceX Starship vehicle fundamentally changes the paradigm for human exploration of space and enables humans to develop into a multi-planet species.”
* Authors of Mission Architecture Using the SpaceX Starship Vehicle to Enable a Sustained Human Presence on Mars Jennifer L. Heldmann, Margarita M. Marinova, Darlene S.S. Lim, David Wilson, Peter Carrato, Keith Kennedy, Ann Esbeck, Tony Anthony Colaprete, Rick C. Elphic, Janine Captain, Kris Zacny, Leo Stolov, Boleslaw Mellerowicz, Joseph Palmowski, Ali M. Bramson, Nathaniel Putzig, Gareth Morgan, Hanna Sizemore, and Josh Coyan
The NERVA solid core nuclear rocket engine. Credits: NASA
James Dewar believes it is time to reconsider the solid core nuclear thermal rocket, like what was developed in the 1960s under the NASA’s Nuclear Engine for Rocket Vehicle Application (NERVA) Project, as a high thrust cargo vehicle for opening up the solar system and for solving problems here on Earth. A tall order, as he explained in his appearance on The Space Show (TSS) October 26, because nuclear propulsion within the atmosphere and close to the Earth was taken off the table by NASA over 60 years ago and research on nuclear rockets was put on ice after 1973 until recently. Dewar worked on nuclear policy at the Atomic Energy Commission and its successor agencies, the Energy Research and Development Administration and the Department of Energy. He has documented his views in a paper linked on TSS blog.
What is old could be new again. NERVA had a very light high power solid core reactor with Uranium 235 fuel in a graphite matrix creating nuclear fission to heat hydrogen to produce rocket thrust. The specific impulse (efficiency in conversion of fuel to thrust) of the first iteration of NERVA was about 825 seconds, or almost twice that of chemical rockets. More efficient versions were on the drawing board. The compact design (35×52-inch core) lends itself to low development costs and would be inexpensive to fabricate and operate. It has the potential to lower launch costs significantly and research could pick up where it left off nearly 50 years ago.
So why is NASA announcing development of new nuclear thermal propulsion systems for missions to Mars in the distant future? The reactor cores like those used in Project NERVA are known technologies that can it be adapted for other useful applications and it can be done safely on Earth. There could be a large niche market for energy production in remote rural areas such as Alaska or Canada, or supplementing base load utilities during power disruptions due to severe weather events. With their high operating temperatures, these reactors can replace fossil fuel power generation for manufacturing industries that require process heat such as steel/aluminum or chemical production, which cannot be powered efficiently by wind or solar energy. There may also be a cost advantage and environmental benefit to replacing carbon based fuels for powering maritime oceangoing vessels.
“Even the Greens may support it…What if a reestablished program included making a nuclear propelled 1000-foot tanker sized skimmer to rid the oceans of plastic?”
Additionally, a nuclear reactor of this type could service manufacturing centers in both space and on Earth. It could inexpensively launch satellites and provide power for environmental and solar weather stations to monitor and protect Earth’s health. Dewar even thinks that the solid core nuclear reactor could be used to address the growing global problem of industrial waste by melting it down to its chemical constituents and then separating out commercially valuable components from the actual waste prior to permanent disposal. The low launch costs of the nuclear rocket may actually make disposal of waste off Earth economically feasible. Whole clean industries could spring up around these process centers. So this type of reactor could address many national goals and objectives rather than just crewed missions to Mars or deep space.
But what about the elephant in the room? Safety, radiation and fear of all things “nuclear”? Would the public support ground based testing if a NERVA type solid core nuclear thermal rocket program were restarted? Dewar covers this in detail in his book The Nuclear Rocket, Making Our Planet Green, Peaceful and Prosperous. As reported by the EPA in 1974, “…It is concluded that off-site exposures or doses from nuclear rocket engine tests at [the] NRDS [Nuclear Rocket Development Station] have been below applicable guides.”
What about regular launches of a nuclear rocket in the Earth’s atmosphere? First, the launch range proposed would be in an isolated ocean area over water to eliminate the possibility of failure or impact in populated regions. Second, the nuclear core would be enclosed in a reentry vehicle type cocoon for safe recovery in the event of an accident. Third, the nuclear engine is envisioned as an upper stage and would not be “turned on” until boosted high in the stratosphere, thus emission of gamma rays and neutrons from the fission reaction would not be any different then the radiation already impinging on our atmosphere from cosmic and solar radiation.
“…the best way to banish fear is for citizens to profit from the program.”
There is also the potential for the U.S. and its citizens to profit from this venture. Dewar suggests a governance framework for creating a public/private corporation in which the private sector is in charge, but leases assets from NASA and DOE. The government would support the venture via isolated testing sites, providing technical advice, supplying the uranium fuel and security to guard against potential nuclear proliferation. The public/private partnership would be set up to incentivize citizen participation through stock purchases and distribution of dividends in addition to providing jobs and funding the missions.
“Another source of funding would exist beyond the government or private billionaires: the public now has access”
Dewar concludes his paper with an inspirational statement: “…a new space program emerges based on science, not emotion, one that maximizes the technology for terrestrial applications, one that neuters the rocket equations and democratizes the space program, allowing citizens to participate and profit, and one that ever integrates Earth into the Solar System.”
Artist depiction of Starship on the lunar surface returning astronauts to the Moon as part of NASA’s Artemis Program. Credits: SpaceX
What will be the impact on the direction of U.S. space policy should SpaceX successfully demonstrate an orbital flight of Starship? Doug Plata, President and Founder of the Space Development Network believes that when Starship achieves orbit, policy makers should “…place Starship at the center of the country’s human spaceflight program…”. In an article in The Space Review he makes the case that if successful in its efforts, SpaceX may be edging us closer to a tipping point on deciding which path to take for the country’s human rated launch vehicle: Space Launch System (SLS) or Starship? This question is accentuated by recent news reports of yet another delay in the Artemis 1 uncrewed test flight of SLS which Ars Technica reports may not launch until the summer of 2022…assuming everything goes perfectly. Meanwhile, SpaceX continues its development of Starship at a breakneck pace, while simultaneously building the manufacturing infrastructure to “…crank them out by the hundreds”, says Plata. With the delay of Artemis 1, it is possible that SpaceX will demonstrate the first orbital launch of Starship before NASA’s first launch of SLS.
NASA has already selected SpaceX to return astronauts to the Moon via Starship as the Human Landing System for the Artemis program, although work has stalled on the contract due to Blue Origin’s lawsuit. But with a reusable Starship at a fraction of the cost, comparable heavy lift capability and a much higher flight rate, how long can SLS last? A case could be made for keeping SLS until SpaceX’s Super Heavy booster is human rated and Starship can be reliably shown to reenter the Earth’s atmosphere and land safely. But this won’t be long given Elon Musk’s aggressive timelines. Will it continue to make sense to launch astronauts on SLS/Orion, transfer them to Starship in lunar orbit and descend to the surface of the Moon when the the whole mission could be accomplished without SLS at a fraction of the cost?
“At some point, it will be obvious that SLS is an unnecessarily expensive alternative to Starship”
With Starship’s anticipated payload capabilities of delivery of 100s of tons and large crews to the lunar surface, and recent advances in inflatable technology, a habitat with a footprint of about 21,000 sq. ft. is within reach. Plata believes that the billions of dollars slated for SLS would be better spent contracting with SpaceX for delivery of inflatables and their supporting infrastructure to the lunar surface. This could lead to a large international lunar base which may eventually become a permanent settlement.
Conceptual illustration of InstaBase – a fully inflatable lunar base capable of supporting an initial crew of eight. Credits: The Space Development Network via The Space Review
“But there is an important historic significance to Starship as well…the real historic prize to be seized is the establishment of humanity’s first foothold off Earth.”
