Peaks of Eternal Light at the lunar south pole annotated with crater labels. Mosaic of 40 images taken by the ESA SMART-1 spacecraft 2005/2006. Area covers 500 x 150 km. Credits: ESA/SMART-1/AMIE camera team; M. Ellouzi/B. Foing, CC BY-SA 3.0 IGO
As most space settlement enthusiasts know, the Peaks of Eternal Light on the rims of craters in the lunar polar regions hold much promise as the ideal location to place collectors for solar energy to power ice mining operations. At the south pole in particular, these peaks lie within just a few kilometers of large frozen water deposits in the permanently dark shallows. But how much solar power is available? Companies such as Trans Astronautica Corporation will want to know so they can inform plans for their Sun Flower™ collector invention as part of a Lunar Polar Mining Outpost.
In a paper posted this month on the pre-print server arXiv.org, a team of researchers at Harvard University and Technische Universität Berlin present the results of a study to answer this question. Using data from high resolution maps of solar illumination on the ridges of Shackleton crater and others, they determined the total available power from collector towers of various heights if they were placed at these locations.
The study found that the power available depends heavily on the height of the panels above the local surface but could be substantial, from a few megawatts for towers of heights less than 100m up to the gigawatt range for towers of 500m or more. This is sufficient power for mining several thousand tons of water per year from Shackleton crater.
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 response to environmental change. Credits: Biosphere 2 / University of Arizona
Once cheap access to space is realized, probably the most important technological challenge for permanent space settlements behind radiation protection and artificial gravity is a robust environmental control and life support system (ECLSS). Such a system needs to be reliably stable over long duration space missions, and eventually will need to demonstrate closure for permanent outposts on the Moon, Mars or in free space. In his thesis for a Master of Science Degree in Space Studies, Curt Holmer defines the stability of the complex web of interactions between biological, physical and chemical processes in an ECLSS and examines the early warning signs of critical transitions between systems so that appropriate mitigations can be taken before catastrophic failure occurs.
Holmer mathematically modeled the stability of an ECLSS as it is linked to the degree of closure and the complexity of the ecosystem and then validated it against actual results as demonstrated by NASA’s Lunar-Mars Life Support Test Project (LMLSTP), the first autonomous ECLSS chamber study designed by NASA to evaluate regenerative life support systems with human crews. The research concluded that current computer simulations are now capable of modeling real world experiments while duplicating actual results, but refinement of the models is key for continuous iteration and innovation of designs of ECLSS toward safe and permanent space habitats.
This research will be critical for establishing space settlements especially with respect to how much consumables are needed as “buffers” in a closed, or semi-closed life support system, when the model’s metrics indicate they are needed to mitigate instabilities. Such instabilities were encountered during the first test runs of Biosphere 2 in the early 1990s.
As SpaceX races to build a colony on Mars, they will need this type of tool to help plan the life support system. Holmer believes that completely closed life support systems for relatively large long term settlements are at least 15 to 20 years away. That means that SpaceX will need to resupply materials and consumables due to losses in their initial outpost who’s life support system in all probability will not be completely closed during the early phases of the project over the next decade. Even SpaceX cannot reduce launch costs low enough to make long term resupply economically viable. They will eventually want to drive toward a fully self sustaining ECLSS. That said, depending on how the company funds its initiatives and sets up it’s supply chains, they may not need a completely closed system for quite some time.
Of course there are sources of many of the consumables on Mars that could support a colony but not all the elements critical for ecosystems, such as nitrogen, are abundant there. There are sources of some consumables outside the Earth’s gravity well which could lower transportation costs and extend the timeline needed for complete closure. SSP covered the SHEPHERD asteroid retrieval concept in which icy planetesimals, some containing nitrogen and other volatiles needed for life support, could be harvested from the asteroid belt and transported to Mars as a supply of consumables for surface operations. TransAstra Corporation is already working on their Asteroid Provided In-situ Supplies family of flight systems that could help build the infrastructure needed for this element of the ecosystem. It may be a race between development of the competing technologies of a self-sustaining ECLSS vs. practical asteroid mining. The bigger question is if humans can thrive long term on the surface of Mars under .38G gravity. In the next century, O’Neill type colonies, perhaps near a rich source of nitrogen such as Ceres, may be the answer to where safe, long term space settlements with robust ECLSS habitats under 1G will be located.
Curt Holmer appeared recently on the The Space Show discussing his research. I called the show and asked if he had used his modeling to analyze the stability of ecosystems sized for an O’Neill-type colony. He said he had only studied habitats up to the size of the International Space Station, but that it was theoretically possible to analyze this larger ecosystem. He said he would like to pursue further studies of this nature in the future.
Artist’s concept of projects which could benefit from DARPA’s (NOM4D) plan for robust manufacturing in space. Credits: DARPA
Pronounced “NOMAD” the Defense Advanced Research Projects Agency plan aims to develop technologies for adaptive, off-earth manufacturing to fabricate large structures in space and on the Moon.
Bill Carter, program manager in DARPA’s Defense Sciences Office explains in an announcement of the program, “We will explore the unique advantages afforded by on-orbit manufacturing using advanced materials ferried from Earth. As an example, once we eliminate the need to survive launch, large structures such as antennas and solar panels can be substantially more weight efficient, and potentially much more precise. We will also explore the unique features of in-situ resources obtained from the moon’s surface as they apply to future defense missions. Manufacturing off-earth maximizes mass efficiency and at the same time could serve to enhance stability, agility, and adaptability for a variety of space systems.”
The program will be split into three 18 month phases driven by metrics associated with progressively challenging exemplars such as respectively, a 1-megawatt solar array, a 100m diameter RF reflector, and finally IR reflective structures suitable for use in a segmented long-wave infrared telescope.
Lessons learned from the program could be applied to on-orbit manufacturing operations by commercial space companies as launch costs come down and access to cislunar space becomes more routine for both government and commercial entities.
Artist depiction of an O’Neill cylinder from the novel K3+. Credits: Katie Lane (Full distribution rights reserved by Erasmo Acosta)
Erasmo Acosta thinks we might be headed in the wrong direction, that we may be suffering from planetary chauvinism and the better way may be to colonize space with O’Neill cylinders. He makes his case in a post on the Predict section of Medium. SSP has long been a strong proponent of free space O’Neill-type settlements, the advantages of which are numerous, not the least of which is 1G artificial gravity to prevent detrimental human health issues that may arise for occupants of colonies with lower gravity on the Moon or Mars. Such space settlements would house millions of people in perfect 70 degree controlled weather without the threat of natural disasters.
Jeff Bezos has advocated for this philosophy with the aim of moving heavy industry off world and preserving Earth’s environment for “residential zoning”. Recent developments seem to indicate he may be spending more of his time focusing on the realization of that vision.
Acosta, a retired software engineer, feels so strongly that O’Neill cylinders will be the preferred mode of space settlement he wrote a novel called K3+ which depicts a future in the next century where humans will be living in thousands of O’Neill cylinders in a “post-scarcity” civilization of virtually unlimited resources. Acosta envisions Mercury as a source of raw materials:
“The planet’s proximity to the sun, its low gravity, and metal-rich concentration make it the ideal source of raw materials for constructing thousands of O’Neill cylinders.”
In a previous post on Predict, he explains how to kickstart a program for harnessing space resources to fabricate these colonies.
After many years of construction, multiple rings of rotating habitats would eventually encircle the sun harnessing a vast amount of the energy output of our star approaching the configuration of a Dyson sphere.
Artist depiction of multiple rings of rotating habitats around the sun. Credits: Katie Lane (Full distribution rights reserved by Erasmo Acosta)
Finally, as a tribute to the father of free space colonies and an inspiration for a generation of space settlement advocates, I’d like to close out this post with a link to the just released trailer for the much anticipated documentary: The High Frontier, The Untold Story of Gerard K. O’Neill.
Artist’s depiction of activities at an early Mars base which could include methane production. Credits: NASA
A team of physicists at the University of California, Irvine has found a short cut for efficient propellant production on Mars. The UCI researchers have discovered a way to streamline the conventional two step Sabatier process which first electrolyzes water into hydrogen before reacting with carbon dioxide in the Martian atmosphere to create methane. Both SpaceX and Blue Origin use methane in their rocket engine designs. The novel approach simplifies fuel production by leveraging zinc as a “synthetic enzyme,” which catalyzes carbon dioxide to synthesize methane directly. The improved process will reduce the amount of ISRU equipment (and therefore weight and launch costs) needed for transport to the surface of Mars to facilitate propellent production required for the trip home. The research has only demonstrated proof of concept so follow-on studies are required to improve the TRL for flight-ready hardware.
Artist impression of the MOONRISE laser mounted on a lunar rover for fabrication of structures on the Moon. Credits: Laser Zentrum Hannover / 3D Printing Industry
A German company called Laser Zentrum Hannover .eV in partnership with the Technical University of Braunschweig has been working on a project called MOONRISE which aims to use laser technology to build a village on the Moon out of lunar regolith. Toward that end, the team for the first time has demonstrated the ability to 3D print structures out of simulated lunar regolith under lunar gravity conditions. The results of their experiments are described in an article in 3D Printing Industry.
The research was carried out in the Leibniz University Hannover’s Einstein-Elevator, a large-scale drop tower device in which experiments can be run under variable gravity conditions at a high repetition rate.
Initiated in 2019, Project MOONRISE is funded by the Volkswagen Foundation and is focused on improving the technology readiness level of additive manufacturing using lunar regolith as building material.
Artist impression of ISRU activities on the Moon. Credits: NASA
What do space experts in industry and academia think will be the technical and policy challenges to overcome for a sustainable lunar outpost leveraging ISRU by 2040 to be realized? A survey using the Delphi method has just been completed to answer this question. The results were just released as a pre-proof in Acta Astronautica. Significant contributors in the fields of ISRU technologies, space architecture, power systems, and space exploration participated in the survey.
There was a group consensus that NASA’s Artemis mission returning humans to the Moon would be delayed by at least 2 years from the previous administration’s target of 2024 due to uncertainty in U.S. policy over the next few years. No surprise here. There was also agreement that ISRU processes could add significant power requirements on the order of 1 MW to a lunar base, and that photovoltaic systems were preferred over nuclear power sources because of a “…political distaste for space nuclear power systems”. Of particular note, the survey participants could not reach agreement on the impact that Covid-19 would have on space exploration.
Artist impression of activities at a Moon Base which could include oxygen production. Credits: ESA – P. Carril
Kevin Cannon of the Cannon Group at the Colorado School of Mines can help find the answer. In a recent post on his Planetary Intelligence blog, the Assistant Professor of Geology and Geological Engineering describes a trade study comparing extraction of oxygen from regolith such as Metalysis’ ESA funded study to getting O2 from ice mining at the lunar poles as favored by NASA. Nothing stands out from a cursory look at the pros and cons of each approach.
In a more data driven analysis to compare apples to apples, Cannon examines energy costs of mining oxygen and plots it against the amount of bulk material that has to be processed to produce an equal amount of O2 from different sources ranging from plain silicate regolith to various grades of water ice endmembers. The analysis even includes processing material from various types of asteroid resources. The types of ice/regolith mixtures can vary widely as described in one of Cannon’s tweets.
Artist’s impression of different types of water ice / regolith endmembers. Credits: Lena Jakaite / strike-dip.com / Colorado School of Mines
Cannon’s analysis reaches the conclusion that “At 1.5-2% water by weight, icy regolith is essentially on par with O2-from-regolith on a joule for joule basis. In other words, if you had a pile of icy regolith already sitting on the surface, it makes sense to throw it out if the grade is less than about 1.5% and extract oxygen directly from the silicate regolith instead.”
ArmorHab transport habitat configured for artificial gravity. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
The innovative ArmorHab mission architecture was presented at the Mars Society Conference in 2016. This novel approach should be considered as part of a strategy for settlement of the Red Planet. The concept integrates several engineering solutions for habitat design to address radiation protection, life support, and transportation while leveraging in situ resource utilization to enhance crew health, safety and reduce costs.
The basic building block of the architecture is a cylindrical Mylar shell wrapped in superconductive tape providing radiation protection through emulation of a magnetosphere. This structure is encased in a protective aerogel for strength and insulation including layers of water ice to further protect the crew from micrometeorites and algae bioreactors for scrubbing carbon dioxide for life support.
ArmorHab wall structure with superconducting tape for radiation protection and algae bioreactors for life support. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
Leveraging Buzz Aldrin’s Mars Cycler invention, the plan starts by building out infrastructure in cislunar space including automated factories on the Moon, then expanding out to Mars with space stations, cycling habitats and connecting “trucks” to provide transport to and from the surface of each destination.
Illustration of cycler model showing six TransportHabs, three space stations and a Mars Truck. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
Left – Image of the Photovoltaic Radio-frequency Antenna Module (PRAM). Credits: of U.S. Naval Research Laboratory. Right: X-37B orbital test vehicle. Credits: Boeing
The first on-orbit demonstration of wireless power transmission, technology that could eventually support elements of a space solar power satellite has just been completed and published in the IEEE Journal of Microwaves. This experiment, the first flight test of a solar-to-RF Photovoltaic Radio-frequency Antenna Module (PRAM) lovingly referred to as a “sandwich module”, was performed on the U.S Airforce’s X-37 Orbital Test Vehicle, the launch of which SSP covered last May. Preliminary results have duplicated in space the expected power transmission that was tested on the ground pre-flight. Although testing is just getting started, the results show proof of concept of this prototype PRAM paving the way for the next phase of the Space Solar Power Incremental Demonstrations and Research (SSPIDR) project planned by Air Force Research Laboratory. The primary objective of SSPIDR is delivery of power to forward deployed expeditionary forces on Earth which would assure energy supply with reduced risk and lower logistical costs. The technology could eventually be used for commercial energy production.
Modular solar-to-RF panels based on the PRAM concept will enable very large radio frequency power beaming apertures to be assembled from a single panel design leading to scalability, lower mass and reduced costs.
Depiction of the PRAM functional mechanism for solar power satellites. Credits: Christopher T. Rodenbeck et al. / IEEE Journal of Microwaves
The next step in Phase 1 of the the SSPIDR project will be the world’s first space-to-ground power beaming demonstration of a solar to-RF modular panel currently planned for 2023.
