There is global space race among countries to build Moon bases, harness it’s mineral resources and helium-3, fuel for future nuclear fusion power plants. Space agencies in China, Japan, Europe, Russia, Iran , Canada and a few private companies all hope to send people to the moon by as early as 2025. They’re talking about building bases, mining for natural resources, and studying the moon in unprecedented detail. A key figure at the European Space Agency says we must look at how we exploit the moon’s resources before it is too late, as missions begin surface mapping.
One day humans may live and work on the moon for weeks or even months. Energy and power will make it possible to travel to and live on the lunar surface. Humans must choose the appropriate energy source and technological means to produce that power. Another is the energy needed to support sustained human presence and the beginning of the industrial activity.
Solar and nuclear heat sources are the basis of the production of energy in space. Solar energy is abundant on the surface of the Moon, but extended night hours (350 consecutive hours) and the extreme environmental temperature change from daylight to nighttime, create problems for solar power use. Earth also addresses similar issues, where demand for additional renewable energy generation, including solar, is rising, but additional power management, distribution, and energy storage solutions are needed to address issues such as intermittency and resiliency.
An orbital lunar mapper has only small power requirements. An unmanned surface explorer would require only a few (2-5) kilowatts continuously, for movement, surface coring, analysis, and telemetry. A radioisotope generator [a radioisotope thermoelectric generator] with dynamic conversion is the technology of choice. Lunar camp, to be inhabited only during the 2 weeks of the lunar day, would initially requires 25 kW, supplied by a solar photovoltaic system. this initial power level could be augmented during future visits using similar or improved photovoltaic technology. Or the lunar camp’s power system could grow, in the same manner as that of the space station, to include solar dynamic or nuclear supplies. the initial power level is suitable for crew life support, lunar science, and light work, but it does not provide the storable energy for heat and life support during the lunar night. For full-time habitation, the camp and later the base would rely on nuclear power supplying a few hundred kilowatts.
The sustainable future of lunar exploration is likely to depend upon the effective use of in situ resources to generate products such as oxygen, water and other used consumables. The use of In Situ Resource Utilisation (ISRU) may provide a means of reducing the ultimate cost and risk of operation on the moon and provide a means for commercial contributions to lunar exploration. Potential products include O2 and H2O for life support or H2 and O2 for fuel and propellant (also potentially by hydrazine production from N2, NH3 and H2O2).
The presence of large quantities of water on the surface of the Moon has major implications for ISRU as a potential source of water and oxygen for life support and hydrogen for fuel. In this case the major challenge for ISRU technologies will be the extraction of ice from such cold and dark environments. As a first step however the extent, quantity, distribution and nature of this ice must be identified.
European Space Agency (ESA) Moon Village
One such study has recently emerged in Europe with a concept for a ‘Moon Village’, which was prepared by the European Space Agency (ESA) with input from the US architectural firm Skidmore, Owings & Merrill and the Massachusetts Institute of Technology. The word ‘village’ perhaps sounds a bit grand as the base is modelled for a crew of just four people for a period of up to 300 days at a time – the maximum duration recommended based on radiation exposure assessment. But with the various systems envisaged for living and working on the moon and transfer to and from the Earth, over time it would come to expand into a village and perhaps eventually even into a town or city.
The basic living structure proposed, named the Habitat, is comprised of a vertical rigid central frame with an inflatable multilayer shell. When deployed it would provide a four-storey structure, roughly ellipsoidal in shape, about 15.5m in height and 10.5m in diameter with a pressurised volume of almost 700m3. Within the structure, the space would be modularised to provide for private quarters, cooking and dining, work, exercise, hygiene and other activities.
Core to the running of Habitat is the power availability. Its external structure could provide a limited space for solar PV, but with a maximum output unlikely to exceed around 1kW this would be inadequate for living, although it could be utilised during the transfer flight and as back-up. Thus an external power plant would be essential.
Various studies have provided a range of estimates for the power requirements from a base of 10kW/person up to 60kW continuous consumption for a crewed habitat at full power. A subsystem breakdown for the proposed Habitat indicates an average power requirement (including 20% margin) of 57kW during the day and 60kW during the night. Two proposals are made for a lunar power plant, using either solar PV or nuclear fusion.
Solar power plant
A solar power plant at the south pole would have to maintain an array of solar panels facing horizontally, with a rotational capability in order to track the sun through 360° over the course of the month. However, such a power station would have to overcome the problem of mutual shadowing, in which some panels would always be shadowed from the horizontal sun by some neighbouring panels, or indeed by any other surface constructions such as the Habitat itself. Furthermore, the darkness periods demand the inclusion of large energy storage capability.
Based on a 59kW power requirement for the Habitat, a solar system with a battery would require approximately 282m2 of solar panels, while a solar system with regenerative fuel cell storage would require 329m2 of solar panels. The latter, however, is much lighter at a total mass of 14t, whereas the solar battery power station comes in at 68t due to the much greater weight of the lithium-ion batteries.
On the power front the study does not indicate a preference for either the solar PV or nuclear fission reactor option. Potentially some hybrid combination is the more likely, if only to provide a level of technology redundancy.
NASA Nuclear fission plant
The second option of a nuclear fission reactor is a technology that is already under development for space travel and lunar surface applications, particularly within NASA. As far back as 2018 NASA and the US Department of Energy demonstrated the Kilopower reactor named Krusty (Kilopower Reactor Using Stirling Technology) capable of providing up to 10kW of electrical power for at least 10 years.
The prototype system uses a solid cast uranium-235 reactor core, about the size of a paper towel roll, and passive sodium heat pipes transfer reactor heat to high efficiency Stirling engines, which convert the heat to electricity. As many Krustys as are required to meet the power requirements could be implemented together. A nuclear fission reactor would be more compact, for a given power capability, than a solar power farm. However, extensive cooling radiators are required to reject the waste heat at a temperature low enough to suit the power conversion principle involved.
Protection of crew and systems from the ionising radiation emissions of an operating reactor also is a requirement and would be achieved by a combination of distance and shielding by regolith (unconsolidated residual or transported material that overlies the solid rock on the earth, moon, or a planet [Merriam-Webster Dictionary]), most likely by burial. The mass of a space fission reactor system depends on various design parameters and assumptions, but a broad estimate indicates a total power station mass of about 5.6t to deliver the Habitat’s 59kW requirement.
This is at least an order of magnitude lighter than a solar power plant. A nuclear fission reactor approach also has the advantage that its development would be applicable to non-polar lunar applications, providing wider mission flexibility. NASA says the Kilopower project team is developing mission concepts and performing additional risk reduction activities to prepare for a possible future flight demonstration.
Anthony Calomino, NASA’s nuclear technology portfolio lead within the Space Technology Mission Directorate, said that the plan is to develop a 10-kilowatt class fission surface power system for demonstration on the moon by the late 2020s. The facility will be fully manufactured and assembled on Earth, then tested for safety and to make sure it operates correctly.
Afterwards, it will be integrated with a lunar lander, and a launch vehicle will transport it to an orbit around the moon. A lander will lower it to the surface, and once it arrives, it will be ready for operation with no additional assembly or construction required. The demonstration is expected to last for one year, and could ultimately lead to extended missions on the moon, Mars, and beyond.
“Once the technology is proven through the demonstration, future systems could be scaled up or multiple units could be used together for long-duration missions to the moon and eventually Mars,” Calomino said. “Four units, providing 10 kilowatts of electrical power each, would provide enough power to establish an outpost on the moon or Mars. The ability to produce large amounts of electrical power on planetary surfaces using a fission surface power system would enable large-scale exploration, establishment of human outposts, and utilization of in situ resources, while allowing for the possibility of commercialization.”
NASA is working on this with the Idaho National Laboratory (INL), a nuclear research facility that’s part of the DOE’s complex of labs. “A low enriched form of nuclear fuel will power the nuclear core,” Steve Johnson, director of the Space Nuclear Power and Isotope Technologies Division at the Idaho National Laboratory, said. “The small nuclear reactor will generate heat that is transferred to the power conversion system. The power conversion system will consist of engines that are designed to operate on reactor heat rather than combustible fuel. Those engines use the heat, convert it to electric power that is conditioned and distributed to user equipment on the lunar and Martian surfaces. Heat rejection technology is also important to maintain the correct operating temperatures for the equipment.”
“The fission surface power system will be designed to operate at around 10 kilowatts of electrical power for around 10 years,” he said, adding that 10 kilowatts is roughly equivalent to the amount of energy needed to power five to eight large households.
“These missions could call for a variety of solar, battery, radioisotope and fission power systems to enable a wide range of demanding requirements,” he said. “Fission surface power is necessary in places where solar power, wind and hydro power are not readily available. On Mars, for example, the sun’s power varies widely throughout the seasons, and periodic dust storms can last for months. On the moon, the cold lunar night lingers for 14 days, while sunlight varies widely near the poles and is absent in the permanently shadowed craters. In these challenging environments, power generation from sunlight is difficult and fuel supply is limited. Fission surface power offers a lightweight, reliable and efficient solution.”
NASA Watts on the Moon’ challenge
As NASA works to extend human exploration of the solar system, unprecedented capacity for energy distribution, management, and storage will be needed to support sustained human presence and the beginning of industrial activity. NASA’s Watts on the Moon Challenge seeks solutions for energy distribution, management, and/or storage that address NASA technology gaps and can be further developed for space flight and future operation on the lunar surface. Not only could novel solutions make a difference in lunar and space exploration, but technologies discovered during NASA’s Watts on the Moon competition could help facilitate new power options on Earth.
Through the ‘Watts on the Moon’ challenge, NASA seeks proposals to develop and demonstrate solutions for the distribution, management and/or storage of energy. The intermittency and resiliency of solar with the extended dark periods are among the issues that must be addressed. Three power delivery activities are up for solutions, which are expected by September 2023.
1. Deliver power from a power plant on the rim of a crater to a mobility platform operating in the crater that collects and delivers icy regolith2 to a water extraction plant.
2. Deliver power from the power plant to the water extraction and purification plant operating inside the crater.
3. Deliver power from the power plant to an oxygen-producing pilot plant operating outside the crater, which extracts oxygen from the delivered material.
Other areas that NASA is pursuing in its lunar surface technology research drive include wireless energy transmission technologies for power distribution to difficult to reach areas such as those in permanent shadow and for mobile applications; batteries for sustained low-temperature operation and advanced power control technologies for interconnected systems.
Opened in September 2020, the Watts on the Moon Challenge is a $5 million, multi-phase competition developed to advance the nation’s lunar exploration goals by challenging U.S. innovators to develop breakthrough energy storage and use technologies that make longer-lasting Moon missions, and the discoveries they uncover, possible.
NASA has awarded $500,000 to seven winning teams in Phase 1 of the agency’s Watts on the Moon Challenge. The technology design competition challenged U.S. innovators, from garage tinkerers to university researchers and startup entrepreneurs, to imagine a next-generation energy infrastructure on the Moon.
Sixty teams submitted original design concepts aimed at meeting future needs for robust and flexible technologies to power human and robotic outposts on the Moon. After evaluation by a judging panel, NASA announced the winners during a private awards ceremony May 20.
The winning teams are:
Astrobotic Technology, Inc. of Pittsburgh: $100,000
Planetary Surface Technology Development Lab at Michigan Technological University in Houghton, Michigan: $100,000
Skycorp Inc. of Santa Clara, California: $100,000
Astrolight of Rochester, New York: $50,000
KC Space Pirates of Kansas City, Missouri: $50,000
Moonlight from the University of California, Santa Barbara: $50,000
Team FuelPod of Johnstown, Colorado: $50,000
“Having a continuous supply of energy on the Moon requires a wide variety of inventive solutions,” said Jim Reuter, associate administrator for NASA’s Space Technology Mission Directorate. “We salute the bold, creative, and curious solvers who are helping us advance the technologies needed for sustainable living and working farther from Earth.”
Winning Phase 1 Concepts
To compete in Phase 1, eligible teams had six months to register and submit ideas for up to three parts of a hypothetical mission scenario – harvesting water and oxygen from a dark crater at the Moon’s South Pole with energy generated by a power plant located on the crater’s outer rim.
The mission scenario included three different activities with different needs for power or energy capacity, different distances from the primary power source, different mobility features, and different operational duty cycles. The panel of judges from government, industry, and academia scored submissions on their scientific and technical merit, applicability, feasibility, and development potential with extra points awarded for solutions that could benefit Earth.
The first mission activity challenged teams to deliver power from the power plant to a mobility platform, or rover, operating inside the crater. The mobility platform collects and delivers icy regolith to the water extraction plant. Astrobotic, the $100,000 grand prize winner in this category, proposed a fleet of small tethered rovers that lay out and connect power cables between the power plant and mobility platform. KC Space Pirates, a team of inventors and space enthusiasts, and UC Santa Barbara’s team Moonlight each won $50,000 for their proposed laser power beaming concepts.
The next mission scenario tasked teams with delivering power from the power plant to a water extraction plant inside the crater. Michigan Technological University’s Planetary Surface Technology Development Lab won the $100,000 grand prize in this category for their proposed system of tethered rovers that unspool superconducting wire into the crater. Astrolight – a collaboration between Astrobotic and Montreal startup Eternal Light Photonics Corp. – won $50,000 for its wireless mobile power beaming solution. And Team FuelPod from Orion AI Labs, an applied robotic research institution, won $50,000 for its intelligent microgrid concept that uses machine learning and a modular system of lithium ion battery-powered pods.
Mission activity three involved delivering power to an oxygen-producing plant outside the crater. Skycorp Inc. won the $100,000 grand prize for its innovative system of power cells and intelligent interfaces for storing and distributing power through the lunar month’s extreme light and temperature changes.
“Congratulations to our Phase 1 winners of NASA’s Watts on the Moon Challenge,” said Dr. Marla Pérez-Davis, director of the agency’s Glenn Research Center in Cleveland. “Not only could these award-winning concepts make a difference in space exploration, but technologies discovered during the competition could drive clean energy innovation and make a positive impact on Earth.”
The second phase of the Watts on the Moon Challenge is a $4.5 million technology demonstration competition. To win a share of the prize purse, participants must build working prototypes to show how their solutions work. Phase 2 registration is scheduled to open in fall 2021.
More about the Watts on the Moon Challenge
The Watts on the Moon Challenge is managed by NASA Glenn and is part of Centennial Challenges, based at the agency’s Marshall Space Flight Center in Huntsville, Alabama. Centennial Challenges is a part of the Prizes, Challenges, and Crowdsourcing program within the agency’s Space Technology Mission Directorate. Centennial Challenges has contracted HeroX to support the administrative part of this challenge.
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