Lunar Surface-to-Surface Power Transfer

Abstract

A human lunar outpost, under NASA study for construction in the 2020's, has potential requirements to transfer electric power up to 50-kW across the lunar surface from 0.1 to 10-km distances. This power would be used to operate surface payloads located remotely from the outpost and/or outpost primary power grid. This paper describes concept designs for state-of-the-art technology power transfer subsystems including AC or DC power via cables, beamed radio frequency power and beamed laser power. Power transfer subsystem mass and performance are calculated and compared for each option. A simplified qualitative assessment of option operations, hazards, costs and technology needs is also described. Based on these concept designs and performance analyses, a DC power cabling subsystem is recommended to minimize subsystem mass and to minimize mission and programmatic costs and risks. Avenues for additional power transfer subsystem studies are recommended. IntroductionConsistent with "The Vision for Space Exploration," NASA is planning to send humans to the Moon and other deep space targets. As part of the lunar exploration planning, NASA convened a "Lunar Architecture Team" or LAT. One output of the LAT was a strategy to develop a permanent human outpost at the lunar South Pole on The Shackleton Crater rim (Cooke et al., 2006). This lunar outpost will be comprised of multiple elements distributed across the lunar surface, each requiring electric power. Thus, power must be transferred from power system elements to surface elements and surface payloads. A prime example payload element is an in situ resource utilization (ISRU) oxygen production plant. Such a plant requires considerable power and must be located remotely from the outpost to minimize induced contamination from dust generation during plant operations.In support of lunar outpost power system development, the goal of this present study was to develop lunar surface-to-surface power transfer subsystem concept design options, compare option quantitative and qualitative metrics, and on the basis of this comparison, make a recommendation of the option with best balance of mass, performance, risk and cost. Most past studies on this topic have focused on a power cable power transfer approach (Gordon, 2001;Khan, et al., 2006;Sprouse, 1991). In the current study, the power transfer subsystem technology options not only include AC and DC power cables, but also radiofrequency (RF) beamed power and solid state laser module beamed power technology options. These concept designs include the required supporting equipment, such as power conditioning electronics and an Active Thermal Control System (ATCS), which can be dominant mass contributors to the total power transfer subsystem mass. The designs also incorporate the appropriate level of fault tolerance against critical and catastrophic faults required of human-rated space systems.Concept designs were prepared for power transfer levels between 1 to 50 kW and transfer distances between 0.1 to 10 km that are consisten...

Space Microgrids for Future Manned Lunar Bases: A Review

“…Multilayer materials are excessively used to prevent the high thermal flux, reduction of the environmental temperatures, and temperature gradients [64]. Also, Active Thermal Control System (ATCS) can be employed to heat and cool as required to maintain the operating temperature range of different electrical systems as mentioned in [65]. ATCS involves electrically powered heaters using resistances and cooler plates using refrigeration devices such as cryocoolers around the electrical equipment [66].…”

“…A space MG on the Moon may have the requirement to transmit about 50kW of power from 0.1km to 10km. The power can be transported using wired AC and DC power cables, wireless beamed power using radio frequency (RF) and solid-state lasers [65]. A similar approach is discussed in [57], where a solar power station in the lunar orbit can generate power and beam it to the lunar base using the microwave.…”

“…A similar approach is discussed in [57], where a solar power station in the lunar orbit can generate power and beam it to the lunar base using the microwave. Different power transmission technologies require certain supporting equipment which adds to the total EPS mass while some components also need passive and active thermal management system for heating and cooling [65]. For AC and DC power cables, the power transmission system mass is directly proportional to the power levels.…”

“…For AC and DC power cables, the power transmission system mass is directly proportional to the power levels. At higher voltages, although the conductor size reduces [11], [65], the wire insulation mass and thickness increases [65]. Using the RF systems, power can be transferred at a frequency of 2.45GHz or 5.8GHz.…”

“…It involves an assembly of ATCS cooled magnetron, and passively cooled transmit antenna and rectenna arrays. At 5.8GHz frequency, free space transmission efficiency increases, and therefore the power subsystem mass and input power is reduced compared to 2.45GHz systems [65]. However, both the power at the input source and the subsystem mass increases in orders of magnitude with an increase in transmission distance, due to the increase in free space losses [65].…”