Toward an Electric Power Utility on the Lunar Surface
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Lunar Electric Rovers (LER) are currently being developed that are substantially more capable than the Apollo vehicle (LRN ,"). Unlike the LRV, the new LERs provide a pressurized cabin that serves as short-sleeve environment for the crew of two, including sleeping accommodations and other provisions that allow for long tern stays, possibly up to 60 days, on the hear surface, without the need to replenish consumables from some outside source, such as a lander or outpost. As a consequence, significantly larger regions may be explored in the future and traverse distances may be measured in a few hundred kilometers (1, 2). However, crew safety remains an overriding concern, and methods other than "walk back", the major operational constraint of all Apollo traverses, must be implemented to assure -at any time- the safe return of the crew to the lander or outpost. This then causes current Constellation plans to envision long-tern traverses to be conducted with 2 LERs exclusively, each carrying a crew of two: in case one rover fails, the other will rescue the stranded crew and return all 4 astronauts in a single LER to base camp. Recent Desert Research and Technology Studies (DRATS) analog field tests simulated a continuous 14 day traverse (3), covering some 135 km, and included a rescue operation that transferred the crew and diverse consumables from one LER to another these successful tests add substantial realism to the development of long-term, dual rover operations. The simultaneous utilization of 2 LERs is of course totally unlike Apollo and raises interesting issues regarding science productivity and mission operations, the thrust of this note.
Moon Tycoon Version 2 (V2) enables and encourages in-situ resource utilization (ISRU) technology developers, principal investigators (PI), and managers across the agency to design and visualize various Lunar operations and missions with a high degree of photorealism. Users are completely immersed in the emulated Moon environment, enabling them to gain new knowledge as they explore the Lunar surface. Moon Tycoon V2 will soon be released to the NASA Software Catalog for public distribution, which will allow external partners, academia, and other interested parties from the public domain to take part.
Centrifuges will continue to serve as a valuable research tool in gaining an understanding of the biological significance of the inertial acceleration due to gravity. Space- and possibly lunar-based centrifuges will play a significant and enabling role with regard to the human component of future lunar and martian exploration, both as a means of accessing potential health and performance risks and as a means of alleviating these risks. Lunar-based centrifuges could be particularly useful as part of a program of physiologic countermeasures designed to alleviate the physical deconditioning that may result from prolonged exposure to a 1/6-g environment. Centrifuges on the lunar surface could also be used as part of a high-fidelity simulation of a trip to Mars. Other uses could include crew readaptation to 1 g, waste separation, materials processing, optical mirror production in situ on the Moon, and laboratory specimen separation.
Methodological and analytical capabilities associated with spark mass spectrometry and X-ray spectroscopy are presented for the determination of the elemental composition of samples of lunar regolith returned to the earth by Apollo 11 and Apollo 12. Using X-ray spectroscopy, the main constituents of samples of lunar surface material were determined, and using mass spectrometry -- the main admixtures. The principal difference of Apollo 11 samples from Apollo 12 samples was found for elements contained in microconcentrations. This is especially true of rare earth elements.
Results are reported for determination of the galactic cosmic ray flux during various time intervals in the 1965-1972 period, on the basis of data from the instruments of a spacecraft that made a soft landing on the lunar surface, and from the radioactivity of samples returned by the spacecraft. During minimum solar activity (the second half of 1965 and the beginning of 1966) I sub 0 (E greater than or equal to 30 percent MeV/nucleon) was determined to be 0.43 (plus or minus 10 percent). These values, within the error limits of the determinations, agree with the corresponding values of galactic cosmic ray intensities determined by stratospheric measurements. The mean flux of galactic cosmic rays over the past million years is equal to I (E greater or equal to 100 MeV/nucleon) + 0.28 (plus or minus 20 percent). This value agrees with the mean flux of modulated cosmic rays during the period of the nineteenth solar cycle. The mean flux of solar protons between 1965 and 1972 was 2.46.
Overview of synthetic lunar terrain generation methods used for the Resource Prospector and Volatiles Investigating Polar Exploration Rover projects.
Data are presented concerning the energy spectra of solar flare particles and the distribution of particles producing submicron diameter craters. Processes which alter the albedo and possibly the chemistry of exposed lunar surfaces are also considered. Measurements are reported of solar flare track gradients in rock 64455 which is sufficiently young to have uneroded surfaces on its sides. Attention is also given to accretionary particles adhering to host surfaces, microcraters on soil particles, and microcraters on the oriented surfaces of sample 76015 from a boulder at Station 6 of the Apollo 17 site.
A preliminary comparison of Surveyor 3 and Apollo 12 photographs of areas disturbed by the Surveyor is described. About 60 Surveyor pictures taken in April and May 1967 and 20 Apollo photographs including stereo pairs were examined in detail. Only one definite change in the surface, other than those produced by astronauts, was noted. This is a particle about 2 mm in diameter which appears in the Apollo photographs of a Surveyor footpad imprint but which does not appear in the Surveyor photographs. The walls made by Surveyor footpads and surface sampler were still in place, and surface areas darkened by ejected fines during the Surveyor landing still appeared dark. The absence of detectable craters in the footpad imprint implies a very low micrometeorite flux on the lunar surface.
The solar system is composed of numerous bodies orbiting the sun, and numerous satellites orbiting planets. However, no objects greater than a kilometer in diameter are known to orbit satellites. Theoretical arguments are used to show that most objects orbiting satellites ultimately would be destroyed by tidal interactions. This may explain why such objects have not been observed. These arguments are applied to objects orbiting the moon. The ages and sizes of most of the circular mare basins are compatible with the lifetimes and crater sizes expected for impacts by objects caught in decaying lunar orbits. The morphology of a few circular mare basins (Crisium, Serenitatis, and possibly Imbrium) indicates that they could have been formed by such impacts. Thus, the lunar surface may provide a record of impacts due to objects caught in tidally decaying lunar orbits.
A discrete Regenerative Fuel Cell (RFC), comprised of a Proton Exchange Membrane (PEM) Fuel Cell (FC) system integrated with a PEM Electrolyzer (EZ) system, can provide energy conversion and storage options for applications where batteries are not practical. This includes missions on the lunar surface where long charge and discharge periods result in extremely high battery system mass for sufficient energy storage. While both PEM FC and PEM EZ are mature terrestrial technologies, there is still a lot of development needed for aerospace applications. Integrating the PEM FC and PEM EZ systems together requires the integration of multiple thermal, fluid, and electrical subsystems, increasing the complexity of the overall RFC system. Additionally, Balance of Plant (BoP) components and subsystems play a crucial role in the effective performance to maximize the RFC round trip efficiency. This presentation will give a high-level overview of RFCs, select BoP components including a catalytic recombiner and gas drying equipment, and the current testing that is being done on the RFC project at NASA GRC.
Devices for lifting, translating and precisely placing payloads are critical for efficient Earthbased construction operations. Both recent and past studies have demonstrated that devices with similar functionality will be needed to support lunar outpost operations. Lunar payloads include: a) prepackaged hardware and supplies which must be unloaded from landers and then accurately located at their operational site, b) sensor packages used for periodic inspection of landers, habitat surfaces, etc., and c) local materials such as regolith which require grading, excavation and placement. Although several designs have been developed for Earth based applications, these devices lack unique design characteristics necessary for transport to and use on the harsh lunar surface. These design characteristics include: a) composite components, b) compact packaging for launch, c) simple in-field reconfiguration and repair, and d) support for tele-operated or automated operations. Also, in contrast to Earth-based construction, where special purpose devices dominate a construction site, a lunar outpost will require versatile devices which provide operational benefit from initial construction through sustained operations. This paper will detail the design of a unique, high performance, versatile lifting device designed for operations on the lunar surface. The device is called the Lunar Surface Manipulation System to highlight the versatile nature of the device which supports conventional cable suspended crane operations as well as operations usually associated with a manipulator such as precise positioning where the payload is rigidly grappled by a tool attached to the tip of the device. A first generation test-bed to verify design methods and operational procedures is under development at the NASA Langley Research Center and recently completed field tests at Moses Lake Washington. The design relied on non-linear finite element analysis which is shown to correlate favorably with laboratory experiments. A key design objective, reviewed in this paper, is the device s simplicity, resulting from a focus on the minimum set of functions necessary to perform payload offload. Further development of the device has the potential for significant mass savings, with a high performance device incorporating composite elements estimated to have a mass less than 3% of the mass of the maximum lunar payload lifted at the tip. The paper will conclude with future plans for expanding the operational versatility of the device.
On the surface of the moon -and not only during heightened solar activities- the radiation environment As such that crew protection will be required for missions lasting in excess of six months. This study focuses on estimating the optimized crew shielding requirement for lunar surface missions with a nuclear option. Simple, transport-simulation based dose-depth relations of the three (galactic, solar, and fission) radiation sources am employed in a 1-dimensional optimization scheme. The scheme is developed to estimate the total required mass of lunar-regolith separating reactor from crew. The scheme was applied to both solar maximum and minimum conditions. It is shown that savings of up to 30% in regolith mass can be realized. It is argued, however, that inherent variation and uncertainty -mainly in lunar regolith attenuation properties in addition to the radiation quality factor- can easily defeat this and similar optimization schemes.
On the surface of the moon and not only during heightened solar activities the radiation environment is such that crew protection will be required for missions lasting in excess of six months. This study focuses on estimating the optimized crew shielding requirement for lunar surface missions with a nuclear option. Simple, transport-simulation based dose-depth relations of the three radiation sources (galactic, solar, and fission) are employed in a one-dimensional optimization scheme. The scheme is developed to estimate the total required mass of lunar regolith separating reactor from crew. The scheme was applied to both solar maximum and minimum conditions. It is shown that savings of up to 30% in regolith mass can be realized. It is argued, however, that inherent variation and uncertainty mainly in lunar regolith attenuation properties in addition to the radiation quality factor can easily defeat this and similar optimization schemes.
Risk to astronauts due to ionizing radiation exposure is a primary concern for missions beyond Low Earth Orbit (LEO) and will drive mission architecture requirements, mission timelines, and operational practices. For short missions, radiation risk is dominated by the possibility of a large Solar Particle Event (SPE). Longer duration missions have both SPE and Galactic Cosmic Ray (GCR) risks. SPE exposure can contribute significantly toward cancer induction in combination with GCR. As mission duration increases, mitigation strategies must address the combined risks from SPE and GCR exposure. In this paper, full mission exposure assessments were performed for the proposed long duration lunar surface mission scenarios. In order to accomplish these assessments, previously developed radiation shielding models for a proposed lunar habitat and rover were utilized. End-to-End mission exposure assessments were performed by first calculating exposure rates for locations in the habitat, rover, and during Extra-Vehicular Activities (EVA). Subsequently, total mission exposures were evaluated for the proposed timelines. Mission exposure results, assessed in terms of effective dose, are presented for the proposed timelines and recommendations are made for improved astronaut shielding and safer operational practices.
Returning to the moon requires many advances in current space technology. One major aspect of this development is a new exploration spacesuit (xEMU). Taking lessons learned from Apollo era suitsand the Extravehicular Mobility Unit (EMU) used on the International Space Station (ISS), xEMU will have increased mobility, dust mitigation, headspace, glove fit, and life support capabilities. Artemis astronauts in xEMU will complete a far more rigorous Extravehicular Activity (EVA) schedule than Apolloand ISS. Notably, metabolic rates during Apollo lunar EVA tasks were observed to be up to 50% lower than similar tasks performed in a ground analog environment under simulated partial gravity with newer suits. Therefore, understanding the physical demands of lunar surface exploration operations is criticalto ensuring best outcomes operating within the constraints of xEMU and planning for exploration EVA activities. This study utilized the Active Response Gravity Offload System (ARGOS) to simulate the lunar environment and continuously offload subjects to lunar gravity. Two male subjects completed two days of EVAs wearing the pressurized Mark III spacesuit, completing suit fit and mobility checks, as well as simulated lander operations, cable routing, crew rescue, geology, payload relocation, and traverse tasks in an end-to-end EVA (E2E) task block and standalone (SA) task blocks. We recorded continuous values of metabolic rate (MR) and heart rate (HR) to assess physical demand. During the E2E task block, subjects did not rest between tasks to simulate continuous effort from task to task, as in real EVAs. In comparison, subjects had a 5-minute break after each SA task block to allow for the metabolic rate and heart rate to return to baseline.MR values were categorized as low (≤ 700 BTU/hr), medium (700-1000 BTU/HR), and high (≥ 1000 BTU/hr), while HR values were categorized as low (≤150) and high (>150). During the 16 tasks in the E2E block, subjects averaged low MR in 6% of tasks, medium MR in 47% of tasks, and high MR in 47% of tasks. While MR was consistent between subjects, Subject 1 averaged low HR for 100% of these tasks, while Subject 2 averaged low HR in 44% of tasks. During the 23 tasks in the SA task blocks, subjects averaged low MR in 26% of tasks, medium MR in 52% of tasks, and high MR in 22% of tasks. Again, HR was different between subjects, with subject 1 averaging low HR in 100% of these tasks while subject 2 averaged low HR in 70%. Across all tasks in this study, subjects reached maximum MR and HR values during a 500m traverse at 30% grade in the E2E block (subject 1: 1747 BTU/hr, 150 BPM; subject 2: 1656 BTU/hr, 177 BPM).Understanding the physical demand to complete exploration EVA tasks will be instrumental to the future success of exploration spacesuit designs and missions. Further work in this study will be needed to characterize MR during exploration EVA tasks, including expanding the subject pool and testing new suit designs.