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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRSDate not supplied

Lunar Polar Exploration with Beamed Powered Rovers

Use of a laser to transmit power to a photovoltaic array has been proposed many times, including significant work done at NASA Glenn during the 1990s, but until recently the technology has lagged behind the ambitious requirements. The current NASA objective of lunar polar exploration provides the need, and evolution of higher-power and more efficient lasers provides the opportunity. Exploration of the ice-bearing craters near the lunar poles, where complete absence of sunlight precludes solar power, have been identified as a significant technology challenge for NASA’s future exploration. An approach to solve this is to use a laser to send power from the illuminated crater rim to a photovoltaic receiver on a rover inside the permanently dark region. A conceptual design was done of a prototype laser power system to be included on a proposed flight demonstration of the Kilopower space reactor. For the design, the laser transmitter is mounted on a small rover capable of moving to a location in line of sight of the receiving rover, e.g., on a crater rim with a view into the permanently dark region to be explored. A 250-watt laser diode bar transmits power at 808 nm, using a 10.5 cm optical beam director. The beam is received by a GaAs solar array mounted on the exploring rover, where it is converted into electrical power at ~50% optical to electrical efficiency. For the flight demonstration, 50 meters of laser transmission was required. The design showed a total laser mass of 7.8 kg is capable of producing the beam needed, not including the thermal control system. The demonstration design demonstrates 50-m transmission, but it would be valuable to have longer point-to-point beaming on the moon. Long beam paths require higher coherence than the diode laser bars of the demonstration system. The development of high-efficiency diode-pumped fiber lasers meets this technology need: and diode-pumped fiber lasers using the Er/Yb system can be purchased commercially with overall conversion efficiency of greater than 50% at wavelength 1.06 micrometers. Two technologies for a photovoltaic converter for this wavelength are the InGaAs photovoltaic cell, using technology developed for multi-junction space solar cells, or newly-developed high-quantum efficiency silicon cells. The next step to mature the technology would be a lunar flight demonstration. In the future, this has the potential to enhance and enable future human exploration of the moon, harvesting and utilizing the ice resources of these permanently-shadowed craters.

Geoffrey A Landis↗
NASA NTRS2020

Results of the KRUSTY Nuclear System Test

The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kW(thermal) Kilopower space reactor. This paper presents results from the KRUSTY nuclear system test, which operated the power system at various temperatures and power levels for 28 consecutive hours. The testing showed that the system operated as expected and that the reactor is highly tolerant of possible failure conditions and transients. The key feature demonstrated was the ability of the reactor to load-follow the demand of the power conversion system. The thermal power of the test ranged from 1.5 to 5.0 kW(thermal), with a fuel temperature up to 880°C. Each 80-W(electric)–rated Stirling converter produced ~90 W(electric) at a component efficiency of ~35% and an overall system efficiency of ~25%.

David I. Poston↗
NASA NTRS2020

Results of the KRUSTY Warm Critical Experiments

The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kW(thermal) Kilopower space reactor. This paper presents results from the KRUSTY warm critical experiments, which were completed prior to the final system test. The first set of criticals comprised cold or zero-power criticals; i.e., the core was not heated by fission power. These were followed by three warm criticals, where fission power heated the core to 200°C, 300°C, and 450°C, respectively. These criticals provided the data, confidence, and regulatory framework that were needed to proceed with the KRUSTY nuclear system test. The criticals also provided valuable data for the benchmarking of codes applicable to all nuclear systems. Finally, a comparison of KRUSTY results to pretest predictions is provided, and overall, the models matched the experimental results very closely.

David I. Poston↗
NASA NTRSDate not supplied

Space Nuclear Propulsion for Deep Space Science Missions

The use of nuclear thermal propulsion (NTP) 1 and nuclear electric propulsion (NEP) 2 systems on deep space science missions to the outer planets and into the interstellar medium 3 can yield significant spacecraft system and mission performance benefits and improvements relative to the use of conventional chemical propulsion systems. Several recent and ongoing programs are developing the technologies and systems required to realize a near-term deep space nuclear propulsion capability. NTP provides improved propulsion efficiencies compared to chemical propulsion, while also providing substantial thrust. This combination of high thrust and increased specific impulse (I_sp) provides high acceleration and extended thrusting periods, enabling greatly reduced trip-times on certain types of missions compared to various propulsive alternatives. For examples, compared to a baseline mission using chemical propulsion, NTP-powered missions to Jupiter or Uranus could deliver approximately 2.4-3.6 times more payload (in the case of Jupiter, the payload delivery is significantly larger than the Juno spacecraft). In this comparison, the higher end of the payload advantage is obtained when the trip time is held equal for the NTP-powered vehicle and a vehicle using a chemical propulsion departure stage. NTP systems are presently under development by multiple government agencies. NASA’s Space Nuclear Propulsion (SNP) project aims to demonstrate a hydrogen-fed NTP engine at 900 s specific impulse (I_sp) and approximately 10-15 klb_f of thrust. DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program is targeting a demonstration of an NTP system in the cislunar space between the Earth and the Moon. An appropriately phased development plan that applies the development of the reactor technology for an NTP engine in this performance class and leverages mature, existing liquid rocket component hardware provides a path to a lower cost propulsion system that can be realized on a shorter development schedule. NEP, with high Isp in the 2,000-8,000 s range, can also provide advantages over chemical propulsion, including a much greater payload delivery mass and the flexibility for planners to trade between delivered mass and a wider window of mission trajectory options. Electric propulsion (EP) systems have demonstrated great utility, performing notably on the Dawn mission to enable rendezvous and orbital insertion at two separate bodies, Vesta and Ceres. An NEP-powered vehicle would have a similar capability to visit multiple bodies, loitering at each before moving to the next. A 10 kW_e NEP system provides a power- rich environment on the spacecraft that is simply not possible using present radioisotope power systems, giving mission planners more scientific instrument and communication hardware options. Several programs and projects are presently developing NEP systems and subsystems in the 10 kW_e power range, leveraging past reactor work and recent nuclear power generation risk-reduction demonstration activities such as the Demonstration Using Flattop Fission (DUFF) and the Kilopower Reactor Using Stirling TechnologY (KRUSTY). The goal of the Air Force Research Laboratory’s Joint Energy Technology Supplying On-Orbit Nuclear Power (JETSON) program is an in-space demonstration vehicle that has a 10 kW_e -class fission power source. These past and present efforts can be combined with the ongoing development of 10 kW_e -class electric propulsion systems (notably the NEXT-C ion thruster or the Hall-effect thrusters for Power and Propulsion Element of the Lunar Gateway) to provide a pathway to a low-cost, reliable NEP system for deep space science application.

Kurt A. Polzin↗
NASA NTRSDate not supplied

Space Nuclear Propulsion for Deep Space Science Missions

The use of nuclear thermal propulsion (NTP) 1 and nuclear electric propulsion (NEP) 2 systems on deep space science missions to the outer planets and into the interstellar medium 3 can yield significant spacecraft system and mission performance benefits and improvements relative to the use of conventional chemical propulsion systems. Several recent and ongoing programs are developing the technologies and systems required to realize a near-term deep space nuclear propulsion capability. NTP provides improved propulsion efficiencies compared to chemical propulsion, while also providing substantial thrust. This combination of high thrust and increased specific impulse (I_sp) provides high acceleration and extended thrusting periods, enabling greatly reduced trip-times on certain types of missions compared to various propulsive alternatives. For examples, compared to a baseline mission using chemical propulsion, NTP-powered missions to Jupiter or Uranus could deliver approximately 2.4-3.6 times more payload (in the case of Jupiter, the payload delivery is significantly larger than the Juno spacecraft). In this comparison, the higher end of the payload advantage is obtained when the trip time is held equal for the NTP-powered vehicle and a vehicle using a chemical propulsion departure stage. NTP systems are presently under development by multiple government agencies. NASA’s Space Nuclear Propulsion (SNP) project aims to demonstrate a hydrogen-fed NTP engine at 900 s specific impulse (I_sp) and approximately 10-15 klb_f of thrust. DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program is targeting a demonstration of an NTP system in the cislunar space between the Earth and the Moon. An appropriately phased development plan that applies the development of the reactor technology for an NTP engine in this performance class and leverages mature, existing liquid rocket component hardware provides a path to a lower cost propulsion system that can be realized on a shorter development schedule. NEP, with high Isp in the 2,000-8,000 s range, can also provide advantages over chemical propulsion, including a much greater payload delivery mass and the flexibility for planners to trade between delivered mass and a wider window of mission trajectory options. Electric propulsion (EP) systems have demonstrated great utility, performing notably on the Dawn mission to enable rendezvous and orbital insertion at two separate bodies, Vesta and Ceres. An NEP-powered vehicle would have a similar capability to visit multiple bodies, loitering at each before moving to the next. A 10 kW_e NEP system provides a power- rich environment on the spacecraft that is simply not possible using present radioisotope power systems, giving mission planners more scientific instrument and communication hardware options. Several programs and projects are presently developing NEP systems and subsystems in the 10 kW_e power range, leveraging past reactor work and recent nuclear power generation risk-reduction demonstration activities such as the Demonstration Using Flattop Fission (DUFF) and the Kilopower Reactor Using Stirling TechnologY (KRUSTY). The goal of the Air Force Research Laboratory’s Joint Energy Technology Supplying On-Orbit Nuclear Power (JETSON) program is an in-space demonstration vehicle that has a 10 kW_e -class fission power source. These past and present efforts can be combined with the ongoing development of 10 kW_e -class electric propulsion systems (notably the NEXT-C ion thruster or the Hall-effect thrusters for Power and Propulsion Element of the Lunar Gateway) to provide a pathway to a low-cost, reliable NEP system for deep space science application.

Kurt A. Polzin↗
NASA NTRSDate not supplied

Consolidation of A Sodium Heat Pipe and Stirling Engine for Fission Surface Power

The Consolidated Heat Pipe (CHP) is a new design in which a sodium heat pipe is welded directly to the hot end of the Stirling engine to deliver thermal power more efficiently. The new integrated interface aims to reduce the large temperature drop (about 120 °C) that was measured across the bolted clamp joint between the Stirling engine and the heat pipes during the Kilopower Reactor Using Stirling TechnologY (KRUSTY) test from 2018. Initial testing and characterization of the CHP was performed in ambient air at the NASA Glenn Research Center (GRC). In the test, the heat pipe evaporator section was heated with a tube furnace. The thermal power was then transported to the Stirling engine integrated with a linear alternator that produced electrical power. The CHP has been tested at a hot end temperature ranging from 600 °C - 800 °C and a variety of other Stirling engine parameters (cold end temperature, piston amplitude and pressure). The results show that the temperature drop between the Stirling engine and the heat pipe has been reduced to 2°C - 4 °C. An overall temperature drop of 20 °C – 60 °C was also noted within the heat pipe depending on the combination of parameters mentioned above. Overall, it has been shown that the new Consolidated Heat Pipe design significantly improved the thermal interface to the Stirling engine.

Consolidated↗
NASA NTRSDate not supplied

Consolidation of A Sodium Heat Pipe and Stirling Engine for Fission Surface Power

The Consolidated Heat Pipe (CHP) is a new design in which a sodium heat pipe is welded directly to the hot end of the Stirling engine to deliver thermal power more efficiently. The new integrated interface aims to reduce the large temperature drop (about 120 °C) that was measured across the bolted clamp joint between the Stirling engine and the heat pipes during the Kilopower Reactor Using Stirling TechnologY (KRUSTY) test from 20181. Initial testing and characterization of the CHP was performed in ambient air at the NASA Glenn Research Center (GRC). In the test, the heat pipe evaporator section was heated with a tube furnace. The thermal power was then transported to the Stirling engine integrated with a linear alternator that produced electrical power. The CHP has been tested at a hot end temperature ranging from 600 °C - 800 °C and a variety of other Stirling engine parameters (cold end temperature, piston amplitude and pressure). The results show that the temperature drop between the Stirling engine and the heat pipe has been reduced to 2°C - 4 °C. An overall temperature drop of 20 °C – 60 °C was also noted within the heat pipe depending on the combination of parameters mentioned above. Overall, it has been shown that the new Consolidated Heat Pipe design significantly improved the thermal interface to the Stirling engine.

Consolidated↗
NASA NTRSDate not supplied

Current Status of NASA's Fission Surface Power Project

Small nuclear fission systems are powerful and could enable robust space operations for planetary habitation and exploration. On Earth, unless disrupted by storms or grid problems, electrical power for most people is no further than an outlet away. However, the solar system does not provide such easy access to electricity as we know it. Astronauts could take advantage of a reliable power supply to explore both the Moon and Mars. The system will need to be lightweight and capable of running regardless of its location, the weather, or available sunlight and other natural resources. NASA’s Fission Surface Power (FSP) project expands on the efforts of the agency’s Kilopower project, which ended in 2018. Currently, NASA is working with the US Department of Energy and industry to design a fission power system that would provide at least 40 kilowatts of power – enough to continuously run 30 households for ten years. A future lunar demonstration will pave the way for sustainable operations and even base camps on the Moon and Mars. This manuscript will showcase the current state of the FSP project, technical goals and accomplishments, future plans, and how this technology paves the way for exciting future applications.

Nuclear↗
NASA NTRSDate not supplied

Vacuum Operation of Consolidated Heat Pipe (CHP) for Fission Surface Power

Consolidated Heat Pipe (CHP) is a new technology that enables direct thermal power delivery to the hot-end of a Stirling engine using a heat pipe--a two phase passive heat transfer device. CHP was developed after the efforts of the Kilopower Using Stirling TechnologY (KRUSTY) test where a heat pipe was used to deliver thermal power from a fission-basedreactor to a Stirling engine to produce 1 kWe of useable electrical power in 2018. Large thermal losses were noted during the KRUSTY test where a temperature drop of 145 °C was measured between the heat pipe’s condenser and the engine’s hot-end. The Consolidated Heat Pipe was designed to address and mitigate this temperature loss. CHP was designed, built and tested at the Glenn Research Center (GRC). The initial test was performed in ambient air conditions, and the results were presented in “Consolidation of a Sodium Heat Pipe and Stirling Engine for Fission Surface Power” at the Thermal Fluids Analysis Workshop in 2023. Researchers at GRC have tested this technology again in a vacuum environment in 2024. Results show that the heat pipe and the hot-end of the Stirling engine are isothermal with a minimal temperature differential of approximately 2.5 °C in varying operational states. The Consolidated Heat Pipe technology has proven to be an efficient way of delivering thermal power directly to Stirling engines.

Greeta J Thaikattil↗
NASA NTRS2019

Compass Final Report: Europa Tunnelbot

The Compass Final Report: Europa Tunnelbot, is a summary of three Compass concurrent engineering team designs for penetrating the ice of Europa and reaching the ocean, while sampling for biomarkers and communicating back to the surface. These conceptual designs, while providing complete conceptual layouts for these penetrators, or 'Tunnelbots' along with the associated communication 'Repeaters' primarily focused on the power and thermal systems needed for these devices. Trades for these systems will provide advantages and challenges for each option. These results will be used to guide power technology development.

probe↗