Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Review of wearable thermoelectric energy harvesting: From body temperature to electronic systems

A review of nuclear batteries

Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ∼ 6 × 10-9 Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of aP = (8.74 ± 1.33) × 10-10 m/s2. This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.

The Pioneer Anomaly

https://iopscience.iop.org/article/10.7567/JJAP.56.05DA04/pdf

Thermoelectric silicides: A review

Enabling exploration with small radioisotope power systems

A Radioisotope Power System (RPS) generates power by converting the heat released from the nuclear decay of radioactive isotopes, such as Plutonium-238 (Pu-238), into electricity. First used in space by the U.S. in 1961, these devices have enabled some of the most challenging and exciting space missions in history, including the Pioneer and Voyager probes to the outer solar system; the Apollo lunar surface experiments; the Viking landers; the Ulysses polar orbital mission about the Sun; the Galileo mission to Jupiter; the Cassini mission orbiting Saturn; and the recently launched New Horizons mission to Pluto. Radioisotopes have also served as a versatile heat source for moderating equipment thermal environments on these and many other missions, including the Mars exploration rovers, Spirit and Opportunity. The key advantage of RPS is its ability to operate continuously, independent of orientation and distance relative to the Sun. Radioisotope systems are long-lived, rugged, compact, highly reliable, and relatively insensitive to radiation and other environmental effects. As such, they are ideally suited for missions involving long-lived, autonomous operations in the extreme conditions of space and other planetary bodies. This paper reviews the history of RPS for the U.S. space program. It also describes current development of a new Stirling cycle-based generator that will greatly expand the application of nuclear-powered missions in the future.

/pdf/radioisotope-power-a-key-technology-for-deep-space-4eyx91zfo2.pdf

Radioisotope Power: A Key Technology for Deep Space Exploration

Radioisotope Power System (RPS) research and development is vital to a variety of future NASA space science and exploration missions. The objectives of NASA’s current RPS activities are threefold: (1) develop new radioisotope power sources for missions that would launch by the end of the decade; (2) advance promising power conversion technologies to increase the specific power and performance of future RPS units; and (3) assess and facilitate the use of advanced RPS technologies for new mission applications. The program consists of two flight unit development projects, a set of 10 competitively‐selected research and development efforts in power conversion technology, focused research tasks on thermoelectric and Stirling energy conversion, and system analyses to support selection of technologies and evaluation of RPS for promising mission applications. This paper describes the content of the program, and discusses its future direction.

NASA’s Program for Radioisotope Power System Research and Development

The superior energy density of antimatter annihilation has often been pointed to as the ultimate source of energy for propulsion. However, the limited capacity and very low efficiency of present-day antiproton production methods suggest that antimatter may be too costly to consider for near-term propulsion applications. We address this issue by assessing the antimatter requirements for six different types of propulsion concepts, including two in which antiprotons are used to drive energy release from combined fission/fusion. These requirements are compared against the capacity of both the current antimatter production infrastructure and the improved capabilities that could exist within the early part of next century. Results show that although it may be impractical to consider systems that rely on antimatter as the sole source of propulsive energy, the requirements for propulsion based on antimatter-assisted fission/fusion do fall within projected near-term production capabilities. In fact, a new facility designed solely for antiproton production but based on existing technology could feasibly support interstellar precursor missions and omniplanetary spaceflight with antimatter costs ranging up to $6.4 million per mission.

https://ntrs.nasa.gov/api/citations/19990110316/downloads/19990110316.pdf

Antimatter Requirements and Energy Costs for Near-Term Propulsion Applications

An analytical model called FILL is presented which represents the first step in attaining the capability for no-vent fill of cryogens in space. The model's analytical structure is described, including the equations used to calculate transient thermodynamic behavior in different regions of the tank. The code predictions are compared with data from recent no-vent fill ground tests using Freon-114. The results are used to validate the FILL model to evaluate the viability of universal submerged jet theory in predicting system-level condensation effects.

George R. Schmidt

Papers

Enabling exploration with small radioisotope power systems

Radioisotope Power: A Key Technology for Deep Space Exploration

NASA’s Program for Radioisotope Power System Research and Development

Antimatter Requirements and Energy Costs for Near-Term Propulsion Applications

Analytical modeling of no-vent fill process