Robert L. Cataldo

Status of Brayton Cycle Power Conversion Development at NASA GRC

The NASA Glenn Research Center is pursuing the development of Brayton cycle power conversion for various NASA initiatives. Brayton cycle power systems offer numerous advantages for space power generation including high efficiency, long life, high maturity, and broad salability. Candidate mission applications include surface rovers and bases, advanced propulsion vehicles, and earth orbiting satellites. A key advantage is the ability for Brayton converters to span the wide range of power demands of future missions from several kilowatts to multi-megawatts using either solar, isotope, or reactor heat sources. Brayton technology has been under development by NASA since the early 1960’s resulting in engine prototypes in the 2 to 15 kW-class that have demonstrated conversion efficiency of almost 30% and cumulative operation in excess of 40,000 hours. Present efforts at GRC are focusing on a 2 kW testbed as a proving ground for future component advances and operational strategies, and a 25 kW engine design as a ...

Nuclear power systems for the First Lunar Outpost

A recent study effort at NASA has developed a preliminary reference mission description for a human return to the Moon by the end of this decade. The First Lunar Outpost (FLO) would provide the framework for establishing a permanent human presence on the Moon and a necessary step toward eventual piloted trips to Mars. The primary objectives of FLO are to sustain a crew of four on the lunar surface for 45 days during which local roving, surface science, and demonstration‐level resource extraction would be accomplished. Power systems capable of meeting the diverse requirements of FLO are a significant engineering challenge. Power requirements range from 10’s of watts for small science packages to 10’s of kilowatts for the crew habitat. The guidelines imposed on power systems include that they be lightweight, easily deployable, and cost efficient. Nuclear systems such as radioisotope thermoelectric generators (RTGs), dynamic isotope power systems (DIPS), and small reactor power systems offer distinct advanta...

MASER: A Mars meteorology and seismology mini-network mission concept enabled by Milliwatt-RPS

A design reference mission (MASER - Meteorology and Seismology Enabled by Radioisotopes) for a Mars mini-network is presented. Four hard landers using parachutes and crushable impact attenuators would be deployed in the polar plains north of the Tharsis bulge to perform seismic and meteorological measurements throughout a Martian year (including the dark winter). Operation throughout the polar winter is only possible through the use of a power subsystem that would rely upon six Radioisotope Heater Units (RHUs), providing ~240mWe.

Development of a robust space power system decision model

NASA continues to evaluate power systems to support human exploration of the Moon and Mars. The system(s) would address all power needs of surface bases and on-board power for space transfer vehicles. Prior studies have examined both solar and nuclear-based alternatives with respect to individual issues such as sizing or cost. What has not been addressed is a comprehensive look at the risks and benefits of the options that could serve as the analytical framework to support a system choice that best serves the needs of the exploration program. This paper describes the SAIC developed Space Power System Decision Model, which uses a formal Two-step Analytical Hierarchy Process (TAHP) methodology that is used in the decision-making process to clearly distinguish candidate power systems in terms of benefits, safety, and risk. TAHP is a decision making process based on the Analytical Hierarchy Process, which employs a hierarchic approach of structuring decision factors by weights, and relatively ranks system des...

Spacecraft Power System Considerations for the Far Reaches of the Solar System

Reliable and ready power is vital to any spacecraft. Currently, two practical options exist for providing that power, harvesting energy from the Sun or heat generated from a nuclear source. Solar photovoltaics is an excellent way to convert the Sun’s energy to electricity within the inner solar system, Mars and perhaps Jupiter if the mission is designed accordingly. However, long term science investigations to the outer planets, which pose a harsh, dark and cold environment, are well served by nuclear based technology such as a radioisotope power system that would provide not only constant Sun-independent power, but also as important, heat generated by the long-term natural radioactive decay process of plutonium-238. This technology can truly enable missions to the outer solar system and beyond otherwise not achievable.

The challenge of space nuclear propulsion and power systems reliability

In October of 2002, The Power and Propulsion Office and The Risk Management Office of NASA Glenn Research Center in Cleveland, Ohio began developing the reliability, availability, and maintainability (RAM) engineering approach for the Space Nuclear Propulsion and Power Systems Project. The objective of the Space Nuclear Power and Propulsion Project is to provide safe and reliable propulsion and power systems for planetary missions. The safety of the crew, ground personnel, and the public has to be the highest priority of the RAM engineering approach for nuclear powered space systems. The project will require a top level reliability goal for substantial mission success in the range from 0.95 to 0.98. In addition, the probability of safe operation without loss of crew, vehicle, or danger to the public, cannot be less than 0.9999. The achievement of these operational goals will require the combined application of many RAM engineering techniques. These include: advanced reliability, availability, and maintainability analysis, probabilistic risk assessment that includes hardware, software, and human induced faults, accelerated life testing, parts stress analysis, and selective end to end sub-system testing. Design strategy must involve the selection of parts and materials specifically to withstand the stresses of prolonged operation in the space and planetary environments with a wide design margin. Interplanetary distances and resulting signal time delay drive the need for autonomous control of major system functions including redundancy management.