Developmental Considerations on the Free-Piston Stirling Power Convertor for Use in Space

Schreiber, Jeffrey G.

doi:10.2514/6.2006-4015

Cited by 14 publications

(8 citation statements)

References 26 publications

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“…Each generator consists of many components, but the fundamental parts are as follows: a GPHS module; a heater head that is made of a nickel composed alloy such as Inconel 718; (i.e. materials with a suitable creep life and thermodynamic performance), the heater head like a pressure vessel, where the heat from the GPHS module is either supplied to the thermodynamic cycle; the third crucial composition is an inert working gas such as helium; the fourth part is a power piston; the fifth part consists of two permanent magnet layers, for instance neodymium iron boron (FeNdB) magnets [19,20].…”

Section: Advanced Stirling Radioisotope Power Systemsmentioning

confidence: 99%

Improving the Overall Efficiency of Radioisotope Thermoelectric Generators

Salh¹

2014

aep

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Radioisotope thermoelectric generators (RTG) convert the decay energy of a radioisotope ( 238 Pu) into heat then into electricity. RTGs have been used to power space exploration missions. This review paper studies several crucial features of past and present Static RTGs, for instance the advantages of Static RTGs. In addition it reviews Static RTGs limitations such as the shortage in the amount of 238 Pu in (U.S.A). Furthermore it compares the future Dynamic RTGs with Static RTGs. It indicates the future Dynamic RTGs, which include a thermodynamic cycle, use 2-4 times less amount of 238 Pu. In spite of that, their efficiency is almost 4 times greater than past and present RTGs.

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Section: Advanced Stirling Radioisotope Power Systemsmentioning

confidence: 99%

Improving the Overall Efficiency of Radioisotope Thermoelectric Generators

Salh¹

2014

aep

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“…While cautious measures and practices have been applied to monitor the internal gas environment for any sign of outgassing in a convertor system level (Schreiber, 2007), the objective of this task was to develop systematic and quantitative assessment of the outgassing potential in each organics used in the convertors, and thus to validate their outgassing performance. Sources of outgassing could be (i) trapped gas/volatile, (ii) un-reacted, small molecular-weight chemical species, (iii) reaction and/or degradation by-products, (e.g., thermal or irradiation-induced degradation or chemical reactions).…”

Section: Outgassing Assessmentmentioning

confidence: 99%

Validation of Organics for Advanced Stirling Convertor (ASC)

Shin¹,

Scheiman²,

Cybulski³

et al. 2008

AIP Conference Proceedings

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Organic materials are an essential part of the Advanced Stirling Convertor (ASC) construction as adhesives, potting, wire insulation, lubrication coatings, bobbins, bumpers, insulators, thread lockers. Since a long lifetime of such convertors to be used in the Advanced Stirling Radioisotope Generator (ASRG), sometimes up to 17 years, is required in various space applications such as Mars rovers, deep space missions, and lunar surface power, performance, durability and reliability of those organics should be critically evaluated in every possible material-process-fabricationservice environment relations. The objective of this study was to evaluate, validate, and recommend organics for use in ASCs. Systematic and extensive evaluation methodologies were developed and conducted for various organic materials. The overall efforts dealing with organics materials for the last several years are summarized in the key areas, e.g., process-fabrication optimization, adhesive bonding integrity, outgassing, thermal stability, and durability

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“…With this, the design of components falls under the umbrella of standard engineering challenges for which methods exist to achieve the required life (Ref. 4).…”

Section: Introductionmentioning

confidence: 99%

Dynamic Power Convertor Development for Radioisotope Power Systems at NASA Glenn Research Center

Oriti

Wilson

2018

2018 International Energy Conversion Engineering Conference

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The Thermal Energy Conversion Branch at NASA Glenn Research Center is supporting the development of high-efficiency power convertors for use in radioisotope power systems (RPS). Significant progress was made toward such a system that utilized Stirling conversion during the 2001 to 2015 timeframe. Flight development of the Advanced Stirling Radioisotope Generator (ASRG) was canceled in 2013 by the U.S. Department of Energy (DOE) and NASA Headquarters primarily due to budget constraints, and the Advanced Stirling Convertor (ASC) technology contract was subsequently concluded in 2015. A new chapter of technology development has recently been initiated by the NASA RPS Program. This effort is considering all dynamic power convertor options, such as Stirling and Brayton cycles. Four convertor development contracts supporting this effort were awarded in 2017. The awarded contracts include two free-piston Stirling, one thermoacoustic Stirling, and one turbo-Brayton design. The technology development contracts each consist of up to three phases: design, fabrication, and test. As of May 2018, all contracts have completed the design phase, and each underwent a design review with an independent review board. Three of the contracts are planned to execute the phase 2 option for fabrication. Convertors manifesting from these development efforts will then undergo independent validation and verification (IV and V) at NASA facilities, which will consist of convertor performance and RPS viability demonstrations. Example tests include launch vibration simulation, performance mapping over the environmental temperature range, and static acceleration exposure. In parallel with this renewed development effort, Glenn is still demonstrating free-piston Stirling convertor technology using assets from previous projects. The Stirling Research Laboratory (SRL) is still operating several convertors from previous development projects, which have similarities and relevance to current contract designs. Four of these are flexure-bearing based and another six are gas bearing based. One of the flexure-bearing convertors has accumulated over 110,000 h of operation and holds the current record for maintenance-free heat-engine run time. Another flexure-bearing convertor was recently manually shut down after 105,620 h of operation, then disassembled and inspected. This inspection produced a wealth of information about the effects of this amount of run time on the technology's components. One of the engineering unit flexure-bearing convertors recently underwent a launch simulation vibration test, a static acceleration exposure up to 20 g, and was then placed on extended operation. Among the gas-bearing convertors, the longest running unit has accumulated over 70,000 h of operation. Four high-fidelity gas-bearing convertors from the ASRG project are still operating continuously for which the longest run time has reached 28,000 h.

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Developmental Considerations on the Free-Piston Stirling Power Convertor for Use in Space

Cited by 14 publications

References 26 publications

Improving the Overall Efficiency of Radioisotope Thermoelectric Generators

Improving the Overall Efficiency of Radioisotope Thermoelectric Generators

Validation of Organics for Advanced Stirling Convertor (ASC)

Dynamic Power Convertor Development for Radioisotope Power Systems at NASA Glenn Research Center

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