AMTEC Module Test Program

Svedberg, Robert C.; Sievers, R.K.; Ivanenok, Joseph F.; Hunt, Thomas K.; Butkiewicz, David A.; Pantolin, Jan E.; Swift, Kim D.; Schüller, Michael; Ryan, M. A.

doi:10.1063/1.2950171

Cited by 6 publications

(5 citation statements)

References 3 publications

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“…In addition, many demanding applications for transparent ceramics, such as missile radomes, have complicated geometries. Thermoplastic extrusion of nanopowders has rarely been studied, likely due to the challenges in obtaining high solids loadings due to the increased surface area interactions between particles in the melt, leading to extremely high viscosities that prevent easy extrusion …”

Section: Introductionmentioning

confidence: 99%

Extrusion of YAG Tubes Shows that Bottom‐up Processing is Not Always Optimal

Taylor

Laine

2013

Adv Funct Materials

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Liquid-feed fl ame spray pyrolysis provides easily dispersed, unaggregated nanopowders with average particle sizes of 20-70 nm depending on the processing conditions. Their chemical compositions can be controlled to ppm levels via control of the initial precursor solution. In this paper, Y 3 Al 5 O 12 composition nanopowders are produced that are atomically mixed but offer a hexagonal crystal structure rather than a YAG structure. Y 2 O 3 and δ -Al 2 O 3 nanopowders are also produced and mixed to evaluate reactive sintering. It is shown that nanopowder/polymer mixtures permit the extrusion of tubes that retain their shape on debindering and sintering to ≥95% theoretical density. More importantly, the sintering behavior of hex-Y 3 Al 5 O 12 is compared with that of tubes formed using 3:5 Y 2 O 3 : δ -Al 2 O 3 mixtures to test the so-called bottom-up paradigm, which suggests that mixing on the fi nest length scales should provide optimal control of sintering rates, fi nal densities, and grain sizes. Instead, it is found that reactive sintering is faster and offers better control of fi nal grain sizes. Dense sintered tubes are translucent, and dimensional uniformity is maintained from extrusion through sintering.

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Section: Introductionmentioning

confidence: 99%

Extrusion of YAG Tubes Shows that Bottom‐up Processing is Not Always Optimal

Taylor

Laine

2013

Adv Funct Materials

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“…(As will later be shown, the generator's specific power is maximized with very thin graphite skins.) Assume that the heat pipe mass ntj P er ufl it length is 1.61 g/cm; that the mass per unit area of the honeycomb is 0.063 g/cm 2 , that of each 0.005" graphite skin is 0.025 g/cm 2 ; that of each bond layer is 0.022 g/cm 2 , so that the areal density /M^ is 0.157 g/cm 2 ; that the volumetric density IMJ of the aluminum skins is 2.77 g/cm 3 ; and that the fin is subjected to quasi-static acceleration of 40 g or 392 m/s 2 normal to its surface. This last assumption was made b ecause previous RTGs [14] were designed and qualification-tested to 40 g, b ut it is quite conservative for the present application, b ecause the RTPV under study is much shorter than the RTGs, and because a quasi-static test may inherently be an overconservative representation of the dynamic launch loads.…”

Section: (Y 0 -?X)zt 0 +4ijzmentioning

confidence: 99%

“…Fortunately, there are a number of advanced conversion systems that may be able to triple the conversion efficiency of present thermoelectric converters. These include the Stirling [1], AMTEC [2], and the thermophotovoltaic (TPV) [3] options. The latter is the basis of the design study described in the present paper.…”

Section: Introductionmentioning

confidence: 99%

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Applicability to an Illustrative Space Mission

Schock¹,

Mukunda²,

Or³

et al. 1994

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The paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator (RTPV), to complement similar studies of Radioisotope Thermoelectric Generators (RTGs) and Stirling Generators (RSGs) previously published by the author. Instead of conducting a generic study, it was decided to focus the design effort by directing it at a specific illustrative space mission, Pluto Fast Flyby (PFF). That mission, under study by JPL, envisages a direct eight-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a post-encounter cruise lasting up to one year.Because of Pluto's long distance from the sun (30-50 A.U.) and the mission's large energy demand, JPL has baselined the use of a radioisotope power system for the PFF spacecraft. RTGs have been tentatively selected, because they have been successfully flown on many space missions, and have demonstrated exceptional reliability and durability. The only reason for exploring the applicability of the far less mature RTPV systems is their potential for much higher conversion efficiencies, which would greatly reduce the mass, and cost of the required radioisotope heat source. Those attributes are particularly important for the PFF mission, which -like all NASA missions under current consideration -is severely mass-and cost-limited.The paper describes the design of an RTPV system consisting of a radioisotope heat source, a thermophotovoltaic converter, and an optimized heat rejection system; and depicts its integration with the PFF spacecraft. It then describes the thermal, electrical, and structural analysis which led to that optimized design, and compares the computed performance of an RTPV system to that of an RTG designed for the same mission. Our analytical results indicated thatwhen fully developed -it could result in a 60% reduction of the heat source's mass, cost, and fuel loading, a 50% reduction of generator mass, a tripling of the power system's specific power, and a quadrupling of its efficiency.The paper concludes by briefly summarizing the RTPV's current technology status and assessing its potential applicability for the PFF mission. For other power systems (e.g. RTGs), demonstrating their flight readiness for a long-term mission is a very time-consuming process. But for the case of the described RTPV design, the paper lists a number of factors, primarily its cold (0 to 10°C) converter temperature, that may greatly reduce the need for long-term tests to demonstrate generator lifetime. In any event, our analytical results suggest that the RTPV generator, when developed by DOE and/or NASA would be quite valuable not only for the Pluto mission but also for other future missions requiring small, long-lived, low-mass generators.

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“…(As will later be shown, the generator's specific power is maximized with very thin graphite skins.) Assume that the heat pipe mass ntj per unit length is 1.61 g/cm; that the mass per unit area of the honeycomb is 0.063 g/cm 2 , that of each 0.005" graphite skin is 0.025 g/cm 2 ; that of each bond layer is 0.022 g/cm 2 , so that the areal density m 2 is 0.157 g/cm 2 ; that the volumetric density m_j of the aluminum skins is 2.77 g/cm 3 ; and that the fin is subjected to quasi-static acceleration of 40 g or 392 m/s 2 normal to its surface. This last assumption was made because previous RTGs [14] were designed and qualification-tested to 40 g, but it is quite conservative for the present application, because the RTPV under study is much shorter than the RTGs, and because a quasi-static test may inherently be an overconservative representation of the dynamic launch loads.…”

Section: Structural Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Application to the Pluto Fast Flyby Mission

Schock¹,

Mukunda²,

Or³

et al. 1994

View full text Add to dashboard Cite

The paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator. Instead of conducting a generic study, it was decided to focus the design effort by directing it at a specific space mission, Pluto Fast Flyby (PFF). That mission, under study by JPL, envisages a direct eight-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a one-year post-encounter cruise.Because of Pluto's long distance from the sun (30-50 A.U.) and the mission's large energy demand, JPL has baselined the use of a radioisotope power system for the PFF spacecraft. The chief advantage of Radioisotope Thermophotovoltaic (RTPV) power systems over current Radioisotope Thermoelectric Generators (RTGs) is their much higher conversion efficiency, which greatly reduces the mass and cost of the required radioisotope heat source. Those attributes are particularly important for the PFF mission, which -like all NASA missions under current consideration -is severely mass-and cost-limited.The paper describes the design of the radioisotope heat source, the thermophotovoltaic converter, and the heat rejection system; and presents the results of the thermal, electrical, and structural analysis and the design optimization of the integrated RTPV system. It briefly summarizes the RTPV system's current technology status, and lists a number of factors that may greatly reduce the need for long-term tests to demonstrate generator lifetime. Our analytical results show very substantial performance improvements over an RTG designed for the same mission, and suggest that the RTPV generator, when developed by DOE and/or NASA would be quite valuable not only for the PFF mission but also for other future missions requiring small, long-lived, low-mass generators.

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AMTEC Module Test Program

Cited by 6 publications

References 3 publications

Extrusion of YAG Tubes Shows that Bottom‐up Processing is Not Always Optimal

Extrusion of YAG Tubes Shows that Bottom‐up Processing is Not Always Optimal

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Applicability to an Illustrative Space Mission

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Application to the Pluto Fast Flyby Mission

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