A one slide presentation/poster on Dynamic RPS development and potential utilization

Hickman, M.

Oriti, S.

Wilson, S.

Zakrajsek, J.

NASA Technical Reports Server

National Aeronautics and
Space Administation
S. Oriti, S. Wilson, M. Hickman, J. Zakrejsek   |  Salvatore.M.Oriti@nasa.gov  |  (216) 433-2066  |  NASA Glenn Research Center, Cleveland, OH 44135
Dynamic Radioisotope Power Systems Development and Potential First 
Mission Utilization
Dynamic power conversion offers the potential to significantly enhance Radioisotope Power System (RPS) performance.  Potential improvements include 
higher conversion efficiency (more power per kg of Pu-238 fuel and less waste heat), low or zero degradation beyond fuel decay, and thus higher end-of-mis-
sion power.  Degradation-free life of Stirling-cycle conversion has been demonstrated on the time scales required by several missions.
ABSTRACT
•  Stirling, Brayton, Rankine, Ericsson are suitable for space applications
•  Conversion efficiencies demonstrated up to 40%
•  Non-contacting bearings and seals (enables long-life continuous operation)
•  Zero degradation via elimination of wear mechanisms
•  Macroscopic engineering challenges (high-temp materials, high-cycle fatigue)
DYNAMIC POWER CONVERSION RECENT CONVERTOR DESIGNS
PATH TO FLIGHT DEVELOPMENT
•  Derived from Surrogate Mission Team input
•  Encompasses wide range of potential Planetary Science Missions
CONVERTOR PERFORMANCE GOALS
ADVANCED STIRLING RADIOISOTOPE
GENERATOR (ASRG)
Development Timeframe
Heat Source
Power
Efficiency
Conversion Technology
Specific Power
2006-2013
2 GPHS
140 We (DC)
28%
Free-piston Stirling
4.4 We/kg
MISSION POTENTIAL
www.nasa.gov
•  Dynamic power conversion has never been flown in space
•  Analogous cryocoolers have operated for up to 20 years in space
•  First mission could be much shorter than outer planets (3 yrs vs 20 yrs)
•  Lunar mission as flight demo is viable
    –  Short cruise time, several destinations that require RPS, short mission duration
•  For short missions, life with margin has been demonstrated at flight-prototype level
•  For long missions (>15 years), demonstrating 2x life is unrealistic
•  First mission must accept some amount of risk, which can be burned down
•  Flightlike Stirling convertors have operated in lab setting for over 12 years (at full temp and power)
•  NASA GRC test article holds all-time world record for heat-engine runtime (>110,000 hrs)
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Design Life
Efficiency
Specific Power
Partial Power
Size
Degradation
Hot-end Temp
Cold-end Temp
Random Vibe
Static Acceleration
Radiation
Robustness
CATEGORY GOAL
20 years
>24% at Tcold>100°C
>20 We/kg
Enables conversion-redundant generators
Enables 200-500 We generator
<0.5%/year
<1000°C
20-175°C
Launch qual (14.6 grms)
20g for 1 minute, 5g for 5 days
300 krad
Ample margins, tolerant of user error
 PHASE DURATION WORK FOCUS TRL
1
2
3
6 months
18 months
12-24 months
Design
Prototype Fabrication
Performance Demonstration
IV&V Test Support
4
4, 6
6
Decision Gate 1
Decision Gate 2
GOAL: Begin Flight Development 
2021
Flexure-bearing Stirling convertor 
continuous operation test article
 Date 2010 2016
 TDC #13 65.4 W 65.4 W
 TDC #14 64.5 W 64.5 W
Example performance data of flexure-bearing 
convertors showing degration-free life
Example cumulative runtimes on flight-
relevant Stirling convertors at NASA GRC
FLEXURE ISOTOPE STIRLING
CONVERTOR (FISC)
American Superconductor, Inc.
Power
Efficiency
Hot-end
Specific Power
70 We
31%
650°C
21 We/kg
TURBO-BRAYTON
CONVERTOR (TBC)
Creare, LLC
Power
Efficiency
Hot-end
Specific Power
355 We
26%
730°C
22 We/kg
SUNPOWER ROBUST
STIRLING CONVERTOR (SRSC)
Sunpower, Inc.
Power
Efficiency
Hot-end
Specific Power
65 We
29%
720°C
33 We/kg
THERMO-ACOUSTIC POWER
CONVERTOR (TAPC)
Northrup Grumman Aerospace Systems
Power
Efficiency
Hot-end
Specific Power
110 We
26%
700°C
19 We/kg
CONVERTORS NOTIONAL GENERATOR DESIGNS
Heat
source
4 GPHS
modules
8x convertors
2x convertors
Heat source
6 GPHS modules
Radiator
Cold End Hot End
Alternator
Cold EndHot End
Altern
ator
Altern
ator
GPHS
 Test  Years of
 Article Operation
 TDC #13 12.6
 TDC #14 12.1
 TDC #15 11.6
 TDC #16 11.6
   Test Years of
   Article Operation
   ASC-0 #3 8.3
   ASC-E3 #4 3.1
   ASC-E3 #6 2.4
   ASC-E3 #9 1.6
   ASC-E3 #8 1.9
   ASC-L 4.0
https://ntrs.nasa.gov/search.jsp?R=20180005489 2019-08-31T15:02:55+00:00Z


Dynamic Radioisotope Power Systems Development and Potential First Mission Utilization

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