Hamley, John A.

Zakrajsek, J.

NASA Technical Reports Server

RADIOISOTOPE POWER SYSTEMS PROGRAM
STATUS AND EXPECTATIONS
J. ZAKRAJSEK
Presented by:
John A. Hamley, RPS Program Manager
July, 2017
www.nasa.gov
https://ntrs.nasa.gov/search.jsp?R=20170008806 2019-08-29T23:09:21+00:00Z
Agenda
• Program Background & Changes
• RPS Related NEPA/Launch Approval Processes
• Next Generation RTG Study
• Dynamic RPS Status
• Constant Rate Production
• Q&A
2
Radioisotope Power Systems
• Radioisotope Power Systems (RPS) are ideally 
suited for missions that need autonomous, 
long-duration power
– Proven record of operation in the most extreme 
cold, dusty, dark, and high-radiation environments, 
both in space and on planetary surfaces. 
• RPS provide long-lived power solutions for 
future Planetary Decadal Science missions 
– Mars 2020 (sample return precursor)
– Uranus Orbiter/Probe
– New Frontiers (Ocean-Worlds, Saturn, Lunar) 
• RPS technologies offer potential to serve a 
wide range of missions from Small-sat/Cube-
sat to Flagship-class Science (1-1000 We) 
– Thermoelectric (Pb-Te/TAGS; Skutterudite) 
– Dynamic (Stirling)
– Radioisotope Heater Units 
• RPS Program has an established relationship 
with DOE and has processes in place to work 
effectively
3
RPS have successfully powered NASA Missions for over 40 years and continues 
to serve the needs of NASA in its exploration of the Solar System  
Programmatic Change
• Several changes have occurred in the Program 
over the last three years
– DOE MOU for RPS has been renegotiated
• Plays to strength of agencies
• Allows for the formulation of Integrated Project Teams (IPTs) for 
flight system development
– RPS Program now includes DOE activities for Pu238 
production and processing into flight fuel forms
– Nuclear Launch Safety and NEPA activities managed by 
the Program Office for Program Executives
– The Technology Advancement Project has been divided 
into two projects
• Thermoelectric Technology Development (JPL)
• Stirling Cycle Technology Development (GRC)
– Support Mars 2020 program
4
NASA/DOE Memorandum of Understanding
• DOE MOU for RPS has been renegotiated
– Plays to strength of agencies
– Allows for the formulation of Integrated Project Teams (IPTs) 
for flight system development
5
23 May 2017
RPS Objective and Level I Requirements
• Program Objective
– Ensure the availability of RPS for the exploration of the solar 
system in environments where conventional solar or 
chemical power generation is impractical or impossible. 
• Program Level I Requirements
– PCA-1:  The RPS Program shall procure RPS for SMD missions.
– PCA-2:  The RPS Program shall sustain the capability to 
conduct RPS missions.
– PCA-3:  The RPS Program shall develop RPS technologies for 
insertion into flight systems. 
– PCA-4:  The RPS Program shall manage the nuclear launch 
safety approval process for RPS.
6
RPS
Production 
Operations*
Operations 
and Analysis
Pu-238 
Supply 
Project
Un-fueled 
RPS 
Production
Mars Rover 2020 
Mission Support*
Future Systems 
Development* RPS Program
Program 
Control
Systems
Formulation 
and Mission 
Integration
DOE Insight
Nuclear
Launch 
Coordination
Communications
Thermoelectric 
Technology 
Development
Stirling Cycle 
Technology 
Development
DOE
NASA
* NASA-funded DOE activities with unique Inter Agency Agreement
Program With DOE Content
7
Nuclear Launch Coordination
• Management of activities which support NASA NEPA and NPR 
8713.5 compliance and the nuclear safety process compliant 
with Presidential Directive/NSC-25 (PD/NSC-25)
• The RPS Program now coordinates this process on behalf of the 
Mission Program Executive
– NEPA compliance
– EIS/EA completion
– Mission databooks
– Launch vehicle data books
– Systems simulations
– Systems and vehicle
component
destructive tests as required
– Accident investigations 
and analysis as required
– Site environmental sensors
– Risk communications
– Analysis of alternate isotopes
8
RPS Program – Coordination Role
• Coordination with 
– Mission Program Executive and Manager
– NASA Headquarters NEPA lead
– NASA Office of Safety and Mission Assurance
– DOE
– INSRP and processes
• Management of all NASA-executed activities in support of the 
launch of RPS, RHUs or nuclear materials on a mission
• Support of all Announcements of Opportunity or directed 
mission activities when RPS, RHUs or nuclear material will be 
present.
• Multi-Mission support activities, including but not limited to the 
production of launch vehicle databooks.
9
Next Gen RTG- Key Considerations
• End of mission power
– Degradation rate
• Integration & Operations
– Number of generators per mission 4 
or less 
• Risks to get to a generator
– TE TRL maturity
– Generator design heritage
• PSD mission focus in next 10 years 
(as best aware)
– Flyby and orbit OP
– Land and rove OW
• Balance of RPS Program
– MMRTG
– Dynamic
– Other
10
Next Gen RTG Future Characteristics
• System designed to operate in vacuum
• System designed to be modular
– Requires process for modular qualification
• System (16 GPHS) provides at least 400 We at BOL with a goal 
of 500 We
• System (16 GPHS) mass is 60 kg or less
• System degradation rate, including fuel degradation, is 1.9%
– To be rewritten in terms of EODL power
• System to be designed to be upgraded with new TCs as 
technology matures
11
Stirling Cycle Technology Development Project
• Reassess Stirling/Dynamic Power Generation 
Technology industrial capability
– ROSES NRA process
– End goal is 200-500W flight system
– First flight opportunity 2028
– Phased approach
• SOA assessment
• Requirements definition
• Prototype system
• Flight contract with DOE
• Maintain GRC In-House
capability
– Stirling Lab (B. 301) RSIL (B.333)
– Fundamental component/systems 
research
– Spacecraft Integration
12
Why a DRPS?
Dynamic Power Systems provide benefits 
that enable spacecraft to meet NASA 
objectives and PSD science objectives 
– Destination flexibility 
– Fuel efficiency/ Less Fuel
– Less Waste Heat
– Higher Potential Power at EODL
– Path to higher power systems (Benefits to 
SMD and HEO)
13
Dynamic Power Technology Objective
In the context of developing a 200-500 We RPS 
determine the development readiness and risk 
associated with dynamic power conversion 
technologies
• Key technology evaluation characteristics
– Reliability
– Robustness
– Manufacturability
– Life-cycle and sustainability costs 
– Performance
14
• Dynamic Power Converters for RPS Contracts
–One signed with ITC Start July 3, 2017
–One contracts ready to be finalized and signed
–Two contracts in negotiation; anticipating July 
contract award
• Dynamic Power Conversion for RPS Contracts
–Kickoff meetings with contractors, Jul. 2017
–Phase 1 convertor designs, Jan. 2018
–Phase 2 demo convertors, Sep. 2019
–NASA prototype convertor test reports, Sep. 2020
–NASA recommendation report, Dec. 2020
RPS Dynamic Power Conversion 
15
DOE RPS Supply Chain
16 16
RPS Program Operations – Transition to 
Constant Rate Production
• DOE and NASA have agreed to transition to a Constant 
Rate Production model across the supply chain to better 
meet NASA mission needs
– Established annual average production rates for Pu-238 and 
fuel clads, across the DOE RPS supply chain 
– Transitioning Pu-238 Supply from a project-based approach 
to a campaign model
– Accelerating research to optimize the supply chain 
– Improving integration of RPS activities across the DOE 
complex to inform future investment decisions
17 17
Constant Rate Production Benefits
• Leverages DOE standard campaign model providing 
flexibility for NASA missions
– New irradiation target designs
– Equipment investments for fuel clad manufacturing
– Utilization studies for the Advanced Test Reactor
– Evaluation of new technology
• Maintains qualified work force
• Reduces mission costs 
– New Frontiers initial estimates reduced approximately 25%
• Provides more predictable operation pace that level-loads 
resources
18
Pu238 Production
• Objective: Restart domestic production of Heat Source 
Pu238 (HS-PuO2)with a planned rate of 1.5 kg/yr at the 
end of FY23
• First new US Pu-238 production since the late 1980s 
– ~ 100 gm total HS-PuO2 has been produced
– Small samples have been shipped 
to LANL to compare analytical results
– Plan to include some new material in 
Mars 2020 fuel load
• Target production already well 
underway for second demonstration
– Demonstrate larger batch sizes
– Implement process improvements
• Target Irradiation in the High Flux 
Isotope Reactor (HFIR) at ORNL 
continues
• Currently investigating options for
additional target irradiation at the
Advanced Test Reactor (ATR) at INL
19
End State Vision - Isotope Production 
• By fiscal year 2021, add additional irradiation 
capability at the Advanced Test Reactor (ATR) for 
redundancy
• By fiscal year 2025, maintain average production rate 
of  1.5 kg/y with surge capacity to ~2.5 kg/y (if funded)
20
Reflector positions and flux traps can 
be used to irradiate NpO2 at ATR
Advanced Test Reactor (ATR)High Flux Isotope Reactor (HFIR)
Reflector positions can be used 
to irradiate NpO2 in the HFIR
ORNL Processing Capability
20
End State Vision – Fueled Clad 
Manufacturing 
• By fiscal year 2021, maintain 10-15/year constant-rate of 
fueled clads at Los Alamos and shipped to Idaho 
• By fiscal year 2025, completed modernization campaign 
at Los Alamos to improve reliability of critical 
infrastructure and enhance worker safety
21
Aqueous Line
21
End State Vision – Fueling/Testing/Delivery
• By fiscal year 2021, modify storage at INL to reduce 
risk and add scheduling flexibility for fueling RPS
• By fiscal year 2025, implement process to match fuel 
for NASA missions based on heat output, providing 
more flexibility to make adjustments
22
General Purpose Heat Source Module
22
Summary
• RPS Program provides NASA a robust, end-to-end program 
capability
– DOE partnership/sustained capabilities
– DOE systems acquisition (MMRTGs) 
– Mission target driven technology development
– Customer engagement 
• Ongoing capability enhancements
– Infrastructure & Plutonium Supply Project
– Nuclear Launch Coordination
– Systems (eMMRTG)
– Technologies  (thermoelectrics and Stirling)
• Service to Missions
– Operational (Voyager, Cassini, New Horizons, Curiosity)
– Future (Mars 2020, potential NF-4)
23
Over 50 years of RPS Missions
24
27 MISSIONS
46 RPS
100% RPS SUCCESS
http://rps.nasa.gov
rps@nasa.gov


Radioisotope Power Systems Program Status and Expectations

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