Donald T. Palac and Lee S. Mason

Glenn Research Center, Cleveland, Ohio

Michael G. Houts

Marshall Space Flight Center, Huntsville, Alabama

Scott Harlow

U.S. Department of Energy, Germantown, Maryland

Fission Surface Power Technology

Development Update

NASA/TM—2011-216976

January 2011

AIAA–2010–8711
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Donald T. Palac and Lee S. Mason

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Marshall Space Flight Center, Huntsville, Alabama

Scott Harlow

U.S. Department of Energy, Germantown, Maryland

Fission Surface Power Technology

Development Update

NASA/TM—2011-216976

January 2011

AIAA–2010–8711

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NASA/TM—2011-216976 1 

Fission Surface Power Technology Development Update 

Donald T. Palac and Lee S. Mason 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Michael G. Houts 

National Aeronautics and Space Administration 

Marshall Space Flight Center 

Huntsville, Alabama 35812 

Scott Harlow 

U.S. Department of Energy 

Germantown, Maryland 20874 

Abstract 

Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and 

places beyond. Nuclear power is an important option, especially for locations in the solar system where 

sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA 

and the Department of Energy are maintaining the option for fission surface power for the Moon and 

Mars by developing and demonstrating technology for a fission surface power system. 

The Fission Surface Power Systems project has focused on subscale component and subsystem 

demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for 

surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power 

conversion, heat rejection, and power management and distribution technologies have validated that the 

fundamental characteristics and performance of these components and subsystems are consistent with a 

Fission Surface Power preliminary reference concept. In addition, subscale versions of a non-nuclear 

reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and 

operated with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the 

viability of establishing system-level performance and characteristics of fission surface power 

technologies without requiring a nuclear reactor. While some component and subsystem testing will 

continue through 2011 and beyond, the results to date provide sufficient confidence to proceed with 

system level technology readiness demonstration. 

To demonstrate the system level readiness of fission surface power in an operationally relevant 

environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power 

Technology Demonstration Unit (TDU) is under development. The TDU will consist of a non-nuclear 

reactor simulator, a sodium-potassium heat transfer loop, a power conversion unit with electrical controls, 

and a heat rejection system with a multi-panel radiator assembly. Testing is planned at the Glenn 

Research Center Vacuum Facility 6 starting in 2012, with vacuum and liquid-nitrogen cold walls to 

provide simulation of operationally relevant environments. A nominal two-year test campaign is planned 

including a Phase 1 reactor simulator and power conversion test followed by a Phase 2 integrated system 

test with radiator panel heat rejection. The testing is expected to demonstrate the readiness and 

availability of fission surface power as a viable power system option for NASA’s exploration needs. In 

addition to surface power, technology development work within this project is also directly applicable to 

in-space fission power and propulsion systems. 
NASA/TM—2011-216976 2 

Nomenclature 

DAS Data Acquisition System 

DOE Department of Energy 

ELS Electric Load Simulator 

FCS Facility Cooling System 

FSP Fission Surface Power 

FSPS Fission Surface Power System 

GRC Glenn Research Center 

HR Heat Rejection 

HRS Heat Rejection System 

HX Heat Exchanger 

I&C Instrumentation and Controls 

IHX Intermediate Heat Exchanger 

INL Idaho National Laboratory 

IP Intermediate Pump 

IVA Intermediate Volume Accumulator 

kg kilogram 

kW kilowatts 

kWe kilowatts (electric) 

kWt kilowatts (thermal) 

LaNL Los Alamos National Laboratory 

LN2 Liquid Nitrogen 

m meter 

MSFC Marshall Space Flight Center 

NaK Sodium/Potassium mixture 

NASA National Aeronautics and Space Administration 

ORNL Oak Ridge National Laboratory 

PC Power Conversion 

PCU Power Conversion Unit 

PMAD Power Management and Distribution 

PP Primary Pump 

PVA Primary Volume Accumulator 

RDU Radiator Demonstration Unit 

rem Roentgen Equivalent Man 

RP Radiator Pump 

RVA Radiator Volume Accumulator 

Rx Reactor 

Rx Sim Reactor Simulator 

SNL Sandia National Laboratory 

TDU Technology Demonstration Unit 

TRL Technology Readiness Level 

yr year 
NASA/TM—2011-216976 3 

Introduction 

The Fission Surface Power Systems (FSPS) project was initiated in 2007 to develop system level 

technology that provides the option for fission surface power for the U.S. Space Exploration Policy. The 

project key goals are to: 

 Develop an FSPS concept that meets surface power requirements at reasonable cost with added 

benefits over competitive options, and that is safe during all mission phases 

 Establish a hardware-based technical foundation for FSPS design concepts and reduce risk 

 Reduce the cost uncertainties for FSPS and establish greater credibility for flight system cost 

estimates 

 Generate the key gate products that would allow Agency decision-makers to consider FSPS as a 

viable option to proceed to flight development 

Key to accomplishment of these goals is demonstration of fission surface power technology at the system 

level in an operationally relevant environment, defined by NASA as Technology Readiness Level 6 

(Ref. 1). 

Initiation of the FSPS project was contingent on successful demonstration that a fission surface power 

system could be developed affordably. In 2007, NASA and DOE performed a rigorous assessment of 

fission surface power cost elements, and approaches to minimize them while meeting expected mission 

requirements (Ref. 2). Key principles of an affordable approach were found to include: (1) selection of 

component performance goals well within envelopes of existing experience and demonstrated capabilities 

where possible; (2) avoidance of component technology development (especially in the reactor) to the 

extent practical; and (3) selection of component and system solutions with lower risk and complexity, 

even at the expense of higher mass. The resultant themes of simplicity, robustness, and conservatism were 

key to an affordable approach to fission surface power (Ref. 3). These findings were applied to 

development of a preliminary FSP concept, which was then used to determine the minimum set of 

component technologies that would require development prior to initiation of a system-level FSP 

technology demonstration. 

From 2008 to 2010, the FSPS project emphasized concept definition and “Pathfinder” technology 

development. Concept definition refined the trade studies and development of a reference concept to 

guide technology development and demonstration. The FSPS reference concept for the lunar surface (with 

applicability to Mars) is shown in Figure 1. The FSP system is defined by four major elements: (1) 

Reactor Module, (2) Power Conversion Module, (3) Heat Rejection Module, and (4) Power Management 

and Distribution (PMAD) Module. The reactor generates the nuclear heat through fission. Thermal power 

is transferred from the reactor to the power conversion and waste heat is transferred from the power 

conversion to the heat rejection. Electrical power generated by the power conversion is processed through 

the PMAD to the user loads. The PMAD supplies electric power for power conversion startup and for 

auxiliary loads associated with the reactor and heat rejection. The PMAD also provides the primary 

communications link for command, telemetry, and health monitoring of the FSP system. The reactor core 

is located at the bottom of an approximate 2 m deep excavation with an upper plug shield to protect the 

equipment above from direct radiation. The NaK pumps, Stirling convertors, and water pumps are 

mounted on a 5 m tall truss structure that attaches to the top face of the shield. Two symmetric radiator 

wings are deployed via a scissor mechanism from the truss. Each radiator wing is approximately 4 m tall 

by 16 m long and is suspended 1 m above the lunar surface. In its stowed configuration, the FSP system is 

approximately 3 by 3 by 7 m tall. More information on the FSP reference concept can be found in 

NASA/TM—2010-216772 (Ref. 4). 
NASA/TM—2011-216976 4 

Figure 1.—FSP reference concept. 

FSP “Pathfinder” technology development included component research as well as component and 

subsystem demonstrations needed prior to designing, fabricating, and testing of a full-scale system 

technology demonstration. Areas of Pathfinder technology development and demonstration included 

reactor simulation (including an electrical heat source and the liquid metal heat transfer loops), liquid 

metal electromagnetic pumps, power conversion units, heat rejection radiators, and integrated reactor 

simulator/power conversion tests. Prior publications provide more information on this phase of FSP 

technology development (Refs. 5 to 8). Successful completion of a majority of the milestones in this 

phase of testing has provided sufficient confidence to proceed with the design of the full scale system 

level Technology Demonstration Unit. 

FSP Technology Demonstration Unit Overview 

The TDU is an end-to-end system test of a reactor simulator (Rx Sim), Power Conversion Unit 

(PCU), and Heat Rejection System (HRS) in thermal-vacuum as shown in Figure 2. The TDU is intended 

to demonstrate the major elements of a notional Fission Surface Power System (FSPS) using a nonnuclear heat source. The Rx Sim includes an electrical resistance heat source and two liquid metal 

(sodium potassium or NaK) heat transport loops. It simulates the reactor thermal interface and expected 

dynamic response. The PCU generates electric power utilizing the heated liquid metal and rejects waste 

heat to the HRS. The HRS includes a pumped water cooling loop coupled to vertical radiator panels 

suspended in the thermal-vacuum facility. An intermediate test configuration, prior to the installation of 

the HRS, includes a Facility Cooling System (FCS) to reject PCU waste heat utilizing an external heat 

exchanger. The data acquisition and control, and power management and distribution equipment would be 

external to the vacuum facility and provide prototypic functionality using commercially available, rackmounted components. 

TDU Objectives 

The primary objective of the TDU is to demonstrate the technology readiness of the integrated FSP 

system using a non-nuclear heat source. Upon completion of the testing, FSP technology will achieve 

Technology Readiness Level 6 (system demonstration in an operational and relevant environment). This 

is based on the use of high-fidelity hardware and prototypic software tested under realistic conditions and 

correlated with analytical predictions. The nuclear aspects of the system will not be demonstrated in the 
NASA/TM—2011-216976 5 

Figure 2.—TDU test layout. 

TDU, but those are considered fairly mature based on terrestrial reactor technology. Some nuclear-related 

technology development will be conducted in parallel with the TDU including reflector control drive 

testing, shield development, and material/component irradiation testing. If FSP technology were to be 

selected for an exploration power application, the FSP reactor would be developed and qualified as part of 

a subsequent mission flight development program. Further, the TDU will not demonstrate system lifetime 

or launch/landing survivability, since both of those items are better addressed in a flight program when 

the requirements are better defined and the design is more mature. 

Some of the major challenges that the TDU testing will address are the liquid metal heat transport, 

electric power generation, and waste heat removal. The basic test plan is to subject the system to realistic 

operating conditions and gather data to better understand performance sensitivity, control stability, and 

response characteristics. A more comprehensive set of TDU objectives is enumerated in Table 1. 

TDU Block Diagram 

The TDU Block Diagram is shown in Figure 3. The Rx Sim includes a Core Simulator, a primary 

NaK heat transport loop, a NaK-to-NaK intermediate heat exchanger (IHX), and an intermediate NaK 

heat transport loop. The Core Simulator includes a series of pin-type electrical resistance heating elements 

arranged to represent the reactor fuel pin bundle. The two NaK loops each include an electromagnetic 

pump and volume accumulator. A NaK Fill & Drain system provides the capability for charging and 

discharging the two NaK loops. A Rx Sim Controller collects data, relays command signals, and supplies 

electric power for the Rx Sim components. The Rx Sim controller provides the means to control core 

simulator NaK outlet temperature and NaK flow rate in both loops. It also would include the software to 

simulate the expected temperature-reactivity feedback dynamics of a FSPS reactor. 

The PCU consists of the Power Converter, PCU Controller, and Gas Fill & Drain system. The Power 

Converter includes a NaK-to-gas heat exchanger for heat input and a gas-to-water heat exchanger for 

waste heat removal. Two power conversion technologies are currently under consideration: Brayton and 

Stirling. The Brayton option would utilize a single heat engine with a rotating turbine-alternatorcompressor and gas-to-gas recuperator. The Stirling option would utilize two free-piston heat engines 

with integral regenerators and linear alternators in an opposed configuration to balance motion. The Gas 

Fill & Drain system provides the capability for charging and discharging the converter’s working fluid, 

either CO2 for the Brayton option or helium for the Stirling option. The PCU Controller collects data, 

relays command signals, and supplies startup electric power for the converter. It also processes the 

electric output of the converter providing AC-DC conversion, parasitic load control, and voltage 

regulation. 
NASA/TM—2011-216976 6 

TABLE 1.—TDU OBJECTIVES 

1. Reduce FSP Development 

Risk 

 Build non-nuclear components that are representative of possible flight 

components to provide a hardware basis for the initial flight design 

2. Verify System-Level 

Performance in Realistic 

Environment 

 Achieve TRL6 by operating the integrated (non-nuclear) system in thermalvacuum 

 Measure power output of the integrated system and compare to predictions 

 Use measured parameters to determine system energy balance and efficiency and 

compare to predictions 

 Demonstrate the functionality of the integrated system over a wide range of 

conditions without failure 

3. Characterize Component 

Performance in a System 

Context 

 Measure component interface parameters including temperature, pressure, and 

flow rate and compare to predictions 

 Demonstrate the functionality of the components over a wide range of conditions 

without failure 

4. Obtain Operational Data under 

Steady-State and Transient 

Conditions 

 Instrument the system to permit measurement of all pertinent operating 

parameters 

 Collect steady-state data at various operating set-points (e.g., full power, part 

power, low reactor temp, low/high radiator temp, etc.) 

 Collect transient data during startup, set-point changes, environmental changes, 

simulated faults, shutdown, and restart 

5. Develop System Control 

Methods 

 Demonstrate electrical controls that isolate the thermal system from electrical 

transients (e.g., user load fluctuations, over-load, short circuit) 

 Demonstrate that the system can respond to environmental changes (e.g., lunar 

day/night cycle) and simulated faults (e.g., loss of reactor flow, loss of radiator 

flow, power conversion unit shutdown) without failure 

 Perform tests to optimize system response to operating changes and implement 

automated algorithms that perform those functions 

6. Benchmark Analytical Codes  Generate pre-test performance predictions for planned test sequences and 

compare with measurements 

 Modify codes as necessary to accurately represent test conditions 

 Use test-validated codes to assist in flight system concept development 

7. Gain System Operations 

Experience for the 

NASA/DOE Team 

 Establish a team of personnel across NASA, DOE, and industry that is familiar 

with the operation of the integrated (non-nuclear) system and its components 

 Collect 100’s of hours of system operations data 

8. Expand Industrial 

Infrastructure for Component 

Design and Fabrication 

 Provide opportunities for industry to design and build FSP components including 

power conversion units, heat exchangers, radiators, pumps, accumulators, piping, 

insulation, sensors, and controllers 

9. Obtain As-Built Mass and 

Cost Data 

 Document the mass and cost of the various components to support future flight 

system estimates 

 Document the cost of system integration and test to support future test cost 

estimates 

10. Provide Tangible and 

Measurable Technology 

Milestone 

 Complete an activity that clearly demonstrates the technical readiness of FSP to 

proceed into flight development 
NASA/TM—2011-216976 7 

Figure 3.—TDU block diagram. 

The HRS consists of a radiator, pumped water heat transport loop, and HRS controller. The radiators 

are two-sided vertical panels with embedded titanium-water heat pipes. The radiator panels include a 

manifold with heat exchangers to transfer heat from the pumped water loop to the heat pipe evaporators. 

The heat pipes transfer the heat to the condenser section and then to the panel surface where it is radiated 

to the walls of the thermal-vacuum chamber. The water heat transport loop provides direct cooling of the 

Power Converter and includes a pump and volume accumulator. The HRS controller collects data, relays 

command signals, controls the pump flow rate, and supplies pump power. 

Prior to the HRS installation, the FCS will provide waste heat removal for the Power Converter. The 

FCS will also utilize water coolant and will include all of the equipment to circulate the water and remove 

the waste heat using a commercial heat exchanger located outside the vacuum chamber. The H2O Fill & 

Drain provides the capability for charging and discharging the water loop with either the HRS or FCSbased test configuration. 

The balance of the test system is associated with the facility. The facility includes the Vacuum 

Chamber (Vacuum Facility #6), Liquid Nitrogen (LN2) cold wall, LN2 Fill & Drain system, Facility 

Controller, Facility Power, Electric Load Simulator (ELS), and Data Acquisition System (DAS). The 

Vacuum Chamber is a 21 m long by 7.6 m diameter horizontal cylindrical tank with cryogenic pumps. 

The LN2 cold wall extends along the center 16.2 m of the chamber length and covers all but the bottom 

60° of the circumference as shown in Figure 3. The LN2 sections would operate at liquid nitrogen 

temperature (77 K) while the bottom and end-cap sections would be at ambient temperature (300 K). The 

LN2 Fill & Drain provides the capability for charging and discharging the cold wall. The Facility 

Controller provides the operations interface for the Vacuum Chamber and LN2 cold wall. The Facility 

Power supplies electric power for the TDU components with availability of 110, 220, 440, and 208 V 

service. 

The ELS receives the regulated electric power from the PCU controller and provides a user interface 

for switching typical loads. The ELS also provides the power bus for starting the Power Converter. The 

DAS provides a central data collection node for the Rx Sim, PCU, and HRS Controllers as well as facility 

instrumentation. A communication network is envisioned that will permit the transfer of data between the 

various controllers and the DAS. 
NASA/TM—2011-216976 8 

Figure 4.—LN2 cold wall arrangement. 

Figure 5.—Key performance requirements. 

A summary of the key TDU performance requirements with a Stirling PCU is shown in Figure 5. The 

Core Simulator nominal input power is 55 kWe producing a primary NaK outlet temperature of 875 K. 

The IHX transfers about 48 kWt to the intermediate loop with a NaK outlet temperature of 850 K. The 

Stirling PCU generates 12 kWe and transfers 36 kWt to the water cooling loop with an inlet temperature 

of 375 K. A 55 m2

 radiator with an outlet temperature of 375 K rejects the 36 kWt to the thermal-vacuum 

chamber cold sink of 175 K. The 400 Vac Stirling alternator output power is processed in an electrical 

controller that delivers 10 kWe to the ELS at 120 Vdc. The TDU system is intended to function over a 

wide range of operating points and transient conditions, representative of what could occur in a lunar or 

Mars surface mission. The primary test variables are core simulator power, primary and intermediate NaK 

flow rate, Stirling piston amplitude, water flow rate, sink temperature, and user load demand. 
NASA/TM—2011-216976 9 

Preliminary TDU Test Planning 

The TDU test program will be defined in detail at the Test Readiness Review prior to starting the initial 

test phase. A preliminary test plan has been developed to guide the design process and identify operational 

expectations for the test hardware. The overall test philosophy is to start simple and introduce greater 

complexity as operations experience is gained. The testing is expected to occur in two major phases: 

Reactor-Power Conversion Test and Integrated System Test. The Reactor-Power Conversion Test will 

include the Rx Sim and PCU with the external FCS providing waste heat rejection. The Integrated System 

Test will replace the FCS with the HRS including the internal radiator panels. Within each phase, there will 

be a number of test sequences, and each sequence will have a specific test objective. A test sequence will 

produce a number of steady-state test points and answer the key technical issues related to the test objective. 

The basic test plan is to subject the system to realistic operating conditions and gather data to better 

understand FSP system performance sensitivity, control stability, and response characteristics. 

A pre-test analytical simulation will be generated to guide the test sequence and assure that the 

system is operated within prescribed limits. Test sequences will be conducted on a 24 hour per day 

operation schedule and could last from several days to over a week in duration. At the conclusion of a test 

sequence, the system will be shutdown and the test team would thoroughly review the data. The test data 

will be used to update the analytical model and provide improved accuracy for the next test sequence. 

FSP Technology Demonstration Unit Status and Outlook 

The TDU System Requirements Review was held in December 2008 at which time a draft TDU 

System Specification was generated to guide the design process. In February 2009, the TDU Preliminary 

Design Review formally kicked off the development of the FSP TDU. An independent review panel 

evaluated the readiness of the TDU system and component designs to proceed to final design, consistent 

with the TDU objectives listed in Table 1 and the requirements shown in Figure 5. In May 2009, an 

independent panel reviewed the final designs and fabrication readiness of the main TDU components: 

Core Simulator, NaK Pump, NaK Accumulator, Intermediate Heat Exchanger, and Power Conversion 

Unit. An additional product of the May review was a final management-approved TDU System 

Specification. The design formulation process culminated with the TDU System Final Design Review in 

October 2009 where a third independent panel evaluated the system design readiness and recommended 

that the project proceed. All major components of the TDU are now in development, and test facility 

modifications are in process. One exception is the TDU intermediate heat exchanger, shown in Figure 6, 

which was completed by ORNL and delivered to MSFC in April 2010. 

Figure 6.—TDU intermediate heat exchanger. 
NASA/TM—2011-216976 10 

Another major milestone in TDU development was the initiation of the PCU fabrication contract. 

Sunpower, Incorporated was selected to fabricate and test a 12 kWe PCU consisting of two 6 kWe 

Stirling engines, and began work in March 2010. Figure 7 shows the design for the thermodynamicallycoupled pair of engines with interfaces for the liquid metal heat input from the reactor simulator (central 

pipes and manifold), and the pumped water waste heat rejection (two outer pipe sets and manifolds). The 

PCU is expected to have a thermal-to-electric efficiency of approximately 27 percent with a NaK inlet 

temperature of 850 K and a water inlet temperature of 375 K. A prototype with two electrically-heated 

1 kWe Stirling engines that share a common expansion space will be tested at GRC in 2010. 

Work is also proceeding on the core simulator. MSFC has completed the design and initial testing of 

the graphite heating elements that will be used to represent the reactor fuel pins. There are 36 heating 

elements in the TDU core simulator, each measuring about 1.5 cm diameter by 43 cm long. The graphite 

heaters are contained in a stainless steel sleeve that is in direct contact with the flowing NaK. Testing has 

confirmed that the heater elements can be operated up to 2.5 kWe each, indicating a total core simulator 

power capability of 90 kWe. This provides margin relative to the 55 kWe required for nominal system 

performance and operational flexibility for off-design and transient testing. A 7-tube heater bundle test 

apparatus, shown in Figure 8, was fabricated at MSFC to demonstrate multi-heater performance in a 

TDU-like configuration. Testing was performed in 2010 over a range of power levels, temperatures, and 

NaK flow rates representative of the requirements imposed on the TDU core simulator. 

Figure 7.—12 kWe dual-opposed PCU. 

Figure 8.—7-tube heater bundle test. 
NASA/TM—2011-216976 11 

Conclusions 

The TDU is a crucial step in demonstrating the readiness of fission technology for future space 

applications. The FSPS Project has completed concept definition studies and Pathfinder tests to help 

guide the TDU development effort. The TDU design process has included a System Requirements 

Review, Preliminary Design Review, and System Final Design Review with multiple independent review 

panels providing a confirmation of the approach and content. The various hardware elements are now in 

the fabrication stage with checkout testing slated to begin in 2011. The TDU test will occur in two phases. 

During the first phase, the reactor simulator and power conversion unit will be assembled and tested in 

thermal-vacuum. An external facility cooling system will provide the PCU heat rejection using a 

commercial water-to-air heat exchanger. Phase 1 hardware checkout testing is scheduled to begin in 2012. 

Also during the first phase, the heat rejection system design and fabrication will be completed. After the 

phase 1 testing, the HRS will be integrated into the TDU. Phase 2 testing of the fully integrated system is 

scheduled for completion during 2014, establishing system-level technology readiness of fission power 

for exploration applications. 

References 

1. “NASA Research and Technology Program and Project Management Requirements,” App. J, 

NASA Procedural Requirement 7120.8, February 5, 2008. 

2. Palac, D., Mason, L., and Harlow, S., “Fission Surface Power Technology Development Status,” 

NASA/TM—2009-215602, March 2009. 

3. Palac, D., Mason, L., and Harlow, S., “Fission Surface Power Technology Development Status,” 

NASA/TM—2010-216249, April 2009. 

4. Fission Surface Power Team, “Fission Surface Power System Initial Concept Definition,” 

NASA/TM—2010-216772. 

5. Mason, Lee, “Recent Advances in Power Conversion and Heat Rejection Technology for Fission 

Surface Power,” NASA/TM—2009-204298, July 2010. 

6. “Performance of an Annular Linear Induction Pump with Applications to Space Nuclear Power 

Systems,” by Polzin, et al., Adkins Jr., Werner, IECEC. 

7. “Test Results From a Pair of 1 kWe Dual-Opposed Free-Piston Stirling Power Convertors Integrated 

With a Pumped NaK Loop,” by Briggs, et al., IECEC. 

8. “Performance Testing of a Full-Scale Radiator for Fission Surface Power Applications,” by Ellis, 

et al., IECEC. 
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13. SUPPLEMENTARY NOTES

14. ABSTRACT

Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and places beyond. Nuclear power is an important option, especially for locations in 

the solar system where sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA and the Department of Energy are maintaining 

the option for fission surface power for the Moon and Mars by developing and demonstrating technology for a fission surface power system. The Fission Surface Power 

Systems project has focused on subscale component and subsystem demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for 

surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power conversion, heat rejection, and power management and distribution 

technologies have validated that the fundamental characteristics and performance of these components and subsystems are consistent with a Fission Surface Power preliminary 

reference concept. In addition, subscale versions of a non-nuclear reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and operated 

with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the viability of establishing system-level performance and characteristics of 

fission surface power technologies without requiring a nuclear reactor. While some component and subsystem testing will continue through 2011 and beyond, the results to date 

provide sufficient confidence to proceed with system level technology readiness demonstration. To demonstrate the system level readiness of fission surface power in an 

operationally relevant environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power Technology Demonstration Unit (TDU) is under 

development. The TDU will consist of a non-nuclear reactor simulator, a sodium-potassium heat transfer loop, a power conversion unit with electrical controls, and a heat 

rejection system with a multi-panel radiator assembly. Testing is planned at the Glenn Research Center Vacuum Facility 6 starting in 2012, with vacuum and liquid-nitrogen 

cold walls to provide simulation of operationally relevant environments. A nominal two-year test campaign is planned including a Phase 1 reactor simulator and power 

conversion test followed by a Phase 2 integrated system test with radiator panel heat rejection. The testing is expected to demonstrate the readiness and availability of fission 

surface power as a viable power system option for NASA’s exploration needs. In addition to surface power, technology development work within this project is also directly 

applicable to in-space fission power and propulsion systems.

15. SUBJECT TERMS

Nuclear electric power generation 

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