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 Status

NASA/TM—2010-216249

April 2010

AIAA–2009–6535
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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 Status

NASA/TM—2010-216249

April 2010

AIAA–2009–6535

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

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Acknowledgments

The authors wish to thank Jim Werner of Idaho National Laboratory, Dave Poston of Los Alamos National Laboratory,

Lou Qualls of Oak Ridge National Laboratory, and Steve Wright and Ross Radel of Sandia National Laboratories,

for their contributions to the FSPS project upon which sections of this paper were based. The information

discussed here was compiled for NASA with support from the Exploration Systems Mission Directorate

and with oversight by the Exploration Technology Development Program.

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NASA/TM—2010-216249 1 

Fission Surface Power Technology Development Status 

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 

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

is limited in availability or intensity. NASA is maintaining the option for fission surface power for the 

Moon and Mars by developing and demonstrating technology for an affordable fission surface power 

system. Because affordability drove the determination of the system concept that this technology will 

make possible, low development and recurring costs result, while required safety standards are 

maintained. However, an affordable approach to fission surface power also provides the benefits of 

simplicity, robustness, and conservatism in design. This paper will illuminate the multiplicity of benefits 

to an affordable approach to fission surface power, and will describe how the foundation for these 

benefits is being developed and demonstrated in the Exploration Technology Development Program’s 

Fission Surface Power Project. 

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 

goals, elements, and plans of the FSPS project have been explained in detail previously (Ref. 1); the 

project key goals are to: 

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

benefits over competitive options 

 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 

This paper examines the aspects of conservatism, robustness, and simplicity that result from, and are 

inherent in, an affordable approach to fission surface power. Initiation of the FSPS project was contingent 

on successful demonstration that a fission surface power system could be developed affordably. Key 

principles of an affordable approach included selection of component performance goals well within 

envelopes of existing experience and demonstrated capabilities where possible, avoidance of component 

technology development (especially in the reactor) to the extent practical, and selection of component and 
NASA/TM—2010-216249 2 

system solutions with lower risk and complexity, even at the expense of higher mass. A preliminary FSP 

concept was assembled using these principles, and the cost of the development of this concept through 

first and second flight units was calculated using a detailed and comprehensive work breakdown 

structure. A cost (FY 2007 dollars) of $1.4 billion for development and first flight unit, and $215 million 

for a second unit (both prior to application of reserves) was the result of the joint NASA/DOE cost 

estimation exercise that was also reviewed by aerospace industry systems development companies. Since 

the study was completed, however, it has become increasingly apparent that the principles of affordability 

applied to space nuclear power system development produce a range of benefits to potential users beyond 

just cost minimization. These resultant characteristics of simplicity, robustness, and conservatism will be 

reviewed below. 

An update of technology development activities to implement and demonstrate affordable fission 

surface power simplicity, robustness, and conservatism will also be provided. The FSPS project has 

recently advanced from early subscale component level technology demonstrations to the initiation of 

hardware development for a non-nuclear system level technology demonstration at 1/4 power and full 

scale in a relevant thermal-vacuum environment, called the FSP Technology Demonstration Unit (TDU). 

Test configurations and results of early subscale “Pathfinder” testing will be reviewed, illustrating how 

these Pathfinders have built confidence toward proceeding with TDU development. Status of TDU 

development activities and progress will be summarized. 

Nomenclature 

AFSPSS Affordable Fission Surface Power System Study 

ARPS Advanced Radioisotope Power System 

Cx Constellation (NASA Vision for Space Exploration flight hardware development program) 

DOE Department of Energy 

ETDP Exploration Technology Development Program 

FSP Fission Surface Power 

FSPS Fission Surface Power System 

FY Fiscal Year 

GPHS General Purpose Heat Source 

GRC Glenn Research Center 

HR Heat Rejection 

HRS Heat Rejection System 

HX Heat Exchanger 

I&C Instrumentation and Controls 

INL Idaho National Laboratory 

kg kilogram 

kW kilowatts 

kWe kilowatts (electric) 

kWt kilowatts (thermal) 

LaNL Los Alamos National Laboratory 

LaRC Langley Research Center 

m meter 

MSFC Marshall Space Flight Center 

MT Metric Tons (1,000 kg) 

NaK Sodium/Potassium mixture 

NASA National Aeronautics and Space Administration 

ORNL Oak Ridge National Laboratory 

PC Power Conversion 

PMAD Power Management and Distribution 

RDU Radiator Demonstration Unit 
NASA/TM—2010-216249 3 

rem Roentgen Equivalent Man 

Rx Reactor 

SNL Sandia National Laboratory 

TDU Technology Demonstration Unit 

TRL Technology Readiness Level 

yr year 

Benefits of an Affordable Approach to Fission Surface Power 

The Affordable Fission Surface Power System Study (AFSPSS) completed in 2007 was a 

collaborative effort that included participation from NASA, DOE, and nuclear industry expert 

consultants, and review by industry. The study team identified strategies to achieve affordability that 

included: 

 Modest requirements and operating conditions 

 Selection of a well-established reactor concept 

 Significant terrestrial and some space experience 

 Large fabrication experience (low cost) 

 Large operational database 

 Reactor design for self regulation of perturbations with large margins 

 Robust control system 

 Extensive reliance on existing terrestrial and prior space nuclear power systems databases 

Application of these strategies resulted in a FSP concept with the characteristics as shown in Table 1. 

TABLE 1.—AFSPSS PRELIMINARY BASIS FOR AFFORDABILITY 

Power level and design life  40 kWe, 5 to 8 years 

Design approach  900 K liquid-metal cooled reactor with UO2 fuel (terrestrial design basis), 

approximately 1 MWt thermal power level 

 Stirling power conversion with 850 K input, ~10 kWe/Stirling engine 

 400 K water radiators (ISS-derived), <200 m2

 400 V transmission, 120 V bus (ISS-derived) for loads 

Technology needs  Liquid metal primary loop and Stirling hot-end interface 

 End-to-end system performance test (TDU) 

 Reactor criticality benchmarking tests 

Launch and Startup  Up to two units delivered on a single lunar lander 

 Reactor startup after installation and crew inspection 

Mission and Environment  One of several power sources for crew and equipment; backup power and crew 

availability provide contingency options 

 Technology and concept design extensible to Mars surface missions 

 Lunar day/night cycle, 50 to 350 K sink, accommodation of dust 

The high energy density of nuclear power enabled a favorable trade on mass with risk and 

complexity, furthered also by the dominance of reactor and shielding mass with respect to the overall 

system mass. 

The FSPS affordable design philosophy is founded in principles of conservatism, simplicity, and 

robustness. 
NASA/TM—2010-216249 4 

Conservatism 

Review of the historical performance and cost trends for terrestrial and space nuclear power system 

development efforts suggests that cost increases with performance. While mission requirements for lunar 

and Mars exploration are not yet final, review of prior planetary surface outpost planning efforts indicated 

that required power is likely to be relatively modest for a nuclear power system, on the order of 100 kWe. 

The high energy density of nuclear fuel allows a power system of this size to be small, on the order of 

10 MT. Comparison to other lunar outpost element concepts showed that a FSPS would therefore be well 

within the range of payloads to be delivered to the outpost, and that the design of the FSPS need not be 

performance driven. Relaxation of performance as a design driver in favor of affordability presented an 

unconventional but useful set of design freedoms in defining a FSPS concept. 

A cornerstone of the design architecture for an affordable FSPS was the choice of constraining the 

reactor coolant outlet temperature to less than 900 K. This represents a relatively low temperature 

(compare to 1375 K for the SP-100 reactor designed during the 1980s (Ref. 2)). Constraining the reactor 

operating temperature allows the use of stainless steel and other non-refractory materials for power 

system structure. In addition, there exists decades of experience with reactor operation at low 

temperature, assuring that the design and operation of the FSPS reactor will be in a well-understood 

regime, and that new technology development for the reactor system can be minimized. 

Similar conservatism was applied in other conceptual definition choices. Throughout the FSPS 

conceptual design, component materials and fluids that have demonstrated compatibility with nuclear 

power applications were chosen to the maximum extent possible. Generous structural and performance 

margins were applied in structural design choices, as were large safety factors. Especially in the reactor 

module of the FSPS, the basis of the conceptual design for affordability was extensive terrestrial nuclear 

power system experience. 

The FSPS concept is composed of the reactor module, the power conversion module, and the heat 

rejection module. Of these modules, new development of reactor module technology is expected to be the 

least affordable. For this reason, definition of an affordable FSPS concept included minimizing 

technology development within the reactor module. In addition to the choice of the low temperature, 

several other affordable features of the reactor module contribute to conservatism. Enriched uranium 

dioxide fuel, baselined for the FSPS, has been extensively used in terrestrial reactors. Planned fuel burnup of less than 1 percent over 8 years alleviates concerns of fuel swelling due to build-up of fission 

product gases. NaK liquid metal reactor coolant has been used in fast spectrum reactors since the 1960s, 

and was the reactor coolant/heat transfer fluid used in the SNAP-10A reactor. Boron carbide shielding, 

selected for the portion of shielding to be launched with the reactor (supplemented with lunar regolith), 

also has been used extensively in terrestrial applications. These examples represent the continual 

emphasis on conservatism characterizing FSPS reactor module conceptual design. 

The baseline power conversion system technology chosen for the FSPS concept is Stirling dynamic 

power conversion. Stirling power conversion underwent extensive development for space mission 

applications during the 1980s. The Space Power Demonstration Engine, consisting of two 

thermodynamically coupled 12.5 kWe Stirling engines, was built to demonstrate 25 kWe Stirling 

conversion for use with the SP-100 space power reactor. The SPDE demonstration, followed by separate 

testing of the separated individual Stirling engines, totaled nearly 2000 hr (Ref. 3). More recently, Stirling 

power conversion technology has been further developed for space science missions utilizing the 

plutonium 238 General Purpose Heat Source, as part of the NASA Science Mission Directorate’s 

Advanced Radioisotope Power System (ARPS) program. Subkilowatt Stirling engines have been tested 

for over 10 years as part of this development (Ref. 4). Stirling engine technology development 

conservatism results from the approach of scaling the APRS technology to the multi-kilowatt level while 

maximizing the use of ARPS thermodynamic design, structural design, and materials choices. 

FSPS heat rejection technology conservatism is obtained primarily through the use of wellcharacterized fluids and materials. Water, pressurized to maintain the liquid state, is the fluid chosen for 

transfer of waste heat from the Stirling engines to the heat rejection system. Temperatures in the FSPS 
NASA/TM—2010-216249 5 

heat rejection system will range from about 350 to 450 K. Decades of experience exists for the use of 

pressurized water in far more severe conditions in the radiation environment of terrestrial pressurized 

water reactors. Titanium heat pipes are the material choice for FSPS radiator heat dissipation, with water 

as the heat pipe working fluid. Titanium compatibility with water at temperatures is well established 

(Ref. 5); additionally, FSPS technology development includes future testing of titanium with water in a 

radiation environment to verify compatibility. 

Simplicity 

The FSPS concept that results from emphasis of affordability over performance (allowing mass to 

vary as needed) is characterized by simplicity as well as conservatism. Many aspects of simplicity, as will 

be seen below, are enabled by the FSPS technology characteristics and reflected in operational aspects of 

the FSPS, and therefore are not planned for validation during FSPS technology development. The basic 

aspects of FSPS simplicity that result from an affordable approach will be briefly reviewed. 

While specific lunar or Mars outpost power and lifetime requirements have yet to be defined, the 

selection of modest system-level power goal of 40 kWe and lifetime goal of 8 years are fundamental to 

system simplicity. The modest power goal of 40 kWe reduces the thermal power of the reactor, simplifies 

the heat transport and thermal control needs, and minimizes the fission product that could contribute to 

material degradation. An 8-year life goal is key to this latter low demand on reactor fuel utilization. Both 

power and life allow the design of the reactor to be designed to operate at very moderate reactivity levels. 

This allows the design of the reactor with large margins against any possibility of uncommanded 

criticality (start-up). In addition, the lack of demand on reactor performance allows the flexibility to 

include, as part of the reactor characteristics, negative temperature reactivity feedback across the 

operating range of the reactor. This feature causes reactor reactivity to drop as temperature increases, 

resulting in a self-regulating characteristic of reactor operation that simplifies power system monitoring 

and control. Also because of its modest performance, the FSPS reactor responds slowly to changes, 

whether from control application or from unplanned transients. This contributes further to the simplicity 

of reactor monitoring and control. For details, see Poston, 2009 (Ref. 6). 

Another FSPS feature that contributes to system simplicity resulting from modest power requirements 

is the implementation of parasitic load control. The FSPS concept includes a parasitic load resistor bank 

as part of the power management and distribution system. These resistors radiate as heat any power that is 

not being consumed by user loads, allowing near-continuous operation of the FSPS at the designed 

40 kWe power output, with only minor changes resulting from the lunar day/night cycle. 

An FSPS concept feature that will be demonstrated during FSPS technology development is 

modularity. Modular reactor, power conversion, and heat rejection modules allow simplified phased 

testing and buildup during technology development as well as during engineering development and 

assembly for launch. Another key byproduct of modularity is the ability to perform system-level testing 

with a non-nuclear reactor simulator. All of the features of the FSPS reactor that result from an affordable 

approach (extensive experience with reactor operation and dynamics, modest performance, slow response, 

negative temperature reactivity feedback, etc.) contribute to the ability to model the reactor dynamic 

behavior with a reactor simulator with large margins on simulation fidelity. This avoids the need to 

perform costly nuclear system-level testing during technology development, while still providing a 

system-level demonstration of technology readiness in an operational environment. 

Robustness 

FSPS design for affordability leads straightforwardly to system robustness through relaxation of 

demands on performance. A common definition of robustness refers to the characteristic of available 

margin on operating conditions, which as explained above is a direct result of design for affordability. 

However, FSPS design for affordability, combined with the high energy density of nuclear power, has the 

multiplicative result that the total system mass is relatively insensitive to changes in mass of modules 
NASA/TM—2010-216249 6 

other than the reactor module itself. Put differently, the FSPS reactor and shield dominate the mass of the 

total system, to the order of approximately 60 percent. Redundant systems, additional structural mass, and 

de-rating of performance can be applied to reactor heat transport, power conversion, heat rejection, power 

management and distribution and system control hardware without major increases in total system mass. 

Safety is the first and foremost benefit to which robustness can be applied as a design degree of 

freedom. While the engineering flight design of an FSPS awaits the selection of the option for fission 

surface power by exploration mission planners, maximizing safety for all mission phases through wide 

margins on safety-related design and operation will be an available capability of an affordable FSPS design. 

High reliability and fault tolerance is also enabled by affordability-driven robustness. For example, 

consider a temporary loss of coolant flow to the FSPS reactor core resulting from a pump anomaly. 

Because of negative temperature reactivity feedback designed into the reactor, it would decrease its 

reactivity until the temperature adjusted to a new equilibrium level. Recovery from this condition would 

consist of restoring cooling via manipulation of liquid metal pumps and power conversion units until a 

nominal working configuration can be achieved. Once cooling flow is restored, the resulting reduction in 

temperature would cause the reactivity to increase, thus increasing the thermal output of the reactor. If 

necessary, reactor power could be adjusted through the rotation of control drums to provide a new 

optimum power level from the system. This scenario is provided as an example of how an affordable 

design provides capabilities that enable fault tolerance and recovery. Similar fault tolerance and recovery 

capability is available for conditions such as stuck reactor control drums, power conversion unit failure, 

radiator pump failure, radiator coolant loss, and electrical load loss. 

Because light weight and high performance are not critical to an affordable design, FSPS designers 

will have the luxury of selecting near-term technology components and parts for FSPS subsystems. 

Additionally, available mass margins can be utilized to provide redundancy and fault tolerance. FSPS 

modules built for engineering models and flight hardware can be designed with inherent toughness to 

withstand rigorous testing, and the affordability of these robust modules will also allow multiple design 

cycles and hardware iterations. 

Technology Development Progress 

The FSPS technology development project initiation was contingent on demonstration of the 

affordability of a fission surface power system via a detailed, credible estimate of cost of an FSP concept 

that targeted affordability as its principle design objective. Similarly, it is anticipated that a prerequisite to 

acceptance of FSP as an option for exploration outpost is the demonstration of an FSP system model 

demonstration in an operational environment, NASA’s definition of Technology Readiness Level 6 

(Ref. 7). This demonstration is the primary goal of the FSPS project. An overview of the project, its 

objectives, elements, and schedule, can be found in Palac, 2009. Significant progress has been made 

during 2007 and 2008 in the “Pathfinder” portion of the FSPS project, which has consisted of subscale 

demonstrations of the readiness of FSPS components and subsystems for development into full-scale 

components of a system-level FSPS Technology Demonstration Unit (TDU). A summary of recent 

demonstrations is presented below, and is illustrated by Figure 1. 

Reactor Simulator and Heat Transfer Loop 

As described above, affordable FSP is a result of minimization of reactor system technology 

development. However, the technology of simulating an FSP reactor with electrical heating requires 

development and demonstration. Building on work started under the Prometheus space nuclear power and 

propulsion program earlier this decade, MSFC has undertaken development of reliable high energy 

density electrical heater bundles that can simulate nuclear reactor components. Recent accomplishments 

include the fabrication of a Thermal Simulator capable of producing over 2 kWt for over 100 hr. This 

Thermal Simulator represents one element of a 37-element core simulator for the TDU. It will be tested to 

validate its performance during the fall of 2009 (Ref. 8). 
NASA/TM—2010-216249 7 

Transferring heat from the reactor simulator to the power conversion unit requires pumping of liquid 

metal NaK. In addition to its high performance as a heat transfer fluid, NaK also is amenable to pumping 

via interaction with an induced electromagnetic field. Electromagnetic pumps are typically less efficient 

and heavier than mechanical pumps, but have no moving parts, and therefore high reliability and 

simplicity. Electromagnetic pumps have been used in terrestrial liquid metal reactors, but none have been 

manufactured for over 15 years of the type suitable for an FSPS. Recently, fabrication of an 

electromagnetic Annular Linear Induction Pump (ALIP) was completed by Idaho National Laboratory 

and Pacific Northwest National Laboratory. It was practical to build an ALIP feasibility demonstration 

unit at full scale as an FSPS Pathfinder demonstration. The ALIP demonstration unit is designed to 

develop a pressure head of 58 to 68 kPa at a flow rate of approximately 4 kg/s. This pump will be 

installed in a liquid metal NaK test loop at MSFC in the fall of 2009 for performance testing (Ref. 9). 

Power Conversion 

Demonstration of Stirling engine readiness at multi-kilowatt electrical power levels was an important 

Pathfinder prerequisite to proceeding to full scale TDU power conversion unit design and fabrication. In 

addition, Stirling engine operation with heat supplied via liquid metal NaK had never been demonstrated 

prior to the FSPS Pathfinder demonstration. GRC worked with Sunpower, Inc., to modify a commercial 
NASA/TM—2010-216249 8 

Stirling engine design to meet the requirements of a Pathfinder demonstration unit, and Sunpower, Inc. 

fabricated two 1 kWe Stirling engines. GRC added liquid metal NaK heat exchangers to the engines, 

which were subsequently installed and tested in MSFC’s Primary Test Circuit laboratory. The NaKheated Stirling pair demonstrated 2.4 kWe of power, with a more-uniform-than-expected circumferential 

temperature distribution in the NaK heat exchanger, indicating low structural stresses in this critical 

interface. This accomplishment provides confidence for proceeding with the detailed design and 

fabrication of a full scale 12 kWe Stirling power conversion unit for the FSPS TDU, to be initiated in the 

fall of 2009. Details of this demonstration, and all power conversion and heat rejection activities in the 

remainder of this summary, can be found in Mason, 2009 (Ref. 10). 

For efficient transport of heat from the reactor to the power conversion system, the power conversion 

system must be located relatively close to the reactor. Stirling engines can thus be expected to be exposed 

to relatively high radiation doses during their operation. While the materials used in most of the Stirling 

engine structures and mechanisms are known to be tolerant of high radiation environments, some of the 

materials used in the linear alternator, and a few other areas of the Stirling engine, have less data available 

about their radiation tolerance. A recently completed Sandia National Laboratories irradiation test of a 

subscale Stirling alternator demonstrated operation of the alternator without degradation up to 20 times 

the expected gamma radiation dose for the life of an FSPS system. Material coupons representative of 

Stirling engine polymer adhesives, elastomers, tribological coatings, and wire insulation will also be 

irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor spent fuel pool in the fall of 

2009. 

Brayton power conversion is a viable back-up to Stirling power conversion for an FSPS. Though 

Brayton power conversion is less efficient than Stirling for the relatively low temperature heat from an 

affordable FSP reactor, Brayton engines have the benefit of low development risk, as there are 

commercial units currently available whose designs could be modified for an FSPS. A 2 kWe Brayton 

unit, original developed for the Solar Dynamic Flight Demonstration Project, was integrated with a 

MSFC-supplied Direct Drive Gas reactor simulator. Since Brayton power conversion uses gas as a 

working fluid in a closed loop for space power applications, the FSPS reactor would directly drive the 

Brayton closed loop by heating a gas, such as a helium/xenon mixture, which is then circulated to the 

Brayton power conversion unit. The demonstration was successfully completed in GRC’s Vacuum 

Facility 6 in 2009, with the Brayton system producing 2 kWe at nominal operating conditions. The test 

also demonstrated the Reactor Simulator’s capability to simulate reactivity control, successfully changing 

its heat output as a reactor would if commanded to change reactivity. During this testing, the Brayton unit 

responded as expected. 

Heat Rejection 

The FSPS heat rejection system must reject approximately 140 kWt of thermal power from the power 

conversion module at a temperature of 400 K or more. Titanium-water heat pipes embedded in composite 

radiators were selected as the most suitable technologies for these conditions, leveraging Prometheus 

Jupiter Icy Moons Orbiter mission studies. Over two years of heat pipe life demonstration, as well as 

three subscale composite radiator panels fabricated via contracted efforts, have provided FSPS needed 

data, courtesy of Prometheus Program initial technology investment. More recently, application of 

knowledge gained from these prior heat rejection demonstrations enabled the FSPS project to embark on 

development of a full scale “2nd Generation” Radiator Demonstration Unit (RDU). This RDU included a 

water manifold to deliver heat to the evaporator ends of the heat pipes, the heat pipes themselves, and the 

1.7 m tall by 2.7 m wide composite radiator panels that radiate the heat distributed through the panel by 

the heat pipes. The RDU was tested over the summer of 2009 in the GRC Vacuum Facility 6, and it 

successfully demonstrated the rejection of 6 kWt of heat as designed under simulated lunar conditions. It 

supports the planned procurement of a 36 kWt TDU heat rejection system, planned to be initiated in the 

fall of 2010. 
NASA/TM—2010-216249 9 

System Technology Demonstration Plans 

With the completion of the FSPS Pathfinder feasibility demonstrations of FSPS components and 

subsystems, the foundation has been laid for progression to development of a full-scale, 1/4 power 

(12 kWe) TDU. A final design review of the TDU system will be conducted in the October 2009. 

Procurement of the Power Conversion Unit for the TDU has been initiated, with contract award times for 

the fall of 2009. Build-up of the Reactor Simulator, starting with the Thermal Simulator bundle 

fabrication, has begun. Elements of the primary loop will be added between now and spring of 2011, 

including a primary and secondary ALIP, and NaK piping and inventory management equipment. Testing 

of this assembled Reactor Simulator module will be conducted at MSFC to demonstrate capability with 

liquid metal NaK to supply heat to the power conversion unit. Once completed in 2012, the Reactor 

Simulator will be delivered to GRC for integration with the completed Power Conversion Unit. Testing of 

the combined Reactor Simulator/Power Conversion Unit, with facility water cooling in place of the Heat 

Rejection System, will be conducted into 2013. Development of the Heat Rejection System will begin in 

2010 and be completed in 2013. The full TDU will be assembled in 2013, and completion of testing is 

anticipated in the fall of 2014. 

Summary 

In pursuing affordability of Fission Surface Power for its exploration mission, NASA and its partners 

have discovered that affordability leads to additional benefits that dramatically increase the conservatism, 

simplicity, and robustness of an FSPS. The benefits are only obtained, however, if the conceptual 

approach of an affordable FSPS is feasible. Recent Pathfinder demonstrations of FSPS components and 

subsystems have successfully demonstrated the fundamental FSPS approach to affordability is sound. 

This forms a solid basis for proceeding with the development of the system-level FSP Technology 

Demonstration Unit, which will establish the availability of Fission Surface Power as an option ready for 

development for NASA’s Exploration mission needs. 

References 

1. Palac, D., Mason, L., and Harlow, S., Fission Surface Power Technology Development Status, 

NASA/TM—2009-215602, March, 2009. 

2. Hyder, A.K., et al., Spacecraft Power Technologies, Imperial College Press, 2000, pp. 266–269. 

3. Mason, L., A Comparison of Brayton and Stirling Space Nuclear Power Systems for Power Levels 

from 1 Kilowatt to 10 Megawatts, NASA/TM—2001-210593, January, 2001. 

4. Schreiber, J., Thieme, L., and Wong, W., Supporting Technology at GRC to Mitigate Ris as Stirling 

Power Conversion Transitions to Flight, NASA/TM—2009-215515, April, 2009. 

5. R.W. Schutz, Corrosion of Titanium and Titanium Alloys, Corrosion: Materials, Vol. 13B, ASM 

Handbook, ASM International, 2005, pp. 252–299. 

6. Poston, D., et al., Reference Reactor Module Design for NASA’s Lunar Fission Surface Power 

System, Proceedings of Nuclear and Emerging Technologies for Space 2009, Atlanta, GA, June 14–

19, 2009. 

7. NASA Research and Technology Program and Project Management Requirements, NASA Procedural 

Requirement 7120.8, Effective February 5, 2008, Appendix J. 

8. Godfroy, T., et al., Technology Demonstration Unit Core Simulator Design, Proceedings of Nuclear 

and Emerging Technologies for Space 2009, Atlanta, GA, June 14–19, 2009. 

9. Werner, J., and Adkins, H., Electromagnetic Pump Fabrication and Predicted Performance, 

Proceedings of Nuclear and Emerging Technologies for Space 2009, Atlanta, GA, June 14–19, 2009. 

10. Mason, L., Recent Advances In Power Conversion and Heat Rejection Technology For Fission 

Surface Power, Proceedings of Nuclear and Emerging Technologies for Space 2009, Atlanta, GA, 

June 14–19, 2009. 
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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-04-2010 

2. REPORT TYPE

Technical Memorandum 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Fission Surface Power Technology Development Status 

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Palac, Donald, T.; Mason, Lee, S.; Houts, Michael, G.; Harlow, Scott 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 463169.01.03.01.01 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION

 REPORT NUMBER

E-17236 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING

 REPORT NUMBER

NASA/TM-2010-216249 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Category: 20 

Available electronically at http://gltrs.grc.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

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

option, especially for locations in the solar system where sunlight is limited in availability or intensity. NASA is maintaining the option for 

fission surface power for the Moon and Mars by developing and demonstrating technology for an affordable fission surface power system. 

Because affordability drove the determination of the system concept that this technology will make possible, low development and recurring 

costs result, while required safety standards are maintained. However, an affordable approach to fission surface power also provides the 

benefits of simplicity, robustness, and conservatism in design. This paper will illuminate the multiplicity of benefits to an affordable 

approach to fission surface power, and will describe how the foundation for these benefits is being developed and demonstrated in the 

Exploration Technology Development Program’s Fission Surface Power Project.

15. SUBJECT TERMS

Nuclear power 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

15 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18