Space Nuclear Power and Propulsion (SNPP)

STMD Space Nuclear Technologies Portfolio, September 1, 2020

Dr. Anthony Calomino | STMD Nuclear Technologies Portfolio Manager
The NASA STMD Space Nuclear Technology portfolio within the Technology 

Demonstration Mission program focuses on advancing nuclear fission 

technology and system capabilities to meet space exploration missions needs 

Ø Design, build, and demonstrate a space-rated fission surface power system that enables a 

sustained lunar presence and is directly extensible to future planetary surface missions

Ø Advance a deep-space, nuclear-propulsion capability through the maturation of key, 

high-risk technologies that lead to the design, build, and demonstration of a human rated 

propulsion system

Ø Establish collaborative, working relationships with other government agencies and 

organizations that share common, synergistic technology needs such as the DoD and DoE

Ø Catalyze industry and academic interest and support to enable broad spectrum of 

innovative and economic technology approaches and solutions

Space Nuclear Technology Overview 

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Space Nuclear Technology (SNT) Portfolio Projects

THE SPACE NUCLEAR TECHNOLOGY PORTFOLIO WITHIN MSFC-LED TDM PROGRAM

CONSISTS OF TWO MAJOR FISSION TECHNOLOGY INVESTMENT AREAS

Fission Surface 

Power (FSP)

Solar independent, continuous power production

§ Enable sustained, long-duration lunar operations

§ Demonstrate operational extensibility to Mars mission

Space Nuclear 

Propulsion (SNP)

Enable opposition-class, short-duration Mars mission

§ Focus for NTP is on fuel and reactor technology maturation

§ Identify NEP subsystem capability gaps and needs

§ Advance critical CFM technologies needed for SNP 

Prioritize lunar surface power while continuing to advance nuclear 

propulsion capabilities to support future human missions to Mars

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Space Nuclear Technology Projects

The Agency is currently engaged in advancing technologies for both 

propulsion and power fission systems with DOE support

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Ø Space Nuclear Propulsion (Mike Kynard, Prj Mngr, MSFC)

§ High temperature, 500 MW thermal reactor drives high Isp engine

§ Support for a common NASA/DOE/DOD fuel production 

capability

§ Pursuing a DOE industry solicitation for reactor designs

Ø Fission Surface Power (Todd Tofil, Prj Mngr, GRC)

§ Low weight reactor with 10 kW dynamic power conversion system

§ Requires near term reactor fuels and materials development

§ Open design and trade space will define ‘what’ the government 

needs, design and test qualification identified by industry

NTP vehicle concept

Government 

Reference Design

Investment is focused on two Projects within the Technology Demonstration 

Program managed by Marshall Space Flight Center

Agency reference configuration for Mars architecture is NEP
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SNPP Working Group provides a forum to collaborate on nuclear 

research and development areas of mutual benefit and reinvigorate 

US commercial nuclear industry

Current NASA/DOE SNPP collaborations fall under an existing 2016 MOU 

that establishes nuclear safety framework including indemnification

Potential opportunities for collaborative research and development 

with commercial partners that could benefit the space and terrestrial 

nuclear systems include:

Ø Reactor fuel and materials research and development

Ø Additive/advanced manufacturing methods and processes

Ø Test and demonstration infrastructure capabilities

NASA/DOE MOU Energy-related Civil Space Activities

Advanced RPS

Fission Surface Power

Kick-off at the Mars 2020 Perseverance launch, MOU supersedes a 1992 agreement and 

establishes interagency Working Groups on Strategic and Innovative Collaborations, 

Space Nuclear Power and Propulsion (SNPP), and Crewed Lunar Surface Environments
Fission Surface Power (FSP)
Fission Surface Power (FSP)

“The United States 

will...establish a sustainable 

human presence on the 

Moon by 2028, and chart a 

future path for Mars 

exploration.

White House Fact Sheet, 26 Mar 2019

NASA and DOE are collaborating on the development of a 10 kWe-class fission power system 

for a flight demonstration to the Moon by 2027, with extensibility to human Mars missions.

FSP Government 

Reference Design

Fission surface power is the Agency’s top nuclear priority

Ø Enabling capability for lunar sustainable presence and crewed Mars exploration

Ø Provides a near-term opportunity for fabrication, testing, and flight of a space fission system

Ø Will serve as a pathfinder for launching and operating other space fission systems

Ø DOE identified moderated HALEU FSP reactors and recently released an RFI for Industry Designs 

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FSP Integration Story

Mars Surface Power Needs

• Nominal 10 kWe power source 

meets current Mars surface 

power needs

• Lunar operational needs and 

performance metrics feed 

forward to lunar demonstration

Lunar Surface Sustainability

• System design to provide 

dissimilar redundant power for 

sustained operation 

• Concept of operation includes 

power management system, 

power cable, cable cart, and 

avionics 

Lunar Surface Fission Power 

Demonstration

• Design, fabricate and qualify a 

launch ready 10 kWe FSP flight 

unit by late 2020’s

• Flight qualified hardware 

needed for reactor, power 

conversion and heat rejection

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DOE reactor study completed in March 2020 identified 

LEU reactor solutions in same mass class as HEU system

§ These are moderated reactors with lower technology 

maturity but potential alignment with industry
Fission Surface Power Lunar Demonstration

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Fission Surface Power System Design 

Ø Power: 10kWe 

Ø Life: 10 year design life

Ø Modularity: Multi-unit interconnectivity to accommodate higher power

Ø Distribution: 1km cable cart + conditioning box

Ø Radiation: ~5 rem/yr @ 1 km (fission source) requires cable cart

Ø Current government reference design calls for a moderated LEU reactor with a 

Stirling power conversion system has an estimated launch readiness date in 2028

§ Risk reduction activities are needed for moderated reactor and a 1 kWe space-rated 

Stirling power conversion unit

Ø Request for Information issued on July 23rd in partnership with DOE seeking industry 

designs for a FSP full system

§ DOE led acquisition provides security, safety, and indemnification framework

§ Mass of cable could be traded against source radiation exposure

§ Upper mass limit may be traded with higher power output range

§ Still considering opportunity for cost sharing with industry

Fission Surface Power Project Status
Industry FSP System Design Solicitation

Provides opportunity to explore Innovative design approaches for FSP system

Ø Leverage industry approaches to design and operational reliability

Ø Identify path leading to a test qualified flight unit by December 31, 2026

Ø Identify technology maturation needs, development risks, subsystem tradeoffs

Ø Identify approach to ground testing and nuclear safety

Ø Forum for partnering relationships between aerospace and nuclear industries

Industry Day was held August 20, 2020 (virtual)

Ø Included talks from James Reuter (STMD), Dr. Rita Baranwal, (DOE), Aaron Miles (OSTP), 

and Ryan Whitley (NSpCl)

Ø Open Discussion and One-on-One Industry /Government Sessions

Ø Phase 1 RFP release October 2020 → Preliminary Designs by December 2021

Ø Phase 2 RFP release January 2022 → Flight unit design, test and launch ready by 2027

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ü Over 180 online participants

ü Extended open discussion

ü Setting up web site for partnering

ü Twelve industry 1-on-1 sessions

ü BWXT, GA, Lockheed, TerraPower, 

Blue Origin, Aerojet Rocketdyne, etc.
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FSP Technology Maturation Initiatives 

Ø Advance moderated HALEU reactor design TRL (3/4-6)

§ Technology developments are related to the moderator life testing and qualification 

Ø Advance Non-nuclear reactor sub-system assembly 

TRL’s (3-5)

§ Design, test and qualify central shutdown rod mechanism

§ Develop thermal and mechanical core-to-heat pipe bonding 

§ Design, fabricate and qualify neutron and gamma shield; 

§ Design, fabricate, and qualify multi-layer insulation

Modified 80 W Stirling 

convertor with electric heater

1,000 watt Stirling

Ø Advance Stirling converter/controller TRL 4–6:

§ Development of a 1 kW class converter and 

controller focused on robustness
FSP Technical and Programmatic Challenges

Challenges

Ø Commercial alignment of industry

Ø Integration/alignment with government design

Ø Secure funding profiles needed to support flight unit 

development, design, and build 

Ø Definition of human reliance rating for system 

operational reliability

Ø Commonality/synergy with future, higher power fission 

power system needed for ISRU and NEP/Chem

Ø Coordination of design capability/flexibility and 

extended lunar concept of operations

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FSP concept on a Blue 

Moon Lander
Space Nuclear Propulsion (SNP)
Space Nuclear Propulsion

STMD current nuclear propulsion technology investment remains focused on 

NTP, and planning meetings are examining NEP subsystem maturation 

requirements.

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NEP vehicle concept

Nuclear Thermal Propulsion System 

Ø Isp estimates are driving reactor temperature to exceed 2900 K

Ø Primary focus is fuel and reactor technology maturation 

Ø Leveraging common NASA/DOE/DOD fuel production capability

Ø Strong DOE collaboration with SME and testing support

Ø Engaged with industry and current solicitation for reactor support

Ø Advance CFM capabilities needed for NTP systems

Nuclear Electric Propulsion System

Ø Current Agency reference configuration for Mars architecture

Ø Coordinating FY20-21 strategy and planning meetings to identify 

technology requirement leading to an implementation plan

NTP vehicle concept
NTP Fuel and Reactor Development 

CerMet

Fuel

Government 

Ref. Design

PRIME 1

Nuclear Test

PRIME 2

Nuclear Test

CerCer

Fuel

PRIME Test 

Faciity

FY21 FY22 FY23 FY24

CerCer

Fuel

CerMet

Transient

CerCer

Transient

CerMet

Process

CerCer

Process

CerMet

Fuel 

ØProject primary focus for the next three years is to develop a high-temperature HA-LEU 

fuel form moderator-block reactor design

§ Moderator block accommodates UN to UC fuel transition plans and has flight heritage 

with the Russian Topaz reactor

§ Building-block strategy to fuel development is key to maturing critical technology 

path

• Optimizes ability to advance fuel fabrication capability and reactor design simultaneously

• Primary development of 900 sec Isp refractory metal fuel (CerMet) with later transition 

to >950 Sec Isp ceramic (CerCer) fuel

• Baseline chemistry is UN with concurrent, accelerated development of carbide chemistry HALEU Reactor 

Concept

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Ø Baseline government reference reactor design is a moderator 

block using a sintered solid-core fuel column

§ Design approach uses spark-plasm sintering to obtain a solid core 

fuel wafer and has shown to ability retain kernel coating structure

§ Thermal testing in March 2020 and July 2020 demonstrates robust fuel form 

and fuel column manufacturing methods for 900 sec Isp system

Ø NASA/DOD-SCO fuel production partnership awarded to BWXT

§ Accommodates AGR TRISO and coated-carbide particle fuel production

§ Kick-off meeting was held in July 2020 and first fuel production is planned 

for early FY22

Ø Flight Demonstration Study for 900 sec Isp reactor designs completed in July 2020

§ Eight week extension narrowed design revisions to NASA MSFC engine balance requirements

§ Reactor designs provided by BWXT, USNC, X-Energy, and General Atomics ranged from 

moderator block to Rover/NERVA design approaches

§ Independent review team assessed strengths, weaknesses, opportunities, and risks for each design

Nuclear Thermal Propulsion Development Status

Successful fuel column test specimen

Coated particle fission fuel

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Base

2-4 Contracts

Option 1

1-2 Contracts

Option 2

1 Contract

Reactor Preliminary Design

(30% Design Review)

Reactor Detailed Design

(90% Design Review)

Reactor Final Design

(Fabrication, Build, and Integration)

Nuclear Thermal Propulsion Industry Solicitation

Ø The proposed reactor designs will use high assay low-enriched uranium and produce a 

hydrogen propellant outlet temperature of at least 900 seconds Isp for a 12,500 lbf

subscale engine

Ø Draft RFP was released through DOE/INL on 8/7/2020 and comment period closed on 

8/21/2020

Ø Final RFP is expected to be released before the end of September 2020

Ø Industry analyses and data products need to demonstrate proposed design will meet 

performance requirements, and must identify quality assurance requirements that will 

be applied during fabrication and testing of the reactor system 

CY 2021-22 2022-2026
Nuclear Transient 

Test - 2

UN cermet & UC cercer

Currently running at INL

Nuclear Transient 

Test – 3

UN cermet

July, 2021

PRIME – 1

UN cermet, 

flowing hydrogen

July, 2022

PRIME –2

UN cercer, 

flowing hydrogen

July, 2023

Purpose: Investigate impacts 

of temperature ramp rate 

and operating temperature 

on CerMet and CerCer fuel

Specimen Geometry: Single 

hexagonal wafer, angular 

uncoated fuel, 19 flow 

channels, no flow tubes

Environment: Static safe gas

Purpose: Investigate impacts 

of temperature ramp rate 

and operating temperature 

on subscale fuel column

Specimen Geometry: 

subscale fuel column length, 

unbonded circular wafers, 

uncoated angular fuel 

kernels, 7 flow channels, 

unbonded Mo flow tubes

Environment: Static safe gas

Purpose: Investigate 

interactions of fuel and 

moderator in flowing hydrogen 

Specimen Geometry: halfscale unbonded circular wafers 

in prototypic reactor fuel 

column with moderator and 

thermal management 

materials, CerMet coated 

spherical fuel kernels, 7 flow 

channels, bonded Mo flow 

tubes

Environment: Flowing hydrogen

Purpose: Investigate integrity of 

fuel + moderator unit cell in 

flowing hydrogen

Specimen Geometry: half-scale 

fuel column with un-bonded 

circular wafers in prototypic 

reactor fuel column with 

moderator and thermal 

management materials, CerCer

coated spherical fuel kernels, 19 

flow channels, bonded Mo flow 

tubes

Environment: Flowing hydrogen

Fuel Development Nuclear Testing with Idaho National Laboratory

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NASA funding and teaming with INL to add flowing hydrogen 

capability to the TREAT reactor for the Prime 1 & 2 test series
Nuclear Electric Propulsion

ØIn conjunction with MTAS and Agency NEP reference configuration for Mars architecture, 

SNP project office will coordinate an effort to identify state of the art for key subsystems, 

technology gaps, infrastructure needs, programmatic schedule and risks from a project 

implementation perspective

ØKey implementation considerations include: 

§ Reactor

§ Power Conversion

§ Heat Rejection

§ High-output Hall Thruster Development

§ Methane Engine Development

§ Infrastructure (testing, propellant production, etc.)

ØGoal is to deliver a draft project development plan (scope, cost, schedule) consistent with 

accomplishing the NEP/Chemical Stage combination vehicle by mid FY21

ØSNP project office is planning a “state of things” meeting in September 2020

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NESC Review NTP and NEP Final Report

Ø Performed an independent assessment of the technical maturity and gaps for NTP and 

NEP/Chem propulsion systems

Ø Mission-agnostic assessment provided system and component evaluations that are 

independent of specific architectures

Ø Assessment focused on in-space, orbit-to-orbit transportation elements with a 

grounding assumption that technology must be qualified and launch ready by 2035

Ø Evaluations included Technology Readiness Level (TRL), Advancement Degree of 

Difficulty (AD2), Schedule Stoplight (G,Y,R), and binned Cost Metrics

Ø Four primary technology groups were evaluated 

§ NTP/NEP Reactors and Fuels, NEP Auxiliary Systems, Cross-Cutting Technologies

Ø Majority of critical technologies for both propulsion systems are immature and at a 

high level of advancement difficulty

Ø Most of the assessed technologies could be matured to support launch readiness by 

2035 given a dedicated, highly focused, and robust funded program
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Ø MTAS 1.1 (2035 opposition class mission, NRHO staging, 2 SLS 

launches/year)

§ Nuclear fuel and reactor development for both NTP and NEP/Chem are the most 

challenging technologies with the long lead-times

§ Long-term cryogenic fluid management and storage is a critical technology 

development, particularly for NTP which requires liquid hydrogen

§ NEP/Chem requires fewest launches and is considered feasible but challenging 

§ NRHO is not an optimal staging condition for the higher thrust NTP system and drives 

up Isp requirement

§ NEP system is complex and subsystem integration needs successful demonstration

Ø MTAS 1.2

§ Determine architecture needs consistent with technical capabilities for each system

Mars Transportation Architecture Study (MTAS)

Foster an objective understanding of in-space nuclear propulsion systems as it relates to 

mission performance and assess capabilities essential to the development of system 

advancements that can be used to guide both policy and technology investment decisions
Ø Committee membership

§ Roger Myers, R Myers Consulting (co-chair)

§ Robert Braun, JPL (co-chair)

§ Shannon Bragg-Sitton, INL

§ Jonathan Cirtain, BWX Technologies 

§ Tabitha Dodson, DARPA 

§ Alec Gallimore, U Michigan

Ø A committee convened by the National Academy of Sciences will assess both NTP and NEP with respect to:

§ Key technical and programmatic merits, challenges, and risks

§ Top-level development and demonstration roadmap with key milestones

§ Space exploration missions that could be enabled

Ø Study timeline:

§ A series of 13 weekly or biweekly 3-hour meetings; 5 meetings with public sessions)

§ 1st meeting: May 18; Last meeting: Sep 21

§ Report released Spring 2021

Ø Speakers at public sessions:

§ NASA

§ Idaho National Laboratory 

§ Los Alamos National Laboratory

§ Aerojet Rocketdyne

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§ James Gilland, Ohio Aerospace Institute 

§ Bhavya Lal, IDA/Science and Tech. Policy Institute 

§ Parviz Moin, Stanford

§ Joseph Sholtis Jr, Sholtis Eng & Safety Consulting

§ Steven Zinkle, U Tennessee Knoxville

National Academy of Sciences Assessment of NTP & NEP

§ Aerospace Corp

§ GA Tech

§ BWX Technologies

§ Ultra Safe Nuclear Technologies
SNP Technical and Programmatic Concerns

Challenges

Ø Fabrication and testing of high temperature composite fuel 

columns and reactor materials looking at UN/W-Mo cermet 

system and UC/ZrC cercer system to meet operational 

temperature (Isp) and neutronic requirements

Ø Focus is on developing a subscale (12,500 lbf) engine that can be 

ground or flight tested

Ø Both propulsion and power projects are working together to 

identify safety, licensing, and regulatory requirements

Ø PRIME test series will provide confidence high temperature 

requirements can be met, however, a cost-effective means to 

perform a full systems test through a ground or flight 

demonstration remains a near-term, critical need

Ø Schedule for NTP - NEP/Chem trade studies and decision on path 

forward has the potential to delay test demonstration 

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Summary

The NASA STMD Space Nuclear Technology portfolio has made 

good progress in FY 2020 to align investments for nuclear power 

and propulsion with implementable plans possessing 

achievable goals within realistic timeframes to meet NASA 

mission needs 

Ø FSP is actively seeking innovative industry solutions for a fission 

power capability that can align with commercial interests and 

can meet a launch readiness date as early as 2027 for a lunar 

surface demonstration mission

Ø SNP will engage industry reactor designers as a integrated team 

members critical to advancing the design, build, and 

demonstration of a engineering-relevant subscale NTP engine

Ø SNP is supporting ongoing Mars transportation architecture studies, 

the NEP reference configuration for Mars, and will adjust as 

necessary to accommodate Agency priorities

Ø SNT portfolio projects have working relationships with DARPA, DOE, 

and DOD and are identifying investment areas of common interest 

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