Coote, David J.

NASA Technical Reports Server

Stennis Space Center
JANNAF Programmatic and Industrial Base Testing and 
Evaluation Technical Interchange Meeting 
Kennedy Space Center, FL
November 8, 2017
National Aeronautics and
Space Administration
Space Technology Mission Directorate 
Game Changing Development Program 
Low Enriched Uranium (LEU) Nuclear Thermal Propulsion: 
System Overview and Ground Test Strategy
Presented by: David Coote, NASA/SSC
https://ntrs.nasa.gov/search.jsp?R=20170011172 2019-08-31T01:32:28+00:00Z
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Background
How Does Nuclear Thermal Propulsion 
(NTP) Work?
2
Propellant heated directly by a nuclear reactor and 
thermally expanded/accelerated through a nozzle
 Low molecular weight propellant – typically Hydrogen
Specific Impulse directly related to exhaust temperature, e.g.: 2850K 
exhaust temperature translates to ~900 sec Isp
Major Elements of a Nuclear Thermal Rocket
XE-Prime Nuclear Thermal 
Rocket Prototype
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Full Funding Profile (all years):
• Budget vs. Requirements
Nuclear Thermal Propulsion (NTP) 
Game Changing Development Project Overview
FY16 FY17 FY18 FY19 Total
Approved 5.754 19.200 20.000 7.032* 51.986
Required 5.754 19.200 20.000 7.032* 51.986
Delta 0.000 0.000 0.000 0.000 0.000
Project Description: 
• Determine Low Enriched Uranium (LEU) NTP feasibility and 
affordability, with good cost and schedule confidence, prior 
to a decision to proceed with full scale development.
• Demonstrate the technology that enables the development 
of high temperature, minimum erosion/fission product 
release fuel elements (FE) using LEU.
• Leverages government, industry and academic expertise and 
existing facilities.
Roles and Responsibilities
• MSFC: PM, SE & Analysis Lead, Cryo ConOps Lead, FE Testing
• GRC: Cryocooler Testing, Cryo ConOps Support, Sys. Analysis Support
• SSC: Rocket Exhaust Capture System DDT&E
• KSC: Ground Processing ConOps / Propellant Densification
• Aerojet Rocketdyne: LEU Engine Analysis
• AMA: Engine Cost Lead
• Aerospace: Engine Cost Independent Review
• BWXT: Fuel Element / Reactor Design/Fabrication
• DOE: FE / Reactor Design and Fabrication Support
*FY 19 est. 3
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
• Reviewed past design efforts and testing to 
construct most affordable path to an NTP for 
Mars missions
• Baseline Design
 25,000 lbf thrust
 ~500MW
 Exhaust capture ground testing
• Uses Low Enriched Uranium (LEU)
 Enables the use of commercial manufacturing 
methods to arrive at best NTP system design to 
reduce cost with no impact on performance
 Use of LEU is consistent with US/international 
efforts to eliminate HEU in all civilian applications
 Enables tremendous programmatic flexibility, 
increasing choice of facilities, and project 
participants
NTP Current Baseline
Size comparison: Baseline 25klbf NTP (Left) vs. 
RL10 (right) Source: Aerojet Rocketdyne
4
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
NTP Technology Maturation Plan
5
We are here
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
NTP Technology Ground Test Strategy
• SSC has been supporting MSFC since FY14 on the AES/Nuclear Thermal 
Propulsion (NTP) Project.
‐ Project goal is to demonstrate the affordability and viability of nuclear thermal 
rocket propulsion
‐ Current focus is to define an affordable development and qualification strategy
6
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
♦ Bore Hole
• Relies on permeability of desert alluvium soil to filter engine exhaust
• Unresolved issues on water saturation effects on soil permeability, hole pressure during engine operation, 
and soil effectiveness in exhaust filtering
♦ Above Ground Scrubber and NNSS (Nevada National Security Site) P-Tunnel Scrubber Option
• Engine exhaust is filtered of radioactive aerosols and noble gases and directly flared to atmosphere
• Nuclear Furnace (NF-1) ground test scrubber successfully tested at the end of Rover/NERVA project
• DOE and ASME standards available for nuclear air cleaning and gaseous waste treatment
♦ Engine Exhaust Capture 
• Engine hydrogen exhaust is burned at high temperatures with oxygen, producing O2 rich steam that 
is cooled, condensed, and collected for controlled processing and disposal
• All analyses to date indicate system will reliability and economically accomplish task
• Subscale test project in design with testing planned for 2Q19
Bore Hole Engine Exhaust Capture
Current NTP Project Baseline
Above Ground Scrubber
Background
NTP Ground Test Options
Review of Nuclear Thermal Propulsion Engine Ground Test Options
7
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
NTP Ground Test 
Engine Exhaust Capture System
NTP Project decision to baseline the Exhaust Capture System as the 
NTP engine ground test approach was based on:
1. Its ability to reliably assure containment of potentially liberated reactor 
radionuclides and fuel element debris
2. Availability of existing NASA rocket propulsion test infrastructure 
uniquely suited to accommodate system requirements
3. Decision to baseline LEU reactor engine
• Substantially minimizes the cost of site security and site licensing
Recently initiated NTP Project study is 
re-reviewing Ground Test Options
8
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
• LEU NTP has synergy with current cryogenic fluids system technology development 
(e.g., Mars lander chemical propellant storage)
 Engine operates similar to current liquid rocket engines (LRE) (e.g., expander RL10)
 LEU NTP hydrogen flow-rates for 25,000-lbf engine  similar to current expander cycle engines
 Not a high pressure, complex SSME type propulsion cycle
 Major systems just like O2/H2 and O2/CH4 engine designs
 Similar turbine design, pump and chamber pressures, nozzle-chamber heat loads, nozzle size
LEU NTP Based on Liquid 
Rocket Engine Technology
LEU NTP Technology Risks Reduced Using LRE Knowledge Base
9
Turbomachinery Sized Per RL60 (e.g., RL10 Derivative)
10JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
NTP Ground Test Strategy
Engine Exhaust Capture System
How it works:
• Hot hydrogen exhaust from the NTP engine flows through a water cooled 
diffuser that transitions the flow from supersonic to subsonic to enable stable 
burning with injected LO2 
– Products include steam, excess O2 and  potentially, a small fraction of noble 
gases (e.g., xenon and krypton)
• Water spray and heat exchanger dissipates heat from steam/O2/noble gas 
mixture to lower the temperature and condense steam
• Water tank farm collects H20 condensate and any radioactive particulates 
potentially present in flow.
– Drainage is filtered post test.
• GO2 condenser cools residual gas to LN2 temperatures, condenses O2 and 
noble gasses.
– LOX Dewar stores LO2 and noble gases, to be filtered post test.
Strategy:
• Fully Contain engine exhaust
• Methodically drain containment vessels 
after test to ensure proper filtration
Preliminary system sizing and performance analysis 
of this concept have been completed and no 
operations performance issues have been identified
All system operating pressures and temperatures 
and fluid supply and flow requirements are well within 
existing chemical rocket propulsion test capability 
and experience.
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Engine Exhaust Capture System
Preliminary System Sizing - 25 klbf Engine
11
Notes/Assumptions: 
• 25,000 lbf thrust (500MW)
• 28 lbm/s GH2 Flow.
• Nozzle Exhaust Temp: 2850 K
• Test Duration: 1 hour
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Engine Exhaust Capture System
Conceptual System Design Layout (Full-Scale)
Facility located at SSC’s A3 Test Stand (Current NTP Project Baseline)
• Most of the infrastructure required by the NTP engine exhaust capture ground test facility is already in place: 
• Tower, test cell, propellant, HPIW, data acquisition and controls infrastructure, the Test Control Center, electric power, etc. 
• Major modifications, procurements, and construction work will be required and are captured in a ROM estimate. 
LO2
H2O
IPA
GN2
LO2
LH2
SSC A3 Test Facility
ROM estimate to prepare stand for NTP engine test is under development
12
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Nuclear Thermal Propulsion 
Technology Development
• Evolving Baseline Scope for NTP Ground Test Activities at SSC
• Current, Non-Nuclear Test Project at SSC’s E3 (FY18/19)
• Sub-scale Engine Exhaust Capture System
• Project and funding approved for Phases 1 & 2
• Phase 1 underway with testing in FY19
• Phase 3: Tunable Hydrogen Wave Heater follow-on (FY20)
• Non-Nuclear NTP Engine Development Tests
• Sub-Scale Turbopump Testing, potentially starts in 2-3 years
• Sub-Scale Reactor Simulator, potentially starts in 4 to 6 years
• Nuclear Systems Test
• NTP Engine Testing, start testing in 12-14 years
• NTP engine PowerPack testing
• Full Flow, non-nuclear test (a depleted uranium reactor, hot hydrogen flow) to 
evaluate flow characteristics and structural integrity of the engine before testing 
an actual NTP engine. 
• NTP reactor multi-element test (<20 MW testing vs 500MW of the full scale NTP 
engine)
13
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Nuclear Thermal Propulsion 
Technology Development 
• Evolving Baseline Scope for NTP Ground Test Activities (continued)
• Potential New Facilities
• Zero-power reactor facility/project, a new facility for nuclear reactor element 
quality evaluation
• Engine Maintenance and Disassembly Facility (EMAD), a new facility for engine 
assemble and post test disassembly and evaluation.
14
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
NTP Engine Exhaust Capture System Testing
Nonnuclear Subscale Demonstration Testing
Key Subscale Test 
Program Goals
• Demonstrate efficacy of 
the RECS concept
• Verify H2 afterburning
• Understand system 
startup and shutdown 
transients 
• Assess alternative 
design and technology 
infusion options
• Develop and validate 
test ops procedures
• Supports nuclear site 
licensing regulatory and 
NEPA/EIS processes
• Builds public 
confidence in test 
safety
LO2 
Storage
Desiccant 
FilterGO2 
Chiller
H2 Heat 
Exchanger
• Diffuser
• O2 Injection 
• Spray 
Chamber
• Debris Trap
ECS Nonnuclear
Subscale Test Facility 
Conceptual Design
(at E3/C1)
Hot Hydrogen 
Source
• Nonnuclear RECS Subscale Demonstration Testing is currently 
the #1 priority for augmented STMD/GCD NTP Program funding 
(within the current congressional budget): 
• Phase 1 (FY18-19), $6.7M,  Initial Design, Construction, and GH2 
operating temperature = 1,600R/1,140F
• Phase 2 (FY19-20), $2.0M, GH2 temperature increase to 
5,000R/4,540F
Stennis Space Center
Facility being designed to demonstrate the feasibility, 
safety, efficacy, and affordability of the RECS concept.
15
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
E3RECS3 Project Preliminary Phase 1 and Phase 2 Development Schedule
16
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
JANNAF PIB T&E TIM
at KSC  (08-Nov-17)
Summary
LEU NTP Project will: 
• Determine Low Enriched Uranium (LEU) NTP feasibility and affordability, with good cost and schedule 
confidence, prior to a decision to proceed with full scale development.
• Demonstrate the technology that enables the development of high temperature, minimum erosion/fission 
product release fuel elements using LEU.
• Leverage government, industry and academic expertise and facilities to accomplish technology development 
goals
LEU NTP has synergy with current cryogenic fluids system technology development
• Engine operates similar to current liquid rocket engines
• Major systems just like O2/H2 and O2/CH4 engine designs
• Similar turbine design, pump and chamber pressures, nozzle-chamber heat loads, nozzle size
NTP Engine Ground Test Exhaust Capture System Project baseline based on :
1. Its ability to reliably assure containment of potentially liberated reactor radionuclides and fuel debris
2. Availability of existing NASA rocket propulsion test infrastructure uniquely suited to accommodate 
system requirements
3. Decision to baseline LEU reactor engine
• Substantially minimizes the cost of site security and site licensing
• Subscale ground test demonstration project underway
Recently initiated NTP 
Project study is re-reviewing 
Ground Test Options
17


Low Enriched Uranium (LEU) Nuclear Thermal Propulsion: System Overview and Ground Test Strategy

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