Coote, David

Gerrish, Harold P.

Rauch, Richard T.

NASA Technical Reports Server

David Coote
NASA/Stennis Space Center
Propulsion and Energy Forum, 9-11 July 2018
Duke Energy Convention Center, Cincinnati, Ohio
Ground Test Strategy for a Nuclear Thermal 
Propulsion Engine
RELEASED - Printed documents may be obsolete; validate prior to use.
https://ntrs.nasa.gov/search.jsp?R=20180004502 2019-08-31T15:25:02+00:00Z
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine
Introduction
2
• Nuclear Thermal Propulsion (NTP) is directly relevant to the 
Agency’s vision, mission, and long-term goal of expanding human 
presence into the solar system and to the surface of Mars 
• Provides the fastest trip time of all currently obtainable advanced 
propulsion systems.
• Offers high energy density and a specific impulse roughly double that of 
the highest performing traditional chemical systems. 
• NTP project is funded through the Space Technology Mission 
Directorate’s (STMD) Game Changing Development (GCD) 
program 
• Goal is to determine the feasibility and affordability of a Low Enriched 
Uranium (LEU)-based NTP engine with credible cost and schedule 
confidence.
RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
NASA/GCD – NTP Ground Test Trade ResultsJune 11, 2018
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine
Introduction
• Driving Requirements
 Thrust: 25k lbf
 Burn time: 50 min + 10% margin = 55 min 
burn
 Exhaust temp: 2850K
 Hydrogen flow rate: 28 lbm/s
 Max allowable back pressure: 25 psia
 Meet regulatory requirements for dose rates
3
Preliminary Engine Architecture
• An NTP engine has substantial 
commonality with conventional liquid 
rocket engines. 
• Primary difference is replacing 
combustion of propellants with heating of 
a single propellant via a nuclear reactor. 
• Exhaust may contain radioactive 
particles and noble gases due to a 
reactor anomaly or failure. 
• NASA has developed the Rocket 
Exhaust Capture System (RECS) 
concept to capture and isolate NTP 
engine exhaust from the environment 
to mitigate the related environmental 
risks.RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Date NASA/GCD/NTP  – Title of Presentation
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine
Nuclear Thermal Propulsion Ground Test Strategy
- Rocket 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 and any radioactive particulates potentially 
present in flow
– Drainage is filtered post test
• Heat exchanger-cools residual gases to LN2 temperatures (freezes and 
collects noble gases) and condenses O2
– LO2 Dewar stores LO2, to be drained post test via boil-off
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
RELEASED - Printed documents may be obsolete; validate prior to use.
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine
Rocket Exhaust Capture System
Preliminary System Sizing - 25 klbf Engine
5
Notes/Assumptions: 
• 25,000 lbf thrust (500MW)
• 28 lbm/s GH2 Flow.
• Nozzle Exhaust Temp: 2850 K
• Test Duration: 1 hour
RELEASED - Printed documents may be obsolete; validate prior to use.
SPACE TECH’S GAME CHANGING DEVELOPMENT PROGRAM
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine
Rocket Exhaust Capture System Is Expected to 
Be Built at NASA’s Stennis Space Center (SSC)
6
• SSC’s A3 test facility and its supporting propulsion test infrastructure is 
uniquely suited to accommodate NTP engine system development and 
specifically, the RECS implementation requirements. 
• Most of the RECS major structural elements are readily available.
RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Date NASA/GCD/NTP  – Title of Presentation
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine 7
Rocket Exhaust Capture System
Subscale Test Project
• Phase 1 Objective: Demonstrate the basic performance of the RECS to capture, contain, process, and 
store rocket exhaust effluents
̶ Utilizes an existing, well-characterized  DTF Thruster (~250 lbf) to simplify H2 afterburning
• Phase 2 Objectives: Demonstrate
̶ Stable H2 combustion flame holding following LO2 injection
̶ Back pressure control in the settling and combustion duct sections during NTP engine simulated transient start and 
shutdown H2 flow conditions
̶ Simulation of NTP engine start and shutdown transient flow conditions using a Hydrogen Wave Heater
Project Initiated in 4Q17
at E-3 Test Facility
Testing Begins Jan-19RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Date NASA/GCD/NTP  – Title of Presentation
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine 8
Rocket Exhaust Capture System 
Subscale Test Project
Preliminary System Sizing (10% Full Scale Demonstration)
RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Date NASA/GCD/NTP  – Title of Presentation
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine 9
RECS-Subscale System Layout
at SSC’s E3/C1 Test Facility
CREO Model
RELEASED - Printed documents may be obsolete; validate prior to use.
Nuclear Thermal Propulsion –
Low Enriched Advanced Propulsion
Date NASA/GCD/NTP  – Title of Presentation
Session: NFF-02
Presentation ID: AIAA-2018-4671 Ground Test Strategy for a Nuclear Thermal Propulsion Engine 10
Summary
• NTP is directly relevant to the Agency’s vision, mission, and long-term 
goal of expanding human presence into the solar system and to the 
surface of Mars 
• The RECS concept captures and isolates NTP engine exhaust from the 
environment to mitigate the potential environmental risks.
• SSC has substantial existing infrastructure to support RECS testing.
• A Subscale RECS test project is in work at SSC
• Will demonstrate the basic performance of the RECS to capture, 
contain, process, and store rocket exhaust effluents
• It is a critical element of the NTP project 
• Will support site licensing, proof-of-concept validation, and 
engineering insight to the full scale system.
RELEASED - Printed documents may be obsolete; validate prior to use.


Ground Test Strategy for a Nuclear Thermal Propulsion Engine

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