Belvin, Anthony

Borowski, Stan

Clement, Steven

Doughty, Glen

Emrich, Bill

Gerrish, Harold

Hickman, Robert

Houts, Mike

Kim, Tony

Mitchell, Sonny

Power, Kevin

Scott, John

NASA Technical Reports Server

1The NASA Advanced Exploration Systems 
Nuclear Thermal Propulsion Project
Mike Houts, Sonny Mitchell, Tony Kim, Bill Emrich, Robert 
Hickman, Harold Gerrish, Glen Doughty, Anthony Belvin, 
Steven Clement, Stan Borowski, John Scott, Kevin Power
Presented at:
Propulsion and Energy Forum 2015
https://ntrs.nasa.gov/search.jsp?R=20150016563 2019-08-31T06:25:39+00:00Z
Nuclear Thermal Propulsion (NTP)
 Nuclear thermal propulsion (NTP) is a fundamentally new capability
• Energy comes from fission, not chemical reactions
• Virtually unlimited energy density
 Initial systems will have specific impulses roughly twice that of the best 
chemical systems
• Reduced propellant (launch) requirements, reduced trip time
• Beneficial to near-term/far-term missions currently under consideration
 Advanced nuclear propulsion systems could have extremely high 
performance and unique capabilities
 The goal of the AES NTP project is to establish adequate confidence in the 
affordability and viability of NTP such that NTP is seriously considered as a 
baseline technology for future NASA human exploration missions 
2
AES NTP Project Recent Activities
Fabrication of 16” coated graphite composite fuel elements (hafnium 
surrogate in place of uranium)
Fabrication of short (<6”) W/UO2 cermet fuel element segments 
(depleted uranium) / testing in Compact Fuel Element Environmental 
Tester (CFEET)
Completion of Nuclear Thermal Rocket Element Environmental 
Simulator (NTREES) 1.2 MW upgrade
Preparation for NTREES test of 16” coated graphite composite fuel 
element (hafnium surrogate) by end of FY15.
Additional AES NTP project emphasis on potential early flight 
demonstration engine using highly enriched uranium (HEU) fuel.  
Coated graphite composite selected as the “lead” fuel for that engine.
Additional work related to early flight (or ground) demonstration 
includes facility identification, schedule generation, and cost 
estimation.
3
Short, 7 Channel W/UO2 Element Fabricated and Tested in 
Compact Fuel Element Environmental Tester (CFEET)
CFEET System 50 kW Buildup & Checkout
Initial Testing of Short W/UO2 Element
Completed CFEET system
Left: View looking down into the CFEET 
chamber during shakeout run 1.  BN 
insulator and bright orange sample inside
Above/left: Pure W sample 
post shakeout run 2.  Sample 
reached melting point (3695K)  
and was held in place by the 
BN insulator.  
CERMET W Powder Coated UO2 HIP Sample
Micrograph of W powder coated UO2 HIP sample 
showing improved distribution of UO2 (dark phase) 
spheres in the W (light phase)matrix.
Uranium Phase (blue) W Phase (red)
UO2
W
Continuous W Matrix
SEM phase map of W powder coated UO2 HIP sample showing improved 
distribution of UO2 (blue phase) spheres in the W (red phase) matrix. 
Crimp and sealing of W powder 
coated UO2 sample in glovebox
CERMET W-UO2 6” 19-Hole Fuel Sample
Images showing the 6” long 19-hole W-UO2 HIP 
can assembly prior to, during, and after welding
Net Shape 
W Cladding
W Coated 
Mo Rods
19 Hole HIP can W-UO2
powder fill in glovebox
HIP Tooling
NTP CERMET Fuel Element Development
• Completed fabrication, assembly, welding of 
two 4.5” HIP cans for pure W samples 
(one with internal cladding/one without)
• Change to 4.5” from 6” was due to availability of 
the W cladding
• Filled two HIP cans with pure W powder
• Achieved ~65% packing density in each can
• Completed HIP cycle for the pure W sample 
with internal cladding
• Sample appears to be near full consolidation 
without can failure
• Pure W samples will be used to evaluate 
shrinkage, etching, and machining
• Full length HIP can for pure W sample has 
been fabricated
• March, 2015 AES NTP project decision to 
defer additional cermet fuel work until FY16 
or beyond.
HIP can assembly for pure W samples prior to welding
Welded HIP can 
assemblies for 
pure W samples 
Pure W sample being loaded into HIP vessel for consolidation. 
Sample is buried in Al2O3 grit; Provides structural support
Pure W sample 
with internal 
cladding after HIP 
consolidation 
Compact Fuel Element Environmental Test (CFEET) 
System and Etch System Upgrades
Thermal Model of W susceptor and BN Pedestal
W susceptor and BN Pedestal
Full Length Fuel Element Etch System
ORNL Graphite Composite Fuel Element Development
9
MSFC High Temperature Furnace
MSFC High Temperature Furnace. 
Licensed for depleted uranium
ORNL Fuels Dev. 
Team from left to 
right: Jim Miller, 
Brian Jolly, Mike 
Trammel.  ORNL 
multi-zone coating 
furnace shown in 
background.
Initial ORNL graphite composite samples after the final heat 
treatment to 2700 C. Long sample is a section from an 
extrusion run. Short one is run out material left over from 
extrusion run. (Heat treated to have some extra material)
Above and left: 
Graphite sample 
prior to heat 
treatment
Coated Graphite Composite Development (ORNL) 
Above: Members of Oak Ridge National 
Laboratory fuels team with the graphite 
extruder; Left: Graphite extruder with 
vent lines installed for DU capability
Above and Left:  
Extrusion samples  
using carbon-
matrix/Hf blend 
.75” across flats, 
.125” coolant 
channels
ZrC coating
Uncoated graphite
Graphite Substrate
Bottom face of 
Substrate
Beginning of internal channelAbove: Test Piece highlighting ZrC Coating
Right: Coating primarily on external surface
Right: Layoff 
base / 
Graphite 
insert
Backscattered SEM EDS analysis - Zr (green), Hf (blue)
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ORNL Graphite Composite Development
Testing in NTREES
12
Above left & right: NTREES in preparation for graphite FE testing
• NTREES has been modified to allow much higher 
power operation – achieved > 200kW
• Check out testing uncovered design deficiencies 
which limited the power that could be applied to test 
elements
• Design deficiencies have been corrected
• Modifications to coils needed prior to very high power 
testing – pursuing designs to allow greater test fidelity
• NTREES fully operational for testing fuel elements 
with prototypic surrogate or depleted uranium loading
1.2 MW induction heater and DAQ system
Induction coil with and without insulation
Nuclear Thermal Rocket Element Environmental Simulator 
(NTREES)
NTREES Phase 1 50kW (2011)
NTREES Phase 2 – 1MW Upgrade (2015)
New Cooling Water System now provides 2 
separate systems that cool induction coil and 
power feedthrough, induction heater and H2N2
mixer respectively
Coil and Feedthrough Assembly
New Coil is
Heavily Insulated
and Rugged
Old Coil was
Uninsulated and
Somewhat Fragile
General Description:
• Water cooled ASME coded test vessel rated for 1100 psi 
• GN2 (facility) and GH2 (trailer) gas supply systems
• Vent system (combined GN2/GH2 flow)
• 1.2 MW RF power supply with new inductive coil
• Water cooling system (test chamber, exhaust mixer and 
RF system)
• Control & Data Acquisition implemented via LabVIEW 
program
• Extensive H2 leak detection system and O2 monitoring 
system
• Data acquisition system consists of a pyrometer suite for 
axial temperature measurements and a mass 
spectrometer
• “Fail Safe” design
Observations / Summary
Since FY 2012, the NASA AES NTP project has made 
progress in certain key areas. 
Safety is the highest priority for NTP (as with other 
space systems).  After safety comes affordability.
No centralized capability for developing, qualifying, 
and utilizing an NTP system.  Will require a strong, 
closely integrated team.
Tremendous potential benefits from NTP and other 
space fission systems.  No fundamental reason these 
systems cannot be developed and utilized in a safe, 
affordable fashion.
14


The NASA Advanced Exploration Systems Nuclear Thermal Propulsion Project

The NASA Advanced Exploration Systems Nuclear Thermal Propulsion Project

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