Nuclear Thermal Propulsion: An Overview of NASA Development Efforts

Ryan Wilkerson| Presented at Missouri S&T | 1031.19

-~-~ . :·

National Aeronautics and Space Administration

https://ntrs.nasa.gov/search.jsp?R=20190033337 2020-04-20T00:58:28+00:00Z

Nuclear Thermal Propulsion

Background

Rocket Thrust Equation

𝑭 = ሶ𝒎 𝑽𝒆 + 𝒑𝒆 − 𝒑𝒐 𝑨𝒆

Equivalent Velocity

𝑽𝒆𝒒 = 𝑽𝒆 +𝒑𝒆 − 𝒑𝒐 𝑨𝒆

ሶ𝒎𝑭 = ሶ𝒎 𝑽𝒆𝒒

How do we assess engine

performance?

Thrust Specific Impulse

Total Impulse

𝑰 = 𝑭∆𝒕 = 𝒎𝑽𝒆

Specific Impulse

𝑰𝒔𝒑 =𝑰

𝒎𝒈𝒐=𝑽𝒆𝒒

𝒈𝒐=

𝑭

ሶ𝒎𝒈𝒐

Thrust is an indicator of how

hard an engine can push

Specific impulse indicates how

efficiently an engine uses propellant

( )

( )

Chemical Engines Advanced Propulsion

SRB-SS SRB-SLS F-1 J-2 RS-25 Ion NEP NTP

Sea Level Thrust (klbf)

2800 3600 1800 109.3 418 - -

Vacuum Thrust (klbf) - - 2020.7 232.3 512.3 2E-5 - 2E-2 25-250

Sea Level ISP (s) 242 269 269.7 200 366 - -

Vacuum ISP (s) - - 303.1 421 452.3 2000-8000 800-1000

Propellant PBAN-APCP PBAN-APCP LO2/RP-1 LO2/LH2 LO2/LH2 Xe LH2

Current engine architectures

Saturn V

Chemical Engines Advanced Propulsion

SRB-SS SRB-SLS F-1 J-2 RS-25 Ion NEP NTP

Sea Level Thrust (klbf)

2800 3600 1800 109.3 418 - -

Vacuum Thrust (klbf) - - 2020.7 232.3 512.3 2E-5 - 2E-2 25-250

Sea Level ISP (s) 242 269 269.7 200 366 - -

Vacuum ISP (s) - - 303.1 421 452.3 2000-8000 800-1000

Propellant PBAN-APCP PBAN-APCP LO2/RP-1 LO2/LH2 LO2/LH2 Xe LH2

Current engine architectures

Space Shuttle

L--

SOLID ROCKET BOOSTER-SRI

Chemical Engines Advanced Propulsion

SRB-SS SRB-SLS F-1 J-2 RS-25 Ion NEP NTP

Sea Level Thrust (klbf)

2800 3600 1800 109.3 418 - -

Vacuum Thrust (klbf) - - 2020.7 232.3 512.3 2E-5 - 2E-2 25-250

Sea Level ISP (s) 242 269 269.7 200 366 - -

Vacuum ISP (s) - - 303.1 421 452.3 2000-8000 800-1000

Propellant PBAN-APCP PBAN-APCP LO2/RP-1 LO2/LH2 LO2/LH2 Xe LH2

Current engine architectures

Space Launch System

Chemical Engines Advanced Propulsion

SRB-SS SRB-SLS F-1 J-2 RS-25 Ion NEP NTP

Sea Level Thrust (klbf)

2800 3600 1800 109.3 418 - -

Vacuum Thrust (klbf) - - 2020.7 232.3 512.3 2E-5 - 2E-2 25-250

Sea Level ISP (s) 242 269 269.7 200 366 - -

Vacuum ISP (s) - - 303.1 421 452.3 2000-8000 800-1000

Propellant PBAN-APCP PBAN-APCP LO2/RP-1 LO2/LH2 LO2/LH2 Xe LH2

Current engine architectures

Mars Transit VehicleIon Engine

There are many uses for nuclear power in

space

8

Electricity Generation to Power ThrusterDirect Heating of Propellant

to Provide Thrust

Nuclear Thermal PropulsionNuclear Electric PropulsionRadioisotope Thermal

Electric Generators

)He alpha patl!Cle

Nuclear thermal rocket engine

Note: results based on

• 1000 psia chamber

pressure

• 2700 K chamber

temperature

• 150:1 nozzle area ratio

Specific Impulse (revisited)

𝑰𝒔𝒑 =𝑭

ሶ𝒎𝒈𝒐=

𝟏

𝒈𝒐

𝟐𝜸

𝜸 − 𝟏

𝑹𝑻

𝑴𝟏 −

𝒑𝒆𝒑𝒄

𝜸−𝟏𝜸

𝑰𝒔𝒑 ∝𝑻

𝑴

-NTP engines produce thrust by heating

propellant using a nuclear core

-propellant temperature directly correlates

to Isp

-core power and temperature determine

exhaust temperature and therefore Isp

NUCLEAR REAClOR

CONlROL DRUM

-J--H -1-f

~ .§ 0

= "§ g ~ i

950

900

850

800

750

700

650

600

550

500

450

400

350

300

250

~ Cl. ~

1500Nuclear Thermal Propulsion with Various Propellants

- H2

1300 - NH3

1100 - H20

- CO2

900

700

500

300

100

NTP mission proposals, from the moon

to Mars

Reusable Lunar Transfer

Vehicle using Single 75 klbf

Engine -- SEI (1990-91)

“Bimodal” NTR Earth Return Vehicle using Clustered

15 klbf / 25 kWe Engines -- Mars DRM 1.0 (1993)

Expendable TLI Stage

for First Lunar Outpost

Mission using Clustered

25 klbf Engines -- “Fast

Track Study” (1992)

Artificial Gravity BNTR Crewed Transfer Vehicle also using

Clustered 15 klbf / 25 kWe Engines -- Mars DRM 4.0 (1999)

Design Transition from Single Large NTR to Clustered Smaller Engines Supplying Modest Electrical Power

Zero-Gravity Crewed MTV uses 3 - 25 klbf

NTR Engines & PVA Auxiliary Power – Mars

(2009)

Historic Nuclear Thermal Propulsion

Efforts

Rover/NERVA* era (1955-1972)

• 20 Rocket/reactors designed, built & tested at cost of ~1.4 B$

• Engine sizes tested

25, 50, 75 and 250 klbf

• H2 exit temperatures achieved

2,350-2,550 K (Pewee)

• Isp capability

825-850 sec (“hot bleed cycle”tested on NERVA-XE)

850-875 sec (“expander cycle”chosen for NERVA flight engine)

• Burn duration

~ 62 min (NRX-A6 - single burn)

> 3.5 hrs (NRX-XE: 28 burns / accumulated burn time)

• Engine thrust-to-weight

~3 for 75 klbf NERVA

• “Open Air” testing at Nevada Test Site-----------------------------

* NERVA: Nuclear Engine for Rocket Vehicle

Applications

The NERVA Experimental Engine (XE) demonstrated 28

start-up / shut-down cycles during tests in 1969.

Rover/NERVA* era (1955-1972)

• 20 Rocket/reactors designed, built & tested at cost of ~1.4 B$

• Engine sizes tested

25, 50, 75 and 250 klbf

• H2 exit temperatures achieved

2,350-2,550 K (Pewee)

• Isp capability

825-850 sec (“hot bleed cycle”tested on NERVA-XE)

850-875 sec (“expander cycle”chosen for NERVA flight engine)

• Burn duration

~ 62 min (NRX-A6 - single burn)

> 3.5 hrs (NRX-XE: 28 burns / accumulated burn time)

• Engine thrust-to-weight

~3 for 75 klbf NERVA

• “Open Air” testing at Nevada Test Site-----------------------------

* NERVA: Nuclear Engine for Rocket Vehicle

Applications NRX-A6 (1972): Hydrogen exit temperature = 2556 K

1 hr.

Rover/NERVA Development Overview

Geometry – Extruded Hexagonal

Length: 51 in.

Flat-to-Flat: 0.75 in.

19 Coolant Channels

Fabrication: Extrusion and Sinter

Fuel Compound

UO2

UC2

Emerging Fuels

(U,Zr)C fuel web

(U,Zr)C solid solutionHighest level of development status for any fuel with

significant remaining challenges

UC 2 Parll<;les/Graphltc M~trhc PyC Coated uc2 Snhcrcs/Gr aphtte Matrl~ Ca rblde/Graohl tc Composite

Carb ide Solld Solution

NbC coatings • ZrC coatings ... ZrC + Mo coatings

Two major failure mechanisms were

discovered through engine testing

Mechanical FailureCorrosion

15

Graphite Matrix: Post Exposure

NbC ZrC GraphiteComposite

(U,Zr)C-C

CTE

(µm/m·K)7.0 - 7.2 7.6 - 7.7 3.0 6.0 - 6.7

,.o

w 0.8 -1-.. a: z 0 iii 0.6 -0 a: a: 8 w 0.4 -> .: .. .., w a: 0.2 -

NRX-A2-A3

1965

NRX-A&XE

1966 1967 1968 1969

TYPICAL WANL

TYPICAL Y-12

A4 AS COMPARISON OF A-4 &AS CRACK PATTERNS @ STATION 20

200X

Historic U.S. Cermet Fuel Development

(1957-1968)

ANL Nuclear Thermal Propulsion Ceramic Metall ic (cermet) Fuels W-UO2 (net-shape HIP, prismatic)

Anem11tyefm~ 4tnu111 can comp,nKJts

(1962 - 1966)

=[

Nose Piece Reflector

f i t . ).10 - "-"l•f e., ...... , RMCIO< !,,ti ooml~. ·--... ,~ t.-i.,.PUl1-258, "'4-ll,2SA. I

0-Type Assembly

Tllfles upill'J In 11a t-1upresswrc:,c1e

GE·NMPO

E-Type Anembly

Tllb8sc:oq ntJstd 0ntopku' klhol ·f U ~rtuUrt(yClll

(Pins su~stCjl,lent)J Inched aul al tubl:sj

Cermets fail from the inside out due to high

temperature instability of ceramic fuel particles

60 vol%

UO2

=

After Hot Hydrogen Exposure

Pre-Test Post-Test

W-d

UO

2cerm

ets

Mo

W-d

UO

2cerm

ets

-Oxide and nitride ceramic fuels susceptible

to H2 corrosion

-necessitates the need for fuel cladding

Before Before

After Hot Hydrogen Exposure

Successfully developed cermets prevented free oxygen

loss and thermal stresses

18

Mass Loss Mitigation Parameters

- W-alloy Claddings

- Gd2O3 and ThO2 stabilizers

- High fuel density to reduce free U, O

migration

- Eliminate interparticle connectivity

- Spherical particles to allow for favorable

interfaces at grain boundaries

- UO2 → UN fuel particles

i i i, 30

~ _,_

f 20 .. Ji "'ii, :II ... ( l1ungsten tlii!l lalllil'T(. 0. 003 iJl!.

/ 011 1 ·r fas, edgl fillln unelllll

f

2 • ~ 8 10 TciJl tes.ttlme; hr

1..., ...... . • ,

l6DOlJ:102Gl7JOOl'XIO 2100 XO> l900 -lO

o.,.._P • SIO (e•)~-

-.,-

(R.t 1) -r--1 i--..

>- ..._..,......,.1P • 3l.2 (e•)~ - -r--~

·-== I= (11.f.1)

! 1 .,-' -.....

1

j .. -.

. .,­..

~

H,,..._ p • 'lT7 1...,) -10.CW:/ l00

..... ~

i"-.. !§

-:::-I I ~

--::::r: 16 .. •• u ••

Rec.,.C..l t....,.-. JO'/ •I(

f l9. S-C..,.,la• ef ~ IN uefflcle1111 fer 11itra,._, .. ,i,,_,.., -4 llll'ffN .__.. INC•CUI lllflf1 '"

12

Solid-solution carbides have high melting

temperature and exhibit high temperature

stability

ZrC rich solid solutions show excellent

resistance to hydrogen corrosion

5 X IQ--4 .------.----,----~---,------r----.--,

Ill IQ-5 I\( E ~ "' .. -·E -w 1-<t a:: (f) (f) 0 _J

(f) f/)

<t ,o-6 :?

3095 K

--~- 2980K

2880 K

\ •~ .... --=.- 2770K

PURE HYDROGEN FLOW • 730 scfh

Ua.os Zro.95 C1.01

Zl ,o-7 0'-----2L_ __ ...;4L-----J6L----Je ___ ..1.,o---~,z~_,

TOTAL PERCENT MASS LOSS (TPML)

3450

NbC 00--c'=---~--c>3-=-o-- 4>--co~___,..50~----,,G-=-o-~1'-=o--sc'-co~___,_9-=-o-_,101§>2,c {3505°) COMPOSITION ZrC {MOLE PERCENT) (34 95 °C )

40QQ ..-------r--...-----r--,---,------,----,----,--,-----,

u 0 3500 .£ .... . !: 0 0. Cl C i 30001-----+-- --1--- ~...i--~~-At-----t

20 40 mol'/,UC

60 BO 100

History: USSR RD-0410 Carbide Fuel Development

Geometry – ‘Twisted Ribbon’

Length: ~100 mm

Diameter: 2 mm

Attempt to maximize heat transfer while

maintaining fuel integrity

Fuel Compounds

Fuel composition was focused on

maximizing the operating temperature

of the fuel

Carbide

• (U,Zr)C

• (U,Zr,Nb)C

• (U,Zr,Ta)C

Carbonitride

• (U,Zr)C,N

The NTP fuel form development efforts of the former Soviet Union was comparable to United States

efforts if not exceeded that of the United States.

Reported ternary-carbide fuel performance of operation at 3100 K for up to 1 hr.

Carbide fuels also experience the most failure in

the mid-band region where power densities are

high and ductility low

21

Fueled Region

T

q

Ductile Failure

Highest

Rate of

FailureBrittle Failure

3000

T, K

2500

2000

1000

500 100 200

1.0

0.6

0.4

0.2

300 400 500 L , mm

History: US Carbide Fuel Development

NERVA/RoverCarbide Fuels

(1955 – 1972)

Carbide (U,Zr)C fuels were tested in NF-1 and

survived exposure to over 2700 K for 109

minutes under flowing hydrogen and irradiation.

Fuel element architecture that the Rover/NERVA

program used for all their fuel compositions

Hot Hydrogen Hot Hydrogen Prototypic Prototypic Static Testing Thermal Cycling Irradiation Testing Engine Testing

✓ ✓ ✓

Aluminum Tube

Overview of NTP Fuel Timeline

1950 1960 1970 1980 1990 2000 2010 2020

NERVA/Rover

(1955 – 1972)

Cermet Development

ANL, NASA LeRC, GE 710

(1962 – 1968)

SNTP

(1987 – 1993)

USSR Solid-Solution Carbide

Fuels (1955 – 1993)

AES NTP, GCD NTP

(2010 – 2019)

Graphite Matrix

Composite

Solid Solution Carbides

Mo-UO2 hot-rolled &

sintered

W-UO2, W-UN

sintered

Coated

Particle

Cermet,

Carbide,

Emerging Fuels

Solid Solution Carbides

Solid Solution Carbonitrides

Carbonitride Cermets

Mo-U02 hot-rolled & intered -U02, W-UN

sintered

Nuclear Materials Group – NASA MSFC

• Marvin Barnes

• Omar Mireles, Ph.D

• Omar Rodriguez, Ph.D

• Jhonathan Rosales, Ph.D

• Brian Taylor

• Martin Volz, Ph.D

• Ryan Wilkerson, Ph.D

Thank you!