Oral Presentation/Viewgraphs Summary - NASAconsidering a 100 kWclass CBC system coupled to a gas-cooled fission reactor. Currently, CBC technology is being explored for Fission Surface

Oral Presentation/Viewgraphs Summary:

NASA has been involved in the development of Closed Brayton Cycle (CBC) power conversion technology

since the 1960's. CBC systems can be coupled to reactor, isotope, or solar heat sources and offer the

potential for high efficiency, long life, and scalability to high power. In the 1960's and 1970's, NASA and

industry developed the 10 kW Brayton Rotating Unit (BRU) and the 2 kW mini-BRU demonstrating technical

feasibility and performance, In the 1980's, a 25 kW CBC Solar Dynamic (SO) power system option was

developed for Space Station Freedom and the technology was demonstrated in the 1990's as part of the 2

kW SO Ground Test Demonstration (GTD) . Since the early 2000's, NASA has been pursuing CBC technology for

space reactor applications. Before it was cancelled, the Jupiter Icy Moons Orbiter (HMO) mission was

considering a 100 kWclass CBC system coupled to a gas-cooled fission reactor. Currently, CBC technology is

being explored for Fission Surface Power (FSP) systems to provide base power on the moon and Mars. These

recent activities have resulted in several CBC-related technology development projects including a 50 kW

Alternator Test Unit, a 20 kW Dual Brayton Test Loop, a 2 kW Direct Drive Gas Brayton Test Loop, and a 12

kW FSP Power Conversion Unit design.

https://ntrs.nasa.gov/search.jsp?R=20120016632 2020-04-29T21:01:31+00:00Z

National Aeronautics and Space Administration

A Summary of Closed Brayton Cycle Development Activities at NASA

Lee Mason

NASA Glenn Research Center

Supercritical CO2 Power Cycle Symposium

April 29-30, 2009

Pre-Decisional , For Discussion Purposes Only

•

www.nasa.gov 1

Outline • National Aeronautics and Space Administration

• Space Power Conversion Options

• Closed Brayton Cycle Timeline

• Brayton Development Projects - Brayton Rotating Unit & Mini-BRU

- Solar Dynamic Brayton

- Brayton Concepts & Studies

- Jupiter Icy Moons Orbiter

- 2 kW Brayton Testbed

- Dual Capstone Brayton Loop

- Fission Surface Power

- Direct Drive Gas Brayton

- Technology Demonstration Unit

- Full-scale Power Conversion Unit

Pre-Decisional , For Discussion Purposes Only www.nasa.gov 2


Space Power Conversion Options

• Closed Brayton Cycle - Mature Technology with

High Power Potential

• Free-Piston Stirling - High Efficiency & Scales

Well to Low Power

• Organic or Liquid-Metal Rankine - Potential for Low Mass at

High Power, but Material & Fluid Mgmt Issues

• Thermoelectric - Flight Proven with Long

Life , but Low Efficiency

• Thermionic - Extensive Database, but

Life Issues Remain


30

- 25 ~ 0 ~

• >-u 20 I:

.~ u :E 15 W

10

5

Ni-Based -,-__ Re~~?ct()ry ;-_---,-_Ceramics Superal/oys Composites

<> Rankine SNAP-50

<> Segmented High T TE

LowT

<> PbTe

SiGe <> Thermo-electric

: Thermionic

1000 1200 1400 1600 1800 2000

Peak Temperature (K)

www.nasa.gov 3


Closed Brayton Cycle

• • • • • • Liquid

coolant • • • • • • • • • • • • .. ,.

Pump

Pre-Decisional, For Discussion Purposes Only

AC or DC

TurboalternatorCompressor

Inert gas working

fluid

•

www.nasa.gov 4


BRU esc Timeline •

BIPS SP-100 Demo DIPS JIMO

( I I I I I I I )

1970 1980 1990 2000

Mini-BRU SP-100 Studies

SSF SD FSP

SDGTD



Brayton Rotating Unit

• First-ever Closed Brayton Cycle (CBC) power conversion system for space (1968-76)

- 4 BRUs Fabricated by AiResearch and Tested at Lewis Research Center

- Included Brayton Heat Exchanger Unit (BHXU) combined Recuperator and Cooler

• BRU Program Successfully Demonstrated: - Manufacturing & Assembly - Jacking Gas Startup - High Conversion Efficiency (>25%)

Material Compatibility - Tilt-Pad Bearings - Extended Life: 38000 Hrs Operation on One

Unit Without Degradation, Approx. 50000 Hrs Total on Four Units

• Performance Parameters: - Alternator Output 2.25 to 15 kWe - Turbine Inlet Temp 1144 K (1600 F) - Compressor Inlet Temp 300 K (80 F) - Compressor Exit Pressure 310 kPa (45 psia)

36000 RPM, 1200 Hz, 208 V - 65 kg BRU, 200 kg BHXU


BRAYTON POWER SYSTEM

Tu rboalternator BHXU

BRU Life Test

www.nasa.gov •


Mini-BRU

• Mini-BRU and Recuperator developed for use with Modular Isotope Heat Source (1974-78)

Built by AiResearch, Tested by Lewis Major Differences from BRU: Lower Power, Foil Bearings, Internal Stator Cooling

- Interchangeable Superalloy and Refractory Turbine Plenums Fabricated

• Led to 1.3 kW Brayton Isotope Power System (BIPS) development (DOE)

- No Flight, but 1000 Hr Workhorse Loop Test

• Mini-BRU Successfully Demonstrated: - High Efficiency (>25%) at Lower Power - Foil Bearings - Alternator Motoring Startup - Leak-Free Recuperator Designs

• Performance Parameters: - Alternator Output 650 to 2100 watts - Turbine Inlet Temp 1144 K (1600 F) - Compressor Inlet Temp 300 K (80 F) - Compressor Exit Pressure 730 kPa (106 psia) - 52000 RPM, 1733 Hz, 67 V - 17 kg mini-BRU, 59 kg Recuperator


Turboalternator

•

BIPS Workhorse

Loop

Mini-BRU Recuperator

www.nasa.gov 7


Solar Dynamic Brayton - Space Station Freedom • • 25 kW Solar Dynamic Power Module for

Space Station Freedom (1986-91) - Part of Hybrid PV/SD Power System - Reduced Life Cycle Costs Compared to

Photovoltaic/Battery System - 15 year On-Orbit life - Man-Rated System

• Phase C/O Design Completed - Higher Risk Components Built & Tested

(e.g. Concentrator, Heat Receiver) - Power Conversion Unit Considered Low

Risk due to BRU Heritage

• Performance Parameters - Alternator Output 36 kWe - Cycle Efficiency 27% - Turbine Inlet Temp 1034 K (1400 F)

Compressor InletTemp 338 K (148 F) Compressor Exit Pressure 560 kPa (81 psia)

- 32000 RPM, 120V 104 kg Turboalternator-Compressor, 162 kg Recuperator, 85 kg Gas Cooler


----

Turboalternator

,::..

......... -

SD Flight Configuration

.. _-

Recuperatorl Cooler

www.nasa.gov 8


Solar Dynamic Ground Test Demonstration • • 2 kW Solar Dynamic Ground Test

Demonstration (1994-98) - Congressional Ear-Mark Following

Cancellation of SO Option for SSF - Full End-to-End System Test in Solar

Thermal-Vacuum (TRL6) - Government/Industry Team: NASA Lewis,

Allied Signal, Harris, Loral-Vought, Rocketdyne

• Extensive Test Program - 33 Separate Tests, 372 LEO Orbit Cycles - 800 Hours of Operational Experience - No Performance Degradation

• Led to Joint US/Russian 2 kW Mir SO Flight Demo (1996-98)

- Shuttle Delivery Mission Re-directed to Mir Re-supply

• Multiple Brayton Unit Configurations - Mini-BRU with 120V Rice Alternator - SO Mir Development Unit with 28V

Permanent Magnet (PM) Alternator - SO Mir Unit with Rewound 120V PM

Alternator


Heat Receiver & Power Conversion Unit

View from Solar Sim.

Window Port

Rotor Components -

www.nasa.gov 9


Brayton Concepts & Studies • • 20 kW Brayton for Near-Term

SP-100 Reactor Flight Demonstration Mission

• 6 kW Dynamic Isotope Power System (DIPS) for Air Force Boost Satellite Tracking System (BSTS)

• 500 watt to 2.5 kW DIPS for Space Exploration Initiative (SEI)

- Science Rovers

- Surface Utility Power

• 100 to 550 kW SP-1 00 Brayton for Lunar and Mars Surface Missions

• Bi-Modal Nuclear Thermal Rocket with 25 to 50 kW Brayton

Pre-Decisional, For Discussion Purposes Only

6 kW DIPS

Bi-Modal NTR

550 kW SP-100 Brayton For Lunar Surface

www.nasa.gov 10


Jupiter Icy Moons Orbiter (JIMO) Brayton

liquid-Metal Reactor with 1+1 Brayton (100 kWe)

Gas-Cooled Reactor with 2+2 Brayton (200 kWe)


liquid-Metal Reactor with 2+2 Brayton (135 kWe)

www.nasa.gov "


2 kW Brayton Testbed

• 2 kW "Space-Like" Closed Brayton Unit for JIMO Risk Reduction - Brayton Converter from SD GTD;

Formerly "Mini-BRU"

- Electrical Shell & Tube HeliumXenon Gas Heater

- Commercial Ethylene Glycol Chiller

- 120 Vdc Electrical Controller & Parasitic Load Radiator

- Alternative 1100 Vdc Controller for Electric Propulsion Testing

• Recent Testing Completed: - Performance Mapping (Jun (02)

- Ion Thruster Demo (Dec (03)

- Mech. Dynamics Test (Nov (04)

- Thermal Transients Test (Sep (05)


Evaluate Transient Measure Mech. Thermal Response Vibrations & Validate Codes Demonstrate & Validate Codes

HV Distribution & EP Thruster

I nteg ration

www.nasa.gov 12


Dual Capstone Brayton Loop

• System Designed and Built by Barber Nichols, Arvada CO - Uses Two Commercial Capstone Micro

Turbine Generators - Modified for Closed-Loop Operation - Common Nitrogen Gas Loop; No Isolation

Valves - Shared (180 kW) Electrical Resistance

Heater; Water Cooling • First-of-a-Kind Test System

- Representative of Direct-Gas Reactor with redundant Brayton units

- Permits evaluation of operational interactions

• GRC Testing Completed May-DB - Operated up to 22 kW Total Power, 950K

Turbine Inlet, 90000 rpm - Equal & Unequal Shaft Speeds - Single and Dual Unit Operation - Staggered & Simultaneous Startup - Analytical Model Validation

Pre-Decisional , For Discussion Purposes Only www.nasa .gov 13


...

Dual Capstone - Equal Shaft Speeds

25.--------.--------,--------.--------,--------.--------.

20

I I I I

I I ________________ l ________ J ________ J __ _ I I I I I I

I I --------~--------+--------~--

I I I I I I I I I I

Reference Condition 1=..:..:.;.;=.;-'i - - - -- ---

~ o 10 Q.

I --------,-------- I I -----------------r--------I

g o I-

5 --------- -----~--------~---------~--------I

O+--------T--------T--------T--------.--------.------~

40 50 60 70 80 90 100

Shaft Speed (krpm)

-{)- DBPCS 950 K HET

__ CCSS 950 K HET

-0- DBPCS 895 K HET

....... CCSS 895 K HET

-c- DBPCS 840 K HET

-..... CCSS 840 K HET

DBPCS=Dual Brayton Power Conversion System; CCSS=Closed Cycle System Simulation

Pre-Decisional , For Discussion Purposes Only www.nasa.gov ,.


Dual Capstone - Unequal Shaft Speeds

12 ,--------.---------.--------.--------.---------.--------.

10

-_ -_ -_ -_ -_ -_ -_ -_ -_:f-~-_-~- ~- -~-~-:-~-~'-~-~- ~- ~- -~-~-~-~-t'-~-;-;- ;- -~-~-~L: ::~~r: ---------I 8 1 -1----- ---~----------~ 1 __ 1

- 1 ::J 1 1

Retererce Condition 1 1 ~ 6 _________ ~---------L-

-------------------------~---------

o 1

! 4 : Q.

1 I

1 1 I I I I

- - - 1- - - - - - - - - -1 - - - - - - - - - -1- - - - - - - - - -I - - - - - - - - -

1 1 1 1 1

1 2 - - - - - - - - - - r- - - - - - - - - - r- - - - - - - - - -1- - - - - - - - - -1- - - - - - - - - -1- - - - - - - - -

1 1 1 1 1

o +---------1---------1---------~--------_r--------_+--------~ 40 50 60 70 80 90 100

Variable Speed PCU Shaft Speed (krpm)

• .-fr- DBPCS

Constant Speed PCU

-.-CCSS Constant Speed PCU

~DBPCS Variable Speed PCU

...... CCSS Variable Speed PCU

DBPCS=Dual Brayton Power Conversion System; CCSS=Closed Cycle System Simulation

Pre-Decisional , For Discussion Purposes Only www.nasa .gov 15


Fission Surface Power Concept

• Modular 40 kWe System with 8-Year Design Life suitable for (Global) Lunar and Mars Surface Applications

• Emplaced Configuration with Regolith Shielding Augmentation Permits Near-Outpost Siting «5 rem/yr at 100 m Separation)

• Low Temperature, Low Development Risk, Liquid-Metal (NaK) Cooled Reactor with U02 Fuel and Stainless Steel Construction

Radiator P",.",n.

-.-------------16m----------------

Main Radiators

Cavity Radiators

NaK Pumps !i:iQ~~~;';':., Shield

Reactor

r 4m

1

Pre-Decisional, For Discussion Purposes Only www.nasa.gov '6


Direct Drive Gas Brayton

• 2 kW Closed Brayton Power Conversion Unit from Solar Dynamic Ground Test - Modified for Prometheus-JIMO Power

Conversion tests - Flight-like Brayton: 900K Turbine Inlet,

300K Compressor Inlet, 52000 rpm, HeXe Working Fluid

• Direct Drive Gas (DOG) Reactor Simulator from MSFC - Designed & tested during JIMO with non

representative heat sink - Pin heater elements in core-like bundle - Stainless steel clad & vessel

• Completed integration & initial checkout testing at GRC Dec-08

• Full performance characterization and controls test completed in Feb-09

- Temperature Control - Simulated Reactor Feedback

Pre-Decisional , For Discussion Purposes Only www.nasa.gov "


DOG Brayton Reactivity Simulations • Response to Brayton Speed Decrease

OOOO~-,~,-,---~~~~~~~~ I Heater Inout Power C'Ne)

--- - -

600 I - Alternator OJtput PowerC'Ne)

400

200 , , ,

:['---, -, ,-=-, ,"'-~&-.,T=-{: 1 0.010 ! j ~E~ t------.. ------, ~ L = Rw~'=

-0.010 ,~: ,-o 10 20 30 40 50 60 70 80

Time (rnn)


Response to Neg. Reactivity Insertion

OOOOr-~-'--~--~~~~~--~~ I Heater Input Power C'Ne)

6000 r 4000 r

400

2OOt---------------J

o 20

, I

40 60

Time (min)

80 100

www.nasa.gov I.

Technology Demonstration Unit - Objectives

National Aeronautics and Space Administration • • • Reduce FSP Development Risk • Benchmark Analytical Codes

• Verify System-Level Performance in Realistic Environment

• Gain System Operations Experience for the NASA/DOE Team

• Characterize Component Performance in a System Context

• Expand Industrial Infrastructure for Component Design and Fabrication

• Obtain Operational Data under SteadyState and Transient Conditions

• Obtain As-Built Mass and Cost Data

• Provide Tangible and Measurable Technology Milestone • Develop System Control Methods

" -"

111111111111 III~III 111111111111

\ H2O - 12kWe ,-,\.6m (-375K)

- I

111111111111 111111111111 1111111111 11

Olav. 1

~ , II ~oK J .t-i " (-8S0K) W ( , ' I:. - J -48 kW, , 'Sim /

,lbEMl1 B-b ©!© ~)C: ~ -~

-2.1 It 1.7 m ell .

, '@} GRC Vacuum Facility #6 : ~ _ _ DIll Power , Acq. &: - - - Mpu ~ - - - - - - - - Control &:DiII.


Notional TDU Test Layout in GRC

Vacuum Facility #6

www.nasa.gov '9

.

Full-scale Power Conversion Unit Contracts e ' National Aeronautics and Space Adm inistration

• Two Phase I Design & Analysis contracts awarded May-OB - Sunpower (Stirling) and Barber Nichols (Brayton) - Approach provides parallel and diverse design path for Full-scale (12 kWe) PCU for

FSP Technology Demonstration Unit (TDU) - Both Final Design Reviews completed in Apr-09 at GRC - Only one contractor will be selected for Phase II Fabrication & Test (Summer 2009)

Flil - ~ Station r------------ -- -- ----------- -- ----------- Console

, , , data : ,

-375KH20 , toHRS fromHRS

, Converter ,

Cold-Side HX I Controller A./VV'

I Alternator Startup & Control I Engine-

rectlfiC8ti°1 Voltage ~ Alternator 400V Regulation Disconnect 120V DC

AC to DC Bus

I I I

Parasitic Load Hot-Side HX

-a5OKNaK to Ht Source ~vacuum Facility from HI Source

----- --' -



• Full-scale 12 kW PCU Designs

Courtesy of Sunpower Courtesy of Barber Nichols


• National Aeronautics and Space Administration

Summary • • Long History of Closed Brayton Technology Development within

NASA & DOE - Brayton Rotating Units

- Solar Dynamic Brayton

- SP-100 Brayton

- Dynamic Isotope Power System

- Jupiter Icy Moons Orbiter

- Fission Surface Power

• Primary Benefits of Brayton include: - High Efficiency

- Scalable to High Power

- Potential for Long Life and High Reliability

- Readily Adaptable to Solar and Nuclear Heat Sources

- Simple and Efficient Electrical Integration


Oral Presentation/Viewgraphs Summary - NASAconsidering a 100 kWclass CBC system coupled to a gas-cooled fission reactor. Currently, CBC technology is being explored for Fission Surface

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