Skip to main content

Full text of "NASA Technical Reports Server (NTRS) 19930017021: Nuclear electric propulsion for planetary science missions: NASA technology program planning"

See other formats


NASA Technical Memorandum 106139 


/tf.pLO 

/ b 3o^y 

pr / 


Nuclear Electric Propulsion for Planetary Science 
Missions: NASA Technology 
Program Planning 


Michael P. Doherty 
Lewis Research Center 
Cleveland, Ohio 


Prepared for the 1. 

Tenth Symposium on Space Nuclear Power and Propulsion 
sponsored by The University of New Mexico and The American Institute 
of Physics 

Albuquerque, New Mexico, January 10—14, 1993 




( NASA— TM- 10613 9 ) NUCLEAR ELECTRIC 
PROPULSION FOR PLANETARY SCIENCE 
MISSIONS: NASA TECHNOLOGY PROGRAM 
PLANNING (NASA) 8 p 


N93-26210 


Unci as 


G3/20 0163059 




NUCLEAR ELECTRIC PROPULSION 
FOR PLANETARY SCIENCE MISSIONS: 
NASA TECHNOLOGY PROGRAM PLANNING 


Michael P. Doherty 
NASA Lewis Research Center 
21000 Brookpark Rd. 
Cleveland, OH 44135 
(216) 977-7092 


Abstract 

This paper presents the status of technology program planning to develop those Nuclear Electric Propulsion 
technologies needed to meet the advanced propulsion system requirements for planetary science missions in the next 
century. The technology program planning is based upon technologies with significant development heritage: ion 
electric propulsion and the SP-100 space nuclear power technologies. Detailed plans are presented herein for the 
required ion electric propulsion technology development and demonstration. Closer coordination between space 
nuclear power and space electric propulsion technology programs is a necessity as technology plans are being further 
refined in light of NEP concept definition and possible early NEP flight activities. 


The Solar System Exploration Division of the NASA’s Office of Space Science and Applications (OSSA) foresees 
a need for low thrust Nuclear Electric Propulsion (NEP) to provide a large reduction in propellant mass, to allow for 
laimrh date flexibility, and to reduce trip times for science missions to many planetary, asteroidal, and cometary 


Space Exploration Initiative 
and Space Science 



NEP: Level 5 to 2000 Hardware S y stems Development and Testing 


Mar s Missions - 2007 
Outer Planets >2005 


FIGURE'! . Logic Flow for Nuclear Propulsion. 



1 








targets. Mission and system studies, assuming the use of SP-100 (reactor and power conversion) technology and ion 
electric propulsion, have been performed which show that NEP enables a number of the proposed missions, allows 
for oibiter missions to the major satellites of Jupiter, Uranus, Neptune, and Pluto (versus flybys), and yields more 
frequent launch opportunities (Yen and Sauer 1991). The requirements for a long life, low mass nuclear power 
source and efficient, long life ion electric engines provide the driver for related power and propulsion technology 
programs. 

TECHNOLOGY PROGRA M PLANS 

A logic flow path for Nuclear Propulsion and its development has been established (Bennett and Miller 1992). 
Figure 1 figuratively conveys this logic flow path, showing that a Nuclear Propulsion Program is responsive to 
advanced propulsion requirements for space exploration and space science and enables flight hardware systems 
development. The purpose of the Nuclear Propulsion Program is to develop and demonstrate focused nuclear 
propulsion systems technology including compliance with sound safety and environmental policies that meet space 
exploration and space science mission requirements. 

Baseline Focused Technology Efforts 

A preliminary overall schedule for the development of 100-kilowatt (kWe) NEP for outer planetary science 
missions is shown in Figure 2. The required development steps are Focused Technology, System Definition, 
Advanced Development, and Flight System Development This schedule shows that the authority to proceed widi 
flight system development would occur approximately at the time that component level testing is complete - mid 
program year (PY) 1997 - and that the flight system critical design review would occur shortly after power/ 
propulsion technology is ready in PY2000. Work is already in progress as of PY1992 in both power and propulsion 
focused technology areas. In the propulsion technology area, initial plans have been established by NASA Lewis 
Research Center’s (LeRC’s) Nuclear Propulsion Office (NPO) for the development and demonstration of an electric 
propulsion thrust system. This activity is the chief technology focus of the Nuclear Electric Propulsion Project, 
serving to bring thrust system and component technologies to Technology Readiness Level 5 (TRL-5) and to verify 



FIGURE 2. Schedule for the Development of NEP for 

Outer Planetary Science Missions (Preliminary). 


2 




analytical tools (including performance and life models) by PY2000 for outer planetary robotic missions. In tandem 
with this activity it will be necessary to continue development and demonstration of space nuclear power system 
technologies having promise to nominally provide 100 kilowatts of power at a specific power of 25 watts per 
kilogram. The S P-1 00 program has technical plans to develop and demonstrate space rated nuclear power 
technologies to meet these requirements by approximately the year 2000 (Annijo 1992). Milestones associated with 
the SP-100 technology tentatively include: (1) space nuclear reactor technology to support an early flight of NEP at 
a sub 50-kWe power rating, to demonstrate nuclear power system launchability and integrated operations with an 
electric propulsion subsystem, and (2) follow-on component and subsystem level ground tests to demonstrate power 
system technologies not tested in the early flight, but still necessary for 100-kWe, 25 -watt 3 -per-kilogram space 
nuclear power applications. 

This paper will discuss the elements of the Nuclear Electric Propulsion Project, including NEP system definition 
and electric propulsion thrust system technology planning. The space nuclear power system technology is to be 
provided by the SP-100 Project 

Nuclear Electric Propulsion, Eroiegj 

The Nuclear Electric Propulsion Project includes six elements: project management, concept development/ 
systems engineering, NEP technology, megawatt (MW)/ innovative technology, facilities, and safety/ reliability/ 
quality assurance/ environment. A basic description of the scope of each of these project elements has been 
previously stated (Doherty 1991). 

With the establishment in PY1992 of the outer planetary science propulsion application as the primary emphasis 
of the NEP Project, project elements and activities reflect a change in focus compared to the project originally 
described by Doherty (1991). The concept development/ systems engineering element will serve to document OSSA 
customer system requirements for NEP, define NEP systems, which meet OSSA customer requirements, and design, 
fabricate, and test the required 100 kWe electric propulsion thrust system. The NEP technology element will serve 
to design, verify, and validate the performance and life of component technologies for electric thrusters, power 
processors, and their required thermal subsystems. The MW/ innovative technology element will now serve to 
identify technologies having benefit for higher power Moon and Mars NEP applications and to perform fundamental 
MW technology demonstration tests. The facilities element will serve to identify and advocate the facility 
infrastructure that is necessary for testing of kilowatt-rated non-nuclear technologies for NEP. The safety/ reliability/ 
quality assurance/ environment element will serve to perform studies and assessments to establish requirements upon 
the safe, environmentally acceptable design, development, test, deployment, and operations of space nuclear electric 
propulsion. 

The schedule for the Nuclear Electric Propulsion Project (Figure 3) shows extensive interaction between the project 
elements just described. 

Concept Development/ Systems Engineering 

The Concept Development/ Systems Engineering element will define, design, and develop the system concept 
which meets the propulsion requirements of the mission. This element is characterized by three chief activities. The 
first activity is the development and documentation of NEP system requirements. NEP system requirements to meet 
the propulsion requirements for the OSSA outer planetary science missions have already been documented (NPO 
1992). This document, conforming to MIL-STD-490A, describes the NEP system, states specific performance 
requirements, defines the approach to verification, and includes reference mission descriptions. It is meant to be a 
“living document”, a document whose continual updating is encouraged and controlled by a formal change control 
process. 

The second activity is the definition of a system concept to meet the propulsion requirements for the outer 
planetary missions. First, an assessment will be made of the applicability of a common NEP flight system in 
meeting the propulsion requirements of a number of the outer planetary missions, and a baseline system configured. 
Then, a more detailed system concept definition will be performed, which shall include consideration of thrust axis 


3 




orientation, nuclear electric power subsystem configuration, thruster nominal power level and array definition, thrust 
vectoring strategy, vehicle guidance, navigation, and control, reaction control system, telecommunications, and 
tannrh packaging and deployment. The output from this detailed definition will be the documentation of technology 
requirements for the space nuclear electric power system and detailed technology requirements for thruster and power 
processor (and associated thermal management subsystems), as well as detailed system and subsystem drawings/ 
schematics. Significantly detailed system and subsystem performance computer models will support the definition 
of the concept. It is expected that the initial concept definition activity (PY1993) will provide a set of major 
technology requirements, while the detailed system concept definition will update these technology requirements 
(PY1994). 

The final major activity under this element is the design, hardware fabrication, and testing for the electric 
propulsion thrust system. Once the overall system concept is defined (PY1994) and thruster and power processor 
technology performance limits and life estimates are established (mid PY1995), a detailed design of the electric 
propulsion thrust system will be performed on contract. This will enable fabrication and delivery by industry to the 
government of engineering model thruster, power processor, and propellant feed system hardware (early PY1997). 
Subsequent to component integration and critical interface verification, a series of plume and fields compatibility, 
simulated qualification, and cluster tests, as well as subsystem performance (PY1998) and life verification tests 
(PY2000), will be performed in government space environment simulation facilities. TRL-5 (PY2000) of the 
electric propulsion thrust system will be supported with documentation in the form of drawing packages, assembly 
procedures, assembly records, and reports. 

NEP Technology 

The NEP Technology element will experimentally evaluate thrust subsystem components and related technologies 
to enable industry to develop an engineering model thrust subsystem. Technology requirements for thruster, power 
processor, and their related thermal management subsystems will provide focus for the required technology efforts. 
For thrusters, experimental evaluation of performance and life issues will require 25-50 kW class laboratory model 


4 





thruster development and testing, hollow cathode, ion optics, and isolator/ neutralizer component development and 
demonstration, and thruster wear/ life testing. The laboratory class hardware will be used to verify critical interfaces 
and assess plume/ fields compatibility issues also. Models for performance and life will be developed, and then 
verified with the lab-class hardware. Technology performance and life limits will be established (mid PY1995), 
enabling the development of engineering model thrust subsystem hardware, and thruster lifetime will be demonstrated 
and verified (PY1997). Recent progress in non-nuclear NEP technologies has been documented by Stone and Sovey 
(1992). 

MW/ Innovative Technology 

The MW/ Innovative Technology element will serve to identify and provide requirements for technologies highly 
beneficial to megawatt NEP applications for the Space Exploration Initiative, and to conduct fundamental 
component/ subsystem performance tests. 

Facilities 

Long term life testing of laboratory class ion electric thrusters as well as thruster-cluster system demonstrations 
place a demanding set of requirements on space environment simulation facilities. The capabilities of many large 
U.S. vacuum chambers have been reviewed and compared with the requirements for electric propulsion testing by 
Sovey et al (1991). The Electric Propulsion Laboratory’s Tank 5 (NASA Lewis Research Center) is a potential 
facility for testing the electric propulsion technologies required for 100-kWe NEP, but some facility modifications 
will be required by PY1995 to enable laboratory model life testing and eventual engineering model thrust system 
testing. The Facilities element will provide requirements to help ensure that the necessary facilities are available for 
electric propulsion component, subsystem, and full system ground testing. 

Safety/ Reliability/ Quality Assurance/ Environment 

System safety, reliability, quality assurance, and environmental impact assessments will have continual impact on 
concept definition, component technology evaluation, and thrust system design and design verification activities. 

IMPLICATIONS OF AN EARLY FLIGHT OF NEP 

As a consequence of the signing of a Memorandum of Understanding Between NASA and the Department of Energy 
(DOE) regarding energy-related civil space activities (July 9, 1992), a working group was established to consider 
program options for a small, lightweight, compact nuclear reactor sized to meet NASA proposed space, and lunar, 
and planetary surface programs (Greene 1992). The working group’s highest consideration for such a compact 
nuclear reactor is a liquid metal cooled, fuel pin, fast spectrum reactor with a Brayton power conversion system rated 
nominally at 20-kWe, and mated with an electric propulsion subsystem into an NEP flight system for several 
planetary science missions (Greene and Newhouse 1992). The mission application of such an early flight option for 
NEP has been reviewed with the Solar System Exploration Division, and fundamental agreement obtained that this 
early NEP flight option should be characterized by a lower system electrical power, a shorter system lifetime, and an 
earlier deployment date than any of the missions previously analyzed by Yen and Sauer (Y en and Sauer 1991). 

Because preliminary interest has been generated concerning an NEP system employing liquid metal cooled reactor 
technology and ion electric propulsion having potentially less than a 50-kWe rating, less than 3 year lifetime, and a 
a deployment date as early as a 1998, it is incumbent that both technology (as well as system) development and 
demonstration issues between this application and the 100-kWe application be worked in a concurrent manner. The 
near term deployment date for the lower power application requires technologies that are already mature, implying 
that some separate technology maturation process will still be required to enable 100-kWe missions. Nevertheless, 
the early flight option will be extremely useful to verify NEP systems technology, to demonstrate the safety 
approval process, and to validate as many as possible of the technologies relevant to the more robust outer planetary 
science mission applications, and therefore provides a path for the development of higher power, future operational 
NEP capabilities. 


5 



SUMMARY AND CONCLUSIONS 


Building upon the technology heritage available through the SP-100 power and ion electric propulsion programs, 
die NEP technology project will coordinate, develop, and demonstrate by year 2000 the technologies required for 100 
kilowatt-electric (kWe) NEP. Detailed plans, including project content, schedule, and milestones, have been 
presented for the required ion electric propulsion technology development and demonstration; meanwhile, the SP-100 
program is implementing technical plans to develop and demonstrate the required space rated nuclear power 
technologies. It is clear that closer coordination between organizations responsible for the required space nuclear 
power and space electric propulsion technologies is necessary for effective, efficient development and utilization of 
these technologies. NEP system concept definition activities and a possible early flight option for NEP can provide 
the required focus. 


Acknowledgments 


The author wishes to acknowledge Messrs. John Clark, Jim Stone, and Jim Gilland of the LeRC s NPO, Jim 

Sovey of LeRC’s Space Propulsion Technology Division, and John Brophy and Jack Mondt of the Jet Propulsion 

Laboratory in their contribution to the programmatic exercises which led to the development of this baseline plan. 

This work was performed “in-house” by personnel at LeRC and JPL. 

References 

Armijo, J. S. (1992) “SP-100 Overview / Technical Progress,” briefing package #CDRL M027, SP-100 Annual 
Technical Meeting, Arlington, VA, 16-17 June 1992. 

Bennett, G. L. and T. J. Miller (1992) “NASA Program Planning on Nuclear Electric Propulsion,” AIAA-92-1557, 
presented at AIAA Space Programs and Technologies Conference, Huntsville, AL, 24-27 March 1992. 

Doherty, M. P. (1991) “Blazing the Trailway: Nuclear Electric Propulsion and its Technology Program Hans,” 
AIAA-91-3441, presented at NASA/ AIAA/ OAI Conference on Advanced Space Exploration Initiative 
Technologies, Cleveland, OH, 4-6 September 1991. 

Greene, J. H. (1992) memorandum regarding “Space Nuclear Power and Propulsion Working Group,” NASA 
Johnson Space Center, Houston, TX, 8 August 1992. 

Greene, J. H. and A. R. Newhouse (1992) “Space Nuclear Power and Propulsion: Final Report,” National 
Aeronautics and Space Administration and Department of Energy joint document, Washington, D.C., 15 
September 1992. 

MIL (1985) “Specification Practices,” MIL-STD-490A, 4 June 1985. 

NPO (1992) Nuclear Electric Propulsion System Requirements, draft document, revision 003, NASA Lewis 
Research Center, Cleveland, OH, 14 August 1992. 

Sovey, J. S„ R. H. Vetrone, S. P. Grisnik, R. M. Myers, and J. E. Parkes (1991) “Test Facilities for High Power 
Electric Propulsion,” AIAA-91-3499, presented at NASA/ AIAA/ OAI Conference on Advanced Space Exploration 
Initiative Technologies, Cleveland, OH, 4-6 September 1991. 

Stone, J. R. and J. S. Sovey (1992) “NASA’s Nuclear Electric Propulsion Technology Project,” NASA TM 
105811, prepared for the 28th Joint Propulsion Conference, Nashville, TN, 6-8 July 1992. 

Yen, C. L. and C. G. Sauer (1991) “Nuclear Electric Propulsion for Future NASA Space Science Missions,” IEPC- 
91-035, presented at AIDAA/AIAA/DGLR/JSASS 22nd International Electric Propulsion Conference, Viareggio, 
Italy, 14-17 October 1991. 


6 



REPORT DOCUMENTATION PAGE 

Form Approved 
OMB No. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 
gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other ssprxt of this 
collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports. 121 5 Jefferson 
Davis Highway, Suite 1204. Arlington, VA 22202-4302, and to the Office of Management and Budget. Paperwork Reduction Project (0704-0188), Washington, DC 20503. 

1. AGENCY USE ONLY (Leave blank ) 

2. REPORT DATE 

May 1993 

3. REPORT TYPE AND DATES COVERED 

Technical Memorandum 

4. TITLE AND SUBTITLE 



5. FUNDING NUMBERS 

Nuclear Electric Propulsion for Planetary Science Missions: NASA Technology 
Program Planning 

WIT 

6. AUTHOR(S) 



W U "J7J — / A. 

Michael P. Doherty 




7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION 
REPORT NUMBER 

E-7820 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 


10. SPONSORING/MONFTORING 
AGENCY REPORT NUMBER 

National Aeronautics and Space Administration 
Washington, D.C. 20546-0001 


NASA TM- 106139 

11. SUPPLEMENTARY NOTES 

Prepared for the Tenth Symposium on Space Nuclear Power and Propulsion sponsored by The University of New 
Mexico and The American Institute of Physics, Albuquerque, New Mexico, January 10-14, 1993. Responsible person, 
Michael P. Doherty, (216) 433-7092. 

12a. DISTRKBUTION/AVAILABIUTY STATEMENT 


12b. DISTRIBUTION CODE 

Unclassified - Unlimited 
Subject Category (awaiting) 




13. ABSTRACT (Maximum 200 words) 


This paper presents the status of technology program planning to develop those Nuclear Electric Propulsion 
technologies needed to meet the advanced propulsion system requirements for planetary science missions in the 
next century. The technology program planning is based upon technologies with significant development 
heritage: ion electric propulsion and the SP-100 space nuclear power technologies. Detailed plans are presented 
herein for the required ion electric propulsion technology development and demonstration. Closer coordination 
between space nuclear power and space electric propulsion technology programs is a necessity as technology 
plans are being further refined in light of NEP concept definition and possible early NEP flight activities. 


14. SUBJECT TERMS 

Nuclear electric propulsion; Ion electric propulsion; Space nuclear power; SP-100; 
Technology planning 

15. NUMBER OF PAGES 

8 

16. PRICE CODE 

A02 

17. SECURITY CLASSIFICATION 
OF REPORT 

Unclassified 

18. SECURITY CLASSIFICATION 
OF THIS PAGE 

Unclassified 

19. SECURITY CLASSIFICATION 
OF ABSTRACT 

Unclassified 

20. LIMITATION OF ABSTRACT 


NSN 7540-01-280-5500 Standard Form 298 (Rev. 2 - 89 ) 


Prescribed by ANSI Std. Z39-18 
298-102