SP_100_REACTOR.pdf
SP-100 Reactor with Brayton Conversion for Lunar Surface Applications
A study examining the potential for integrating Brayton-cycle power conversion with the SP-100 reactor for lunar surface power applications. Two
designs are modeled.
Document date: 1992-01-12
Department: Lewis Research Center
Author: Lee S. Mason, Carlos D. Rodriguez, Barbara I. McKissock, James C. Hanlon, Brian C. Mansfield
Document type: report
pages: 20
Archivist's Notes: Fair quality text document.
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Sponsoring/Monitoring Agency: National Aeronautics and Space Administration Washington D.C.
Author: Lee S. Mason, Carlos D. Rodriguez, Barbara I. McKissock, James C. Hanlon, Brian C. Mansfield
Summary:
This study examines the potential for integrating Brayton-cycle power conversion with the SP-100 reactor for lunar surface power system applications.
Two designs were characterized and modeled.
The first design integrates a 100-kWe SP-100 Brayton power system with a lunar lander. This system is intended to meet early lunar mission power needs
while minimizing on-site installation requirements. Man-rated radiation protection is provided by an integral multilayer, cylindrical ithium
hydride/tungsten (LiH/W) shield encircling the reactor vessel.
Design emphasis is on ease of deployment, safety, and reliability while utilizing relatively near-term technology. The second design combines Brayton
conversion with the SP-100 reactor in an erectable 550-kWe power plant concept intended to satisfy later-phase lunar base power requirements. This
system capitalizes on experience gained from operating the initial 100-kWe module and incorporates some technology improvements. For this system the
reactor is emplaced in a lunar regolith excavation to provide man-rated shielding, and the Brayton engines and radiators are mounted on the lunar
surface and extend radially from the central reactor. Design emphasis is on performance, safety, long life, and operational flexibility.
Design emphasis is on performance, safety, long life, and operational flexibility.
INTRODUCTION:
Recent studies examining approaches for lunar base missions have suggested a need for
nuclear reactor power systems (Synthesis Group Report, 1991). Most mission development strategies suggest a phased approach for meeting mission
objectives. Power requirements for permanent-occupancy lunar surface missions range from tens of kilowatts for the early emplacement phases to
hundreds of kilowatts for the later operational phases. Nuclear reactor power systems provide a low-mass, long-life option for meeting these
requirements. One strategy for satisfying lunar base power requirements is through a centralized utility. Power could be generated by multiple systems
and provided to a central user-common switching station. From the switching station electric power would be distributed to the various users.
The stated power requirements are commensurate with results from NASA's 90-day study of the Moon and Mars. Within the power generation area an
initial nuclear reactor system could be emplaced that would have the capacity to meet near-term power requirements associated with the emplacement
phase.
Principal power users for this phase of the mission might include initial crew habitat modules, science platforms, rover recharging facilities, and
in-situ resource utilization (ISRU) demonstrations.
A photovoltaic and regenerative fuel cell (PV/RFC) system might also be utilized to provide redundant power to the habitat life support systems.
If the lunar base grows and power requirements increase to accommodate laboratory modules, constructible habitats, liquid oxygen plants, launch and
landing servicing facilities, and expanded science, a subsequent larger nuclear reactor system could be delivered to complement and eventually replace
the original system.
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Here are the Highlights:
GROUND RULES AND DESIGN GUIDELINES
This study characterizes two different SP-100 Brayton systems.
The first system is sizedfor 100 kWe and is designed to be self deployable. It was assumed that this system would be one of the first elements
delivered to the lunar surface and therefore could rely on no equipment or manpower for its installation.
The second system is sized for 551} kWe. This system is assumed to be delivered to the Moon when power requirements have increased to account for a
full operational liquid oxygen production facility.
Because this system would be delivered once the base is established, it was assumed that a crew would be available for its installation. The basic
concept consists of a single SP-100 reactor located in a cylindrical hole with surface-mounted Brayton engines and radiators. Man-rated radiation
protection is provided through the emplacement of the reactor in the excavation. Despite the crew availability this power plant is designed for quick
and easy assembly.
Reactor and Primary Heat-Transport System
In both cases SP-100 reactor technology is assumed. SP-100 is a joint Department of
Energy (DOE), NASA, Department of Defense (DOD) program to develop a space reactor power system. The reactor subsystem consists of uranium nitride
(UN) fuel pins, reflector controls, safety rods, pressure vessel, auxiliary coolant loop, and instrumentation and controls.
Man-Rated Shielding
The 100-kWe system utilizes an integral man-rated shield to protect the lunar base crew members. The shield circumferentially surrounds the reactor
core and consists of alternating layers of tungsten and lithium hydride.
Heat Rejection
The heat rejection system for the 100-kWe system is designed to fit within the lander
system and be self-deployable. Previous designs for systems of this nature have shown a conical, deployable radiator that extends above the lander and
is located within the instrument shield half-angle to eliminate back scattering (Hickman and Bloomfield, 1989).
Power Conditioning, Control, and Distribution
For both systems an ac-ac converter is included to convert the alternator output to a suitable voltage for long-distance transmission.
Studies have shown that high-voltage transmission is a favorable method for reducing the mass of the cabling for lunar base missions with multiple,
distributed users.
Longdistance cabling might also be desirable when nuclear systems are utilized so as to provide safe separation distances between crew and powerplant.
The ac-ac converter consists of transformers, ancillary control, and circuit protection in a thermally conductive enclosure with heat-pipe radiator
cooling.
100-kWe SYSTEM DESIGN
The 100-kWe design has the reactor, the power conversion units, and the heat exchangers enclosed in a cylindrical protective shell that is supported
by the lander structure. The deployed system is presented in figure 5. A cross section of the internal components of that shell is shown in figure 6
with the cylindrical man-rated shield cut away to display the reactor core.
The range of temperatures for heat rejection required that a combination of mercury and water heat pipes be used for both designs.
550-kWe SYSTEM DESIGN
The system specific mass represents a significant improvement over the two 100-kWe systems. This can be attributed to component economies of scale
resulting from the higher power output and the utilization of in-situ materials to provide man-rated shielding.
CONCLUSIONS
Both of the designs presented in this paper offer distinct advantages for lunar surface power generation.
The 100-kWe system is a safe, reliable design that requires minimal manpower for installation and uses relatively near-term technology.
It is ideal for initial lunar base power requirements.
The 550-kWe system is applicable when power requirements have increased to accommodate extensive in-situ resource utilization.
Its design is consistent with the needs of an evolved lunar base: performance, safety, long life, and operational flexibility.
The potential advantages of the centralized power utility approach suggested in this report include redundancy, user growth accommodation, reduced
development cost, and simplified logistics. For nuclear reactor systems an additional advantage of a central utility is that all of the power systems
can be collocated in a single remote area for safety.
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reply to post by AboveTopSecret.com
this is very interesting...but i believe that they have these produced as a " what if" so when they do go to the moon or mars, they have some
expert who has done research into the feasibility of actual application of this particular endeavor. the "if and when" this technology is applied is
the intriguing question. thanks for all the time and effort put into the release and posting of these documents. this is grunt work that has to be
done
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