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Design and Analysis of RTGs for CRAF and Cassini Missions

Description: This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications. The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. But subsequently JPL significantly increased both the power level and the mission duration for both missions, so that they can no longer by met by two standard RTGs. The resultant power gap must be closed either by reducing JPL's power demand (e.g., by decreasing contingency reserves) and/or by increasing the power system's output. One way under active consideration which more than meets the system power goal would be the addition of a third RTG for each mission. However, the author concluded that it may be possible to meet or closely approach the CRAF power demand goals with just two RTGs by relatively modest modification of their design and/or operating conditions. To explore that possibility, the effect of various modifications - either singly or in combination - was analyzed by Fairchild. The results indicate that modest modifications can meet or come very close to meeting the CRAF power goals with just two RTGs. Elimination of the third RTG would yield substantial cost and schedule savings. There are three copies in the file.
Date: November 30, 1990
Creator: Schock, Alfred; Noravian, Heros & Sankarankandath
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for CRAF and Cassini Missions; two copies - one dated 8/3/1990 and the other dated 11/8/1990.

Description: The paper describes the design and analysis of Radioisotope Thermoelectric Generators Integrated with JPL's CRAF and Cassini spacecraft. The principal purpose of the CRAF mission is the study of asteroids and comets, and the principal purpose of the Cassini mission is the study of asteroids, Saturn, and its moons (particularly Titan). Both missions will employ the Mariner/Mark-2 spacecraft, and each will be powered by two GPHS-RTGs. JPL's spacecraft designers wish to locate the two RTGs in close proximity to each other, resulting in mutual and unsymmetrical obstruction of their heat rejection paths. To support JPL's design studies, the U.S. Department of Energy asked Fairchild to determine the effect of the RTGs' proximity on their power output. As described in the paper, this required the development of novel analysis methods and computer codes for the coupled thermal and electrical analysis of obstructed RTGs with axial and circumferential temperature, voltage, and current variations. The code was validated against measured data of unobstructed RTG tests, and was used for the detailed analysis of the obstructed CRAF and Cassini RTGs. Also described is a new method for predicting the combined effect of fuel decay and thermoelectric degradation on the output of obstructed RTGs, which accounts for the effect of diminishing temperatures on degradation rates. For the 24-degree separation angle of JPL's original baseline design, and for the 35-degree RTG separation of JPL's revised design, the computed results indicate that the mutually obstructed GPHS/RTGs with standard fuel loading and operating temperatures can comfortably meet the JPL-specified power requirements for the CRAF mission and almost meet the specified requirements for the Cassini mission.
Date: October 8, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for Solar and Martian Exploration Missions

Description: The paper described the results of design, analysis and spacecraft integration studies of Radioisotope Thermoelectric Generators (RTGs) for three unmanned space exploration missions. The three missions, consisting of the Mars Rover and Sample Return (MRSR) mission, the Solar Probe mission, and the Mars Global Net work (MGN) mission, are under study by the Jet Propulsion Laboratory (JPL) for the U.S. National Aeronautics and Space Administration (NASA). The NASA/JPL mission studies are supported by the U.S. Department of Energy's Office of Special Applications (DOE/OSA), which has commissioned Fairchild Space Company to carry out the required RTG design studies.
Date: May 1, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design and Spacecraft-Integration of RTGs for Solar Probe

Description: Presented at the 41st Congress of the IAF, October 6-12, 1990 in Dresden, FRG. The paper describes the design and analysis of Radioisotope Thermoelectric Generators integrated with JPL's planned Solar Probe spacecraft. The principle purpose of the Solar probe mission is to explore the solar corona by performing in-situ measurements at distances as close as four solar radii or 0.02 AU from the sun. This proximity to the sun imposes some unusual design constraints on the RTG and on its integration with the spacecraft. The results demonstrated that the obstructions result in significant performance penalties for the case of the standard GPHS-RTG design. Finally, the paper describes a simple empirical method for predicting the combined effect of fuel decay and thermoelectric degradation on the RTG's power output, and applies that method to predict the long-term power profile of the obstructed Solar Probe RTGs. The results indicate that the existing GPHS-RTG design, even without modifications can meet the JPL-prescribed EOM power requirement. There is also three copies in the file of an earlier version of this dated 8/3/1990 with the report number of FSC-ESD-217-90-470. The most current one is the IAF version (IAD-90-208) dated October 6-12, 1990.
Date: October 1, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Coupled Thermal and Electrical Analysis of Obstructed RTGs

Description: A Radioisotope Thermoelectric Generator (RTG) with an unsymmetrically obstructed heat rejection path can have significant axial and circumferential variations in the temperatures, currents, and voltages of its thermoelectric couple network. The present paper describes a methodology for analyzing the thermal and electrical performance of such an RTG, and the development of a computer code for implementing that emthodology. The code derives coupled solutions of the RTG's thermal, thermoelectric, and electrical equations. It accounts for the Peltier effect, Ohmic heating, and the Thomson effect, and treats the electrical power produced in each couple as an effective heat sink. It satisfies the condition that all parallel couples produce the same voltage, and that all series-connected couple groups produce the same current. Finally, the paper illustrates the use of the code by applying it to the detailed analysis of the RTGs for the CRAF and Cassini missions. In each of these, there are two adjacent RTGs which are obstructed by each other and by the nearby spacecraft. The results of the analysis will be used by the spacecraft designers in selecting the location, orientation, and spacing of the two RTGs. There are two copies in the file.
Date: January 1, 1990
Creator: Schock, Alfred; Noravian, Heros & Or, Chuen T.
Partner: UNT Libraries Government Documents Department

Space Exploration and the Benefits to Mankind

Description: Paper presented at the 41st Congress of the International Astronautical Federation in Dresden, GDR in October 1990. This paper analyzes the past challenges of the space program's multi-national cooperative agreements and examines the challenges of the future as we quickly become a global society. Cross Reference ESD-T1.
Date: October 1, 1990
Creator: Moser, T.L.; Freitag, R. & Schneider, W.C.
Partner: UNT Libraries Government Documents Department

On the Response of the Ulysses RTG to the Impact of Large SRM-Fragments

Description: Presented at the Seventh Symposium on Space Nuclear Power Systems in Albuquerque, NM, January 7-11, 1990. It will be shown that end-on impacts, which are more likely to occur with Ulysses than with Galileo, will produce greater average fueled clad distortion than was typical of Galileo. Fortunately, the predicted distortions remain well within the Galileo database. It will also be shown that the 2-dimensional calculations which were performed for the Galileo configuration were indeed valid in that application and are also valid for the Ulysses configuration. There are three copies in the file.
Date: January 1, 1990
Creator: Eck, Marshall B. & Mukunda, Meera
Partner: UNT Libraries Government Documents Department

Users manual for Aerospace Nuclear Safety Program six-degree-of-freedom reentry simulation (TMAGRA6C)

Description: This report documents the updated six-degree-of-freedom reentry simulation TMAGRA6C used in the Aerospace Nuclear Safety Program, ANSP. The simulation provides for the inclusion of the effects of ablation on the aerodynamic stability and drag of reentry bodies, specifically the General Purpose Heat Source, GPHS. The existing six-degree-of-freedom reentry body simulations (TMAGRA6A and TMAGRA6B) used in the JHU/APL Nuclear Safety Program do not include aerodynamic effects resulting from geometric changes to the configuration due to ablation from reentry flights. A wind tunnel test was conducted in 1989 to obtain the effects of ablation on the hypersonic aerodynamics of the GPHS module. The analyzed data were used to form data sets which are included herein in tabular form. These are used as incremental aerodynamic inputs in the new TMAGRA6C six-degree-of-freedom reentry simulation. 20 refs., 13 figs., 2 tabs.
Date: February 1, 1990
Creator: Sharbaugh, R.C.
Partner: UNT Libraries Government Documents Department

GPHS motion studies for heat pulse intervals of reentries from gravity-assist trajectories. [General Purpose Heat Source Module (GPHS)]

Description: Motion studies of the General Purpose Heat Source Module, GPHS, were conducted in the heat pulse interval associated with entries from earth gravity assist trajectories. The APL six-degree-of-freedom reentry program designated TMAGRA6C was used. The objectives of the studies were to (1) determine the effect of ablation on GPHS motion, and (2) determine whether the GPHS module entering the earth's atmosphere from an earth-gravity-assist trajectory has a preferred orientation during the heat pulse phase of reentry. The results are given in summary form for easy visualization of the initial conditions investigated and to provide a quick-look of the resulting motion. Detail of the motion is also given for the parameters of interest for each case studied. Selected values of initial pitch rate, roll rate, and combinations of these within the range 0[degree] to 1000[degrees]/sec were investigated for initial reentry angles of -7[degrees] (shallow) and -90[degrees] (steep) and initial angles of attack of 0[degree] (broadface to the wind) and 90[degrees]. Although the studies are not exhaustive, a sufficient number of reentry conditions (initial altitude, reentry angle, angle of attack, rotational motion) have been investigated to deduce certain trends. The results also provide information on additional reentry conditions that need to be investigated. The present results show four GPHS orientations that predominate - all with some pitch oscillations and rolling motion. These are: angles of attack, [alpha][sub R] of 0[degree], 30[degrees], 90[degrees] and tumbling. It should be assumed that all these orientations are equally probable because only combinations of two initial reentry angles, [gamma][sub 0], and two values of [alpha][sub R]. have been investigated. Further the probability for any given initial rate on orientation is not known.
Date: March 1, 1990
Creator: Lucero, E.F. & Sharbaugh, R.C.
Partner: UNT Libraries Government Documents Department

Low-mass, intrinsically-hard high temperature radiator. Final report, Phase I

Description: This paper reports on the investigation of layered ceramic/metal composites in the design of low-mass hardened radiators for space heat rejection systems. The investigation is part of the Strategic Defence Initiative. This effort evaluated the use of layered composites as a material to form thin-walled, vacuum leaktight heat pipes. The heat pipes would be incorporated into a large heat pipe radiator for waste heat rejection from a space nuclear power source. Composite materials evaluations were performed on combinations of refractory metals and ceramic powders. Fabrication experiments were performed to demonstrate weldability. Two titanium/titanium diboride composite tubes were successfully fabricated into potassium heat pipes and operated at temperatures in excess of 700C. Testing and analysis for composite tubes are described in the report. The study has verified the feasibility of using layered composites for forming thin-walled, light weight heat pipe tubes for use in hardened space radiators.
Date: July 15, 1990
Partner: UNT Libraries Government Documents Department

NASA low power DIPS [Dynamic Isotope Power System] conceptual design requirements document

Description: This document describes the requirements for a low power (0.5--1.0 kwe) Dynamic Isotope Power System (DIPS) for interplanetary and space exploration missions using the Mariner Mark II spacecraft. The reference mission used to establish these requirements was the Cassini orbiter mission to Saturn. Requirements specific to two other missions (Outer Planet Orbiter/Probe and Comet Nucleus Sample Return) are also included. A list of references used to develop these requirements is provided. 17 refs., 2 figs., 2 tabs.
Date: January 1, 1990
Creator: Johnson, G.; Determan, W. & Otting, W.
Partner: UNT Libraries Government Documents Department

Thulium-170 heat source

Description: An isotopic heat source is formed using stacks of thin individual layers of a refractory isotopic fuel, preferably thulium oxide, alternating with layers of a low atomic weight diluent, preferably graphite. The graphite serves several functions: to act as a moderator during neutron irradiation, to minimize bremsstrahlung radiation, and to facilitate heat transfer. The fuel stacks are inserted into a heat block, which is encased in a sealed, insulated and shielded structural container. Heat pipes are inserted in the heat block and contain a working fluid. The heat pipe working fluid transfers heat from the heat block to a heat exchanger for power conversion. Single phase gas pressure controls the flow of the working fluid for maximum heat exchange and to provide passive cooling.
Date: September 6, 1990
Creator: Walter, C.E.; Van Konynenburg, R. & VanSant, J.H.
Partner: UNT Libraries Government Documents Department

Creep strength of niobium alloys, Nb-1%Zr and PWC-11

Description: A study is being conducted at NASA Lewis Research Center to determine the feasibility of using a carbide particle strengthened Nb-1% Zr base alloy to meet the anticipated temperature and creep resistance requirements of proposed near term space power systems. In order to provide information to aid in the determination of the suitability of the PWC-11 alloy as an alternative to Nb-1% Zr in space power systems this study investigated (1) the long-time high-vacuum creep behavior of the PWC-11 material and the Nb-1% Zr alloy, (2) the effect of prior stress-free thermal aging on this creep behavior, (3) the effect of electron beam (EB) welding on this creep behavior, and (4) the stability of creep strengthening carbide particles. 14 refs., 5 figs., 2 tabs.
Date: January 1, 1990
Creator: Titran, R.H.
Partner: UNT Libraries Government Documents Department

Electronic and photonic power applications

Description: Efficient conversion of radioactive decay to electrical power has been the goal of a number of past research efforts. One of these was the Elgin-Kidde nuclear battery. In this concept promethium-147 was used as a beta source which was then mixed with a phosphor to produce a radioluminescent (RL) source of light. The light source was coupled to silicon photovoltaic converters to create electricity. This photoelectric approach is being revisited using tritium based solid state compounds and advanced gas concepts to produce RL light sources being disclosed at this conference. Efficient conversion of the RL light energy to electrical energy imposes certain requirements on the semiconductor converter. These requirements will be discussed. Projections of power source electrical and physical characteristics will be presented based on reasonable design parameter assumptions. The words Power Supply'' usually evoke a vision of a rotating machine or chemical battery. However, today's technology is making increasing use of photonics, where information and even power can be moved through optical fibers. Brighter volumetric RL light sources open a whole new range of photonics-based applications, while solid state tritiated compounds provide the foundation for improved mechanical adaptability and safety. 4 refs., 6 figs., 1 tab.
Date: January 1, 1990
Creator: Walko, R.J.; Ashley, C.S.; Brinker, C.J.; Reed, S.T.; Renschler, C.L. (Sandia National Labs., Albuquerque, NM (USA)); Shepodd, T.J. (Sandia National Labs., Livermore, CA (USA)) et al.
Partner: UNT Libraries Government Documents Department

Galileo light-weight radioisotope heater units design and safety analysis

Description: The Light-Weight Radioisotope Heater Unit (LWRHU) provides thermal energy to temperature sensitive components aboard the orbiter/probe of the Galileo Spacecraft during its multiyear interplanetary mission. Heat is derived from the radioisotopic decay of 238-plutonium. A power of 0.56 watts/gram of radioisotope, a half-life of 88 years, and no moving parts permitted a robust, long-lived, compact heat source design. A single l-w design provided small thermal increments, with options in the number and placement, to satisfy the needed thermal environment for the spacecraft components. Radioisotope use in these devices necessitated the assessment of postulated radiological risks in accidents or malfunctions of the space shuttle or the Galileo spacecraft during near earth mission phases. Included in this document are data for the design, postulated accidents with their consequences, test data, and the derived source terms and personnel exposures for the various events. 5 refs., 1 fig., 1 tab.
Date: January 1, 1990
Creator: Johnson, E.W. (EG and G Mound Applied Technologies, Miamisburg, OH (USA)) & Zocher, R.W. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Thermal analysis of the FSP-1 fuel pin irradiation test

Description: Thermal analysis of a pin from the FSP-1 fuels irradiation test has been completed. The purpose of the analysis was to provide predictions of fuel pin temperatures, determine the flow regime within the lithium annulus of the test assembly, and provide a standardized model for a consistent basis of comparison between pins within the test assembly. The calculations have predicted that the pin is operating at slightly above the test design temperatures and that the flow regime within the lithium annulus is a laminar buoyancy driven flow. 7 refs., 5 figs.
Date: July 25, 1990
Creator: Lyon, W.F. III.
Partner: UNT Libraries Government Documents Department

Multiplexer/amplifier test results for SP-100

Description: Multiplexer and amplifier systems must be designed with transistors that can perform satisfactorily over ten years to a total gamma dose of 120E6 rads and a total neutron fluence of 1.6E15 nvt for the SP-100 reactor system. Series of gamma and neutron tests have been completed to measure transistor degradation as a function of total dose, fluence, and temperature. Test results indicate that modest increases in temperature result in substantial improvement of transistor performance at a neutron flux of 8E8 n/cm{sup 2}/s. 2 refs., 3 figs.
Date: January 1, 1990
Creator: King, D.B.; Luker, S.M. (Sandia National Labs., Albuquerque, NM (USA)) & Ryan, R. (General Electric Co., San Jose, CA (USA))
Partner: UNT Libraries Government Documents Department

Multi-service briefing on radioisotope systems for defense applications, briefing notes and supporting information

Description: A briefing on isotope systems technology and applications was held at the Pentagon on 9 May 1990, cosponsored by the Department of Defense and the Department of Energy. The objective was to provide isotope systems information to interested individuals and offices from the DOD and the Services, and then to discuss potential uses of this technology within the defense community. Presentations were given on the useful characteristics of radioactive decay, isotope sources, properties of specific isotopes, and details of isotope systems that have been deployed for terrestrial and space applications. Application areas covered included: electrical, thermal and mechanical energy conversion systems; radiation applications; and radioluminescent lights. Talks were also given on system licensing and approvals, and conclusions from the 1986 workshop on isotope systems applications. This document contains the meeting agenda, copies of the vu-graphs used in the presentations, face sheets given to meeting attendees, a list of attendees, and supplementary information requested during the meeting.
Date: May 1, 1990
Creator: Jarrett, J.H. & Tingey, G.L.
Partner: UNT Libraries Government Documents Department

Milliwatt generator heat source progress report, January--December 1989

Description: All hardware shipments to LANL were made on or ahead of schedule, thus satisfying all War Reserve and other hardware/yttrium requirements for the reporting period January--December 1989. A special investigation was conducted to determine the source of a surface staining'' problem observed on some T-111 components. Although the cause was not positively identified, the actions taken as a result of the investigation dramatically reduced both the frequency of occurrence and the magnitude of the problem. Hardware fabrication activates continued in an efficient and timely manner, with production losses at a minimal level. During the reporting period, a 99.4% utilization yield was realized, with a 0.8 dollar percent defectiveness. 1 ref., 15 figs., 5 tabs.
Date: September 10, 1990
Creator: Saylor, R.W.
Partner: UNT Libraries Government Documents Department

Unique features of space reactors

Description: Space reactors are designed to meet a unique set of requirements; they must be sufficiently compact to be launched in a rocket to their operational location, operate for many years without maintenance and servicing, operate in extreme environments, and reject heat by radiation to space. To meet these restrictions, operating temperatures are much greater than in terrestrial power plants, and the reactors tend to have a fast neutron spectrum. Currently, a new generation of space reactor power plants is being developed. The major effort is in the SP-100 program, where the power plant is being designed for seven years of full power, and no maintenance operation at a reactor outlet operating temperature of 1350 K. 8 refs., 3 figs., 1 tab.
Date: January 1, 1990
Creator: Buden, D.
Partner: UNT Libraries Government Documents Department

Iridium-alloy processing experience in FY 1989

Description: Iridium-alloy blanks and foil are produced at the Oak Ridge National Laboratory for use as fuel cladding material in radioisotope thermoelectric generators for space power sources. Until 1984, the material was produced from small 500-g drop castings. A new process has been developed in which consumable electrodes of about 10 kg are arc melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1989 included the arc melting of three electrodes and the extruding and rolling to sheet of three billets. Significant improvements have been made in the extruding and arc-melting processes. Preliminary results show that these improvements have had an important effect in increasing the rate of blank acceptance in nondestructive evaluations. 4 refs., 33 figs., 11 tabs.
Date: November 1, 1990
Creator: Ohriner, E.K.
Partner: UNT Libraries Government Documents Department

The PEGASUS Drive: A nuclear electric propulsion system for the space exploration initiative

Description: The advantages of using electric propulsion for propulsion are well-known in the aerospace community. The high specific impulse, lower propellant requirements, and lower system mass make it a very attractive propulsion option for the Space Exploration Initiative (SEI), especially for the transport of cargo. One such propulsion system is the PEGASUS Drive (Coomes et al. 1987). In its original configuration, the PEGASUS Drive consisted of a 10-MWe power source coupled to a 6-MW magnetoplasmadynamic (MPD) thruster system. The PEGASUS Drive propelled a manned vehicle to Mars and back in 601 days. By removing the crew and their associated support systems from the spacecraft and by incorporating technology advances in reactor design and heat rejection systems, a second generation PEGASUS Drive can be developed with an alpha less than two. Utilizing this propulsion system, a 400-MT cargo vehicle, assembled and loaded in low Earth orbit (LEO), could deliver 262 MT of supplies and hardware to Mars 282 days after escaping Earth orbit. Upon arrival at Mars the transport vehicle would place its cargo in the desired parking orbit around Mars and then proceed to synchronous orbit above the desired landing sight. Using a laser transmitter, PEGASUS would provide 2-MWe on the surface to operate automated systems deployed earlier and then provide surface power to support crew activities after their arrival. The additional supplies and hardware, coupled with the availability of megawatt levels of electric power on the Mars surface, would greatly enhance and even expand the mission options being considered under SEI. 9 refs., 1 fig., 1 tab.
Date: October 1, 1990
Creator: Coomes, E.P. & Dagle, J.E.
Partner: UNT Libraries Government Documents Department

Review of liquid metal heat pipe work at Los Alamos

Description: A survey of space-power related liquid metal heat pipe work at Los Alamos National Laboratory is presented. Heat pipe development at Los Alamos has been on-going since 1963. Heat pipes were initially developed for thermionic nuclear-electrical power production in space. Since then Los Alamos has developed liquid metal heat pipes for numerous applications related to high temperature systems in both the space and terrestrial environments. Some of these applications include thermionic electrical generators, thermoelectric energy conversion (both in-core and direct radiation), thermal energy storage, hypersonic vehicle leading edge cooling, and heat pipe vapor laser cells. Some of the work performed at Los Alamos has been documented in internal reports that are often little-known. A representative description and summary of progress in space-related liquid metal heat pipe technology is provided followed by a reference section citing sources where these works may be found. 53 refs.
Date: January 1, 1990
Creator: Reid, R.S.; Merrigan, M.A. & Sena, J.T.
Partner: UNT Libraries Government Documents Department