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Aging effects of US space nuclear systems in orbit

Description: This report presents information and data in support of a cost-benefit analysis being performed by Fair child Industries (FI) on the feasibility of retrieving existing US space nuclear systems in earth orbit by the Space Shuttle. This report evaluates, for US space nuclear systems presently in orbit, the radioisotopic inventory and external radiation field as a function of time, the effect of aging on fuel containment materials over the projected lifetime of the system, and the possible radioactive source terms should reentry eventually occur. Although the radioisotopic inventories and radiation fields have been evaluated for all systems, Transit 4A and Transit Triad have been emphasized in the evaluation of the aging effects and reentry consequences because these spacecraft have the shortest projected orbital lifetimes (570 and 150 years, respectively). In addition to existing systems in orbit, the radioisotopic inventory, radiation field, and reentry source terms have been evaluated for a General Purpose Heat Source (GPHS) in a parking orbit due to an aborted Galileo Mission or International Solar Polar Mission (ISPM).
Date: May 14, 1982
Creator: Bartram, B.W.; Huang, R.; Tammara, S.R. & Thielke, N.R.
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

Low-thrust rocket trajectories

Description: The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report. 57 refs., 10 figs.
Date: January 1, 1986
Creator: Keaton, P.W.
Partner: UNT Libraries Government Documents Department

Nuclear power supplies: their potential and the practical problems to their achievement for space missions

Description: The anticipated growth of the space station power requirement provides a good example of the problem the space nuclear power supply developers have to contend with: should a reactor power supply be developed that attempts to be all things to all missions, i.e., is highly flexible in its ability to meet a wide variety of missions, or should the development of a reactor system await a specific mission definition and be customized to this mission. This leads, of course, to a chicken-and-egg situation. For power requirements of several hundreds of kilowatts or more, no nuclear power source exists or is even far enough along in the definition stage (much less the development stage) for NASA to reasonably assume probable availability within the next 10 years. The real problem of space nuclear power is this ''chicken-and-egg'' syndrome: DOE will not develop a space reactor system for NASA without a firm mission, and NASA will not specify a firm mission requiring a space reactor because such a system doesn't exist and is perceived not to be developable within the time frame of the mission. The problem is how to break this cycle. The SP-100 program has taken an important first step to breaking this cycle, but this program is much more design-specific than what is required to achieve a broad technology base and latitude in achievable power level. In contrast to the SP-100 approach, a wider perspective is required: the development of the appropriate technologies for power levels can be broken into ranges, say, from 100 kWe to 1000 kWe, and from 1000 kWe to 10,000 kWe.
Date: January 1, 1985
Creator: Colston, B.W. & Brehm, R.L.
Partner: UNT Libraries Government Documents Department

Space power technology into the 21st century

Description: This paper discusses the space power systems of the early 21st century. The focus is on those capabilities which are anticipated to evolve from today's state-of-the-art and the technology development programs presently in place or planned for the remainder of the century. The power system technologies considered include solar thermal, nuclear, radioisotope, photovoltaic, thermionic, thermoelectric, and dynamic conversion systems such as the Brayton and Stirling cycles. Energy storage technologies considered include nickel hydrogen biopolar batteries, advanced high energy rechargeable batteries, regenerative fuel cells, and advanced primary batteries. The present state-of-the-art of these space power and energy technologies is discussed along with their projections, trends and goals. A speculative future mission model is postulated which includes manned orbiting space stations, manned lunar bases, unmanned earth orbital and interplanetary spacecraft, manned interplanetary missions, military applications, and earth to space and space to space transportation systems. The various space power/energy system technologies anticipated to be operational by the early 21st century are matched to these missions.
Date: January 1, 1984
Creator: Faymon, K.A. & Fordyce, J.S.
Partner: UNT Libraries Government Documents Department

Reentry response of the light weight radioisotope heater unit resulting from a Venus-Earth-Earth Gravity Assist maneuver accident

Description: Reentry analyses consisting of ablation response, thermal response and thermal stress response have been conducted on the Light Weight Radioisotope Heater Unit for Galileo/VEEGA reentry conditions. Sequential ablation analyses of the LWRHU aeroshell, the fuel clad, and the fuel pellet have been conducted in reentry regimes where the aeroshell has been deemed to fail. The failure criterion for ablation is assumed to be recession corresponding to 50% of the wall thickness (the design criterion recommended in the DOE Overall Safety Manual). Although the analyses have been carried far beyond this limit (as presented and discussed herein), JHU/APL endorses the position that failure may occur at the time that this recession is achieved or at lower altitudes within the heat pulse considering the uncertainties in the aerodynamic, thermodynamic, and thermo-structural analyses and modeling. These uncertainties result mainly because of the high energies involved in the VEEGA reentries compared to orbital decay reentries. Risk evaluations should consider the fact that for shallow flight paths the unit may disassemble at high-altitude as a result of ablation or may remain intact until it impacts with a clad that had been molten. 80 refs., 46 figs., 16 tabs.
Date: October 1, 1988
Creator: Hagan, J.C.
Partner: UNT Libraries Government Documents Department

System aspects of a Space Nuclear Reactor Power System

Description: Selected systems aspects of a 300 kW nuclear reactor power system for spacecraft have been studied. The approach included examination of two candidate missions and their associated spacecraft, and a number of special topics dealing with the power system design and operation. The missions considered were a reusable orbital transfer vehicle and a space-based radar. The special topics included: power system configuration and scaling, launch vehicle integration, operating altitude, orbital storage, start-up, thawing, control, load following, procedures in case of malfunction, restart, thermal and nuclear radiation to other portions of the spacecraft, thermal stresses between subsystems, boom and cable designs, vibration modes, altitude control, reliability, and survivability. Among the findings are that the stowed length of the power system is important to mission design and that orbital storage for months to years may be needed for missions involving orbital assembly. The power system design evolved during the study and has continued to evolve; the current design differs somewhat from that examined in this paper.
Date: January 1, 1988
Creator: Jaffe, L.; Fujita, T.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W. et al.
Partner: UNT Libraries Government Documents Department

Coaxial tube array space transmission line characterization

Description: The coaxial tube array tether/transmission line used to connect an SP-100 nuclear power system to the space station was characterized over the range of reactor-to-platform separation distances of 1 to 10 km. Characterization was done with respect to array performance, physical dimensions and masses. Using a fixed design procedure, a family of designs was generated for the same power level (300 kWe), power loss (1.5 percent), and meteoroid survival probability (99.5 percent over 10 yr). To differentiate between vacuum insulated and gas insulated lines, two different maximum values of the E field were considered: 20 kV/cm (appropriate to vacuum insulation) and 50 kV/cm (compressed SF6). Core conductor, tube, bumper, standoff, spacer and bumper support dimensions, and masses were also calculated. The results of the characterization show mainly how transmission line size and mass scale with reactor-to-platform separation distance.
Date: January 1, 1987
Creator: Switzer, C.A. & Bents, D.J.
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

The effect of maximum-allowable payload temperature on the mass of a multimegawatt space-based platform

Description: Calculations were performed to determine the mass of a space-based platform as a function of the maximum-allowed operating temperature of the electrical equipment within the platform payload. Two computer programs were used in conjunction to perform these calculations. The first program was used to determine the mass of the platform reactor, shield, and power conversion system. The second program was used to determine the mass of the main and secondary radiators of the platform. The main radiator removes the waste heat associated with the power conversion system and the secondary radiator removes the waste heat associated with the platform payload. These calculations were performed for both Brayton and Rankine cycle platforms with two different types of payload cooling systems: a pumped-loop system (a heat exchanger with a liquid coolant) and a refrigerator system. The results indicate that increases in the maximum-allowed payload temperature offer significant platform mass savings for both the Brayton and Rankine cycle platforms with either the pumped-loop or refrigerator payload cooling systems. Therefore, with respect to platform mass, the development of high temperature electrical equipment would be advantageous. 3 refs., 24 figs., 7 tabs.
Date: August 1, 1987
Creator: Dobranich, D.
Partner: UNT Libraries Government Documents Department

Assessment of a hot hydrogen nuclear propulsion fuel test facility

Description: Subsequent to the announcement of the Space Exploration Initiative (SEI), several studies and review groups have identified nuclear thermal propulsion as a high priority technology for development. To achieve the goals of SEI to place man on Mars, a nuclear rocket will operate at near 2700K and in a hydrogen environment at near 60 atmospheres. Under these conditions, the operational lifetime of the rocket will be limited by the corrosion rate at the hydrogen/fuel interface. Consequently, the Los Alamos National Laboratory has been evaluating requirements and design issues for a test facility. The facility will be able to directly heat fuel samples by electrical resistance, microwave deposition, or radio frequency induction heating to temperatures near 3000K. Hydrogen gas at variable pressure and temperatures will flow through the samples. The thermal gradients, power density, and operating times envisioned for nuclear rockets will be duplicated as close as reasonable. The post-sample flow stream will then be scrubbed and cooled before reprocessing. The baseline design and timetable for the facility will be discussed. 7 refs.
Date: January 1, 1991
Creator: Watanabe, H.H.; Howe, S.D. & Wantuck, P.J.
Partner: UNT Libraries Government Documents Department

Light-Weight Radioisotope Heater Unit Final Safety Analysis Report (LWRHU FSAR): Volume 3, Nuclear Risk Analysis Document

Description: The Light-Weight Radioisotope Heater Unit (LWRHU) Final Safety Analysis Report (FSAR), Volume 2, Accident Model Document (AMD) describes potential accident scenarios during the Galileo mission and evaluates the response of the LWRHUs to the associated accident environments. Any resulting source terms, consisting of PuO2 (with Pu-238 the dominant radionuclide), are then described in terms of curies released, particle size distribution, release location, and probabilities. This volume (LWRHU-FSAR, Volume 3, Nuclear Risk Analysis Document (NRAD)) contains the radiological analyses which estimate the consequences of the accident scenarios described in the AMD. It also contains the quantification of mission risks resulting from the LWRHUs based on consideration of all accident scenarios and their probabilities. Estimates of source terms and their characteristics derived in the AMD are used as inputs to the analyses in the NRAD. The Failure Abort Sequence Trees (FASTs) presented in the AMD define events for which source terms occur and quantify them. Based on this information, three types of source term cases (most probable, maximum, and expectation) for each mission phase were developed for use in evaluating the radiological consequences and mission risks. 4 refs., 5 figs., 8 tabs.
Date: November 30, 1988
Partner: UNT Libraries Government Documents Department

High power density reactors based on direct cooled particle beds

Description: Reactors based on direct cooled HTGR type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out long the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBR's) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed. 12 figs.
Date: January 1, 1985
Creator: Powell, J.R. & Horn, F.L.
Partner: UNT Libraries Government Documents Department

Low gravity fluid-thermal experiments

Description: Pacific Northwest Laboratory (PNL) is the lead laboratory for the thermal-hydraulic research in the US Department of Energy Multimegawatt Space Nuclear Power Program. PNL must provide the tools necessary to analyze proposed space reactor concepts, which include single- and two-phase alkali metal and gas-cooled designs. PNL has divided its activities for this task into three basic areas: computer code development, thermal-hydraulic modeling, and experimentation. The subject of this paper is the low-gravity experimental program currently underway at PNL in support of the MMW Program.
Date: June 1, 1987
Creator: Krotiuk, W.J. & Cuta, J.M.
Partner: UNT Libraries Government Documents Department

Mission maps for use in the choice of specific impulse for manned Mars missions

Description: The choice of engine concept for the initial manned missions to Mars should be driven by what can be feasibly built and flight qualified in the near term, and by the level of engine performance that is required for these missions. This paper addresses how mission requirements affect the choice of specific impulse, and consequently what values of the specific impulse best serve these missions. Broad mission surveys and sensitivity studies were performed to determine the specific impulse values that allow for fast transfer times and wide launch windows. We find that a specific impulse of around 1000 to 1200 sec is sufficient. Choosing an engine concept that has a higher specific impulse value is not justified for these missions because the modest reduction in propellant requirements and further widening of the launch windows does not compensate for the substantially greater technical risk. 3 refs., 8 figs.
Date: January 1, 1991
Creator: Madsen, W.W.; Neuman, J.E.; Olson, T.S. & Siahpush, A.S.
Partner: UNT Libraries Government Documents Department

An alternative strategy for low specific power reactors to power interplanetary spacecraft, based on exploiting lasers and lunar resources

Description: A key requirement setting the minimum electric propulsion performance (specific power ..cap alpha../sub e/ = kW/sub e//kg) for manned missions to Mars is the maximum allowable radiation dose to the crew during the long transits between Earth and Mars. Penetrating galactic cosmic rays and secondary neutron showers give about 0.1-rem/day dose, which only massive shielding (e.g., a meter of concrete) can reduce significantly. With a humane allowance for cabin space, the shielding mass becomes so large that it prohibitively escalates the propellant consumption required for reasonable trip times. This paper covers various proposed methods for using reactor power to propel spacecraft. 7 refs., 6 figs., 1 tab.
Date: February 2, 1989
Creator: Logan, B.G.
Partner: UNT Libraries Government Documents Department

Nuclear reactor power as applied to a space-based radar mission

Description: The SP-100 Project was established to develop and demonstrate feasibility of a space reactor power system (SRPS) at power levels of 10's of kilowatts to a megawatt. To help determine systems requirements for the SRPS, a mission and spacecraft were examined which utilize this power system for a space-based radar to observe moving objects. Aspects of the mission and spacecraft bearing on the power system were the primary objectives of this study; performance of the radar itself was not within the scope. The study was carried out by the Systems Design Audit Team of the SP-100 Project. (3 refs., 6 figs., 2 tabs.)
Date: January 1, 1988
Creator: Jaffe, L.; Fujita, T.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W. et al.
Partner: UNT Libraries Government Documents Department

Nuclear reactor power for an electrically powered orbital transfer vehicle

Description: To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to Earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.
Date: January 1, 1987
Creator: Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R. et al.
Partner: UNT Libraries Government Documents Department

Multimegawatt space nuclear power supply: Phase 1, Final report

Description: The Phase 2 program objectives are to (1) demonstrate concept feasibility, (2) develop a preliminary design, and (3) complete Phase 3 engineering development and ground test plans. The approach to accomplish these objectives is to prove technical feasibility of our baseline design early in the program while maintaining flexibility to easily respond to changing requirements and advances in technology. This approach recognizes that technology is advancing rapidly while the operational phase MSNPS is 15 to 20 years in the future. This plan further recognizes that the weapons platform and Advanced Launch System (ALS) are in very early program definition stages; consequently, their requirements, interfaces, and technological basis will evolve. This document outlines the Phase 2 plan along with task scheduling of the various program aspects.
Date: February 17, 1989
Partner: UNT Libraries Government Documents Department

Multimegawatt space nuclear power supply: Phase 1, Final report

Description: The preliminary safety assessment report analyzes the potential radiological risk of the integrated MSNPS with the launch vehicle including interface with the weapon system. Most emphasis will be placed the prime power concept design. Safety problems can occur any time during the entire life cycle of the system including contingency phases. The preliminary safety assessment report is to be delivered at the end of phase 2. This assessment will be the basis of the safety requirements which will be applied to the design of the MSNPS as it develops in subsequent phases. The assessment also focuses design activities on specific high-risk scenarios and missions that may impact safety.
Date: February 17, 1989
Partner: UNT Libraries Government Documents Department

Multimegawatt space nuclear power supply, Phase 1 Final report

Description: This Specification establishes the performance, design, development, and test requirements for the Boeing Multimegawatt Space Nuclear Power System (MSNPS). The Boeing Multimegawatt Space Power System is part of the DOE/SDIO Multimegawatt Space Nuclear Power Program. The purpose of this program is to provide a space-based nuclear power system to meet the needs of SDIO missions. The Boeing MSNPS is a category 1 concept which is capable of delivering 10's of MW(e) for 100's of seconds with effluent permitted. A design goal is for the system to have growth or downscale capability for other power system concepts. The growth objective is to meet the category 3 capability of 100's of MW(e) for 100's of seconds, also with effluent permitted. The purpose of this preliminary document is to guide the conceptual design effort throughout the Phase 1 study effort. This document will be updated through out the study. It will thus result in a record of the development of the design effort.
Date: February 17, 1989
Partner: UNT Libraries Government Documents Department