Greater power levels were pursued and in 1965,SNAP-10A,the only nuclear fission electrical power system launched by the U.S.,was placed in Earth orbit.The system was designed to produce 30kW of thermal power and 500 W of electrical power.0 The system was placed in a planned 4,000-year lifetime Earth orbit and,after successful startup and operation,was shut down due to a series of spurious electronic signals.The SNAP-10A also flight tested electric propulsion cesium ion thrusters although the results were inconclusive.12 The U.S.program continued to pursue higher performing RTG power systems rather than reactor systems in contrast to the Soviet Union which focused their efforts primarily on reactor based systems.Interestingly the Soviet Union has orbited approximately 35 reactor based power systems.3 After approximately a decade long gap the U.S.began once again to investigate reactor systems,and in 1979 the Space Power Advanced Reactor (SPAR)Program was initiated to address anticipated space power needs.14 The SP-100 program that was initiated in 1983 as a joint program between NASA,the Department of Defense(DOD)and the Department of Energy(DOE)evolved from the SPAR program.The goal of SP-100 was to develop the nuclear and power technologies necessary to provide tens to hundreds of kilowatts of electrical power for seven years at full power over ten years of operation.Applications were targeted for both future military and civilian missions.NASA presented potential civil applications to the House of Representatives,Subcommittee on Energy Research and Development,in March 1988 with the following chart in Figure 5. 27
Greater power levels were pursued and in 1965, SNAP-10A, the only nuclear fission electrical power system launched by the U.S., was placed in Earth orbit. The system was designed to produce 30kW of thermal power and 500 W of electrical power.10 The system was placed in a planned 4,000-year lifetime Earth orbit and, after successful startup and operation, was shut down due to a series of spurious electronic signals.11 The SNAP-10A also flight tested electric propulsion cesium ion thrusters although the results were inconclusive.12 The U.S. program continued to pursue higher performing RTG power systems rather than reactor systems in contrast to the Soviet Union which focused their efforts primarily on reactor based systems. Interestingly the Soviet Union has orbited approximately 35 reactor based power systems.13 After approximately a decade long gap the U.S. began once again to investigate reactor systems, and in 1979 the Space Power Advanced Reactor (SPAR) Program was initiated to address anticipated space power needs.14 The SP-100 program that was initiated in 1983 as a joint program between NASA, the Department of Defense (DOD) and the Department of Energy (DOE) evolved from the SPAR program. The goal of SP-100 was to develop the nuclear and power technologies necessary to provide tens to hundreds of kilowatts of electrical power for seven years at full power over ten years of operation. Applications were targeted for both future military and civilian missions. NASA presented potential civil applications to the House of Representatives, Subcommittee on Energy Research and Development, in March 1988 with the following chart in Figure 5. 27
LONG-RANGE FORECAST POTENTIAL CIVIL APPLICATIONS 一⊙AS￥ INNER SOLAR SYSTEM ASTERTURNPLE MARS/PHOBOS BASE MARS SETTLEMENT RENDETVOUS/ERPLORER MAIRANSPORT VEICLERY M能E CATRANSPORT VENICLEY co是TUANPLE EARTH-MOON SYSTEM ORDITENSPROB。 LUNAR SETTLEMENT LAPOBSERVATOHY AR A先 TEPLORERU L1 UBRATION BASE AI ADAR STATION OL EARTH ORBIT MO票PRG ORBITAL怎SEMOLY BASES GEO DEPOT/BASE Fig.1 Figure 5:SP-100 Chart used in 1988 Congressional Testimony The SP-100 program made significant progress in understanding the technologies required for development of space reactor power systems,but unfortunately was cancelled in 1992 before any of the planned reactor flights.It should be noted that in this same time period there was a DOE,NASA and DOD effort to formulate design concepts for the Multimegawatt Program that investigated high power systems for a variety of military and civilian applications.This aspect of the program separated from NASA and continued under the Reagan Administration's space defense initiatives.These programs,like similar programs that preceded them,had difficulty in retaining and articulating a true mission need.It can be theorized that having such a large power 28
Figure 5: SP-100 Chart used in 1988 Congressional Testimony The SP-100 program made significant progress in understanding the technologies required for development of space reactor power systems, but unfortunately was cancelled in 1992 before any of the planned reactor flights. It should be noted that in this same time period there was a DOE, NASA and DOD effort to formulate design concepts for the Multimegawatt Program that investigated high power systems for a variety of military and civilian applications. This aspect of the program separated from NASA and continued under the Reagan Administration’s space defense initiatives. These programs, like similar programs that preceded them, had difficulty in retaining and articulating a true mission need. It can be theorized that having such a large power 28
range,tens to hundreds of kW,and a variety of mission requirements,ranging from survivable military reconnaissance platforms and directed energy weapons to civilian human piloted missions,actually diffused the mission purpose to the point that a single compelling need was lost to justify continuance.That is one reason why this thesis focuses on a narrower power and applications range. Recent efforts in the early 90's,with the Space Exploration Initiative (SEI), announced by President Bush in 1989,once again introduced the possibility of including nuclear technologies in the suite of enabling space technologies.However after a few years of study this also failed to achieve Congressional support due to the perceived development costs of a human Moon,Mars and interplanetary exploration program. The SEI effort did provide a temporary resurgence and interest in nuclear space systems and,at a minimum,allowed NASA and others to provide an updated assessment of technology requirements and required investments to complete such a family of missions. Accidents are also a very important part of nuclear space history,as nuclear incidents have a direct bearing on future policy,program structure and architectures. There have been four failures of U.S.nuclear space activities in either the launch or in- space operations phase of the mission.Three involved Radioisotope Thermoelectric Generators(RTGs)and the forth involved the one and only U.S.flight reactor.In 1964 a Transit 5B navigation satellite failed to achieve orbit and burned up in the upper atmosphere as designed.The second involved the 1965 SNAP-10 reactor that shut down early and remains in a nuclear safe orbit.The third incident occurred in 1968 during the first minute into the launch of a Nimbus weather satellite.After the launch vehicle malfunctioned and was destroyed,the RTGs fell into the Santa Barbara Channel but were 29
range, tens to hundreds of kW, and a variety of mission requirements, ranging from survivable military reconnaissance platforms and directed energy weapons to civilian human piloted missions, actually diffused the mission purpose to the point that a single compelling need was lost to justify continuance. That is one reason why this thesis focuses on a narrower power and applications range. Recent efforts in the early 90’s, with the Space Exploration Initiative (SEI), announced by President Bush in 1989, once again introduced the possibility of including nuclear technologies in the suite of enabling space technologies. However after a few years of study this also failed to achieve Congressional support due to the perceived development costs of a human Moon, Mars and interplanetary exploration program. The SEI effort did provide a temporary resurgence and interest in nuclear space systems and, at a minimum, allowed NASA and others to provide an updated assessment of technology requirements and required investments to complete such a family of missions. Accidents are also a very important part of nuclear space history, as nuclear incidents have a direct bearing on future policy, program structure and architectures. There have been four failures of U.S. nuclear space activities in either the launch or inspace operations phase of the mission. Three involved Radioisotope Thermoelectric Generators (RTGs) and the forth involved the one and only U.S. flight reactor. In 1964 a Transit 5B navigation satellite failed to achieve orbit and burned up in the upper atmosphere as designed. The second involved the 1965 SNAP-10 reactor that shut down early and remains in a nuclear safe orbit. The third incident occurred in 1968 during the first minute into the launch of a Nimbus weather satellite. After the launch vehicle malfunctioned and was destroyed, the RTGs fell into the Santa Barbara Channel but were 29
subsequently recovered.The last failure was the reentry of the Apollo XIII lunar module in 1970 that carried RTGs.The RTGs reentered with the lunar module and survived reentry intact.The Apollo XIII RTGs remain at the bottom of the South Pacific Ocean where they are presumed to be intact.In each case the safety design features remedied any adverse consequences that may have resulted from the nuclear material. The Soviet space program was not as fortunate,and in 1978 caused an international incident with the reentry of the Cosmos 954 nuclear reactor powered satellite over Canada's Northwest Territories.The reactor was designed to burn-up on reentry,however debris was found over a 600 km tract.'5 Although no large fuel particles were found,several large metallic fragments with high radioactivity levels were discovered.16 This event was highly significant and focused world attention on safety and policy issues associated with the use of nuclear space power systems. In summary,over the last 50 years,mission requirements behind the various space nuclear programs have changed dramatically as the driving forces have moved from intercontinental ballistic missiles through the different phases of the Cold War competition.These forces have caused investments in technologies to rise and fall and with them national infrastructure and capabilities.The challenge today is to provide a focused mission requirement that can be clearly communicated and maintained throughout the development program.This also must be accompanied by reinvigorating national capability to deliver on such systems in a safe manner. 3.2 Recent and Relevant Program Results As noted earlier the SP-100 program has made the most significant recent progress in the understanding and development of space based reactor power systems. 30
subsequently recovered. The last failure was the reentry of the Apollo XIII lunar module in 1970 that carried RTGs. The RTGs reentered with the lunar module and survived reentry intact. The Apollo XIII RTGs remain at the bottom of the South Pacific Ocean where they are presumed to be intact. In each case the safety design features remedied any adverse consequences that may have resulted from the nuclear material. The Soviet space program was not as fortunate, and in 1978 caused an international incident with the reentry of the Cosmos 954 nuclear reactor powered satellite over Canada’s Northwest Territories. The reactor was designed to burn-up on reentry, however debris was found over a 600 km tract.15 Although no large fuel particles were found, several large metallic fragments with high radioactivity levels were discovered. 16 This event was highly significant and focused world attention on safety and policy issues associated with the use of nuclear space power systems. In summary, over the last 50 years, mission requirements behind the various space nuclear programs have changed dramatically as the driving forces have moved from intercontinental ballistic missiles through the different phases of the Cold War competition. These forces have caused investments in technologies to rise and fall and with them national infrastructure and capabilities. The challenge today is to provide a focused mission requirement that can be clearly communicated and maintained throughout the development program. This also must be accompanied by reinvigorating national capability to deliver on such systems in a safe manner. 3.2 Recent and Relevant Program Results As noted earlier the SP-100 program has made the most significant recent progress in the understanding and development of space based reactor power systems. 30
The program began with over 100 different concepts for the reactor system and competed liquid metal,gas cooled,thermionic and heat pipe reactors in combination with various thermoelectric,thermionic,Brayton,Rankine and Stirling energy conversion systems. The program selected twelve and then three concepts for further evaluation and development,which were:1)High temperature,liquid metal cooled,pin-fuel element reactor with thermoelectric conversion 2)an in-core thermionic power system,and 3)a low-temperature,liquid metal cooled,pin-fuel element reactor with Stirling cycle conversion.7 In 1985 the program selected the high temperature liquid metal (lithium) pin-fuel element reactor with thermoelectric conversion for development to flight readiness although some work continued on technologies that supported alternative architectures.This activity proceeded through design,analysis,development and component testing before cancellation.In the same time period of SP-100,the Soviet Union orbited a new generation of nuclear reactors,named Topaz I,that evolved from thermoelectric systems to multi-cell in-core thermionic systems in the range of 5 kW.s The design,analysis,component development and alternative architectures investigated under SP-100 represent the most recent and comprehensive efforts to date to develop a space based nuclear power system with the required power ranges for NEPP systems.A significant amount of information existed in industry,academia and government on many aspects of this activity.However the momentum of industry investments and industry support of concepts is critical for success in government projects and this momentum has fundamentally been lost over the last 10 years. Exceptions to this are advancements in non-nuclear power components such as radiators, electronic propulsion devices and power electronics.One consequence of this is that at 31
The program began with over 100 different concepts for the reactor system and competed liquid metal, gas cooled, thermionic and heat pipe reactors in combination with various thermoelectric, thermionic, Brayton, Rankine and Stirling energy conversion systems. The program selected twelve and then three concepts for further evaluation and development, which were: 1) High temperature, liquid metal cooled, pin-fuel element reactor with thermoelectric conversion 2) an in-core thermionic power system, and 3) a low-temperature, liquid metal cooled, pin-fuel element reactor with Stirling cycle conversion.17 In 1985 the program selected the high temperature liquid metal (lithium) pin-fuel element reactor with thermoelectric conversion for development to flight readiness although some work continued on technologies that supported alternative architectures. This activity proceeded through design, analysis, development and component testing before cancellation. In the same time period of SP-100, the Soviet Union orbited a new generation of nuclear reactors, named Topaz I, that evolved from thermoelectric systems to multi-cell in-core thermionic systems in the range of 5 kW. 18 The design, analysis, component development and alternative architectures investigated under SP-100 represent the most recent and comprehensive efforts to date to develop a space based nuclear power system with the required power ranges for NEPP systems. A significant amount of information existed in industry, academia and government on many aspects of this activity. However the momentum of industry investments and industry support of concepts is critical for success in government projects and this momentum has fundamentally been lost over the last 10 years. Exceptions to this are advancements in non-nuclear power components such as radiators, electronic propulsion devices and power electronics. One consequence of this is that at 31