134-579: Project Rover was a United States project to develop a nuclear-thermal rocket that ran from 1955 to 1973 at the Los Alamos Scientific Laboratory (LASL). It began as a United States Air Force project to develop a nuclear-powered upper stage for an intercontinental ballistic missile (ICBM). The project was transferred to NASA in 1958 after the Sputnik crisis triggered the Space Race . It
268-451: A thrust-to-weight ratio of 1:1, which is needed to overcome the gravity of the Earth at launch. Over the next twenty-five years, U.S. nuclear thermal rocket designs eventually reached thrust-to-weight ratios of approximately 7:1. This is still a much lower thrust-to-weight ratio than what is achievable with chemical rockets, which have thrust-to-weight ratios on the order of 70:1. Combined with
402-532: A 10,000 MW nuclear rocket engine capable of launching 11,000 kilograms (25,000 lb) into a 480 kilometers (300 mi) orbit. This engine was codenamed Condor, after the large flying birds , in contrast to the small flightless Kiwi. However, in October 1958, NASA had studied putting a nuclear upper stage on a Titan I missile, and concluded that in this configuration a 1,000 MW reactor upper stage could put 6,400 kilograms (14,000 lb) into orbit. This configuration
536-460: A 4,000 MW reactor with an 89-centimeter (35 in) core as a successor to Kiwi. LASL decided to name it Phoebe , after the Greek Moon goddess. Another nuclear weapon project already had that name, though, so it was changed to Phoebus, an alternative name for Apollo. Phoebus ran into opposition from SNPO, which wanted a 20,000 MW reactor. LASL thought that the difficulties of building and testing such
670-485: A consortium of companies to conduct a study on electric thrusters powered by nuclear energy, known as Nuclear Electric Propulsion. The study outlines the roadmap for the launch of a nuclear propulsion demonstrator in 2035. Current solid-core nuclear thermal rocket designs are intended to greatly limit the dispersion and break-up of radioactive fuel elements in the event of a catastrophic failure. As of 2013, an NTR for interplanetary travel from Earth orbit to Mars orbit
804-435: A conventional engine could produce an exhaust velocity of 2,500 meters per second (8,300 ft/s), a hydrogen-fueled nuclear engine could attain an exhaust velocity of 6,900 meters per second (22,700 ft/s) under the same conditions. He proposed a graphite-moderated reactor due to graphite's ability to withstand high temperatures and concluded that the fuel elements would require protective cladding to withstand corrosion by
938-417: A coolant and as a moderator to reduce the amount of uranium oxide required. The control rods were located inside the island, which was surrounded by 960 graphite fuel plates loaded with 4-micrometer (0.00016 in) uranium oxide fuel particles and a layer of 240 graphite plates. The core was surrounded by 43.2 centimeters (20 in) of graphite wool moderator and encased in an aluminum shell. Gaseous hydrogen
1072-452: A factor of 2 to 100 compared to conventional nuclear fuels . Fission-fragment rocket using Am was proposed by George Chapline at Lawrence Livermore National Laboratory (LLNL) in 1988, who suggested propulsion based on the direct heating of a propellant gas by fission fragments generated by a fissile material. Ronen et al. demonstrate that Am can maintain sustained nuclear fission as an extremely thin metallic film, less than 1/1000 of
1206-542: A given design, the temperature that can be attained is typically determined by the materials chosen for reactor structures, the nuclear fuel, and the fuel cladding. Erosion is also a concern, especially the loss of fuel and associated releases of radioactivity. Solid core nuclear reactors have been fueled by compounds of uranium that exist in solid phase under the conditions encountered and undergo nuclear fission to release energy. Flight reactors must be lightweight and capable of tolerating extremely high temperatures, as
1340-414: A heat source releases thermal energy into a gaseous propellant inside the body of the engine, and a nozzle at one end acts as a very simple heat engine: it allows the propellant to expand away from the vehicle, carrying momentum with it and converting thermal energy to coherent kinetic energy. The specific impulse (Isp) of the engine is set by the speed of the exhaust stream. That, in turn, varies as
1474-434: A large paper surveying many of the problems involved in using nuclear reactors to power airplanes and rockets. The study was specifically aimed at an aircraft with a range of 16,000 kilometers (10,000 mi) and a payload of 3,600 kilograms (8,000 lb), and covered turbopumps , structure, tankage, aerodynamics and nuclear reactor design. They concluded that hydrogen was best as a propellant and that graphite would be
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#17328631333271608-623: A large reactor were being taken too lightly; just to build the 4,000 MW design required a new nozzle and improved turbopump from Rocketdyne. A prolonged bureaucratic conflict ensued. In March 1963, SNPO and the Marshall Space Flight Center (MSFC) commissioned Space Technology Laboratories (STL) to produce a report on what kind of nuclear rocket engine would be required for possible missions between 1975 and 1990. These missions included early manned planetary interplanetary round-trip expeditions (EMPIRE), planetary swingbys and flybys, and
1742-537: A larger design in the Space Thermal Nuclear Propulsion (STNP) program. Advances in high-temperature metals, computer modeling, and nuclear engineering, in general, resulted in dramatically improved performance. While the NERVA engine was projected to weigh about 6,803 kilograms (14,998 lb), the final STNP offered just over 1/3 the thrust from an engine of only 1,650 kilograms (3,640 lb) by improving
1876-543: A lunar shuttle. The conclusion of this nine-volume report, which was delivered in March 1965, and of a follow-up study, was that these missions could be carried out with a 4,100 MW engine with a specific impulse of 825 seconds (8.09 km/s). This was considerably smaller than had originally been thought necessary. From this emerged a specification for a 5,000 MW nuclear rocket engine, which became known as NERVA II. Nuclear thermal rocket A nuclear thermal rocket ( NTR )
2010-453: A marginally reduced fuel cost. Yet another mark in favor of hydrogen is that at low pressures it begins to dissociate at about 1500 K, and at high pressures around 3000 K. This lowers the mass of the exhaust species, increasing I sp . Early publications were doubtful of space applications for nuclear engines. In 1947, a complete nuclear reactor was so heavy that solid core nuclear thermal engines would be entirely unable to achieve
2144-524: A millimeter thick. Am requires only 1% of the mass of U or Pu to reach its critical state. Ronen's group at the Ben-Gurion University of the Negev further showed that nuclear fuel based on Am could speed space vehicles from Earth to Mars in as little as two weeks. The Am as a nuclear fuel is derived from the fact that it has the highest thermal fission cross section (thousands of barns ), about 10x
2278-553: A new technology that promised heavier payloads over longer distances seemed weak. However, the nuclear rocket had acquired a powerful political patron in Senator Clinton P. Anderson from New Mexico (where LASL was located), the deputy chairman of the United States Congress Joint Committee on Atomic Energy (JCAE), who was close to von Neumann, Bradbury and Ulam. He managed to secure funding. All work on
2412-527: A novel type of nuclear rocket . Since the thermal absorption cross section of Am is very high, the best way to obtain Am is by the capture of fast or epithermal neutrons in Americium-241 irradiated in a fast reactor . However, fast spectrum reactors are not readily available. Detailed analysis of Am breeding in existing pressurized water reactors (PWRs) was provided. Proliferation resistance of Am
2546-405: A nozzle cooled by liquid hydrogen instead of water, a new Rocketdyne turbopump, and a bootstrap start, in which the reactor was started up under its own power only. The test of Kiwi B1A, the last test to use gaseous hydrogen instead of liquid, was initially scheduled for 7 November 1961. On the morning of the test, a leaking valve resulted in a violent hydrogen explosion that blew out the walls of
2680-554: A nuclear space engine, as well as previous tests of fuel rods and ion engines . Development of solid core NTRs started in 1955 under the Atomic Energy Commission (AEC) as Project Rover and ran to 1973. Work on a suitable reactor was conducted at Los Alamos National Laboratory and Area 25 (Nevada National Security Site) in the Nevada Test Site . Four basic designs came from this project: KIWI, Phoebus, Pewee, and
2814-594: A physicist working on the Nuclear Energy for the Propulsion of Aircraft (NEPA) project at the Oak Ridge National Laboratory , wrote a detailed study. He had read Cleaver and Shepard's work, that of Tsien, and a February 1952 report by engineers at Consolidated Vultee . He used data and analyses from existing chemical rockets, along with specifications for existing components. His calculations were based on
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#17328631333272948-599: A propellant gas. Project 242 studied the application of this propulsion system to a crewed mission to Mars. Preliminary results were very satisfactory, and it has been observed that a propulsion system with these characteristics could make the mission feasible. Another study focused on the production of Am in conventional thermal nuclear reactors. In 2022, the European Space Agency launched an initiative called "Preliminary European Reckon on Nuclear Electric Propulsion for Space Applications" (RocketRoll) and commissioned
3082-486: A redesign. Attention then switched to B4, a more radical design, but when they tried to put the fuel clusters into the core, the clusters were found to have too many neutrons, and it was feared that the reactor might unexpectedly start up. The problem was traced to absorption of water from the normally dry New Mexico air during storage. It was corrected by adding more neutron poison. After this, fuel elements were stored in an inert atmosphere. N Division then decided to test with
3216-570: A rocket propellant, was involved in the Aircraft Nuclear Propulsion (ANP) project, built NASA's Plum Brook Reactor , and had created a nuclear rocket propulsion group at Lewis under Harold Finger . Responsibility for the non-nuclear components of Project Rover was officially transferred from the United States Air Force (USAF) to NASA on 1 October 1958, the day NASA officially became operational and assumed responsibility for
3350-483: A series of "cold flow" reactor tests using fuel elements without fissionable material. Nitrogen, helium and hydrogen gas was pumped through the engine to induce vibrations. It was determined that they were caused by instability in the way the liquid flowed through the clearance gaps between adjacent fuel elements. A series of minor design changes were made to address the vibration problem. In the Kiwi B4D test on 13 May 1964,
3484-434: A series of groundbreaking scientific papers that considered how nuclear technology might be applied to interplanetary travel . The papers examined both nuclear-thermal and nuclear-electric propulsion. Through Project Rover , Los Alamos National Laboratory began developing nuclear thermal engines as soon as 1955 and tested the world's first experimental nuclear rocket engine, KIWI-A , in 1959. This work at Los Alamos
3618-439: A set temperature is reached, the reactor is quickly turned off again. During these pulses, the power being produced is far greater than the same sized reactor could produce continually. The key to this approach is that while the total amount of fuel that can be pumped through the reactor during these brief pulses is small, the resulting efficiency of these pulses is much higher. Generally, the designs would not be operated solely in
3752-720: A single main gate into the storage area, which then separated into seven spurs. Two spurs led into 55.3-square-meter (595 sq ft) bunkers. The facility was used to store a wide variety of radioactively contaminated items. In February 1962, NASA announced the establishment of the Nuclear Rocket Development Station (NRDS) at Jackass Flats, and in June an SNPO branch was established at Las Vegas (SNPO-N) to manage it. Construction workers were housed in Mercury, Nevada . Later thirty trailers were brought to Jackass Flats to create
3886-609: A theoretical maximum specific impulse that is 3 to 4.5 times greater than those of chemical rockets. In 1944, Stanisław Ulam and Frederic de Hoffmann contemplated the idea of controlling the power of nuclear explosions to launch space vehicles. After World War II, the U.S. military started the development of intercontinental ballistic missiles (ICBM) based on the German V-2 rocket designs. Some large rockets were designed to carry nuclear warheads with nuclear-powered propulsion engines. As early as 1946, secret reports were prepared for
4020-448: A village named "Boyerville" after the supervisor, Keith Boyer. The first phase of Project Rover, Kiwi, was named after the flightless bird of the same name from New Zealand, as the Kiwi rocket engines were not intended to fly either. Their function was to verify the design and test the behavior of the materials used. The Kiwi program developed a series of non-flyable test nuclear engines, with
4154-415: Is a type of thermal rocket where the heat from a nuclear reaction replaces the chemical energy of the propellants in a chemical rocket . In an NTR, a working fluid , usually liquid hydrogen , is heated to a high temperature in a nuclear reactor and then expands through a rocket nozzle to create thrust . The external nuclear heat source theoretically allows a higher effective exhaust velocity and
Project Rover - Misplaced Pages Continue
4288-508: Is being studied at Marshall Space Flight Center with Glenn Research Center . In historical ground testing, NTRs proved to be at least twice as efficient as the most advanced chemical engines, which would allow for quicker transfer time and increased cargo capacity. The shorter flight duration, estimated at 3–4 months with NTR engines, compared to 6–9 months using chemical engines, would reduce crew exposure to potentially harmful and difficult to shield cosmic rays . NTR engines, such as
4422-635: Is expected to double or triple payload capacity compared to chemical propellants that store energy internally. NTRs have been proposed as a spacecraft propulsion technology, with the earliest ground tests occurring in 1955. The United States maintained an NTR development program through 1973 when it was shut down for various reasons, including to focus on Space Shuttle development. Although more than ten reactors of varying power output have been built and tested, as of 2024 , no nuclear thermal rocket has flown. Whereas all early applications for nuclear thermal rocket propulsion used fission processes, research in
4556-503: Is proposed to operate at temperatures above the melting point of solid nuclear fuel and cladding, with the maximum operating temperature of the engine instead of being determined by the reactor pressure vessel and neutron reflector material. The higher operating temperatures would be expected to deliver specific impulse performance on the order of 1300 to 1500 seconds (12.8-14.8 kN·s/kg). A liquid-core reactor would be extremely difficult to build with current technology. One major issue
4690-415: Is that the reaction time of the nuclear fuel is much longer than the heating time of the working fluid. If the nuclear fuel and working fluid are not physically separated, this means that the fuel must be trapped inside the engine while the working fluid is allowed to easily exit through the nozzle. One possible solution is to rotate the fuel/fluid mixture at very high speeds to force the higher-density fuel to
4824-400: Is then cooled, typically using water. In the case of a nuclear engine, the water is replaced by hydrogen, but the concept is otherwise similar. Pulsed reactors attempt to transfer the energy directly from the neutrons to the working mass, allowing the exhaust to reach temperatures far beyond the melting point of the reactor core. As specific impulse varies directly with temperature, capturing
4958-688: The Applied Physics Laboratory published their research on nuclear power propulsion and their report was eventually classified. In May 1947, American-educated Chinese scientist Qian Xuesen presented his research on "thermal jets" powered by a porous graphite-moderated nuclear reactor at the Nuclear Science and Engineering Seminars LIV organized by the Massachusetts Institute of Technology . In 1948 and 1949, physicist Leslie Shepherd and rocket scientist Val Cleaver produced
5092-510: The U.S. Air Force , as part of the NEPA project , by North American Aviation and Douglas Aircraft Company 's Project Rand . These groundbreaking reports identified a reactor engine in which a working fluid of low molecular weight is heated using a nuclear reactor as the most promising form of nuclear propulsion but identified many technical issues that needed to be resolved. In January 1947, not aware of this classified research, engineers of
5226-426: The "open cycle", the losses of nuclear fuel would be difficult to control, which has led to studies of the "closed cycle" or nuclear lightbulb engine, where the gaseous nuclear fuel is contained in a super-high-temperature quartz container, over which the hydrogen flows. The closed-cycle engine has much more in common with the solid-core design, but this time is limited by the critical temperature of quartz instead of
5360-729: The 2010s has moved to fusion approaches. The Direct Fusion Drive project at the Princeton Plasma Physics Laboratory is one such example, although "energy-positive fusion has remained elusive". In 2019, the U.S. Congress approved US$ 125 million in development funding for nuclear thermal propulsion rockets. In May 2022 DARPA issued an RFP for the next phase of their Demonstration Rocket for Agile Cislunar Operations (DRACO) nuclear thermal engine program. This follows on their selection, in 2021, of an early engine design by General Atomics and two spacecraft concepts from Blue Origin and Lockheed Martin . The next phases of
5494-604: The Deputy Director of the Los Alamos Scientific Laboratory (LASL), and Herbert York , the director of the University of California Radiation Laboratory at Livermore , were interested, and established committees to investigate nuclear rocket propulsion. Froman brought Bussard out to Los Alamos to assist for one week per month. Robert Bussard's study also attracted the attention of John von Neumann , and he formed an ad hoc committee on Nuclear Propulsion of Missiles. Mark Mills ,
Project Rover - Misplaced Pages Continue
5628-603: The Earth's atmosphere and perhaps even magnetosphere . The final fission classification is the gas-core engine . This is a modification to the liquid-core design which uses rapid circulation of the fluid to create a toroidal pocket of gaseous uranium fuel in the middle of the reactor, surrounded by hydrogen. In this case, the fuel does not touch the reactor wall at all, so temperatures could reach several tens of thousands of degrees, which would allow specific impulses of 3000 to 5000 seconds (30 to 50 kN·s/kg). In this basic design,
5762-466: The I sp to between 930 and 1000 seconds. KIWI was the first to be fired, starting in July 1959 with KIWI 1. The reactor was not intended for flight and was named after the flightless bird , Kiwi. The core was simply a stack of uncoated uranium oxide plates onto which the hydrogen was dumped. The thermal output of 70 MW at an exhaust temperature of 2683 K was generated. Two additional tests of
5896-562: The Nuclear Furnace. Progressively higher power densities culminated in the Pewee. Tests of the improved Pewee 2 design were canceled in 1970 in favor of the lower-cost Nuclear Furnace (NF-1), and the U.S. nuclear rocket program officially ended in the spring of 1973. During this program, the NERVA accumulated over 2 hours of run time, including 28 minutes at full power. The SNPO considered NERVA to be
6030-570: The Nuclear Furnace. Twenty individual engines were tested, with a total of over 17 hours of engine run time. When NASA was formed in 1958, it was given authority over all non-nuclear aspects of the Rover program. To enable cooperation with the AEC and keep classified information compartmentalized, the Space Nuclear Propulsion Office (SNPO) was formed at the same time. The 1961 NERVA program
6164-630: The Pajarito Canyon Site. They were tested there at very low power and then shipped to Area 25 (known as Jackass Flats) at the AEC's Nevada Test Site . Testing of fuel elements and other materials science was done by the LASL N-Division at TA-46 using various ovens and later a custom test reactor, the Nuclear Furnace. Project Rover resulted in the development of three reactor types: Kiwi (1955 to 1964), Phoebus (1964 to 1969), and Pewee (1969 to 1972). Kiwi and Phoebus were large reactors, while Pewee
6298-849: The Pajarito Site. Fuel and internal engine components were fabricated in the Sigma complex at Los Alamos. Testing of fuel elements and other materials science was done by the LASL N Division at TA-46 using various ovens and later a custom test reactor, the Nuclear Furnace. Staff from the LASL Test (J) and Chemical Metallurgy Baker (CMB) divisions also participated in Project Rover. Two reactors were built for each engine; one for zero power critical experiments at Los Alamos and another used for full-power testing. The reactors were tested at very low power before being shipped to
6432-412: The Pewee was also built. It was fired several times at 500 MW to test coatings made of zirconium carbide (instead of niobium carbide ) but Pewee also increased the power density of the system. A water-cooled system is known as NF-1 (for Nuclear Furnace ) used Pewee 2's fuel elements for future materials testing, showing a factor of 3 reductions in fuel corrosion still further. Pewee 2 was never tested on
6566-504: The SNAP project officer in the disbanded Aircraft Nuclear Propulsion Office (ANPO), became chief of the SNAP Branch in the new division. On 25 May 1961, President John F. Kennedy addressed a joint session of Congress . "First," he announced, "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to
6700-589: The Shuttle cargo bay. The design provided 73 kN of thrust and operated at a specific impulse of 875 seconds (8.58 kN·s/kg), and it was planned to increase this to 975 seconds, achieving a mass fraction of about 0.74, compared with 0.86 for the Space Shuttle main engine (SSME). A related design that saw some work, but never made it to the prototype stage, was Dumbo. Dumbo was similar to KIWI/NERVA in concept, but used more advanced construction techniques to lower
6834-560: The Soviet Union ended the nuclear test moratorium that had been in place since November 1958, so Kennedy resumed US testing in September. With a second crash program at the Nevada Test site, labor became scarce, and there was a strike. When that ended, the workers had to come to grips with the difficulties of dealing with hydrogen, which could leak through microscopic holes too small to permit
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#17328631333276968-484: The U.S. Rover program intentionally modified a Kiwi reactor (KIWI-TNT) to go prompt critical, resulting in immediate destruction of the reactor pressure vessel, nozzle, and fuel assemblies. Intended to simulate a worst-case scenario of a fall from altitude into the ocean, such as might occur in a booster failure after launch, the resulting release of radiation would have caused fatalities out to 200 m (600 ft) and injuries out to 600 m (2,000 ft). The reactor
7102-495: The US civilian space program. Project Rover became a joint NASA-AEC project. Silverstein appointed Finger from Lewis to oversee the nuclear rocket development. On 29 August 1960, NASA created the Space Nuclear Propulsion Office (SNPO) to oversee the nuclear rocket project. Finger was appointed as its manager, with Milton Klein from AEC as his deputy. A formal "Agreement Between NASA and AEC on Management of Nuclear Rocket Engine Contracts"
7236-591: The US space program to the AEC, but US President Dwight D. Eisenhower responded by creating the National Aeronautics and Space Administration (NASA), which absorbed NACA. Donald A. Quarles , the Deputy Secretary of Defense , met with T. Keith Glennan , the new administrator of NASA, and Hugh Dryden , his deputy on 20 August 1958, the day after they were sworn into office at the White House , and Rover
7370-529: The aim of producing a nuclear upper stage for an intercontinental ballistic missile (ICBM). York created a new division at Livermore, and Bradbury created a new one called N Division at Los Alamos under the leadership of Raemer Schreiber , to pursue it. In March 1956, the Armed Forces Special Weapons Project (AFSWP) recommended allocating $ 100 million ($ 1121 million in 2023) to the nuclear rocket engine project over three years for
7504-567: The assistant director at Livermore was its chairman, and its other members were Norris Bradbury from LASL; Edward Teller and Herbert York from Livermore; Abe Silverstein , the associate director of the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory ; and Allen F. Donovan from Ramo-Wooldridge . After hearing input on various designs, the Mills committee recommended that development proceed, with
7638-461: The backup B1 engine, B1B, despite grave doubts about it based on the results of the B1A test, in order to obtain more data on the performance and behavior of liquid hydrogen. On startup on 1 September 1962, the core shook, but reached 880 MW. Flashes of light around the nozzle indicated that fuel pellets were being ejected; it was later determined that eleven had been. Rather than shut down, the testers rotated
7772-436: The basic concept, A1 and A3, added coatings to the plates to test fuel rod concepts. The KIWI B series was fueled by tiny uranium dioxide (UO 2 ) spheres embedded in a low- boron graphite matrix and coated with niobium carbide . Nineteen holes ran the length of the bundles, through which the liquid hydrogen flowed. On the initial firings, immense heat and vibration cracked the fuel bundles. The graphite materials used in
7906-469: The basis of a 2,700 MW design intended to be the upper stage of an ICBM. By 1957, the Atlas missile project was proceeding well, and with smaller and lighter warheads becoming available, the need for a nuclear upper stage had all but disappeared. On 2 October 1957, the AEC proposed cutting Project Rover's budget, but the proposal was soon overtaken by events. Two days later, the Soviet Union launched Sputnik 1 ,
8040-457: The best neutron moderator , but assumed an operating temperature of 3,150 °C (5,700 °F), which was beyond the capabilities of available materials. The conclusion was that nuclear-powered rockets were not yet practical. The public revelation of atomic energy at the end of the war generated a great deal of speculation, and in the United Kingdom, Val Cleaver , the chief engineer of
8174-479: The convention, Anderson added support for nuclear rockets to the Democratic Party platform. The third and final test of the Kiwi A series was conducted on 19 October 1960. The Kiwi A3 engine used 27-inch (69 cm) long cylindrical fuel elements in niobium carbide liners. The test plan called for the engine to be run at 50 MW (half power) for 106 seconds, and then at 92 MW for 250 seconds. The 50 MW power level
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#17328631333278308-633: The cost cutting that prevailed as the Vietnam War escalated and after the space race ended with the Apollo 11 Moon landing. Projects Rover and NERVA were canceled over their objection in January 1973, and none of the reactors ever flew. During World War II , some scientists at the Manhattan Project 's Los Alamos Laboratory , including Stan Ulam , Frederick Reines and Frederic de Hoffmann , speculated about
8442-652: The development of nuclear-powered rockets, and in 1947, Ulam and Cornelius Joseph "C. J." Everett wrote a paper in which they considered using atomic bombs as a means of rocket propulsion. This became the basis for Project Orion . In December 1945, Theodore von Karman and Hsue-Shen Tsien wrote a report for the United States Army Air Forces . While they agreed that it was not yet practical, Tsien speculated that nuclear-powered rockets might one day be powerful enough to launch satellites into orbit. In 1947, North American Aviation's Aerophysics Laboratory published
8576-407: The drums to compensate, and were able to continue running at full power for a few minutes before a sensor blew and started a fire, and the engine was shut down. Most but not all of the test objectives were met. The next test of the series was of Kiwi B4A on 30 November 1962. A flame flash was observed when the reactor reached 120 MW. Power was increased to 210 MW, and held there for 37 seconds. Power
8710-416: The drums. To increase thrust, it is sufficient to increase the flow of propellant. Hydrogen, whether in pure form or in a compound like ammonia, is an efficient nuclear moderator, and increasing the flow also increases the rate of reactions in the core. This increased reaction rate offsets the cooling provided by the hydrogen. As the hydrogen heats up, it expands, so there is less in the core to remove heat, and
8844-572: The earth." He then went on to say: "Secondly, an additional 23 million dollars, together with 7 million dollars already available, will accelerate development of the Rover nuclear rocket. This gives promise of someday providing a means for even more exciting and ambitious exploration of space, perhaps beyond the Moon, perhaps to the very end of the Solar System itself." Nuclear reactors for Project Rover were built at LASL Technical Area 18 (TA-18), also known as
8978-487: The effect was negligible: 3, 12 and 24 cents respectively. The tests demonstrated that adjacent nuclear rocket engines would not interfere with each other, and could therefore be clustered, just as chemical ones often were. The next step in LASL's research program was to build a larger reactor. The size of the core determines how much hydrogen, which is necessary for cooling, can be pushed through it; and how much uranium fuel can be loaded into it. In 1960, LASL began planning
9112-439: The electronic instrumentation from radiation from the reactor. The control room was located 3.2 kilometers (2 mi) away. The plastic coating on the control cables was chewed by burrowing rodents and had to be replaced. The reactor was test-fired with its exhaust plume in the air so that any radioactive fission products picked up from the core could be safely dispersed. The reactor maintenance and disassembly building (R-MAD)
9246-435: The energy of the relativistic neutrons allows for a dramatic increase in performance. To do this, pulsed reactors operate in a series of brief pulses rather than the continual chain reaction of a conventional reactor. The reactor is normally off, allowing it to cool. It is then turned on, along with the cooling system or fuel flow, operating at a very high power level. At this level the core rapidly begins to heat up, so once
9380-571: The engine remained stable and controllable throughout. The tests demonstrated that a nuclear rocket engine would be rugged and reliable in space. Kennedy visited Los Alamos on 7 December 1962 for a briefing on Project Rover. It was the first time a US president had visited a nuclear weapons laboratory. He brought with him a large entourage that included Lyndon Johnson , McGeorge Bundy , Jerome Wiesner , Harold Brown , Donald Hornig , Glenn Seaborg , Robert Seamans, Harold Finger and Clinton Anderson. The next day, they flew to Jackass Flats, making Kennedy
9514-495: The first artificial satellite. This fired fears and imaginations around the world and demonstrated that the Soviet Union had the capability to deliver nuclear weapons over intercontinental distances, and undermined American notions of military, economic and technological superiority. This precipitated the Sputnik crisis , and triggered the Space Race , a new area of competition in the Cold War . Anderson wanted to give responsibility for
9648-426: The fuel and cladding. Although less efficient than the open-cycle design, the closed-cycle design is expected to deliver a specific impulse of about 1500 to 2000 seconds (15 to 20 kN·s/kg). The Soviet RD-0410 went through a series of tests at the nuclear test site near Semipalatinsk Test Site . In October 2018, Russia's Keldysh Research Center confirmed a successful ground test of waste heat radiators for
9782-460: The hydrogen propellant. Bussard's study had little impact at first, mainly because only 29 copies were printed, and it was classified as Restricted Data and therefore could only be read by someone with the required security clearance. In December 1953, it was published in Oak Ridge's Journal of Reactor Science and Technology . While still classified, this gave it a wider circulation. Darol Froman ,
9916-416: The large tanks necessary for liquid hydrogen storage, this means that solid core nuclear thermal engines are best suited for use in orbit outside Earth's gravity well , not to mention avoiding the radioactive contamination that would result from atmospheric use (if an "open-cycle" design was used, as opposed to a lower-performance "closed cycle" design where no radioactive material was allowed to escape with
10050-501: The last technology development reactor required to proceed to flight prototypes. Several other solid-core engines have also been studied to some degree. The Small Nuclear Rocket Engine, or SNRE, was designed at the Los Alamos National Laboratory (LANL) for upper stage use, both on uncrewed launchers and the Space Shuttle . It featured a split-nozzle that could be rotated to the side, allowing it to take up less room in
10184-399: The next highest cross section across all known isotopes. The Am is fissile (because it has an odd number of neutrons ) and has a low critical mass , comparable to that of Pu . It has a very high cross section for fission, and if in a nuclear reactor is destroyed relatively quickly. Another report claims that Am can sustain a chain reaction even as a thin film, and could be used for
10318-426: The nuclear rocket was consolidated at Los Alamos, where it was given the codename Project Rover; Livermore was assigned responsibility for development of the nuclear ramjet , which was codenamed Project Pluto . Project Rover was directed by an active duty USAF officer on secondment to the AEC, Lieutenant Colonel Harold R. Schmidt. He was answerable to another seconded USAF officer, Colonel Jack L. Armstrong, who
10452-574: The only coolant available is the working fluid/propellant. A nuclear solid core engine is the simplest design to construct and is the concept used on all tested NTRs. Using hydrogen as a propellant, a solid core design would typically deliver specific impulses (I sp ) on the order of 850 to 1000 seconds, which is about twice that of liquid hydrogen - oxygen designs such as the Space Shuttle main engine . Other propellants have also been proposed, such as ammonia, water, or LOX , but these propellants would provide reduced exhaust velocity and performance at
10586-491: The only president to ever visit a nuclear test site. Project Rover had received $ 187 million in 1962, and AEC and NASA were asking for another $ 360 million in 1963. Kennedy drew attention to his administration's budgetary difficulties, and his officials and advisors debated the future of Project Rover and the space program in general. Finger assembled a team of vibration specialists from other NASA centers, and along with staff from LASL, Aerojet and Westinghouse, conducted
10720-421: The other, and the energy level adjusted by rotating the drums. Because hydrogen also acts as a moderator, increasing the flow of propellant also increased reactor power without the need to adjust the drums. Project Rover tests demonstrated that nuclear rocket engines could be shut down and restarted many times without difficulty, and could be clustered if more thrust was desired. Their specific impulse (efficiency)
10854-512: The outside, but this would expose the reactor pressure vessel to the maximum operating temperature while adding mass, complexity, and moving parts. An alternative liquid-core design is the nuclear salt-water rocket . In this design, water is the working fluid and also serves as the neutron moderator . Nuclear fuel is not retained, which drastically simplifies the design. However, the rocket would discharge massive quantities of extremely radioactive waste and could only be safely operated well outside
10988-693: The particles were made larger (50 to 150 micrometers (0.0020 to 0.0059 in) in diameter), and given a protective coating of pyrolytic graphite. On 10 September, Kiwi B4E was restarted, and run at 882 MW for two and a half minutes, demonstrating the ability of a nuclear rocket engine to be shut down and restarted. In September 1964, tests were conducted with a Kiwi B4 engine and PARKA, a Kiwi reactor used for testing at Los Alamos. The two reactors were run 4.9 meters (16 ft), 2.7 meters (9 ft) and 1.8 meters (6 ft) apart, and measurements taken of reactivity. These tests showed that neutrons produced by one reactor did indeed cause fissions in another, but that
11122-509: The passage of other fluids. On 7 November 1961, a minor accident caused a violent hydrogen release. The complex finally became operational in 1964. SNPO envisaged the construction of a 20,000 MW nuclear rocket engine, so construction supervisor, Keith Boyer had the Chicago Bridge & Iron Company construct two gigantic 1,900,000-liter (500,000 U.S. gal) cryogenic storage dewars . An engine maintenance and disassembly building (E-MAD)
11256-528: The primary focus on improving the technology of hydrogen-cooled reactors. Between 1959 and 1964, a total of eight reactors were built and tested. Kiwi was considered to have served as a proof of concept for nuclear rocket engines. The first test of the Kiwi A, the first model of the Kiwi rocket engine, was conducted at Jackass Flats on 1 July 1959. Kiwi A had a cylindrical core 132.7 centimeters (50 in) high and 83.8 centimeters (30 in) in diameter. A central island contained heavy water that acted both as
11390-547: The program will focus on the design, development, fabrication, and assembly of a nuclear thermal rocket engine. In July 2023, Lockheed Martin was awarded the contract to build the spacecraft and BWX Technologies ( BWXT ) will develop the nuclear reactor. A launch is expected in 2027. Nuclear-powered thermal rockets are more effective than chemical thermal rockets, primarily because they can use low-molecular-mass propellants such as hydrogen. As thermal rockets, nuclear thermal rockets work almost exactly like chemical rockets :
11524-490: The pulsed mode but could vary their duty cycle depending on the need. For instance, during a high-thrust phase of flight, like exiting a low earth orbit , the engine could operate continually and provide an Isp similar to that of traditional solid-core design. But during a long-duration cruise, the engine would switch to pulsed mode to make better use of its fuel. Liquid core nuclear engines are fueled by compounds of fissionable elements in liquid phase . A liquid-core engine
11658-462: The reactor could be controlled. Finger went ahead and called for bids from industry for the development of NASA's Nuclear Engine for Rocket Vehicle Application ( NERVA ) based upon the Kiwi engine design. Rover henceforth became part of NERVA; while Rover dealt with the research into nuclear rocket reactor design, NERVA involved the development and deployment of nuclear rocket engines, and the planning of space missions. LASL's original objective had been
11792-423: The reactor was automatically started and briefly run at full power (990 MW) with no vibration problems. The test had to be terminated after 64 seconds when nozzle tubes ruptured and caused a hydrogen leak around the nozzle that started a fire. Cooldown was performed with both hydrogen and 3,266 kilograms (7,200 lb) of nitrogen gas. On inspection after the test, no damaged fuel elements were found. The final test
11926-567: The reactor's construction were resistant to high temperatures but eroded under the stream of superheated hydrogen, a reducing agent . The fuel species was later switched to uranium carbide , with the last engine run in 1964. The fuel bundle erosion and cracking problems were improved but never completely solved, despite promising materials work at the Argonne National Laboratory . NERVA NRX (Nuclear Rocket Experimental), started testing in September 1964. The final engine in this series
12060-697: The rocket division at De Havilland , and Leslie Shepard , a nuclear physicist at the University of Cambridge , independently considered the problem of nuclear rocket propulsion. They became collaborators, and in a series of papers published in the Journal of the British Interplanetary Society in 1948 and 1949, they outlined the design of a nuclear-powered rocket with a solid-core graphite heat exchanger . They reluctantly concluded that nuclear rockets were essential for deep space exploration, but not yet technically feasible. In 1953, Robert W. Bussard ,
12194-422: The rocket propellant. ) One way to increase the working temperature of the reactor is to change the nuclear fuel elements. This is the basis of the particle-bed reactor, which is fueled by several (typically spherical) elements that "float" inside the hydrogen working fluid. Spinning the entire engine could prevent the fuel element from being ejected out the nozzle. This design is thought to be capable of increasing
12328-399: The seven holes in the graphite modules to create 137-centimeter (54 in) long fuel modules. This time the reactor attained 88 MW for 307 seconds, with an average core exit gas temperature of 2,178 K. The test was marred by three core module failures, but the majority suffered little or no damage. The test was observed by Anderson and delegates to the 1960 Democratic National Convention . At
12462-414: The shed and injured several workers; many suffered ruptured eardrums, and one fractured a heel bone. The reactor was undamaged, but there was extensive damage to the test car and the instrumentation, resulting in the test being postponed for a month. A second attempt on 6 December was aborted when it was discovered that many of the diagnostic thermocouples had been installed backward. Finally, on 7 December,
12596-480: The specific impulse to about 1000 seconds (9.8 kN·s/kg) at the cost of increased complexity. Such a design could share design elements with a pebble-bed reactor , several of which are currently generating electricity. From 1987 through 1991, the Strategic Defense Initiative (SDI) Office funded Project Timberwind , a non-rotating nuclear thermal rocket based on particle bed technology. The project
12730-681: The square root of the kinetic energy loaded on each unit mass of propellant. The kinetic energy per molecule of propellant is determined by the temperature of the heat source (whether it be a nuclear reactor or a chemical reaction ). At any particular temperature, lightweight propellant molecules carry just as much kinetic energy as heavier propellant molecules and therefore have more kinetic energy per unit mass. This makes low-molecular-mass propellants more effective than high-molecular-mass propellants. Because chemical rockets and nuclear rockets are made from refractory solid materials, they are both limited to operate below 3,000 °C (5,000 °F), by
12864-454: The stand and became the basis for current NTR designs being researched at NASA 's Glenn Research Center and Marshall Space flight Center. The NERVA/Rover project was eventually canceled in 1972 with the general wind-down of NASA in the post- Apollo era. Without a human mission to Mars , the need for a nuclear thermal rocket is unclear. Another problem would be public concerns about safety and radioactive contamination . In January 1965,
12998-477: The state of the art of nuclear reactors. Most importantly, the paper surveyed several ranges and payload sizes; Consolidated's pessimistic conclusions had partly been the result of considering only a narrow range of possibilities. The result, Nuclear Energy for Rocket Propulsion , stated that the use of nuclear propulsion in rockets is not limited by considerations of combustion energy and thus low molecular weight propellants such as pure hydrogen may be used. While
13132-480: The strength characteristics of high-temperature metals. Chemical rockets use the most readily available propellant, which is waste products from the chemical reactions producing their heat energy. Most liquid-fueled chemical rockets use either hydrogen or hydrocarbon combustion, and the propellant is therefore mainly water (molecular mass 18) and carbon dioxide (molecular mass 44). Nuclear thermal rockets using gaseous hydrogen propellant (molecular mass 2) therefore have
13266-466: The temperature will level off. These opposing effects stabilize the reactivity and a nuclear rocket engine is therefore naturally very stable, and the thrust is easily controlled by varying the hydrogen flow without changing the control drums. LASL produced a series of design concepts, each with its own codename: Uncle Tom, Uncle Tung, Bloodhound and Shish. By 1955, it had settled on a 1,500 megawatt (MW) design called Old Black Joe. In 1956, this became
13400-482: The test got under way. It was intended to run the engine at 270 MW for 300 seconds, but the test was scrammed after only 36 seconds at 225 MW because hydrogen fires started to appear. All the thermocouples performed correctly, so a great deal of useful data was obtained. The average hydrogen mass flow during the full power portion of the experiment was 9.1 kilograms per second (20 lb/s). LASL next intended to test Kiwi B2, but structural flaws were found that required
13534-457: The test site. In 1956, the AEC allocated 127,200 hectares (314,000 acres) of an area known as Jackass Flats in Area 25 of the Nevada Test Site for use by Project Rover. Work commenced on test facilities there in mid-1957. All materials and supplies had to be brought in from Las Vegas . Test Cell A consisted of a farm of hydrogen gas bottles and a concrete wall 0.91 meters (3 ft) thick to protect
13668-400: The tests conducted from 1955 to 1957, was inexpensive, easy to obtain, liquid at 239 K (−34 °C), and easy to pump and handle. It was, however, much heavier than liquid hydrogen, reducing the engine's impulse ; it was also found to be even more corrosive, and had undesirable neutronic properties. For the fuel, they considered plutonium-239 , uranium-235 and uranium-233 . Plutonium
13802-482: The two laboratories to conduct feasibility studies and construction of test facilities. Eger V. Murphree and Herbert Loper at the Atomic Energy Commission (AEC) were more cautious. The Atlas missile program was proceeding well, and if successful would have sufficient range to hit targets in most of the Soviet Union . At the same time, nuclear warheads were becoming smaller, lighter and more powerful. The case for
13936-420: The type of reactor, ranging from a relatively simple solid reactor up to the much more difficult to construct but theoretically more efficient gas core reactor. As with all thermal rocket designs, the specific impulse produced is proportional to the square root of the temperature to which the working fluid (reaction mass) is heated. To extract maximum efficiency, the temperature must be as high as possible. For
14070-405: The weight of the reactor. The Dumbo reactor consisted of several large barrel-like tubes, which were in turn constructed of stacked plates of corrugated material. The corrugations were lined up so that the resulting stack had channels running from the inside to the outside. Some of these channels were filled with uranium fuel, others with a moderator, and some were left open as a gas channel. Hydrogen
14204-405: Was achieved with a propellant flow of 2.36 kilograms per second (5.2 lb/s), but exit gas temperature was 1,861 K, which was over 300 K higher than expected. After 159 seconds, the power was increased to 90 MW. To stabilize the exit gas temperature at 2,173 K, the fuel rate was increased to 3.81 kilograms per second (8.4 lb/s). It was later discovered that the neutronic power measuring system
14338-574: Was added. It was larger than a football field, with thick concrete walls and shield bays where engines could be assembled and disassembled. There was also an engine test stand (ETS-1); two more were planned. There was also a radioactive material storage facility (RMSF). This was a 8.5 hectares (21 acres) site roughly equidistant from the E-MAD, Test Cell "C", and ETS-1. It was enclosed by a cyclone wire fence with quartz perimeter lighting. The single-track railroad that connected facilities carried one branch through
14472-468: Was also in charge of Pluto and the Systems for Nuclear Auxiliary Power (SNAP) projects. In principle, the design of a nuclear thermal rocket engine is quite simple: a turbopump would force hydrogen through a nuclear reactor, where it would be heated by the reactor to very high temperatures and then exhausted through a rocket nozzle to produce thrust. Complicating factors were immediately apparent. The first
14606-407: Was canceled before testing. In a conventional solid core design, the maximum exhaust temperature of the working mass is that of the reactor, and in practice, lower than that. That temperature represents an energy far below that of the individual neutrons released by the fission reactions. Their energy is spread out through the reactor mass, causing it to thermalize. In power plant designs, the core
14740-403: Was chosen as it is cheap, gets stronger at temperatures up to 3,300 K (3,030 °C), and sublimes rather than melts at 3,900 K (3,630 °C). To control the reactor, the core was surrounded by control drums coated with graphite or beryllium (a neutron moderator) on one side and boron (a neutron poison ) on the other. The reactor's power output could be controlled by rotating
14874-553: Was eliminated, the number of coolant holes in each hexagonal fuel element was increased from four to seven, and the graphite reflector was replaced with a 20-centimeter (8 in) thick beryllium one. Although beryllium was more expensive, more difficult to fabricate, and highly toxic, it was also much lighter, resulting in a saving of 1,100 kilograms (2,500 lb). Due to the delay in getting Test Cell C ready, some features intended for Kiwi C were also incorporated in Kiwi B2. These included
15008-422: Was in most respects a typical hot cell used by the nuclear industry, with thick concrete walls, lead glass viewing windows, and remote manipulation arms. It was exceptional only for its size: 76 meters (250 ft) long, 43 meters (140 ft) and 19 meters (63 ft) high. This allowed the engine to be moved in and out on a railroad car. The "Jackass and Western Railroad", as it was light-heartedly described,
15142-420: Was incorrectly calibrated, and the engine was actually run at an average of 112.5 MW for 259 seconds, well above its design capacity. Despite this, the core suffered less damage than in the Kiwi A Prime test. Kiwi A was considered a success as a proof of concept for nuclear rocket engines. It demonstrated that hydrogen could be heated in a nuclear reactor to the temperatures required for space propulsion, and that
15276-480: Was intended to lead to the entry of nuclear thermal rocket engines into space exploration. Unlike the AEC work, which was intended to study the reactor design itself, NERVA's goal was to produce a real engine that could be deployed on space missions. The 334 kN (75,000 lb f ) thrust baseline NERVA design was based on the KIWI B4 series. Tested engines included Kiwi, Phoebus, NRX/EST, NRX/XE, Pewee, Pewee 2, and
15410-602: Was judged sufficient for space missions by SNPO. Building on the KIWI series, the Phoebus series were much larger reactors. The first 1A test in June 1965 ran for over 10 minutes at 1090 MW and an exhaust temperature of 2370 K. The B run in February 1967 improved this to 1500 MW for 30 minutes. The final 2A test in June 1968 ran for over 12 minutes at 4000 MW, at the time the most powerful nuclear reactor ever built. A smaller version of KIWI,
15544-524: Was managed by the Space Nuclear Propulsion Office (SNPO), a joint agency of the Atomic Energy Commission (AEC), and NASA . Project Rover became part of NASA's Nuclear Engine for Rocket Vehicle Application ( NERVA ) project and henceforth dealt with the research into nuclear rocket reactor design, while NERVA involved the overall development and deployment of nuclear rocket engines, and the planning for space missions. Nuclear reactors for Project Rover were built at LASL Technical Area 18 (TA-18), also known as
15678-413: Was much smaller, conforming to the smaller budget available after 1968. The reactors were fueled by highly enriched uranium , with liquid hydrogen used as both a rocket propellant and reactor coolant. Nuclear graphite and beryllium were used as neutron moderators and neutron reflectors . The engines were controlled by drums with graphite or beryllium on one side and boron (a nuclear poison ) on
15812-418: Was not readily available. Highly enriched uranium was therefore chosen. For structural materials in the reactor, the choice came down to graphite or metals. Of the metals, tungsten emerged as the frontrunner, but it was expensive, hard to fabricate, and had undesirable neutronic properties. To get around its neutronic properties, it was proposed to use tungsten-184 , which does not absorb neutrons. Graphite
15946-569: Was positioned on a railroad car in the Jackass Flats area of the Nevada Test Site . As of January 2012, the propulsion group for Project Icarus was studying an NTR propulsion system, but has seen little activity since 2019. In 1987, Ronen & Leibson published a study on applications of Am (one of the isotopes of americium ) as nuclear fuel to space nuclear reactors , noting its extremely high thermal cross section and energy density . Nuclear systems powered by Am require less fuel by
16080-402: Was pumped into the middle of the tube and would be heated by the fuel as it traveled through the channels as it worked its way to the outside. The resulting system was lighter than a conventional design for any particular amount of fuel. Between 1987 and 1991, an advanced engine design was studied under Project Timberwind , under the Strategic Defense Initiative , which was later expanded into
16214-437: Was rejected because while it forms compounds easily, they could not reach temperatures as high as those of uranium. Uranium-233 was seriously considered, as compared to uranium-235 it is slightly lighter, has a higher number of neutrons per fission event, and a high probability of fission. It therefore held the prospect of saving some weight in fuel, but its radioactive properties make it more difficult to handle, and in any case it
16348-479: Was reported by the Karlsruhe Institute of Technology 2008 study. In 2000, Carlo Rubbia at CERN further extended the work by Ronen and Chapline on a Fission-fragment rocket using Am as a fuel. Project 242 based on Rubbia design studied a concept of Am based Thin-Film Fission Fragment Heated NTR by using a direct conversion of the kinetic energy of fission fragments into increasing of enthalpy of
16482-457: Was roughly double that of chemical rockets. The nuclear rocket enjoyed strong political support from the influential chairman of the United States Congress Joint Committee on Atomic Energy , Senator Clinton P. Anderson from New Mexico (where LASL was located), and his allies, Senators Howard Cannon from Nevada and Margaret Chase Smith from Maine . This enabled it to survive multiple cancellation attempts that became ever more serious in
16616-488: Was said to be the world's shortest and slowest railroad. There were two locomotives: the electric L-1, which was remotely controlled, and the diesel-electric L-2, which was manually controlled, with radiation shielding around the cab . Test Cell C was supposed to be completed in 1960, but NASA and AEC did not request funds for additional construction that year; Anderson provided them anyway. Then there were construction delays, forcing him to personally intervene. In August 1961,
16750-699: Was signed by NASA Deputy Administrator Robert Seamans and AEC General Manager Alvin Luedecke on 1 February 1961. This was followed by an "Inter-Agency Agreement on the Program for the Development of Space Nuclear Rocket Propulsion (Project Rover)", which they signed on 28 July 1961. SNPO also assumed responsibility for SNAP, with Armstrong becoming assistant to the director of the Reactor Development Division at AEC, and Lieutenant Colonel G. M. Anderson, formerly
16884-512: Was that a means had to be found of controlling reactor temperature and power output. The second was that a means had to be devised to hold the propellant. The only practical way to store hydrogen was in liquid form, and this required a temperature below 20 K (−253.2 °C). The third was that the hydrogen would be heated to a temperature of around 2,500 K (2,230 °C), and materials would be required that could withstand such temperatures and resist corrosion by hydrogen. Liquid hydrogen
17018-451: Was the Kiwi B4E test on 28 August in which the reactor was operated for twelve minutes, eight of which were at full power (937 MW). This was the first test to use uranium carbide pellets instead of uranium oxide, with a 0.0508-millimeter (0.002 in) niobium carbide coating. These were found to oxidize on heating, causing a loss of carbon in the form of carbon monoxide gas. To minimize this,
17152-628: Was the XE, designed with flight representative hardware and fired into a low-pressure chamber to simulate a vacuum. SNPO fired NERVA NRX/XE twenty-eight times in March 1968. The series all generated 1100 MW, and many of the tests concluded only when the test-stand ran out of hydrogen propellant. NERVA NRX/XE produced the baseline 334 kN (75,000 lb f ) thrust that Marshall Space Flight Center required in Mars mission plans. The last NRX firing lost 17 kg (38 lb) of nuclear fuel in 2 hours of testing, which
17286-412: Was the first item on the agenda. Quarles was eager to transfer Rover to NASA, as the project no longer had a military purpose. Silverstein, whom Glennan had brought to Washington, D.C., to organize NASA's spaceflight program, had long had an interest in nuclear rocket technology. He was the first senior NACA official to show interest in rocket research, had initiated investigation into the use of hydrogen as
17420-480: Was then continued through the NASA's NERVA program (1961–1973). NERVA achieved many successes and improved upon the early prototypes to create powerful engines that were several times more efficient than chemical counterparts. However, the program was cancelled in 1973 due to budget constraints. To date no nuclear thermal propulsion system has ever been implemented in space. A nuclear thermal rocket can be categorized by
17554-460: Was then increased to 450 MW, but flashes then became frequent, and the engine was shut down after 13 seconds. After the test it was discovered that 97% of the fuel elements were broken. The difficulties of using liquid hydrogen were appreciated, and the cause of the vibration and failures was diagnosed as hydrogen leaking into the gap between the core and the pressure vessel. Unlike a chemical engine that would likely have blown up after suffering damage,
17688-506: Was theoretically the best possible propellant, but in the early 1950s it was expensive, and available only in small quantities. In 1952, the AEC and the National Bureau of Standards had opened a plant near Boulder, Colorado , to produce liquid hydrogen for the thermonuclear weapons program. Before settling on liquid hydrogen, LASL considered other propellants such as methane ( CH 4 ) and ammonia ( NH 3 ). Ammonia, used in
17822-602: Was used as a propellant, at a flow rate of 3.2 kilograms per second (7.1 lb/s). Intended to produce 100 MW, the engine ran at 70 MW for 5 minutes. The core temperature was much higher than expected, up to 2,900 K (2,630 °C), due to cracking of the graphite plates, which was enough to cause some of the fuel to melt. A series of improvements were made for the next test on 8 July 1960 to create an engine known as Kiwi A Prime. The fuel elements were extruded into cylinders and coated with niobium carbide ( NbC ) to resist corrosion. Six were stacked end-to-end and then placed in
17956-405: Was used in studies of Nova , and became the goal of Project Rover. LASL planned to conduct two tests with Kiwi B, an intermediate 1,000 MW design, in 1961 and 1962, followed by two tests of Kiwi C, a prototype engine, in 1963, and have a reactor in-flight test (RIFT) of a production engine in 1964. For Kiwi B, LASL made several design changes to get the required higher performance. The central core
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