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Rocketry
Published in Jonathan Allday, Apollo in Perspective, 2019
In the 1960s, NASA carried out development work on nuclear engines. The Nuclear Engines for Rocket Vehicle Applications (NERVA) programme constructed and tested several variants with thrusts between 44,000 and 1,111,000 N. These engines delivered specific impulses of the order of 800 s – much better than a chemical rocket. At the time, the tests were taking place with a manned Mars mission in mind. Consideration was given to using them in a modified Saturn V third stage. However, when the Nixon administration cut the NASA budget, NERVA was a casualty. Despite this, the principle of the nuclear engine was established successfully and over 17 hours of accumulated ground-based test firing experience was achieved. Indeed, one of the engine designs was certified as flight-safe before the programme came to an end and nuclear engines remain valid options for interplanetary exploration. The Russians have also tested nuclear thermal propulsion successfully.
Hydrogen in Aeronautics
Published in G. Daniel Brewer, Hydrogen Aircraft Technology, 2017
Development of a nuclear rocket engine in a flyable configuration was undertaken under the NERVA (nuclear engine rocket vehicle application) phase. Aerojet General Corporation was the prime contractor for the complete engine, with Westinghouse Electric Corporation having the contract for design of the reactor itself.
Numerical Investigation and Parametric Study on Thermal-Hydraulic Characteristics of Particle Bed Reactors for Nuclear Thermal Propulsion
Published in Nuclear Technology, 2020
Yu Ji, ZeGuang Li, Jun Sun, ErSheng You, MingGang Lang, Lei Shi
Nuclear thermal propulsion was first proposed in the early 1950s and was aggressively developed from the late 1950s to the early 1970s. During this period, the principal research activities were performed in the United States and the Union of Soviet Socialist Republics,5 and the most representative effort was the Rover and later the Nuclear Engine Rocket Vehicle Application (NERVA) Project.6 NERVA was a hardware-oriented program that achieved many accomplishments, such as fuel design and fabrication, system design, and the testing of 20 reactors or engines. However, the NERVA program was terminated in 1973 due to recessionary ambitions for space exploration and changed national economic priorities.4 Afterward, some space technologists continued to reconsider the benefits of space nuclear systems, and several different nuclear system concepts for propulsion were conceived and studied. The particle bed reactor (PBR) was one of these novel concepts.4 Similar to other established or planned pebble bed reactors or facilities, such as the HTR-10 (Ref. 7) and the HTR-PM (Ref. 8) in China, the PBMR (Ref. 9) in South Africa, and the SANA experiments facility10 in Germany, the PBR was also a gas-cooled reactor that utilized nuclear fuel particles to pack a bed. The PBR is different, however, as this bed has been transformed into an annular region within two concentric porous frits from a cylindrical region in the common pebble bed reactor and the coolant, mostly the hydrogen, flows through the fuel bed radially rather than axially to reduce the pressure drop,11 as shown in Fig. 1. As a variant of the pebble bed reactor, the operating temperature in the PBR was significantly higher than that of ground pebble bed reactors due to the adoption of fuel and other structural materials with higher melting points. In addition, the power density in the PBR core was also increased because of the reduction in fuel particle size and the subsequent enhancement of its heat removal capability, thus leading to a compact, lightweight, and efficient reactor design. Compared to the NERVA reactor, the PBR fit better to an advanced space nuclear propulsion system. Unfortunately, the development of PBR systems lasted only 7 years, i.e., 1987 to 1994, and the demonstration was never initiated. In recent years, the U.S. National Aeronautics and Space Administration has responsored the NTP research and has chosen it as the primary option for cargo and crew transfer in outer space.12 It is estimated in the Design Reference Architecture 5.0 that the use of clustered, lower-thrust NERVA engines is capable of human exploration missions to Mars at a reduced risk,13 and that the exploration capability could be enhanced further if the PBR systems are realized.