![]() ![]() 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. 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). That, in turn, varies as the square root of the kinetic energy loaded on each unit mass of propellant. The specific impulse (Isp) of the engine is set by the speed of the exhaust stream. ![]() Nuclear-powered thermal rockets are more effective than chemical thermal rockets, primarily because they can use low-molecular-mass propellants such as hydrogen.Īs thermal rockets, nuclear thermal rockets work almost exactly like chemical rockets: 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. In July 2023, Lockheed Martin was awarded the contract to build the spacecraft and BWX Technologies ( BWXT) will develop the nuclear reactor. The next phases of the program will focus on the design, development, fabrication, and assembly of a nuclear thermal rocket engine. 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. In May 2022 DARPA issued an RFP for the next phase of their Demonstration Rocket for Agile Cislunar Operations (DRACO) nuclear thermal engine program. Congress approved US$125 million in development funding for nuclear thermal propulsion rockets. The Direct Fusion Drive project at the Princeton Plasma Physics Laboratory is one such example, although "energy-positive fusion has remained elusive". Whereas all early applications for nuclear thermal rocket propulsion used fission processes, research in the 2010s has moved to fusion approaches. Although more than ten reactors of varying power output have been built and tested, as of 2023, no nuclear thermal rocket has flown. The United States maintained an NTR development program through 1973 when it was shut down for various reasons, for example to focus on Space Shuttle development. ![]() NTRs have been proposed as a spacecraft propulsion technology, with the earliest ground tests occurring in 1955. The external nuclear heat source theoretically allows a higher effective exhaust velocity and is expected to double or triple payload capacity compared to chemical propellants that store energy internally. 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 engine is in the left background with a shield structure in the mid/foreground.Ī nuclear thermal rocket ( NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket. Sketch of a solid core fission nuclear thermal rocket with tap-off turbopump 1 December 1967: The first ground experimental nuclear rocket engine (XE) assembly is shown here in "cold flow" configuration, as it makes a late evening arrival at Engine Test Stand No. JSTOR ( August 2019) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Nuclear thermal rocket" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification. ![]()
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