 antimatter catalyzed nuclear pulse propulsion is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel which normally would not be useful in propulsion. the anti-protons used to start the reaction are consumed, so it is a misnomer to refer to them as a catalyst. traditional nuclear pulse propulsion has the downside that the minimum size of the engine is defined by the minimum size of the nuclear bombs used to create thrust. with conventional technologies nuclear explosives can scale down to about 1/100 kiloton (10 tons, 42 gj; w54), but making them smaller seems difficult. large nuclear explosive charges require a heavy structure for the spacecraft, and a very large (and heavy) pusher-plate assembly. small nuclear explosives are believed to stop shrinking in overall size and required fissile nuclear materials at around 25 kilograms weight, so smaller pulse units are much more expensive per delivered unit energy, and much less mass efficient than larger ones. by injecting a small amount of antimatter into a subcritical mass of fuel (typically plutonium or uranium) fission of the fuel can be forced. an anti-proton has a negative electric charge just like an electron, and can be captured in a similar way by a positively charged atomic nucleus. the initial configuration, however, is not stable and radiates energy as gamma rays. as a consequence, the anti-proton moves closer and closer to the nucleus until they eventually touch, at which point the anti-proton and a proton are both annihilated. this reaction releases a tremendous amount of energy, of which some is released as gamma rays and some is transferred as kinetic energy to the nucleus, causing it to explode. the resulting shower of neutrons can cause the surrounding fuel to undergo rapid fission or even nuclear fusion. the lower limit of the device size is determined by anti-proton handling issues and fission reaction requirements, unlike either the project orion-type propulsion system, which requires large numbers of nuclear explosive charges, or the various anti-matter drives, which require impossibly expensive amounts of antimatter, antimatter catalyzed nuclear pulse propulsion has intrinsic advantages. a conceptual design of a thermonuclear explosive physics package, is one in which the primary mass of plutonium, usually necessary for the ignition in a conventional teller-ulam thermonuclear explosion, is replaced by one microgram of antihydrogen. in this theoretical design, the antimatter is helium cooled and magnetically levitated in the center of the device, in the form of a pellet a tenth of a mm in diameter, a positio
Fusion_power Nuclear_spacecraft_propulsion