Boeing patents laser-powered fusion-fission jet engine for airplanes, spacecraft
Assume the brace position. Boeing has received a patent for, I kid you not, a laser-powered fusion-fission jet propulsion system. Boeing envisions that this system could replace both rocket and turbofan engines, powering everything from spacecraft to missiles to airplanes.
The patent, US 9,068,562, combines inertial confinement fusion, fission, and a turbine that generates electricity. It sounds completely crazy—and it is completely unrealistic given our current mastery of fusion, or lack thereof—but, in the future perhaps, this could be a rather ingenious solution.
To begin with, imagine the silhouette of a big turbofan engine, like you'd see on a commercial jetliner. Somewhere in the middle of the engine there is a fusion chamber, with a number of very strong lasers focused on a single point. A hohlraum (pellet) containing a mix of deuterium and tritium (hydrogen isotopes) is placed at this focal point. The lasers are all turned on at the same instant, creating massive pressure on the pellet, which implodes and causes the hydrogen atoms to fuse. (This is called inertial confinement fusion, as opposed to the magnetic confinement fusion that is carried out in a tokamak.)
According to the patent, the hot gases produced by the fusion are pushed out of a nozzle at the back of the engine, creating thrust. But that's not all! One of the by-products of hydrogen fusion is lots of fast neutrons. In Boeing's patented design, there is a shield around the fusion chamber that's coated with a fissionable material (uranium-238 is one example given). The neutrons hit the fissionable material, causing a fission reaction that generates lots of heat.
http://arstechnica.co.uk/cars/2015/07/boeing-patents-laser-powered-fusion-fission-jet-engine-for-airplanes-spacecraft/
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