Fusion-Thermal Engine
Engine which uses fusion energy to heat and expel reaction mass for propulsion.
Design
Resembling somewhat a fossil-fueled jet engine, a fusion-thermal engine operates by intaking air, superheating it with radiant energy from a fusion reaction, and expelling it to produce thrust. Unlike a torch drive the fusion plasma is kept contained and hence the exhaust is only negligibly radioactive. However, this indirect heating results in greatly reduced specific impulse and hence while capable of enabling efficient surface-to-orbit flight, a fusion-thermal engine is generally not suitable for interplanetary travel.Use
The most common uses for fusion-thermal engines is in aircraft and spaceplanes, where high energy density and long operating hours are desired. For atmospheric flight, endurance is limited only by mechanical wear and the amount of fusion fuel on board. Spaceplanes can take advantage of dual-mode capability by using air as reaction mass while in atmosphere, followed by a switch to onboard tanks filled with e.g. water or hydrogen to boost into orbit. This versatility combined with the relative safety of fusion-thermal designs versus pure fission alternatives, has led to many types of air- and spacecraft in advanced polities utilizing these engines.History
With the invention of fusion reactors, human civilization gained access to an extremely energy-dense and safe power source. The earliest fusion-powered aircraft were huge, using onboard reactors to power electric motors driving propellers or ducted fans, as materials science had not yet advanced to the point where heat could be absorbed in some sort of exchange medium and transferred to an engine's working fluid. Once this became possible, fusion-thermal engines offered an easy and efficient way to make self-contained surface-to-orbit craft.
Access & Availability
Common form of reaction drive
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