Eli5:how does petrol engines differ from diesel engine?if so then what type of engine is used in rockets?
In: Technology
In a gasoline engine, fuel and air are mixed and injected into the cylinder. The piston compresses them. Then a spark plug creates a spark which ignites the mixture.
In a Diesel engine, air is injected without fuel. The air is compressed to a point where it is so hot that fuel would ignite on its own if it were present. This would mess with timing and such, so the fuel is injected at the end of this compression stage. Because the air inside is so hot, the fuel ignites.
Diesel engines also have something called glowplugs. Because a Diesel engine requires the heat of compression to ignite the fuel, it can be hard to start an engine in the cold. Glowplugs are basically just heating devices to help get over the initial cold when starting.
Rocket motors are reaction engines. They produce thrust essentially by chucking all the burnt stuff out the back, *really* fast. The underlying principle is basically the same though — a fuel and an oxidizer are mixed, ignited (once, unlike intermittent automobile engines, rocket motors are typically continuous), and the reaction products are expanded inside a nozzle, which produces thrust.
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