All engines work on the same concept. Convert the heat released by a chemical reaction into thrust. The chemical reaction has a fuel, and an oxidizer to burn it. This reaction releases hot gases at high pressures, which are then exited through a nozzle to generate thrust.
All engines carry their own fuel with them in a separate tank. Those that also carry their own oxidizer are called rocket engines, while the those which suck in oxygen from the surrounding air are called air breathing engines.
Rocket Engines
Rocket Engines always contain
- Solid Rocket Motor In SRM’s, the fuel + oxidizer mixture exists as a solid mass. You can start burning the solid mass at one end all the way to the other. As a result, SRM are essentially a steel tube with solid propellant inside it, and a hole/nozzle at one end, to let the hot combustion gases out and generate thrust. There are hundreds of solid propellants combos out there, which I leave to the reader to google and find out. Due to their versitility and easy of long term storage, SRM’s are the workhorse engines for missiles.
- Cryogenic In you want to get a lot of kick out of your engine, you have to go for liquid propellants. The best liquid propellants are gaseous at room temperate ad pressure, hence they tanks to contain them would have to as big as a city block to store meanful amounts. Hence, they are first liquidified at cryogenic temperatures (-200 degree C) and then stored. This also makes long term storage difficult and hence these type of engines are limited to orbitital launches only. The best example is liquid methane (fuel) + liquid oxygen (oxidizer)
- Hypergolics In terms of kick, they sit somwhere between SRM’s and cryogenics. These are liquids at room temperature and pressure, but they tend to be corrosive and toxic in nature. As a result, long term storage is hard, and due to safetly issues, people prefer to use them for engines that will be used in space, ad not for reaching space. Example - Aniline (fuel) + hihgly concentrated nitric acid (oxidizer). Fun note: concentrated nitric acid
Air Breathing Engines
When a airbreating engines uses a “compressor/pump” to help it suck air from surrounding’s it’s a gas-turbine engine. When the forward momentum of the aircraft is sufficjent to force air into the engine, they are called Ram-engines.
- Gas-turbine engines These type of engines suck-in air from surrounding using a compressor, since they need so much air that that a pump is needed to drive all that air.
- Turbo-Jet: In this engine, all the thrust comes from
- Turbofan:
- Turbo-prop:
- Ram engines