How does a rocket work? Is it different from a jet engine?
In: Engineering
A jet engine takes the ambient air and compresses it using fan blades, then injects fuel into that compressed air and ignites it, then uses the rapid expansion and expulsion of the hot air to push the aircraft forward.
A rocket engine does NOT take in any ambient air. It uses internally stored oxidizers and fuels, mixes them, combusts them, and uses the rapid ejection of the combustion products to push the rocket forward.
Major difference is obviously that the jet engine does not store its own oxidizer, it grabs it from the air. This is why jet engines cannot function in space, while rocket engines can, because they bring their own supplies.
Both rockets and jets work by throwing mass out the back at high speed in order to push themselves forward.
The difference is where the mass comes from…in a rocket, all the mass is carried onboard (fuel + oxydizer). In a jet, most of the mass is in the atmosphere (air) and the jet just carries the fuel. The oxydizer is oxygen from the air.
The inner mechanics are quite different but they all follow the “suck/squeeze/bang/blow” format for themal engines.
Yes little dude, they are different. The main difference is that a rocket engine has almost no moving parts, it’s just a long controlled explosion in a nicely shaped chamber. A jet engine on the other hand, has hundreds of individual parts moving at very high speed inside.
Rockets take a fuel and an oxidizer, combust them, and send a large amount of gas out the back at very high speed. Fuel can be liquid or solid, but its all about a large amount of gas leaving at very high speed.
Turbojet engines like used in fighter jets have an air intake up front which pulls in a moderate amount of air, compresses it, injects fuel, burns it, and sends the mixture through a turbine to spin the compressor up front, then ejects the gas at pretty high speed.
Turbofans like you see on commercial airliners have the jet turbine in the core like Turbojets do, but they have that turbine in the back also spin a really big fan at the front which takes a large amount of air and speeds it up just a tiny bit. This imparts a large amount of momentum (thrust) to the air while consuming less energy than trying to accelerate it to high speed.
Rockets have incredible power to weight ratios but have to carry their own oxidizers. Turbojets have good power to weight and power to size ratios and only have to bring fuel with them, while turbofans have great fuel efficiency but aren’t compact. If you need maximum thrust for a short while you go for a rocket, if you need high thrust for a long time in a small package then you need a turbojet, and if you need moderate thrust for a really long time and don’t care about space then a turbofan is your engine of choice
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