Why can't jets use a rocket engine like Raptor?

The people living near airports don't want things flying faster than the speed of sound near them.

Use to much fuel for airplanes to carry.

Jets fly in the atmosphere, and they use air to burn fuel. Rockets fly outside the atmosphere, so they have to carry oxidizer with them. Rocket planes have existed, but because the have to carry both elements to function, they're limited in how much payload they can carry and how far they can go.

Airplanes can use rocket engines! In fact, they were one of the first practical products from a fledgling propulsion laboratory in Southern California. https://en.m.wikipedia.org/wiki/JATO https://m.youtube.com/watch?v=MtU66pRzfIk

There is an air breathing rocket engine that's exactly what you want on a plane:

https://en.m.wikipedia.org/wiki/SABRE_%28rocket_engine%29

https://www.gov.uk/government/publications/synergetic-air-br...

The answer is "its too expensive, unsafe and basically unnecessary." Even Concorde (with conventional jets) proved to be uneconomical when luxury commercial aviation was lucrative, and US rocket powered X-Planes never made it out of prototypes.

Giant turbofans are good enough.

Quick and easy answer: A rocket wouldn't last long enough. A jet can fly for hours.

Read up on the German rocket fighters used in WW2. IIRC the rocket engine lasted about six minutes. They had no power available for landing, so had to glide to a close-by landing strip or crash.

Fast, they were. Useful, not so much. Dangerous to their pilots, also.

https://en.wikipedia.org/wiki/Messerschmitt_Me_163_Komet

One way to look at it is to use the particular fuel and engines ISP. Specific impulse which really is about pounds of thrust per pound of fuel per second.

Rocket each pound of fuel + oxidizer you burn a second gives produces a few hundred pounds of thrust. Call it 300.

Air breathing engine doesn't carry oxidizer. A rocket needs to carry ~3 lbs of oxidizer per lb of fuel. Using the 300 number above an air breathing engine would have an ISP of 900.

It gets worse of the rocket because prop and turbo-fan engines also use air for reaction mass[1]. Which boosts the calculated ISP even higher. Call it 5X higher. Now your ISP is 4500.

So yes you can use rockets for an aircraft. But it won't travel as far as one with a piston or turbofan.

1 Thrust is basically mass flow X deltaV. Where power is mass flow X deltaV squared. So it's more efficient to create thrust by accelerating a large mass flow a small amount (turbofans) than a a small amount of mass a large amount (rockets).