Unlike other ramjets, scramjets do not need to slow air to subsonic speeds in their combustion chambers. To pull off ignition and expansion in the 0.001 seconds before the pressurized air shoots out the exhaust, scramjets typically use hydrogen fuel, which has a high specific impulse (change ...
Ramjets tend to be used on rocket and missile engines but since they "breathe" air, they cannot be used in space. Scramjets are similar, except that the supersonic air doesn't slow down anything like as much as it speeds through the engine. By remaining supersonic, the air exits at ...