Ramjet

The maximum thrust of a gas turbine engine is limited by the maximum turbine inlet temperature. At supersonic speeds the pressure and temperature rise are such that the turbine is not very useful. Also, above M = 3, the pressure rise makes the compressor unnecessary. The Ramjet engine is a jet engine without the compressor or a turbine. The forward speed is sufficient to provide air intake at high pressures required to generate exhaust velocities that deliver thrust.

Ramjets operate at M=3. Therefore the ramjet requires additional propulsive device to enable it to reach M = 3.

The Scramjet is a supersonic combustion Ramjet.

Scramjet