Intake design was also a major issue. As much of the available energy in the incoming air has to be recovered, known as intake recovery, using shock waves in the supersonic compression process in the intake. At supersonic speeds the intake has to make sure that the air slows down without excessive pressure loss. It has to use the correct type of shock waves, oblique/plane, for the aircraft design speed to compress and slow the air to subsonic speed before it reaches the engine. The shock waves are positioned using a ramp or cone which may need to be adjustable depending on trade-offs between complexity and the required aircraft performance.