 After the air passes the end of the first ramp it has become subsonic such that the diverging ramp further contributes towards the reduction in airstream velocity and consequently its increase in pressure.This intake design thus ensures excellent pressure recovery and contributes to Concorde's improved fuel efficiency whilst cruising supersonically at up to Mach 2.2 (beyond which airframe heating effects limit any further increase in speed).Variable geometry intakes, such as those on Concorde, vary the ramp angle to focus the series of oblique shock waves onto the intake lip, control of which is accomplished by complex non-linear control laws using the ramp void pressure (the pressure of the air in the gap between the two ramps) as a control input.