pressure, static pressure, angle of attack and sideslip) and sent it to the Air Intake Control Units located nearer the air intakes, a distance of ~190 feet, using screened, twisted pair cables to replace a much greater weight in aircraft wiring had only analogue signal wiring and pneumatic piping been used. The intake control system had the unique ability to keep the powerplants operating correctly and to aid recovery, whatever the pilots, the aircraft and the atmosphere were doing in combination at the time. The overall pressure ratio for the powerplant at Mach 2.0 cruise at 51,000 ft was about 82:1, with 7.3:1 from the intake and 11.3:1 from the 2 engine compressors. The thermal efficiency with this high pressure ratio was about 43%. Exhaust nozzle The variable-geometry exhaust nozzle, developed by SNECMA, consisted of two "eyelids" which varied their position in the exhaust flow dependent on the flight regime; for example, when fully-closed (into the exhaust flow), they acted as thrust-reversers, aiding deceleration from landing to taxi speed. In the fully-open cruise position, together with the engine nozzle, they formed an ejector nozzle to control the expansion of the exhaust. The eyelids formed the divergent passage while the engine exhaust ejected or pumped the secondary flow from the intake ramp bleed slot. The expanding flow in the diverging section caused a forward thrust force on the exhaust nozzle: its 29% contribution to the overall propulsion system thrust at cruise. During cruise at Mach 2.02 each Olympus 593 was producing around 10,000 lbf of thrust, equivalent to 36,000 horsepower (~27 MW) per engine. Eames (SAE Transactions 1991) however mentions the cruise thrust of each engine to be 6790 lbf, which corresponds to 25,000 horsepower per engine and 100,000 horsepower for the entire vehicle. The 10,000 lbf is perhaps the maximum thrust available at cruising speed (used during acceleration and climb just before transitioning to cruise). The primary exhaust nozzle and jet pipe were designed for a life of 30,000 hours; the TRA (Thrust Reverser Aft) structure for a life of 40,000 hours. Variants 593 - Original version designed for Concorde Thrust : 20,000 lbf (89 kN) dry / 30,610 lbf (136 kN) Afterburner 593-22R - Powerplant fitted to prototypes. Higher performance than original engine due to changes in aircraft specification. Thrust : 34,650 lbf (154 kN) dry / 37,180 lbf (165 kN) reheat 593-610-14-28 - Final version fitted to production