ASME GTTC 10-18-21 Bi-Monthly Technical Meeting
Harold Simmons/SW Research Institute
"Design a Mach 3+ Jet Engine with a Slide Rule"
Powered by two Pratt & Whitney J58 jet Engines, the Lockheed SR-71 Blackbird broke the world's record for sustained altitude in horizontal flight at 85,069 feet and absolute speed record of 2,193.2 MPH, Mach 3.3 in 1976. As it retired, in 1990, one SR-71 set a transcontinental a speed record from LA to DC (2299.7 statute miles in 1 hour, 4 minutes, and 20 seconds), averaging 2,124 MPH. These records still stand today! The 34,000 lb. thrust J58 Engine transitions from pure turbojet to part ramjet as it climbs to 90,000 ft. Its 9-stage compressor only provided 8.5:1 pressure ratio, but traveling at Mach 3.3, ram air compression ratio reached 39:1 creating inlet pressure similar to 10,000 ft, but with temperatures up to 750 degrees F. Design challenges were pervasive, especially for oil lubricated bearings, material selection, and thermal growth. As computing power was severely limited in those days; J58 design challenges were overcome with creative hand draw designs, rigorous review protocols, and experience-based analyses using slide rules and adding machines. Harold will review some of the 1960’s methods used to design record shattering jet engines with nothing more than a knowledge of mechanical engineering, a culture of looking outside the box, and a slide rule.