Two inventors, working apart, raced to build the first jet engine
Frank Whittle, an RAF officer, started designing a practical jet engine in 1928. In Germany Hans von Ohain was independently chasing the same idea a few years later. Von Ohain's engine flew first, powering the Heinkel He 178 over Rostock on 27 August 1939, though heat damage quickly burned it out.
Rockets had already flown. In 1928 the Lippisch Ente, earlier used as a glider, became the first aircraft powered by rockets, and the Opel RAK.1 of 1929 was the first built for rocket flight. Italy's Caproni Campini N.1 grabbed headlines in 1940, but its compressor was turned by a piston engine rather than by a true gas turbine. Britain's Gloster E.28/39 flew on Whittle's engine in May 1941, and a General Electric version of it powered America's Bell XP-59A the next year.
The Gloster Meteor became the first jet built in series, and Germany's Messerschmitt Me 262 entered service in April 1944 as the first operational jet fighter, though too late to change the war. Whittle used a centrifugal compressor, while von Ohain's axial-flow layout won out with most manufacturers by the 1950s.
Passenger jets arrived in 1952, when BOAC flew the de Havilland Comet from London to Johannesburg, higher, faster and smoother than propeller planes. Metal fatigue in its aluminium structure caused several crashes, opening the way for the Boeing 707 in 1958. The 707 hung its engines beneath the wings, a layout echoed in airliners ever since. Fuel-thrifty turbofans spread through the 1950s and 1960s and became the commonest jet engine. Supersonic travel came with the Soviet Tu-144 at Mach 2.35 in 1975 and Concorde, which flew for 27 years.
Jets are most efficient when their exhaust leaves only slightly faster than the aircraft is moving, which is why airliners cruise near Mach 0.8 at 10,000 to 15,000 metres. Designers also follow the Whitcomb area rule, smoothing an aircraft's cross-section along its length to limit wasteful shockwaves. The SR-71 Blackbird holds the military speed record at Mach 3.35, while the uncrewed X-43 scramjet reached roughly Mach 9 to 10.
Source: Jet aircraft
