OBITUARY : Bill Hilton

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Bill Hilton's greatest claim to fame was that he coined the term "the sound barrier", yet he always maintained that this was the result of a misunderstanding by a journalist to whom he tried to explain the complex concept of supersonic travel in the 1930s. This was typical of a man who had a brilliant mind but never showed the least trace of pomposity. His career spanned major changes; he was an aerodynamicist at a time when the science was in its infancy, and was also in at the birth of the space race.

Hilton was born in north London in 1912. He studied physics at the Royal College of Science and aerodynamics for his PhD at Imperial College, London. His postgraduate work was on photographing the vortices around aircraft which cause lift, enabling them to fly. He was the first person to photograph vortices on propellors; this research was used in 1976 in the design of the Westland Berp Helicopter, which still holds the world speed record for helicopters.

He joined the National Physical Laboratory in 1935 and became a Principal Scientific Officer in charge of the two wind tunnels, leading a team looking at the possibilities of supersonic flight. The wind tunnels were used for research on guided missiles, aircraft and ramjets. He was to remain there until the end of the Second World War; and advised on the Mulberry harbours (the prefabricated harbours towed across the Channel by the Allies), the bouncing bomb and the development of the jet engine.

At the end of the war he was seconded by the National Physical Laboratory to the Applied Physics Laboratory of Johns Hopkins University in Maryland, in the United States, where he worked on Project Bumblebee ramjet research into supersonic propulsion for missiles. He returned to the UK in 1949 and worked briefly for the Royal Aircraft Establishment, before joining Armstrong Whitworth as Chief Aerodynamicist in 1950, where he set up his third high-speed wind tunnel. He published a standard reference book, High Speed Aerodynamics (1951).

By the late 1950s his interest was turning to the new field of space, and as the Head of the Astronautics Section of the Advanced Projects Group at Hawker Siddeley in Kingston, Surrey, he led the first industrial team in the UK studying the potential of communications satellites. He is remembered by colleagues as an inspirational team leader. He suggested a cheaper alternative to the standard circular orbit designed by Arthur C. Clarke for communications satellites; by describing an ellipse and so coming closer to the earth for part of the orbit it was possible for satellites to carry a greater payload and yet provide excellent coverage of the northern hemisphere. Called the "Hilton orbit", it is still in use today by Russia under the Molniya programme. However, following the short-sighted decision by the British government not to press ahead with communications satellites, which became a multi-million-dollar industry, he was forced to change direction.

Hilton spent 18 months from 1963 in Paris as Secretary of the International Astronautical Federation and continued to attend their annual congresses for the rest of his life. Indeed, he presented a paper, "Communications with Extra Terrestrial Intelligence (CETI)", to the Peking Congress in 1996 at the age of 84, since he saw this as the next great step. He worked for the British Aircraft Corporation from 1966 as Assistant to the Technical Director, before taking early retirement in 1973 to pursue his many other interests and to continue his work on the Councils of the Royal Aeronautical Society and the British Interplanetary Society.

Bill Hilton's hobbies were many and varied. He had played the ukulele since his mother bought him one from a market stall for 2s 6d as a child; since he had never seen one before, he began by playing it upturned on his lap. In his later years he became a member of the George Formby Society and the Ukulele Society of Great Britain; he recalled with enthusiasm a meeting with Formby himself. A number of scientific conferences throughout the world were enlivened by Hilton and his ukulele. He was also a keen skater and a pelargonium grower, who had plants in bloom throughout the year.

William Frank Hilton, aerodynamicist; born London 10 June 1912; Principal Scientific Officer, National Physical Laboratory 1935-46; Aerodynamics Group Supervisor, Applied Physics Laboratory, Johns Hopkins University 1946-49, Chief Aerodynamicist, Armstrong Whitworth 1950-59; Leader, Astronautics Section, Advanced Projects Group, Hawker Siddeley 1959-61; Secretary, International Astronautical Federation 1963-64; married 1939 Joan Unwin (one son, two daughters); died Epsom, Surrey 6 March 1997.