William Alan Stewart Butement (18 August 1904 – 25 January 1990) was a New Zealand-born British-Australian defence scientist and public servant. A native of New Zealand, he made extensive contributions to radar development in Great Britain during World War II, served as the first chief scientist for the Australian Defence Scientific Service, then ended his professional career with a research position in private business.
Early life
Alan Butement was born at Masterton, New Zealand, the son of New Zealand-born William Butement, physician and surgeon, and his English-born wife Amy Louise Stewart. When Alan was age eight, the family moved to Sydney, where he started at The Scots College. After a year, the family moved again, this time to London, England. He graduated from University College School and then studied at University College, University of London, where he attended lectures by Edward Victor Appleton and received the BSc degree in physics in 1926. He followed this as a research student for two years. He married Ursula Florence Alberta Parish on 17 June 1933.
Achievements in Great Britain
In 1928, Butement joined the War Office's Signals Experimental Establishment (SEE) at Woolwich, London, as a Scientific Officer, developing radio equipment for the British Army. He and an associate, P. E. Pollard, conceived a radio apparatus for the detection of ships. A breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation, gave successful laboratory results, but was not of interest to War Office officials. Nevertheless, in January 1931, a writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that would eventually become radar.
In October 1936, Robert Watson Watt's team working for the Air Ministry began work on what would become Chain Home (CH). By 1936 they had moved to the Bawdsey Manor Research Centre (on the North Sea coast) and had already begun plans for deployment of the CH system. Referred to as Range and Direction Finding (RDF), Bawdsey had by this time begun branching out, forming teams to design and build all sorts of radar related devices. An Army Cell from the SEE was attached to the Bawdsey operation. Butement was among those representing the War Office.
At Bawdsey, Butement was assigned to develop a Coastal Defence (CD) RDF system to be used for aiming anti-shipping and anti-aircraft guns. By early 1938, he had a prototype under test. This used a pulsed 1.5 m (200 MHz) transmitter producing 50 kW power, (later increased to 150 kW). For the transmitting and receiving antennas, he developed a large dipole array, 10 feet high and 24 feet wide, giving narrow transmitting and receiving beams. This array could be rotated at a speed around 1.5 revolutions per minute. To improve the directional accuracy, lobe-switching was used in the transmitting array.
Primary credit for introducing beamed RDF systems in Great Britain must be given to Butement. As a part of this development, he formulated the first – at least in Great Britain – mathematical relationship that later became well known as the "radar range equation".
In September 1939, at the start of the war, operations at Bawdsey were distributed to safer locations. The Army Cell joined the Air Defence Experimental Establishment (ADEE) at Christchurch in Dorset on the south coast. At the time of the move, Butement was named an Assistant Director of Scientific Research, and continued to lead the Coastal Defence (CD) research activity. The primary use of the evolving CD system was in aiming searchlights associated with the anti-aircraft guns, and Butement acquired the nickname of 'Mr. Searchlight Radar.' He also developed what became the standard method of determining miss-distance of gunfire against shipping by using RDF echoes from splashes caused by shells hitting the sea.
There was an urgent need to improve the effectiveness of the anti-aircraft guns. With his background in radio, in October 1939 Butement turned to this technology as a potential solution. He conceived of a highly compact RDF set placed on the projectile, setting off the detonation when close proximity to the target was attained. He completed the circuit design, but there was the problem of packaging such a device in a small projectile, as well as the question of the vacuum tubes surviving the acceleration forces at firing.