Instead of returning to the Cavendish, the team moved to
Exeter, where Dee and three others worked on developing rockets as anti-aircraft weapons, while Strothers and Curran joined a group under John Coles working on the development of the
proximity fuse. Strothers was based at
Leeson House and
Durnford School. She and Curran developed a workable fuse, which was codenamed VT, an acronym of "Variable Time fuse". The system was a small, short-range, Doppler radar that used a clever circuit. However, Britain lacked the capacity to mass-produce the fuse, so the design was shown to the United States by the
Tizard Mission in late 1940. The Americans perfected and mass-produced the fuse. In due course, these proximity fuses arrived in the United Kingdom, where they played an important part in the defence of the kingdom against the
V-1 flying bomb. dropping chaff (the crescent-shaped white cloud on the left of the picture) over
Essen during a thousand-bomber raid Strothers married Curran on 7 November 1940. Soon afterwards they were transferred to the
Telecommunications Research Establishment near
Swanage, where Sam worked on
centimetric radar, while Joan joined the Counter Measures Group in an adjoining lab. It was with this group, at Swanage, and later at
Malvern, that Joan devised the technique that was codenamed Window, which is also known as
chaff. She tried various types of radar reflectors, including wires and sheets, before settling on strips of
tin foil wide and long that could be scattered from bombers, thus disrupting the enemy's radar. Window was first employed in
Operation Gomorrah, a series of raids on
Hamburg, and resulted in a much lower loss rate than usual. As part of
Operation Taxable on 5–6 June 1944, Window was dropped by
Avro Lancasters of
617 Squadron to synthesise a phantom invasion force of ships in the
Straits of Dover and keep the Germans unsure as to whether the brunt of the Allied assault would fall on
Normandy or in the
Pas de Calais area.
R. V. Jones later declared: "In my opinion, Joan Curran made an even greater contribution to victory, in 1945, than Sam." They joined the
British Mission at the
Berkeley Radiation Laboratory in California, headed by
Mark Oliphant, a distinguished Australian scientist that Joan knew from the Cavendish Laboratory. Oliphant also acted as
de facto deputy to
Ernest Lawrence, the director of the Radiation Laboratory. The mission of the laboratory was to develop the electromagnetic
isotope separation process to create
enriched uranium for use in atomic bombs. While at Berkeley, Joan gave birth to her first child, a daughter, Sheena, who was born severely mentally handicapped. They later had three sons, all of whom went on to complete a
PhD. ==Later life==