In the late 1930s Thomson was investigating the possibility of achieving a sustained chain reaction of uranium fission by neutrons. Blackman was one of several people involved, and contributed by making theoretical calculations concerned with neutron diffusion. The work resulted in his being appointed to serve on the British Committee on Atomic Energy during 1940 and 1941. Later, from 1942 to 1945, he carried out scientific work for the Ministry of Home Security mainly involving the properties of foams used in fire-fighting; some of the work ws published after the war.