While starting his engineering career with MIT during the 1930s to 1940s, Grier co-invented a miniature stroboscope and handheld flash with Harold Edgerton and Kenneth Germeshausen.

During World War II, Grier built a firing mechanism during the Manhattan Project that was used in the Fat Man bomb.

Apart from electrical engineering, he took part in NASA safety boards that assessed Skylab and the preparation of the first Space Shuttle.

[2] During this time period, Grier co-invented a miniature stroboscope alongside Harold Edgerton and Kenneth Germeshausen in 1934.

[3] While working on aerial photography for Edgerton during World War II, Grier joined the Manhattan Project and built the firing mechanism used in the Fat Man bomb.