Gamma engines were manufactured by Bristol Siddley and used on the Black Knight and Black Arrow launch vehicles. Propellants were High Test Peroxide and Kerosene. Black Knight used 4 chambers in two pairs on the Y and Z axes. The motors were gimballed to provide thrust in all axes.

Black Arrow was a three stage vehicle. The first stage had an 8 chamber layout with 4 pairs of Gamma engines gimballed as with Black Knight giving thrust in all axes. The second stage had two Gamma chambers with extended nozzles to give full expansion in vacuum. Both engines were gimballed to provide thrust in three axes.