The camera and its film magazines with an inertial navigation system were carried in a cramped "Q-bay" below the drone's air intake. These components were built into a module that fit into the bay and was known as a "hatch". The hatch would be ejected at the end of the mission and then snagged out of the air by a JC-130 Hercules, a technique that had been developed by the USAF to recover film canisters from satellites. If the C-130 missed, the hatch was equipped with flotation devices so it could be recovered by ship if released over water. Honeywell built the avionics systems; new construction techniques and materials had to be developed for the systems to withstand the high temperatures, extreme vibrations and lack of space in the D-21.