The electronics, made from vacuum tubes, generated significant heat. For this reason, the Firestreak missile undergoing a ground test was cooled by Arcton, and in-flight by ammonia pumped through the missile from bottles in the rear of the launching "shoe". The bottles contained enough ammonia for 15 minutes, so the missile could only be started up during the approach. An air bottle in the fuselage-mounted weapon pack kept the ammonia bottles pressurized before launch. Hot air from the engine compressor stages connected to the rear of the launch pack and was routed to the missiles. During flight, this kept various moving components warm, warm enough that they would not freeze up during the 13 second flight time.