German V-1 flying bomb - final design and lauching specs

Ground-launched V-1s were propelled up an inclined launch ramp by an apparatus known as a Dampferzeuger ("steam generator"), in which steam was generated when hydrogen peroxide (T-Stoff) was mixed with sodium permanganate (Z-Stoff).
Designed by Hellmuth Walter Kommanditgesellschaft, the WR 2.3 Schlitzrohrschleuder consisted of a small gas generator trailer, where the T-Stoff and Z-Stoff combined, generating high-pressure steam that was fed into a tube within the launch rail box.
A piston in the tube, connected underneath the missile, was propelled forward by the steam. It is a common misconception that this was done to allow the engine to start running but this is not true. It was done because the Argus didn't have enough power to propel the V1 to a speed over its incredibly high stall speed.
The launch rail was 49 m (160 ft) long, consisting of 8 modular sections, each 6 m (20 ft) long, and a muzzle brake. Production of the Walter catapult began in January 1944.