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 long, consisting of 8 modular sections, each long, and a muzzle brake. Production of the Walter catapult began in January 1944. The Walter catapult accelerated the V-1 to a launch speed of , well above the needed minimum operational speed of . The V-1 made British landfall at , but accelerated to over London, as its of fuel burned off. On 18 June 1943, Hermann Göring decided on launching the V-1, using the Walter catapult, in both large launch bunkers, called Wasserwerk, and lighter installations, called the Stellungsystem. The Wasserwerk bunker measured long, wide, and high. Four were initially to be built: Wasserwerk Desvres, Wasserwerk St. Pol, Wasserwerk Valognes, and Wasserwerk Cherbourg. Stellungsystem-I was to be operated by Flak Regiment 155(W), with 4 launch battalions, each having 4 launchers, and located in the Pas-de-Calais region. Stellungsystem-II, with 32 sites, was to act as a reserve unit. Stellungsystem-I and II had nine batteries manned by February 1944. Stellungsystem-III, operated by FR 255(W), was to be organized in the spring of 1944, and located between Rouen and Caen. The Stellungsystem locations included distinctive catapult walls pointed towards London, several "J"-shaped stowage buildings referred to as "ski" buildings as on aerial reconnaissance photographs the buildings looked like a ski on its side, and a compass correction building which was constructed without ferrous metal. In the spring of 1944, Oberst Schmalschläger had developed a more simplified launching site, called Einsatz Stellungen. Less conspicuous, 80 launch sites and 16 support sites were located from Calais to Normandy. Each site took only 2 weeks to construct, using 40 men, and the Walter catapult only took 7–8 days to erect, when the time was ready to make it operational. Once near the launch ramp, the wing spar and wings were attached and the missile was slid off the loading trolley, Zubringerwagen, onto the launch ramp. The