Many airplanes, especially heavy-laden bombers, are launched by booster (jato) rockets whose powerful push gets them into the air without too long a take-off run. The rockets are expensive, whether they use liquid or solid fuel, so the West German Ministry of Transport asked jet-propulsion experts to evaluate hot-water rockets, a prewar German idea that never got a thorough tryout. Recently, Physicist Werner Michely told a meeting at Freu-denstadt that hot-water booster rockets look promising.
Michely constructed a simple device: a strong-walled pressure vessel with a valve and a nozzle at one end. When used as a rocket booster, it is filled...