Hot-Water Rocket

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 with 66 Ibs. of water heated electrically to 504DEG F. The water cannot boil because it is confined, but its pressure rises to 50 atmospheres (735 Ibs. per sq. in.). When the valve is opened, part of the water turns into steam, and a jet of steam and water spurts out at 1,140 m.p.h. The reaction, Michely claims, can push an airplane forward just as efficiently as a fuel-burning rocket, and much more cheaply. When electricity is used for heating, the same amount of thrust costs less than one-seventieth as much as with a solid-fuel rocket. Other heat sources would be even cheaper.

Michely has tested his hot-water rocket only on the ground, but he thinks it has a bright future in the air, both for horizontally and vertically launched aircraft. Besides its cheapness, it is comparatively safe because of its low pressure and temperature, and its single valve is its only moving part.

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