A Jet Propulsion Apparatus MARTIN M E Y E R Brooklyn College, Brooklyn, New York
T
HE diagram illustrates an apparatus designed to show the rocket and jet propulsion principles.
0 .----- .- - -...-. - -.-
The flask contains water which, when boiled, spins the long vertical arm vigorously. The principle was first
employed by Hero of Alexandria more than 2000 years ago, and one sees in i t the lawn sprinkler and other familiar devices. But the particular apparatus is new as far as the writer knows. It may be readily constructed from materials available in the elementary chemistry laboratory-Florence flask, glass tubing, stopper, and two small washers (W and W'), cut from rubber tubing to fit tightly. Relative sizes make little difference, but: 1. The short outer glass tubing or sleeve, A , should be nearly the size of the inner rotor tubing, R. The contact surface may be lubricated with petroleum jelly, but this is not imperative and two suitable pieces of tubing are easily selected. 2. The washers merely hold the rotor in place. They need not close the openings above and below them, and it is better if there is a little play, say, inch. 3. It may be necessary to experiment a little with the size of the nozzle a t the tip, which should not be too small. 4. The rotor arm should be about 3 inches long, and the jet tube should bend backward a t about 45'. 5. The rubber stopper should be wired to the flask a t D. The water should not boil too rapidly, or, in a remote chance, the flask might explode. Some quantitative characteristics of jet propulsion may be measured with this apparatus with fair results. The drawing, i t is gratefully acknowledged, was made by Miss Ruth Bernholz.
