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Henry Bull's Impulse Engine of 1935

This a fairly simple %u201Cmotion rectifier%u201D that lends itself to home experimentation. It can probably be built with solenoids manufactured for sprinkler controls and some simple electronics. Henry Bull demonstrated this in 1935. At that time there was no space program, so its feeble thrust was eclipsed by the alternatives of the day. Today, however, even a feeble thrust, produced continuously over a long period of time, has great significance to the space program, especially since it expends no fuel. The principle can best be explained by referring to the diagram below. Imagine a tube with a guide rod in its center. Around the guide rod are two toroid shaped masses, heavy iron washers perhaps. A compression spring is placed in the middle between the masses. At only one end of the tube is another spring. The other end has no spring. The actions of the masses are controlled by solenoid coils wrapped around the tube (not shown). (One could probably also construct this by putting the solenoids on the rod and having them serve dual purposes as both motivators and masses).
Henry Bull's Impulse Engine of 1935


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