Harry W. BULL
Popular Science Monthly (January 1935), p. 27
Powered by Reaction Motor"
Imagine a heavier-than-air
flying craft devoid of any visible means of propulsion, which
rises from the earth and travels through the air in apparent
defiance of gravity. Lifting itself by its own bootstraps, by
slinging weights about its interior, it could navigate at will
in the stratosphere or even in the unknown reaches of outer
space. Such a craft is brought within the realm of speculation
by pioneer experiments of Harry W. Bull, of Syracuse, NY, with
an entirely new form of propulsion that he terms the reaction
Suspended from a pair of
light, flexible wires, in his laboratory, hands a cylindrical
tube about a foot long. At the touch of an electric switch, it
becomes alive and leaps forward, as if drawn by some invisible
magnet. Actually the power plant, a curious system of
reciprocating weights, is contained within the tube itself.
This elementary form of
reaction motor operates on a principle that has long been
neglected by engineers, but which Bull believes can be applied
in aircraft and other vehicles. It depends upon the difference
in effectiveness of two ways of transmitting energy, which can
be termed impact and impulse. If a weight is thrown against a
solid wall, it is stopped by impact, and much of its energy is
wasted in distorting the weight and wall and in producing
heat. However, if the weight is thrown against a spring
fastened to the wall, it is stopped by impulse, the spring
conserving the energy of the moving weight and transmitting
the resulting force, with little loss, to the wall. Tests have
shown a weight will yield three times more force by impulse
than by impact.
Figure 1 ~ Here is our
artistsís conception of the proposed globular aircraft which
is to be driven by shifting weights.
Figure 2 ~ Diagram shows
how force would be obtained from reciprocating weights
striking against the springs.
Figure 3 ~ Harry W. Bull,
inventor, exhibits an experimental model of his reaction
motor with which he hopes to power an aircraft that will,
apparently, defy gravity. When the power is shut off the two
pointers, above, coincide. Weights in the device are
operated by electromagnets.
Applying this principle in
the manner shown in the accompanying diagram, he mounts two
movable weights in a cylinder and starts them simultaneously
in opposite directions. One is stopped by a flat steel plate,
and the other by a spring. The difference in the effectiveness
of the two blows, as explained above, is sufficient to kick
the cylinder forcibly in the direction of the spring. The
weights may be returned to their original positions by any
standard mechanical means, and the cycle repeated
continuously, providing a steady and self-contained driving
force without recourse to propellers, rocket jets, or any
other familiar means of propulsion.
From the present
experimental model to a reaction motor powerful enough to lift
aircraft seems a long step. Achieving a practical reaction
motor, Bull points out, depends to a large extent,
paradoxically, upon how inefficient it can be made. The more
force that can be wasted in impact, the greater force will be
left to push ahead, a new problem for engineers, who have
spent years trying to conserve energy rather than dissipate
it. Likewise, much experimentation remains to be done upon the
impulse side of the apparatus, which is still far from
Supposing these difficulties
overcome, what would an airship, driven by a reaction motor,
look like? Bull visualizes a globular craft with a motor in
the form of an upright cylinder containing two pistons
operating in opposite directions, one delivering an impulse
and the other an impact. A carburetor adapted for mixing
vaporized oxygen and gasoline would supply an explosive
mixture to drive the pistons. Several cylinder units could be
used to obtain a steady lifting force. Others placed
horizontally would provide forward motion. A similar
impulse-impact cylinder of reduced size, operated electrically
and mounted near the outer shell of the ship, would rotate the
craft for steering. An airship driven by this new method could
travel at high speed and could be used at either high or low
the American Rocket Society 29: 7-8, (Sept.
"(5) Entirely New Reaction Methods"
entirely new means of securing a reaction was next tested.
The rocket was made up of a series of chambers the ends of
which consisted of steel disks fastened together by a 1/4
inch diameter steel rod. The chambers were arranged to
explode in series, blowing the steel disks downward with
great velocity. Knowing the weight of the disk and its
velocity and also the weight of the complete rocket it is a
simple matter to find the energy of the recoil. Although
this type of rocket works, it leaves much to be desired in
the line of safety.
series of tests now followed which I believe are original in
the field of reaction. They dealt with a form of
impact-impulse reactions which are created mechanically. The
apparatus if placed in a box in space would move without the
use of a jet of any sort, it being propelled by a
reciprocating motion of two weights. The truth of the theory
may be easily proven by a very simple apparatus.
theory is that a large weight with a low velocity ( if
stopped by springs ) will yield more foot pounds of energy
than a small weight with a high velocity being stopped by
impact, even though both were given the same initial force.
A simple illustration: Let us assume you are in the center
of a room in space. One wall is elastic and the opposite one
solid. In your hands are two balls one heavy and the other
light and you throw them with the same force at the same
time. The heavier one hits the elastic wall with an impulse
and a large amount of energy is given to the room in that
direction. The lighter one having the same energy hits the
solid wall but its energy is dissipated in heat and
distortion. If there could be found a method whereby the
kinetic energy of the lighter ball could be effectively
utilized the room would move in the other direction.