FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

NUMBER 10 297
I remember being so frustrated by the fact that the
power was cut off at 5 p.m. that many times I would
set up to take a cut, lose the power, and then pull
the lathe through by hand. Under such circumstances,
it is not surprising that it took about eight
months to complete the first test combustion chamber.
When my masterpiece was completed, I took it
to the head of the Marine Engineering Department
and requested permission to set it up in the foundry
and fire it. In perhaps justifiable concern over the
future of Isherwood Hall, permission was denied.
I found a much more receptive climate, however,
across the Severn River at the Experiment Station.
After a third-degree interrogation by several heads
of departments, concerning in particular the safety
of my proposed operations, it was decided to let
me have a go at it. Not only was I given permission
to work at the Experiment Station, but some
assistance was provided in the form of materials.
In addition, a little welder named Sugar Evans
was assigned to give me a hand in the construction
of the rocket test stand.
In order to complete the test that I had programmed,
I had to forego my September leave, and
I was most annoyed to find that construction of an
item as prosaic as a test stand required nearly half
of my leave period. Nowadays, of course, construction
of a rocket test stand requires upwards of 18
months and many millions of dollars. Sugar Evans
and I took a very practical approach, although not
a very elegant one. In making the propellant tanks,
we went out to the stock rack, selected some steel
pipe of approximately the right size, and pulled it
out to what appeared to be about the right length.
Sugar, whiz that he was with the cutting torch, then
cut the pipe off at the proper length without even
removing it from the stock rack. We then made
closures for the tanks by burning circles out of
boiler plates, welding them in, and providing them
with gussets which appeared to both of us to be
about adequate in thickness and strength. There
was a tank for the fuel, a tank for the liquid oxygen,
and since the thrust-chamber design utilized a nozzle
cooled in part by an injection of water, there was
also a tank for cooling water.
Instrumentation was characteristically simple and
direct, involving the use of Bourdon tube pressure
gauges, an Eastman Kodak timer, and best of all, a
stock-room scale on which the thrust chamber was
mounted in a nozzle-up position. In operation, the
beam rider on the scale was set to the thrust
desired, and the valves were opened until that
thrust was obtained. The instruments were then
photographed with a Boy Scout camera at intervals
determined primarily by the time required to wind
the film on the camera. The fuel consumption was
measured by means of a boiler gauge glass.
Although such flow measurements were undoubtedly
highly inaccurate, they were no more inaccurate
than the measurement of the thrust itself.
And at any rate, it was not accuracy, but the principle
of the thing that counted at this stage of the
game.
Tests of December 1937
Before completion of the test stand, I went to the
Industrial Superintendent, Mr. John K. Amos, and
announced that I was ready for my tests and would
need an adequate supply of liquid oxygen and
gasoline. I might as well have asked for an atomic
bomb. Mr. Amos replied that the U.S. Naval
Welding Regulations specifically forbade the use
of oils or hydrocarbons in conjunction with oxygen
of any kind, and there was no supply of liquid
oxygen at the Experiment Station or any place in
the vicinity. Mr. Amos volunteered, however, that
there was an adequate supply of compressed air at
very high pressure available from some torpedo air
compressors, and that I would be allowed to use
this compressed air as the oxidizer for the gasoline.
This fact probably proved to be a very favorable
turn of fate, since the compressed air supply
allowed me to run my thrust chamber for relatively
long periods of time. It also avoided the difficulties
which undoubtedly would have been encountered
in the use of liquid oxygen.
Figure 2 shows one of the first tests in progress.
The thrust chamber rested on a beam balance with
the nozzle pointed skyward. The thrust and mixture
ratio were controlled by hand valves in the propellant
lines.
Thrust and chamber pressure were the only
variables of significance measured. The motor operated
for several seconds but was initially very
difficult to control. The maximum chamber pressure
attained was 150 pounds per square inch. The
thrust was about ten pounds.