FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

298 SMITHSONIAN ANNALS OF FLIGHT
FIGURE 2.—First test in progress.
With the first combustion chamber we made a
considerable number of more-or-less successful tests
at increasing thrusts, finally running the apparatus
for periods as long as several minutes at a time. I
would frequently run the tests during the lunch
hour when the workmen from the shop would
come out, gather around the rocket, and amuse
themselves by throwing stones into the jet to see
how high they would be hurled. I remember once
two of the men got a large board and attempted to
force it into the jet. Although the thrust of the
rocket was only about 25 pounds, they found it
difficult to hold the board in position against this
force.
The tests were duly reported in the April 1938
issue of the journal of the American Rocket Society 4
and constitute some of the very earliest measurements
on rockets ever described.
Tests of September 1938
After the first set of tests, it was obvious that a
man with only two hands could not juggle three
valves—air, gasoline, and water—simultaneously,
especially since smooth combustion could be obtained
only at certain very delicate settings of the
mixture ratio. During the succeeding months, the
chamber was modified to eliminate the water by
using refractory nozzles. A continuously indicating
thrust measuring device was provided and a gauge
glass was added to the gasoline tank. A Kodak timer
was used, and the gauges were photographed by a
still camera at intervals determined by the length
of time required to wind the film. Figure 3 shows a
typical photographic record of the instrument panel.
In September 1938, another series of tests was
made, again using compressed air and gasoline.
Three types of refractory nozzles were used; graphite,
fireclay, and aluminum oxide cast from thermit
slag. Except for the nozzle change, the motor was
identical to that used previously. Only the aluminum
oxide nozzle was found satisfactory; the others
eroded too rapidly. With the A1203 nozzle, however,
runs of many minutes could be made before
the chamber became overheated. 5
For record purposes, runs from 15 to 45 seconds
were made. The data obtained in these September
1938 tests are summarized in the following tabulation:
FIGURE 3.—Instrument panel.