FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

NUMBER 10
FIGURE 5.—Small fin-stabilized rocket, which used a single
tubular grain, and test chamber for it (bottom).
in the chamber shown in Figure 7, where again only
the pressure was measured. Figure 8 shows, superimposed,
three pressure records from this apparatus,
all corresponding to the same burst pressure of 100
atm (nominal). The poor reproducibility of the
pressure level is evident, and as a result the rocket
wall had to be designed rather thick. However, it
was still sufficiently thin to become overheated. In
the first rockets launched, the wall reached red heat
at the end of the combustion time. To avoid overheating
a thin insulating layer of asbestos was inserted
between the chamber wall and the propellant.
These rockets were launched with good results
and reached velocities of about 1000 fps, which
were in agreement with the estimated velocity. The
main inconvenience observed in the launching of
both types of rockets was the lack of accuracy of
their trajectory. It was attributed to the erratic
transverse displacement of the center of mass resulting
from the fact that there was nothing to
prevent the lateral motion of the three tubular
charges when their diameter decreased. To restrict
this motion, stabilization by spinning the rocket
about its axis was attempted by impressing a fast
rotational speed to the rocket holder prior to ignition.
This launcher is shown in Figure 9. The whole
rocket holder was set in rotation by an electric
motor. Moreover, the three tilted exhaust nozzles
provided a tangential thrust component after
launching. The ignition burst diaphragms were
replaced by shear pins (r) which firmly held the
exhaust nozzle terminal sections pressed against a
terminal plate until a preassigned pressure was
reached. In another version of the spinning rocket
the initial rotation was obtained through a fast
burning charge located in an annual chamber
around the single exhaust nozzle. This charge was
ignited just prior to the main charge and exhausted
through small tangential nozzles. The spinning
rockets did not provide any more precise trajectories
than the fin stabilized rockets.
Further Research on Solid Propellants
Late in 1928 my father was called from the reserve
back to active duty as a general and asked to
become Direttore Generale delle Costruzione
Aeronautice in the Ministry of Aeronautics, while
still continuing his teaching activity as a professor
of the School of Aeronautical Engineering. This
event had two important effects on our rocket research
program. First, the facilities of the Ministry
Of Aeronautics became available for the continuation
of our research; and, second, my father became
immediately deeply involved in pressing problems
of broader and more immediate interest. The first
was a very welcome improvement of the situation,
especially in view of the fact that the 100,000 lire
of the General Staff were almost exhausted. The
second was, on the contrary, a blow to the future
dynamic development of the applications, if not
to the fundamental aspects of the research. Indeed
I was now, practically alone, in charge of our research
effort. My father only devoted a little time
to it in the evenings, when we discussed our problems
at home. Because my mind has always been
more attracted by questions solved by basic research,
these naturally gained prevalence with
respect to questions regarding applied research. I
should add that, of course, my studies prevented
me from devoting my full attention to the research
project. The experiments took place in Rome in an
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