FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

50 SMITHSONIAN ANNALS OF FLIGHT
place of honor among the pioneers of space exploration.
4
Introduction
On my own initiative and having remained to
the very end the only technician working on this
great problem—the design, production, laboratory
experimentation, static tests and numerous flight
tests of rockets of my invention—I was able during
the years prior to 1939 to develop a number of
rocket prototypes which, at that time, were in the
forefront of progress.
From the beginning, I used only solid fuels, in
particular, fine-grain slow-burning mine powder.
This I succeeded in "taming" by markedly increasing
the combustion time and by burning parallel
layers at a strictly constant speed. With the help
of the Central Pyrotechnics School of Bourges, I
was able to obtain blocks of a composite powder,
strongly compressed and homogeneous, which
always gave the best results. As often as possible,
I chose for my tests sunny days without appreciable
wind. My theoretical study and an analysis of the
combustion process may be found in my first book,
Self-propelled Rockets, published in April 1935. 5 My
second book was published on 11 January 1938.
The use of my compressed powder with internal
nozzle enabled me to obtain the specific gravity of
1.48, as compared with 0.83 for uncompressed black
powder. Average combustion speeds always proved
to be remarkably constant. They varied, depending
on the type of Louis Damblanc rocket, between 13
and 20 mm per second. The combustion always took
place in successive concentric layers around the
internal conical area. During all our tests up to
1939, the combustion of the charge was always
constant and stabilized in each stage.
From the very beginning of my research, I was
struck by how little care had been given to the
construction of the rocket. In my large rockets, we
employed ordinary sheet metal from 2 to 3 mm
thick, singly-riveted along the whole length. Use of
this primitive structure was feasible only because
of the very small pressures developed during combusion.
The very frequent overpressures, on the
order of 10 times ordinary pressure, resulted in
immediate failure. The self-propelled rockets designed
by me developed pressures 60 times greater
in ordinary operation.
The test firing took place at the Bourges Firing
Ground (Central Pyrotechnics School). A large
number of experiments were made at the test bench
and in vertical launches, because angular launching
over a very extensive ground did not permit the
rockets to be recovered easily.
Development of Test Means for Automatic
Axial Pressure Recording
My test stand, shown diagrammatically in Figure
1, was designed to provide the following:
1. Measurement of the maximum thrust value of
a rocket by the compression of a previously
calibrated spring.
v *$77w;
FIGURE 1.—General diagrammatic view of the rocket test
stand. Tube (1) constitutes the combustion chamber intended
to receive the rocket, open at the upper end to let the combustion
products escape and including a bottom (2) intended
to receive and transmit the reactive forces resulting from
rocket operation. The forces are found by measuring the
elastic strains on a coil spring (3). Every stress on the bottom
(2) results in depression of spring (3) and in displacement
of tube (1), transmitted to a pointer (13) inscribing the
corresponding curve on drum (15) driven by a clockwork
mechanism.