FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

NUMBER 10 261
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FIGURE 2.—Unge's early rockets: a, First rocket tested in 1892. b, Second type, with two exhaust
pipes and one combustion chamber, diameter 50 mm (2 in), length 300 mm (12 in), c, Third
type, with two combustion chambers, d, Type with uniformly thick, oblique exhaust orifices.
e, Modification, with conical, oblique exhaust orifices and a 300-mm (12 in) guidance tube.
turbine "consisting of conical inlet canal (a) and
likewise conical outlet canal (b), which at (c) encounter
the smaller section (minima-section)," according
to the patent. This is also the definition of
the de Laval nozzle, even if the construction was not
as finished and complete as today, but it was the
first time the de Laval nozzle principle had been
used in rocketry by a designer who knew why it was
applied to the rocket. Patents on this gas turbine
were approved in 12 countries.
A calculation, using the dimensions of the turbine
and the pressures to be found in one of Unge's
notebooks, gives the exit mach number as M = 2.9.
Unge scaled the dimensions of the turbine to fulfill
the requirements of an isentropic expansion usable
in all three types of rockets he had in production.
This invention turned out to be so effective that
the use of a rotation gun was no longer necessary.
Unge therefore designed new types of lightweight
launching tubes, consisting simply of a number of
cylindrically arranged guides (Figure 4). The sim­
plification of the launch tube made the field handling
of the rocket much more sophisticated, and
there were no longer any restrictions on the designing
of bigger rockets.
The name "aerial torpedo" was for the first time
officially used in this turbine patent of 1897. Two
years after this invention Dr. Gustaf de Laval joined
the board of the Mars Co., which even more stresses
the fact, that Unge was well aware of the de Laval
nozzle principle through early contacts with its
inventor.
Parallel with the work on the stabilization problem,
Unge gave his attention to improving the
rocket propellant. In the first types of rockets Unge
used a propellant consisting of ordinary gunpowder,
but his collaboration with Alfred Nobel gave rise
to an extensive series of experiments to improve
ballistite, invented by Nobel in 1888. The first
known "successful" firing of a ballistite rocket (Figure
5) was made on 12 September 1896 in Stockholm.