FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

220 SMITHSONIAN ANNALS OF FLIGHT
1930. In May, a 14-day exhibition of liquid-propellant
rockets and experimental equipment is held by the
Society for Space Travel in Berlin on the Potsdamer
Platz and afterwards in the Wertheim department
store.
1930. On 17 May, Max Valier is killed by an exploding
liquid-propellant rocket.
1930. On 27 September, the Raketenflugplatz Berlin (Berlin
Rocket Field) is founded by Rudolf Nebel.
1931. On 14 March, near Dessau, Johannes Winkler launches
a rocket using methane and oxygen. Altitude about
600 meters. The second Winkler rocket explodes during
launch on 6 October 1932, on the Frische Nehrung
near Pillau.
1931. On 11 April, at the Berlin Central Airport, Chief
Engineer Pietsch of the Heylandtwerke demonstrates
an improved Valier rocket automobile. Propellants:
alcohol and oxygen.
1931. On 14 May, at the Berlin Rocket Field, a Miter liquidpropellant
rocket (Double-Stick Repulsor) is launched
to a height of 60 meters.
1931. On 23 May, at the Berlin Rocket Field after completion
of the workshops and static test run of the
engine, a Riedel Repulsor, using gasoline and oxygen,
attains a distance of more than 600 meters. A fortnight
before, the same device had already reached
an altitude of 100 meters. Meanwhile, improved
repulsors of the same dimensions have reached distances
of 5 kilometers and altitudes of about 1.5
kilometers. Thus, the technical development of the
liquid-propellant rocket has begun.
One very important date is missing in this list,
namely 23 July 1930, the day when Hermann
Oberth together with Rudolf Nebel, Klaus Riedel,
Rolf Engel, and Wernher von Braun (who had just
received his high school diploma) demonstrated
his "Kegelduse" (cone-shaped nozzle) to Dr. Ritter,
the director of the Chemisch-Technische Reichsanstalt
(Government Institute for Chemistry and
Technology with functions similar to the U.S.
Bureau of Standards). On a rudimentary test rack of
the Institute, the Kegelduse produced about 7.7 kg
maximum thrust for a total combustion time of
96 sec. and a nearly constant thrust of 7 kg for 50.8
sec with a sub-stoichiometric composition of liquid
oxygen and gasoline. The demonstration proved so
successful that Dr. Ritter recommended further
work on this rocket engine as worthy of support by
the Deutsche Notgemeinschaft (German Foundation
providing funds for selected projects).
The rocket projects suggested by Oberth in 1923
that influenced the overall development of liquid
rockets in Germany and Austria, had already included
combustion chambers with inner dynamic
regenerative surface cooling. For example, Oberth
had proposed a two-stage high-altitude probe,
Model B, and a manned spacecraft, Model E, with
the first stage in both cases burning an alcohol-water
mixture and liquid oxygen, and the second stage
burning liquid hydrogen instead of the alcoholwater
mixture. As proposed, the thrust chamber of
the second stage would be fitted into the liquid
hydrogen tank and use the heat capacity of the
propellant for cooling; for the first stage, a novel
dynamic cooling process was proposed. Necessary
cooling was to be achieved by varying the mixture
ratio of the propellants. 2 thus reducing the combustion
temperature, and by insulating the combustion
chamber walls by a dynamic cooling film of evaporating
fuel which is the simplest method of regenerative
cooling. The absorbed heat was to pre-heat
the fuel, while the film of evaporating fuel would
protect the chamber walls from the hot combustion
gases. Oberth described this as follows:
The combustion chamber does not join directly with the
jacket surfaces. In between, there is a thin wall connected
to the jacket by metallic braces and thus held in the correct
position. Liquid from the atomizer flows between this thin
wall and the jacket, vaporizes, and thus protects the chamber
walls from burning. The vapor discharges between
atomizer and jacket into the chamber. Within the chamber,
the vapor remains near the walls; thus, with high vaporization,
the walls are being insulated from the hot gas ....
This arrangement allows the dry weight of the rocket to be
much less than it would be if chamber and nozzle were lined
with fireproof materials on the inside, and this is a considerable
advantage. It also permits the gases to pass along
the metallic surfaces which retard the flow less than asbestos
or chamotte.s
In this description, the coolant is simply called a
"liquid" and no indication exists where a supplemental
cooling system or regenerative cooling is
considered. In a different paragraph additional
information is given:
Nevertheless, in order to obtain lower combustion chamber
temperatures for the Model B, I considered weaker compositions;
i.e., for the alcohol rocket, instead of rectified
alcohol, a 13.4 percent dilute alcohol, which only gives a
combustion chamber temperature of about 1400°C and an
exhaust velocity of about 1700 m/sec ....
An additional feature of Models B and E is the insulation
of the wall by the vapor of the coolants ... so that burning
of the chamber wall is definitely avoided .... With Models
B and E, this dynamic cooling can become very effective by
letting gas, of the same chemical composition as the forming
gas, flow along the walls. According to Kirchhoff, this
absorbs almost completely the heat radiated from the inner
chamber.*