FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

222 SMITHSONIAN ANNALS OF FLIGHT
Considering this state of development, economical rocket
flight operations over distances of several thousand miles
may be possible in the foreseeable future, as soon as the
remaining deficiencies in Sander's rocket engines can be
eliminated.?
Afterwards, however, no one ever heard again of
Sander's liquid-propellant rockets, and it has remained
unknown whether the reasons were personal
or due to actual deficiencies in his liquidrocket
engines. As far as the co-author remembers,
Sander's liquid rockets had capacitive cooling only
and oxygen-rich combustion.
At least from 1924 on, Max Valier had dreamed
of a spacecraft with rocket propulsion as the ultimate
goal of his work, but had never put into writing
any details regarding the proposed propulsion
system. Thus, for a long time, the question remained
open whether he envisaged a turbo-engine
or a solid- or liquid-propellant rocket as the final
solution. Only in January 1930 did he begin to develop
his own liquid-propellant rocket engine after
having received, at the end of 1929, some support
for his project from the Heylandtwerke in Berlin-
Britz. After preliminary combustion tests with
alcohol and gaseous oxygen, he ran his engine,
called "Einheitsofen" (standard combustion chamber),
for the first time on 26 March 1930, with liquid
oxygen. With this combustion chamber, weighing
about 4 kg, Valier made the first successful test
runs of the RAK-7 automobile on 17 and 19 April
1930. The fuel and liquid-oxygen tanks were completely
separated from each other, one located in
front and the other in back of the driver's seat. As
to the cooling problem, the Einheitsofen did not
show any fundamental improvement over the conical
nozzle. The combustion gas temperature was
kept low by adding water to the alcohol, so that
capacitive cooling was sufficient. One of Valier's
associates, Walter J. H. Riedel, wrote about the
Einheitsofen:
The chamber was made of standard steel tubing. At one end
was the expansion nozzle and at the other the propellant
injection system. Oxygen was fed through a number of small
bore holes from the pre-mix chamber into the combustion
chamber. The fuel was injected into the chamber against
the flow of the oxygen gas. A drag disk reduced the velocity
of the oxygen gas flow by producing vortex fields.s
Valier had planned to continue the development
of his combustion chamber with the aid of the Shell
Oil Company, and thus had to commit himself to
using Shell oil (kerosene) instead of alcohol. Of
course, this increased the cooling problem. Riedel
reported on this as follows:
Instead of using alcohol, as before, Shell oil had to be used.
Alcohol is a fuel that can be mixed with water in any
desired proportion, allowing reduction and determination of
the combustion temperature. With kerosene, this is not that
easily done. By adding water to kerosene and shaking it, an
emulsion forms for a short while, during which kerosene
and water mix; afterwards, they quickly separate again. In
order to maintain the integrity of the combustion chamber
walls, the gas temperature had to be kept within certain
limits. The problem was solved by feeding the kerosene,
prior to entry into the combustion chamber, through a
so-called emulsion chamber. 9
On 17 May 1930, Valier was killed during preliminary
tests with this emulsion chamber. Less
than a year later, on 11 April and 3 May 1931,
Alfons Pietsch, a senior engineer of the Heylandtwerke,
made another test run of the RAK-7 with
an improved rocket engine weighing about 18 kg.
According to Willy Ley 10 this engine must have
yielded a thrust of 160 kg and been cooled by the
fuel, but no proofs or any further data on the type
of cooling used were ever found.
At the end of 1929, Johannes Winkler, in the
journal Die Rakete, suggested the construction of
long cylindrical combustion chambers for methaneliquid
oxygen with ceramic lining of the nozzles
near the throat area. In summer 1930, he began to
build his first liquid-propellant rocket engine, which
he called a Strahlmotor (jet engine), and at the end
of the year he started to run his first ground tests.
The first firing attempt, on 21 February 1931, was a
failure; but the second firing of the complete aggregate
HW-1 (Hiickel-Winkler-Astris 1), at Gross-
Kuehnau near Dessau on 14 March 1931 has been
recorded in the annals as the first flight of a liquidpropellant
rocket in Europe. The rocket—about 60
cm long, its main structure made of aluminum
sheet, and with a launch weight of about 5 kg—
consisted of a triangular arrangement of three tubelike
containers for methane, liquid oxygen and
compressed nitrogen for pressurization. The engine,
45 cm long, was made of seamless steel tubing and
positioned approximately along the centerline of
the assembly.
In October 1931, in a rented room of the Berlin
Rocket Field, Winkler and his first assistant, Rolf
Engel, began construction of the HW-2, bigger and
with a length of 1.50 m and take-off weight of 50 kg.
This rocket—with spherical propellant tanks ar-