FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

230 SMITHSONIAN ANNALS OF FLIGHT
will then go much smoother. If you try today to write your
thesis on space flight, you may be an old man with a long
beard before you get your degree."
Dutifully and successfully, Sanger wrote his thesis
on "The statics of multi-spar truss wings with
parallel webs, cantilevered and half-supported, directly
and indirectly loaded," and was awarded a
doctor's degree on 5 July 1929.
From February 1930 on, Sanger worked as assistant
to Professor Rinagl at the Institute for Materials
Research of the Technical University, in
Vienna. His private work continued nevertheless.
In the second chapter of a manuscript entitled
"Cosmo-Technology" he listed under the heading
"Ship Propulsion - The Rocket as Prime Mover"
the following outline: (1) General Remarks; (2)
Rocket Theory; (3) The Chemical Rocket; (4) The
Radium Rocket; (5) The X-Ray Rocket. As "Radium
Rocket" Sanger described what we would call
today an isotope-heated propulsion system. In the
chapter "X-Ray Rocket" he put on paper some
preliminary studies on what many years later became
known as his theory of the "Photon Rocket."
Up to mid-1931, Eugen Sanger still spent most of
his time on wind-tunnel tests with three-dimensionally
curved flight profiles. Apparently, no records
are left, but the results were published by Sanger in
an article, "Cber Fliigel hoher gute" (On High-
Performance Wings), that appeared in the magazine
Flugsport (Air Sports) on 24 June 1931.
Immediately following, he began to summarize
the results of his fundamental studies on rocket
flight, using many elements from his earlier drafts
for "Stratospheric Flight" and "Cosmo-Technology."
In May 1933, they were published under the
title "Raketenflugtechnik." 26 The 222-page treatise
with chapters on "Propulsive Forces, Aerodynamic
Forces, Trajectories" was to be a fundamental theoretical
textbook. In the introduction, Sanger specified
that design details were intentionally omitted
in all discussions. Yet, some comments on the cooling
problems encountered with liquid rocket engines
were included on page 53:
One of the significant physical properties of the propellants
is their cooling capacity. . . . This cooling capacity is of
importance because the propellants themselves must probably
be used to cool the engine instead of having a special coolant
dissipate heat across combustion chamber and nozzle walls to
the outside air. As a rule, the cryogens (liquid hydrogen,
liquid oxygen, liquid nitrogen) are unsuitable for wall cooling
since they boil off under the pressure and temperature
conditions within the tank and do not absorb heat prior to
evaporation.
According to the notes of his later Vienna log
book, Sanger's first designs for a combustion chamber
and his preliminary practical experiments date
back to 1932, the year in which he also started to
lecture on this subject at the Technical University
in Vienna.
The oldest of Sanger's still-existing test logs dates
from December 1932. With a welding torch Sanger
spot heated the 3-mm-thick steel wall of a cylindrical
container filled with water and recorded the
following: "The wall becomes red hot; a layer of
steam forms at the hot spot and displaces the water;
afterwards, the wall melts very quickly."
In this Vienna log book one of the first sketches,
dating from 3 January 1933 bears the designation
"Basic Project." It depicts a simple conical nozzle
with a small opening angle (about 8°), an extended
exhaust, and double-path cooling. The portions of
the engine steel jacket exposed to combustion gases
are lined with magnesium oxide. Also provided is a
jacket for dynamic cooling by means of a propellant
which is pumped from the tank through the cooling
jacket—in counter flow to the exhaust gases—into
the injector. Altogether, the proposal combines
capacity cooling by a ceramic liner with a high
melting point and regenerative surface cooling.
Since his primary duties were as assistant at the
Institute for Materials Research, it is understandable
that in the beginning Sanger was preoccupied
by materials testing, especially by screening potential
structural and heat-resistant materials for the
rocket engine. Up to February 1933, after his first
test firings with chamber walls of steel and static
water cooling had been unsatisfactory, he exposed
plates, or pipes of electrode graphite, thorium
oxide, tungsten, and magnesium oxide to flames of
a welding torch. During all these tests he studied
with special interest the effect of oxygen-rich combustion
and the rate of dissociation of the welding
flame.
For a few months after 3 February 1933, there are
no notes in the log book, only blank but numbered
pages. It is not clear whether the experiments were
interrupted due to other commitments—such as the
publication of Raketenflugtechnik—or whether
test logs from this period were lost.
During this time, the only known direct contact
between the Berlin and the Vienna group occurred.