FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

NUMBER 10 237
2. Use of metals as fuels, either in pure form or as additive
to other fuels.
3. Use of rocket engine combustion gases to drive propellant
feed pumps.
4. Special tubing for building thrust chambers; proper tubing
profiles provide for a smooth inside wall and large
surface areas for cooling.
5. High-speed lox pumps to prevent oxygen evaporation.
6. Manufacture of combustion and thrust chambers by winding
tubes to proper shape.
7. Wall-cooled nozzles characterized by an average divergence
angle larger than 25° and smaller than 27° (shortened
nozzle).
Sanger, in December 1934, published a short report
on his tests and their technical conclusions in
a special edition of the magazine Flug (Flight). In
the following months, he applied for an Austrian
patent on some of his ideas including, on 9 February
1935, a claim for the regenerative forced-flow
cooling of rocket engines. The Austrian patent
144,809, "Raketenmotor und Verfahren zu seinem
Betrieb" (Rocket Engine and Method for its
Operation), reads in part:
The coolant must be carefully ducted around the combustion
chamber through a specially designed cooling jacket so that
a prescribed coolant flow velocity is safely maintained over
the entire combustion chamber wall in order to assure at all
places the required heat transfer and avoid spot heating of
the wall material beyond an allowable limit.
Twelve patent claims followed:
1. Rocket engine with essentially continuous combustion,
characterized by forcing a coolant along walls exposed
to the combustion so that a specified coolant flow velocity
is safely maintained at any given spot of the combustion
chamber wall; the ratio of useful combustion chamber
volume to the throat cross-sectional area ranges from
50 to 5000 cm 3 /cm 2 .
2. Rocket engine according to claim no. I, characterized by
grooves machined into the combustion chamber wall,
which serve as coolant passages and are properly covered
to form a leak proof channel.
3. ... by winding tubes of arbitrary cross-section around
the combustion chamber wall to provide coolant passages.
4. . by joining together tubing of any chosen crosssection
to form coolant passages with the combustion
chamber wall; the tubes to be properly connected to
each other.
5. ... by providing for the combustion chamber wall tubes
of such cross-section that joining them together results,
without trouble, in a properly shaped, smooth wall surface
on the combustion side.
6. ... by ducting connections, injection passages, etc., into
the combustion chamber between the cooling channels in
such a way that no uncooled material concentrations
occur.
7. . by keeping the coolant along its flow path entirely
or partly under increased pressure.
8. ... by reducing to a desired level the amount of combustion-gas
heat radiation to the wall through properly
heat-reflecting wall surfaces.
9. ... by applying improved wear-resistant coatings to
chamber wall areas subject to wear by impinging combustion
gases.
10. ... by exploiting the wall-to-coolant heat flux for preheating
the propellant prior to injection into the combustion
chamber.
11. ... by actually using the propellants (i.e., fuel, lox, etc.)
partly or entirely as coolants.
12. ... by adding to the propellants suitable ingredients,
such as catalysts, amylic nitrate, etc., to vary the speed
of combustion.
In addition to this basic patent, many patents of
addition in various countries were granted; among
others, on 11 December 1941, the German patent
DRP 716,175; the Italian patent 334,064; the
French patent 792,596; the British patent 459,924;
and in the United States, patent application USA
Serial 33,516 was filed, but the patent was not
granted, probably due to the war.
Effective 1 February 1936, Sanger accepted a
contract with the Deutsche Versuchsaustalt fur
Luftfahrt (German Research Institute for Aeronautics)
at Berlin-Adlershof that committed him to
prepare plans for the establishment of a Raketentechnisches
Forschungsinstitut (Rocket Research
Institute) and a research program for liquid rocket
propulsion systems. Construction of the institute
began in February 1937 at Trauen near Lueneburg.
Sanger was able to continue his Viennese tests on
a larger scale only after he had moved to Fassberg,
near Trauen, on 25 August 1937, and after the
"most vital" parts of his new test facility had been
completed. This actually happened after the 1926-
36 period that was to be covered by this report.
Nevertheless, a short historical summary of the
later investigations, as far as they concern the completion
of his cooling method developed in Vienna,
will be presented on the following pages.
On 25 October 1938, prior to resuming his test
runs and based on his experience with vapor coolants
dating from 9 May 1934, Sanger applied for a
patent on an improved, closed regenerative coolant
loop using supplemental coolants. In the main
process fuel and lox are separately forced by highpressure
pumps through the injector into the combustion
chamber, where they burn together and
then expand across the nozzle and gain exhaust
velocity. The supplemental cooling process handles