FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

94 SMITHSONIAN ANNALS OF FLIGHT
FIGURE 3.—The ORM rocket engine was designed and tested
on the stand in 1931.
The propellant components were pressure-fed
from the tanks by compressed nitrogen. The engine
was tested with the nozzle directed upwards.
The ORM-1 had 93 parts.
Experimental piston-type propellant pumps
driven by gases bled from the combustion chamber
were designed and tested in 1931-32.
In 1932, Department II of the GDL designed
and tested experimental engines from ORM-4
through ORM-22 to find the best type of ignition,
methods of start-up, and mixing systems for various
propellant components. When these engines underwent
static tests in 1932, the oxidizers used were
liquid oxygen, nitrogen tetroxide, nitric acid, and
nitrogen tetroxide dissolved in nitric acid; the fuels
were gasoline, benzene, toluene, and kerosene.
The ORM-4, ORM-5, ORM-8, ORM-9, and
ORM-12 engines underwent several score of firing
tests. With the pressure in the combustion chamber
up to 50 atm (gauge), the engines were run for up
to one minute. Spark plugs and pyrotechnical ignition
were used. The internal diameter of the cylindrical
steel combustion chambers of the ORM-4
through ORM-8 engines was 40 mm. The combustion
chamber of the ORM-9 engine had an internal
diameter and height of 90 mm and a thermal
ceramic lining 10 mm thick (zirconium dioxide or
magnesium oxide with soluble glass). Its nozzle, 15
mm in diameter, was plated with an 8-mm layer
of red copper. The combustion chamber and nozzle
in the ORM-12, of the same dimensions as those in
the ORM-9, were copper-plated.
So that the best method for supplying propellant
components could be selected, various types of injectors
were tested in the engines: the ORM-4 engine
was provided with spray injectors, the ORM-5
with spray-split type, and the ORM-8 with split
injectors.
In the ORM-9 engine the split injector was located
in the combustion chamber head opposite the
nozzle (see Figure 4). In the ORM-11, it was placed
on the wall of the cylindrical combustion chamber.
The ORM-12 engine already featured two separate
swirl injectors, one for oxidizer and the other
for fuel. The injectors, provided with non-return
valves, were arranged opposite each other on the
wall of the cylindrical combustion chamber (see
Figure 5).
The ORM-16 engine had swirl injectors of a
more advanced design.