FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

182 SMITHSONIAN ANNALS OF FLIGHT
crease greatly the maximum flight velocity at a required
moment. Besides, it was advantageous to use
the ramjet as an auxiliary engine because it did not
require special fuel supplies such as were necessary,
for example, for a liquid rocket engine, but could
use the same gasoline as the main engine did.
In August 1939, a prototype airborne ramjet
(auxiliary engine DM-1, intended for ground tests)
was designed and manufactured. The engine diameter
was 240 mm. Bench tests of this engine were
performed in September 1939.
A successful testing of the DM-1 permitted its
manufacture to be undertaken for on-board installation,
and in September 1939, three DM-2 auxiliary
engines were built.
Burnout of the thrust chamber of the auxiliary
engine was prevented by a special cooling system,
the gasoline entering the engine being used as a
cooling liquid. Burning stability of the gasoline in
the combustion chamber was achieved by a special
device, the so-called protective ring, within the
chamber. These protective rings formed small
regions within the chamber in which the air flow
had low velocities. In these protected regions (precombustion
chambers) the ignition and smooth
burning of a small quantity of gasoline took place.
The flame that escaped the protective rings propagated
burning through the main mass of the airgasoline
mixture. To assure ignition within the
temperature range from —60° to -f 60 °C and multiple
starts in flight at any velocities, a special
electrical ignition device was designed which was
used throughout all flights.
DM-2 engines were very compact. Their length
was 1500 mm, maximum diameter was 400 mm,
nozzle exit diameter was 300 mm, and the weight
of one engine without the engine frame was 12 kg
and with the frame, 19 kg.
To investigate operation of the ramjet before
flight tests the AT-1 special tunnel was built (after
some modification it was designated the AT-2).
Maximum air-flow velocity within its working section
was 75 m/sec. The test of the auxiliary engines
first in the AT-1 tunnel and then in the AT-2 verified
their safe operation, and permitted the development
of an ignition device and a smooth burning
process, as well as the determination of the main
ramjet parameters. These tests were carried out
throughout the whole period of the DM development,
both to check the structural improvements
made during the tests and to monitor the engine
operation and its condition.
Test of two DM-2 models began in October,
1939, and on 22 October 1939, official tests of the
DM-2 in a tunnel were performed. The results of
these tests were summarized in a statement which
said:
During the tests the engine was started three times. The
controls functioned well. The engine appeared to be completely
reliable and explosion-proof.
During the engine tunnel test the air flow developed a
velocity of 120 km/hr. At this velocity the engine thrust was
about 10 kg which corresponded to designed values. 7
After successful wind tunnel tests of the ramjet
engines, they were installed in the aircraft shown
in Figure 3 for testing in flight.
During these first ramjet engine tests the aircraft
where those engines were installed was essentially a
flying laboratory for the investigation of ramjet
operation.
To protect the fuselage and the tail from the possible
effect of DM engine combustion products, the
I-15-bis tail was covered with sheet duralumin before
the tests.
Flight tests of the I-15-bis aircraft with two ramjets
as auxiliary engines installed under the wings
began in December 1939. The first ramjet aircraft
was tested by test-pilot Petr Yermolayevich Loginov.
The flights performed by P.Ye. Loginov in December
1939, were the world's first made in a ramjet
aircraft. It is interesting to note that the first
flight of a foreign semijet aircraft, constructed by
the Italian Caproni Company's Campini project
and widely publicized by the press abroad, did
not take place until August. This was seven months
later than the flight of the I-15-bis ramjet aircraft.
Pilot Loginov's conclusions about the operation
of jets constructed by LA. Merkulov:
1. The engines provide some marked velocity increment of
the 1-152 aircraft.
2. The engine operation control is simple and readily done
(one handle with a switch).
3. The engine operation is smooth at any speed and with a
protective metal sheathing on the underside of the aircraft's
wing, it is fireproof.
In all, the I-15-bis aircraft with the DM-2-type
ramjets, piloted by different airmen, made 54 flights.
Cut-in of the DM-2 increased the aircraft velocity
an average of 18-20 km/hr. Tests were performed at
flight velocities of 320-340 km/hr. The DM-2 had