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The Tsu-11 was a primitive,
thermojet-style
jet engine produced in small numbers in
Japan in the closing stages of
World War II. It was principally designed to propel the Japanese
Okha
flying bomb, a
kamikaze weapon.
The Tsu-11 used a four-cylinder inverted inline
Hitachi Hatsukaze Ha 11 piston engine to drive a single-stage,
compressor. A fuel injection system was fitted behind the compressor.
In operation, fuel would be mixed with the compressed air and the
resulting mixture ignited, creating thrust.
The engine was designed to overcome the major shortcoming of the Ohka
Type 11 weapons, that of limited range. The Type 11 was powered by
solid-fuel rocket motors, which provided tremendous acceleration, but had
a very short burn time. The upshot of this was that the Ohka's carrier
aircraft would have to fly very close to the target, making it vulnerable
to interception. In practice, most Ohka-carrying bombers were shot down
before they ever had the opportunity to launch their weapons. It was
reasoned that a jet engine would provide high speed as well as enough
range to keep the carrier plane safe long enough to release the Ohka and
leave the area.
The engine was first tested hung underneath a
Yokosuka P1Y bomber sometime in
1944 and was deemed successful enough to order into production. The
Ohka was adapted to accomodate the engine in a lengthened fuselage with
jet intakes added at the sides. This configuration was designated Ohka
Type 22. The Tsu-11 was also selected to power the
Yokosuka MXY-9 Shuka ("Autumn Fire") - a trainer intended to
prepare pilots for the
Mitsubishi J8M rocket-powered interceptor. Neither of these aircraft
entered service, however, as their development took place too late in the
war.
A single example of a Tsu-11 engine exists, preserved at the
National Air and Space Museum in
Washington DC. In
1997 it was installed in the museum's Ohka 22 during its restoration.
Engineering analysis of the engine during the restoration process
suggested that the fuel injection and combustion probably contributed
little to the power of the engine, with most of the thrust actually being
produced by the compressor - in effect, a
ducted fan engine.
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