by Ernest B.
When the first
commercial jet came into service in the late 1950s, jet engine exhaust nozzles
had a funny look. It appeared as if small diameter pipes were coming out. The
purpose was, obviously, to reduce the noise of the engine exhaust.
Moving on to
the early 1970s, I was the product integrity engineer for the Viking lander
terminal engine program. The nozzle for this unprecedented throttling 600 lbf
Hydrazine engine was designed by aerodynamic engineers to minimize nozzle
exhaust effects (velocity) on the Martian landing site. After extensive testing
at White Sands, in chambers that simulated the Mars’ atmosphere, the resultant
engine had 18 small nozzles.
The engine was
built at Rocket Research Corporation (RRC) in Redmond, Washington, and much of
the testing was done there. I’d go by the sea-level test cell when the engine
was running, and you could hardly hear the exhaust noise. At this time, RRC was
developing a 300 lbf engine with a single large nozzle for another customer.
One day, I happened to go by the test cell when this engine was running. It
made so much noise that the ground would shake.
This gave me an
appreciation of the effectiveness of the original jet engine nozzles to reduce
noise. By lowering the exhaust velocity, you lowered the exhaust noise.
A companion
development was the creation of purified Hydrazine to eliminate carbonateous
compounds (contamination) that could be deposited on the surface of Mars. This
propellant eventually became the industry standard for monopropellant Hydrazine
propulsion system and has been used most recently on the Phoenix and Curiosity
landers.
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| Viking Lander Terminal Descent Rocket Engine |
