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.
|Viking Lander Terminal Descent Rocket Engine|