MD11Engineer From Germany, joined Oct 2003, 13336 posts, RR: 64 Reply 1, posted (8 years 4 months 3 weeks 5 hours ago) and read 2755 times:
Most rocket exhaust nozzles are Laval nozzles (Laval, Swedish 19th century engineeer, invented and first used this type of nozzles in steam turbines).
The idea of any nozzle is to convert potential energy of a gas (pressure) into kinetic energy, e.g. give the gas a velocity as high as possible.
Laval nozzles work on the principle that the throat area dimensions let the gas at a given combustor pressure reach the speed of sound in the throat. The cone behind is dimensioned, that the gas will expand further and exceed the speed of sound. The shape of the cone (the angle of the opening) is mostly determined by the pressure difference between the throat and ambient. As a result, rocket nozzles used within the atmosphere tend to be narrower than those used in a vacuum.
Lehpron From United States of America, joined Jul 2001, 7028 posts, RR: 22 Reply 4, posted (8 years 3 months 2 weeks 1 day 2 hours ago) and read 2263 times:
Follow-up question: Usually a hot gas come out of a rocket nozzle so the shape is due to pressure (thank you MD11Engineer)
What is the exhaust is a plasma? It's hot enough to be ionic and thus would need to be controled by magetic solenoid fields, but is there a pressure difference to cause a need for a traditionally shaped rocket nozzle? Or is the solenoid shaped that way?
BTW, I'm watching October Sky right now -- never seen it and have no prejudgements -- this should be interesting.
My friend who let me borrow the disk asked me how I can be into SciFi movies like Stargate, Event Horizon, Contact, etc and still be in aeronautical engineering rather than astronautical. I don't know what to tell him.
Guilty pleasure I guess.
The meaning of life is curiosity; we were put on this planet to explore opportunities.