> Ideally, rocket nozzles are designed so that the flow is optimally 
> expanded over the altitude range (pressure range) it operates in. You 
> can't "have it all".
>
> Jon
> --
> Jon S. Berndt
> Aerospace Engineer
> Houston, TX

If I remember correctly the engine bells of the 1st, 2nd and 3rd stages of 
the Saturn V were quite different shapes to accomodate this.

This is one of the advantages of the aerospike type of engine... It 
effectively uses the atmosphere as the outer wall of the expansion chamber, 
thus it automatically adjusts to external atmospheric pressure.   What a 
great pity the X33 and Venturestar programs were shelved!

Assuming the spacecraft didn't need to enter atmosphere, i.e. it was an 
interplanetary craft, its engines would only need to operate in a vacuum, so 
no adjustment would be required.

Rarius

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