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From: serre@boulder.Colorado.EDU (SERRE GLENN)
Newsgroups: sci.space,sci.space.shuttle
Subject: Sea Level RL-10s (was Re:  New Shuttle Engines)
Summary: Would need (minor?) mods for startup.
Message-ID: <30004@boulder.Colorado.EDU>
Date: 19 Nov 90 19:47:37 GMT
References: <11236@milton.u.washington.edu> <1990Nov16.211340.27611@zoo.toronto.edu>
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In article <1990Nov16.211340.27611@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
>A badly overexpanded nozzle causes the gas flow to break away from the
>nozzle wall before reaching the end, which causes all manner of nasty
>turbulence and problems of various kinds.  The SSME nozzles are in fact

There is, however, one good effect from separation in an overexpanded nozzle:  
If the flow didn't separate (which it usually does at ~0.4 times ambient)
then the exit pressure would be even lowe, resulting in a greater loss of 
thrust (compared to the separated case).  

>>to adapting the RL-10 to operate at sea level.  Is this a good example of

>In principle, all you need is a shorter nozzle, although you have to think
>about things like the effect on the cooling system.  There may be some
>issues in ignition, too.

Since the RL-10 "bootstraps" on ignition (uses energy from tank pressurization
to spin-up the turbines), you'd have to pressurize the fuel and ox tanks to 
about 20 lbs/in2 over atmospheric (for the Centaur G-prime RL-10s).  I can't
imagine that this would be a problem, though.  

Trivia and ramblings from 


--Glenn Serre
gaserre@nyx.cs.du.edu   (serre@tramp.colorado.edu will disappear soon. :-( )