Re: Multiple engines (was RE: Liquox)

At 05:13 PM 6/10/2004 -0700, you wrote:

> >We are considering an alternate nozzle strategy: lots of little 1" throat
> >nozzles welded between two water jet cut plates.
>
>Why welded between two plates?  Run coolant through it?

So it becomes a honeycomb structure, otherwise you would need a very thick 
top plate.

>I looked a lot at making a lot of little nozzles out
>of a single plate either cast or machined with
>micronozzles across the plate.  Cast inconel plates
>with the nozzles preformed aren't that expensive,
>and can operate at the required temps for many
>of the propellants.  Probably including your
>mixed monoprop.  Stainless is probably even
>good enough for that mixture.

Stainless is fine for our mixed-monoprop, but even inconel doesn't really 
get you up into any bipropellant temperature ranges.  The "superalloys" 
don't have much higher melting points than stainless, they just retain a 
lot more strength at the elevated temperatures.  None of them have any 
usability above about 2200 F.  You need to go to a refractory (columbium, 
molybdenum, etc) to get an uncooled biprop, and even then you need to run 
very low pressure.

John Carmack