At 11:25 AM 7/31/02 -0700, Bill Clawson wrote:
>But what about the contention that bigger engines are typically more
>efficient (higher Isp)? I'm not arguing for or against multiple cat packs,
>but about the size of engines in general.
All other things being equal, that's more or less true. It's not
particularly hard to understand why -- a larger engine will have
proportionately less volume close to the walls, as opposed to a smaller
engine. Since many of the losses in a rocket engine are in the boundary
region, this leads to a small loss in efficiency for a smaller engine, all
other things being equal. However, this only becomes a big deal for small
rocket engines (like less than 1000 lbs thrust). Between an engine of
10,000 lbs thrust and one of 100,000 lbs thrust it's a fraction of a percent.
That said, smaller rocket engines are *MUCH* easier to design,
build, and test, which should balance out any fractional losses in
efficiency from being smaller.
-p
_______________________________________________
ERPS-list mailing list
[EMAIL PROTECTED]
http://lists.erps.org/mailman/listinfo/erps-list
