Re: Re: New Igniter Project Update

On Wednesday, May 12, 2004, at 02:07 PM, John Carmack wrote:
> One comment :
>
> "From what we've seen so far, most of them run from $200+, and they 
> also are mostly designed for very low outlet pressures (<150psi). "
>
> I would suggest that designing experimental rockets for 150 psi feed 
> pressures is a good idea.  Lots of industrial stuff is designed for 
> 150 psi working pressure, and you can save a lot of money over going 
> to higher pressure stuff.  You only wind up with a 2:1 expansion ratio 
> or so, but all the other rocket lessons are going to be the same, and 
> if anything does pop, it will be a less violent pop...

I'm increasingly coming around to this point of view.  Do the absolute 
simplest thing, forget the chimera of 'performance'.  If I was starting 
from scratch I'd spec nitrous oxide/Isopropanol, 150 psi feed pressure, 
and a mix ratio that keeps the temperature low enough to use 
radiatively cooled stainless chambers.  Performance would suck, but it 
would be cheap and simple enough to actually get something done.

......Andrew