Re: Re: New Igniter Project Update

At 02:43 PM 5/12/2004 -0400, you wrote:

>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

Well, you can't get nitrous down to 150 psi feed pressure unless you 
refrigerate it, so you might be stuck with high pressure there.

Getting the mix down to using a radiatively cooled stainless chamber would 
require an extremely rich mixture, and you probably wouldn't know if you 
had it right until you melted through a chamber.  A big hunk of copper heat 
sink is probably a better idea.

John Carmack