Re: What's the latest at RR

Doug Jones (
Thu, 01 Jul 1999 07:32:28 -0700

I ran into some of the gang at the grocery store (hey, Mojave is a *small* town), and the word is, another tiedown test after the 4th of July, and first hover a week or two after that. Wednesdays seem to work out best- prep Monday, fuel up Tuesday, fire/fly Wednesday dawn, analyze results & make changes the rest of the week.

Philip Witham wrote:
> Doug! You're whistling my tune!
> >Doug Jones wrote:
> >Actually, for modest delta-v high acceleration missions,
> Like getting out of this damn gravity well...

Actually, 9000 m/s is *not* a modest delta-V. The effective mass ratio must be in excess of 15, closer to 20 for pressure fed with it's performance penalties. Sometimes I wish we were Martians...

> >Lower pressure engines are easier to regeneratively or ablatively
> >cool, although they have lower performance in the atmosphere. In
> >vaccum, they do as well as higher pressure engines, but are a bit
> >bulky (1/4 pressure needs 2x nozzle diameter for same thrust).
> ...Yes sir! And size is a lesser factor in component and system cost.
> And a really wide second stage nozzle can be a corrugated stainless
> steel cone, wrapped around the first stage. Pc=75PSI!

Spoken like a true Sea Dragon disciple ;) Little parts are a nuisance to spec and manufacture, and tolerances have to be very tight for injector elements... but I know from personal experience that small combustors are convenient to handle. It's nice to just sling a 5,000 lbf thruster over your shoulder and carry it out to the car. 500K engines need a forklift. A large one.

What I'm getting at is that I'm an agnostic on pumped SSTO vs press-fed TSTO.

> >Ignition sequence timing is simpler, since you only have to light
> >the chamber, no preburner or gas generator needed.
> ...And fewer transducers to wire, tubes to bend, fittings to leak,
> control and data acquisition channels to build, less software to
> write, the list goes on.

Preaching to the choir. BTDT.

> >As for barnstorming, there is some very real interest in a flying
> >Me-163 replica... now *that* would be a fun project.
> Hoooboy, the human who could safely fly that would be one steely eyed
> heroic type! Though, I think if you asked for a pilot, you'd get
> 2,000 volunteers.

Actually, the handling characteristics of the Me-163 were quite good, and the thrust/weight ratio is comparable to modern jet fighters. Empty, the approach speed would be quite low. There was a two-seat trainer with retractable gear built during the war, and that's the logical choice for a replica. I wouldn't mind getting a type rating for "rocket fighter"...

Doug Jones, Freelance Rocket Plumber