Re: rutans roton, again

Steve VanSickle (
Fri, 8 Jan 1999 10:11:43 -0600 (CST)

On Thu, 7 Jan 1999, Spike Jones wrote:

>> If 350 sec is an average for the whole flight,

> well, not down low. thats surely their vacuum isp. i would be interested
> in the isp profile, given aerospike altitude compensation.

Me too. You're right...350 averaged is probably high.

> > The rotor blades will deploy upward before reentry (like an umbrella blown
> > inside-out) and stay in the lee of the shock way, minimizing heating.
> steve i remain skeptical on this scheme.

Seems like it ought to still get a bit warm to me, too. However, they *are* doing extensive computational aerodynamics and are relying heavily on hypersonic rotor wind tunnel work that NASA did in the 60's. Amazing all the stuff gathering dust in their libraries.

> > > so cheap it would not be so critical to recover anything.
> >
> > Doubtful. True land that sucker, fuel it up, kick the tires and fly again
> > reusability is the only way they will be able to take on the big boys.
> well pardner, the old land, fuel and fly scenario is most probably
> not doable with single stage to orbit. its asking too much. but there
> are many interrim technologies, even with throwaway hardware that
> could stomp the big boys flat. our modern launchers all require standing
> armies at staggering costs. if we managed to get a design that is way
> simple, we could throw the stuff away every shot and *still* be waaay
> cheaper than a recoverable system that requires hundreds of full timers.

Watch me back-peddle... Wouldn't take much to build a simplified expendable that could beat the big guys in a fair contest. But I'm not sure you would get a fair contest. I think you need something overwhelming superior and difficult for them to duplicate to survive the economic/legal/political power they can bring to bear. Don't get me wrong, I'm not talking secret conspiracies...just good old fashioned hardball.

> > I think Rotary will
> > pull it off, if they have the financial ability to weather the loss of one
> > or two vehicles during testing. A lot of "rocket scientists" will have a
> > lot of explaining to do.
> ya, ill be one of em.

Oh, no! I didn't mean you! All those *other* rocket scientists <grin>.

> consider this tho: i have a version of a roton,
> been making sketches and calcs for a few months now. it is a two
> stage, both rotary, with no recoverables *but* it is verrry simple.
> given economies of scale, the parts could be mass produced and
> still beat up on the big boys. my version has lox/methane first stage
> and lox/hydrogen second. i am trying to calculate my way out of
> liquid hydrogen for the second stage, as it introduces so many handling
> difficulties, but i give away a lot of performance without it. i fear
> even my 9500 m/s delta v is a bit optimistic.

But doesn't the concept more or less require the fuel and oxydizer to be closely matched in density? That's one of reasons they use kerosene, and also one reason they use LOX for engine cooling (the pressure drop through the cooling system brings it to the same pressure as the less dense kerosene). Wouldn't there be a 10 to 1 pressure difference with the LOX and hydrogen?

> i tried to make it work with no despun section, but couldnt figure out
> how to guide the turn, so, i end up with a despun platform forward
> that holds the payload. problem im having is that the cross sectional
> area is large, so i lose an awful lot to drag. i wonder if i could get
> a mountain top launch site? a high one could get me out of half
> the atmosphere. the environmental types wouldnt like it tho. spike

Is it because the low denity fuel requires a large diameter? Higher density fuel can make it much more compact. And I would think that rotating the feul tanks are more trouble than they are worth...slow, low pressure rotating seals aren't *that* hard.