Re: rutans roton, again

Michael S. Lorrey (
Thu, 07 Jan 1999 12:00:55 -0500

Steve VanSickle wrote:

> On Wed, 6 Jan 1999, Spike Jones wrote:
> <snip>
> > this is the critical statement on the whole site. my task, before
> > i start buying roton stock, is in determining exactly what the
> > comment means. if it means an empty roton is 5% heavier than
> > an empty atlas, while holding 24% more fuel by mass (the only
> > logical interpretation of the statement) well, then im impressed.
> > i grant that it is possible, since a kerosene tank is much smaller
> > and lighter than a tank that could hold an equal mass of liquid
> > hydrogen.
> Atlas did not use liquid was Kerosene/Lox like the Roton is.
> Roton saves empty mass by widespread use of advanced composites instead
> of the stainless steel the Atlas body/tank was made of. And Roton stock
> is not available to the public (unless you have several hundred thousand
> you want to invest to make it worth their while to push it through the
> SEC). I think there may be an IPO after testing.

Actually, you don't need to invest that much, you just have to have a minimum net worth to qualify for a level of investment in such private stock instruments. There are several net worth thresholds for different levels of capitalization. I don't have copies of the SEC regs on me, but I had dealt with this issue with the startup I was involved in in Seattle earlier this decade. People that meet the threshold requirements (it can be a net worth amount or a gross income amount) are called Qualified Investors. You can also get stock in pre-IPO companies as compensation for work done for them, either as an employee or as a contractor.

> > next i must do the calcs. i have weights of the empty atlas, so
> > from the info given, weight, size and specific thrust (i will assume
> > they really did somehow figure out how to get 350 seconds vac isp
> > out of kerosene and lox with a 400 psi chamber pressure) i can
> > estimate (optimistically) drag coefficients and see if they really do
> > have a chance of getting to orbit that way.
> I thought they were running at higher pressure than that, but I could be
> wrong. Even at higher pressure and aerospike altitude compensation, it
> will be a tough goal. If 350 sec is an average for the whole flight, 9300
> m/s delta-v (which is a good estimate including drag and gravity losses)
> the mass ratio is 15 or so. Even if the averaged specific impulse drops
> to 320, the mass ratio stays under 20.
> > as for using an autogyro reentry system, i have gone even crazier
> > trying to figure out how they could make that happen. every
> > version of that i can imagine would be nowhere near handling
> > the heat load of even a no-payload reentry. at best, i could imagine
> > blades that would deploy very late in the reentry event, after going
> > subsonic. this creates the need for a heatshield, which defeats most
> > of the advantage of the autogyro system in the first place.
> 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.
> There, they will make the vehicle passively stable (so that loss of the
> reaction control system won't result in the vehicle losing control) but
> they won't be spun up for lift until the vehicle slows to sub-sonic. The
> heat sheild they are designing will be water transpiration cooled (think
> of it as an ablative heat shield, where the ablative material is water and
> it's replaced every flight). They expect to use rotors for hypersonic
> lift on later vehicles (both take-off and re-entry) but they now expect to
> have to actively cool them. That is more risk than they want to take on
> for a first generation vehicle.
> > on the other hand, the system could perhaps be made so simple and
> > 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.
> > the whole exercise gives one a new respect for how deep a gravity
> > well we are in down here. spike
> Actually, I've been growing more and more appalled at how the cost and
> difficulty of spaceflight has been over stated over the decades. Only a
> government monopoly would think a disposable spacecraft reasonable (for
> other than the most basic test purposes). But once NASA established the
> status-quo, no one was able to buck it until now. 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.

Has anyone checked on the latest from the various rocketplane companies? Pioneer Rocketplane seemed to be moving along pretty well a while back.

I've also seen some good performance from some amateur projects which are using a peroxide(90%)/tar type solid/liquid hybrid fuel system. This apparently allows a real minimization in the mass of the vehicle, and the solid fuel is really dense, while the high concentrate peroxide is extremely reactive.

I know that Pioneer was looking at a 95% peroxide/JP-4 system earlier. Now they are drifting toward a more conventional oxygen/kerosene system. Mike Lorrey