Re: Mojave airport is not a spaceport

From: Earl Colby Pottinger (earlcp_at_idirect.com)
Date: 06/25/04 

Date: Fri, 25 Jun 2004 12:30:29 -0500

"Pete Lynn" <pete@peterlynnkites.com> :

> "johnhare" <johnhare@tampabay.rr.com> wrote in message
> news:QzbCc.1614$lL2.139538@twister.tampabay.rr.com...
> >
> > I may be in disagreement with you about the nearly SSTO
> > performance requirement. MR for SSTO seems to be about 16
> > (Lox/Kero) from the ground, and 10 from the vacuum altitude
> > you deliver to. Going from 6.25% dry mass including payload to
> > 10% dry mass including payload is a major gain in margins. Even
> > without the mass savings on lighter engine and tank mass
> > percentage, 37.5% of the upper stage dry mass becomes
> > available to increase payload. I was convinced several years
> > ago by Len Cormiers' Space Van booster concepts.
>
> Me too, assisted SSTO where you stage just above the atmosphere such
> that your lower stage can still easily return to the launch site, (this
> is critical), seems like such an ideal way of doing things. These are
> two very different regimes prompting two very different optimal
> solutions. Trying to do it all in one SSTO will just result in a
> compromised design, which does not really gain you anything.

However, Henry Spencer has a good point when he said that first you should
try to make a SSTO first. The closer you get to SSTO the better for the
payload of a boosted design. Beside, trying for a SSTO forces you to look a
designs and ideas that you might skip over if you start designing a TSTO in
the first place.

> If there was such a cheap reusable assist stage commercially available,
> then even very small orbital vehicles, (less than 100kg), could be
> developed at almost the hobbyist level. There would no longer be an
> aerodynamically imposed small scale limit on orbital vehicles.
> Development of small orbital vehicles could be directly within the means
> of individuals, a very low cost Prize on that basis could be real
> interesting.

At that point I really expect the paper work to cost more and weigh more that
the orbital craft :)

> There are a number of different approaches to the assist stage. I have
> come to quite dislike the straight aircraft approach, not to deride
> Scaled Composites, (they are getting the results), but I suspect it has
> cost them 5-10 times as much as it should. This is telling, they used
> to be the pin up boys of low cost development, but were they really? I
> fear that they opted for the design that they did not because it was the
> right one, but because it was the only one they knew how to make.

In thier defense, it is usually best to do what you know best, and second
they probably designed, builted, and debugged White Knight for less money
than NASA would have paid to rent, modify, demodify a commercial plane.
Compared to where we want to go they were not low cost, compared to where we
are coming from in the past. They were very low cost.
 
> One of the things that I am greatly impressed with Armadillo over, in
> addition to their proper low cost development approach, is their pure
> nothing but rocket mentality. This keeps weights and costs low,
> especially during development, optional extras that provide greater
> efficiency at greater complexity can come later when the market is ready
> to pay for it.

Agreed. Not just weighs and costs. The software modelling was simpler,
modifing the design was also easier IE the switch from four rockets to one.
Plus the need of only a pad of concrete/packed soil mean testing can be moved
very easyily.

> In the long term the straight VTVL rocket assist stage will be very fuel
> hungry, gravity losses dominate so this probably favours aerodynamic
> augmentation. I do still quite like VTVL, speed is useful and the white
> knight takes something like an hour to get to height, and not very high
> at that. I suspect that we need to go much higher than subsonic air
> breathing engines allows. Although I expect the assist stage might
> fully aerodynamically shield the upper stage, supersonic aerodynamic
> vehicles tend to cost, I am unsure of this approach.

I don't agree unless you are only talking about a craft to lift hobbist
designs, if only them then yes I agree.

> So we have the pure VTVL rocket and I am guessing you are favoring this
> type of VTVL vehicle that instead uses your very high T/W air breathing
> engine

In real life there are no very high T/W air breathing engines

> and perhaps goes supersonic, the more I think about this, the
> more I like it, no wings. This might almost reach a 100km, can you do
> it? I suppose I still favour what is effectively a very refined rocket
> powered paraglider. This is probably still the cheapest to develop and
> operate in the short term, but it is a bit slow and limited in height.
> I will continue to investigate various more refined hybrid type
> solutions that might overcome some of these weaknesses, I am less sure
> of this than I used to be, assuming you can do it.

A pure rocket design is always simpler. May not be cheaper, but it is
simpler and thus less likely to have a bad design error hidden away somewhere.

> > I think our goals might be similar with a slight difference in
> > methods and means :-), not to mention real world experience. I
> > hope to start closing the gap on the last two real soon now, same
> > as I did last year, and the year before that....

> And me too. :-)

The more ways tried the better. NO-ONE but no-one really knows what the bet
methods are yet.

> I am making some progress on the tethered wing thing, though initial
> commercialization will be elsewhere, (where the money is). I am hoping
> that maybe five years from now I will be able to make one for rocket
> landing. Hopefully for around 1% landing weight I can build one that
> provides a glide rate of around five, if desired, with soft vertical
> landing, perhaps without the need for any landing gear. This should be
> lighter than any of the alternatives, it could also be easily powered.
>
> Pete.

Good Luck. URL?

                Earl Colby Pottinger 

-- 
I make public email sent to me!  Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC.  What happened to
the time? http://webhome.idirect.com/~earlcp

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