Scramjets !!!! It works

> From: Omar E. Vega [mailto:oevega@...]

> I don't believe so, John. I think that if the guys develop a motor
> that is able to work as a jet engine, then the whole matter of
> sending loads to the space will become more easy than today.
>
> I see the following advantages:
>
> (1) There is a large saving in fuel. In an important part of the path
> the motor consumes oxygen from the atmosphere.
>
> (2) In the future a 3-phases scramjet could start firing as a rocket,
> switch to scramjet mode in the critical part of the path and back to
> rocket again when it leaves the atmosphere. If that is done, the
> savings in engine hardware and load will be very large indeed.
>
> (3) If things goes well, that kind of motors could be used in regular
> hypersonic planes for hurried executives. So, they could be mass
> produced (the motors, not the executives :) ). Making the cost of
> going up there a lot cheaper.

As I said, if it was purely a matter of speed then we'd all be using mass
drivers. But it isn't a matter of speed! It's a matter of going at that
speed _through_the_atmosphere_ for a prolonged period of time. The problems
of building a mach25 scram-jet pale in comparison with the problems of
building a ship that can withstand the heat long enough to get to those
speeds in the first place!

There are reasons rockets go up and then sideways, and not the other way
round as the spaceplane concept requires.

> From: Dave Logsdon [mailto:templar@...]
> There *are* reasons to favour some of the newer approaches.
> The first is that a Scramjet first stage can provide
> Cheaper Access To Space (CATS)

How? How can a technology that requires decades of expensive research before
it's up to the job and breakthroughs in material science before it's even
practical possibly be cheaper in the near term than a proven technology with
a wide technology base whose principles are widely understood?

> ELV vs. RLV

RLV has nothing to do with space planes. The X-43 is a spaceplane. It ain't
reusable though. The DC-X would not have been a spaceplane, but it would
have been reuseable.

> The cryogenic fuels used in the rockets you favour

And what will be powering your scram-jets if not highly explosive cryogenic
fuel? Fairy dust?

Challanger blew up because it was deliberately flown well outside of it's
operational envelope. You'd get exactly the same result if you tried to make
a 747 do a loop-the-loop. The only thing the hydrogen did was make the
fireworks a little prettier. The columbia broke up because of a string of
very stupid management decisions, going back to the basic design of the STS
shuttle. Please note that the shuttle is the ONLY rocket where the heat
shield, or any part of the payload, can be damaged by falling debris.

You can't fairly use the shuittle as a rocket case study because it is so
unique, and because it so uniquely badly designed. Though the same can't be
said when comapiring it to the space planes you seem to favour. For
instance, how you you incorporate an escape system into the design? What
happens when you try and take off from a French airport and one of your
wheels throws a piece of jagged metal up against the TPS? Or the tire
explodes and you're hurtling down the runway at hundreds of miles per hour?
What happens when one of your beyond bleeding edge engines goes wrong and
the fuel catches fire just before rotation?

I also agree that ELVs should be replaced. I'm just more inclined to the
TSTO VTOL RLV, instead of the SSTO HTOL RLV, as simplier, cheaper and more
likely to succeed. Space planes are potentially very useful, but they are
not the universal solution to a simple problem - as people sometimes claim
they are.

John