Scramjets !!!! It works

From: ANTIcarrot [mailto:dante.feditech@...]

"But not an orbital RLV though. I've also yet to see a design for a launch
vehicle with a hybrid engine. Not that I'm saying that it's impossible ..."

That's my point. Not yet, but not impossible. That's why I believe hybrid
fuel systems should be used now, for anything they are currently capable of.
First, because they're cheaper to build, cheaper to operate, and safer.
Second, because using what they're able to do now supports the R&D to create
better, possibly orbit-capable hybrid fuel systems.

RE: Challenger: "I put it to you that if your biggest engine rips loose and
damages the super-structure at high speed, you're screwed no matter what
design you use. ;) "

Well, maybe it's the way you described it. Or maybe, the SRB failure
detonated the *explosive* fuel in the ET, but if the fuel for the SSMEs
hadn't been explosive, the pilot *might* have had a few extra seconds to
initiate SRB separation, and try for an emergency landing. Might have.
Maybe. Hey, I've had enough close calls in my life that I'll always take a
slim chance over none at all.

"The only reason the tank has insulation in the first place is because if it
didn't, ice might form and fall off during launch, damaging the shuttle's
heatshield. Spot the irony. "

Yeah, I spot the irony. Now, would you please spot the point I've been
making? So, why was the insulation there? Because ice might form. And, why
might the ice form? Because of the *cryogenic* fuels! *IF* we can get rid of
cryo-fuels, we eliminate this problem.

"Watch a saturn-v launch sometime. You can see it's covered with ice that
falls off during launch. This was never a serious issue before the shuttle."

Reverting to an old-fashioned, straight-up, single-stack VTOL is, indeed,
*one* way of dealing with the problem. But, is it the *only* way? NO. If
not, is it the *best* way? Well, that's our current discussion.

I posted:
Even if all the safety issues could be addressed, the cost savings alone of
hybrid systems make them worth considering.

"That's like saying, 'Cars crash and are unreliable. We should all start
using bicycles.'"

I don't see how you're relating cost savings to this. If your point was
actually in reference to the safety issue, then I'd say the comparison is
between your fondness for an earlier model, and my preference for a later
model that's less expensive to make, requires much less maintenance, and is
safer to `drive'. No matter if it's cars or spacecraft, anything that's
cheaper *and* safer is an improvement.

I really don't understand what your problem is with the idea of using an
alternate rocket system that costs less, *and* is safer, on the occasions
it's up to the job. Or with promoting this alternate system, in the hope
that it can be developed into something that *might* be able to replace our
current fuel systems for all applications.

"In case of systems failure. Would you really like to tell your astronauts,
"We're pretty sure it's safe, but on the off chance we're wrong you're
completely screwed?"

My analogy was to current, commercial aircraft, that fly *thousands* of
times a day without any need for any escape mechanism. But, if you want to
insist on an evacuation system, then the ejection systems used in some
military aircraft could easily be added to the jet-powered lifter/first
stage, and the orbiter/second stage could be equipped with an ejectable
`survival module', similar to the one in the FB-111.

"Where as VTOL has the advantage of making any patch of concrete anywhere
into a space-port."

You *know* it takes more than a "patch of concrete" to create a spaceport!
On the physical side, you'll need a gantry, a complete cryogenic system to
process your fuel and oxidizer, possibly a VAB, maybe a `crawler' to carry
the assembled ship into position... whatever. As I've mentioned before, HTOL
systems will be able to use the infrastructure already in place for
aircraft. This would save millions for any company starting a private launch
business. Plus you'll have to convince the FAA, the owners of the airport,
and the community gov't, that you should be certified to do what you want.
If you can't get legal certification, you ain't gonna fly. HTOL looks and
sounds like just another aircraft taking off. This isn't a real issue for a
nat'l gov't space program, but for a private company?

"Consider the Harrier and the A-10. Which needs more
concrete? Which has greater flexibility?"

You know as well as anyone reading this that the Harrier uses the same
resources and infrastructure as any other aircraft. The more desperately you
try to dance around the point, the more you prove my side of this.

"Vertical take off is the way every rocket has ever worked."

And your point is?

"The design shapes are very simple. Hence easy to build and maintain."

Hybrid-fueled systems are simpler and cheaper than cryo-fueled systems. HTOL
systems -- aka aircraft -- have been built and maintained longer, and at
lower costs, than any VTOL system.

"Heatshields can be kept small (with only the base being armored) which
allows heavier but more reliable technology... Multiple landing options,
including parasail or powered landing."

This brings up something I've been concerned about re: VTOL systems, but you
might have just addressed it. Just how accurately can your preferred system
park itself where it's needed? Gov'ts can afford to chase all over the place
to recover their space capsules, but private companies can't. An HTOL craft
landing at an airport/spaceport has access to any facilities needed to deal
with it's passengers and cargo. Are VTOL craft able to do this? Roton and
the DC-X were intended to be controllable-descent designs, but the
parachutes all the *successful* VTOL designs have used just drop the capsule
somewhere in the general vicinity of a awfully big `landing site'. Maybe
current VTOL systems can deal with this? How accurately can a parasail land
a capsule?

"Small VTOLs can operate from almost anywhere."

*After* you build the infrastructure to operate from, which can cost
millions per location. HTOL can operate from existing airports, saving
millions in creating said infrastructure. In addition, VTOL can operate
"almost anywhere" only *IF* they're certified and permitted to operate. NASA
and the U.S. military -- and their equivalents in other countries -- do what
they want, wherever they want. But private companies have to answer to the
FAA, OSHA, other Federal agencies, and a host of local bureaucrats and
agencies. Spacecraft that launch like an airplane, and land like an
airplane, are more likely to be thought of as airplanes. This second point
*might not* be an issue, but it strikes me as something that needs to be
looked at.

"They can be sold commercially, because the design doesn't lend itself to
weapons deployment."

Oh, you *GOTTA* be kidding me! What do you call a VTOL suborbital? I call it
an ICBM! The creation of boosters capable of reaching space was originally
created as almost an afterthought to ballistic missile development; the
Redstone, Atlas, and Titan boosters were all originally designed as weapons.

"With very slight modifacations and refueling in orbit, the VTO can go to
Luna, Mars or GEO."

Assuming there would ever be a reason to use the *same* craft for those
missions -- and I make no such assumption. Why would we ever want to try to
create a craft that's supposed to climb in and out of Earth's atmosphere
into the edge of space, and then expect that *same* craft to go voyaging off
somewhere else? Isn't this something like expecting Columbus to slap wheels
onto the side of the Santa Maria, and then hitch up some oxen, to do
somewhat the equivalent of the Lewis and Clark expedition?

"Greater flexibility in positioning the base of operations."

See my infrastructure points above. The `bases of operation' for HTOL
already exist, all over the world.

"Able to land and take off in bad weather."

Aircraft regularly take off and land in weather that grounds rocket
launches.

"Fewer enviromental (sound) problems."

Interesting point. I've never been around for a major rocket launch, so I
can't compare it to the countless aircraft launches I have been near. The
impression I've always had was that rockets were much louder, but if they
do, in fact, require a smaller `sound abatement zone', then this would be a
legitimate point in your favour, *if* you're building a completely new
spaceport. So, *once again*, we're back to my point that HTOL systems will
be able to utilize the infrastructure of *existing* airports, avoiding the
need to build a new, separate, very expensive spaceport.

Dave