Scram uses?

Richard Schumacher wrote in message ...
I was about to write "cruise missle", but hell: why would the military want a
vehicle whose propellant is extraordinarily difficult to store?

Any military scramjet powered missile would probably use hydrocarbon
propellants. Sure, that doesn't work yet, but until recently,
hydrogen propellants didn't work either. I'd imagine that at least
some, and possibly lots, of the information from hydrogen scramjets,
will be applicable to hydrocarbon fuels.

It certainly doesn't make any sense as part of an orbital launcher or vehicle.

Orbital vehicle, probably not. Long-distance cruise vehicle, it
might.

-jake

Jake McGuire wrote:

Richard Schumacher wrote in message ...
I was about to write "cruise missle", but hell: why would the military want a
vehicle whose propellant is extraordinarily difficult to store?

Any military scramjet powered missile would probably use hydrocarbon
propellants. Sure, that doesn't work yet, but until recently,
hydrogen propellants didn't work either.

The engine geometry until recently didn't work, but at least it was clear that hydrogen can sustain a
sufficiently rapid flame front. Hydrocarbons don't, which eventually will drive the fanatics toward that
other old money-sink day-dream, pulse-detonation engines. It's an admirable scheme: scramjet
investigations can be milked for another eight years or so before it becomes obvious to Congress that
scramjets will never be practical for anything, and then the investigators can start asking for funding
for PDE work...

Richard Schumacher wrote:

The engine geometry until recently didn't work, but at least it was clear that hydrogen can sustain a
sufficiently rapid flame front. Hydrocarbons don't, which eventually will drive the fanatics toward that
other old money-sink day-dream, pulse-detonation engines.

Or toward on-board reforming of the hydrocarbons into things like CO, H2, and acetylene.

Paul

Richard Schumacher wrote in message ...
Jake McGuire wrote:
Any military scramjet powered missile would probably use hydrocarbon
propellants. Sure, that doesn't work yet, but until recently,
hydrogen propellants didn't work either.

The engine geometry until recently didn't work, but at least it was clear that hydrogen can sustain a
sufficiently rapid flame front. Hydrocarbons don't,

Please read this press release:

http://www.pratt-whitney.com/pr_062003.asp

... and then choose one of the following options.

[ ] 1. Hydrocarbons cannot sustain a sufficiently rapid flame front
to allow scramjets to work.

[ ] 2. Pratt and Whitney is being untruthful or otherwise misleading.

[ ] 3. I was incorrect.

I agree that scramjets are useless (or worse than useless) for cheap
access to space. So for the purpose of sci.scpace.*, they're
off-topic. They're certainly hard to make work. But three years ago
Henry Spencer could quite accurately point out that scramjets were
vaporware, and that they hadn't produced positive thrust in flight
after decades of trying.

That's no longer the case. Now it's only one instance of net positive
thrust, but when the third X-43A flies it'll be two, and if/when HyFly
flies late this year or early next it'll be three (this time with
hydrocarbon fuels), then four, and so on.

To steal a page from many SSTO supporters of yore, who stole it from
Arthur C. Clarke, we've moved beyond "It's impossible" to "Of course
you can do it, but why bother?" Next up: "I said it was a good idea
all along."

-jake

"Paul F. Dietz" wrote:

Richard Schumacher wrote:

The engine geometry until recently didn't work, but at least it was clear that hydrogen can sustain a
sufficiently rapid flame front. Hydrocarbons don't, which eventually will drive the fanatics toward that
other old money-sink day-dream, pulse-detonation engines.

Or toward on-board reforming of the hydrocarbons into things like CO, H2, and acetylene.

You devil, you :_ A way to make the vehicle even *more* difficult and expensive! Yes, the fans probably will
try that tack.

Richard Schumacher wrote:

... It's an admirable scheme: scramjet
investigations can be milked for another eight years or so before it becomes obvious to Congress that
scramjets will never be practical for anything, and then the investigators can start asking for funding
for PDE work...

A lot of people seem to share your opinion. Me, I like to work with
empirical data.

So far as I've been able to discern, we know rather little about the recent
test:
- the Hyper-X booster rocket works well
- the X-43A guidance system works
- the X-43A engine burns fuel at Mach 7

What I can't find anywhere is any indication of thrust. Did that engine
generate any appreciable amount of thrust? Enough to overcome Mach 5 drag
and actually accelerate?

If anyone has any such hard data, I'd love to hear about it.

/kenw
Ken Wallewein
K&M Systems Integration
Phone (403)274-7848
Fax (403)275-4535

www.kmsi.net

Richard Schumacher wrote:

Or toward on-board reforming of the hydrocarbons into things like CO, H2, and acetylene.


You devil, you :_ A way to make the vehicle even *more* difficult and expensive! Yes, the fans probably will
try that tack.

You *do* know that endothermic reforming of JP-7 has already been
done in ground tests of scramjets, right? The fuel was reformed in
a separate processor, not the engine itself, but the principle
is the same.

Paul

wrote in :

What I can't find anywhere is any indication of thrust. Did that
engine generate any appreciable amount of thrust? Enough to overcome
Mach 5 drag and actually accelerate?

If anyone has any such hard data, I'd love to hear about it.

http://www.aviationnow.com/avnow/new...id=news/04054w
na.xml

"Officials said the 12-ft.-long X-43A produced enough net thrust in the
Mar. 27 flight that it was accelerating while in a slight climb at Mach 7
and 100,000 ft. altitude."
--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Jake McGuire wrote:

To steal a page from many SSTO supporters of yore, who stole it from
Arthur C. Clarke, we've moved beyond "It's impossible" to "Of course
you can do it, but why bother?" Next up: "I said it was a good idea
all along."

-jake


True enough. On the other hand, steam powered aircraft never made it
past assertion two.

--

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