Hypersonics Overhype

That's the theme of my latest column at TechCentralStation:

http://www.techcentralstation.com/033104C.html

"Rand Simberg" wrote in message
...
That's the theme of my latest column at TechCentralStation:

http://www.techcentralstation.com/033104C.html


I myself even have doubts about the military applications for the hypersonic
bomber the Air Force is envisioning. The goal is to have almost zero
decision-to- impact time but a hypersonic vehicle can hardly loiter around
and would probably have a huge turning circle travelling at its minimum
speed (mach 5). It would take about 10 minutes to get a bomb on target by
such as bomber after the 'go' was given. This compares unfavourably compared
to a ICBM which can hit any target in the world in 15-20 minutes. A modified
ICBM with a conventional warhead would probably be just as effective.

"Uddo Graaf" wrote...
I myself even have doubts about the military applications for the
hypersonic
bomber the Air Force is envisioning.

Such a bomber might work if it was rocket only. (But would still take an
hour or two to launch.) Or if it was accelerated to M1.0 whilst on a launch
rail, upon which a RAM/SCRAM combined-cycle engine could take over.

Hypersonics have applications for the army. A M7.0 hydra rocket (the pods
used on Apaches) would make a very good anti-tank weapon. Might even be
cheep enough to make the hellfire redundant except for precision strikes. On
second thoughts the US army would probably hate the idea, as such a cheep
and simple weapon would probably make a worthy successor to the RPG-7, which
they are still having troubles with.

This compares unfavourably compared to a ICBM
which can hit any target in the world in 15-20 minutes.

This would require the military to think intelligently and not waste money.
There is however a very sensible arguement against using ICBMs as
conventional weapons. It would set a precident, and could allow someone to
covertly launch a nuclear warhead, under the pretence it's merely a
conventional warhead.

A modified ICBM with a conventional warhead
would probably be just as effective.

Oh but the USAF couldn't do that! They might accidentally kill someone when
the first stage hit the ground...

ANTIcarrot.

"Rand Simberg" wrote ...
That's the theme of my latest column at TechCentralStation:
http://www.techcentralstation.com/033104C.html

I understand that scram-jets can work at higher altitudes. The test flight
occured at 28.5km (95k ft) which is higher than either concorde or military
jets. From memmory a scram-jet could fly even higher. Does anyone know if
this woudl have a significant impact on sonic boom at ground level?

The point of gathering fuel 'for free' is to reduce the size of the vehicle
(which can lead to all sorts of benifits) not to save on fuel or oxidiser
costs. I agree though this is a very dumb idea.

WTF are they doing cancelling the RS-84 though??! They *NEED* a restartable
engine if they're going to go to Mars and stop once they get there!!! It's
also a perfect candidate for any kind of luna mission space-tug. Idiots.
Bloody idiots...

ANTIcarrot.

h (Rand Simberg) wrote:
That's the theme of my latest column at TechCentralStation:
http://www.techcentralstation.com/033104C.html

Yes, and it includes your usual theme of NASA bashing, but you reach a
new low by mis-stating the facts and engaging in hyperbole. The very
selfsame sin you accuse the mass media of.

And I quote from the article:

However, it's possible to overstate the achievement, and both the program
personnel and the media are doing that. For instance, one would have the
impression from the coverage that a scramjet had never been previously
tested in flight, when in fact the Australians did this almost two years ago, with
a tiny fraction of the Hyper-X budget.

And now for the rest of the story...

The Hyshot test was a failure. Their intent (like the X-43A) was to
demonstrate SCRAM mode. Sadly while producing enough thrust to
accelerate the vehicle, the engine burned in subsonic RAM mode. In
other words, the Australians *didn't* do anything with a fraction of
the X-43A budget, but rather they demonstrated something very
different, an improved ramjet.

The significance of this flight was not that it was an in-flight test of a scramjet,
but that it generated sufficient thrust to actually accelerate the vehicle.

If a NASA PAO generated the same statement about X-43A, you'd be among
the first to crawl all over them for making a 'failure' a 'sucess'.

D.
--
Touch-twice life. Eat. Drink. Laugh.

"Uddo Graaf" wrote:
I myself even have doubts about the military applications for the hypersonic
bomber the Air Force is envisioning. The goal is to have almost zero
decision-to- impact time but a hypersonic vehicle can hardly loiter around

Why not?

and would probably have a huge turning circle travelling at its minimum
speed (mach 5).

Which means you start your run from farther away. Oddly enough,
that's what you want to do anyhow in order to loiter beyond the reach
of enemy radars and AA defenses.

It would take about 10 minutes to get a bomb on target by such as bomber
after the 'go' was given. This compares unfavourably compared
to a ICBM which can hit any target in the world in 15-20 minutes.

It also compares favorably with the ICBM in that it has a faster
response time, and can be called back.

D.
--
Touch-twice life. Eat. Drink. Laugh.

On Wed, 31 Mar 2004 12:31:40 -0800 (PST), in a place far, far away,
(Derek Lyons) made the phosphor on my
monitor glow in such a way as to indicate that:

(Rand Simberg) wrote:
That's the theme of my latest column at TechCentralStation:
http://www.techcentralstation.com/033104C.html

Yes, and it includes your usual theme of NASA bashing, but you reach a
new low by mis-stating the facts and engaging in hyperbole. The very
selfsame sin you accuse the mass media of.

The difference, of course, is that I make corrections when called on
it, which they generally don't (e.g., Gregg Easterbrook).

The Hyshot test was a failure. Their intent (like the X-43A) was to
demonstrate SCRAM mode. Sadly while producing enough thrust to
accelerate the vehicle, the engine burned in subsonic RAM mode. In
other words, the Australians *didn't* do anything with a fraction of
the X-43A budget, but rather they demonstrated something very
different, an improved ramjet.

I hadn't seen that follow up.

The significance of this flight was not that it was an in-flight test of a scramjet,
but that it generated sufficient thrust to actually accelerate the vehicle.

If a NASA PAO generated the same statement about X-43A, you'd be among
the first to crawl all over them for making a 'failure' a 'sucess'.

If I had been aware, yes. I'll research further and see if I can
rectify it. Thanks for the correction.

On Wed, 31 Mar 2004 13:08:02 -0800 (PST), in a place far, far away,
h (Rand Simberg) made the phosphor on my
monitor glow in such a way as to indicate that:

If a NASA PAO generated the same statement about X-43A, you'd be among
the first to crawl all over them for making a 'failure' a 'sucess'.

If I had been aware, yes. I'll research further and see if I can
rectify it. Thanks for the correction.

OK, Derek, you're going to have to provide a cite for your claim,
because I can't find any references to it. Everything I find
indicates a test success.

Moreover, because neither ramjets or
scramjets work at low speeds (note that the test vehicle had to be
accelerated to scramjet velocities with a commercial
rocket), any commercial hypersonic
transport would have to have conventional
(and supersonic) turbofans in addition to the scramjet motors, resulting in
two
separate (and heavy) propulsion systems.

How about a maglev launched Scramjet? Just build a short maglev track, (The
Chinese have one), that can accelerate the maglev to 7 times the speed of
sound. The scramjet then takes off from that, flies to orbit and then glides to
a runway landing.

Tom

On 31 Mar 2004 22:13:46 GMT, in a place far, far away,
(TKalbfus) made the phosphor on my monitor glow in
such a way as to indicate that:

How about a maglev launched Scramjet? Just build a short maglev track, (The
Chinese have one), that can accelerate the maglev to 7 times the speed of
sound. The scramjet then takes off from that, flies to orbit and then glides to
a runway landing.

A scramjet can't fly to orbit. It only works in the atmosphere.
Amazingly enough, there were people working on NASP who didn't
understand this.