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Hypersonics Overhype



 
 
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  #21  
Old April 2nd 04, 12:23 PM
Pat Flannery
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Default Hypersonics Overhype

John wrote:

Can someone please tell me how something that's broadcasting that much IR
can be called 'stealthy'?


Okay...so it may tend to get a bit warm at those speeds :-) .... I
assume the "stealth" is supposed to be in regards to radar rather than
IR; but it would be interesting to determine how much of the IR would
get to the ground if the emitter's at an altitude of 150,000 feet or
more, as the atmosphere may soak a lot up. The big advantage of
something moving (and maneuvering) at around Mach 5 and those altitudes
is that it's going to be very difficult to hit with a ground launched
missile unless you have a fair degree of warning of its approach, so
that the missile can reach its target's future position when the target
also arrives at it. That's easier to do with radar than IR, and the
fact that the hypersonic missile can maneuver greatly complicates the
intercept problem for the forces trying to intercept it.... you may
launch at a predicted position where you assume it's going to be, then
it turns... and suddenly your interceptor missile finds that it's
heading toward the wrong piece of sky, and that it has too much inertia
and too little fuel and time to change its course to achieve a
successful intercept. At these speeds even slight turns mean miles away
in a matter of a few seconds. If scramjet missiles become widespread,
they are going to be a major incentive to develop directed energy
weapons to deal with them- as that's one of the few things that could
slew around fast enough to target a maneuvering one...otherwise you are
going to need things like super Sprint ABM's just to get to them in time.
And it seems very likely that they are going to be in a _lot_ of
country's inventories around 20 years down the line...even India is
working on one.

Pat

  #22  
Old April 2nd 04, 07:05 PM
Derek Lyons
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Default Hypersonics Overhype

"Bill Bonde ( Not the man who knows everything, just the man who knows
the important things )" wrote:

The ABC thinks it was a success:

http://www.abc.net.au/science/slab/hyshot/default.htm
#begin quote
did the test go?


Well; that's nothing but an account of the test launch, not a summary
of the science. Don't confuse the two.

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

  #23  
Old April 2nd 04, 07:16 PM
Derek Lyons
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Default Hypersonics Overhype

Pat Flannery wrote:
At these speeds even slight turns mean miles away
in a matter of a few seconds.


Keep in mind that this applies to the cruise missile as well as the
interceptor, the closer the cruise missile comes to it's target, the
less it can maneuver.

Take a notional hypersonic cruise missile taking a path from Soviet
Russia to Offut AFB. While it's still over the Canadian Shield, it
can maneuver practically freely. However, as it approaches the US
border, the 'wedge' it can be in and still strike it's target narrows
pretty rapidly, since even a minimum radius turn can throw it miles
off target. At some point the incoming missile can no longer turn,
but must remain more or less on a direct course.

What this means is that your defense problem changes from a long range
intercept well down range into something close to (but not quite) a
point defense intercept. Difficult, but not perhaps requiring
directed energy weapons.

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

  #24  
Old April 2nd 04, 08:03 PM
Bent C Dalager
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Default Hypersonics Overhype

In article ,
Derek Lyons wrote:
Take a notional hypersonic cruise missile taking a path from Soviet
Russia to Offut AFB. While it's still over the Canadian Shield, it
can maneuver practically freely. However, as it approaches the US
border, the 'wedge' it can be in and still strike it's target narrows
pretty rapidly, since even a minimum radius turn can throw it miles
off target. At some point the incoming missile can no longer turn,
but must remain more or less on a direct course.


This problem can still be compensated for though, with two primary
strategies.

1. The missile can be preprogrammed to make course variations
throughout that would make it appear to be aimed at something that it
is not. Thus, it can be statically pre-programmed to make last-second
course adjustments very close to its target that will throw off the
defenders' predictions of where it's headed. The missile is still
somewhat vulnerable however since, as you point out, there will still
be a point-of-no-evasion some distance from its target.

2. The missile can be preprogrammed with a number of primary and
secondary targets and, assuming it is somehow kept updated on enemy
countermeasures being deployed against it, can keep varying its course
to evade them so long as at least one of its eligible targets is
within the 'wedge'. The missile can then evade counter-measures up to
the very last second since while it might miss its target by doing so,
it will simply allocate a new one. The problem then becomes one of
fuel consumption; how long can it keep up the game before running dry.

Cheers
Bent D
--
Bent Dalager - - http://www.pvv.org/~bcd
powered by emacs

  #25  
Old April 2nd 04, 08:39 PM
Pat Flannery
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Default Hypersonics Overhype

Derek Lyons wrote:

Pat Flannery wrote:


At these speeds even slight turns mean miles away
in a matter of a few seconds.



Keep in mind that this applies to the cruise missile as well as the
interceptor, the closer the cruise missile comes to it's target, the
less it can maneuver.

The trick is to have it's target be at the end of a last violent
maneuver; and hope the enemy doesn't suspect what exactly the target is
until it's too late.


Take a notional hypersonic cruise missile taking a path from Soviet
Russia to Offut AFB. While it's still over the Canadian Shield, it
can maneuver practically freely. However, as it approaches the US
border, the 'wedge' it can be in and still strike it's target narrows
pretty rapidly, since even a minimum radius turn can throw it miles
off target. At some point the incoming missile can no longer turn,
but must remain more or less on a direct course.

What this means is that your defense problem changes from a long range
intercept well down range into something close to (but not quite) a
point defense intercept. Difficult, but not perhaps requiring
directed energy weapons.


It's still going to be a very challenging intercept, especially if the
incoming missile uses stealth; another thing that has been looked into
is have the incoming missile release submunitions as it approaches it's
target, making the task of the defenders more difficult as multiple
submunitions must then be dealt with before they arrive. If that
technique is used, then the parent missile can zig and zag all over the
place as long as it passes at some point close enough to its target or
targets in its trajectory that the maneuver capabilities of its
submunitions allow the objective to be reached. In either case you have
to disperse your ACM (Anti Cruise Missile) interceptor missiles to more
potential target sites so that they can have the time to reach any
incoming missile or sub-warhead as it approaches. And if you put rocket
engines on the submunitions, they may arrive at speeds substantially
higher than their parent missile.

Pat

  #26  
Old April 2nd 04, 08:57 PM
Pat Flannery
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Default Hypersonics Overhype

Bent C Dalager wrote:

2. The missile can be preprogrammed with a number of primary and
secondary targets and, assuming it is somehow kept updated on enemy
countermeasures being deployed against it, can keep varying its course
to evade them so long as at least one of its eligible targets is
within the 'wedge'. The missile can then evade counter-measures up to
the very last second since while it might miss its target by doing so,
it will simply allocate a new one. The problem then becomes one of
fuel consumption; how long can it keep up the game before running dry.




Yeah, if can't hit the ICBM complex at Laputa, it can always head for
Barshaw instead.
(I'm getting of this image of of a hypersonic missile inbound toward a
heavily defended area running into interceptor after interceptor, and
going further and further down it's list of strategic targets to
attack...finally it sets itself on its last target option... and as he
sits in the outhouse of his dacha, the Russian Assistant Undersecretary
for Turnip Pest Control Measures gets the greatest and last surprise of
his Red Turnip Beetle hating life.)

Pat

  #27  
Old April 3rd 04, 12:52 AM
Henry Spencer
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Default Hypersonics Overhype

In article ,
Derek Lyons wrote:
At these speeds even slight turns mean miles away
in a matter of a few seconds.


Keep in mind that this applies to the cruise missile as well as the
interceptor, the closer the cruise missile comes to it's target, the
less it can maneuver.


Yes and no and kind of. It depends on whether you measure "close" in
distance or in time. Given equal availability of aerodynamic lift -- a
large assumption, admittedly -- the cross-range the missile can achieve in
a given *time* is about the same whether it's doing Mach 0.8 or Mach 8.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

  #28  
Old April 3rd 04, 01:32 AM
Derek Lyons
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Default Hypersonics Overhype

(Bent C Dalager) wrote:
1. The missile can be preprogrammed to make course variations
throughout that would make it appear to be aimed at something that it
is not. Thus, it can be statically pre-programmed to make last-second
course adjustments very close to its target that will throw off the
defenders' predictions of where it's headed. The missile is still
somewhat vulnerable however since, as you point out, there will still
be a point-of-no-evasion some distance from its target.


The problem is, the faster you are flying and the larger your turn
radius, the farther the no-evasion point gets from the actual target.
In addition, the more course changes you have, the longer it takes to
get to your target (making it hard to coordinate strikes) and the more
fuel you eat.

2. The missile can be preprogrammed with a number of primary and
secondary targets and, assuming it is somehow kept updated on enemy
countermeasures being deployed against it, can keep varying its course
to evade them so long as at least one of its eligible targets is
within the 'wedge'. The missile can then evade counter-measures up to
the very last second since while it might miss its target by doing so,
it will simply allocate a new one. The problem then becomes one of
fuel consumption; how long can it keep up the game before running dry.


No, the real problem is making sure that targets are hit, and that
half your strike doesn't waste itself on one 'easy' target while the
majority of the targets are unhit.

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

  #29  
Old April 3rd 04, 02:10 PM
Vincent Cate
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Default Hypersonics Overhype

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

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

At this URL Rand says:
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.


Are we sure that it had more thrust than drag? For how much
of the 10 seconds? Do we know the before and after speeds
around these 10 seconds? Are you sure that you are not part
of the hyper-hype? :-)

-- Vince

  #30  
Old April 3rd 04, 02:10 PM
Bill Bonde ( Not the man who knows everything, jus
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Default Hypersonics Overhype

Derek Lyons wrote:

"Bill Bonde ( Not the man who knows everything, just the man who knows
the important things )" wrote:

The ABC thinks it was a success:

http://www.abc.net.au/science/slab/hyshot/default.htm
#begin quote
did the test go?


Well; that's nothing but an account of the test launch, not a summary
of the science. Don't confuse the two.

I thought they were claiming that it accelerated the craft in SCRAM
mode. Maybe I misread it.

 




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