Defense against Hypersonic Glide Vehicles

sferrin

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Just starting a generic thread here to discuss possibilities and programs. Saw the following in an AvWeek article:

"These include a new family of interceptor missiles called SkyFire proposed by Raytheon; hypervelocity projectiles designed by General Atomics, Boeing and BAE Systems; a laser gun offered by Boeing; and electronic attack systems conceptualized by Northrop Grumman, L3 Technologies and Lockheed. Lockheed also has proposed a full range of new interceptors, including a space-based system, an air-launched missile and the “Valkyrie” for terminal hypersonic defense. "

http://aviationweek.com/defense/top-us-hypersonic-weapon-program-facing-new-schedule-pressure#comment-1090641


Anybody know anything about these?
 

Orionblamblam

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sferrin said:
a laser gun offered by Boeing;
I have doubts about the utility of lasers against hypersonic weapons. Not only do they have to punch through a potentially incandescent leading edge shockwave they also have to damage structures that are *designed* for high thermal and structural loading.
 

Trident

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Said structures are operating in a thermal environment which is already challenging to begin with though, so there might not be a lot of margin to bear additional heat load. The straw which breaks the camel's back...

I do agree about the optical challenges imposed by hypersonic flow past the target - lasers currently seem to have quite enough problems dealing with normal atmospheric distortion and turbulence.
 

sublight is back

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Trident said:
.....seem to have quite enough problems dealing with normal atmospheric distortion and turbulence.
Only if they are coming from the terrestrial side.... ;)
 

sferrin

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Even radar has problems getting through the plasma layer. With Sprint they needed quite a bit of power to communicate through it. I would think it would be even more difficult for a much shorter wavelength laser.
 

Orionblamblam

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Trident said:
Said structures are operating in a thermal environment which is already challenging to begin with though, so there might not be a lot of margin to bear additional heat load. The straw which breaks the camel's back...
*IF* the thing is flying fast enough to create an incandescent gas layer, then it has a pretty good shield against lasers. A gas that is transparent to visible or IR becomes very, VERY opaque to visible or IR if it's glowing. So a laser would strike that and heat up the outer layer of the gas, but little to none of that energy would likely punch through to the vehicle.

Of course it's a safe bet that the incandescent "shield" will only cover leading edges, not the whole thing. So a strike at the side might work. But head-on, the laser has a challenge.
 

jeffb

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Would there be any benefit to disturbing the air ahead of the object? Aim to create a series of detonations ahead of or beside the vehicle timed to disrupt the plasma or induce a tumble.
 

starviking

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Orionblamblam said:
*IF* the thing is flying fast enough to create an incandescent gas layer, then it has a pretty good shield against lasers. A gas that is transparent to visible or IR becomes very, VERY opaque to visible or IR if it's glowing. So a laser would strike that and heat up the outer layer of the gas, but little to none of that energy would likely punch through to the vehicle.

Of course it's a safe bet that the incandescent "shield" will only cover leading edges, not the whole thing. So a strike at the side might work. But head-on, the laser has a challenge.
Heating the outer layer should have some effect on the pressure & volume of the outer layer - which could have some effect on the aerodynamics of the HGV.
 

marauder2048

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sferrin said:
Even radar has problems getting through the plasma layer. With Sprint they needed quite a bit of power to communicate through it. I would think it would be even more difficult for a much shorter wavelength laser.
I thought that plasma sheaths were actually more permeable to shorter wavelengths...
 

Trident

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Orionblamblam said:
*IF* the thing is flying fast enough to create an incandescent gas layer, then it has a pretty good shield against lasers. A gas that is transparent to visible or IR becomes very, VERY opaque to visible or IR if it's glowing. So a laser would strike that and heat up the outer layer of the gas, but little to none of that energy would likely punch through to the vehicle.
Concur, as I said. A laser-based HGV defence faces a big hurdle, but (in my view) it's the hypersonic flow, not the vehicle structure.

starviking said:
Heating the outer layer should have some effect on the pressure & volume of the outer layer - which could have some effect on the aerodynamics of the HGV.
The 21st century equivalent of toppling V1s? Certainly an interesting idea.
 

TomcatViP

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We wrote about this idea some time ago.

You have to keep in mind that the boundary layer of an HGV is predominantly driven by the surface temperature and the Reynolds number.*
By playing randomly with the temperature of the body surface you can probably destabilize the vehicle, overloading its ctrl computer.

As I wrote much earlier, its then light speed Vs signal speed


*There are some certainly other trick to play like like coupling a laser and a pulsed HPMW to have a burst effect turning the smooth ride to something like navigating on a sea of popping popcorn ;)
 

marauder2048

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Given that the control system has to be able to respond to destabilizations due to random/un-even
ablation anyway I tend to think the dwell times are going to be close to what RAND
was suggesting is the typical timeline for burn through against HGVs (several tens of seconds).
 

Orionblamblam

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marauder2048 said:
Given that the control system has to be able to respond to destabilizations due to random/un-even
ablation anyway
Birds, bugs, rain, hail, clouds, smoke, dust. Never mind various forms of "wind."
 

fredymac

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I always associated plasma sheaths with deliberate deceleration. How much range can you maintain while simultaneously generating a shock wave strong enough to ionize air? What is the flight profile of an HGV? For any significant range will it be mainly above the atmosphere and only come down to skip/maneuver during course changes?
 
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