I caught wind of this from another message board and the first thing I thought was “oh no, not this again”. Previous NMD threads have always pointed out:
That it’s fairly easy for ICBMs to fool targeting systems by deploying mylar balloons upon re-entry.
By the time we know we’ve missed, it’s too late to shoot up another interceptor.
Even if we do manage to hit a bullet with a bullet, the shrapnel still falls on our heads, possibly while armed.
Enter The Airborne Laser. This is a megawatt-class chemical laser mounted on the nose of a specially built Boeing 747-400F that is supposed to shoot down missles in their boost phase. According to the press releases:
Is this any less of a joke than the late 80’s “Star Wars” fantasies? The problems I can think of include:
In order to be able to target missles in their launch stage, the Boeing 747 has to be flying over the hostile country, violating their airspace.
I can’t imagine that a Boeing 747 is very manuverable. Wouldn’t it be pretty easy for a hostile country to send up a few dozen fighters to hunt it down?
The laser’s destructive energy is heat. Can’t the ICBM be fitted with a cheap asbestos jacket?
Regarding the question of heat, and the potential protection from asbestos insulation (or polishing the exterior to reflect the laser), these ignore the physics of it, mainly that the energy levels are so high, that the kill is achieved basically instantly. the metaphor I heard was “a ballerina can pirouette in front of a shotgun, but it won’t help.”
Unless things have changed recently, the Air based laser system is supposed to be part of a theatre defense system, not NMD. That means that it’s intended purpose is to, for example, shoot down Scuds fired at US bases during an invasion of Iraq. I think they’ve backed away from Reagan’s fantasy of a nationwide laserbeam network.
These threads: NMD, where for art thou? Does Israel have working ‘starwars’ technology?
have more information on the current programs.
Besides the fact that airspace violations would be the least of your worries if a WMD-loaded warhead was being launched at you… My understanding is that the range on this weapon is considerable, but I’ll have to go look for numbers. Russia would be able to launch from the interior of their country with no fear of the ABL, but normal-sized countries like Iraq or North Korea probably wouldn’t.
Enter the F-15C, armed with AMRAAMs. It would be protected the same way the US protects it’s AWACs aircraft. Very few countries can even contemplate successfully penetrating a US fighter screen. In most cases, sending up a few dozens fighters would only end up being a good way to make a lot of US aces.
True, although I don’t see why the ICBM’s have to be targeted “in their launch stage”. Just wait 'til they’ve gained a hundred miles or so of altitude, then you can fire at 'em from a few thousand miles away.
Yes, the version I saw on the Discovery Channel contemplated firing at them from extremem long range. Essentially, anytime it was not blocked by the horizon line.
The reason we prefer to target missiles during their boost phase is that they’re very easy to see from a long way away. After their engines (particularly their solid rocket boosters) have cut out, it’s practically impossible to see them well enough to target lasers at 'em from over a thousand miles away.
Where did you hear this from? I have heard people with a lot of knowledge say that increasing the reflectance of the surface and/or making the missile rotate would be quite effective countermeasures.
Your argument amounts to a claim that they can make the airborne laser with so much “overkill” in the absence of countermeasures that it will even still work with countermeasures in place. I certainly don’t think that the technical challenge of making it work at all, even in the absence of countermeasures, is so trivial!
Agreed, the need for a Wavefront Sensor (guide laser) to control adaptive optics (dynamic main beam focusing to counter atmospheric turbulence) strongly suggests that the airborne laser is still a system on the edge of feasibility. It’s way to early to claim that countermeasures will be ineffective.
On this point, I should note that the Bush Administration has been, seemingly purposely, blurring the distinction between theatre missile defense and national missile defense. (I think they even did a re-org of the agency along these lines.) For example, they are taking things such as the airborne laser that were being developed for theatre defense and saying, “Well this can be the boost phase part of a layered national missile defense.”
Unfortunately, as some experts have noted, it is not clear that systems designed for theatre defense can be even used as good starting points for a defense against ICBMs…At the very least, it would be a large jump from one to the other.
By the way, to add something that is really more relevant to the “NMD where art though?” thread that Squink linked to, but is worth noting: One reason that one is hearing less about missile defense recently is that Rumsfeld has decided to classify all the details about future tests (at least of the mid-course one that was basically the full NMD program under Clinton).
The supposed reason is that they have gotten to a stage in the program where they believe such classification is necessary in order not to tip off our adversaries. The more realistic reason is that they are tired of organizations like Union of Concerned Scientists using these details to point out how completely unrealistic the tests still are at this point.
I don’t see how that follows. Adaptive optics is a proven technology, and it can easily decrease the beam spot diameter by one order of magnitude. That means two orders of magnitude (100 times) higher power density. There’s nothing marginal about that.
Reflective coatings may not be as effective as you think. Even if you have a 98% reflective coating (not easy but possible), the 2% absorption is enough to heat up the surface and destroy the coating instantly. Polished metal surfaces are more durable but they only have 90% reflectivity.
I think insulation might be more effective. Still, covering the entire missile with ceramic tiles would be a major weight penalty. Don’t forget we are talking about the boost phase, so you have to protect the entire lower stage booster.
You need to specify a distance for your claim of “one order of magnitude”, and that’s where the problem lies. A factor of 100 power density increase at 10 miles is meaningless if you need to engage missiles 100 miles out.
The fact that the ABL uses adaptive optics implies that atmospheric beam dispersion can be a serious, mission threatening problem. Unfortunately, turbulance is a normal property of the atmosphere, increases with distance, and varies over time. Even the best optics in the world can only correct a limited amount of distortion, and the nature of the atmosphere implies that the range at which that correction is overwhelmed will vary wildly from hour to hour.
As far as I know, data on the effective range of the ABL has not been made public. Without that, we are left with only the knowledge that the designers have been forced to apply a first order solution to a second order problem. That’s often a sign of a system on the edge of feasibility.
It may turn out that adaptive optics give enough of a boost to make the ABL viable and unstoppable, but that remains to be proven.
“First order solution” in what sense? AO (adaptive optics) is a closed loop system - you move the optics until you get an undistorted wavefront. Ground-based astronomical AO systems routinely achieve 0.1 arcsec resolution, which translates to less than 10 inches over a 100 mile range. With the airborne laser you are looking through more air, but you don’t have to look through the really turbulent air near the ground so I think the conditions are comparable. Also, AO is a key technology not just for airborne lasers but also for all sorts of reconnaissance. The military must spend a lot of money on this.
Which isn’t to say that the whole project is easy. But I’d guess that air turbulence is not the most difficult problem. For instance, designing a mirror (esp. a deformable one) that withstands the power of the laser seems much more difficult to me.
Not an undistorted wavefront, but one that is as undistorted as possible. The system can only make a single correction for however many lenses form in the atmosphere. There’s non-ideal behavior and scattering associated with each of those. That’s not going to be a huge problem for the reconnaissance or targeting uses you mention, but it could be for the high power levels needed by the ABL. If as you say, it’s not a problem, why have they bothered to try to fix it ? This 97 GAO report tells us that:
Adaptive optics will no doubt improve the system, but question remains whether that will be enough. I guess they’ll tell us after they get done testing the complete system.
I don’t think that’s true. If you divide the output of the laser generator into infinitely thin beams, each one hits a unique point on the deformable mirror. If the mirror is infinitely deformable, you can change the direction of each beam independently and direct every one of them to the same point on the target. Of course, real-life systems would not do that, but I believe there is no theoretical limitation.
Thanks for the link, and you may be right. Though it’s hard to tell if the criticism is on the ultimate feasibility of such a technology or on the current management and design.
I think that the only way to really determine the feasibility is to try building the system. The ground based version is said to work well at short range (never missed according to TRW), but only testing will tell whether that translates well to the longer ranges envisioned for the ABL.
