The February 11, 2010 test of the ALTB (the small, slightly horizontal blip on the right) against a target missile, the larger blip on the left. The target blip size is dominated by the exhaust plume.)
On February 11th, 2010, the Air Force successfully tested its Airborne Laser Test Bed (the new name for what was developed as the Airborne Laser or ABL). Since the ABL was how I got into this business, I feel a certain interest in its continued development. Others, especially Jan Stupl who is a Science Fellow at Stanford’s CISAC, have done a more complete analysis since I did my study (also as a CISAC Science Fellow ) on the ABL. Jan’s thesis at Hamburg University involved authenticating a finite element simulation of a laser heating up a rocket’s airframe by actually comparing it with experiments he did. I consider his study to represent the current state-of-the-art knowledge in the nongovernmental community. (While at CISAC, Jan has extended that study with a very important analysis of using lasers as anti-satellite weapons.)
I think my most important contribution to the ABL discussion was in presenting a way of thinking about laser missile defense engagements. This is summarized by this graph, which shows the two important curves for determining a laser’s effectiveness, which can be characterized by the length of time it takes the laser to heat up the rocket’s skin enough for internal stresses to break the missile apart. (See Jan Stupl’s work for more accurate time estimates.)
An example of how to think about laser engagements. It depends on the nature of the target missile as well as the laser’s energy; both of which are uncertain.
One graph, the “visibility” curve, shows how long the missile is visible to the ABL while it is under power. (The ABL’s kill mechanism requires that there be a large axial load on the airframe that is only there while under power.) As the ABL gets farther away, the Earth’s curve hides more and more of the powered flight either behind the Earth’s limb or, perhaps more likely, behind a large barrier of atmosphere that disrupts the laser beam. On the other hand, the farther away the laser is, the long it takes to deposit enough energy to cause a failure. That is represented by the graphs that are increasing dramatically with distance. The distance at which these two types of curves cross is the maximum range of ABL.
Videos of the February 11th test have been altered to mask the time of the actual engagement. (That is what they say at the start of each video segment.) My guess, based on how fast pieces seem to fall away, is that they have been sped up. Which, of course, makes the laser seem more effective. Another apparent feature of the videos is how close the target and the ALTB are. This has two effects. Most importantly, the engagement is much farther down the “time required” curves. But it also means a given change in the missile’s position, as it accelerates along its trajectory, will produce a bigger angular displacement as viewed from the ALTB. That should mean it is easier for the onboard targeting systems to follow the target. It also appears that the ALTB is pointing down when it fires. This could, of course, be an artifact of the position of the camera. However, if it is true, it means both that the laser is firing through more atmospheric turbulence (an impressive achievement) and that the rocket is moving slower than it would if it was allowed to gain altitude. The later means, of course, that it is easier to shoot down.
I think the target was probably one of the Scud-Bs that the US acquired back in the 1990s. See http://www.navsource.org/archives/10/11/10111006.jpg for one on the launch platform, the ex-USS Tripoli.
Wouldn’t any country that possesses the ability to launch an ICBM against the US easily shoot down a slow moving Boeing 747 flying a few hundred km from its ICBM?
> Wouldn’t any country that possesses the ability…
Defense suppression isn’t considered a topic for polite conversation in BMD circles. 🙂
Seriously, at some point the vulnerability of critical BMD components like the AN/TPY-2, SBX and so forth to targeted attack by a variety of means should be considered.
So it’s really pork barrels for star wars aficionados.
Well, let’s think about this.
If Country X decides it’s going to fight a nuclear war with the US, to nuke a bunch of our cities, then yes, they’re probably going to attack our warning and defense systems as part of that attack.
However, it’s hardly credible that anyone would seek to initiate something like that, as the retaliatory strike would be fairly catastrophic. Going after US cities en masse is step one of a two-step suicide dance.
ICBMs and nuclear weapons are useful – in the actually usable sense – as bargaining chips in diplomacy and deterrence. One can consider very limited uses as onsies or twosies against extremely important singular targets of some sort, which might not provoke a overwhelming counterattack. As theater or tactical weapons, nukes with shorter range delivery might make sense in other less strategic uses.
But attacking a warning platform is likely to be seen as the opening move of the suicide two-step. So anyone not actually attempting that attack on the continental US and their own suicide in response is going to avoid doing so, if they have any sense left.
One could see them being attacked as a particularly high-stakes move in an otherwise not-likely-to-go-nuclear confrontation, to make a particularly high-strung point, but in general there seems to be a conclusion that rational players will avoid targeting strategic systems in confrontations to avoid misunderstandings.
From: http://www.mda.mil/news/gallery_altb.html
“The entire engagement occurred within two minutes of the target missile launch, while its rocket motors were still thrusting. “
So the video is indeed sped up… a little hard to estimate where on that graph we are, since there’s also targeting and tracking…
Great theater for wide eyed and scientifically naïve congresspersons; ‘til numbers are released on the range, respective altitudes, beam dwell time, composition of target, etc.. this is only a light show with little merit beyond the seduction of a little coin out the taxpayers’s coffers in times of great financial duress.
I just don’t see how this is a strategic weapon in the nuclear sense of the word. Having to orbit and wait only 200 mi or so from the target means you are in a standoff with someone, or you are at war and have air superiority. The defender would be tempted to throw as many SAM’s, and low grade fighter jets at this thing as they could. I’ll bet this thing could do wonders for sweeping airspace clean of fighter jets. But there’s no way this thing would be useful against a foe with a real ICBM force designed and massed for a counterforce mission.
However, we did cross a rubicon. Two aspects of the old SDI (My fav sci-fi movie, staring Ronald Regan.) are now in place. Hit to kill is becoming easier and cheaper, and more nations are doing it. The ‘hitting a bullet with a bullet’ argument is going away. YAL-1 is in a way a prototype of the orbital laser battle station. 27 years after Regan’s speech we finally have something you could launch on a Saturn class booster and take a few shots for a few fleeting seconds of an off chance overflight from orbit. Who knows in another 50 years maybe some of this will be ready to deploy and then we’ll have a real debate instead of throwing shadows at one another.
So, Mr. Herbert, let me get this straight. Rational players won’t target the laser aircraft, because that would invite retaliation. And the bad guys aren’t crazy after all. At the same time, they are crazy, because we can’t deter their use of missiles against North America, so we need an airborne laser. Which we don’t have to protect against them because they aren’t crazy.
Or are you saying “Don’t worry, nobody would attack the laser plane unless they were going to attack the US anyway”? Because, I hate to break this to you, but I don’t think Mr. 3.1415 was worried about the poor little 747 per se.
The Youtube link is a hoot, complete with high-pitched whining sound when the laser is active: “Do you expect me to talk, Goldfinger?”… “No, Mr. Bond – I expect you to die!”
More seriously, a reflectivity of 90% seems awfully low – about the same as the shiny side of aluminium kitchen foil. Are we supposing that the missile users won’t increase the reflectivity of their missile bodies? For example, a silver foil coating would take reflectivity to about 95% above 400 nm, or gold to about 98% above 700 nm (i.e. if the laser is primarily infra red). Even at 95% the absorption is halved compared to 90%, resulting in a doubling of the dwell time of the laser. More interestingly, dielectric coatings could be tuned to the specific laser frequency; in lab applications they easily achieve reflectivities > 99.99%, although I’ve no idea if or how they could be applied to a missile body.
Then there’s the issue of beam absorption if the missile is flying through cloud, something that would further shorten the dwell time.
Sure there has been some impressive progress in the field of long-range laser weapons, but I think it’s going to be another decade or two before they’ve overcome even some of the elementary problems and counter-measures.
On a different note, do the pilots of the aeroplane have automatic eye protection e.g. an automatic visor that comes down before the laser goes active?
I don’t know how the numbers go, but I could imagine that if the laser strikes a flat surface on the missile and is momentarily reflected straight back at the aeroplane then the pilots can hardly rely on blinking! We’ve probably all experienced the momentary flash of sunlight from an aircraft many miles overhead, and even though these guys will be much further away, the brightness of the laser is vastly greater than the sun…
The Youtube video is a hoot: – sorry, my computer initially jumped to the “Future weapons airborne laser” clip.
Still, if you’ve nothing better to do, click on that one too – it looks like a promo video, and I can just imagine that there are Congressmen out there who would be concerned if a laser didn’t make the appropriate cutting-the-spy-in-half noises… 🙂
The snarky answer is, “shoot down the 747 with what – a missile?” We just learned who wins that fight 🙂
The more serious answer is, it won’t be just a slow-moving 747, but a 747 with an antimissile laser plus an AWACS, a couple of F-18Gs, and half a dozen F-22s. It’s not clear to me that a nation like e.g. North Korea could even track such a force orbiting a couple hundred kilometers out.
As we move up the threat ladder to e.g. Iran or China or Russia, the ABL looks rather less useful – except that in those cases we’d want to look at larger and more heavily-supported missile defense package. And, necessarily, a longer-term one. There are no short-term missile defense options against Russia, with or without ABL.
And, as George Herbert has noted, missile defense is only part of a package that includes deterrence, diplomacy, and various offensive options.
The complete disregard here for the scientific development process is staggering.
People, we realize that you are going to try and put down this test by any means, but Rome wasn’t built in a day. No, this wasn’t a perfect test, but its a giant leap in the right direction.
There’s nothing scientific about trying to develop a system that requires rewriting the laws of physics in order for it to become a viable system.
If you want to invest in basic research into bending laser beams around corners, or propagating them through several hundred kilometers of solid ground, that could lead to a usable system (in an alternative universe).
In this universe, ABL doesn’t make any sense, and testing it as a near-deployable system is vastly premature.
I agree with MJS that this is a development test, not an operational or evaluation test. Furthermore, it is important to recognize the importance of the name change: from an operational ABL to a Test Bed . Nevertheless, it is also important to understand the conditions that the test took place under and the reasons why those conditions were chosen. In particular, it was the weight problems associated with operational resonators that prevented this system from achieving anything close to a war fighting capability.
Since the ABL is limited to the physical dimensions of it’s host aircraft, would a larger ground based system be capable of achieving greater range or would atmospheric conditions negate any benefits of a larger laser? How well does a directed energy weapon scale? How much effectiveness would the heat generated by a laser have against the heat shield of a warhead on the descent?
It seems to me that a fleet of ABL’s, laser equipped satellites, and large ground lasers could theoretically constitute an impervious missile shield. Now I realize that this has near 0 percent chance of occurring considering the staggering cost involved and just how broke the US is, but theoretically would it be feasible? At least until any potential adversaries “blinged” up their missiles and applied reflective coatings.
George William Herbert said,
> If Country X decides it’s going to fight a nuclear war with the US, to nuke a bunch of our cities, then yes, they’re probably going to attack our warning and defense systems as part of that attack.
> However, it’s hardly credible that anyone would seek to initiate something like that, as the retaliatory strike would be fairly catastrophic. Going after US cities en masse is step one of a two-step suicide dance.
[snip]
> But attacking a warning platform is likely to be seen as the opening move of the suicide two-step. So anyone not actually attempting that attack on the continental US and their own suicide in response is going to avoid doing so, if they have any sense left.
> One could see them being attacked as a particularly high-stakes move in an otherwise not-likely-to-go-nuclear confrontation, to make a particularly high-strung point, but in general there seems to be a conclusion that rational players will avoid targeting strategic systems in confrontations to avoid misunderstandings.
I’m very, very reluctant to depend on everyone in such situations adhering to behavior that we would consider rational. But beyond that, even nominally rational actors can come up with radically different perceptions of what a situation is and what a rational response to it would be.
To construct an imaginary example, what if a future ICBM-armed Iran thought that its missiles’ purpose was not to destroy the Great Satan as an end in itself, but to deter the US from attacking their country and overthrowing the regime? In that case, would it not see a US BMD capability as intended to negate the deterrent and render Iran subject to attack? And, consequently, conclude that degrading the BMD capability (for example by attacking the southern FBX with a special forces team) would restore a deterrent relationship and be stabilizing, rather than the opposite?
As an aside, this kind of discussion has occured over the years in the satellite vulnerability/ASAT context. I tend to come down on the position that the temptation to gain military advantage (or redress disadvantage) would be very strong indeed and could well win the day.
Hairs, on eye protection: the ABL weapon (don’t know about the guide laser) operates at 1.315 µm, well into the NIR.
Technically it was the CSA isolation system that couldn’t scale well, not the resonator per se. Irrespective, this is a weapon without a role. Kick up the power an order of magnitude and this thing will still only be useful for battlefield blinding.
A near inf beam at 1315 nm & a 1.5m focusing element, assuming near perfect correction of the beam on the fly then we get the characteristic equation: D_t=.61*L*1.3E-6/1.5 =L*5.2E-7
Roughly target illumination works out to a 5.3 cm diameter circle @ 100km.
Since COIL is aiming for target power of 100kw and since we’re being generous and oblivious to the second law let’s say 100% of that is getting to target.
Therefore irradiation is 1.14kw/cm^2. Now if they hold this spot on for a few seconds it should cut thru a steel tank during boost phase. Of course in reality the beam will be jumping around the entire fuselage and their best bet would be to widen the beam, increase the dwell time and allow for the beam to slowly weaken the tank body of the missile so that aerodynamic stress would finish it off. Which seems to be what they did with the liquid rocket test and considering the thicker hide of a solid rocket may be why they were less successful in that shoot down attempt.(I’m not sure what the shel is outputting but if we accept ~<20kw then the range to target must have been snug, ~30km)
How effective would a 100kw operational ABL be? Not very seems to be the opinion of the military. After all, if this thing, under optimal conditions has to orbit <100km away from the boost phase flight path of the tactical missile, then wouldn’t firing off sams to create a launch window be the order of the day whenever surging a bevy of tactical missile? The ABL would have to undertake some evasive maneuvers while its CAP dealt with the threat and then a minute later, when the ABL could resume its mission, the boost phase is over. This thing simply serves no useful purpose save for blinding a few errant pilots or people on the ground.
The Airborne Laser testbed is going to be transfered away from the Missile Defense Agency and to the agency responsible for the recent 100+kW solid-state laser modules (and I believe they are headed to the same test facility), which makes me think that the chemical COIL laser modules (there are six of them) on the ABL are going to be replaced with solid-state ones over the next couple years (remember that a kilowatt-class solid-state laser is shown out through the main turret for atmospheric compensation, so many of the optics should work for solid-state lasers). Chemical lasers are simply too inconvenient to be used operationally, but solid-state lasers are now at the point where they have reached militarily relevant power levels, levels which can quite easily destroy mortars, missiles, artillery shells, etc and larger targets with more modules. With solid-state lasers, all you need is electricity.
BTW, the COIL laser on the ABL generates megawatt-level output power, not merely 100kW. 1kW/cm^2 is roughly the heating produced during orbital reentry, which is certainly no friend to airframes (have you ever tried launching an entire missile covered with ablative heatshield? Well, Iran’s missiles wouldn’t leave Iran if they did). All you need to do to cause aluminum to fail is to heat it to 350 degrees C.
Any reflective coating could be quickly destroyed by a 1kW/cm^2 heat load, which a 1MW ABL laser could deposit even at hundreds of miles. Any sort of reentry-tile system that could withstand prolonged contact with a 1MW laser would be far too heavy for any but very capable ICBMs, like the US and Russia have deployed.