back to article Raygun 747 missile-zapping test video released

The US Missile Defence Agency has released video of last week's test of the Airborne Laser Testbed (ALTB) - the huge, jumbo-jet-mounted laser cannon built to blast hostile ballistic missiles out of the sky as they boost upward from their launch sites. The ALTB was formerly known simply as the Airborne Laser (ABL), but has …

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  1. Michael H.F. Wilkinson Silver badge
    Joke

    It would be a hell of a way

    to light a barbeque

  2. Anonymous Coward
    Boffin

    Counter measures ?

    Now while I haven't tried this, I'm wondering if wrapping missiles in a special reflective materiel (that's up to the job) wouldn't render the laser canon ineffective?

  3. FlatSpot
    Black Helicopters

    Events are accurate but not shown in realtime

    so err how long were they frying it for.. couple of hours/days??

    1. Anonymous Coward
      Boffin

      Re: Counter measures ?

      Wrapping it in tipfoil might make it look pretty, but it's not likely to do much for heat dissipation.

    2. lIsRT
      Boffin

      The title is required, and must contain letters and/or digits.

      Apparently not - unless it's 100% reflective, some of it will be vaporised and the vapour will start to absorb the laser energy instead, then the energy just conducts as heat into the coating (which then disintegrates).

      Or so I read.

      1. Michael H.F. Wilkinson Silver badge
        Boffin

        One might still

        coat a missile with an ablation-type heat shield (think Apollo era). If it is also reflective (in the correct wavelength band) it will reflect part of the heat, but that by itself is apparently not enough. However, if you allow a thick shield to evaporate this has two effects: It carries the heat away from the missile effectively, and could create a cloud of droplets or particles which could scatter part of the laser energy. The vapour absorbing energy is not a problem as it will not conduct energy to the missile effectively.

        Launching missiles in thick fog could help, but IR travels quite far through fog (would reduce range further though).

  4. PATSYQB

    lasers - my arse

    WTF??? Nothing here that couldnt be run off in 10 mins with a cracked copy of After Effects.....

  5. Anonymous Coward
    WTF?

    Hey Wait

    What ever happened to the ground based one we were supposed to sell to Israel? The one that was shooting tank shells out of the sky?

    1. Dapprman

      It was completed and successfully tested

      However there were strong objections to the disposal of the toxic waste produced. Apparently the residents of the northern towns actually felt it was safer to put up with the occasional missile (most land harmlessly) than have a large toxic waste dump near by - though this was before the big increase prior to the last major Israeli incursion of Gaza.

      1. Ammaross Danan
        Megaphone

        Well

        Just slap a nuclear reactor in the back of the plane. Electro lasers powered by such would be more than capable of one-shotting a missile in a few seconds, not this horrid 1-minute crap. Hate to have to stem off 5 missiles at once.

        1. Trevor Pott o_O Gold badge

          @Ammaross Danan

          First off, "slapping a nuclear reactor in the back of a plane" would violate quite a few treaties, not to mention make eleventeen squillion NIMBYs explode.

          Secondly, you could put the biggest power source you wanted on that plane, but power generation isn't the problem. (Power generation on something the size of a 747 isn’t a problem. The solid state array required for a megawatt-class laser isn’t that big, leaving plenty of room for old-fashioned fossil-fuel-based generators.)

          Heat is the killer to this idea. A large portion of all the energy you are pumping out is converted to light, but not all...when you are talking megawatt class lasing, this is a terrific engineering problem. You have to sink that heat off your lasers, (and possibly your focusing mechanisms, I honestly don’t know the answer to that one,) conduct that heat to an appropriate radiator, and then radiate it away.

          Big ass water-cooling system and/or heat pipes can help with some of that, but where do you dump the heat? Directly into the atmosphere isn't exactly an option. The air be a little thin where they be lasing, and the surface area required starts to boggle the mind. I am sure with enough time and effort the heat dissipation issue can be overcome, perhaps by recycling the waste heat into sub-generation, perhaps by using heat pumps to dump the heat as super-heated exhaust. This gets into the realm now of muchos big time maths, and a lot of trial-and-error.

          Either way, we can cheerfully pack a megawatt+ worth of generation capacity onto a 747 without ever having to put fissionables into a position where they might be blown up in our atmosphere. Avoiding the scattering of fissionables everywhere helps keep the rate of exotic cancers down.

          If you can come up with some neat ways to overcome the heat dissipation problems however, then DARPA would love to hear from you.

          1. Michael H.F. Wilkinson Silver badge

            Actually, quite a large percentage is heat

            Some 50% or more. Getting rid of heat is one of the real thermodynamical nightmares. As Eddington (I think it was) once said: "If you want to break the second law of thermodynamics, there is no hope."

  6. Alex-TheManfromUncle
    Black Helicopters

    .. dejavu?

    I feel I've read this article somewhere else before.......

    Questionable time stamps on the video, as I have seen the second segment at the end of last year...

    Blackhelicopters, as something is turning rank very quickly...

  7. Anonymous Coward
    Boffin

    What was that?

    There were some pictures of coloured lights. I have no idea what they meant. There's certainly nothing to confirm that it was a raygun blootering a rocket out of the sky.

  8. BarryMc
    Coat

    Fake!

    Obviously fake.

    Everyone knows that lasers go PEW!PEW! when fired.

  9. heyrick Silver badge

    This is geniune?

    Nothing I couldn't do with a cheap laser pointer, halogen-bulb torch, couple of christmas tree lights, and a low-band video camera running with the focus wonky. Don't even need computer editing beyond VirtualDub for splicing the bits together...

  10. Pascal Monett Silver badge

    "[the Iranian missile threat] did not come as fast as we thought it’d come"

    Somewhat like the WMD menace in Iraq then, eh ?

    Good thing they didn't invade first, this time.

    1. Anonymous Coward
      Alert

      Quite a few defense analysts..

      ..over the last few years have clutched their crystal balls and opined that when it all kicks off, Israel will be involved.

      They're mighty jumpy over there, a bunch of warlike right wingers running the military of a nuclear state- surrounded by countries which really are out to get them, paranoia aside. Hell of a situation- my money is on Israel nuking Iran or vice versa. It's not going to be good.

      On the upside, if things get out of hand, living in London, I'll be a prime nuke target, and likely die nice and fast :)

  11. John Smith 19 Gold badge
    Happy

    running some numbers

    Heat could well be the long pole in this tent. The laser diode pumped lasers are pretty good on this at (IIRC) about 32% efficiency. I've no idea what chemical systems are. From memory HeNe is around 5%. The rest (68% or 95% depending on system) is heat. Chemcial systems were chosend for their (apparent) mechancial simplicity, not necessarily for there efficiency.

    So a MW class laser has to dump somewhere between 2 and 19MW. To put that in perspective. 1MW/m^2 was the Apollo heat shield spec (which at 100W/cm^2 is also roughly the heat output of a modern CPU).

    So you're looking at 2-19 square metres (205 Sq Ft) of heat dumping surface. Large but not impossible *provided* you have a heat sink to dump the heat into. It would not be the first time people have used the fuel for cooling. Likewise engine intake air (at 40kft) is also pretty cold If the efficency is <5% then you're proportionately in bigger trouble. Heat pipe cooled leading edges were proposed for the space shuttle (the top surface of the wing during re-entry is a *lot* cooled than the edge or windward sides) but an aircraft with a wing mounted radiator has not (AFAIK) flow since the 1930's.

  12. AdamP
    Pirate

    Real Genius

    Val Kilmer will be so pissed

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