4 ms·

Well, you could also target your immediate neighbors. I bet most of the richest and most industrialized eastern china would be right inside the viable target ar

Well, you could also target your immediate neighbors. I bet most of the richest and most industrialized eastern china would be right inside the viable target area. Also, think anti-ballistic missile defences -- no need for adaptive optics and all that jazz when you can swat the missiles with lasers from their most vulnerable position, right at the top of their trajectory.

jacquesm 17y ago
One gigawatt is a tremendous amount of energy, but what microwave radiation would do against an incoming ICBM is an open question. It's all about how concentrated the beam will be and how fast you can direct it (ICBMs move pretty fast and even at the top of their trajectory they are hard to pinpoint because they do not exactly carry homing beacons). Also, in all of the following keep in mind that we're talking about a re-entry vehicle here which has extensive heat shielding anyway just to survive its inevitable contact with the atmosphere. It is more about energy density if this could be used as a weapon against an ICBM or not, the receiver of the energy would presumably be a fairly large patch of ground with a 'safe zone' around it in case of minor misalignment. If you'd want your gigawatt to be concentrated in an area of 100x100 m under 'normal 'conditions you will not be able to quickly reconfigure to something on the order of a hotspot as produced by a battle laser (this is not a laser!). In normal operating conditions and assuming they can beam as tight as 1,000,000,000 Watts per 100x100m patch (which remains to be seen) you'd have about 100KW / square meter, or about 10 W / square centimeter assuming absolutely perfect (so lossless) transmission and 0 reflection. Microwave absorption of the ICBM would then be the deciding factor if anything happened to it or not, 10W / square centimeter seems a lot but it really isn't, the question is how long the beam could be focused on the incoming ICBM and how steady it could be held. With lasers this appears to be possible, see this http://boeing.mediaroom.com/index.php?s=43&item=817 http://boeing.mediaroom.com/index.php?s=43&item=817 but it was an aircraft at subsonic speeds vs a stationary ground target. Shooting stuff down that moves very fast is not that easy, especially not if your normal mode of operation is for energy transmission instead of destruction.
- Tuna-Fish 17y ago
  Who was talking about shooting icbm's with microwaves? If you have a gigawatt power generation platform in space, putting a couple of free-electron lasers up there is hardly more than an afterthought. With a big enough laser, you can stop having to worry about the heat shielding/reflectivity of the target, and just trust that the second you hit something, it's surface is going to ionize (= blow up). And as for hitting the targets up there, at the apex of their trajectory ICBM's are 1) ballistic 2) slow compared to the other parts of their flight. While hitting is still not exactly easy, other than hitting them on the launch pads it's the easiest way to do the (hard) task.
  - jacquesm 17y ago
    You make this sound a little easier than it is, really, but you are right that if you do want to hit them the top of the trajectory is one of the best times to try to do it. Unfortunately the people that launch these things are well aware of that, which is why if they are launched they are not launched 'one-by-one' to allow you to recharge your lasers between shots. Another slight problem with the strategy is that any attacker capable of launching an ICBM at a country would probably also have the capability to hit that platform, and wich a 1GW radiated output it provides you with a really nice fat target.
  - ars 17y ago
    Why would it blow up? Nuclear bombs don't blow up when they get hot. All that would happen is you would make a hole in it, but since it's on a ballistic it would keep on going. (Ballistic means gravity is controlling it, it's not powered.) Even if you blew it up, at best you would spread nuclear material all over the target area. You need to hit these things during the boost phase, where a: you can stop it from going ballistic and make it fall back into the launching country, and b: you have something volatile to blow up (the fuel). Also, it's easier. When it's at the apex it's moving horizontally very quickly, and it's at it's closest to you. Which is the most difficulty when it comes to aiming (since the angle of the shot is moving the fastest at that point). When it's moving vertically toward you is much easier to aim, since you barely have to move the laser.

jacquesm 17y ago

One gigawatt is a tremendous amount of energy, but what microwave radiation would do against an incoming ICBM is an open question. It's all about how concentrated the beam will be and how fast you can direct it (ICBMs move pretty fast and even at the top of their trajectory they are hard to pinpoint because they do not exactly carry homing beacons). Also, in all of the following keep in mind that we're talking about a re-entry vehicle here which has extensive heat shielding anyway just to survive its inevitable contact with the atmosphere. It is more about energy density if this could be used as a weapon against an ICBM or not, the receiver of the energy would presumably be a fairly large patch of ground with a 'safe zone' around it in case of minor misalignment. If you'd want your gigawatt to be concentrated in an area of 100x100 m under 'normal 'conditions you will not be able to quickly reconfigure to something on the order of a hotspot as produced by a battle laser (this is not a laser!). In normal operating conditions and assuming they can beam as tight as 1,000,000,000 Watts per 100x100m patch (which remains to be seen) you'd have about 100KW / square meter, or about 10 W / square centimeter assuming absolutely perfect (so lossless) transmission and 0 reflection. Microwave absorption of the ICBM would then be the deciding factor if anything happened to it or not, 10W / square centimeter seems a lot but it really isn't, the question is how long the beam could be focused on the incoming ICBM and how steady it could be held. With lasers this appears to be possible, see this http://boeing.mediaroom.com/index.php?s=43&item=817 http://boeing.mediaroom.com/index.php?s=43&item=817 but it was an aircraft at subsonic speeds vs a stationary ground target. Shooting stuff down that moves very fast is not that easy, especially not if your normal mode of operation is for energy transmission instead of destruction.

Tuna-Fish 17y ago
Who was talking about shooting icbm's with microwaves? If you have a gigawatt power generation platform in space, putting a couple of free-electron lasers up there is hardly more than an afterthought. With a big enough laser, you can stop having to worry about the heat shielding/reflectivity of the target, and just trust that the second you hit something, it's surface is going to ionize (= blow up). And as for hitting the targets up there, at the apex of their trajectory ICBM's are 1) ballistic 2) slow compared to the other parts of their flight. While hitting is still not exactly easy, other than hitting them on the launch pads it's the easiest way to do the (hard) task.
- jacquesm 17y ago
  You make this sound a little easier than it is, really, but you are right that if you do want to hit them the top of the trajectory is one of the best times to try to do it. Unfortunately the people that launch these things are well aware of that, which is why if they are launched they are not launched 'one-by-one' to allow you to recharge your lasers between shots. Another slight problem with the strategy is that any attacker capable of launching an ICBM at a country would probably also have the capability to hit that platform, and wich a 1GW radiated output it provides you with a really nice fat target.
- ars 17y ago
  Why would it blow up? Nuclear bombs don't blow up when they get hot. All that would happen is you would make a hole in it, but since it's on a ballistic it would keep on going. (Ballistic means gravity is controlling it, it's not powered.) Even if you blew it up, at best you would spread nuclear material all over the target area. You need to hit these things during the boost phase, where a: you can stop it from going ballistic and make it fall back into the launching country, and b: you have something volatile to blow up (the fuel). Also, it's easier. When it's at the apex it's moving horizontally very quickly, and it's at it's closest to you. Which is the most difficulty when it comes to aiming (since the angle of the shot is moving the fastest at that point). When it's moving vertically toward you is much easier to aim, since you barely have to move the laser.