David Suzuki warned us it'll never work:
Up until recently, plans to shoot down an enemy missile (from a "nation of concern" like North Korea or Iran) have focused on hitting one as it falls toward a target in the U.S.. A missile defense station is currently being built in Alaska for just that purpose, but such a strategy is fraught with technical problems. Hitting a small, tumbling warhead with another missile is no easy task. Tests of all but the most simple scenarios have routinely failed, and critics say that enemies could easily overwhelm any anti-missile system by using missiles with multiple warheads, decoys or other low-tech measures.
That was written in July of 2003. Despite the implication that development was abandoned on a system for intercepting an incoming warhead during the descent phase, such a system has recently been tested with great success (hat tip to small dead animals).
With all due respect to Dr Suzuki, he is a geneticist. There is nothing low-tech about multiple warheads or decoys. The whole point of a missile is to deliver a very heavy warhead to a target. Remember that a fission bomb uses a lump of the most dense materials found on Earth. Uranium has a density of 19,050 kg/m3. Steel, by comparison, has a density of about 7700 kg/m3. Of course, you're not taking up too much uranium, or plutonium, depending on the flavour of bomb you've made, but a nuclear warhead is still a much heaver than a conventional explosive.
Let's eliminate the possibility of multiple warheads. There is nothing low-tech about making multiple warheads, cramming them on top of the same missile, and then having each fall on target. Remember, the sheer cost of a nuclear warhead is such that a poor nation like North Korea is not going to waste any.
What of decoys? They are low-tech, right? Not really. First, they have to approximate the weight of a real warhead. Any significant difference means that they will trace measurably different trajectories through the atmosphere, differences that a missile defense system could use to spot the target.
So two heavy dummies with one real warhead? Now you've tripled the size of the payload. That means a larger missile, more fuel, and a bigger target for other anti-missile systems designed for boost phase interception. A bigger missile also means more difficulty in hiding preparations from spy satellites and other surveillance systems.
And that's just for two decoys. How many decoys would be needed to overwhelm the missile defence system? Three? Five? Ten?
Instead of one missile with a mix of decoys and a warhead, you could use multiple missiles, I suppose. But they would have to fly in close formation to actually present a single target with multiple subtargets to a missile defence system. Not likely.
But back to a single missile and the low-tech decoys. There is the question of deployment. The missile has to follow a specific trajectory to land the warhead on the target. If you start ejecting decoys, you have a problem of deflecting the real warhead (conservation of momentum comes into play when you take a single object in motion and cause it to split into two objects in motion). There has to be a delicate balance of decoys coming off in such a way as to avoid perturbing the path of the warhead, while at the same time staying close enough to the real warhead to present themselves as legitimate targets for the missile defence system to consider in the short time it has.
The funny thing is, and this is just my speculation, the delicate balance that has to be achieved is just as likely to result is a wonderful formation of the warhead in the centre of a circle of symmetrically released decoys. And the difficulty in picking out the warhead in this pinwheel arrangement is...what?
To make such a system work, you need to test and test. The US is, of course, watching the tests with its vast array of land-, sea-, air-, and space-based sensors, collecting data on how the missile and all it's constuent parts (booster, warehead, and decoys) perform, all the while you are on the receiving end of immense diplomatic pressure with each test you execute. I'm not sure you could test such a system enough times to work out the bugs before being preemptively attacked.
But let's say you've got your gargantuan missile, with 80% of the fuel transporting inert decoys, and the rest for the one real missile. You've got the decoy deployment problem licked. You've managed to test enough without being preemptively attacked. Missile defence has already worked. It has forced the enemy to expend vastly more resources (financial, technical, material, and diplomatic) for little return. All that for a missile that might not even reach the target. The prohibitive cost of attempting to defeat a missile defence system will reduce the number of potential enemies. Countries that only a few decades ago thought to one day join the ballistic missile club will now focus on real low-tech ways of causing trouble.
But don't take my word on how tricky it is to make a decoy system that actually works. Check out this patent. Radar-absorbing materials, antenna arrays -- nothing low-tech here.
Sorry, Dr Suzuki, but there is no cheap and easy way to defeat missile defence. There is nothing low-tech about the means you seem so eager to see the enemy use to threaten the West.
The real low-tech weapon is a madman with a bomb belt or a truck full of fertilizer, hoping to die a martyr for his god while causing the deaths of hundreds or thousands of civilians. Ill-informed speculation like yours that criticizes defence against the enemy only encourages him. Perhaps you could use your training as a geneticist to see if there is something organically wrong with this sort of person. Leave the missile stuff to the guys who apparently know how to make it work.
