Not_Whistlin_Dixie said:
I recall reading that the attacking ICBM can spew a lot of metallized mylar balloons which simulate the radar return of an authentic threat. This supposedly can swamp the defender at a modest cost to the attacker.
It would have 20-30 years ago, but nowadays computers are fast enough to filter them out. They don't have quite the same radar return and there is enough atmosphere about up there that they don't have the same ballistic performance anyway.
Incidentally, it appears that the current plan is to simply blast all the decoys out of the way (bursting the balloons) and kill whatever is left. Since the decoys will have effectively zero cross-range manouverability, this isn't all that hard. I've been told (although I'm not entirely sure if the guy was joking) that the material of choice for bursting them is grape flavour jelly. Turns to sharp crystals under vacuum and the grape flavour stuff is effectively invisible.
Not_Whistlin_Dixie said:
Also, that modern re-entry vehicles include multiple, independently targeted re-entry vehicles.
Yep, that's why this system is no threat at all to the Russians and won't be any threat to the Chinese when they finish modernising their arsenal in the next couple of years. However, that isn't the whole story. Back before the Russians deployed their ABM/SAM system the British nuclear weapons (at that time delivered by the V-bombers) were targetted on about 100 or so different places in Russia. The defences have cut that down so that nowadays we can take out Moscow and everything in it with certainty, but have no weapons left over for anything else. It's a wierd fact but ABM systems seem to be best at protecting things they don't directly cover.
If the US was serious about a defensive system however they'd just put nuclear warheads in their interceptor missiles. MIRVs don't actually have very much cross-range ability so a big enough explosion going off in the centre of the group of MIRVs would destroy all of them. Fallout is actually a pretty minor problem if the explosion is at high enough altitude, and "EMP" really isn't the danger it is claimed to be. However, the US doesn't need to do so and hence isn't.
Not_Whistlin_Dixie said:
If memory serves correctly, Mr. Putin was recently boasting of some sort of big breakthrough in this field.
From memory all he was boasting of was the ability of Russian RVs to manouver on the way into a target. That's nothing new - the Chevaline upgrade to the UK Polaris missiles was able to do something similar 20 years or so ago. Because of the extremely high speeds involved their manouverability is very limited and this will at best cut down the efficiency of defences - it won't defeat them completely.
Not_Whistlin_Dixie said:
I've read that the surest, easiest way to kill the attacker's ICBM is with a "booster phase" interception, when the thing is still going up, with first stage engine burning. USA is working on some type of chemical laser, carried in the fuselage of a cargo jet, as a means of achieving booster phase interception.
Yep. The problem with that is that whatever you hit the missile with has to be pretty close to the launcher. The airbourne laser has to be within something like 100 miles (depends on weather) and the various missile options have to be even closer. Say Iran decides to kick off at some point in the future - how confident would you be driving a Boeing 747 around over Iranian territory in case they launch? When it works it's great, but it isn't always possible.
On a side note, the other reason boost phase interception is so desirable is that whatever is in the missile will fall on the launching country rather than you. A nuclear device will no doubt be smashed up in the shoot-down, but if it's loaded with something like Smallpox or Sarin that's a very different matter.