Sure, the missile is 21 meters long. But the boost stages comprise about 90% of that length, and are gone within the first 5 minutes of flight. For the other 25+ minutes, it’s mostly drifting, with the post-boost vehicle making tiny course corrections for a few more minutes in the ascent (possibly even “faking” towards Target A and then changing course towards Target B). Once the reentry vehicle is spun up and released, it free-falls up to apogee and then back down to the target. Not much heat signature to track until it begins to reenter.
The reentry vehicle is very small - a cone that has roughly the height and girth of a professional (American) football player. It’s moving very fast, and probably traveling in formation with a few decoys, jammers, chaff, and other distractions. Imagine trying to hit a baseball pitched to you in a blizzard, while five or six guys stand near the pitcher and throw snowballs to the catcher at the same time.
The length really is the primary factor anyway. Nobody would try to intercept a missile from the side; your “best” chance would be to aim along the path of flight. So you’ve got one missile flying along at 15000 mph aiming to hit a six foot wide target that’s also traveling at 15000 mph.
Something that made the comet impact easier was that the Deep Impact probe was in the same trajectory as the comet. The collision was attained by the speed difference of the two objects. The Comet merely over-took the probe, kind of like a really bad rear-ender.
This is a lot easier collision to manage than if they were trying to cross paths like an ABM and an ICBM.
The only nations with nuclear weapons that have a beef with the US are Iran and North Korea (though there’s some doubt if they actually have any nukes yet or not). Neither one of them is currently capable of lobbing a nuke at the US via an ICBM. NK supposedly is close to having the ability, but its doubtful that even if they actually do have a missile with the necessary range, that it could be successfully fired. Given that neither of those two nations can do it, then there’s really nothing for us to worry about, so far as ICBMs or submarine launched missiles go.
And it would therefore be perfectly reasonable for Japan to consider implementing a missile-defense system. Reasonable to consider it, though not necessarily to do it: That would depend on the likelihood of an attack, the cost of the system, and the expected likelihood that the system would work.
But it’s completely unreasonable for the U. S. to consider such a system, because there are no threats to the U. S. which would be addressed by such a system even if it worked, and it distracts attention away from other much more plausible threats.
Believe me, if you don’t like the thought of Japan getting nuked, I’m much less pleased.
Their accuracy isn’t great yet, but they’ve launched a missile over Japan in the past. Coming from a certified crazy country, that’s not something to be taken lightly.
I don’t believe that the current method is a good approach, but something must be considered. IIRC Japan and the US are working on a joint missile defence program separate from the Son of Star Wars approach.
I know, but its still a peeve of mine when someone points out that a space based laser or ground based missle system won’t be sniffing around freighters in mid atlantic or pacific. That’s what the Navy, Coastguard, Intelligence services will be doing.
Its sort of liked doing away with police speed traps because they do nothing for burgularies. I know, its probably not the same sort of thing and I realise SDI is a bit far fetched for decades if not longer, but when there’s ample evidence that its a bit of a dead donkey why mention shipboard nukes?
[indent]The ABL is designed to detect and destroy theatre ballistic missiles in the powered boost phase of flight immediately after missile launch. The aircraft loiters at an altitude of 40,000 feet.[/indent]The ABL is a theater defense systemn designed to operate on a battlefield in close proximity to the launch site, knocking out the missile in boost phase by firing at the booster, rupturing the case and igniting the propellent. It is not effective against terminal-phase RVs and is a whole 'nother animal as compared to strategic defense like KEI and GMD. In order destroy an ICBM, you’d have to have a plane up at the right time and within line of sight of the booster trajectory; difficult, if the launching party is, say, China or India.
The point of that line of argument is that even if we did have an effective way to respond to a strategic attack (a massive flight of missiles headed to every destination to which Northwest flies in the continental US) it would merely cause a nation or party interested in a terrorist attack to pick a different vector, even assuming the option of a missile was possible to begin with. Sailing a weapon in on a boat is trivial; boats enter and leave American waters regularly, usually without so much as a by-your-leave. Requirements of registration with port authorities and Coast Guard approval are difficult to enforce. Shipping one over as, say, a shipment of electronics or Bebe shirts or rice is almost as easy. And as Tuckerfan astutely notes, the parties most interested in potentially doing us harm lack the reliable capability to send one via air, anyway.
In the case of Iran and North Korea, though, I’d personally be more concerned about living in Syria or South Korea (or Japan), respectively, than I’d spend time worrying about their striking at the US. 'Course, that’s a reasonable assessment, and neither of those nations is known to be operated by reasonable leadership.
Well, there’s Canada…
Whenever this discussion comes up I can’t help but get the urge to quote from the film Wag The Dog:
Stanley Motss: The President will be a hero. He brought peace.
Connie Brean: But there was never a war.
Stanley Motss: All the greater accomplishment.
Not a debate on the feasibility–but rather a GQ of why we could hit something moving fast in one instance and not another; both given modern computer processing power.
We did have successful tests knocking down very fast stuff–and a large part of that is probably because of modern computer processing power. So things have improved from what the OP remembered on that front.
But, when we’ve sealed off all the ports and harbours, then you’ll be wishing you had your ABM, won’t you!
Seriously though, I get all the points made, its just a peeve of mine that the obvious fallacies of any sort of SDI at the moment seem to be enough by themselves without having to discuss alternative methods of warhead delivery.