Don't shoot shoot shoot that thing at me
June 3, 2007 8:42 PM   Subscribe

What is involved in "aiming" an ICBM?

I guess I've always wondered about it, but this article recently posted to the blue brings it back to mind. What exactly is involved in "training nuclear missiles on European targets?" It seems to me that good design would allow for easy changes to the missle's target - enter latitude and longitude then press red button, etc. Does this refer to setting a default location that would be hit if it wasn't overridden or is there significant effort involved in changing the missile's target? Is saying that a missile is trained on target X just posturing?
posted by sanko to Grab Bag (10 answers total) 1 user marked this as a favorite
 
My understanding is that it's mostly just posturing. There might be a bit of procedure in it; maybe a missile battery has a default target that it's trained at, but you're correct in thinking that most modern missile systems can be aimed, up until right before launch, pretty much anywhere.

The only good thing it might have is in the case of an accidental launch. (I.e., if the missile were to be accidentally launched, it would detonate over the ocean, rather than over an enemy city.)

From a presentation by the Brookings Institution:
The de-targeting agreement with China announced with great fanfare by the White House over the weekend will have exactly zero impact on U.S. operational nuclear posture. We stopped actively targeting China in 1982. As for the 13 Chinese ICBMs that the CIA claims are targeted on the United States, we have no way of knowing if or how this agreement will be implemented. If China's ICBM targeting systems are anything like ours or Russia's, changing from one pre-programmed target set to another is about as easy as switching channels on a television with a remote control.
(Emph. mine)

In the case of nuclear submarines and other mobile launchers, there's not really any way to pre-target them anyway, since the trajectory they need to follow at launch needs to take into account their start position -- so they are always going to be 'targeted' at the time of launch. It's just a matter of when the target is communicated to the people who actually 'press the button'; whether they know it in advance, or whether it comes as part of the launch order.
posted by Kadin2048 at 8:56 PM on June 3, 2007


former submariner here. it was my understanding that the warheads that may or may not have been on the ship may or may not have been set to somewhere in the middle of the ocean, just in case of the unlikely event of an accident causing a launch.

and also, what kadin and sanko said.
posted by ArgentCorvid at 9:29 PM on June 3, 2007


The warning is political posturing about intended targets, not actual targeting data. "If you shoot us, we'll shoot X, Y and Z."
posted by frogan at 9:39 PM on June 3, 2007


Here's some good information on how the National Strategic Target List was implemented in the 1970s; Googling around it appears that TRW has a contract for programming the targets into the missile systems. I have no idea whether any information on Russian procedures exists, but some of the US procedures can probably be extrapolated.
posted by rolypolyman at 10:20 PM on June 3, 2007


See the wikipedia article here for more info.

Essentially these are ballistic missiles, meaning they are set on a particular path which will cause them to land at the aim point. Some systems allow for some level of mid-course correction, but aiming a missile involves setting it from the moment of launch on a path which will hit the intended aim point.
posted by Ironmouth at 10:28 PM on June 3, 2007


Even more detail here, an article on inertial guidance. Usually a gyroscope (or lately, a sphere floating in beryllium) will measure changes from a known state (where the missile was launched from). The missile's thrusters and fins are then manipulated by a control system to assure that it stays on a predetermined track towards the target. Modern ICBM's can hit within 275 meters of their aim point. When the missile is carrying a warhead of 250 kilotons power, the aiming is essentially perfect.

The key is that the missile has to operate without outside guidance--if GPS satellites are hit or a ground control bunker was destroyed, a missile without its own internal guidance could miss--not the result one wants if the goal is to deter a nuclear attack.
posted by Ironmouth at 10:40 PM on June 3, 2007 [1 favorite]


There was a decent article by Slate's Explainer about this a few years ago.
posted by inkyz at 11:29 PM on June 3, 2007


You pre-target your missiles if you expect a nuclear strike before you have time to respond. If you're in an alert posture with default targets, when the capital gets taken out and you lose command and control, the missiles are all preprogrammed. That way, they'll be properly dispersed to destroy your enemy as thoroughly as possible without any further input from anyone. (beyond 'launch!').

If the missiles aren't targeted anywhere, then they require a positive command from the government to aim them. This probably takes about five minutes, assuming they still use humans to decode messages and dual-verify like they used to. (I certainly would hope this would happen, but I can't say for sure.) If they're using computer targeting, it would take maybe a couple of seconds to reprogram the entire arsenal. But the command has to happen, and if the central control is taken out suddenly, the missiles may never launch.

Overall, this means that risk increases. If Moscow is suddenly cut off from the missile sites due to a technical glitch or, say, an asteroid strike (hardly unthinkable), a massive strike could happen without a direct order from the government to do so. This thought, rightly, scares people.

The only rational reason to have your missiles pre-targeted is if you expect a decapitating nuclear strike, so Russia is saying that they believe America is setting up to nuke them. Even with Cheney in charge, this is just stupid and political posturing. It is, nonetheless, a strong statement. It means more than the other posters are indicating.

I wonder why they feel so threatened by this system? I wonder if it's Putin going on the offensive because of the Litvinenko thing?
posted by Malor at 1:09 AM on June 4, 2007


My limited understanding of this includes a dated fact that the MX was the USA's first ICBM with terminal guidance for the 're-entry vehicle', which is what the call the warheads. That means that they had some means of assessing where they were and making corrections to the final path to target. Prior to that, it was all about burn duration on the boosters and initial trajectory. In the case of some early ICBMs, I was under the impression that burn duration in boost was based on fuel quantity as much as anything else, meaning a lot of work to change targets. Of course, in those days, non-storable propellants and oxidizers were the rule (i.e., red fuming nitric acid, LOX, and JP1.) I had friends who deployed the early storable propellant Titan 2 ICBMs (using hydrazine monopropellants) who told of a constant stream of fueling operations on the earlier ICBMs, like Minuteman. Tedious problem, huh?

Why would you do this? Simplicity. All the computational burden remains on the ground. Once fired, the missile is going to come down where impulse and direction dictate.

It's hard to describe how primitive some of the electronics were for this sort of stuff. It's also hard to describe how nasty an environment it had to live in. THe lauch silo was benign, but the rockets were exoatmospheric, meaning huge temperature differences in a short time, a brutish vibration environment, etc. Motors ignited while the rocket was IN the silo, meaning hot gasses were everywhere. Double ick! (MX actually was spit out of its silo with CO2 and its motor ignited after it cleared the silo... they were only every deployed in decommissioned Minuteman silos, as I recall and I think the've been retired?)

Point is.. in the early days, simplicity was good.

MX used solid propellant like the Shuttle boosters, and had 10 warheads on it's MIRV, and the accuracy was classified info. 275 Meters circular error probablilty (CEP) may have been what was published, but it sounds off to me by a factor of 10, which is amazing if you consider the distances involved.

One of the reasons Ivan hated MX was because of those 10 warheads. It was a first strike weapon. With so many of the warheads on so few launch vehicles, there was a national incentive to launch first. MX also was not consistent with earlier arms limitation agreements (it was mobile), and was very provocative. At the time, we were being led by a kindly, old, ignorant and stupid man named Reagan, who actually believed that one could recall a missile once launched and who advocated 'nuclear warning shots' to vaporize part of Poland, pehaps, if the Ruskies got out of hand. ( His intellectual successor is Mr. "Mission Accomplished" G. W. Bush. )

But I digress....

Even though we're now in the age of GPS, I'd doubt that any missile designer would use anything other than inertial guidance to deliver a warhead. It is accurate, simple, and self-contained.

I DO know that on tactical, non-nuclear missles, targeting info is sent at the very last second. ( I did some stuff on Sea Sparrow missiles and Standard Missile 2, years ago.) The vertical launch version of Sparrow got it's initial steering instructions about 3 seconds before launch.) From that point on, on-board seekers guide the rocket, except that there is some interaction with the launch platform.

Tactical nuclear weapons, which could include cruise missiles with small warheads, use terrain following techniques and can fly to pretty much the exact target desired. The targeting is probably one of the last things to get sent to the missile.
posted by FauxScot at 3:50 AM on June 4, 2007 [2 favorites]


There are different missiles for longer and shorter ranges. What's the point in having a larger missile with enough range to get to the other side of the world if you just want to bomb something a few thousand miles away?

Obviously guidance systems play a large role but fuel needs also play a very important role. Also if you have any basic physics experience, trajectories must be calculated before hand and not on the fly, as it were.
posted by JJ86 at 9:00 AM on June 4, 2007


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