Friday, March 03, 2006

Overestimating the Missile Threat

Rowan Callick wrote an article entitled "China's Missile Threat 'Unstoppable'" in yesterday's The Australian claiming
The balance of terror across the Taiwan strait[...] gives China the capacity to pulverise and close down the island but not yet to invade it.
Readers of this blog (especially this post) know that China's ability to "pulverize" Taiwan is often overestimated, as it is in this article. I do, however, agree with his characterization of China's inability to invade.

Let us examine his supporting evidence:
China is capable of deploying several hundred transportable short- to medium-range ballistic missiles within a few days
With the caveat that the number of missiles deployed does not equal the number of missiles hitting their targets, I would agree.

...which could take less than five minutes to reach targets in Taiwan...
True, but not particularly relevant unless he is trying to claim that the launch sites are too close to Taiwan for Taiwan to mount an effective missile defense, an unlikely claim since it would take days to deploy them by his own estimate.

...each destroying an area of about half a city block.
If you will pardon a Clintonian moment: That depends on what your definition of "destroy" is. Or "city block" for that matter. I won't quibble, but rather clarify this point. He assumes, as I did in my own analysis of China's missile threat, that a missile will destroy all within its blast radius--a reasonable assumption if the buildings are not hardened to protect against such a blast (as many military installations surely are) and partial destruction is good enough. The lethal radius of a CSS-6 or CSS-7 is approximately 60 meters if a conventional high-explosive warhead is used, as it likely would be if the target is an urban area (a nuclear blast would obviously be a completely different situation). A radius of 60m would cover an area of 11,309m (2.79 acres). According to Wikipedia, a city block can vary from one acre to ten, so it seems his assertion, if caveated with some reasonable assumptions, is certainly reasonable.

Leading strategic expert Hugh White, a professor at the Australian National University, said yesterday that China had overtly built up its capacity to between 600 and 700 missiles to make a political point - that it would not tolerate any move by Taiwan to declare itself independent.
Reading political points into military build-ups isn't always safe, but I find this reasonable.

No missile defence system could stop them, because the numbers were so great, Professor White said. "And missile defence is a raw numbers game."
The professor is correct that Taiwan will be not be able to stop every missile, especially since at present only the northern half of the island is protected by Patriot missiles (to the best of my knowledge). Taiwan can use its Patriots to attrit those incoming missiles, reducing their destructive capacity. Lets play the "raw numbers game." My calculations of the subject tell me that accounting for mechanical malfunctions (a modest 10%), missile defenses (50% as a ball park estimate, until Taiwan runs out of missiles), and strategic reserves (1/3 seems to be the rule), about 320 missiles will hit their targets.

"The number of Chinese missiles gives Beijing a lot of political and strategic flexibility," Professor White said. "It could, for instance, fire off 20 missiles and say, 'What do you think of that?' - leaving a lot of rounds in its locker.
The problem with this is one of accuracy that is further elucidated in the following sentence:
And if China did decide it wanted to take even stronger action, it could target power stations and airstrips and ports and army barracks, and could stop Taiwan functioning for awhile."
Taiwan probably wouldn't be overly intimidated by attempts to hit specific buildings, because they would either miss the target or be so inefficient as to demonstrate the missiles' impotence. With a circular error probability of 200-280 meters, it would take 44 CSS-6s or 23 CSS-7s to destroy a target with 75% certainty, which doesn't seem to be particularly intimidating to me. Using between one out of every 30 of your missiles (or 1/15 with the less accurate missiles) to have a three-in-four chance of destroying one building won't scare anyone into submission. If China has upgraded all of its missiles with GPS-guidance systems, a technology China is rumored to be deploying on its most advanced missiles (NOT all of them), China could reasonably expect to destroy 240 non-hardened targets with its 320 missiles that reach their targets or 461 targets if no missiles were held in reserve. Once again, not particularly devastating and certainly not enough to "stop Taiwan functioning."

The author, or the professor guiding him, seems to believe that every missile China launches will hit its target. That is not a reasonable assumption. Let's hope that China is not as prone to miscalculation.