China's DF-21 and DF-15 ballistic missiles use inertia plus gyroscope guidance at the middle course, and as a result the flight trajectories are quite inflexible. Even if new optical and radar image guidance technologies are applied at the terminal course, it is still extremely difficult to quickly adjust the direction when attacking a moving target.

Suppose a DF-21M middle-range ballistic missile were to attack a U.S. aircraft carrier from a distance of 1,000 kilometers at an average speed of 7 Mach, or flying at a speed of 2,380 meters per second -- the whole course would take approximately seven minutes. Of course, because the U.S. Navy has developed the naval theater missile defense, or TMD, system, about 10-90 seconds after the DF-21M was launched, the DSP-1 infrared detection satellite would catch the signal and transmit the data through the data link to the ground-based joint tactical centre, or JTAG. The JTAG would transfer the data to the naval-based Aegis TMD system.

Almost all the Aegis Class guided missile destroyers, or DDGs, are equipped with joint tactical terminal receivers specifically designed to receive JTAG and DSP-1 satellite data. Even if no action were taken to intercept the DF-21M, the aircraft carrier could still evade the attack at full navigation speed. All of the U.S. Navy's nuclear-powered aircraft carriers have a maximum speed of 32 knots. In other words, they can move 30.866 meters each minute and 216.06 meters within seven minutes.

In line with the latest trends of the Chinese military forces, the HF sky-wave over-the-horizon backscatter radar is currently under development. The China National Electronics Import and Export Corp. has unveiled some of the technical details of this type of radar system. Documents indicate that the construction of pole-shaped antennae has been completed, and therefore at least one experimental variant of the radar system is in operation.

The transmitting and receiving arrays of the radar are respectively 200 x 100 square meters and 1,100 x 60 square meters, at an elevation of 60 degrees. This transmitting radar array can track 100 different targets simultaneously, and has a detection range of 800-3,000 kilometers. The CEIEC also introduced an HF surface-wave over-the-horizon radar, which was specifically designed to detect stealthy targets and has an effective detection range of 300 kilometers. Of course, digital image reconnaissance satellites, oceanic surveillance satellites and a variety of signal surveillance systems could also determine the approximate position of the USN aircraft carrier.

Even if the Chinese missiles could not accurately hit the aircraft carriers, shooting them in their direction would allow the Chinese military forces to impose "coercive isolation" on the U.S. aircraft carrier battle groups, keeping them out of the Taiwan Strait combat theater.

There has been speculation that China has developed sub-munitions and canister warheads for the DF-15 and DF-21. What progress has the PLA Second Artillery Force made in developing ballistic missile warheads? The answer to this question can be partly found in China's export of P12 ballistic missiles and the development of warheads for the WS-1B and WS-2 multiple-role rocket systems.

Firstly, China's military has invested heavily in developing blasting warheads, blasting cluster warheads for P12, sub-ammunition warheads, cloud blasting warheads and blasting-burn warheads for ballistic missiles and WS-1B and WS-2, all of which are capable of inflicting mass destruction upon designated targets.

Taking the sub-munitions fitted on the WS-1B as an example, the combat part of the warhead weighs only 152 kilograms; it has 475 munitions; the dispersing area of the sub-munitions is 28,000 square meters, and of course this dispersing area can be reset.

If a DF-15 ballistic missile were fitted with a 500-kilogram warhead, the total number of sub-munitions could be 3.2 times those fitted on the WS-1B. In other words, there would be 1,520 sub-munitions or even more depending on the different weights of the sub-munitions. If the dispersing areas of the sub-munitions were the same, that would mean a dramatic increase in unit strike intensity.

If the ballistic missiles used Russian satellite guidance at the middle course plus a certain kind of terminal guidance system, the threat that a DF-15 could pose to an aircraft carrier is very obvious. Psychologically, this would keep the U.S. aircraft carriers 600 kilometers away from the Taiwan Strait combat theater. And if China chose to launch attacks with DF-21M medium-range ballistic missiles, the so-called "coercive isolation" zone would be much broader. Even if these attacks did not seriously damage the aircraft carrier itself, the sub-munitions assault could destroy the radar, command and communications systems of the aircraft carrier battle group and force it to withdraw from the battle.

If a cloud-blasting warhead were used, the 90-kilogram munitions would have a lethal radius of 70 meters and overpressure lethal radius of 50 meters, while the 500-kilogram warhead would have a lethal radius of 388 millimeters and overpressure lethal radius of 277 meters. Using a blasting-burn warhead, the 70-kilogram combat load would have a lethal radius of 70 meters, and an effective radius of dispersing killing greater than 70 meters, whereas the 500-kilogram warhead's lethal radius and effective radius of dispersing killing could be as broad as 500 meters.

(The author if editor in chief of Kanwa Defense Monthly.)

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