TAIPEI --- China fired a “carrier killer” anti-ship ballistic missile (ASBM) into the South China Sea on Wednesday (Aug. 26), the day after the U.S. sent a U-2 aircraft to spy on Chinese military exercises.
China's action has already drawn the ire of Japan, undoubtedly increases tensions in the region, and raises the question: Just how advanced is this newly developed Chinese weapon?
Most ballistic missiles reenter the atmosphere at around Mach 8 to Mach 15, at an altitude of 50 km, depending on the reentry angle. Due to increasing air resistance in the dense region of the lower atmosphere, after it survives the maximum Q heating period at an altitude of around 15 to 20 km, the missile reduces its terminal speed to around Mach 2 at 3 to 5 km altitude, depending on the shape of the warhead.
Therefore, the target acquisition and control response time during the final phase is relatively short. Subsequently, a thruster system may be added to an ASBM, such as DF-21D, to increase its terminal speed and maneuverability, so that it will not be easily intercepted by ground defenses.
Additionally, even if the People's Liberation Army's (PLA) new ASBM has a smart warhead design, it will not be able to "see" its target during the reentry phase due to ionization blockage. Only once it slows down in the lower atmosphere can it start searching for its target, which is not too different from an air-breathing platform at this stage.
Therefore, a final speed of more than Mach 2 for the DF-21D's warhead is the maximum. This allows the ASBM enough time for target acquisition and avoids being intercepted.
If the incoming DF-21D was detected at 80 km altitude, assuming a reentry speed of Mach 10 and a subsequently reduced speed of Mach 2 at 5 km altitude, at least 30-plus seconds will have passed before impact. During this time, an aircraft carrier sailing at 25 knots will have traveled at least 375 meters.
A Nimitz-class carrier’s dimension is 330 m x 80 m. That means, even if China’s reconnaissance assets were able to determine the location of a US carrier, it will have sailed outside of the designated impact area. (end of excerpt)
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