Editor’s Note
This article, presented in three parts, delves into the pivotal role of data in deciphering a Chinese missile launch. Parts I and II have already been unveiled, laying the groundwork by elucidating the missile’s trajectory and the hurdles to its precision. In this segment, the author underscores the significance of continuous data inputs in scrutinizing a specific Chinese missile launch and how it aids in understanding the intricate target behaviour and the missile’s hit probability, thereby, shedding light on the strategic implications of Chinese ASBM capabilities.
The earliest successful missile in this class was the Pershing II, which the Americans deployed between 1983 and 1991. The Pershing II was a two-stage solid fuel missile with an 80-kilo tonne warhead, a range of 1700 kilometres, with a re-entry velocity of Mach 8. It had vector control fins for guidance. It had inertial guidance and radar guidance in the terminal stage, and the CEP was reportedly 30 metres. The ballistic trajectory was deliberately made manoeuvrable so that Anti-Ballistic missile systems would have a hard time destroying it. As per the open source, the Pershing II, on entering the Earth’s atmosphere, would do a ‘pull up’ manoeuvre and then scan the surface using its built-in radar and home onto the target with the help of the control fins. In any pull-up manoeuvre, the velocity reduces.
Calculations show that a Mach 8 ballistic missile entering the Earth’s atmosphere on a pull-up manoeuvre would have its velocity reduced to just about Mach 2. The Pershing II was designed specifically to hit stationary targets. It was abolished in May 1988 as part of the ratification of the Intermediate-Range Nuclear Forces Treaty. The Chinese extensively studied the Pershing II, and the DF-21D was born.
Let us now discuss the Chinese ASBM ‘kill chain’ as it is depicted on various Chinese websites. A brief description was provided in the introduction, but now a slightly detailed look is needed.
(Source: https://blogos.com/article/35397/)
According to the depiction, satellites would pick up the position of advancing American aircraft carriers and relay the data to aircraft or UAVs. The position would then be relayed to the ASBM launchers ashore, and the missile would be launched based on the information received.
So, let us look at the vital components of this ‘kill chain’. Firstly, the satellite data flow. If a satellite in polar orbit travels at speeds 7 to 8 km per second, it has a 10-minute window to pass data to the ground station. The raw data reaches the ground station and is processed. The processing time depends on the sophistication and processing power deployed. It could be days, an hour or maybe even minutes. Let us give the Chinese the benefit of the doubt that they have reduced the processing time lag to minutes. After that, the user retransmitted this data to the launchers, the aircraft or the UAVs deployed. If you increase the number of satellites, the data flow can be reduced to six to seven minutes.
These are theoretical calculations. Nobody knows the truth. The satellites have internal errors in tracking the target, their position concerning the frames of reference, and transmission losses during data transfer. The air assets data flow, whether using drones or fixed-wing aircraft, their speeds, coverage, numbers deployed, and associated data link issues on account of use of HF/VHF/UHF or satellite link, all have significant errors.
Another red herring we often encounter on the Internet is that the Chinese use Over the Horizon Targeting B (OTH B) radars for initial tracking of aircraft carriers. Let us look at the basic physics of an OTHB radar. The frequency range is from 3 to 30 megahertz. The wavelength is 100 to 10 metres. The range resolution is 20 to 40 kilometres. The bearing resolution is between two to four kilometres.
The system is heavily dependent on an accurate climatological model, which must be updated hourly. Even after that, the position you get can be off by tens of kilometres. OTH B radars are primarily used for detecting ballistic missile launches and aircraft detection, not warships. Simply not practicable. The other variation, OTH Surface wave radar, which is used for the detection of warships, is limited by physics to a range of about 180nm and, therefore, would not fit the template.
Let us now look at the actual interception calculations:
(Source: https://www.popularmechanics.com/military/weapons/a12366/how-it-works-china-antiship-ballistic-missile/)
As per open-source information, the DF-21D supposedly has a range of 1500 to 2000 kilometres. On being launched, its boost phase time is about 70 seconds, where it attains a velocity of 4km/s. Target update has to happen in this boost phase before the burnout. After that, the missile has a mid-course of 400 seconds, reaching an apogee of about 400km. No manoeuvring is possible in this phase. After that, it enters the atmosphere with a velocity of Mach 8, and the time to target is 67 seconds.
The missile is designed to do a pull-up manoeuvre like the Pershing II and open its guidance to home onto the target. At this point, the missile velocity would drop to 0.6 km/s or Mach 2. Any Aegis SM-3 equipped warship can quickly destroy the warhead as the SM-3 system can easily intercept a 3 to 5 km/s missile. More so, an aircraft carrier at a speed of 24knots after 60 seconds would have moved off by 740 meters based on simple vector analysis. The chances of hitting a moving target are absolutely slim, if at all.
So, what is the proof that DF-21D works? On 26 August 20, approximately four missiles, DF 26 and DF-21 D, were reportedly launched into the South China Sea. According to Taiwanese reports, these were unsuccessful. Out of which, one of them landed ashore! Then, we also have satellite photographs of Chinese ASBM tests in the Xinjiang desert, wherein an aircraft carrier model on a railway track is shown. Then, we have another set of satellite photos showing that the missile has hit a destroyer-sized target in the desert (12).
Calculating the trajectory of a missile to hit a target that is moving linearly on a rail track is quite different from targeting a moving target at sea, which can move anywhere in any direction. We all have read the reports on the subpar performance of standard American weapons in the Ukraine-Russia war. Here, we have an untested, unknown, futuristic weapon which claims to hit aircraft carriers out at sea. So far, there is no evidence. Theoretically, ASBMs can hit a moving target. However, the actual mechanisation of physics and the need for flawless and seamless performance of every piece of equipment in the entire network make it an extremely difficult proposition to succeed in the real world.
Rear Admiral Ajay V Bhave (Retd)
