Thursday, December 17, 2015

Stalking Air Craft Carriers

"Flood tubes 2 and 4!"

Recent Sino submersible stuff going on around American aircraft carriers begs the quiz:

Assuming a Chinese submarine is able to sneak into position to attack the American carrier, what is the likelihood of its ordnance achieving critical hits?

At this juncture, it is appropriate to establish the terms “mission kill” and “platform kill.” Simply put, platform kill occurs when the ship attacked is sunk, while a mission kills involves the ship being unable to perform its primary task(s). The raison d’être of the aircraft carrier is its air wing and the ability to conduct flight operations is indispensable in this aspect. Making its flight deck inoperable would be one way to bring about the mission kill of a carrier. Another would be to reduce the ship’s speed and maneuverability, as it must be able to maintain a steady course and speed for the launch and recovery of aircraft. For America’s adversaries, achieving a mission kill of its carriers might just be enough for a major military and political victory.

The Chinese submarine can attack the American carrier with either its torpedoes or, if it has them, anti-ship cruise missiles (ASCMs). A hit from the former is arguably the more damaging of the two. Indeed, Howarth contends in China’s Rising Sea Power (p. 99.) that “(l)arge armored warships are inherently difficult to sink or disable with hits above the waterline, unless the missiles manage to penetrate a vital area of the ship such as its magazine or combat information center.” Then U.S. Chief of Naval Operations Gary Roughhead took the same line when he maintained in 2011: “I would argue that you can put a ship out of action faster by putting a hole in the bottom [with a torpedo] than by putting a hole in the top.”

A torpedo hit, which is below the waterline, will create a hole in the carrier’s hull and this might slow the ship down and/or make it list. A wake-homing torpedo – a weapon owned by China – is even more dangerous as it tracks the wake created by the target and hits the propeller system or its vicinity upon impact. This is an outcome that would adversely degrade the carrier’s speed and mobility – two factors that affect its ability to conduct flight operations. All in all, attaining torpedo hits on an American carrier has a decent chance of bringing about its mission kill – if the resultant damage is not properly contained.

There have been no instances in the postwar era of American warships being hit by torpedoes. However, there were a few incidents of fires involving USN assets; bearing this in mind, it can perhaps be argued that in any future conflict, the U.S. Navy would be more used to handling hits topside rather than those below the waterline.  To illustrate, the PLAN has the Type 53 torpedo that is with armed a 300 kg warhead. It also has the Type 65 wake-homing torpedo that has a 450 kg warhead. All in all, American ship crew might not be able to handle a torpedo hit as well as one from a missile considering the USN’s lack of experience in dealing with the former; in this light, the submarine-launched torpedo constitutes a genuine threat to the U.S. carrier.

Modern Chinese boats like the Kilo and Shang have six torpedo tubes each and this means usually a maximum of five ASCMs will be loaded into the tubes and fired. This is because it is typical, indeed prudent, for the submarine to have at least a torpedo loaded and ready for firing in case any sub-surface threat appears. A salvo of a handful of missiles, though dangerous in its own right, hardly constitutes the saturation attack which the Aegis air-defense system on the carrier’s escorts are conceived to handle.

There were a number of serious fires involving U.S. flattops in the post-war period and it is reasonable to infer from these blazes what could be the likely aftermath of ASCM hits on a modern carrier. This is because these fires bear a similarity to ASCM hits in that both involve the ship’s topside. The conflagration that engulfed the USS Enterprise in January 1969 is often cited as evidence of the U.S. supercarrier’s ability to take punishment and still remain operational. The fire occurred when nine 500-pound bombs were set off on its flight deck and the explosive power of the blast was said to be equivalent to that of six Russian cruise missiles (Howarth, China’s Rising Sea Power, p. 99.). In spite of heavy casualties – 27 dead and 300 wounded – the catapults and arresting gear of “Big E” remained relatively undamaged, and she resumed flight operations within hours. In other words, the ship sustained the equivalent of half a dozen ASCM hits, without a mission kill.

However, it must be stressed that this extrapolation does not take into account the fact that at the point of impact, the missile could be moving at supersonic speed. Indeed, the Chinese submarine-launched YJ-18 ASCM has a terminal speed of between Mach 2.5 to 3. The question is thus: “Would the kinetic energy sustained from travelling at such high speeds allow the missile to penetrate the carrier’s armor and hit vital spaces like its magazines?” Witness the sinking of HMS Sheffield during the Falklands War, where a subsonic Exocet penetrated the destroyer’s hull but did not detonate. Nevertheless, the missile caused fires that doomed the ship.

Summing up, the preceding analysis has shown that current PLAN submarines, because of the tyranny of geography and their operational and technological deficiencies, would have considerable difficulty finding and tracking U.S. carriers in the event of a conflict in the western Pacific. However, exogenous elements like targeting information provided by ocean-surveillance satellites could potentially alleviate the shortcoming. And if the Chinese submarine does get to shoot at the U.S. flattop, doing so with torpedoes rather than anti-ship missiles might offer a better chance of mission success.


Steven Nicovich said...

That's assuming during a conflict that a P-8A or USS Seawolf/Virginia/Los Angeles class submarine (always part of a carrier group) doesn't find a Chinese sub first and sink it.