The P-8 Poseidon is one of the U.S. military’s most advanced surveillance aircrafts. It’s been deployed to Okinawa, Japan for one main reason: to monitor China’s growing submarine fleet.
In the back of the plane, a heavily modified Boeing 737, the crew homes in on the vessel using a barrage of surveillance equipment, including radar, GPS and infrared cameras.
Further down the fuselage stand rows of tube-shaped sonar buoys that the crew can catapult into the sea and that float for up to eight hours as they track objects underwater.
This is a dummy run: Today’s target is a Singaporean container ship, and the P-8 roars by without dropping the buoys. But the aircraft is designed to hunt a far more elusive, and potentially dangerous, quarry: Chinese submarines.
Soldiers stand on guard next to a Chinese navy nuclear-missile submarine at the Qingdao base in eastern China. Yin Haiyang/Color China Photo/Associated Press.
It is one of six P-8 jets the U.S. has sent to its Kadena air base in Okinawa since December as part of its strategy of “rebalancing” toward Asia, deploying more military and diplomatic resources to the region in response to China’s growing firepower and assertiveness.
Okinawa also sits next to one of the main chokepoints, the Miyako Strait, that U.S. officials say Chinese subs have used in recent years to enter the Pacific. “If we have history, if there’s a trend of them getting from point A to point B, then we’ll exploit that,” says Cmdr. Pennington. He calls the P-8 a “game-changer,” despite some criticism in the U.S. of the $34 billion the Pentagon is spending on developing and buying the planes.
The jet is designed to replace the old propeller-driven P-3 Orions in Okinawa that were built to hunt Soviet subs and have been flying since the 1960s. The P-8 can drop and monitor up to 64 “sonobuoys,” twice the P-3’s capacity.
A U.S. Navy P-8 Poseidon flies over the Western Pacific, one of six deployed to Okinawa to help anti-submarine forces in the area. Dominic Nahr/Magnum for The Wall The new aircraft can also reach a target up to 1,200 nautical miles away—about 300 miles further than the P-3—and remain on station for four hours before flying home. “That allows us to get to the southern parts of the South China Sea. We do that quite often,” says Capt. Mike Parker, Commander of the U.S. Navy’s Task Force 72, which conducts marine reconnaissance in Asia. “We want to be able to locate those submarines and if needs be, let them know that we know where they are.” The P-8s’ operations can bring them into confrontation with Chinese forces. In August, the Pentagon said a Chinese jet fighter had flown dangerously close to a U.S. P-8 during an interception near Hainan island, site of one of China’s submarine bases. China’s defense ministry publicly said its pilot flew safely and demanded that the U.S. cease surveillance operations near its base. But the U.S., which says those operations are in international airspace, is taking steps to allow the P-8s even more time over the South China Sea, by negotiating agreements with surrounding countries to use their airfields as launchpads for sub-hunting flights, say people familiar with those discussions. The P-8’s additional range—and the importance of such regional launchpads—were both clearly demonstrated when the aircraft joined the search for the missing Malaysia Airlines flight MH370 earlier this year. As during that search, the U.S. also envisions working more closely with other countries in the region that are upgrading their anti-sub aircraft fleets. The plan is for the P-8s to work in conjunction with Triton aerial drones, the first of which is expected to be deployed to the Pacific island of Guam in 2017, according to senior U.S. Navy officers. 
ENLARGEThe P-8's crew can catapult tube-shaped sonar buoys from the jet that then float as they listen for submarines underwater. Dominic Nahr/Magnum for The Wall Street Journal. Yet, for all their extra speed, range and sonar buoys, the P-8s rely on the basic sub-hunting techniques of the Cold War. Part science and part instinct, undersea warfare is rooted in the complex physics of the ocean. Neither satellites nor radar can detect objects underwater. The most effective way to find a sub is still by using sonar equipment to listen for its engine, or to bounce sound signals—or “pings”—off its metallic body. Submariners avoid detection by keeping their engines quiet, avoiding outgoing communications and remaining below the “thermal layer”—between warmer water near the surface and colder water below—that deflects sonar pings. The P-8s also work with satellites that monitor submarine bases, with undersea microphones that listen for passing subs and with surface ships that tow large arrays of sonar equipment. Once over a potential target, the P-8 drops its sonar buoys in a grid, then circles overhead gathering the data that they transmit. Those data are displayed on a screen in the back of the plane and analyzed by specialists like Naval Aircrewman Operator 1st Class Robert Pillars, who is trained to recognize the acoustic signature of a Chinese sub. “If there’s a submarine there and it’s within range of a sonobuoy, I’ll find it,” he says, standing in the back of the P-8 after its sortie. “It’s kind of an art because you can go after the same boat twice and it’ll sound different both times. It’s about training and instinct.” Until recently, finding Chinese subs was relatively easy. Many were old diesel models, which spotters could find when they surfaced every few hours to “snorkel”—run the engines that charge their electric batteries. The reactors on China’s early nuclear subs were even noisier, say Western naval officers. In recent years, however, China has made advances in quieting its diesel subs, many of which use technology that lets them run their engines for long periods on liquid oxygen without surfacing for air, say Chinese and Western military experts. In 2006, U.S. officials were stunned when a Chinese diesel-powered Song-class sub surfaced within torpedo range of a U.S. aircraft carrier, the Kitty Hawk, without being detected in advance, say U.S. officers briefed on the incident. “China’s now got some very quiet subs, and that makes our job more challenging,” says Capt. Parker. “If you’re not very good, you won’t find them.” Since the Kitty Hawk incident, the U.S. has stepped up anti-sub patrols. But China has also deployed large numbers of ships, aircraft and missiles that appear to be designed to prevent U.S. forces from monitoring waters near its coast, say Chinese and Western military experts. In 2009, five Chinese ships surrounded the USNS Impeccable—one of the U.S. Navy’s most advanced anti-sub ships—in international waters near a submarine base on Hainan. Last November, China suddenly established an air-defense identification zone over the East China Sea and warned of unspecified “defensive measures” against aircraft that entered without identifying themselves in advance. Many U.S. officials now fear that China may declare another zone over the South China Sea—although Beijing has said repeatedly in recent months that it has no such plans. China’s ultimate goal, those officials believe, is to turn the South China Sea into a safe haven for its subs much like the bastions from which Soviet subs operated in the Cold War. If Chinese aircraft and surface ships can keep U.S. anti-submarine forces at bay, that would let China’s subs patrol safely near its shores and slip unnoticed into the deeper waters of the Pacific. “That would be like the Cold War,” says Capt. Parker. “It’s what the Soviets used to do.” 