A Chinese Type 093 class SSN (nuclear attack sub) was recently seen moored at their new naval base on Hainan island. This base, just north of Vietnam, must make the Indians nervous, because more and more Chinese warships are showing up in the Indian Ocean. It was only a year ago that China confirmed, as many suspected, that the first Type 093 boat entered service in December, 2006. Officially, that was a secret, and Chinese nuclear subs don't go to sea much, so it's difficult to tell if new ones are actually in service, and not just tied up at a pier for further work after launching. But now the 093 boats are obviously being moved south, and maybe into the Indian Ocean as well.
The Type 093 class SSN looks a lot like the three decade old Russian Victor III class SSN design. And the subsequent Type 94 SSBN (ballistic missile carrying nuclear powered boat) looks like a Victor III with a missile compartment added. Taking a SSN design and adding extra compartments to hold the ballistic missiles is an old trick, pioneered by the United States in the 1950s to produce the first SSBNs. The Chinese appear to have done the same thing with their new SSN, creating a larger SSBN boat of 9,000 tons displacement. Priority was apparently given to construction of the 094, as having nuclear missiles able to reach the United States gives China more diplomatic clout than some new SSNs. The first 094 entered service about a year ago.
Having already sent the first two new, 7,000 ton, 093 class SSNs to sea, China was apparently underwhelmed by their performance. Not much more is expected from the 094s. The 093s are too noisy, and have a long list of more minor defects as well. This may mean 2-3 093s will be built, while more resources will be diverted to the next SSN class; the 095. The Type 093 and Type 094 were both over a decade in development and construction. Work began on the 094 class in the 1990s. For years, all that was known was that the Chinese were having technical problems with the new design. The 094 is a modern SSBN, using technology bought from Russia, plus what was developed by the Chinese in their earlier nuclear submarine building efforts. The Chinese have had a hard time building reliable nuclear subs, but they are determined to acquire the needed skills. You do that by doing it, and eating your mistakes. U.S. intelligence experts believe that China is building a class of five Type 94s.
Google Earth images of China show underground hangers for aircraft at an airport outside the city of Le Dong, on the southern island of Hainan (near Vietnam). For nearly five years now, commercial satellite photos have been revealing details of a military buildup on Hainan. The most obvious example of this is the submarine base that China was building at Yulin, near Sanya. The base has underground docking facilities for nuclear and diesel-electric subs, created by tunneling into coastal hills.
Rumors of such a base began circulating after 2002, apparently once locals began noticing all the construction activity, and the tight security around the site. The underground facilities not only protect the boats from air or sea based attack, but enable maintenance and modifications to be done in secret. Same deal with the airport tunnels, which are also visible to anyone passing by on the ground. But there's nothing as compelling as pictures.