While the new Russian Bulava SLBM (Sea Launched Ballistic Missile) continues to fail flight tests, its U.S. counterpart, the much older, 58 ton, 44 foot long Trident II, has not failed to launch successfully in twenty years. Since 1989, none of more than 120 test launches have failed. The Trident had two failures during its 49 development test launches, but since then, it has been the most reliable SLBM to ever enter service. Each Trident II costs about $65 million, and entered service in 1990. Some of them are fired every year, to insure that the current configuration (of hardware and software) still works as it is supposed to.
In contrast, the latest Russian SLBM, the Bulava, is having an awful time in testing. While the overall (out of over 5,000 of them) failure rate for test launches of Russian rockets is eight percent (and the U.S. Trident I had a failure rate of 13 percent while in development), more than half of Bulava's development test launches have failed. The 48 ton, 56 foot long Bulava costs about the same as the Trident II. Russian leaders insist that the Bulava will eventually succeed. But insiders say that, if you use the same criteria for a successful Trident II launch, only one of the 13 Bulava tests was a success.
While the Bulava is less reliable, it is using more modern components than the Trident II. The guidance system for the Trident II uses 1980s era electronics, and is becoming impossible to maintain. That's because many key components are not manufactured anymore, and supplies of these spares are running out. So the U.S. Navy is developing a new guidance system, using current components, and a design that makes it easier to substitute future, and more powerful, components for those that become obsolete.
Currently, 12 of the 14 American Ohio class SSBN (ballistic missile carrying nuclear subs) carries the Trident II D2, and the other two will receive that missile the next time they are in for refit. The Trident II is expected to remain in service for the life of the Ohio class boats, which means another two decades of service.