National Harbor, Md. — The Navy is modernizing its arsenal of Trident II D5 nuclear missiles in order to ensure their service life can extend for 25 more years aboard the Navy’s nuclear ballistic missile submarine fleet, service leaders said.

The 44-foot long submarine-launched missiles have been serving on Ohio-class submarines for 25 years, Vice Adm. Terry Benedict, director of Strategic Systems and Programs said April 7 at the Navy League’s Sea Air Space exposition.

The missiles are also being planned as the baseline weapon for the Ohio Replacement Program ballistic missile submarine, so the Navy wants to extend their service life for at least an additional 25 years, Benedict said.

“Ohio Replacement will be in service until the 2080s, so a submarine missile launching capability must last that long,” he said. “The D5 system has served us well. However, 25 years is about the max of what we planned for the system.”

Benedict said the Navy has been working on technical upgrades to the existing Trident II D 5 in order to prevent obsolescence and ensure the missile system remains viable for the next several decades.

“We’ve modernized the guidance system by replacing two key components due to obsolescence – the inertial measurement unit and the electronics assembly,” Benedict said.

Under the U.S.-Russia New START treaty signed in 2010, roughly 70-percent of the U.S.’ nuclear warheads will be deployed on submarines, Benedict explained.

The 130,000-pound Trident II D5 missile can travel 20,000-feet per second and reach ranges of 4,000 nautical miles, according to Navy figures. The missiles cost $30 million each.

The Navy has recently acquired an additional 108 Trident II D 5 missiles in order to strengthen the inventory for testing and further technological development.

“We’re continually upgrading and testing new aspects of the missile system. We’ve had 148 successful test flights of the missile,” said John Daniels, spokesman for the Navy’s Strategic Systems Programs.

As part of the technical improvements to the missile, the Navy is upgrading what’s called the Mk-4 re-entry body, the part of the missile that houses a thermonuclear warhead. The life extension for the Mk-4 re-entry body includes efforts to replace components including the firing circuit, Benedict said.

The Navy is also working with the Air Force on refurbishing the Mk-5 re-entry body which will be ready by 2019, Benedict said.

Benedict said the Mk-5 re-entry body has more yield than a Mk-4 re-entry body, adding that more detail on the differences was not publically available.

The missile also has a larger structure called a release assembly which houses and releases the re-entry bodies, Navy officials said. There is an ongoing effort to engineer a new release assembly that will work with either the Mk-4 or Mk-5 re-entry body.

The Trident II D5 also arms the United Kingdom’s Vanguard ballistic missile submarine. In fact, the U.S. and UK are collaboratively working on a common missile compartment for their next generation SSBNs, or ballistic missile submarines.