Groton - The Navy awarded Electric Boat an additional $22.5 million to continue developing the common missile compartment for a new class of ballistic-missile submarines to replace the Ohio class and the United Kingdom's Successor ballistic-missile submarine, General Dynamics announced Friday.

EB will procure and test the equipment that will be used in the production of the common missile compartment.

The funding is part of a five-year, $1.85 billion contract, which was initially awarded in December 2012 and tasked EB with the research and development work for the Navy's next-generation ballistic-missile submarine. Construction is scheduled to begin in 2021. The potential value of the overall contract is $2.9 billion, according to GD.

This work will involve EB's engineering and design force, which includes more than 4,000 employees.

U.S. Rep. Joe Courtney and U.S. Sens. Richard Blumenthal and Chris Murphy said the contract is good news for EB and Connecticut's defense industry, especially during challenging economic times.