General Dynamics Electric Boat, a subsidiary of General Dynamics Corp. ( GD ), has received an extension to its previous contract worth $208.6 million from the U.S. Navy to buy long lead time material for three Virginia-class submarines. The submarines for which lead time material will be provided are SSN-793, SSN-794 and SSN-795. Long lead-time material includes steam and electrical-plant components, main propulsion unit and ship-service turbine generator sets, and miscellaneous hull, mechanical and electrical-systems components to support construction of these submarines. The Virginia-class submarine program is a class of nuclear-powered fast attack submarines serving the United States Navy. These submarines are designed for a broad spectrum of open-ocean and littoral missions. Moreover, they are less costly than the Seawolf class of attack submarines.