General Dynamics Corp. said Friday that its Electric Boat subsidiary recently received three U.S. Navy contracts worth a combined $4.6 billion to design and develop a new kind of submarine and to continue construction of Virginia-class attack submarines.

A five-year, $1.85 billion contract calls for Electric Boat to perform research and development work for a new class of ballistic-missile submarine, which is scheduled for a 2021 construction start.

In addition, the subsidiary will continue to develop the joint U.S. Navy and Royal Navy common missile compartment for Ohio Replacement submarines and the U.K. successor-class ballistic-missile submarine, the company said.

Electric Boat also received a $2.5 billion contract to build two Virginia-class submarines. Under the third contract, Electric Boat will receive $308 million to buy materials for three Virginia-class submarines, General Dynamics said.

Shares of General Dynamics slipped 15 cents to $71.33 in midday trading Friday. They are trading near the high end of their 52-week range of $61.09 and $74.54.