The future USS Zumwalt, the nearly $4 billion stealth destroyer being built by Bath Iron Works, was launched into the Kennebec River on Monday. The BIW drydock (blue) would submerge later in the day, and the Zumwalt (gray) would float into the river. The 610-foot Zumwalt’s primary function is land attack — to provide missile and gun support for troops ashore, according to Todd Estes, manager of the DDG 1000 program office at BIW. The “tumblehome” hull of the DDG 1000 also is distinct, designed to “pierce” waves, according to the Navy. The superstructure shape and arrangement of the antennas are designed to make the ship far less visible to enemy radar. The destroyer also features a new, multifunction radar system. BIW will continue work on the ship until its scheduled delivery to the U.S. Navy in 2015.