Replenishment at sea (RAS) or underway replenishment (UNREP) is a method of transferring fuel, munitions, and stores from one ship to another while under way. Most ships can receive replenishment on either side. Aircraft carriers of the U.S. Navy, however, always receive replenishment on the starboard side of the carrier. The design of an aircraft carrier, with its island/navigation bridge to starboard, does not permit replenishment to the carrier’s port side. (learn more: en.wikipedia.org/wiki/Underway_replenishment)
In this video, watch as aircraft carrier USS Gerald R. Ford (CVN 78) conducts a replenishment-at-sea evolution with USNS Leroy Grumman (T-AO 195). USS Ford is currently underway conducting test and evaluation operations.