The Challenge of Vertical Replenishment at Sea
We have recently posted interviews with the Captain of the USNS Robert E. Peary and discussed the evolving role of supply ships in the global operations of the USN-USMC team.
We underscored the complex ballet of doing re-supply at sea in the sea states in which these ships operate. Military Sealift Command recently has provided us with a video, which shows one such operation. In this operation, a sister T-AKE ship, USNS Amelia Earhart, is seen working with the USS George Washington (CVN 73). This is called UNREP or Underway Replenishment.
Here the cargo is being organized for transfer on the Amelia Earhart and is transported by either a Puma helicopter or by transfer lines.
The two major methods of transferring dry cargo used today are via vertical replenishment (VERTREP) and connected replenishment (CONREP). These two methods may be used singly or at the same time.
VERTREP is carried out by helicopters with the ships in close proximity, or miles apart, depending on the tactical situation and the amount of cargo to be transferred. The helicopters transfer cargo using a sling similar to a net that is suspended from a hook on the underside of the copter. One or more helicopters continuously shuttle back and forth between the delivery ship and the receiving ship. There may be more than one ship receiving cargo at one time.
CONREP involves two processes, refueling and re-supply. In fueling at sea (FAS), fuel is pumped from the delivering ship, such as a fast combat support ship (AOE). Other replenishment ships such as the combat stores ship (AFS) and the ammunition ship (AE) can deliver fuel, but their primary mission is the delivery of dry cargo by methods referred to replenishment at sea (RAS).
CONREP uses a wire highline between the delivering and receiving ships that uses a Standard Tensioned Replenishment Alongside Method (STREAM) rig. The two ships steam side-by-side and the hoses and lines used to transfer fuel, ammunition, supplies, and personnel connect the ships. The STREAM rig is preferred over other connected replenishment methods since it permits greater ships separation. The delivery ship may have a receiving ship on both sides at the same time.