SFS — The 55 Knot Sealift Ship

Abstract

SFS is the acronym for the Surface Effect Fast Sealift Ship, a 20,000‐ton, surface effect ship (SES). The SFS acronym was chosen to distinguish it from the smaller, 100‐6,000 ton, SES craft. The paper is based on an Ingails Shipbuilding conceptual design and concludes that an SFS is buildable now using existing technology. The waterjet propulsion system and the seal development program are also discussed. Immediate application to the Army's sealift requirements, the possible alternative military sealift and commercial applications, and the application of SFS technology to future military and commercial ship design are examined. The SFS is designed to carry U.S. Army unit equipment such as tanks, trucks, and helicopters in a roll on/roll off configuration. The vessel must carry a 5,000 short ton payload over a range of 3,500 miles in sea state 3 at 100% full power at an average speed of 55 knots. The maximum cushionborne draft is ten feet and the SFS must be capable of loading and unloading while on cushion to permit operating in shallow draft ports. The original conceptual design was 825 feet long, 150 feet wide, and 84 feet high. It had 240,000 bhp of propulsion power and 60,000 bhp of lift power. The present configuration is slightly larger and has over 200,000 square feet of usable payload deck space. The parametric studies leading to the selection of the hull form and proportions are discussed. The logic used in the selection of the waterjet/gas turbine propulsion system is reviewed. The philosophy of the arrangements, the propulsion system, the lift air system, the fuel system, the ballast system, and the ventilation system are also addressed. The paper identifies the differences between the SFS operational profile and that of conventional ships. The payloadrange‐speed‐fuel relationships are explored and similarities with aircraft explained. The Army's need for a fast sealift ship is discussed. Features have been added by Mod II, which extend the design beyond the single Army mission concept and make it a truly versatile fast sealift ship which can perform virtually any known sealift mission.