Advanced Hydro-Ski Vehicles for Amphibious Warfare

Abstract

The Lockheed hydro-ski vehicle is one of several new concepts being examined to meet a .Navy requirement for advanced, high-speed, assault landing craft. The hydro-ski is a variable geometry planing hull capable of speeds ranging from 35 to 60 knots and maintenance of this speed in a seaway. The hull design is a normal, essentially flal, planing bottom; however, a pair of skis have been added which, when retracted, fit into recesses in the hull. Beyond hump speed the skis are hydraulically extended to provide two narrow planing surfaces, thus lifting the basic hull well above the water surface, in this fashion the flat-plate area that is exposed to wave impact is greatly reduced. A 25-ft test craft has been built to prove the concept. The preliminary design of a family of assault craft has been completed, all powered by water jet propulsion systems. With gross weights varying from 4500 to 200,000 Ib, these craft have been configured as suitable replacements for current landing craft. A very simple design, the hydro-ski boat may be configured for any mission for which high speed in a seaway is a fundamental requirement. 111 ING World War 11, and again in Korea, our military forces were required to make assault landings on enemyheld shores in order to gain and hold a beachhead. Landings were accomplished in barge-like vehicles with a maximum speed capability of 9 knots. The ride to the beach was usually rough, slow, and often hazardous, particularly when conducted under enemy fire from the shore. The U. S. Navy is currently embarked upon a program to improve all facets of their ability to conduct amphibious warfare. Several different vehicle concepts are being evaluated for the most practical design approach to various sizes of high-speed landing craft which will improve this situation in the future. The Lockheed hydro-ski is one of the concepts being considered. The hydro-ski described in this paper is basically a variable geometry planing hull. Very high speeds have been obtained over the years by utilizing the planing hull; unfortunately, however, these speeds are attainable in smooth water only! All such craft must restrict their speed when waves are encountered because of the severity of slamming loads caused by wave impact on the flat-plate surface of the hull. The hydroski provides a means of reducing the flat-plate area exposed to wave impingement, thus permitting the craft to remain at high speed in a seaway, within the limits of the design. One naval officer, drawing upon his experience as a sailing man, has described this concept as reefing the beam7' when encountering rough (weather) water. Figure 1 is presented to describe the variable geometry hull. Shown is a 25-ft test craft, built by the Marine Vehicles Department of the Lockheed-California Company to prove the basic concept of impact load alleviation. The hull is a normal.