FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1963
1963 - 2272.PDF
YLlGHT International supplement, 22 August 1963 Air-Cushion Vehicles Surface-Effect Ship U.S. MARITIME ADMINISTRATION SURFACE EFFECT SHIP SP* Provisional three-view of the 200,0001b MA RAD ship IN OUR JUNE ISSUE we published a plot of vehicle speed against time (in years) to show the contrasting philoso phies in the ACV field between Britain and the United States as seen by the US Maritime Administration. Whereas the former country has "embarked early on a programme of hardware develop ment, producing a craft of lower per formance at an earlier date," the MARAD philosophy is "one of con centrating early effort in a research phase to produce a better-performing craft at a later date." The quotations are taken from a Paper read before a joint SAE/ASNE meeting in Washington by Dr Scott Rethorst, of the Vehicle Research Corp, Pasadena, Calif, and Mr W. T. Potter, of the US Department of Com merce, describing the Surface-Effect Ship—a special form of air-cushion vehicle evolved from a lifting aerofoil *ith its tips turned down so that, when operating in ground effect, it becomes effectively two-dimensional and lifts without paying any penalty in induced drag. Vehicle Research Corp is developing a vehicle which at low speeds rides on a conventional air bubble, generated by peripheral curtain jets, but which has an overall shape having the form of a lifting aerofoil with its tips turned down close to the ground. As vehicle speed rises, so does its own body-generated lift— partly resulting from reduced pressure on top and partly from a "channel" of increased pressure underneath, between the down-turned sides (Fig 1). The spacing of the streamlines shows the constant high pressure underneath, resulting from external compression ahead of the vehicle, and the uniform reduction in pressure around the top and down the sides "eliminating any shed vorticity or induced drag." This idea appeared promising enough in 1960 for the US Navy (Office of Naval Research) to issue a solicitation for bids in January 1961. The winner was VRC, who had previously conducted extensive research into air-cushion vehi cles—GEMs, ground-effect machines, in American parlance—chiefly for over land use. In the spring of that year the Maritime Administration became ac tively interested in the idea, and a con tract with VRC was permitted in August 1961, for a commercial version. VRC set forth the controlling design parameters, while MARAD settled upon a 100-ton (200,0001b) craft. Pre liminary design and development test ing proved so successful that steps were taken last August to provide money for further work. Included in this further work is the construction of dynamically scaled man-carrying models. The first of these is a 24ft two-seater and, although details have not yet been published, much can be deduced from the sketch (Fig 2). The crew sit to starboard of the centreline, and the central portion of the upper sur face is substantially raised, to increase the effective thickness/chord ratio in this area. There are two centrifugal lift fans and two propellers, and what ap pears to be an AiResearch gas turbine is near the front fan. There appear to be two jets along the sides formed by gaps left between three (apparently flexible) hollow ducts. The two propellers are presumably driven by shafting from the main powerplant. Stability and control is provided by a central fin and two rear fins and rudders, joined by a horizontal tail. Construction of this research vehicle 25
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
