Crew/Combat System Performance Requirements in the Operational Environment of Surface Effect Ships

Abstract

ABSTRACTThe Surface Effect Ship (SES), using a relatively unexploited natural phenomenon, portends a potential revolution in marine transportation and naval application. The prospect of ship designs capable of nominal 100‐knot speeds and transoceanic ranges offers exciting mission possibilities; coupled to such opportunities are certain non‐optimal vehicle features generally associated with a still maturing concept. Exercising SES high‐speed capability in high sea states can result in vertical vibration modes not previously sustained by man for long time periods. The challenge is twofold: 1) to the design engineer, the opportunity of evolving improved ride quality techniques during the forthcoming history of SES development; 2) to the standards institutions, to provide guidance without strangling an emerging technology.The SES is a fast ocean‐going ship employing a self‐generated cushion of air for lift support, reduction of resistance, and reduction of rough water loads and motions; the high‐speed capacity of SES especially in aggravated sea conditions can, as a function of mission demands, result in a unique heave acceleration environment. Both crew performance information and long‐term medical implications are of interest since naval application requires extended mission times and men are expected to live aboard SES as any other sea‐going ship. Vertical motion is expected to center in the region from 0.2–3.0 Hz with predominant energy in the 0,5–2.0 Hz interval for a 2000‐ton ship. Neither the scientific community which produces standards nor the professional operators who command ships have yet established either exhaustive characterizing data regarding performance or significant operational experience in such an arena of vibration frequency. Indeed, the standards and the experience are inextricably bound together and must evolve iteratively since the subject presently suffers from a paucity of data.This paper attempts to set forth the problem, from the customer's point of view, in operational terms. It stipulates basic requirements as they are currently envisioned, reviews the status of standards information available to the designer in the 0.2–3.0 Hz regime, and provides new impetus and additional justification for appropriate data collection in such a vibration environment.Preliminary insight into problem specifics has been obtained from use of a manned six‐degree‐of‐freedom motion base simulator at NASA's Marshall Space Flight Center, using empirical data from 100‐ton test‐craft and motion predictions from a 2000‐ton SES math model. A simulated pilot house was stimulated to portray ship response characteristics at various speeds in diverse sea states. Results of these motion simulations and selected critical crew tasks conducted during the tests for up to four‐hour intervals are discussed. The need for extensive additional effort over a broad front to establish a sound data base regarding long‐term exposure effects, if any, is made clear.The question of operational application and concomitant impact upon mission equipment suitability is exposed to view and discussed briefly, and finally, a brief status report on SES development, schedule and projections for the future conclude the paper.