The design principles of high speed marine craft are much less established than the well-established techniques honed over centuries of practice in the design of low speed marine craft with their displacement hull origins. High speed marine craft design, on the other hand, involves study of different hull form concepts, each requiring an understanding of four basic forces resulting in the lift and the drag of the craft. These four forces are: hydrostatic (buoyancy); hydrodynamic; aerostatic and aerodynamic. Each of these four forces scale by different laws of physics making scaling difficult from small models to large ship sizes. The combination of those forces applies differently in each case depending on the choice of concept being considered. In a broad sense, for the hydrofoil, the hydrodynamic forces dominate; for the amphibious air cushion craft, the aerostatic forces dominate; for the wing-in-ground-effect craft (WIG), the aerodynamic forces dominate. Coupled with these different forces, the high speed marine craft must also contend with the physics of subcavitating and supercavitating flows in both the hull hydrodynamics and in the propulsion schemes envisaged.

This influence of the four forces has a significant impact on the size and speed of the craft and its use or mission. This intrinsic triad of “size-speed-mission” is a key consideration when asking what is achievable in attaining high speed at sea. This relationship is expanded upon throughout the book. Because of these complex interactions between the various forces and choice of craft concept, the programmatic history of developing high speed marine craft has been somewhat sporadic with isolated successes among various setbacks caused by both technology issues and programmatic stumbles.

Upper limits of low speed marine craft speeds using displacement hulls have remained relatively unchanged over several centuries with typical values of 25–35 knots, depending on ship size and sea conditions. The “speed limits” for high speed marine craft vary widely depending on the concept selected but speeds from 50 to 250 knots covers the experience base under discussion.

Two major thrusts in the US for high speed marine craft were by the US Maritime Administration (MARAD) for commercial shipping, and by the US Navy for military ships and craft. MARAD conducted two major thrusts; first a surface piercing hydrofoil with planned speeds of 60–100 knots and subsequently, a combination hovercraft and WIG design for 100–150 knots.