High Performance Ships—Promises and Problems 3 
This paper will discuss the potential of these concepts and some of the problems that 
arose in expanding certain of them into practical ship designs. 
SOME HIGH-PERFORMANCE SHIPS 
Ground-Effect Craft 
Ground-effect craft offer the contradictory capabilities of high speed and the ability to 
hover above the surface. Speeds of well over 100 knots appear to be attainable and such 
speeds are attractive for many applications. The ability to hover has obvious advantages, 
for example, in amphibious operations. Recent theoretical and experimental evidence indi- 
cates that in the high speed range of operation, these craft will not respond to wave action, 
but can maintain level flight over ocean waves. These promises, when and if attained, indi- 
cate applications for amphibious warfare, antisubmarine warfare, aircraft carriers, missile 
carriers, cargo and personnel carriers, etc. The rapidly expanding literature on these ground- 
effect craft is a measure of their apparent promise; it is also a measure of the many problems 
to be resolved. 
Ground-effect craft do not completely avoid the free surface, particularly the more 
“pedestrian” versions of this concept. Fig. 2 shows four types. Various combinations of 
these basic schemes are possible, and it would seem that every conceivable variation has 
been proposed. 
iL oe 
ees 
AIR CUSHION 
RAM WING PERIPHERAL JET 
SPEED > 100 KNOTS SPEED < IOOKNOTS 
ZT WS 
AIR CUSHION 
SIDEWALL PLENUM CHAMBER 
SPEED < 50KNOTS SPEED < 100 KNOTS 
Fig. 2. Four forms of ground-effect craft 
The “ram wing” shown in the top of Fig. 2, is actually a low-flying aircraft. The sig- 
nificant reduction in induced drag achieved by flying close to surface should permit the 
attainment of very high lift/drag ratios at high speeds. Values as high as 60 at a chord/ 
height ratio of 0.5 have been estimated. 
