GEM Research in the U.S. 295 
S 
Size/Height — 
ize/Heig 7 
1000 
8 
25 
500 _s Es 
Fa 
= 
oo o 
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a 
> : 
F Typical 
~ Airplane 
= 
= Typical 
s Helicopter 
lw 
S 
Size/Height — 
ize/Heig AC 
Fig. 11. The relationship between performance 
and size for a GEM 
provide better performance than the air cushion. There is the possibility that a GEM can 
compete successfully, even with somewhat inferior lift/drag ratio, because of its more 
flexible load-handling abilities and terminal facility requirements. And there is the possi- 
bility that the GEM’s apparent compatibility with nuclear power will, in future years, loom 
larger than the lift/drag consideration. Nevertheless, it would be necessary to stretch any 
or all of these possibilities rather far to avoid the conclusion that ocean-going GEM’s will 
be very large vehicles indeed. As such, their development represents a very imposing 
economic undertaking, and, while a great deal of current GEM research and study is directed 
toward the ocean-going machine, it may be assumed that serious development efforts will 
await clarification of the present confused state of knowledge. 
In the meantime, GEM applications will be made in “fringe” areas where special cir- 
cumstances or special requirements make moderate-size GEM’s attractive. The two main 
categories of such fringe areas are: 
1. The limited application possibilities over flat inland areas and protected waters, 
where extremely low operating heights afford good performance for moderate-size vehicles. 
These include passenger and cargo ferries, emergency craft, sport craft, and swamp buggies. 
2. Limited military application possibilities where requirements for speed, amphibious 
capability, and load-carrying ability outweigh the conventional economic performance 
criteria. 
Early applications are likely to center around the air curtain concepts. Only in this 
area is the state of the art sufficiently advanced to permit rational design. Where the future 
will lead is anybody’s guess. 
Whatever form the GEM of the future takes, this much is certain: If energetic and 
enthusiastic activity count for much, the GEM’s future in the U.S. should be very bright 
indeed. 
