(Figure 67) which might be of a size and type suitable for multiple mounting 
on a large rotating disc for large-diameter hole boring. This model does not 
have direct impacting of the oscillator with the work tool anvil as does an 
earlier drill model; it is simplified in sealing, construction, and use because 
of the self-contained aspects of its construction. Its efficacy remains to be 
proved in deep-ocean applications, but it almost certainly will prove advan- 
tageous in loosening soft rock, hard soil, etc., and reducing cutter forces. A 
prime feature of this type of oscillator is the very high energy input—50 hp 
in the model shown; the small size of the chips produced will facilitate flushing 
from the work face. 
Summary 
Of the nonconventional methods of destroying hard rock, the use of 
very-high-velocity water jets for spalling, and of electron beam cutting and 
spalling appear the most attractive for early development for deep ocean 
bottom work. The electron beam in its present state of development Is not 
adapted to a high-pressure water environment, except in vertical drilling, but 
the water jet does appear to be wholly suitable. Development of supporting 
and movable machines capable of using these techniques advantageously is 
needed. 
If neither of the above methods proves workable, rapid oscillating 
of a number of carbide bits mounted on a rotating work face probably will 
offer some advantage over the present cutter system. 
Large hole rock penetration appears to be within the state-of-the-art 
so far as rock excavation is concerned, but many of the methods applicable 
in a one-atmosphere environment will probably not be feasible in the high- 
pressure environment. Systems which generate large amounts of dust or 
noxious fumes probably cannot be used because air will not be readily 
available to purge the excavation. Necessity for changing bits will make 
the use of conventional cutters on large moles undesirable. 
Future Plans 
New rapid excavation techniques in rock should be further 
investigated, with some support given to those that appear most useful in 
the high-pressure water environment or in the one-atmosphere environment 
of a sealed-off cavity under the ocean. Building and test of scale-model devices 
for demonstrating the more favorable techniques will be in order for the next 
two fiscal years. The high-velocity water jet, the electron-beam, and high- 
impact abrasive cutting in particular appear to have advanced to the point 
where further investment is justified. 
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