Re: Registration

[John Brownlee <jonnie@chronic.lpl.arizona.edu>]

	Two words, boys: 'power failure.' 
	One of the most common single points of failure is the electrical
system in submersibles of all kinds, statistically. Properly implimented
viewports have a significantly lower failure rate, I actually don't know
of any true failures in the past.  Electricals are complicated with
hundreds of components, viewports have a half dozen. There is a reason
submersibles designed today still have viewports; if you lose a battery
compartment or a cable gets sheared you can still see. 
	It's the same reason why even the most automated subs have a means
to blow air into the tanks under the power of the compressed air in the
cyllinders alone. Remove single points of failure; many subs require some
operator intervention during recovery from an abort, and being able to see
outside helps.
	At least that's the way I see it. No pun intended, of course. :)

							John

John Brownlee
Lunar and Planetary Lab
University of Arizona
jonnie @ lpl . arizona . edu