Re: Making viewports (was: Visibility / Safety or Safety / Visibility ?)

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

	Hi Phil,

	I am curious, as someone "in the game," do you think that acrylic
hemi's will eventually supplant conical viewports even at deep depths
(i.e. on the order of 1000's of meters)? Your designs make good use of
them to about 2000', but what do you see the future being given the
progress in large castings of polymers like acrylic? Curious about exactly
what the state of the art is in casting hemi viewports with such high
thicknesses. 
	Of course there is limited support (i.e. the NSF grant fiasco) for
any manned effort off the continental shelf, but I am wondering what is in
store for the next generation of manned deep submergence work. It
would be interesting to see where the state of the art is, even if it
isn't being implimented.

							John

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