Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: New type of computer- no semiconductors
Message-ID: <1990Jan9.165937.9503@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1309@milton.acs.washington.edu>
Date: Tue, 9 Jan 90 16:59:37 GMT

In article <1309@milton.acs.washington.edu> whit@milton.acs.washington.edu (John Whitmore) writes:
>superconductors should function well in space, and they'd be easier
>by far to cool (with a well built parasol, any old rock in space
>will achieve 3.2 Kelvin temperatures, well under the superconducting
>threshold temperature)...

Unfortunately, not so.  That parasol is not magic; if it keeps the sunlight
off, it will in turn get warm and start to radiate heat into your computer.
A well-built parasol in near-Earth space will give you liquid-nitrogen
temperatures, 70K or thereabouts, but you'll have to be a lot further out
from the Sun to get liquid-helium temperatures.  Satellites that need
liquid-helium temperatures for sensors, like the current Cosmic Background
Explorer, carry large tanks of liquid helium and plenty of insulation...
and when the tanks boil dry, that's the end of the sensors' useful life.
-- 
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu