21 Jun
2004
21 Jun
'04
6:37 a.m.
>>>> "der" == der Mouse
<mouse(a)rodents.montreal.qc.ca> writes:
> There was an idea some time back that if we ever
get to the moon
> that we could be using "open-air" valves (tubes) in the vacuum
> there for high powered devices
der> Is the "open-air" vacuum on the Moon a hard enough vacuum for
der> vacuum-tube technology? Does it depend on whether it's day or
der> night (and therefore whether there is solar wind pouring in)? I
der> know that _some_ vacuum-tube technology - notably CRTs - depends
der> on electrons having a mean free path well over the tube size,
der> and that needs a pretty hard vacuum.
That's true for all vacuum tubes. If that condition isn't met, you
have a "gas filled tube" -- something you occasionally want, but not
very often.
I think even solar wind is a pretty hard vacuum.
> - with the benefit that goes with the better
radiation resistance
> that goes with valve technology.
der> Is it valves that give you rad-hardening, or size? A transistor
der> the size of a valve would, I suspect, be inherently pretty
der> rad-hardened. (Certainly the largest transistors I've seen are
der> far smaller than the smallest valve I've seen. Probably by
der> about an order of magnitude, once you strip each one down to the
der> operating portion.)
Take a look at power transistors sometime. Some come in "hockey puck"
packages, which describes not just the shape but also the size. And I
think a fair fraction of that package is die...
paul