In article ,
Mike Andrews wrote:
Mike Knudsen wrote:

I doubt there were ever walk-in tubes. The vacuum required for any kindof tube
life is so "hard" and pure that you wouldn't be able to pump out a whole room
to that purity. Though maybe with a really big "getter" ... Mike K.

I have this image of someone walking in through the airlock with a
_big_ container of cesium or strontium, to be used as a getter, and
hooking it up to a pair of terminals on the inside of the tube once
it has been baked and pumped down for a while.

I also have this image of an enormous induction heater, with coils
completely surrounding the tube, forepumps the size of modern fanjet
engines, and diffusion pumps slinging kiloliters of oil per second.

Somehow, I think it's just not viable.

I believe that in Rocket Ship Galileo, Heinlein discussed vacuum tubes
on the moon. No external envelope needed, just shielding.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."