How high do you need to get if your 6L6 is broken?

Been reading Golden Age SF again? The "open-air electron gun" trick was used in George O. Smith's _Venus Equilateral_.

This guy claims to have gotten a 12AV7-equivalent to run at 133 Pascal, equivalent to ~85,000 feet altitude (16 miles) but he had to crank up the voltages:

To get commercial-grade vacuum you need to get into Low Earth Orbit.

Mark L. Fergerson

If there's a hole in the envelope, won't the electrons fall out?

You also need to think at power dissipation issues, since there s no convection cooling,

Of course running the anode red hot especially on the night side of the orbit, facing the cool sky will help lot in terms of radiative cooling.

The Digikey website for a high voltage depletion mode FET ?

I think that if you modify a (hand) bicycle pump properly, you can get a useful vacuum for that purpose. Or maybe use one of those aquarium aerator pumps; the kind that uses a rotating cam to displace the tube that goes thru it.

That is what the grid leak detector is for; put the pan underneath.

In the vacuum environment of space,ignoring the possible effect of direct s un light, the envelope can also only radiate heat but like the plate has a rest temp of zero absolute, instead of room temp of 295K.

The true situation at thermal equilibrium is non obvious.

... Phil

on. However, most of it is in the far infrared and so gets absorbed by the soda glass envelope. Once its temp rises, the envelope radiates back and he lps keep the plate hot. The glass is cooled by convection and some radiatio n too - at max rated power dissipation, the surface temp settles to about 2

sun light, the envelope can also only radiate heat but like the plate has a rest temp of zero absolute, instead of room temp of 295K.

You won't need an envelope

NT

You'd have to reactivate the cathode when you got up there.

Cheers

Phil Hobbs

Plus, the whole plate structure is at risk of collapse with no envelope to support and protect it.

.... Phil

Without gravity, the drip pan won't work.

Only about three feet, the height of the drawer where your credit card is 8-)

Or course, the real hardcore selfmade-man would never do this and instead fix the tube or build a new one from bare metal and glass:

At least 0.001 torr at an altitude of 59 miles or higher:

One problem might be that if you're flying at 59 miles altitude, there's not enough air to conduct sound, so nobody will hear your guitar playing.

Incidentally, vacuum tubes in otter space are making a comeback:

Not much convection or conduction cooling either.

after you

NT

I guess you'd have to be pretty high to start wondering how high you need to be ;)

-Lasse

VE was great fun, if you could ignore the extreme cheesiness of the romantic subplots.

And of course charging up Murdoch's pirate ship with an electron gun wouldn't have affected anything inside, because the skin is a big Faraday cage.

Cheers

Phil Hobbs

if you can sit on the edge of a black hole without getting suced in yourself, you maybe able to generate enough vacuum void to allow it to conduct properly.. But then again, the hole will also be sucking up other gases while it passes by..

So in short, you may get the performance of a gassy tube!

Get your space gear on!

Jamie

tt:

I thought about going there...

As it happens, I was high when I wrote my reply, and am right now. I use pot* to supplement the naproxen I take for my osteoarthritis because what t he docs want to do to me is more invasive (like steroid injections into my joints) and has side effects I prefer not to experience (from skin irritati on to death!).

I hope that doesn't get me kicked out of The Deplorables...

• One reason I moved to WA State- it's legal here

Mark L. Fergerson