On Mon, 10 Dec 2018 13:19:41 -0000, Tim Streater wrote:

In article , Bruce Farquhar
wrote:

On Mon, 10 Dec 2018 09:22:20 -0000, Tim Streater
wrote:

In article , Bruce Farquhar
wrote:

On Sun, 09 Dec 2018 21:40:03 -0000, Rod Speed
wrote:

Bruce Farquhar wrote

A thermocouple produces enough to power a spacecraft?!?

It isnt a single thermocouple, it's a thermopile.
https://en.wikipedia.org/wiki/Thermopile
https://en.wikipedia.org/wiki/Nuclear_power_in_space

Or just for some small electronics?

Not small at all.

Why are these not used on earth?

Probably not that cheap, once you've made the Pu-238.

Whatever happened to those AA nuclear batteries? I assume
they worked the same.

What on earth are you talking about?

Some idea or prototype someone came up with 10 or 20 years ago. They were supposed to be to for use in very long life and low current things - battery backup for alarms, wall clocks, thermostats, etc.