[Coco] Re: Off Topic - Mars Rover Software

[Theodore Evans (Alex)]

On Jan 20, 2004, at 9:17 PM, Brad Grier wrote:

> One of the Viking landers operated on the surface of Mars from 
> 1976-1983 (NASA mistakenly sent a bad command that turned the thing 
> off). That's a long time - but I think it was powered by some kind of 
> plutonium power generator (there were no solar panels). It's very 
> difficult to get such generators off the ground these days.

These space based nuclear reactors are called RTGs (radio-thermal 
generators).  The decay of the nuclear material causes them to get hot 
and they use thermocouples to generate electricity from this 
temperature difference.  They are light, provide a reasonable amount of 
power for a fairly long time, and work anywhere, but the instruments of 
the space craft have to be protected from the reactor, and unlike 
conventional batteries, they decay at the same rate whether you use the 
power or not.