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Re: Repeater on the Moon



> Hello Bruce and others.
>
> Just a minor nit if I might.  The ALSEPS were quite long lived.  The 
> last lunar landing was Apollo 17 Dec 1972.  The ALSEPS were finally 
> turned off on 1 Oct 1977.  It was purely an economic measure (the cost 
> was about 2 million a year) to help pay for the shuttle.  ALSEPS from 
> Apollo 12,14,15,16,and 17 were all working pretty good.  There were 
> quirks of course  (off the top of my head there was an interesting 
> temperature related problem to one of the instruments on 16 or 17) but 
> no serious problems.  The power source was such that they would still 
> be working today had they not been turned off.
>
> The trick was the RTG...everything stayed warm because it stayed on.

remainder snipped ..

Hmm.  I had thought the RTG's weren't that long-lived, but then again 
.. more or less the same RTG powered the Voyager spacecraft, so I 
should have remembered that.  I had thought the ALSEP's hadn't survived 
that long either, but a 5 year lifetime is pretty good for a lunar 
surface experiment, and I have to agree that keeping warm is the key to 
staying alive for that long.

I forget how much power those RTG's could generate though .. could we 
get enough power to run a transponder more or less continuously?  
They're light enough, a lot lighter than batteries at any rate.  If 
they last long enough to keep a transponder going for more than 5 years 
it's probably worth looking into.  Which solves both the night 
operation and weight problems, or at least makes the launch economics a 
little more viable.  Certainly something to think about, if those RTG's 
are available for civilian use ..

Heard from a flight instructor:
"The only dumb question is the one you DID NOT ask, resulting in my 
going out and having to identify your bits and pieces in the midst of 
torn and twisted metal."

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