# [extropy-chat] Mars rovers RIP?

Jeff Davis jrd1415 at yahoo.com
Wed Jun 9 21:50:28 UTC 2004

Mars rovers prepare for a dramatic last act

http://www.csmonitor.com/2004/0609/p01s02-usgn.html

The above article begins, "Well past their expiration
dates, ..."

So okay, the designers needed to GUARANTEE that the
Rovers would "last" long enough to complete their 90
day missions.  To me this means making them robust
enough so that the probability of failure prior to 90
days is effectively zero.  Inevitably this makes the
probability of failure on day 91 very low as well.
And day 92, and 93, etc.  Well, we're past day 180
and they're still goin' strong.  Which suggests the
obvious question, "Just how long will they last?"

I suggest a "Rover expiration pool", where we all make
our predictions re the date of the rovers' demise.

Now I don't know by what logic others will make there
predictions, but here is a thought or two from moi.

Batteries and photovoltaics.  Batteries get old and
fade away.  As they go through the charge/discharge
cycle they come to hold less and less charge each
time.  At some point the amount of charge they will
hold will be insufficient to last overnight, at which
point the game will be over.  Contributing to this
will be the decline in the output of the solar panels
providing the daily recharge.

If I knew the particulars of the battery design, and
the pattern of daily power usage, I might be able to
calculate how long before the batteries fail.  I don't
know this.  But I do have a cordless drill at home
which is till going strong after at least five years
of heavy and abusive use.  So...

I will guess five years from this date for the
problem-free rover, and two years for the rover with
the heater-always-on problem.

That's June 9th, 2009, and June 9th, 2006,
respectively.

And to make it interesting I will place ten bucks US
on each guess.

Best, Jeff Davis

"My guess is that people don't yet realize how
"handy" an indefinite lifespan will be."
J Corbally

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