(Henry Spencer) wrote:

In article ,
McLean1382 wrote:

And the need for
extreme reliability will drive up development costs in any case.

Not if you send along tools and spare parts (and guys who know how to use
them) instead, and provide enough redundancy and backups to give time for
them to be used.

The problem here is that it takes a little time to make sure your
pre-calculated MTBF and MTTR are in the ballpark, and that your spares
store has the proper width and depth. There's the issue of your tool
locker and ensuring that cal requirements can be met. There's the
issue of ensuring that the sell-by dates on spares and tools will
cover the life of the mission. There's the issue of ensuring adequate
training and documentation to support preventative and corrective
maintenance. There's the *big* issue of ensuring that the equipment
is designed to be serviced and maintained. There the issue of setting
up maintenance schedules and procedures...

No show stoppers, but a lot of engineering man-hours, a lot of
seemingly trivial details, and a fair amount of money. The Navy has
been wrestling with these problems for decades now, and is just now
getting the general philosophy down, yet each new class of ship has to
climb up a pretty steep learning curve getting all the details right.

In highly-lethal Earth environments, like Antarctica, we
don't see anywhere near the same development costs.

Partially because Antarctica isn't nearly as lethal as Mars, by a long
shot. Partially because a great deal of Antarctic equipment is either
COTS or near enough to it as the same environment is found in parts of
Alaska as well as in the Scandinavian countries and Artic expeditions.

If you're going to the trouble of sending people as part of the mission, you
should exploit their capabilities to the fullest to make the engineering easier.

You don't make the engineering easier by incorporating repair options
and spares, you just move the engineering problems into different
areas. The military and companies like the telco frequently choose
locally repairable equipment over depot level maintenance not to
reduce costs, but to increase availability at some cost in reliability
(mostly due to errors in maintenance).

Yes, this implies a somewhat larger expedition -- multiple ships,
substantial crews. That is actually cheaper than a cut-to-the-bone
minimal expedition where everything *has* to work perfectly because
there's no safety margin and no repair option.

No, Larger expeditions like this transform development costs into
operational costs. They explicitly don't reduce the costs of launch.

D.
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