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Old March 10th 19, 11:08 PM posted to sci.astro.amateur
Chris L Peterson
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Default NASA never expected to have to re-position its drilling probe?

On Fri, 8 Mar 2019 23:52:58 -0800 (PST), Quadibloc
wrote:

On Thursday, March 7, 2019 at 7:22:04 AM UTC-7, Chris L Peterson wrote:

First of all, NASA didn't design this probe. Second, it was entirely
expected that the probe could hit something that would slow it down or
that it couldn't get through. Making the probe retractable and
repositionable was not a practical option.


If you knew anything about engineering, you'd know about design
tradeoffs and cost/benefit analyses.


A naive person such as myself - and such as any number of Congressmen - would
have thought that given that it costs billions of dollars to send a probe to
Mars, and if drilling beneath the Martian surface was an important part of that
probe's science mission, then any extra cost to make "the probe retractable and
repositionable" would have been not merely well worth it, but imperative.


It is precisely the sort of thing that could make the entire mission
impossible, by adding significant cost and complexity to the design,
making it unfeasible to include other instruments, or making
everything less reliable. A change like that would impact almost every
system on the lander.

(InSight is part of the Discovery program, which funds relatively
inexpensive missions. The InSight budget is $830 million. A heavier,
more power hungry, retractable probe- which would need to operate on a
completely different principle than the simple impact probe now in
use- could easily have killed the entire program. It might never have
been funded at all given a higher budget or greater opportunity for
mechanical failure.)