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Rescuing the Insight Heat Mole?

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#1 Pess

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Posted 07 December 2019 - 11:00 AM

I think, by now, we have all heard about the issues with the Mars Insight Heat probe and its uncanny ability to resist digging much deeper than its own length.

 

Recently after penetrating about 10" into the Mars soil, it somehow reversed itself and came back out almost to the point of plopping down outside the original hole.

 

We have not heard much update on plans to try reinserting the probe and encouraging further penetration in a bid to salvage some of the experiment. But looks like the only option is to use the 'scoop' to try and right the probe and then put pressure on its butt-end to encourage forward penetration.

 

It's not an encouraging circumstance for sure trying to remotely get the scoop & pressure directly on the probe.  

 

Looking at the experiment, I am sure greater minds thought of this but why didn't the design include some reverse oriented wedges or spring loaded 'catches' to prevent backward movement once the probe went through a hammer cycle?  The side edges (not much would be needed) would hook into the sides of the soil and give resistance to backward movement of the probe when it went through a hammer cycle.

 

Too late now but I wonder why such a design feature was rejected?

 

Not much new info since the probe backed itself mostly out of its hole.   Experiment might be a lost cause at this point as the scoop could only offer push-back resistance until the probe got below soil level and then we likely would return to the same issue with the probe hammering in place without advancement.

 

 

Pesse (Probe hammering uselessly against the metal top of a buried Martian Biodome?) Mist

 

 

 

 

 

 

 

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Edited by Pess, 07 December 2019 - 11:03 AM.


#2 llanitedave

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Posted 07 December 2019 - 12:38 PM

I think the main issue is simply a lack of power and weight.  If you look at hammer drills on Earth designed for penetrating soil, they have some serious impact force behind them.

 

I don't know the details of this particular drill, and I'm sure they had some major design experts helping them out, so I'm really in no position to be a Monday Morning Quarterback, but I've drilled through a lot of gravelly alluvium in my day, a lot of sand, and a lot of bedrock.  Each substrate has it's own "best practices", although I've also drilled through hard volcanic cobbles using a system designed more for pea gravel.  It worked, but it wasn't pretty.

 

The main problem here is, I think, just not knowing what the substrate consists of.  But it you're not sure, you need something with enough power to get through the different possibilities.


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#3 Jim_V

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Posted 08 December 2019 - 04:10 PM

 

 

Looking at the experiment, I am sure greater minds thought of this but why didn't the design include some reverse oriented wedges or spring loaded 'catches' to prevent backward movement once the probe went through a hammer cycle?  The side edges (not much would be needed) would hook into the sides of the soil and give resistance to backward movement of the probe when it went through a hammer cycle.

 

 

 

Pesse (Probe hammering uselessly against the metal top of a buried Martian Biodome?) Mist

Seems the idea was that  the existing soil would offer up the required  friction, keeping the probe "digging". Except the soil is not acting as expected. There seems to be no loose granular fall back into the hole which would offer up the required friction. 

 

I tend to agree with Pess, that a built in mechanical friction should have been used, but that design would then add in other possible complications and possible failure. . 



#4 Pess

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Posted 09 December 2019 - 02:56 PM

Seems the idea was that  the existing soil would offer up the required  friction, keeping the probe "digging". Except the soil is not acting as expected. There seems to be no loose granular fall back into the hole which would offer up the required friction. 

 

I tend to agree with Pess, that a built in mechanical friction should have been used, but that design would then add in other possible complications and possible failure. . 

My thinking was adding something like fish scales to the sides of the mole. 

 

Even some scale design machined into the sides may have been beneficial.

 

It is almost like some moisture is cementing the granules of dirt allowing them to be compacted creating a hole which doesn't offer side-friction.

 

Looks like the experiment is dead. Even getting the  probe back in and using the scoop to press it downward, the probe likely will not continue onward past the top of the hole unless the ground material significantly changes beneath the surface.  

 

Pesse (This space for rent) Mist



#5 Jim_V

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Posted 12 December 2019 - 01:58 PM

My thinking was adding something like fish scales to the sides of the mole. 

 

Even some scale design machined into the sides may have been beneficial.

 

It is almost like some moisture is cementing the granules of dirt allowing them to be compacted creating a hole which doesn't offer side-friction.

 

Looks like the experiment is dead. Even getting the  probe back in and using the scoop to press it downward, the probe likely will not continue onward past the top of the hole unless the ground material significantly changes beneath the surface.  

 

Pesse (This space for rent) Mist

I hate to consider second guessing the designers, but it is possible the soil is "frozen" a couple inches under the surface, and I would have thought that would have been considered as a design parameter. ( note frozen does not mean frost frozen)

 

Irrelevant, of our armchair quarterbacking, I to think the experiment is done. A shame, but....


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