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from the diggy-diggy-hole,-diggy-diggy-hole dept.
NASA engineers are preparing another tactic to get the troubled "mole" instrument on the Mars InSight lander burrowing into the regolith as intended.
Engineers plan to use the robotic arm on its InSight Mars lander to push a heat flow probe into the surface, acknowledging that they have "few alternatives" if that effort fails.
The Heat Flow and Physical Properties Package instrument team has spent nearly a year trying to get the instrument's probe, or "mole," to burrow into the surface. The mole has an internal hammering mechanism that is designed to drive the probe as deep as five meters into the surface in order to measure the heat flow from the planet's interior.
The mole, though, stopped only about 30 centimeters below the surface. The mission has tried a number of ways to get the mole moving again, including removing the instrument housing on the surface to allow the lander's robotic arm to try and fill in the hole created by the mole, as well as pin the mole to one side of that hole, increasing the friction needed for the mole to work its way into the surface.
In October, that use of the arm to pin the mole worked briefly, allowing the mole to burrow into the surface, only for it to rebound partially out of the hole. A second attempt led to the mole again rebounding partially out of the hole in January.
The mole is a 16-inch-long (40-centimeter) spike equipped with an internal hammering mechanism that relies on friction from the soil to help it dig down. The probe is designed to drag a ribbon-cable like tether behind it as it digs.
While pushing down on the top (back cap) of the probe seems an obvious approach, according to NASA "The team has avoided pushing on the back cap until now to avoid any potential damage to the tether."
Previous Coverage
More Mars Mole Mission Misfortune
Mars Mole Mission Rues Resistanceless Regolith
NASA to Jack up Insight Lander to Assess Non-Penetrating Probe
InSight Impinges Insufficiently in Site
Also at NASA-JPL
(Score: 2) by ElizabethGreene on Monday February 24 2020, @05:11AM (4 children)
The other concern with pushing on the back of the mole is the risk that it flops flat out of the hole. Once it's lying flat there isn't an obvious way to get it vertical again. Making provisions to allow the arm to retrieve and redeploy the science instruments seems really important now, but it wasn't a consideration when when the probe was built and tested here on Earth. That's a lesson learned.
On a related note, once the mole experiment is placed (successful or not), I hope we can use the arm to dig a trench. Photographs of what's under the surface soil would be interesting data.
(Score: 2) by bradley13 on Monday February 24 2020, @11:20AM (3 children)
Maybe I've missed it, but I haven't seen an analysis of why these problems are happening. Are they hitting rocks? Or - what seems more likely - have billions of years of blowing reduced the surface soil to such a fine powder that it is nearly frictionless? For the nearest Earth equivalent: how would the "mole" do, drilling in dirt coated with absolutely dry Sahara sand?
Everyone is somebody else's weirdo.
(Score: 0) by Anonymous Coward on Monday February 24 2020, @03:35PM (1 child)
I don't entirely see how frictionless soil would be a problem, but this is definitely not the case. That's based on a misconception about Mars driven by visuals and sci-fi tropes. Turns out the Martian soil is, on average, about about 2% water. Put another way, a cubic foot of Martian soil = ~1 liter of water.
As for the explanations... Imagine you're drilling into a wall. And your drill stops working properly. What's the problem? Power? Overheating? Jam? Mechanical dysfunction? Bit stuck? One of a million other reasons? Now imagine your drill is 40 million miles away, drilling into a surface you know nothing about, with a physical condition you can only measure using potentially faulty sensors, and every action you send your drill takes 6-40 minutes to get a response back. We so desperately need to get humans on Mars if we ever hope to make any sort of meaningful scientific progress.
(Score: 2) by takyon on Tuesday February 25 2020, @11:37AM
We just need a nice plasma drill. Or maybe even off-the-shelf equipment like jackhammers that can be manipulated by the rover or robots.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by ElizabethGreene on Monday February 24 2020, @11:51PM
There is some discussion about it in JPL's FAQ [nasa.gov].
They believe the problem is, as you've said, that there isn't enough friction for the probe to operate properly. Inside the probe is a linear actuator. The actuator lifts a weight and then slams it into a stop near the bottom of the probe. That should cause the probe to move down and that appears to work. They believe the problem is that the next action, lifting the weight so it can hammer again, causes the actuator to move back up again. This didn't happen in the test conditions because there was sufficient friction between the probe and surrounding soil to hold position during the upstroke.
I was thinking about it after I wrote my comment and I think I was wrong about the probe falling flat being a full failure mode. IIF the arm could manage to dig a shallow angled trench and the probe can be knocked into that trench it might be possible to hammer it laterally to get it digging again. I don't know if that is within the arm's capabilities; it certainly wasn't designed for it.