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comment by mk
mk  ·  1561 days ago  ·  link  ·    ·  parent  ·  post: NASA's Mars Lander 'Mole' Is Digging Again as Marsquake Mystery Baffles Scientists

It seems odd to me that "bouncing out" was a possibility allowed by the engineering. I would think that the possible force vectors would be diagrammed, and different combinations modeled out.





kleinbl00  ·  1561 days ago  ·  link  ·  

    Kinda seems like this was a project that wasn't all that well researched in 1997 and has made the rounds ever since.

Tent stakes are not new tech yet I can't find any evidence of anyone ever making a self-driving one. I'm not convinced that there was a lot of testing of this thing; I can't imagine it working in my back yard and I've got 60% more gravity to work with.

FIFTEEN FEET. The thing is supposed to penetrate fifteen feet of unknown dirt. Not "dig", penetrate.

http://esmats.eu/amspapers/pastpapers/pdfs/2016/grygorczuk2.pdf

It's got a Maxon DCX-22 motor - this one - which is 22mm in diameter. It's basically driving an impact wrench that isn't twisting. At all.

Near as I can tell that motor tops out at 14W. That's about a 0.02 HP motor. The paper lists a 0.7W duty cycle every four seconds. Which has to generate enough force to compress a spring that can force what's effectively a paper towel tube through fifteen feet of unknown dirt. Yet that scientific paper mostly talks about coatings, as if the science of a self-hammering tent stake was settled.

Apparently it was sold as a "mobile penetrometer." When you search for that on Youtube you get stuff like this:

I find it hard to avoid the conclusion that NASA flew an experiment that had never been tested nor even seriously evaluated.

user-inactivated  ·  1561 days ago  ·  link  ·  

Mumbemumble years of government tech projects, though not nearly as interesting as NASA, says someone who worked on the project when they started out at NASA moved up the chain, and it remained their pet project. At some point you just let the PHBs have their thing even if it's stupid, because they have enough clout to be an even bigger pain in your ass than doing the stupid thing will be. If you're lucky letting them have the stupid thing will get rid of both the stupid project and the PHB.

kleinbl00  ·  1561 days ago  ·  link  ·  
goobster  ·  1561 days ago  ·  link  ·  

It did bounce around for like 10 years, or something, and was supposed to go to Venus, then the Moon, and finally Mars.

My guess is that the tech hasn't been updated, because the nature of NASA projects is that if you change ANYTHING, you have to resubmit the project like an entirely new one. So old shit is constantly getting flown, simply because it has weathered the test of time... and zero advancement/innovation/improvement.

kleinbl00  ·  1561 days ago  ·  link  ·  

'97 if I recall correctly. Thing is? It's newtonian physics. You would literally assign this as an undergraduate engineering problem. If you have the mass of the hammer, the area of the piton, the coefficient of the point and the coefficient of the cylinder you can calculate whether it would work. Better yet, arrange the equation as a function of static/dynamic coefficients of friction and solve for maximum coefficient of friction for it to work, then compare with existing measurements. Nothing here is beyond good old fashioned quadratic equations.

Imagine if the CIA had a self-burying contact mic. How ubiquitous would that thing be? What about a device that could pull its own data cable? The level of specialization here should be available at Home Depot.

I don't see how it survived basic feasibility. Either I am missing something major and obvious or this thing wasn't so much "designed" as "hoped" into existence.

Devac  ·  1561 days ago  ·  link  ·  

The funny thing is that only about a year after that hammer paper was published, researchers found out that Martian soil simulant can be compressed into hard bricks through hammering.

Maybe we really shouldn't into space.

kleinbl00  ·  1560 days ago  ·  link  ·  

LOL they think martian soil is adobe. Because why wouldn't it be. You can do that with "dirt" all over the American Southwest because it's volcanic.

    The engineers believe that the iron oxide, which gives Martian soil its signature reddish hue, acts as a binding agent. They investigated the simulant's structure with various scanning tools and found that the tiny iron particles coat the simulant's bigger rocky basalt particles. The iron particles have clean, flat facets that easily bind to one another under pressure.

That's gonna respond real well to shear and lateral compression.

I keep thinking back to the power profile of that little thing - it's not even a cordless screwdriver. It's like an electric toothbrush. That is somehow supposed to drive itself through sixteen feet of dirt. And NASA people are generally smart so I keep wondering what the fuck I'm missing.

Here it is working.

goobster  ·  1560 days ago  ·  link  ·  

Alright. This just got weirder.

This project is NOT American. It's not some dopey narrow-minded NASA geek, who has never been outside of ABQ, designing something definitely unworkable.

It's GERMAN.

Now THAT makes it even MORE complexing! What the hell are we missing here...? Who thought this was a good idea? How was it tested? What types of calculations did they make to allow for the lower gravity, and composition of the Martian soil? Or if it happens to hit a sub-surface PEBBLE 3 inches down in its 5-meter journey??

kleinbl00  ·  1560 days ago  ·  link  ·  

Penetrator is Polish, yo.

goobster  ·  1560 days ago  ·  link  ·  

Oh right. Misread that. The heat sensor is German/ESA. The penetrator is...

... nah... let's just let the last word be penetrator

kleinbl00  ·  1560 days ago  ·  link  ·  

I suspect that diffusion of responsibility has been a major theme throughout this particular instrumentation package.