NASA To Try Powering Mars Rover "Spirit" Out of Sand Trap

coondoggie writes "NASA's long-running Mars rover Spirit is stuck in a sand trap — a situation the space agency would like to fix. Yesterday NASA said it will begin what it called the long process of extricating Spirit by sending commands that could free the rover. Spirit has been stuck in a place NASA calls 'Troy' since April 23, when the rover's wheels broke through a crust on the surface that was covering bright-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap. Driving was suspended to allow time for tests and reviews of possible escape strategies, NASA stated."

Comments

Oh no

[MichaelSmith]

Methinks it is time for somebody to get out and push.

AAA's new market

[Dayofswords]

Mars is the new frontier for the AAA people to explore.

Up next:OnStar

Re:NASA Quality & Space Commercialization

[jdigriz]

Guys, the 90-day planned lifespan of the rovers was pure politics. Congress wouldn't have gone for, "Yeah, we're gonna need funding for the next 5 years." if told so up-front. At the same time, it wouldn't have made sense to allocate that money from the beginning since there was a non-zero chance that the rovers might auger in, like the Mars Polar Lander did, and that none of that funding for surface ops would be needed after all. So they built the rovers, said "Well, if we get 90 days out of them, we can declare Mission Accomplished." and went with it. Since they were solar-powered there's no particular reason that they would last only that long. 90 days was a classic case of "underpromise and overdeliver." If there had been some sort of catastrophic design flaw and they failed after only 30 days they could have claimed to have succeeded with 1/3 of the mission objectives, etc.

Re:It's a conspiracy!

[hazee]

I fail to see why it takes Diego Maradona to free the rover, wherever it is.

Re:Use the arm ?

[ScottMaxwell]

Using the arm to help isn't completely off the table, but pretty close, largely for reasons you conjectured about in your post. First, we can't actually push while driving, because the motor controllers are shared between the arm and the wheels -- you can run one or the other, but not both at once.

We could, potentially, push down with the arm to lift Spirit slightly, then run the wheels. But Spirit's just not strong enough to make much difference. :-) In the best case, we can push down with maybe 70N of force, and that's if we had a hard surface to push on. (But if we had a hard surface to push on, we probably wouldn't be mired in this stuff in the first place.) For comparison, you'd need to apply ~ 650N to completely lift Spirit, so the arm can apply only about 1/10 of the needed force. As you can see, she wasn't designed to do one-handed push-ups. :-)

Further, doing so would pose a high risk of damage to the arm itself, and since four of Spirit's science instruments -- about 2/3 of the total science payload -- live on the end of that arm, the potential downsides are quite significant.

In addition, it's not completely clear that pushing down with the arm to partially lift Spirit would actually help: one effect of that would be to reduce the traction on the wheels, and not having enough traction is one of our big problems here.

Resculpting the terrain is a less unlikely scenario, but something we're keeping in our back pocket for now. There are few suitable rocks within reach, we've never tried it and (again) would risk damaging the arm by doing so, and on top of all that we don't even know if it would actually help, since the rocks might simply slip quickly under the wheels without moving us forward much. Even so, if things get desperate enough, we might possibly try that one.

The soil we're stuck in is very weird, and has some counterintuitive properties. It doesn't work like dirt or mud. We mixed up a batch of simulant to drive our test rover in, and while there are known differences between the simulant and the real soil, the experience of working with the simulant is quite illuminating. The stuff feels like flour and flows like water: run your hand through it, and it flows away from you like water does, it just stops moving sooner. Weird, weird stuff.