Mars Rover Spirit Down a Wheel

riflemann writes "NASA is reporting that two years into its 90-day mission, Spirit has lost one wheel and is now running on five wheels, dragging the broken wheel. With this reduced mobiity, the rover still needs to make its way to a slope where it can catch enough sun over the Martian winter to keep it operating. 'Even though the rovers are well past their original design life, they still have plenty of capability to conduct outstanding science on Mars.', says project leader Dr. John Callas."

Comments

Cold

[MichaelSmith]

Its almost winter in the southern hemisphere of Mars. I wonder if there is a chance that a contact has contracted in the cold enough to break off power to this motor. Who knows? Spirit has been lucky before. Perhaps this wheel will start working again in the summer.

Failing that I am available to fix the broken motor, assuming that NASA can provide transportation :)

Re:At first read, I get dissapointed

[partymonkey]

Maybe it's just me, but I doubt they spent all that money on the rovers for just 90 days of operation. I'd be willing to bet that they designed them to last 3-5 years. Also, they were probably just setting expectations *really* low, so if the rovers failed early then they still looked good in the public eye.

Failed brushes?

[dougmc]

"It is not drawing any current at all," said JPL's Jacob Matijevic, rover engineering team chief. One possibility engineers are considering is that the motor's brushes, contacts that deliver power to the rotating part of the motor, have lost contact.

Brushless motors are generally 1) more efficient and 2) longer lasting (with no brushes to wear out) and 3) more expensive (especially when you include the ESC, electronic speed control) than otherwise similar brushed motors. (But when you send something into space, who cares about an extra $1000 on motors?) I'm rather surprised that they didn't go brushless in something like this. Brushless motors are also cleaner, as there's no brushes to wear down over time. This is critical in zero gravity environments like orbit (nobody wants brush-dust floating around) and wouldn't be so important on Mars, but even so ... I wonder why they used brushed motors. Even if they things weren't supposed to last very long, you'd think brushless motors would be more efficient, giving them some extra power to work with, for not much extra money.

(My experience with brushed and brushless motors comes from R/C planes, where a brushless motor is sometimes twice as powerful and 50% more efficient than a similarly sized brushed motor. Of course, a large part of this is that the brushed motor is dirt cheap, made cheaply in every way, and the brushless motors are of higher quality, but even so, even when comparing high quality stuff (and not cheap speed 400 can motors) the brushless are signifigantly better.)

Re:Failed brushes?

[Anonymous Coward]

Actually, having recently heard a talk with people from JPL I can tell you why. They went with brushed motors because it was what had been previously used and was, therefore, seen as a safe option. For future robotic missions they plan on using brushless motors.

Re:Failed brushes?

[v1]

Brushless motors are more complex, and require an array of active electronics inside them to produce the AC and modulating magnetic field they need to operate. Most brushless motors are lower torque than their brushed counterparts. (majority, I know there will be exceptions) Brushed motors are more mechanical in nature and suffer from the usual mechanical issues, but they are less prone to failure than brushless. Also, traveling through space and landing on a planet that may not have a protective magnetic field, active (transistor based) electronics must be carefully protected against emi that can disable or damage them.

I'm sure they went brushed for a variety of very good reasons. The technology of brushless was available when the rovers were designed, and I can't imagine NASA not seriously considering them.

all alone in the cosmos

[JTW]

The rovers are interesting critters.. not unlike their older sibling Pioneer 10.

I guess we've given up on artificial intelligence, but I rather think what we altogether thought was a mind of information is actually a mind of situation and evolving spirit that simply exists in the moment. If that be true, even an Ant could have artificial intelligence.

Its interesting we drive these things into the ground, or until they run out of power, or we loose interest.

It may be lame, But I'd think it might be more interesting in the long run to upload a final survival program into these critters and turn them loose.. perhaps in the long run we'll come to those ideas and terms. Perhaps years from now when astronauts decide to land there they really will find martians!

Of course if we have a nuclear or biological melt down, then perhaps they will out live us.

There was a SciFi story long ago called NightFall.. it would make an interesting animated short or story to tell the story from the rovers perspective... and in the end they are given their freedom and continue to look up at the night to the twinkle in the sky where their makers live, and then.. they loose contact, perhaps they merely lost interest in their creations.. or perhaps the makers are no more, and they truly are all alone.. and as the cold surrounds and grips them they fold up their solar wings preparing for another martian winter and the rovers go to sleep.. perchance to dream.. of other worlds.

Even if it can't make it up the slope...

[artifex2004]

Why would the rover actually permanently die if it ran out of power?
Surely when the Martian winter comes to an end, and the area it's in is flooded with sunlight again, the solar cells could still work, the battery could recharge, and it could wake up?

Or did nobody think about a cold restart?