Ground too hard for Curiosity’s drill

A second drill attempt by Curiosity, using an improvised drilling technique designed to bypass the failure of the drill’s feed mechanism, once again failed to drill deep enough to obtain a sample.

After two drilling attempts, Curiosity’s drill was not able to dig into the bedrock sufficiently to collect a sample of rock at this location. Curiosity’s engineers are continuing to refine the new drilling method. In the future, this might include adding percussion, which could enable drilling into harder rock.

Either the ground on Vera Rubin Ridge is too hard for Curiosity’s drill, or the new drilling technique does not allow the drill to push with the same force as previously. The update at the link implies the former, but I suspect the latter is a factor as well.

Curiosity attempts to drill with improvised technique

The Curiosity engineering team has made the first attempt to drill in more than a year, using an improvised technique that has the rover arm push the bit into the ground rather than its presently non-function feed mechanism.

This early test produced a hole about a half-inch (1-centimeter) deep at a target called Lake Orcadie — not enough for a full scientific sample, but enough to validate that the new method works mechanically. This was just the first in what will be a series of tests to determine how well the new drill method can collect samples. If this drill had achieved sufficient depth to collect a sample, the team would have begun testing a new sample delivery process, ultimately delivering to instruments inside the rover.

According to the mission update page, for some reason the drill was unable to penetrate the ground very deeply.

They plan to do more tests, with the goal of eventually getting a hole deep enough to provide good samples.

Curiosity science team to attempt first drilling in a year

After a year of tests and engineering rethinking, the Curiosity science team has decided to attempt drilling its first hole in more than a year.

From yesterday’s Curiosity mission update:

Because there is only so much data volume and rover power to go around, performing drill activities must temporarily come at the expense of scientific investigations (although you’d be pressed to find a disappointed science team member this week, as the drilling campaign will bring loads of new scientific data!). As a result, with the exception of some environmental observations by the Rover Environmental Monitoring Station (REMS) instrument, today’s plan does not have any targeted scientific observations within it. Today will instead be dedicated to drill preload activities and imaging for engineering and rover planning purposes in preparation for a full test of the revised drilling operations.

The problem with the drill has been its feed mechanism, the equipment that moves the drill downward into the hole. As designed the robot arm would get planted on the surface to provide stability for the drill, which as it drilled would be pushed downward that that feed mechanism. Last year they found something had clogged that mechanism so that it would not retract properly.

From what I understand, what they have tested and have decided to try instead is to place the drill against the surface in an extended position, and use the arm itself to push the bit downward. The concern is whether the arm can hold the drill steady. They have done some tests and think it can. We shall soon find out.

Drill issues at Curiosity

The recent failure by Curiosity to drill has caused engineers to stop the rover in its tracks while they analyze the cause of the problem.

The rover team learned Dec. 1 that Curiosity did not complete the commands for drilling. The rover detected a fault in an early step in which the “drill feed” mechanism did not extend the drill to touch the rock target with the bit. “We are in the process of defining a set of diagnostic tests to carefully assess the drill feed mechanism. We are using our test rover here on Earth to try out these tests before we run them on Mars,” Curiosity Deputy Project Manager Steven Lee, at NASA’s Jet Propulsion Laboratory in Pasadena, California, said Monday. “To be cautious, until we run the tests on Curiosity, we want to restrict any dynamic changes that could affect the diagnosis. That means not moving the arm and not driving, which could shake it.”

Two among the set of possible causes being assessed are that a brake on the drill feed mechanism did not disengage fully or that an electronic encoder for the mechanism’s motor did not function as expected. Lee said that workarounds may exist for both of those scenarios, but the first step is to identify why the motor did not operate properly last week.

Though they do not say so, the problem is almost certainly related to a fundamental design flaw in the drill’s design that causes intermittent short-circuits when they use it, and has the possibility of shorting out the entire rover if they are not careful.

Drill design flaw source of short circuit on Curiosity

NASA engineers have confirmed that the rover’s drill is the source of the intermittent short circuit that forced them to shut down Curiosity temporarily.

“The most likely cause is an intermittent short in the percussion mechanism of the drill,” Erickson said in a statement. (Curiosity’s drill doesn’t simply rotate; it hammers into rock, via that percussion mechansism, as well.) “After further analysis to confirm that diagnosis, we will be analyzing how to adjust for that in future drilling.” A brief short occurred during a test on Thursday (March 5) that used the drill’s percussive action, NASA officials explained.

This is not a surprise, as it has been known since before launch that a design flaw in the drill could cause short circuits, possibly serious enough to permanently shut down the rover. They have thus used the drill much less than they had originally planned, and with great care.

Once they get a handle on the specifics causing this short, they say that Curiosity will go back into operation. However, I suspect that they may no longer use the drill, or if they do, they will use it under very very very limited circumstances.

Engineers commanded Curiosity to drill its third drill hole on Tuesday on what looks like an outcrop of sandstone in Gale Crater.

Engineers commanded Curiosity to drill its third drill hole on Tuesday on what looks like an outcrop of sandstone in Gale Crater.

This hole is shallow and is merely a test to see if a deeper full bore would be worthwhile geological.

That Curiosity has only drilled three holes, and is now only doing a test bore first is partly because engineers fear that using the drill too much will cause a short circuit that will disable the rover entirely. This fear is because of a design flaw in the construction of the rover and the drill.

After resuming drilling in Seattle — and only going four feet — Bertha has been stopped again.

After resuming drilling in Seattle — and only going four feet — Bertha has been stopped again.

High temperatures near the machine’s cutting face prompted contractors to stop mining after the drill advanced a total of 4 feet in test runs Tuesday and Wednesday. And that ended Bertha’s attempt to resume mining after an eight-week layoff.

The earlier stoppage remains unexplained. They found some concrete chunks and steel pipe sections in the way, but nothing that could have explained why the drill was blocked. Now the high temperatures pose a more significant problem, as they suggest there is something technical wrong with the giant drill.