Curiosity team working to resume drilling
Engineers with NASA’s Curiosity Mars rover team are working to restore the rover’s sample-drilling capability by using new techniques. Use of the drill has been suspended due to a mechanical problem with the arm that first occurred late last year.
While the earliest that drilling for rock samples can resume is still several months away, mission managers are enthusiastic about successful Earthbound tests of techniques to work-around problems with the drill’s feed mechanism. The most recent development is a preparatory test on Mars.
“We’re steadily proceeding with due caution to develop and test ways of using the rover differently from ever before, and Curiosity is continuing productive investigations that don’t require drilling,” said Deputy Project Manager Steve Lee, of NASA’s Jet Propulsion Laboratory (JPL), in Pasadena, California, via a release issued by the agency.
On Oct. 17, 2017, Curiosity touched its drill to the Martian surface for the first time in 10 months. The rover pressed the drill downward, and then applied a smaller amount of sideways force while taking measurements with a force sensor.
“This is the first time we’ve ever placed the drill bit directly on a Martian rock without stabilizers,” said JPL’s Douglas Klein, chief engineer for the mission’s return-to-drilling development. “The test is to gain [a] better understanding of how the force/torque sensor on the arm provides information about side forces.”
The force sensor provides the arm with feedback about how hard it is pressing down or sideways. To keep the drill bit from getting stuck in a rock, it is important to avoid too much side force both while drilling into a rock and while extracting the bit.
Curiosity’s drill has two contact posts, known as stabilizers, one on each side of the bit, that are placed on the target rock while the bit is in a withdrawn position. At this point, the drill’s motorized feed mechanism would extend the bit forward and the bit’s rotation and percussion actions drill a hole in the target rock. Curiosity used its drill to obtain sample material for 15 Martian rocks between 2013 and 2016.
In December of 2016, the drill’s feed mechanism stopped working reliably. After investigating the possibilities of restoring the feed mechanism’s reliability or using it in a less-than-reliable configuration, the team prioritized developing an alternative method of drilling without the use of the feed mechanism. In the alternative method, called “feed-extended drilling“, the stabilizers are not used to touch the target rock. The bit is advanced into a rock by Curiosity’s robotic arm rather than the drill’s feed mechanism.
“We’re replacing the one-axis motion of the feed mechanism with an arm that has five degrees of freedom of motion,” Klein said. “That’s not simple. It’s fortunate the arm has the force/torque sensor.”
The sensor’s original purpose was to monitor so in excess of expectations that it would automatically stop all arm motion for the day. The new feed-extended drilling technique uses this method to compensate for side loads. The preparatory test on Mars will help engineers determine the most effective way to use data from the sensor.
Engineers tested the feed-extended method at JPL using a near-twin of the Curiosity rover. The team also developed methods for delivering drilled samples to the laboratory-instrument inlets on the rover’s deck without the use of the drill’s feed mechanism.
“The development work and testing here at JPL has been promising,” Lee said. “The next step is to assess the force/torque sensor on Mars. We’ve made tremendous progress in developing feed-extended drilling, using the rover’s versatile capabilities beyond the original design concepts. While there are still uncertainties that may complicate attempts to drill on Mars again, we are optimistic.”
Curiosity is currently nearing the top of “Vera Rubin Ridge“, a 20 story-ridge on lower Mount Sharp. The rover has been studying the extent and distribution of the iron oxide mineral hematite in the rocks that make up the ridge.
On Tuesday, Oct. 24, the Curiosity team had planned to use the SAM instrument suite to analyze a sample of Martian sand from a location called “Ogunquit Beach” that the rover had visited in late March. However, technical issues with NASA’s Deep Space Network prevented the team from sending commands to the rover. If everything goes as planned, those science activities will be retried in the next few days.
Video courtesy of NASA’s Jet Propulsion Laboratory
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.