It’s been an eventful a number of Martian days, or sols, since our final weblog put up, so we wished to offer everybody with an replace on the place issues stand on Mars. In our final put up, we defined that we have been on the point of start flying with a better rotor pace to compensate for reducing atmospheric density attributable to seasonal adjustments on Mars. Rising the rotor pace is a major change to how we’ve been flying to date, so we wished to proceed ahead rigorously. The first step was to carry out a high-speed spin take a look at at 2,800 rpm on the bottom and, if all the things went properly, step two was to carry out a short-duration flight, briefly hovering over our present location, with a 2,700 rpm rotor pace.
The high-speed spin take a look at was accomplished efficiently on Sept. 15, 2021 at 23:29 PDT, 11:11 LMST native Mars time (Sol 204 of the Perseverance mission). Ingenuity’s motors spun the rotors as much as 2,800 rpm, briefly held that pace, after which spun the rotors again all the way down to a cease, all precisely as sequenced for the take a look at. All different subsystems carried out flawlessly. Of specific curiosity was figuring out whether or not the upper rotor speeds trigger resonances (vibrations) in Ingenuity’s construction. Resonances are a typical problem in aerial rotorcraft and might trigger issues with sensing and management, and can even result in mechanical harm. Thankfully, the information from this newest high-speed spin confirmed no resonances on the increased rotor rpm’s. The profitable high-speed spin was an thrilling achievement for Ingenuity and gave us the inexperienced mild to proceed to a take a look at flight with a 2,700 rpm rotor pace.
The take a look at flight was scheduled to happen on Sept. 18, 2021 (Sol 206) and was alleged to be a quick hover flight at 16 toes (5 meters) altitude with a 2,700 rpm rotor pace. It turned out to be an uneventful flight, as a result of Ingenuity determined to not take off. Right here’s what occurred: Ingenuity detected an anomaly in two of the small flight-control servo motors (or just “servos”) throughout its computerized pre-flight checkout and did precisely what it was alleged to do: It canceled the flight.
Ingenuity controls its place and orientation throughout flight by adjusting the pitch of every of the 4 rotor blades as they spin across the mast. Blade pitch is adjusted by means of a swashplate mechanism, which is actuated by servos. Every rotor has its personal independently managed swashplate, and every swashplate is actuated by three servos, so Ingenuity has six servos in whole. The servo motors are a lot smaller than the motors that spin the rotors, however they do an amazing quantity of labor and are crucial to steady, managed flight. Due to their criticality, Ingenuity performs an automatic verify on the servos earlier than each flight. This self-test drives the six servos by means of a sequence of steps over their vary of movement and verifies that they attain their commanded positions after every step. We affectionately check with the Ingenuity servo self-test because the “servo wiggle.”
The information from the anomalous pre-flight servo wiggle reveals that two of the higher rotor swashplate servos – servos 1 and a pair of – started to oscillate with an amplitude of roughly 1 diploma about their commanded positions simply after the second step of the sequence. Ingenuity’s software program detected this oscillation and promptly canceled the self-test and flight.
Our crew continues to be wanting into the anomaly. To collect extra information, we had Ingenuity execute extra servo wiggle checks throughout the previous week, with one wiggle take a look at on Sept. 21, 2021 (Sol 209) and one on Sept. 23, 2021 (Sol 211). Each of the wiggle checks ran efficiently, so the difficulty isn’t completely repeatable.
One idea for what’s taking place is that shifting components within the servo gearboxes and swashplate linkages are starting to point out some put on now that Ingenuity has flown properly over twice as many flights as initially deliberate (13 accomplished versus 5 deliberate). Put on in these shifting components would trigger elevated clearances and elevated looseness, and will clarify servo oscillation. One other idea is that the high-speed spin take a look at left the higher rotor at a place that hundreds servos 1 and a pair of in a singular, oscillation-inducing means that we haven’t encountered earlier than. We now have quite a lot of instruments out there for working by means of the anomaly and we’re optimistic that we’ll get previous it and again to flying once more quickly.
Our crew could have a number of weeks of time to finish our evaluation as a result of Mars will probably be in photo voltaic conjunction till mid-October, and we gained’t be uplinking any command sequences to Ingenuity throughout that point. Conjunction is a particular interval through which Mars strikes behind the Solar (as seen from Earth), making communications with spacecraft on Mars unreliable. Ingenuity is not going to be utterly idle throughout this time, nevertheless; Ingenuity and Perseverance will probably be configured to maintain one another firm by speaking roughly as soon as every week, with Ingenuity sending primary system well being info to its base station on Perseverance. We’ll obtain this information on Earth as soon as we come out of conjunction, and can learn the way Ingenuity performs over an prolonged interval of relative inactivity on Mars. See you on the opposite aspect of conjunction!