Trailblazer
Lengthy earlier than Ingenuity’s historic first flight on Mars, engineers at NASA’s Jet Propulsion Laboratory in Southern California and their collaborators at AeroVironment Inc. have been already shifting the boundaries of human data and aeronautic achievement with testing right here on Earth. Flights by an Ingenuity prototype in 2016 confirmed that managed, aerodynamic flight was potential in a Mars-like ambiance for the primary time. These flights have been made potential by JPL’s 25-foot thermal-vacuum chamber, which is able to replicating environments with all kinds of temperatures, pressures, and compositions. Regardless of being one of many largest thermal-vac chambers on the planet, it was nonetheless too small for important horizontal movement, principally limiting check flights to easy hovering. Engineers labored round this to some extent by constructing a customized wind wall to simulate Martian winds and the aerodynamic situations seen in ahead flight. Right here, too, there have been limits in how a lot and the way nicely the situations of Mars may very well be examined. Finally, the helicopter nonetheless had a lot to show when it spun up its rotors for its first actual flight check on the planet for which it was designed. This historic first flight on April 19, 2021, was carried out flawlessly, matching its efficiency in numerous chamber checks nearly precisely.
That first, modest 3-meter (9-foot) hover flight, although spectacular, was nonetheless fairly removed from testing Ingenuity’s limits. Over the following six months, the Ingenuity staff methodically probed the helicopter’s skills, pushing it just a bit more durable with every flight. Altitude was elevated to five meters on Flight 2, after which 10 meters on Flight 5. Ahead flight was tried for the primary time on Flight 2 at a cautious 0.5 m/s. By Flight 10, Ingenuity was flying at an altitude of 12 meters (40 toes) and a velocity of 5 meters per second (11 mph), displaying simply how far engineers from NASA and AeroVironment had pushed her since these early chamber checks half a decade earlier.
These early-mission data would stay largely in place for the following 12 months because the Ingenuity staff transitioned the car from a easy expertise demonstrator (akin to the primary Wright brother’s airplane) to a practical science and scouting asset on the floor of Mars. Studying methods to coordinate the actions of the rover and the helicopter to benefit from Ingenuity’s distinctive capabilities (and limitations) took effort and time. To know the audacity of the try, one may think how troublesome it could have been to aim to offer common business passenger service with the Wright Flyer in 1903.
Reaching the bounds
By early 2023, Ingenuity discovered itself actually racing for its life up the Jezero river delta, and the bounds imposed by these early-mission velocity/altitude data made it troublesome to remain forward of the rover within the slim channels of the Jezero delta. To know the mission impacts of Ingenuity’s flight envelope, it’s crucial to debate the overall set of constraints that form the method of flight planning for Ingenuity.
- Power – Flights draw monumental quantities of power from the onboard battery in a brief time period. Because the battery is discharged throughout a flight, its potential to help these excessive energy ranges additionally decreases. Beneath a sure degree, the battery gained’t have the ability to meet the facility wants of the helicopter, resulting in destabilization or a system-wide brownout, each of which might lead to a crash.
 - Warmth – Flights generate important warmth in varied parts of the helicopter. If flights proceed for lengthy intervals of time, parts might start to overheat and fail, leading to a crash. The time when this might happen relies on the parts’ beginning temperature, the setting through which they’re working, and the precise composition of the flight.
 - Terrain – Martian terrain instantly impacts navigation efficiency, and extremely variable terrain may cause management effort spikes which additionally create energy spikes that the battery must help. As well as, sufficiently rock-free airfields outline the set of paths accessible to the helicopter.
 - Security and Touchdown Accuracy – The constraints and capabilities highlighted above can drive Ingenuity far off beam, even when not severely sufficient to interrupt the flight. This might outcome within the helicopter touchdown in an unsafe location, leading to a crash. All flights should be studied prematurely to make sure car security through the flight and at touchdown.
The frequent denominator in all these constraints is time. Saving flight time saves power, reduces heating, and offers extra freedom to make use of slower speeds to tiptoe round disruptive terrain which may in any other case endanger or considerably degrade the touchdown accuracy of the helicopter. Larger speeds and better accelerations cut back the time wanted to execute a given flight path. Larger altitudes allow greater speeds, as the broader discipline of view helps to maintain floor options in view of Ingenuity’s navigation digital camera longer, counteracting the impact of elevated velocity. Increasing Ingenuity’s flight envelope had the potential to loosen up flight planning constraints and permit Ingenuity to function extra successfully alongside Perseverance. The staff resolved to vary focus, actively on the lookout for alternatives to renew testing and broaden the flight envelope. Ingenuity would as soon as once more return to the enterprise of pushing the boundaries of Martian flight and setting numerous flight data alongside the way in which.
A Return to Kind
This new strategy began paying dividends on Flight 45, the place new data for each velocity and acceleration have been set. Most flight velocity was elevated to six m/s and horizontal acceleration was elevated from the earlier most of 0.75 m/s^2 (first utilized in Flight 25’s record-setting run throughout Seitah) to a brand new, extra aggressive 0.85 m/s^2. Shortly afterwards, throughout Flight 49, the utmost velocity was elevated to six.5 m/s with a hover of 16 meters on the finish of the flight. The utmost altitude ceiling was pushed out once more simply 10 days later throughout Flight 50 with a 2-meter improve to 18 meters.
Nonetheless, such work was troublesome to do whereas sustaining Ingenuity’s regular operational schedule. Important effort is required to maintain Ingenuity flights synchronized with the rover’s actions over troublesome terrain whereas staying in communications vary. Lastly, as Perseverance approached the Mandu Wall area in September of 2023, the Ingenuity staff noticed the chance we would have liked. The comparatively permissive communications setting and flat terrain round Jurabi Level supplied the proper setting to carry out the kind of testing that the decrease Jezero delta areas had made so troublesome.
Considerably sarcastically, for all of the deal with flying quicker, one of many highest-priority checks concerned decreasing the vertical touchdown velocity under the usual 1 m/s descent price. This functionality was a precedence for the following deliberate Martian helicopter, the Pattern Restoration Helicopter (SRH), which is being designed to retrieve the pattern tubes dropped by Perseverance. The preliminary design of SRH makes use of Ingenuity as a place to begin however carries additional mass within the type of a robotic arm and wheels wanted to allow pattern retrieval together with the pattern tube itself. These additions improve the anticipated stress on the touchdown gear throughout landing. A softer touchdown could be simpler on the touchdown gear however more durable for the landing detection algorithm to determine, and, on the extremes, may end up in multi-contact occasions that would trigger a crash. On Earth, touchdown at Mars gravity ranges is troublesome to check in a sensible method and should as a substitute be partially examined throughout a number of venues. Happily, we have already got a flying car on Mars and the staff might use Ingenuity as a testbed, gathering actual world information on touchdown speeds wanted by the SRH mission. After cautious examine and re-tuning parameters round a 0.75 m/s descent velocity, Flights 57-59 demonstrated the delicate landing on each flat and sloped terrain.
Flight 59 additionally served the aim of accelerating the utmost altitude at hover to twenty meters, permitting ahead flight as much as 16 meters. Usually, 4 to six meters of altitude ceiling are held in reserve to account for slant vary when tilted and for variable terrain and the ensuing management system response. This enabled Flight 60 to set a brand new most velocity report of 8 m/s because the helicopter flew to Jurabi Level. Flight 61 was a near-repeat of 59 that additional expanded the flight regime. The ascent velocity was elevated to 1.5 m/s and descent velocity to 1.2 m/s, each beforehand simply 1 m/s, saving round 10 seconds on the standard flight. The flight additionally achieved the very best altitude thus far at 24 meters. This was a big milestone because it surpassed the analytical worst-case drop-out of the laser vary finder (LRF) which is used to measure Ingenuity’s altitude above floor degree. If the LRF drop-out extends longer than 2 seconds, the helicopter will fault and land (seemingly secure within the case of a hover flight, however presumably deadly throughout ahead flight). This altitude additionally enabled the staff’s aim of ahead flight at 10 m/s demonstrated in Flight 62 at an altitude of 18 meters in ahead flight. After all, Ingenuity hadn’t forgotten its companion on the Crimson Planet. In the midst of this record-setting flight, Ingenuity managed to seize a number of high-resolution pictures of the Jurabi Level area many sols forward of the rover’s arrival.
In abstract, this flight check marketing campaign has been an incredible success, proving that our intrepid rotorcraft continues to be able to breaking data and pushing the envelope 2 ½ years after touchdown on Mars. During the last 9 months, the Ingenuity staff has doubled our most flight altitude restrict from 12 to 24 meters, almost doubled our max velocity from 5.5 m/s to 10 m/s, elevated our most horizontal and vertical acceleration, and validated each soft- and hard-landing approaches. Regardless of this speedy tempo, the staff isn’t slowing down. We intend to maintain pushing to see what new issues may be discovered and what new capabilities may be mastered with our small helicopter on the Crimson Planet.
