At some point it had to happen: bad weather, flight painted. Annoying, but it would be nothing unusual if the flight should not have been going from an extremely remote airport. The dusty airfield »Airfield L« is 350 million kilometers from all earthly airports on Mars. At the beginning of January 2022, the little helicopter »Ingenuity« was to take off from there to another historical flight. It would have been flight number 19. But then a dust tower braked the record hunt, the next travel option should only be available a few weeks later. It was the first weather -related flight loss on another planet. A premiere.
And not the only one. Ingenuity has been flying over Mars for about a year now, setting record after record. Originally planned as a technology demonstrator, which was supposed to accomplish the first controlled and independent flight on another celestial body, the mini-helicopter has long since found a new purpose: the team of the Jet Propulsion Laboratory (JPL) in Pasadena, California, which operates the aircraft, calls it the "operational demonstration phase". On the one hand, it is about gaining experience on how helicopters could be helpful in the future in the exploration of Mars and other celestial bodies. On the other hand, it is about flight schedules and landing sites, ranges and departure times, temperature, atmospheric pressure and, last but not least, the weather.
When Ingenuity threw his two opposite rotors for the first time on April 19, 2021 to rise above the Mars dust for 39.1 seconds, very few would have thought that they would still deal with the mini -helicopter a year later . It was unclear whether ingenuity could even stand out in the thin air. Compared to the earthly air envelope, the atmosphere on the red planet generally only has a density of less than one percent; It is like flying on earth at a height of 30 kilometers. Although the attraction on Mars - about 40 percent of earthly value - is also less of a good effect, but which alone does not compensate for the lack of buoyancy.
The JPL team therefore relied on extreme lightweight construction. The result was a flying machine weighing 1.8 kilograms, with a height of half a meter and a wingspan of the rotor blades of 1.2 meters. They rotate about their axis about 2400 times per minute, much faster than the rotors of terrestrial helicopters. Ingenuity also has to fly independently, it is not possible to think of a remote control due to the minute-long transit time of all radio signals from Earth to Mars. The team only uploads the desired waypoints, the start time and the planned speed before the start. The rest is taken over by Ingenuity, in German roughly: "ingenuity" or "ingenuity".
On the way to the Jezero crater, Ingenuity made a record flight
"The whole thing runs under the motto: high risk, high chances," chief engineer Bob Balaram had told in an interview before the first flight. The team was to be given 30 days for their risky adventure, then the JPL wanted to devote its undivided attention back to the Mars rover Perseverance, which had brought Ingenuity to the Red Planet. A maximum of five flights were planned - provided everything went smoothly.
Ingenuity flight number 25 completed at the beginning of April.
It was a record flight again: the helicopter covered around 700 meters, more than ever in one piece. The speed has also reached almost 20 kilometers per hour. However, the new top performance was only a means to an end: Ingenuity is on the way to a dry river delta in the Jezero crater, as the playing field of the mini helicopter is called. The Rover Perseverance, which is primarily supposed to search for traces of former life on Mars, is also on the way to this delta.
Ingenuity's task: The helicopter should explore the area out of the air in advance and give tips on which of two former river arms should best choose on its way. In the aerial photographs, the science team also wants to search for worthwhile goals to explore the rover. In the future, Ingenuity, the mission of which NASA has extended until September 2022, will even explore regions from the air that are too rugged to control it safely.
All this is far from Ingenuity's original tasks: the project is "exclusively a technology demonstration" and in no way intended to support Perseverance's scientific mission, NASA had emphasized before the first flight. This is the past. However, the new challenges are correspondingly great: "Since our first flight, we have learned a lot about operating a helicopter on Mars, about its strengths and its weaknesses," writes chief pilot Håvard Grip on the JPL blog. "However, flying is also becoming more and more difficult every day.«
Ingenuity is not made for hilly terrain
Among the unexpected problems are, in particular, the seasonal fluctuations on Mars. Summer has just ended there, autumn is coming, and with it the time of dust storms and low pressure areas. Further weather-related flight cancellations are looming.
Summer, on the other hand, caused other problems: the already thin Mars atmosphere became even thinner due to the higher temperatures. The air pressure dropped from about 1.2 to 1.5 percent of earthly value to only one percent. "The difference may seem low, but it has a significant impact on the engine's engineering ability," writes chief pilot Grip. With a density of 1.2 percent, for which the helicopter was originally interpreted, Ingenuity therefore has at least 30 percent shoe reserves. They are important for the start and in the event that obstacles must be scanned unplanned. In Mars summer, however, these reserves fell to eight percent. Too little to fly safely.
The team therefore increased the speed of the rotors, originally 2400 revolutions per minute to 2700 revolutions. There was nothing more, since the rotor tips would have reached a pace near the speed of sound, which would create additional resistance.
However, higher speeds meant a greater load on the motors and the other moving components. The temperatures on board increased, the team had to reduce the maximum flight time from 150 seconds to 130 seconds. Simply flying off earlier in the morning, when it's even colder on Mars, was not an option. Ingenuity needs the first rays of the sun to warm up from the cold of the night and charge its batteries with the help of solar cells. As a result, every flight became risky, it was necessary to weigh between speeds and temperatures, take-off time and flight duration.
You would be Believe what i just saw.
Yet another problem plagues the JPL team: Ingenuity is not made for hovering over hilly terrain. The navigation of the mini helicopter is responsible for this. Since there is no GPS on Mars, Ingenuity relies on built-in sensors. They measure acceleration and rotation and use them to calculate the position of the helicopter. However, the whole thing is inaccurate. Therefore, there is also a downward-facing navigation camera on board. It takes a picture 30 times per second, compares the individual photos and determines the old and the new position from them.
However, the software starts from a flat site during its calculations - after all, Ingenuity should not fly anywhere else. If the helicopter is traveling in mountainous terrain, the tips of the hills seem to move faster than the rest of the landscape due to their lower distance to the camera. That confuses the algorithms. The navigation becomes imprecise, the direction of flight varies, precise landings are no longer possible. The longer the flight takes, the greater the potential landing zone.
This becomes a challenge, especially in the uneven delta of the Jezero crater. The problem cannot be solved simply: the flat navigation is firmly programmed into Ingenuity's on -board computers. The team around chief pilot Grip therefore simulates upcoming flights over hills, cliffs and dunes of earthly computers. It looks at what the confused bristle calculator will probably make of it and plan the flight routes accordingly.
Weighing the risks and benefits
So far it has gone well, even if there were some moments of fright. At flight 6, for example, the software swallowed one of the pictures of the navigation camera. The time stamps of all subsequent recordings no longer fit, the algorithm got messed up. Wild flight maneuvers and inclinations up to 20 degrees were the result. Ingenuity could still land safely, with the help of its acceleration sensors. At flight 17 shortly before landing, contact with the Rover Perseverance, which serves as a relay station for communication with the earth. Apparently, Ingenuity had disappeared unplanned behind a hill, which disturbed the direct radio connection. The landing still worked without any problems.
From the mantra "high risk, high opportunities", specified by chief engineer Balaram before the start, has long since become careful weighing up between benefits and risk: Ingenuity can break at any time. At the same time, it should fly higher and faster than ever before. It has to defy the autumn weather, but it has also become an important factor for the scientific work of the Rovers Perseverance. And he should show what is possible with drones in the future. The flying on Mars, it doesn't make it easier.
