When the Rover “Perseverance” (“endurance”) starts on Thursday as planned, to Mars, with a bonus attraction. Under its belly is a small helicopter, “Ingenuity” (“ingenuity” is) called. It is the first flight to lift off on an alien planet. For seven years, its development has taken. It required a lot of engineering, even in Places where one would not necessarily expect.
“When you tackle a Problem from the beginning, one sees only the obvious challenges,” says Håvard Grip, an engineer at the Jet Propulsion Laboratory of Nasa. For example, would be to leave the helicopter in the first place to withdraw to. Its rotor diameter can not exceed 1.2 meters, so it fits under the Rover. Also, the Rotor may not rotate too fast. Otherwise, would. his tips is the speed of sound is exceeded, which precipitates in the cold and the different atmosphere of Mars is somewhat lower than in the earth’s atmosphere Combined with the gravitational pull on Mars, thanks to which a subject has only a third of its earthly weight, and a hundred times lower density of the Martian air, the result is that it takes about twice as much power as on earth, the same mass increase. “You can calculate on a napkin,” says the engineer.
rotors for the thin Mars air
designing With these parameters in mind Håvard Grip, and his colleagues in 2013, began their helicopter. They decided to use two superimposed rotors, running at 2400 Revolutions per Minute against each other. Above them, a solar cell is located, including a flight computer, Sensors, two cameras, radio system and especially the batteries in a small box space. Everything together weighs just 1.8 kilograms. “But first, when you start really working on the Details, to recognize things that were previously obvious,” says Grip.
What are the means, recognized the engineers 2014. They had just built a first prototype and had him in a chamber to start, from which they had pumped out the air, to simulate the thin Martian atmosphere. He picked up the phone. The basic calculations were correct. “But he was uncontrollable,” recalls Grip.
This early Test have shown that it is not enough to take the earth’s proven Design and simply need to be adjusted – here, then, let the Rotor run slightly faster. “Things behave on Mars just fundamentally different,” says Grip. It turned out that the rotor blades were the cause. They fluttered up and down. The leaves do from helicopters on the earth also. But here, the air dampens their movement. In the thin Martian atmosphere, this damping is eliminated. The leaves are therefore advised in such a way to Flutter, that you can make the control of the Mars helicopter sluggish, which in turn complicates the control. “You can think of it as if you wanted to with two heavy shopping bags on the Handlebars of bicycles,” says Grip. The engineers went back to the drawing Board and designed stiffer rotor blades. The Problem was solved.
Because they are made of carbon fiber with a foam core, weighs each of the two 1.2-metre rotors not even 60 grams, less than a hen’s egg. It is not surprising that they raise, tells Grip. “You look so robust, but if you hold it, you realize that they weigh practically nothing.”
