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Magazine Helicopter Industry #102

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HELICOPTER INDUSTRY I

HELICOPTER INDUSTRY I NEW TECHNOLOGIES I T he Mars Helicopter Scout, named Ingenuity, is scheduled to take off from Earth on July 17 aboard the Mars 2020 probe. If the launch were to be postponed, the launch window would move to February 18, 2021. The one-way trip to Jezero Crater on Mars will take about six months. The objective of the Mars 2020 mission, with a total cost of about .5 billion, is to determine how Mars’ natural resources could be exploited to prepare for future human settlement. The main tool on board the probe will be a six-wheeled land vehicle, a rover, called Perseverance. The American rovers Sojourner, Spirit and Curiosity have already been seen on Mars. With Perseverance, NASA is changing scale, this time sending a spacecraft the size of a small car and a mass of one ton. Another novelty, therefore, is the presence of a helicopter that will arrive on Mars in the luggage of this rover. EXTRATERRESTRIAL AND EXTRAORDINARY CONSTRAINTS Ingenuity is a miniature helicopter, weighing only 1.8 kg, which will be called upon to play a scouting role. It will be used to find the best possible route to avoid dangers and to find points of interest for Perseverance, which could then fly over larger areas during its lifetime. The images provided by Ingenuity will have about ten times the resolution of those of the orbiting Martian probes. Ingenuity will also help determine whether or not the use of flying machines for extraterrestrial exploration is a good idea. The first studies for sending a helicopter to Mars began in 2015. In view of the positive results obtained, the formal decision was announced May 11th, 2018 to entrust the project to a mixed team of varying skillsets from the Aerovironment Company, Nasa’s Ames Research Center, and Langley Research Center. The first of the constraints that were faced by the designers of the aircraft were that of flight automation: there is no question of flying the aircraft in real-time at a distance of more than 50 million kilometers. Ingenuity, which deserves its name, will therefore have to fend for itself once the flight order has been given: take off, flight, orientation, image recording, and landing, in order to recharge the batteries and wait for the next flight. After all, many drones perform this on Earth, although the constraints of the Martian atmosphere are far more complex. HI I 52

A HELICOPTER AT LEVEL 900! Composed of carbon dioxide, Mars is incredibly tenuous, with an average pressure of 6 millibars, or 1/170th of the Earth’s atmosphere. At about ten meters from the Martian ground, which is the maximum flight altitude that Ingenuity will attain, as it is equal to the density of the Martian atmosphere and that found at... 30 kilometers from the Earth’s surface. Flying a helicopter in these conditions was not easy. In short, it was first necessary to model the dynamics of flight in these particular conditions, before designing a very light helicopter with a large rotor diameter to obtain the desired lift. However, the helicopter will be able to rely on the help provided by gravity, which is about three times weaker than on Earth, since Mars’ mass is onetenth that of Earth. In May 2016, a first 850g demonstrator was tested in an environmental chamber just under 8m in diameter, reproducing the near vacuum on Mars. The chosen formula used a contra-rotating rotor, eliminating the need for an anti-torque rotor while providing a very compact design. The results obtained were positive, and allowed the development of the final version of the device, by the use of the counter-rotating rotor formula with an electric motor. Ingenuity therefore weighs 1.8 kg and has two rigid counter-rotating rotors with a diameter of 1.21m rotating at a maximum speed of 2800 rpm. Its power comes from an electric motor coupled to a set of six lithium-ion microbatteries recharged by a solar panel. Its payload includes a high-resolution colour camera for navigation, another for studying the terrain, and a communication system enabling it to relay the images obtained to the Perseverance rover. Despite its minimalist weight, the Martian helicopter was designed to withstand the rocket’s high level of vibration and acceleration during launch. Its’ electronics, which include gyroscopes, motion and orientation sensors, accelerometers and an altimeter, are also protected against solar radiation and the intense cold that reigns on the planet (-63°C on average). In regards to its’ navigation, the aircraft uses an inertial navigation system that can be readjusted using a star sight that is pointed at the sun. HI I 53