May 7, 2021

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NASA lands Rover Perseverance on Mars

3 min read


In the mission Support Zone at the Lockheed Martin campus in Littleton, Colorado, masked people sat near computers, piloting three spacecraft orbiting Mars. These three – Mars Reconnaissance Orbiter, Maven, and Odyssey – were all tasked, in one way or another, with downloading data from another spacecraft: the Mars Perseverance rover, which was attempting to land on the Red Planet. . The information from these orbiters would help engineers know the status of Perseverance as it made its way through the atmosphere and determine if it survived. “Space is not a place to go,” read the words painted on one wall. “Space is a place to do.”

Scattered among the usual notes on unauthorized visitors and classified meetings, social distancing signs, masks and symptoms were placed around the building. “No masks with exhaust valves” warned one, aerospace. One was stationed behind the head of Lockheed’s David Scholz, who, about an hour before landing, was standing in a conference room 6 feet away from everything, sporting a blue surgical mask over his beige shirt in double pocket. The NASA video stream played in the background. Scholz had just described himself as a ‘confident nervous wreck’. This is because he is the principal engineer of a device called an “aeroshell,” which envelops the rover against the most extreme conditions of its journey down toward the surface of Mars.

Lockheed engineers had been working on this project for years, and today Scholz and his team could finally see it being implemented. But it’s all they could do: watch. Their system was automated and would do its job without them.

And so they saw a man-made object falling from the sky, aiming to land in a crater called Jezero. The landing, scheduled for 12:55 p.m. PT, would mark the end of the Perseverance rover’s journey into space and the start of its stay in this desolate destination: a depression that housed – billions of years ago – a lake and a river delta. It’s a place where life could, theoretically, have survived once.

Searching for places that appear to have been suitable for ancient life and proof of potential past habitation are among the objectives of the Mars 2020 mission. The rover will also collect and store geological samples for a future recovery mission and attempt to produce oxygen from the planet’s abundant carbon dioxide, in anticipation of the needs of future human astronauts.

But to get there, the spacecraft had to survive a heart-wrenching process that engineers call “entry, descent, and landing,” or EDL, which the Lockheed Martin team now nervously awaited. These final stages occur during what is known (to the point of cliché) the “seven minutes of terror” – the moment when the spacecraft must autonomously orchestrate its own E, D, and L without crashing into the sky. ground. During its mad rush, the rover would experience speeds of around 12,100 km / h and feel the equivalent of 12 times the Earth’s gravity during deceleration. Its protective sheath would heat up to about 2370 degrees Fahrenheit. Many things could go wrong: the machine could get too hot; his pieces might not come apart when they were meant to; even if they separated properly, they could “recontact” (read: hit each other); Perseverance might end up in the wrong place; it could end up creating its own impact crater. Choose your own nightmare.

“The bottom line about EDL is that everything has to be okay,” Allen Chen of NASA’s Jet Propulsion Laboratory, who heads the EDL team, told me a few weeks before landing. “There is no partial credit.”

This 100% A + performance is what excites the nerves even of the confident engineers at Lockheed Martin who worked on the aeroshell. The aeroshell consists of two parts: the heat shield, which looks like a steampunk space frisbee, and the backshell, a classic space capsule. The heat shield faces the planet as the spacecraft enters the atmosphere, taking on the commercial side of pressure and heat. It is made from tiles of a material called PICA, or carbon ablator impregnated with phenol. “When it’s hot, it starts to decompose, and this decomposition absorbs a lot of energy and also creates gas which forms a boundary layer which protects the heat shield from the environment,” Scholz explained before the landing. The shielded shield, in turn, protects its cargo. The device burns the atmosphere at an inclination, which Scholz calls “an angle of attack,” and steers itself with thrusters.



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