Approximately seven months after liftoff, NASA’s last Mars-bound vehicle, Perseverance, will still have to survive “seven minutes of terror” this Thursday, as the ultra-dangerous maneuver that precedes its landing has been called. on the red planet.
The chosen location, Jezero Crater, is the most dangerous landing site ever attempted. In seven minutes, the vehicle must go from a speed of 20,000 km / h to 0.
Perseverance is scheduled to land at 8:55 PM on Thursday.
– 130 km: entrance to the atmosphere –
Ten minutes before entering the atmosphere of Mars, it will separate from the cruise stage, which supplied it with fuel during the trip.
The rover will then be connected exclusively to the descent stage, both protected by two shields, the lower thermal one.
About 130 km from the surface of Mars, the mission will enter the atmosphere at a speed of 20,000 km / h. Friction will raise the temperature to 1,300 ° C. The lower shield will protect the rover from this infernal heat.
– 11 km: parachute opening-
But the atmosphere is not enough to slow down the spacecraft, which is still going 1,500 km / h.
At an altitude of about 11 km, at an opportune moment calculated based on the distance remaining to the landing site, a 21-meter diameter parachute will be deployed, located on the upper shield.
This will slow the device down to about 300 km / h.
– 9 km: heat shield separation –
20 seconds after opening the parachute, the heat shield will be released: the vehicle it was protecting is exposed for the first time to the atmosphere of Mars.
At that point a totally new technology will come into play, called “Terrain Relative Navigation” (TRN): the images recorded live by the rover’s cameras are compared with maps recorded in its system and the dangerous areas to avoid are predefined. Taking this data into account, it will be decided where the rover lands.
– 2 km: retro-propelled phase –
At an altitude of about 2 km, the NASA vehicle will detach from the rear shield and parachute.
The rover will separate from the descent stage, but first, thanks to its eight engines pointed towards the surface of Mars, it will have slowed the descent. After performing a maneuver away from the parachute, the rover will end up descending vertically to its landing point.
– 20 m: rover separation –
At about 20 meters above the ground, the speed will be 2.7 km / h, slower than a person’s walking. Then, the rover will descend suspended by cables thanks to a system of pulleys during the last 15 seconds (stage called “skycrane”).
The vehicle will then unfold its wheels. When it hits the ground, the cables will be cut and the descent stage will move away to drop as far as possible. Due to the delay in transmission between Earth and Mars, when NASA confirms the landing, it will actually have taken place several minutes earlier.
la / dga / ll