How to complete the separation of the two devices? Experts of the Eighth Aerospace Academy decipher the risks behind the “perfect falling fire”
Its successful performance ensures that the landing patrol can complete the subsequent series of perfect falling, descent, hovering, obstacle avoidance, and landing actions , Leaving a Chinese mark on the surface of Mars for the first time.
How was the “separation of the two instruments” completed in the orbit of Mars this time? Where is the risk? What thrilling process did you go through during the landing? Experts from the Shanghai Eighth Academy of Aerospace revealed the details.
Before the separation, the “Tianwen-1” Mars rover was orbiting on a moored orbit with a period of two Martian days. About 6 hours before reaching the near-fire point, the Eighth Academy grasped the orbiter developed by the General Assembly. The four 120N engines ignited for about two minutes to perform a descending maneuver, enter the Martian atmosphere and enter the orbit, and then turn to the separation attitude of the two devices (orbiter, landing patrol device), and perform the separation of the two devices.
According to experts from the Eighth Institute, the separation of the two devices has gone through the three-step process of “dropping, separating, and ascending orbit”, which is startling every step.
First of all, the “Tianwen No. 1” will implement a down-orbit maneuver, and the engine on the orbiter will ignite to reduce the height of the detector near the fire point. Then, “Tianwen-1” separated the orbiter and the landing patrol before about 125 kilometers from the surface of Mars. After the two vehicles reach a safe distance, the orbiter is ignited to lift the orbit to the relay orbit, and while the orbiter is ascending, it will shoot and monitor the descending process of the landing patrol in real time. Then, the landing patrol adjusts its attitude, with the heat-resistant outsole facing forward, and glide along the orbit into the Martian atmosphere, aiming at a narrow entry corridor into the Martian atmosphere. The angle formed by the landing patrol and the Martian atmosphere is very critical. If the angle is too large, the friction temperature with the atmosphere will rise too sharply, and the angle is too small to achieve the goal of entering the Martian atmosphere.
Experts pointed out that if the de-orbit deviation is too large, it will affect the entry angle, latitude and longitude of the landing rover when it enters the Martian atmosphere, and ultimately affect the landing process after the landing rover enters the Martian atmosphere. In this case , The ground can terminate the separation process; if there is a separation problem, the detector can automatically determine to cancel the separation, continue to fly with the landing patrol, and wait for the subsequent landing opportunity; separation is successful, but the orbiter’s height near the fire point is not enough, and it will enter the Martian atmosphere The risk of crash, these are the risk points of the separation and landing of the two vehicles.
After the landing patrol and the orbiter are separated, they continue to enter the orbit along the Martian atmosphere. After separation, they enter the Martian atmosphere for more than 3 hours, relying on aerodynamic shape to decelerate, parachute deceleration, engine deceleration, hovering avoidance Barrier, and finally landed safely on the surface of Mars. The orbiter will perform an ascending maneuver after separation for half an hour and return to the parking orbit.
When entering the Martian atmosphere, the landing patrol The speed can reach 4.8 kilometers per second, which is equivalent to 6 times the speed of the ejection chamber
When the landing patrol is about 10 kilometers away from Mars, the supersonic parachute is opened. According to experts, the landing patrol entering the aerodynamic deceleration stage is the most important deceleration stage. When entering the Martian atmosphere, the landing patrol can reach a speed of 4.8 kilometers per second, which is equivalent to 6 times the speed of the ejection chamber. After the landing patrol enters the Martian atmosphere, it needs to conduct the lift system guidance and deploy the trim wing to make better use of the resistance of the Martian atmosphere, so that the land patrol will slow down by the constant friction between the heat-proof outsole of the land patrol and the Martian atmosphere. After 5 minutes of deceleration, the speed of the landing patrol dropped to 460 meters per second, a speed reduction of nearly 90%.
When the speed drops to 100m/s, the parachute has basically completed its mission, and after that, the landing patrol will be The back cover was thrown away, revealing that the landing platform and the Mars rover opened the supersonic parachute when the landing patrol was about 10 kilometers away from Mars. With the help of a parachute, the speed of the landing patrol dropped below 100 meters per second. In this more than one minute, the speed and direction of the wind in the Martian atmosphere have a great impact on the accuracy of the “fire” fall, and sometimes even affect the safety of the “fire” fall.
When the height of Mars is 100 meters, Hovering with the help of the landing engine. When the speed drops to 100 m/s, the parachute has basically completed its mission. After that, the landing patrol throws off the outsole and back cover, exposing the landing platform and the rover. The 7500N variable-thrust landing engine on the platform began to ignite to further reduce the descent speed of the landing patrol. It took 80 seconds to reduce the speed to 3.6 m/s while maintaining a stable attitude. The ground radar was randomly turned on and deployed. The four landing legs of the landing buffer mechanism.
When the height of Mars is 100 meters, the landing engine is used to hover, and the fire surface is imaged at the same time, and then a relatively flat area is selected for landing.
At the last moment of “fire”, The energy-absorbing materials in the four landing legs are used to cushion the impact force during landing and ensure that the landing patrol patrols smoothly on the surface of Mars. At the final moment of “fire”, the energy-absorbing materials in the four landing legs are used to cushion the impact force during landing to ensure that the landing patrol lands smoothly on the surface of Mars.
During the entire “fire” process, due to the very long distance of the ground fire, the one-way delay of ground fire communication exceeded 17 minutes. During the “fire” process, the landing patrol and the ground “command” are in a “disconnected” state. It needs to autonomously complete the series of extremely complex actions of entry, descent and landing in accordance with the pre-planned plan, and there should be no slightest. Mistakes, because this process cannot rely on the ground for real-time control and intervention.
The butterfly-shaped rover——”Zhu Rong It took just over 9 minutes for the ship to fall on the “fire”, which was really thrilling. Afterwards, as the rover spread its dark blue wings and slowly drove off the landing platform, the butterfly-shaped rover—the Zhurong With the expectations and trust of the Chinese people, scientific exploration will be carried out on the red planet of Mars.