On May 15, my country's "Zhu Rong" rover landed on the southern end of the Utopia Plain of Mars.
The latest scientific exploration found that there is a large amount of groundwater ice under the shallow bottom of the Martian Utopia Plain 1 to 10 meters above the ground, and the water storage is equivalent to the largest freshwater lake on the earth-Lake Superior.
Does the presence of water on Mars mean that Mars has existed or life has existed?
These questions need to be further answered by our Mars rover in this magical place of Utopia Plain.
Choosing to land on the Utopia plain may reveal the mystery of life on Mars.
But the landing on Mars is extremely dangerous. What difficulties must the probe overcome?
What are the different ways to land on Mars?
The success rate is only about 50%
After choosing a landing site, the biggest challenge is how to land on Mars.
Currently, the success rate of the world's Mars rover landing is only about 50%.
This is because Mars is too far away from the earth, and the ground telemetry and remote control signals are very weak.
In addition, since the communication delay between the Earth and Mars is more than 10 minutes, everything must be carried out independently by the probe during the whole process of Mars landing.
In addition, when the Mars rover moves to the back of Mars, the Earth cannot accurately determine its orbital parameters, which will bring difficulties to the selection of the reentry height.
Before landing, it is necessary to inject data into the Mars rover in advance so that it can execute hundreds of procedures completely autonomously during the landing process, and no one procedure can be mistaken.
After entering the Martian atmosphere, the heat protection measures for the Mars rover, and whether the parachutes, airbags, and buffer rockets can work in accordance with the procedures are all crucial. They must be very precise, not bad for one second.
Therefore, every link of the Mars rover’s landing process must not be missed.
An American scientist once described the mood when the Mars rover landed, as if a husband was waiting for his wife to give birth outside the delivery room.
When the American "Mars Polar Lander" was scheduled to land on Mars on December 3, 1999, when it was about to land on the surface of Mars, a software error caused its decelerating rocket engine to shut down prematurely and eventually crashed.
On October 20, 2016, the entry, landing and landing demonstrator of the “Sharparelli” in the European “Mars Biology-2016” probe lost contact with the ground before landing due to a one-second calculation error , Separated the parachute from the heat shield in advance, causing the "Sharparelli" to crash and crash into a hard landing.
3 ways to land on Mars
After a lot of research and practical exploration, at present, there are three main ways for the probe to soft landing on Mars, each of which has its own advantages and disadvantages, but the basic principle is the same, which is to rely on the resistance of the Martian atmosphere to the entry capsule and parachute and detection The reverse thrust of the buffering engine on the aircraft reduces the speed of the high-speed Mars rover when it lands on the surface of Mars to zero.
The first landing method is the airbag bounce type.
This method is relatively simple and low in cost, but it can only meet the soft landing requirements of the light-weight Mars rover, and the landing accuracy is not high.
The American Mars Pathfinder, Valor and Opportunity rover all use this landing method, that is, parachute + air bag bounce landing.
Since the landing is a hard landing, the probe wrapped in the airbag will bounce up to a height of 10 stories when it landed, then bounce several times, gradually reduce the bounce height, and finally land on the surface of Mars.
The second landing method is the reverse thrust landing leg type.
This landing method is more complicated and costly. It can meet the requirements of a heavier probe for soft landing on Mars. The landing accuracy is high, similar to the return capsule of the "Shenzhou" spacecraft.
The US Pirates 1 and 2, Phoenix, Insight, and my country’s Zhu Rong rover all use this landing method, namely parachute + buffer engine reverse thrust + landing leg, where the landing leg is Play a certain cushioning effect when landing.
The third type of landing is the aerial crane type.
This landing method is the most complicated, the most costly, and the most advanced technology. It can meet the soft landing requirements of heavier detectors, and the landing position can also be more precise.
Both the American "Curiosity" and "Perseverance" Mars rover use this type of landing, that is, parachute + buffer engine reverse thrust + aerial crane landing.
(The author Pang Zhihao is the chief scientific communication expert of national space exploration technology)