People’s Daily Online, Beijing, May 15 (Zhao Zhuqing) On May 15, Tianwen-1 successfully landed in the pre-selected landing area in the southern part of the Mars Utopia Plain. China’s first Mars exploration mission to Mars was a complete success. The Tianwen-1 mission achieved my country’s first extraterrestrial planet landing, which is another significant milestone in China’s aerospace industry development.
The landing process “step by step startling” by “autonomy” throughout the journey
According to Rao Wei, product assurance manager of the “Tianwen No. 1” probe of the Fifth Academy of Aerospace Science and Technology Group, the “Tianwen No. 1” probe has been successfully launched on July 23, 2020. Orbital flight for about 295 days; after successfully orbiting Mars on February 10, 2021, key flight control tasks such as pre-detection of the landing zone, orbit maintenance, and self-check have been completed. During this period, the energy is balanced, the state is stable, and the sub-systems work normally.
At around 2 am on May 15th, “Tianwen-1” entered the landing window in the Mars mooring orbit. Then the probe descended, the orbiter was separated from the landing patrol starter, and then the orbiter ascended and returned to the mooring orbit. , The landing patrol runs to the entry point 125 kilometers from the surface of Mars, begins to enter the Martian atmosphere, and finally softly land on the surface of Mars.
The “Tianwen-1” Mars probe landed on the surface of Mars through a soft landing from the outer edge of the Martian atmosphere. The entire landing process was shocking, and the technology was very complicated.
The landing process is roughly divided into the following steps. First, the probe aimed at a narrow entry corridor into the Martian atmosphere, then aerodynamically slowed down, and then the Mars special parachute was deployed; after the parachute completed its mission, the probe dropped the outsole and back cover, exposing the landing platform and the rover; the large thrust was launched. The maneuver began to work, and the probe observed the ground to find the safest specific landing site; the last four landing legs landed steadily on the surface of Mars.
The whole process is short and complicated. There is no opportunity for intervention on the ground. The timing of each action is determined independently by “Tianwen No. 1”.
Braking at high speed? “Supersonic Parachute” Shows Its Skills
To land safely and steadily on the surface of Mars, the first problem is to slow down the high-speed Mercedes-Benz “Tianwen No. 1”.
However, compared with lunar exploration missions, Mars exploration has to face a long distance of 400 million kilometers. The Martian environment and the earth environment are quite different and uncertain. The atmosphere thin, and we do not have the actual measurement method of the Martian atmosphere. There is no flight-verified data; in addition, the atmosphere of Mars is volatile due to the influence of seasons, night and day, Martian storms, etc.; the surface of Mars is complicated with rocks, slopes, ravines, and other obstacles; Martian dust storms are more serious than those of the earth. These factors bring great difficulties to landing on Mars, and the risk of a safe landing is very high.
“The supersonic parachute is the most difficult part of the deceleration technology. When using the parachute, Tianwen No.1 must be opened at supersonic speed, low density, and low dynamic pressure. This process has difficulty in opening the parachute and unstable parachute opening. Question.” said Wang Chuang, the overall chief designer of the “Tianwen No. 1” probe of the Fifth Academy of Aerospace Science and Technology Group.
He explained, “Because the Martian atmosphere is very thin, the aerodynamic shape of the probe is required to have efficient deceleration performance when entering Mars, and at the same time, lighter heat-proof materials are required.”
Experience “9 minutes of terror” and choose “life and death.”
In addition to the deceleration design, the choice of the Mars entry plan is also critical, and it can even be said to decide “life and death.”
Because from the moment it first stepped onto the entry point, “Tianwen No.1” ushered in the most dangerous and thrilling “9 minutes of terror” in this fire-finding journey.
It is reported that the current success rate of human Mars exploration missions is only about 50%, and most of the failures are at the “entry/descent/landing” stage. “The greatest difficulty in Mars exploration is landing. This process requires a combination of aerodynamic shape, parachute, engine, multi-stage deceleration, and landing recoil to implement a soft landing. Each link must be accurate, and it can be a second. Caused the failure of the entire mission.” said Sun Zezhou, chief designer of the “Tianwen No. 1” probe of the Fifth Academy of Aerospace Science and Technology Group.
“For this reason, before the landing, the’Tianwen 1’carried out a detailed investigation and pre-exploration of the landing area on the Mars mooring orbit, obtained a large amount of data on the topography of the landing area, and carried out the probability of the occurrence of Martian dust storms. At the same time, the Mars rover inherited the mature hovering and obstacle avoidance technologies of Chang’E 3, 4, and 5 to ensure a safe landing. Based on these measures, we have also adopted the ballistic-lift entry program of the trim wing is designed to reduce the risk caused by the uncertainty of Martian atmospheric parameters and improve the adaptability.” Sun Zezhou said.
After the “Tianwen No. 1” successfully landed on Mars, my country’s first Mars rover is about to make its debut. Let us look forward to the wonderful performance of “Zhu Rong”!