Why have you been flying for so long? How dangerous is the process of falling a fire? What to do after landing?
Designer reveals Tianwen No.1
The picture shows the rendering of the Tianwen-1 landing patrol vehicle landing on Mars.
(Photo courtesy of the Fifth Academy of China Aerospace Science and Technology Corporation)
On May 15, China's first Mars exploration mission, Tianwen-1, successfully landed in the pre-selected landing zone in the southern Utopia Plain of Mars, leaving a Chinese mark on Mars for the first time.
As early as February 10, the Tianwen No. 1 probe successfully "braked" and was captured by Mars, but it was "delayed" in the following three months.
Why have you been flying for so long?
Landing on Mars, why do experts call this "the core and most difficult part of the mission"?
After landing, how will Tianwen-1 explore Mars?
With these questions, the reporter interviewed experts such as Wang Chuang, the chief designer of the Mars Probe, the General Design Department of the Fifth Academy of China Aerospace Science and Technology Corporation, and Zheng Yongchun, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.
Why did it take so long to arrive?
Take no time to spare, make perfect preparations for falling into the fire
After being captured by Mars, the Tianwen-1 probe not only carried out multi-dimensional exploration of Mars in more than three months, but also made full preparations for landing on Mars.
The Tianwen-1 probe is a "three-piece", including the orbiter, the entry module and the "Zhurong" Mars rover. The latter two together form the landing patrol device.
According to Du Yang, deputy chief designer of the 509th Orbiter of the Eighth Academy of Aerospace Science and Technology Group, in order to "pre-stop" the landing patrol, the orbiter will conduct multi-dimensional detection of the pre-selected landing area. In an unobstructed place, on the other hand, wait for the "chance" to observe the sky and get the weather conditions in the vicinity of the landing area.
Several large dust storms are formed on the surface of Mars every year. Historically, there have been probes that caught up with the dust storms when they arrived on Mars, and ultimately failed to start their work smoothly.
Dust storms may change the dynamic parameters of the landing patrol descent process, affecting the safety of the landing process, and dust particles may adhere to the surface of the detector, or even penetrate into the interior, causing equipment failure.
As the Mars rover uses solar panels for power supply, a large amount of sand and dust will cover the surface of the solar cells, reducing the power generation efficiency and even the loss of power generation capacity.
For the rover, the loss of energy supply is undoubtedly fatal.
Therefore, the orbiter detects the pre-selected landing area in advance and learns about sandstorms and other trends, so as to avoid inclement weather.
Tianwen-1’s landing site is the southern part of the Martian Utopia Plain. By analyzing the previous meteorological data and remote sensing data from the Mars rover in this area, it is a safer choice to set off a fire in mid-to-late May.
In addition to preparatory work, Tianwen No.1 has also completed a series of scientific explorations.
On February 24, after Tianwen 1 entered the Martian orbit, the seven scientific instruments on the orbiter were all turned on and started to work, and several orbit adjustments were made during this period.
This means that it has obtained scientific information on Mars at different orbital heights, and the combination of detection data at different orbital heights can help us understand the space environment of Mars more comprehensively, such as Mars’ magnetic field, ionosphere, solar wind and The interaction between the upper atmosphere of Mars, etc.
How dangerous is the process of falling a fire?
Completed independently by Tianwen No. 1 and experienced the "unknown 9 minutes"
The Tianwen No. 1 fire was divided into three steps: entering, decelerating and soft landing, referred to as "EDL".
At about 1 am on May 15th, the Tianwen-1 probe descended from its parked orbit and maneuvered to Mars into orbit; at 4 o'clock, the landing patrol was separated from the orbiter, and after about 3 hours of flight, it entered the Martian atmosphere After about 9 minutes of deceleration, hovering, obstacle avoidance and buffering, it successfully soft-landed in the pre-selected landing zone.
"This is the most risky step in the entire mission. The landing process cannot be controlled by the ground in real time. It can only be done autonomously by Tianwen-1." Wang Chuang told reporters that after entering the Martian atmosphere, Tianwen-1 first used the Martian atmosphere to perform aerodynamics. Slowing down, overcoming the challenges of high temperature caused by ultra-high-speed friction, attitude deviation caused by aerodynamics, and reducing the descent speed of about 20,000 km/h by about 90%; then, Tianwen No. 1 opened the parachute to decelerate the parachute. , When the speed drops to 100 m/s, the engine is decelerated by the reverse thrust, and the atmospheric deceleration phase enters the power deceleration phase.
At 100 meters from the surface of Mars, Tianwen-1 entered the hovering phase. After precise obstacle avoidance and slow descent, the landing patrol steadily landed on the surface of Mars under the protection of buffer mechanisms and airbags.
The most difficult thing is the parachute.
"The supersonic parachute is the most difficult link in 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 problems such as difficulty in opening the parachute and unstable parachute opening. "Wang Chuang said that due to the thin atmosphere of Mars, the developers designed the aerodynamic shape and heat-proof structure of the detector with high-efficiency deceleration performance, and adopted lighter heat-proof materials.
Although my country has had lunar landing experience before, the soft landing mission of Tianwen-1 to Mars is even more difficult.
"The communication between the ground station and the probe is achieved through radio waves, and the propagation speed is about 300,000 kilometers per second. The average distance from the moon to the earth is 380,000 kilometers, so there is almost no delay when the lunar probe communicates with the earth. However, the distance between the Earth and Mars varies. The closest is about 55 million kilometers, and the farthest can reach 400 million kilometers." Zheng Yongchun told reporters that due to the long distance, the communication between the ground and the Mars rover faces the longest approach. With a delay of 20 minutes, researchers cannot control the detector at any time, which is unprecedented.
"my country has implemented a Mars exploration mission for the first time. There is no first-hand data on the Mars environment, especially the atmosphere, which is equivalent to groping step by step in a completely unknown environment. The difficulty can be imagined." Said Chen Baichao, the overall chief designer.
The day before the Tianwen-1 landing patrol rover fell on fire, the British "Nature" magazine published a review article, claiming that the landing of the "Zhu Rong" rover was the biggest test of China's deep space exploration capabilities.
The report also quoted Robert Orosse, a planetary scientist at the Institute of Radio Astronomy in Bologna, Italy: "This mission is a huge leap for China, because they completed the mission that NASA took decades to complete in one go. ."
What to do after falling into the fire?
Global imaging of the landing site, self-inspection, departure from the landing platform and patrol detection will be carried out in sequence
Reaching Mars is not the goal, it is the goal to obtain as much effective scientific exploration data as possible.
Next, the rover will carry out global imaging of the landing site, self-inspection, departure from the landing platform, and patrol detection.
Tianwen No. 1 carries a total of 13 scientific instruments, capable of taking pictures, measuring substances, measuring the environment, measuring geology, and watching the weather, and it is equipped with "all kinds of martial arts."
The rover and the orbiter jointly undertake the scientific exploration mission, which mainly involves the research of the Martian space environment, surface topography and soil surface structure, etc., which will bring China first-hand data on Mars research.
The rover is 1.85 meters high and weighs about 240 kilograms. It is equipped with 4 "butterfly wings"-solar panels, and 6 wheels are independently driven. It is an out-and-out "Mars 6-wheel drive off-road vehicle".
There are 6 scientific instruments on board, including multi-spectral camera, subsurface detection radar, Mars surface composition detector, Mars surface magnetic field detector, Mars weather measuring instrument, navigation terrain camera, etc., in addition to obstacle avoidance cameras, surveillance cameras, etc. Many engineering instruments.
The orbiter's significance to the Mars rover is more than just "taking a ride."
After the landing patrol lands safely, the orbiter will stay in the communication relay orbit, forward various information and data back to the earth, and at the same time convey instructions from the earth to the rover.
The orbiter itself is also a super scientific research expert, carrying 7 scientific instruments, namely a medium-resolution camera, a high-resolution camera, a subsurface detection radar, a Martian mineral spectrometer, a Martian magnetometer, and a Martian ion and neutral particle. The analyzer and the Mars energy particle analyzer can conduct holistic, global, and comprehensive research on Mars at multiple orbital altitudes.
The detection process is carefully arranged, and the detection data is safely and effectively transmitted back to the earth without fail.
Considering that Mars is far away, my country has built three new measurement and control stations in addition to the measurement and control station built for the lunar exploration project.
"In this way, 4 networked antennas can be arrayed, and the measurement and control capabilities are stronger. It can realize the measurement and control communication when Mars is 400 million kilometers away from the earth." said Liu Tongjie, deputy director of the China National Space Administration's Lunar Exploration and Space Engineering Center. This is in measurement and control technology. This is a big breakthrough.
The design life of the Mars rover is 3 Mars months. Since a day on Mars is slightly longer than that of the Earth (Mars rotation period is about 24 hours and 37 minutes), it is equivalent to about 92 Earth days.
According to the plan, after about 90 Mars days, the rover will end its patrol and exploration work, and the orbiter will also adjust its orbit to enter an orbit of 265 kilometers near the fire point and 12,000 kilometers away from the fire point, and carry out at least one Martian year (about 2 Earth years) short-range remote sensing detection.
Tianwen-1 has achieved my country’s first extraterrestrial planet landing, pushing my country’s interstellar exploration to a new level, which is undoubtedly a feat in the history of human spaceflight.
NASA Assistant Administrator Thomas Zulbuqin posted on social media: "Zhurong landed on Mars, congratulations to the China National Space Administration Tianwen-1 team! Together with the global scientific community, I look forward to this Mars mission to understand humans This red planet makes an important contribution."
The vast universe carries the yearning of Chinese people for thousands of years, and it also entrusts the common dream of all mankind.
After all the calls came out, my country's first Mars rover strode towards a new journey of interstellar exploration.
(Our reporter Chai Yaxin)