How difficult is it for Tianwen-1 to accomplish three major tasks at one time?

At 12:41 on July 23, my country's first Mars probe, Tianwen-1, was successfully launched by a Long March 5 carrier rocket from the Wenchang Space Launch Center in Hainan. After liftoff, it will take about 7 months to reach Mars and conduct orbiting and patrol exploration.

China's first Mars exploration mission will achieve the three major tasks of "orbiting", "landing" and "patrol exploration" at one time. This is unprecedented in the history of space exploration and the difficulty can be imagined. So, what difficulties and risks does Tianwen-1 face on its dream journey to Mars? Let's take a closer look at the bumps and bruises on the road to Mars exploration.

The first challenge: the task starts from a high point and the technical span is large

As of the end of June this year, 44 Mars exploration missions have been conducted by countries around the world, but the probability of success is only about 50%. This shows that the inherent risks of Mars exploration missions are very high.

China's Mars exploration mission aims to orbit, land and patrol at the same time. "No country in the world has ever achieved this at the same time, and the mission is very difficult," said Sun Zezhou, chief designer of the Mars probe of the Fifth Academy of China Aerospace Science and Technology Corporation.

According to deep space exploration experts from the Fifth Academy of China Aerospace Science and Technology Corporation, the launch scale of my country's Mars exploration mission is very large, and the effective landing mass is second only to that of the United States' Curiosity, and the exploration around Mars is at the same international level. The probe is under development, and the correlations are extremely complex. The first entry into an extraterrestrial atmospheric body faces many technical challenges, such as orbit, aerodynamics, heat protection, large sail parachute, etc., and new technological breakthroughs and leaps must be achieved in the design of nearly ten aspects.

The second challenge: new design constraints and high uncertainty

Faced with a distant and unknown planet, Tianwen-1 will inevitably face the test of a new environment on its journey to Mars.

Existing data show that there is very little basic data on Mars' thin atmosphere, wind fields, dust storms, and surface topography, and there is great uncertainty. The new interplanetary space environment makes the already extremely risky exploration mission even more difficult.

The new constraints on Mars, such as the long distance of up to 400 million kilometers and the long time delay, place very high demands on the autonomous capability of the probe, and bring huge challenges and uncertainties to a series of designs including successful entry and landing on Mars, measurement and control communications, rover energy, thermal control, and movement on the surface of Mars, as well as the technology and environmental adaptability of electronic products.

The third challenge: There are many key technologies and it is difficult to solve them

It is understood that in this Mars exploration mission, there are many critical, unique and irreversible links, such as near-fire capture braking, instrument separation, entry/descent/landing, rover release and separation and many other key technologies.

"The most core and difficult part of our Mars exploration mission this time is the aerodynamic shape and parachute deceleration process after the probe enters the Martian atmosphere. We only have one chance and we must ensure success." Chief Designer Sun Zezhou has a calm and clear understanding of the "Mars Exploration" mission.

To this end, the research and development team specially designed a new aerodynamic shape, a new parachute, etc. These key technologies are extremely difficult to tackle.

The fourth challenge: heavy verification tasks and high test difficulty

The reporter learned that the "Tianwen-1" Mars probe has many new technologies that have not been used or encountered by previous satellites or probes.

Therefore, in order to ensure the reliability of the probe, the research and development team carried out a large number of tests and verifications. In addition to the conventional force, heat and other tests, they also had to complete aerodynamic shape, thermal ablation protection, hovering and obstacle avoidance, slow descent and landing, and special tests of the rover's indoor and outdoor systems, subsystems and single-machine level. The verification task was extremely heavy.

According to deep space exploration experts from the Fifth Academy of China Aerospace Science and Technology Corporation, these special tests are not only difficult to determine the test methods and plans, but also very difficult to simulate the Martian environment, implement the tests, and determine the test results. In addition, the adequacy, effectiveness, and coverage of the test verification and the test simulation verification are also extremely difficult.

However, the multiple difficulties did not scare away the Mars exploration development team. The designers raced against time to carry out a large number of test verifications and various mission preparations, paving the way for the Tianwen-1's Mars exploration journey.

The fifth challenge: tight development cycle and high progress risk

my country started its Mars exploration relatively late, so the development team has been running since the mission was launched. The Mars exploration mission was officially approved in early 2016; in July 2016, the development of the Mars probe entered the prototype stage; at the end of 2016, the probe completed all key technical research and detailed design... Since then, the development team has been working non-stop, completing the product development and verification, standby for delivery, and launch as planned in just over four years.

During this period, the work on the plan and the prototype, as well as the prototype and the final prototype, was fully cross-cut and parallel. To this end, the main tasks did not stop for a moment and were connected in advance. Progress and technical risks were highly coupled, and the entire line and the entire process required extra-long work, which put extremely high demands on risk control.

In addition, the Mars exploration mission is a major aerospace engineering task in my country. There are hundreds of participating research units, multiple lines running in parallel, multiple locations progressing in parallel, and multiple state processes running in parallel. The connection relationships are extremely complex, and coordination management and resource guarantee are extremely difficult, and it is extremely difficult to coordinate and control progress and quality risks.

"But it is precisely because of pressure that we can bring about technological progress," said Sun Zezhou. To this end, the research and development team demonstrated the spirit of national cooperation, carefully planned and implemented the mission with precision. All systems of the probe and all research and test personnel carried out their work in accordance with the requirements of "high quality, high efficiency and high benefits" to ensure the smooth progress of my country's first Mars exploration mission.

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