The success rate is less than half of humanity's "fire detection"
At present, the highly anticipated multi-national exploration of Mars has begun. Affected by weather conditions, the UAE Mars probe "Hope" delayed the launch mission until July 17. my country's Mars probe "Tianwen-1" has now arrived at the Wenchang space launch site. According to the scheduled plan, the launch will take place around July 23.
In fact, compared with the exploration of Mars, humans have made a lot of attempts on the exploration of the moon, and the results are remarkable. On January 2, 1959, the Soviet Union successfully launched "Lunar One", which opened the prelude to human exploration of the moon; in 1969, American astronaut Armstrong landed on the moon, and his small step took a huge leap forward for humanity; 1994 , The "Clementine" probe launched by the United States obtained the most detailed image of the lunar surface at that time, and found that there may be a lot of water ice in the South Pole of the moon; in 2011 and 2013, the United States launched the probe successively and accurately measured the gravity of the moon. Field, and analyzed the lunar thin atmosphere composition; in 2019, China's "Chang'e 4" for the first time realized the landing and patrol detection of the human detector on the back of the moon.
More than 50 years have passed since mankind first landed on the moon, and Mars is still missing. So what are the differences between Mars and Moon exploration?
The success rate of Mars exploration in history is only 43%
Mars is one of the planets in the solar system that is close to the earth and the natural environment is most similar to the earth. It has always been a hot spot for human exploration in deep space. Since 60 years ago, mankind has begun an adventure on Mars.
In October 1960, the Soviet Union launched two probes "Mars 1A" and "Mars 1B" to Mars, but unfortunately, after the launch of "Mars 1A", the third-stage rocket failed to ignite and only flew to the ground. It was scrapped at a height of 120 kilometers. The rocket engine of Mars 1B exploded directly. The debris falling in the air even contaminated the entire Baikonur launch site.
The exploration of Mars in the United States was also unfavorable. In 1964, the newly established NASA launched the Mariner 3 Mars probe. When it passed through the earth’s atmosphere, a protective shield of the probe failed. After the launch, all the detection instruments failed to turn on, and the first attempt in the United States also failed.
In October 1964, the US Mars 4 Mars probe returned to Earth the first image of the shortest distance in the history of mankind about the surface of Mars. At the same time, more than 5 million bits of scientific information were returned. It can be said This mission opened a new era of human space exploration.
However, in the following years, the Soviet Union launched several failures to launch a probe near Mars. The "Mars 2" probe developed has the ability to land in orbit, but it is encountering a large-scale dust storm on the surface of Mars during the landing process. , "Mars 2" crashed into the basin on Mars, this operation ended with a lander crash. 20 seconds after the Mars 3 probe landed on Mars, it lost contact with Earth. This is similar to NASA's experience in 1992. After the Mars Observer entered Mars orbit, it quickly lost contact.
In the 21st century, the exploration of Mars with an orbiter ushered in a golden age. The United States and the European Space Agency have successfully launched Mars probes. India has also joined the Mars Exploration Contest and launched the first "Mars Orbit Mission" probe. However, humans probe Mars
'S journey did not go smoothly. In 2011, Russia's "Phobos-Soil" interplanetary probe failed to send it into orbit to Mars due to a malfunction of the engine. "Fire" failed.
Data show that since 1960, the United States, the Soviet Union/Russia, Japan, Europe and India have carried out 44 Mars exploration projects, but only 23 successful and partially successful missions, the complete success rate is 43%, the remaining Projects have had detectors crashed, malfunctioning or missing. What is partial success? Pang Zhihao, the chief scientific communication expert of the national space exploration technology, explained in an interview with the Science and Technology Daily: "For example, the Soviet Union's "Mars 3" probe, after landing Mars, only sent back a signal of 20 seconds and lost contact. Some experts said that it was successful. Some people say they are unsuccessful."
Some people may ask, is the lunar exploration success rate higher? In this regard, Pang Zhihao said that the success rate of lunar exploration is not too high, the complete success rate is about 53%, especially in the early stage, the failure rate is relatively high. Overall, the success rate is slightly higher than Mars. Due to different statistical methods, such as the difference between understanding success and partial success, some statistical results appear to be about 60%, and some statistical results show 50%.
How difficult is it to detect Mars compared to the moon
In the industry, Mars is called the "detector cemetery", and its difficulty of detection can be imagined.
According to Pang Zhihao, Mars is about 400 million kilometers away from the earth, and recently about 56 million kilometers. The probe needs to fly such a long distance to reach Mars. There are very high demands.
In terms of launching, the rocket's carrying capacity, orbit accuracy and reliability are important prerequisites for Mars exploration. The speed at which the lunar probe enters the earth-moon transfer orbit is 10.9 km/s. The speed of the Mars rover to enter the ground fire transfer orbit must reach at least the second cosmic speed (11.2 km/s). Therefore, when launching a lunar probe and a Mars probe of the same quality, the latter must use a more powerful rocket to make the probe directly enter the ground fire transfer orbit, otherwise it will need to consume the probe's own fuel and accelerate the flight time , Which will affect the life of the detector.
"The biggest difficulty in Mars exploration is landing on Mars. The probe has to go through orbiting, descent and landing. This process is usually called terror for 7 minutes." Pang Zhihao said that it takes 7 minutes under Mars' thin atmosphere The speed of the detector is reduced from 20,000 km/h to zero, which requires the integration of a variety of deceleration methods including pneumatic deceleration, parachute deceleration and reverse thrust deceleration. Each link must be accurate and its difficulty is no less difficult A golf ball will fall into a hole in Tokyo."
Pang Zhihao explained that although the density of Mars' atmosphere is only 1% of that of the earth, compared with the lunar landing, when Mars landed, the probe had one more link to enter the atmosphere and open the parachute. Since the Martian atmosphere can play a certain deceleration role, the landing deceleration needs to be controlled very accurately. When entering, there must be no slight error in the attitude and angle of entry. However, human knowledge of the Martian atmosphere is still relatively limited, and coupled with the long delay of the measurement and control signal, the attitude, angle and speed adjustment before entering the Martian atmosphere must be performed independently by the probe. When the probe cuts into Mars orbit, if the cut-in point is too far from Mars, it cannot be captured by Mars' gravitation and pass through Mars; if the cut-in point is too close to Mars, it may crash into the Martian atmosphere. In addition, after entering the Martian atmosphere, the probe should also open the umbrella on time to slow down, cut the umbrella on time, throw the bottom on time, hover over obstacles on time, shut down on time, etc., and a slight flash will cause failure.
Due to the long distance, it takes 260-320 days for the Mars rover to reach Mars orbit, and communication is also a big problem. Pang Zhihao said that the radio signal sent from the earth to Mars has a one-way delay of about 20 minutes. At the same time, the longer the distance, the weaker the signal, coupled with noise interference in the universe, this is a very big challenge to the signal transmission technology. In order to cope with the problem of signal attenuation, the detector needs to be equipped with high-gain, high-reliability communication equipment, and the ground must also have a large-diameter deep space measurement and control antenna to avoid the detector being "lost" due to communication failures.
If everything goes well in the front, the probe finally settles on Mars, but it is not easy to work smoothly. Pang Zhihao said that to work on the surface of the moon, a lunar rover needs to spend a long moon night. A long moon night is equivalent to 14 days on earth, and the temperature can reach minus 180 degrees Celsius. The temperature difference on Mars is not that big, and it is also 24 hours a day. However, the dust storm on Mars is very large, which is 6 times the impact of the 12-level typhoon on Earth. These flying sands will cover the solar panels of the rover, making it unable to work properly. Historically, the first and second generation of American rover cars were stopped by the impact of sandstorms. "This requires fully improving the utilization of energy, including high-efficiency solar cell technology and high-efficiency battery technology, and improving the power-to-mass ratio of the energy system. For example, the solar panel should be as large as possible, and the photoelectric conversion efficiency should be higher." Pang Zhihao said.
Our reporter Fu Lili