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| Last updated at: (Beijing Time) Friday, October 17, 2003 |
Expert on technological advantages of 'Shenzhou' spacecraft, 'Long-March' carrier rocket
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| After the successful return of China's first manned space craft "Shenzhou V" ("Shenzhou" means "magical vessel"), Zhang Qingwei, deputy general commander of the nation's Manned Space Flight Project and president of China Aerospace Science & Technology Corporation, received an interview by our reporter on the points of advanced technology applied in the craft and its carrier rocket. |
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After the successful return of China's first manned space craft "Shenzhou V" ("Shenzhou" means "magical vessel"), Zhang Qingwei, deputy general commander of the nation's Manned Space Flight Project and president of China Aerospace Science & Technology Corporation, received an interview by our reporter on the points of advanced technology applied in the craft and its carrier rocket.
Shenzhou, a wonderful vehicle shuttling between the Earth and spaceFrom 1999 to 2003, China successfully launched five space ships, four unmanned and one manned, and achieved breakthrough in 13 key technologies including reentry lift control of manned spacecraft, emergency rescue, soft landing, GNC malfunction diagnosis, module separation and heat prevention. As a cross-century project of China in the hi-tech field, "Shenzhou" is of a superior general performance, which reaches the world advanced level in the 1990s.
"Shenzhou" carries distinct Chinese characteristics in terms of its structure and general mode. It is of a high starting point and intellectualization degree. Although China's manned spacecraft program starts rather late, it doesn¡¯t repeat the steps of "Gagarin" times--from being unmanned, to manned by a single polit, then finally to manned by a group of restaurants--but cross forty-year development by Americans and Russians by a single stride. "Shenzhou" is capable of carrying three astronauts from the very beginning; for the first manned flight, Gagarin only flied around the Earth for one circle, Alan B. Shepard Jr only made sub-orbital flight, but Chinese astronaut flied for one day on low earth orbit. Foreign manned spaceships firstly tried on small animals their astronaut environment control and life guarantee systems, while China adopted an advanced modern device--simulated man--to imitate the oxygen and carbon dioxide consumed by "astronaut", and track the changes of its life signals through ground observation stations.
"Shenzhou" is highly adaptable. Its orbital module can stay in orbit for to-the-ground observation, and at the same time as an aircraft prepare for rendezvous and docking in future. In foreign countries two space ships are launched successively for one time, but in China one is launched firstly and its orbital module stays to dock with the next one. To realize rendezvous and docking foreign countries have to launch 2N times, but China N+1 times, provided N>1. For example, if N is 5, foreign countries need to launch 10 spaceships but China only 6. So, in this way, with a smaller total number of spacecraft launched, China could save a large amount in launching cost and at the same time use its stayed orbital module for scientific experiments. China is taking on a road of manned spacecraft of low cost and high returns.
Compared with "Mercury", America's first test spacecraft, and "Vostok", Russia's first test spacecraft, "Shenzhou" displays distinguishable technological advantages, says Zhang. (see Table 1.)
Table 1: Main technological indexes of the first spacecraft of China, the United States and the Soviet Union
| Project |
Mercury |
Vostok |
Shenzhou |
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| Launch mass (T) |
Around 1.4 |
Around 4.7 |
7.8 |
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| Maximum cabin diameter (m) |
1.8 |
2.3 |
2.5 |
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| Reentry mode |
Ballistic |
Ballistic |
Lifting |
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| Power |
Storage battery |
Storage battery |
Solar cell array |
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| Structure |
Cabin, braking module |
Reentry module, instrument module |
Attached section, orbital module, reentry module, propelling module |
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China's Shenzhou far exceeds US Mercury and Soviet Union's Vostok in terms of launch mass and maximum cabin diameter. Its structure, compared with the two-module structure of the two former spaceships, enables more functions and calls more sophisticated technologies in the connection and separation of electricity, gas and liquid lines between modules and the attached section. Shenzhou is mainly powered by solar cell array, an electricity system much more advanced than those of Mercury and Vostok. Especially, Shenzhou adopts the lifting reentry mode, with the lift controlled by GNC sub-system during the reentry process. This is a returning way more advanced than the ballistic one, since it could raise by large margin the precision in returning to the planned site and reduce the reentry overload peak, thus reducing the overload pain suffered by astronaut when returning to the ground.
Table 2. Comparison between "Soyuz TM" and "Shenzhou"
| Project |
Soyuz TM |
Shenzhou |
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| Launch mass (T) |
7 |
7.8 |
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| Maximum cabin diameter (m) |
2.2 |
2.5 |
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| Reentry mode |
Semi-ballistic |
Lifting |
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| Precision of landing site |
Circle with a radius smaller than 30 km |
Theoretical deviation 15 km ±9 km |
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| Reentry overload peak (g) |
3-4 |
3.24 |
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Compared with Soyuz TM spaceship, an advanced type in the 1990s, Zhang points out, Shenzhou has equivalent performance in terms of reentry mode, landing precision and reentry overload peak, providing a more comfortable environment for astronaut's work and life. (see Table 2.)
Long-March II carrier rocket reaches world advanced level in reliability, safety and success rateThe Long-March II-F carrier rocket precisely sent "Shenzhou" spacecraft into the vast space for five times, and it has reached world advanced level in its reliability, astronaut's safety and success rate, with their indexes standing at 0.97, 0.997 and 100 percent respectively. China's various kinds of carrier rocket products have lived up to expectation in their design, quality, performance and flight results. The Long-March II-F rocket, with its excellent general performance, marks a mature stage for China's space carriers. This time's launch is the 71st flight of the Long-March rocket family, as well as its 29th successful mission in succession since October 1996. The launching success rate for Long-March rocket is 91 percent.
The Long-March II-F rocket is a brand-new rocket used for the first time in manned spacecraft launching in China's space history, and among China's carrier rockets it is of the biggest launch mass, length and the most sophisticated systems. The rocket runs a full length of 58.3 meters, topped by an escape tower. Its launch mass is 479.8 tons, carrying capacity 7,800 tons, capable of sending spacecraft into the 200km-450km low earth orbit.
On the Long-March II-F rocket are adopted 55 new technologies, among which the key items such as the malfunction detection system and the escape system are difficult questions even in the world. The rocket, at its waiting-for-blast period and the ascent stage, can automatically check and diagnose malfunctions, then send information to the escape system to realize astronaut automatic escape and escape upon ground command.
To raise the rocket's reliability and safety, redundant technology is applied to important systems and key parts of Long-March II-F, which amounts to a "double indemnity" to the rocket. Once malfunction occurs in the main system, the rocket could rapidly shift to the backup system to ensure normal operation and astronaut safety.
The Long-March II-F realized "three verticles" in China's space flight history¡ªvertical general assembling, vertical testing and vertical transportation to the launching area. Testing and launching can be conducted at a 1.5 km distance. All these reached world advanced levels.
The Vostok is carried by "Vostok" rocket, Soyuz and Progress by "Soyuz" rocket. America's Mercury is firstly launched by "Redstone" rocket for sub-orbital flight, while Gemini is launched by "Gemini" rocket, (i.e. Titan II LV4).
The Vostok carrier rocket, designed by Sergey P. Korolev, runs a full length of 38.36 meters. With a launch mass of 287 tons and a taking-off thrust of 4002.5 KN, it is capable of sending a payload of 4.7 tons into low earth orbit. The rocket carried 92 flights from 1970 to 1989, 91 succeeded, or 98.8 percent. Soyuz rocket is developed on the base of Vostok, its low-earth carrying capacity raised from 4.7 tons to 7.2 tons. By April 1993, Soyuz had launched 1012 missions, 17 failed, success rate 98.3 percent.
The "Redstone" rocket is the first manned spacecraft carrier for sub-orbital flights for the US, while "Atlas" carries Mercury, the first-generation manned spacecraft of the US, for flights around the earth. Mercury-Atlas runs a full length of 29.07 meters, with a launch mass of 117.93 tons and a taking-off thrust of 1610.26 KT. It conducted four sub-orbital flights and two around-the-earth orbit flights, four succeeded and two failed. "Gemini" rocket is developed on the base of Titan II missile, and is specially used for the Gemini spacecraft, America's second-generation manned spaceship. The rocket runs a full length of 33.22 meters, with a launch mass of 148.3 tons and a taking-off thrust of 1912.7 KN, and is capable of sending a payload of 3,620 km into 483-km orbit. Since March 1965, Gemini launched in succession ten spacecraft manned by two each, the flights all succeeded.
By People's Daily Online |
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