¡¡¡¡BEIJING, Dec. 30 (Xinhuanet) -- China launched its fourth unmannedspacecraft, the "Shenzhou IV", early Monday at the Jiuquan Satellite Launch Center in northwestern Gansu Province.

¡¡¡¡The first experimental spacecraft "Shenzhou" was launched by "Long March" carrier rocket on Nov. 20, 1999, at the same launch center, and touched down in the Inner Mongolia Autonomous Region the next day.

¡¡¡¡Chinese engineers for the first time assembled and tested the rocket and spaceship in a vertical way. Meanwhile, they used a newly-established network, covering land and sea, to control and monitor the spacecraft.

¡¡¡¡On Jan. 10, 2001, China launched the second unmanned spaceship "Shenzhou II" which was basically identical to a manned craft.

¡¡¡¡Scientists designed space life sciences, space materials, spaceastronomy and space physics experiments under conditions of microgravity in outer space.

¡¡¡¡"Shenzhou II" performed well in orbiting the earth and brought back much important scientific data after its return.

¡¡¡¡On March 25, China launched its third unmanned craft "Shenzhou III", which could carry out the functions of a manned craft.

¡¡¡¡A set of metabolic simulation apparatus, human physical monitoring sensors and dummy astronauts have been installed aboardthe spaceship.

¡¡¡¡During the test launch, space scientists for the first time tested the escape system, which could save the lives of astronautsduring the launch.

¡¡¡¡Its orbital module ran for about 180 days in outer space, circling Earth 2,821 times. A number of space science experiments were conducted, such as the orbital change of flying objects at low orbits, analysis of fall, better way to fuel distribution, fault detection and emergency management. Enditem