China will launch its unmanned spacecraft Shenzhou VIII early Tuesday for the country’s first space docking, a major step closer to the goal of building a permanent space station around2020.

Commissioned by the Tiangong1/Shenzhou 8 Rendezvous and Docking Mission Headquarters, now I’d like to introduce the flight mission of Shenzhou 8. According to the Headquarters of the mission, the Shenzhou 8 spaceship is scheduled to be launched at 5:58:07 a.m. on November 1, 2011. Propellants have been loaded into the Long March 2F/Y8 launch vehicle since 10 o’clock this morning.

The main tasks of the mission include to perform China’s first space rendezvous and docking tests with Tiangong 1, to make a breakthrough and demonstrate the automatic docking technology; to test the functions and performances of the modified Shenzhou spaceship and Long March 2F launch vehicle as well as the coordination of all systems of the program; and to test the working mode of the assembly and conduct space scientific experiments. Shenzhou 8 spaceship is unmanned.

Being a modified spaceship, Shenzhou 8 is capable of both automatic and manual docking. It follows the three-module configuration, namely the orbital module, reentry module and propelling module. The spaceship has a total length of 9 meters and a maximum diameter of 2.28 meters. Its take-off weight is 8.082 tons. The 5-cubic-meters orbital module is the living cabin for the astronauts, with measuring instruments and active docking mechanisms fitted outside it. The reentry module is the astronauts’ cabin equipped with parachute and landing buffer system. There are instrument panels, commanding boards and manual control handle in it. The propelling module is the power and energy cabin of the spaceship. It has orbital control engine, attitude control engine and solar cell array.

The Long March 2F/Y8, the carrier rocket of the Shenzhou 8 spaceship, is the newly developed version of Long March 2F. The main modifications have been made on booster system, control system and failure detecting system as to improve its carrying capacity and orbit injection accuracy. The total length of the rocket is 58.3 meters and its lift-off mass is 497 tons. Its payload is 8130 kilograms.

According to the flight plan, about 584 seconds after the ignition, the spaceship will be separated from the carrier rocket and sent into the initial orbit with the perigee height of 200 km and apogee height of 330 km. It will complete its first rendezvous and docking with Tiangong1 within 2 days after its launch.

The whole process of the rendezvous and docking with Tiangong 1 can be divided into 5 phases, namely long distance navigation phase, self-controlling guidance phase, rendezvous and docking phase, assembly flight phase, and separating and retreating phase.

The phase of long distance navigation will begin from the entrance of Shenzhou 8 into its designated orbit. After changing its orbits for 5 times under the guidance of the Tracking, Telemetry & Command and Communication (TT&CC) systems on the ground, Shenzhou 8 will transfer from its initial orbit into the near-circular orbit at a height of 330 kilometers, which is in the same orbit surface with Tiangong 1. About 52 kilometers below and behind Tiangong 1, Shenzhou 8 will establish a stable space to space communication link with it and then navigate automatically.

The self-controlling guidance phase can be divided into 3 steps, namely targeting, approaching and horizontal closing-in . It will last for about 2 and an half hour from its self-controlling guidance of Shenzhou 8 to its contact with Tiangong 1.

The rendezvous and docking phase will begin from the contact of the docking mechanisms. Within 15 minutes, the processes of capturing, buffering, approaching and locking will be completed. Finally the two vehicles will be physically connected to form an assembly.

During the assembly flight phase , Tiangong 1 will be in charge of the flight control and Shenzhou 8 will be just docked with it. The assembly will fly for about 12 days before carrying out another docking test at an appropriate time. The whole process will be as follows, the two vehicles will separate from each other after the docking mechanism unlocked; Shenzhou 8 will retreat 140 meters away from the target vehicle, waiting for the second rendezvous and docking to form an assembly again.

The assembly will continue to fly for another 2 days before entering the separating and retreating phase, when the two vehicles will depart from each other again, and the spaceship retreats to a safe distance beyond 5 kilometers away from the target vehicle, ending the test. After that, the reentry module of Shenzhou 8 spaceship will return to the earth, and Tiangong 1 will ascend to an autonomous flight orbit and convert into long-term operation management mode.

During the mission of Shenzhou 8 spaceship, China and Germany will carry out 17 space life scientific experiments using the Sim-Box aboard the spaceship.

At present, all subsystems involved in the mission, including the astronauts system, space application system, manned spaceship system, carrier rocket system, the launching site system, TT&CC system and the landing system, have successfully finished an integrated rehearsal. All preparatory works before launch have been finished.

At the same time, Tiangong 1 target vehicle, since its successful launch on September 29, has successively completed orbital tests and orbital control, and has entered the docking orbit at a height of 343 kilometers. Tiangong 1 is running stably and working normally, with everything ready for the mission.

Source and photo: China Manned Space Engineering