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Shenzhou 8
Shenzhou 8 was the eighth flight of the Shenzhou spacecraft, and the fifth unmanned mission, intended to demonstrate rendezvous and docking between two unmanned space vehicles. The mission would provide useful engineering experience for subsequent manned rendezvous and docking missions and the construction of the future space station.
Space rendezvous and docking was one of the three key techniques, along with extra-vehicular activity (EVA) and long-term space living, to be developed in the second phase of the Project 921. Although the technique was perfected by the United States and Russia in the 1960s, China had to develop the technique almost from scratch. The Shanghai Academy of Spaceflight Technology (SAST) began to develop an androgynous docking mechanism in the mid-1990s, but the system was not ready until 2010 due to technical obstacles.
The Spacecraft
Shenzhou 8 inherited the basic design of the Shenzhou spacecraft, consisting of a front orbital module, a re-entry capsule, and an aft service module, with a total mass of 8,082kg. It was one of the three Shenzhou vehicles (8, 9, and 10) to have been built in batch production. Shenzhou 8 carried two dummies and a biological experiment payload supplied by Germany and the European Space Agency inside its re-entry module. Although unmanned, the spacecraft was exactly identical to that used in a manned mission.
To dock with Tiangong 1, a docking module attached to the front end of Shenzhou 8's orbital module. The docking module consisted of a docking port, radio beacons, transponders, communication antenna, UHF radar, laser rangefinder, and electro-optical tracking system. Translation thrusters were added to the spacecraft for close manoeuvring during rendezvous and docking.
Shenzhou 8 in thermal vacuum chamber test
Docking
Shenzhou 8 was launched on 1 November 05:58:10 China Standard Time (31 October 2011 21:58:10 GMT) from the Jiuquan Satellite Launch Centre, onboard the Changzheng 2F-Y8 launch vehicle. After five orbit elevation manoeuvres in 41 hours, the spacecraft reached a position about 52km away from Tiangong 1 in the afternoon of 2 November (GMT). The first docking was to take place while the two spacecraft flew over Chinese territory, where ground-based tracking stations could provide intensive tracking and telemetry support. The time of the docking was in midnight local time in order to avoid the interruptions of sun flares to the spacecraft's docking and tracking systems.
At 15:08 GMT (23:08 local time), with its tracking radar successfully capturing the target vehicle, Shenzhou 8 switched from ground-guidance mode to self-guidance mode to start its rendezvous sequence. At 16:03 GMT, the vehicle manoeuvred to about 5km to Tiangong 1. After the ground control had checked and confirmed the results of the guidance computers of both spacecraft, Shenzhou 8 fired its rocket thrusters to continue its rendezvous. At 17:02, the spacecraft deployed its docking adapter, ready for the docking.
Shenzhou 8 stopped briefly at 400m away from the target vehicle to allow the final check of the docking systems of both spacecraft by the ground control. When the two vehicles were about 200m apart, Shenzhou 8 switched on its external lighting to illuminate Tiangong 1 in the dark night sky. At 17:16, Shenzhou 8 stopped at the 140m parking point. About 4 minutes later, the spacecraft fired its thrusters to continue its manoeuvre towards Tiangong 1 at a relative speed of 0.5m/s. At 17:23, Shenzhou 8 reached the 30m parking point. After a final check by the ground control, the spacecraft moved towards Tiangong 1 at a relative speed of 0.2m/s.
The two vehicles made their first contact at 17:28 GMT. At the point of impact, Shenzhou 8 fired its thrusters to push its docking adapter on its front end into the docking port of Tiangong 1. In the next 10 minutes, the docking systems of the two vehicles completed a series of actions to ensure a good capture and alignment of the two vehicles’ velocities and orientations. At 17:36 GMT (01:36 local time), the two vehicles were confirmed to have been successfully docked together. The Chief Director of the Project 921, PLA General Chang Wanquan announced at 01:43 local time that the first space rendezvous docking was successful.
Orbital view of Shenzhou 8 from Tiangong 1
The Tiangong 1-Shenzhou 8 complex flew in orbit for 10 days and 20 hours while ground control carried out various checks and tested the flight control of the complex. On 14 November, at 11:24 GMT, Shenzhou 8 undocked with Tiangong 1 under the command of ground control. 4 minutes later, the two vehicles were separated. Shenzhou 8 manoeuvred backwards to a position about 140m away from Tiangong 1 and then closed up to dock with Tiangong 1 again. The second docking exercise was completed at 12:07 GMT.
Re-entry
On 16 November, Shenzhou 8 was undocked with Tiangong 1 for the last time at 10:30 GMT. The spacecraft ignited its rocket thrusters at a distance of 140m to manoeuvre further away from Tiangong 1. The re-entry of Shenzhou 8 began at 10:43 GMT on 17 November. The spacecraft ignited its main engines for retro-fire at 10:46 GMT. Its service module was jettisoned at 11:07 GMT. The re-entry capsule of Shenzhou 8 touched down at the Siziwangqi landing site at 11:32 GMT.
Shenzhou 8 re-entry capsule
Mission Details
| Crew | None |
| Launch vehicle | Changzheng 2F-Y8 |
| Launch pad | Jiuquan Satellite Launch Centre, Pad 921 |
| Launch | 31 October 2011 21:58:10 GMT 1 November 2011 05:58:10 CST |
| Recovery | 17 November 2011 11:32 GMT 17 November 2011 19:32 CST |
| Duration | 16 days 13 hours 33 minutes |
| Orbits | 262 |
Last updated: 26 January 2012