Shenzhou 4 launched on December 29, 2002, was the fourth unmanned launch of the Chinese Shenzhou spacecraft. Carried on board was two dummy astronauts to test the life support systems.

The spacecraft was equipped for a manned flight, even featuring a sleeping bag, food and medication. The windows were constructed of a new material that was designed to stay clear even after reentry to allow an astronaut to confirm that the parachutes have properly. It was said that the spacecraft flown on Shenzhou 4 had no major differences to that used on Shenzhou 5. It flew with the ability for manual control and emergency landing, systems needed for a manned flight. A week before the launch, astronauts trained in the spacecraft to familiarize themselves with its systems.

Initially the spacecraft was in a 198 km by 331 km orbit inclined 42.4°. This was raised to 330 km by 337 km at 23:35 UTC on December 29. Also on January 4 and January 5 several smaller manoeuvres are thought to have taken place. The rate of orbital decay seemed higher after January 1 suggesting that the orbital module's solar panels may have been deployed for the first time. Compared to Shenzhou 3 the orbital period of Shenzhou 4 was much more tightly bounded with smaller manoeuvres.

The spacecraft carried 100 peony seeds to investigate the affect of weightlessness on plants grown from them. The 52 experiments onboard investigated areas in physics, biology, medicine, earth observation, material science and astronomy.

Four tracking ships were used for the mission — one of the coast of South Africa in the South Atlantic Ocean, one in the Indian Ocean near Western Australia, one in the North Pacific Ocean south of Japan, and one in the South Pacific Ocean west of New Zealand.

The reentry module landed safely on about 40 km from Hohhot in Inner Mongolia. As with previous flights, the command for reentry to begin was given by a tracking ship off the coast of South Africa. It was thought before the flight that the Chinese could attempt a water landing to test the emergency system but this did not eventuate. The orbital module remained in orbit until September 9, 2003.

Mission statistics

Mission name: Shenzhou 4

Launch: December 29, 2002 16:40 UTC

Jiuquan Satellite Launch Center

Landing: January 5, 2003 11:16 UTC

Inner Mongolia

40°31′ N, 111°23′ E

Duration: 6 days 18 hours 36 minutes

Orbits: 108

NSSDC ID: 2002-061A

(Source: Wikipedia)