Fourth and final test flight of the Shenzhou spacecraft, without crew on board. The spacecraft was flown in the same configuration as a crew-carrying mission, and as such two dummy astronauts were carried on board, as are sleeping bags, food and medication. The control systems were fitted with ability for manual control and emergency landing. 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 deployed properly. The spacecraft carried 100 peony seeds to investigate the effect of weightlessness on plants grown from them. The 52 experiments onboard investigated areas in physics, biology, medicine, earth observation, material science, and astronomy.