A Long March booster launched an unmanned prototype of a manned spacecraft on what may be the final test flight before China attempts launching humans into space.

The Long March 2F rocket lifted off at 12:40 am Monday Beijing time (1640 GMT Sunday) from the Jiuquan Satellite Launching Center in northwestern China. Initial Chinese media reports indicated that the Shenzhou 4 spacecraft "entered its preset orbit" but provided no additional details.

The exact launch date was not announced in advance, and Chinese sources provided no official indication that the launch was scheduled until after liftoff. However, there had been speculation in Chinese and Western media that a launch attempt was planned for the last week of 2002. In August Zhang Qingwei, president of China Aerospace Science and Technology Corporation, said that the launch was planned by the end of 2002.

While no details about the Shenzhou 4 mission have been released other than its launch, the spacecraft is likely carrying both diagnostic instruments to measure conditions within the spacecraft as well as scientific experiments. Chinese media reported earlier this month that included in Shenzhou 4's payload are 100 peony seeds that will be returned to Earth and planted to see how zero gravity exposure affects their growth. Shenzhou 4's mission duration has not been announced, but the last two test flights each lasted one week. Previous missions have landed in Inner Mongolia, although some reports have suggested China may attempt a water landing on this flight.

Shenzhou, Chinese for "divine vessel", is a prototype of a manned spacecraft. While few details about the design of Shenzhou have been released by China, the spacecraft appears to be at least superficially similar to Russia's Soyuz spacecraft. Like Soyuz, Shenzhou is made of three modules: a service module that houses propulsion systems and other equipment, a reentry module used to return crews to Earth, and an orbital module that can remain in orbit after the reentry module deorbits. Shenzhou appears to be slightly larger and heavier than Soyuz.

Development of Shenzhou began in 1993 as part of Project 921, a Chinese effort to develop a manned spaceflight capacity. The effort was not publicly announced until early 1999. Shenzhou was intended to be the first phase of an effort that would later include a small space station and, in the long term, a reusable manned spacecraft, although Chinese officials have released few details about those plans.

China has taken a methodical, cautious approach to its Shenzhou test flights. The first flight, in November 1999, was a short one-day mission. China waited until January 2001 for the second flight, a week-long mission. The lack of images of the Shenzhou 2 spacecraft after landing, in sharp contrast to the publicity surrounding the first flight, led Western analysts to speculate that something had gone wrong with the mission. While Chinese officials never confirmed that speculation, the next Shenzhou launch did not take place until March 25 of this year, when Shenzhou 3 carried out what apparently was a successful one-week mission.

A successful test flight by Shenzhou 4 has led to rumors that the next Shenzhou flight may be manned. In November Hu Hongfu, deputy general manager of China Aerospace Science and Technology Corporation, said that there would be "no difference" between Shenzhou 4 and the spacecraft that would carry humans. About a dozen yuhangyuans - the Chinese name for astronauts - are believed to be training and could be ready for a mission in 2003. When that flight does occur, China will become only the third nation, after Russia and the United States, to launch humans into space.