China in surprise launch of Long March 4B with ZiYuan-1

by Rui C. Barbosa and Chris Bergin.

Despite an expected launch date of December 26, China launched their Long March 4B (Chang Zeng 4B) rocket at 03:26 GMT on Thursday from a wintry Taiyuan Satellite Launch Center. The launch – adding to what is a record year for the Chinese, a  year they beat the United States in orbital launches – carried the ZiYuan-1 (2C) Earth observation satellite into orbit.

Chinese Launch:

China’s launch schedule has been moving around in recent months, partly due to the Long March 2C failure in August and partly because of the large number of missions that have been undertaken in what has been a memorable 2011 for the Chinese.

The launch of the ZiYuan-1 (2C) Earth observation satellite was originally tagged for a December 19 launch, prior to that slot being taken by the successful launch of the Long March 3B/E (Chang Zheng-3B/E), which lofted the NigComSat-1R into orbit on behalf of Nigeria from the Xixhang satellite Launch Center.

Eagle-eyed members of the forum then noticed Chinese messageboards talking about the launch moving up the schedule, prior to news of spectators arriving at the launch site for what became Thursday’s lift-off.

Not a great deal of information on the ZiYuan-1 (2C) have been revealed in the Chinese media, other than it is another of China’s Earth observation fleet – as much as this one has been confirmed to be for civilian purposes – sporting two High Resolution HR cameras, capable of a spatial resolution of 2.36m, with a joint swath of 54 km.

Its main feature is its panchromatic multi-spectral camera, which boasts a resolution of five meters and ten meters, with a swath of 60 km – suggesting this is an upgraded version of the Sino-Brazilian CBERS satellite – backed up by an alternative call sign of CBERS-02C.

The satellite – weighing in at a mass of 2,100 kg – will be mainly used by the Ministry of Land and Resources. It is designed to have a service life of three years.

This was the 19th orbital launch of the year for China, beating the United States’ 2011 record of 18 orbital launches.

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The CZ-4B Chang Zheng-4B launch vehicle:

The feasibility study of the CZ-4 Chang Zheng-4 began in 1982 based on the FB-1 Feng Bao-1 launch vehicle. Engineering development was initiated in the following year. Initially, the Chang Zheng-4 served as a back-up launch vehicle for Chang Zheng-3 to launch China’s communications satellites.

After the successful launch of China’s first DFH-2 communications satellites by Chang Zheng-3, the main mission of the Chang Zheng-4 was shifted to launch sun-synchronous orbit meteorological satellites. In other hand The CZ-4B Chang Zheng-4B launch vehicle was first introduced in May 1999 and also developed by the Shanghai Academy of Space Flight Technology (SAST), based on the CZ-4 Chang Zheng-4.

The rocket is capable of launching a 2,800 kg satellite into low Earth orbit, developing 2,960,000 kN at launch. With a mass of 249,000 kg, the CZ-4B is 45.80 meters long and has a diameter of 3.35 meters.

SAST began to develop the Chang Zheng-4B in February 1989. Originally it was scheduled to be commissioned in 1997, but the first launch didn’t take place until late 1999.

The modifications introduce on the CZ-4B Chang Zheng-4B included a larger satellite fairing and the replacement of the original mechanical-electrical control on the Chang Zheng-4 with an electronic control.

Other modifications were an improved telemetry, tracking, control, and self-destruction systems with smaller size and lighter weight; a revised nuzzle design in the second stage for better high-altitude performance; a propellant management system for the second stage to reduce the spare propellant amount, thus increasing the vehicle’s payload capability and a propellant jettison system on the third-stage.

The Chang Zheng-4B uses UDMH/N2O4 for all three stages. The first stage uses a YF-21B motor consisting of four 75,000kg thrust YF-20B thrust chambers motors with swinging nozzles. The second stage is similar to that of the CZ-3A, with a YF-24F rocket motor consisting of one 75,000kg thrust YF-22B main motor with fixed nozzles, and a YF-23F swivelling venier motor with four chambers motors (4,700kg thrust in total).

The third stage is a specially designed unit powered by a 98kN YF-40 rocket motor.

The Taiyuan Satellite Launch Center:

Situated in the Kelan County on the northwest part of the Shanxi Province, the Taiyuan Satellite Launch Center (TSLC) is also known by the Wuzhai designation. It is used mainly for polar launches (meteorological, Earth resources and scientific satellites).

The center is based at a location 1400-1900m above sea level, and is surrounded by mountains to the east, south and north, with the Yellow River to its west. The annual average temperature is 4-10 degrees C, with maximum of 28 degrees C in summer and minimum of -39 degrees C in winter.

TSLC is suitable for launching a range of satellites, especially for low earth and sun-synchronous orbit missions. The center has state-of-the-art facilities for launch vehicle and spacecraft testing, preparation, launch and in-flight tracking and safety control, as well as for orbit predictions.

(Images via member “1706892431“, and ChinaNews).

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