Long March 4B launches Shi Jian-6 duo – China aiming for record year

by Rui C. Barbosa

The Chinese are continuing to push towards a record year for launches, as a Long March 4B (CZ-4B Chang Zheng-4B) lofted the Shi Jian-6 Group-04 satellites (SJ-6G Shi Jian-6G and SJ-6H Shi Jian-6H) from the Taiyuan Satellite Launch Center at 00:49 UTC, Wednesday.

Chinese Launch:

As with previous missions for this series of satellite, the two new satellites are tasked with probing the space environment, along with conducting other related space experiments. The Shi Jian-6 Group-04 satellites are likely to replace the Shi Jian-6 Group-03 spacecraft, which were launched on October 25, 2008 – also from the Taiyuan Satellite Launch Center.

Previous satellites were built by the Shanghai Academy of Space Flight Technology and Dongfanghong Satellite Company under subcontract to the China Aerospace Science and Technology Corporation.

According to sources, the mission of the SJ-6 Shi Jian-6 satellites also includes “electronic intelligence technology tests”.

This was the 133rd successful Chinese orbital launch, the 133nd launch of a Chang Zheng launch vehicle, the 31st successful orbital launch from Taiyuan (the second in 2010) and the 11th orbital launch in 2010.

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. 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 (LEO), 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 introduced 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 included an improved telemetry, tracking, control, new self-destruction systems and a revised nozzle design in the second stage for better high-altitude performance. It also includes a propellant management system for the second stage, to reduce the spare propellant mass – 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 vernier 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.

Situated in the Kelan County in the northwest region 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).

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.

The next Chinese launch will likely take place on October 30, when a CZ-3C Chang Zheng-4C launch vehicle will orbit a new navigation satellite, the BeiDou-2 ‘Compass-G4’. The Chinese are also expected to launch the ZX-20A ZhongXing-20A (ST-1B Shen Tong-1B ) military communications satellite, the BeiDou-2 ‘Compass-I2 navigation satellite and the FY-3B Feng Yun-3B meteorological satellite.

(Launch Image from ChinaNews)

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