The Long March 3B is a Chinese orbital launch vehicle having three stages, with an optional fourth stage. The rocket has four liquid-fueled side boosters, and was first launched in 1996. The Long March rockets have subsequently maintained an excellent reliability record. Since 2010, Long March launches have made up 15–25% of all space launches globally.

A Long March-3B rocket carrying two new-generation satellites for the BeiDou Navigation Satellite System (BDS) blasts off from the Xichang Satellite Launch Center in the southwest China’s Sichuan Province, July 25, 2015. Photo Credit: Xinhua / Zhu Zheng
A Long March-3B rocket carrying two new-generation satellites for the BeiDou Navigation Satellite System (BDS) blasts off from the Xichang Satellite Launch Center in the southwest China’s Sichuan Province, July 25, 2015. Photo Credit: Xinhua / Zhu Zheng

The Long March 3B/E, the enhanced version of the Long March 3B, was first launched in 2007 and has greater Geostationary Transfer Orbit (GTO) payload capacity. The enhanced 3B/E’s have a larger first stage and larger side boosters, compared to the original Long March 3B. As a result, its payload capacity to GTO was increased from 5,100 kg to 5,500 kg. In 2013, it successfully launched China’s first lunar lander Chang’e 3 and lunar rover Yutu.

The Long March 3 family of rockets (Credit: CGWIC)
The Long March 3 family of rockets (Credit: CGWIC)

Design

Side Boosters

The Long March 3B/E utilizes four side boosters that each use one YF-25 engine, which is powered by Unsymmetrical Di-Methyl Hydrazine (UDMH) and Nitrogen Tetroxide (N2O4). Measuring 16.1 m in length, the side boosters produce 740 kN of thrust at lift off, with the engines burning for 140 s and an ISP of 260 s.

First (center) Stage

The first stage has four YF-21C engines, which again uses UDMH and N2O4 as propellants. The first stage has an ISP of 260 seconds and produces 2,960 kN of thrust at sea level. The Long March 3B/E’s first stage measures 3.35 m in diameter and 24.76 m in height.

Second Stage

The second stage is powered by a single YF-22E engine. However, attitude control is provided by a single YF-23 Vernier engine, and combined, these engines are known as a YF-24 module. Just like the side boosters and the first stage, the engine runs on UDMH and N2O4 and produces 742 kN of thrust. The second stage is again 3.35m in diameter and 12.9 m tall, while burning for approximately 185 seconds during flight.

Long March 3B/E launch with APStar-9
Long March 3B/E launch with APStar-9 (Credit: ChinaNews.com)

Third Stage

The Long March 3B/E third stage is 12.4m long and is powered by two YF-75 engines. Unlike the other stages, this stage is high energy/efficiency stage powered by liquid hydrogen (LH2) and liquid oxygen (LOx). Since this engine only performs in the vacuum of space, efficiency is more important than thrust, it only produces 157 kN, while having a specific impulse of around 440 s.

Optional Fourth Stage

The optional fourth stage again runs on UDMH and N2O4, and has a singular YF-50D engine producing 6.5 kN at an ISP of 315 s. It is unclear if this stage will be used for this launch.

Video: Long March-3B launches TJSW-6 (Credits: SciNews)

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