China Longmarch-3B

Long March 3B: The "Gold Standard" of China's High-Orbit Aerospace

In the vast journey of cosmic exploration, the Long March 3B launch vehicle (CZ-3B) has always been an indispensable core force in China's aerospace industry. Developed by the China Aerospace Science and Technology Corporation, this three-stage liquid-propellant launch vehicle with strap-on boosters is not only a mainstay for high-orbit launches, but also a "gold standard" in China's aerospace projects thanks to decades of technological iteration and stable performance. It has left countless glorious marks in the fields of Beidou navigation network, lunar exploration program, deep-space exploration and international commercial launches.

In terms of basic performance, the Long March 3B demonstrates excellent adaptability and launch capability. The standard version has a total length of 56.3 meters, while the improved version can reach 56.5 meters due to the extended fairing. The first and second core stages have a diameter of 3.35 meters, the strap-on boosters 2.25 meters, the third core stage 3.0 meters, and the maximum diameter of the fairing is 4.2 meters, featuring a compact and well-organized overall structure. In terms of liftoff mass, the standard version reaches 456 tons, and the enhanced version (LM-3B/E) is upgraded to approximately 480 tons through structural optimization. Correspondingly, its geosynchronous transfer orbit (GTO) payload capacity has also made continuous breakthroughs – from the initial 5.1 tons, to 5.5 tons for the enhanced version in 2006, and further to 5.55 tons after the "dual enhancement" project in 2023. As of December 2024, the Long March 3B has completed 100 launches, becoming China's first "100-launch rocket", and its 98.6% success rate is the best proof of its reliability. It has a wide range of missions and can flexibly perform launches to geosynchronous orbit, medium Earth orbit and sun-synchronous orbit. When it successfully launched the Tianwen-2 probe in May 2025, it even broke through the Earth-escape orbit technology, achieving a launch speed of over 11.2 km/s with an orbit insertion accuracy error of less than 1 meter, demonstrating top-tier orbit control capability.

As the "heart" of the rocket, the engine system provides strong power for the stable operation of the Long March 3B. The rocket adopts a staged propulsion design. Each of the 4 strap-on boosters is equipped with one YF-25 engine, with a single-engine sea-level thrust of 740.4 kN. Together with the YF-21C engine (vacuum thrust of 2961.6 kN) for the first core stage and the YF-24E engine (vacuum thrust of 742 kN) for the second core stage, they all use dinitrogen tetroxide/unsymmetrical dimethylhydrazine (N₂O₄/UDMH) as propellants, providing sufficient thrust for the rocket's liftoff and ascent phases. The YF-75 cryogenic engine (using liquid hydrogen/liquid oxygen) equipped in the third stage is a technical highlight, with a vacuum thrust of 80 kN and a specific impulse of 421 seconds. It has the capability of restarting and can accurately send satellites into the target orbit. During the "dual enhancement" project in 2023, the pressure cylinders of this engine were also removed and the pre-cooling process was optimized, further improving reliability and fuel efficiency.

Looking back at the development history of the Long March 3B, every step of it has been accompanied by technological breakthroughs and self-transcendence of China's aerospace industry. In 1986, to meet the needs of international commercial satellite launches, the R&D team officially initiated the development of the Long March 3B, with the Long March 3A (CZ-3A) as the core stage and drawing on the strap-on booster technology of the Long March 2E (CZ-2E). In February 1996, the rocket's first flight failed due to a fault in the inertial reference system. However, the R&D team did not give up. After more than a year of technical research, they successfully launched the Mabuhay satellite of the Philippines in August 1997, marking the breakthrough of its technical bottlenecks and the official start of its service life. Since then, the Long March 3B has undergone continuous iteration and upgrading: in 2006, the strap-on boosters were lengthened to increase the payload capacity to 5.5 tons, forming the enhanced version; in 2011, the dual laser inertial measurement unit redundancy design was introduced to greatly improve the reliability of the control system; the "dual enhancement" project in 2023 further enhanced mission adaptability through optimizing trajectory design and replacing insensitive pyrotechnics. In major missions, it has also achieved remarkable results – launching Chang'e-3 in 2013 to realize China's first soft landing on an extraterrestrial body; sending Chang'e-4 into space in 2018 to complete the world's first soft landing on the far side of the moon; completing the 100th launch in December 2024, becoming a milestone in China's aerospace history; and helping Tianwen-2 embark on an asteroid exploration journey in 2025, pushing China's deep-space exploration into a new stage.

The significance of the Long March 3B has long gone beyond being a launch vehicle; it has become an important symbol of China's aerospace strength. In major national projects, it is an absolute "backbone force" – having sent a total of 64 Beidou satellites into orbit to support the completion of the global positioning system; undertaking the launch missions of Chang'e-3 and Chang'e-4 to build a key bridge for lunar exploration; in the Tianwen-2 mission, the high-orbit and high-precision launch capability it verified has laid the foundation for subsequent asteroid sample return missions. In the international commercial aerospace field, since entering the market in 1997, it has launched more than 20 satellites for countries such as the United States, France and the Philippines, including Apstar-2R and W3C. With its high reliability and flexible adaptability, it has become the first choice of international customers, significantly increasing the global share of China's commercial aerospace industry. In terms of technological innovation, its modular design enables the generalization of the core stage and strap-on boosters, and can form a series of payload capacities by combining different numbers of strap-on boosters; the modified Type V in 2020 applied technologies such as online fault identification and active load reduction for the first time, accumulating experience for the development of intelligent rockets; in 2024, it achieved high-density operations with 14 launches a year, supporting the high-frequency mission needs of China's aerospace industry.

From the failure of its first flight in 1996 to the breakthrough in deep-space exploration in 2025, over the past nearly 30 years, the Long March 3B has become a "golden rocket" in China's aerospace industry with continuous improvements and stable performance. It has witnessed China's aerospace industry's technological leap from conventional propulsion to cryogenic propulsion, and from single-orbit launch to deep-space exploration. It has also injected strong impetus into China's efforts to become an aerospace power through commercial and international development paths. In the future, even with the successive debut of new-generation manned rockets and heavy-lift rockets, the Long March 3B will continue to shine in fields such as high-orbit communications and deep-space exploration, writing a new legend of China's aerospace industry.