LONG MARCH 3 (CZ-3)

The Long March 3 was introduced in order to give China the capabihty of flying to geosynchronous orbit. Although a new name, it was actually an adaptation of its first two stages of the Long March 2, adding a powerful, hydrogen – fuelled upper stage, while later versions added strap-ons to give the rocket much extra lift at take-off. The Long March 3 was introduced in January 1984. Although the satellite launched was left stranded in low Earth orbit, the rocket has since then been used successfully for both domestic and foreign communications satellite launches (Chapter 5), as well as weather satellites (Chapter 6). After 13 missions, it was retired with the Feng Yun 2 weather satellite in 2000. The Long March 3 was a single stack, without strap-on rockets, and gave way to three variants: the ЗА, the powerful 3B, and the most recent, the 3C.

The Long March ЗА was the first variant of the Long March 3, introduced 10 years later, offering substantially improved performance and able to place about twice the weight in geosynchronous orbit. It had a stretched first stage and bigger third stage. The third stage was entirely redesigned and carried two YF-75 engines (rather than one on the Long March 3). Ten small engines were fitted to the third stage in an attempt to settle the propellant before its second ignition. The Long March ЗА had a new, advanced digital computer system. It has been used to fly communications and navigation satellites and, later, China’s first Moon probe.

The Long March ЗА continues in service, but is now supplemented by the Long March 3C, introduced on the Tian Lian data relay launch on 25th April 2008 and used subsequently for Beidou missions and the Chang e 2 lunar mission. In effect, it is the CZ-3A with two strap-ons, giving

Long March 2F profile, with escape tower on top. Courtesy: Mark Wade.

it the much greater capacity of 3.9 tonnes to geostationary transfer orbit. This makes it much heavier (345 tonnes) and slightly taller (55 m).

The Long March 3B is the most powerful rocket in the Chinese armory of unmanned spaceflight (5,923-kN thrust), with four strap-on rockets to achieve a payload of between 4.8 and 5.5 tonnes to geosynchronous orbit. The 3B took a number of systems directly from the ЗА, such as engines, electronics, guidance, and computer controls, but with larger propellant tanks, a larger nose fairing, and better computer. The Long March 3B got off to a bad start, crashing on its maiden flight on St Valentine’s Day in 1996, but subsequently going on to be China’s main lifter of domestic and foreign communications satellites. Modifications were made in 2009 to increase payload to 5.5 tonnes (lengthening the booster by 77 cm, the first stage by 1.49 m, and modifying the fins). Details are given in Table 3.5.