The CZ-3B was developed in the 1990s to provide commercial satellite launch for domestic and international customers. By adding four liquid-propellant strap-on boosters to the CZ-3A, the GTO payload capacity of the CZ-3B was further increased to 5,100kg, making it the most capable SLV currently in use in the PRC, and at the time of its introduction the second most capable SLV in the world, only after the Russian Proton.
CZ-3B launch vehicle (Chinese Internet)
The CZ-3B was introduced in the early 1990s to succeed the problem-prone CZ-2E for commercial satellite launch. The maiden flight of the CZ-3B took place on 14 February 1996 GMT (15 February local time), carrying a commercial satellite Intelsat 708. Only two seconds after lifting off from the launch pad at XSLC, the launch vehicle began to veer off course. The vehicle and the payload then hit the ground and exploded at T+22 seconds, destroying the US$125 million satellite. The Chinese official media confirmed that six people were killed during the accident, with another 57 injured. However, some foreign reporters who witnessed the accident estimated as many as 500 could be killed. (see also: CZ-3B disaster video)
The 15 February failure was the most severe accident in the history of PRC’s space programme, and possibly the worst in the world. The cause of failure was traced to the CZ-3B's guidance and control subsystem. A gold-aluminum solder joint in the output of one of the gyro servo loops failed, cutting electrical current output from the power module and causing the inertial reference platform of the vehicle's guidance and control system to slope. This caused computers to send the vehicle veering off the planned trajectory shortly after lift-off. The failed module was the only one of six similar modules that lacked conductive adhesive to reinforce the solder joint.
Despite the initial failure, the CZ-3B made a second launch successfully on 20 August 1997, sending the Philippine Agila 2 MABUHAY satellite into the GTO. This was followed by another six consecutive successful launches. The latest launch took place on 14 May 2007, when a CZ-3B launch vehicle successfully sent the Chinese-made NIGCOMSAT-1 communications satellite for Nigeria into the orbit.
CZ-3C
CZ-3C launch vehicle (Chinese Internet)
In order to fill the payload capacity gap between the CZ-3A and CZ-3B, CALT also developed the CZ-3C, which is almost identical to the CZ-3B, but fitted with only two strap-on boosters. The CZ-3C has a GTO payload capability of 3,800kg, making it suitable for the launch of smaller satellites. The CZ-3C programme was first revealed in the mid-1990s, and the design was approved by the CASC in 2001. The first launch of the CZ-3C is scheduled in April 2008.
Design
The CZ-3B consists of a 3-stage core vehicle with four strap-on stages. The first and second stage of the core vehicle and the strap-on boosters all employ the UDMH/N2O4 (nitrogen tetroxide) storable liquid propellant. The third stage of the core stage uses LOX/LH2.
The first stage of the core vehicle is powered by a YF-21 rocket engine consisting of four YF-20 chambers motors with swinging nozzles, each producing 75,500kg thrust. The second stage of the core vehicle has a rocket engine consisting of one 75,600kg (742kN)-thrust YF-22 main motor with fixed nozzles and a YF-23 swivelling venire motor with four chambers motors (4,800kg/47kN-thrust in total). The payload fairing of the CZ-3B/C is 8.887m in length and 4~4.25m in diameter.
The third stage has a YF-75 LOX/LH2 engine that produces 16,000kg (157kN) thrust, with the restarting ability for increased payload capacity.
The CZ-3B has four 2.25m-diameter strap-on boosters and the CZ-3C has two, each using a single 75,500kg-thrust YF5-1 engine with a fixed nozzle.
