A Chinese Long March 3B rocket blasted off from the Xichang Satellite Launch Center at 16:25 UTC on Tuesday, carrying a secretive communications satellite to Geostationary Transfer Orbit. Confirmation of mission success was provided by sources with contacts in the Chinese space sector, though official confirmation of a successful launch is typically published hours after the fact in official Chinese media.
The secretive communications satellite is known as ChinaSat-2C, or Zhongxing-2C, part of a series of military communications satellites operated by the Chinese armed forces. No information or technical details are available on the satellite, though its designation reveals that it is likely belonging to the second generation of Shentong tactical communications satellites designed to deliver secure voice and data communications to ground terminals operating at the Ku-Band frequency.
Shentong was inaugurated in 2003 when ChinaSat-20 entered orbit, followed by another first generation launch in 2010. ChinaSat-2A, the first in the Shentong-2 series, was lifted to orbit in May 2012. Because the ChinaSat designation includes both commercial and military communications satellites, the differentiation between the two becomes somewhat more complex, though the lack of information available on the 2C satellite clearly suggests military operation.
The Chinasat-2A satellite is based on the DFH-4 satellite platform built by the China Academy of Spaceflight Technology which is likely utilized for the 2C satellite launched on Tuesday.
The DFH-4 bus represents a third generation communications satellite platform, capable of facilitating high-power and high-capacity communications payloads for different applications such as direct broadcasting, tracking and data relay, mobile communications, etc.
DFH-4 measures 2.36 by 2.10 by 3.60 meters in dimensions and can accommodate payloads of up to 588 Kilograms, creating a launch mass of a maximum of 5,200 Kilograms. Two 6-meter solar arrays generate an End-of-Life power of 10,500 Watts of which 8kW are available to the payload. DFH-4 is divided into three modules – the propulsion module, the service module and the payload module. Onboard batteries are used to store power for night passes and power distribution is provided by dedicated avionics systems.
The DFH-4 satellite platform uses state of the art navigation and attitude determination systems and reaction wheel-based attitude actuation. The satellite is equipped with a main propulsion system for the climb to Geostationary Orbit and reaction control thrusters used to assist in attitude control and stationkeeping in the Geostationary Belt that is possible with an accuracy of +/-0.05° in all directions. DFH-4 is built to host C, Ku, Ka and L-Band payloads with a nominal service life of 15 years.
Lifting off from Xichang after midnight local time, the 56.3-meter rocket weighing 456 metric tons completed a short vertical ascent before aligning itself with a south-easterly trajectory, taking it over the Yunnan, Guizhou and Guangxi provinces, the Gulf of Tonkin, Hainan Island and out over the Pacific Ocean.
With its four liquid-fueled boosters and large core stage firing at full throttle, the Long March 3B had a total launch thrust of 604 metric-ton-force.
The four boosters, 16.09 meters long and 2.25 meters in diameter, were to fire for two minutes and 20 seconds – each delivering 740 Kilonewtons of additional thrust and burning through 41,100 Kilograms of hypergolic propellants. After separation of the boosters, the vehicle was to continue ascent powered by the core stage alone, fitted with a four-chamber DaFY-6-2 engine cluster providing 2,961 Kilonewtons of thrust. The stage stands 24.76 meters tall and holds 186,200 Kilograms of propellants at liftoff enabling it to burn for 158 seconds.
Separation of the stages was planned to occur in hot mode, starting with the ignition of the second stage’s vernier engine and followed by the firing of cutting charges to allow the second stage to pull away from the spent core for main engine ignition. The 12.9-meter long second stage, holding 49,000kg of propellants, was expected to burn for nearly three minutes with a total thrust of 742 Kilonewtons.
Assuming control of the flight, the third stage was to ignite its YF-75 dual engine cluster that, unlike the other CZ-3B stages, burns Liquid Oxygen and Liquid Hydrogen. Generating 157 Kilonewtons of thrust, the third stage was to burn through 18,200 Kilograms of cryogenics over the course of two burns to raise the apogee of the orbit and achieve a Geostationary Transfer Orbit for spacecraft separation just over 26 minutes into the flight.