Long March 4C

Mission: Chang’e-4 is the backup to the Chang’e-3 mission which put a lander and rover on Mare Imbrium (Moon) in late 2013. The relay satellite, recently named Queqiao – or Magpie Bridge, taken from a Chinese folklore tale that sees two lovers reunited once a year when a flock of magpies form a bridge across the Milky Way — will orbit around the Lagrange point around 65,000 kilometers beyond the moon, so as to be visible to both ground stations on the Earth and the lander and rover on the lunar far side at all times. Its main function will be to relay telecommands from the ground to the Chang’e-4 lunar spacecraft and transmit data and telemetry back to Earth via S-band, while using x-band to communicate with the lander and rover.

Rocket: The Long March 4C rocket is a Chinese expendable orbital rocket. It is manufactured by SAST, which is a branch of CASC (China Aerospace Science and Technology Corporation) . Its maiden flight occurred on April 26, 2006 and this will be the 25th attempt to launch it. It weighs 250,000 kilograms (550,000 lb) and can deliver 4,200 kilograms (9,300 lb) to LEO, 2,800 kilograms (6,200 lb) to SSO and 1,500 kilograms (3,300 lb) to GTO.

First Stage: The first stage is 27.91 meters high and 3.35 meters in diameter. It uses four YF-21C engines that produce 2,961.6 kN (665,800 lb_f). It uses N₂O₄ (dinitrogen tetroxide) and UDMH (unsymmetrical dimethylhydrazine).

Second Stage: The second stage is 10.9 meters high and 3.35 meters in diameter. It uses N₂O₄ (dinitrogen tetroxide) and UDMH (unsymmetrical dimethylhydrazine).

Third Stage: The third stage is 14.79 meters high and has a diameter of 2.9 meters. It uses 2 YF-40A engines that produce 100.85 kN (22,670 lb_f). It also uses N₂O₄ (dinitrogen tetroxide) and UDMH (unsymmetrical dimethylhydrazine).