The Long March CZ-5 heavy-lift rocket sitting on a launch pad at the Wenchang Satellite Launch Centre in Hainan is China’s most powerful rocket ever, and also its most fragile.

Scheduled to blast off on Thursday afternoon, according to computer calculations it will be China’s safest launch, and yet it is also being regarded as the riskiest in decades.

The CZ-5 project has suffered years of delays, with its entire research and development process plagued by accidents and failures, with many technological and engineering problems being bigger than mainland rocket scientists and technicians expected.

But it “must be built, must be launched, must be a success”, said a scientist involved in the project who requested anonymity, “otherwise the Chinese space programme will always live as a dwarf in the shadow of giants”.

The CZ-5 can lift 25 tonnes of cargo into low-earth orbit, two and a half times as much as the previous most powerful Long March rocket. To do that it required a whole new family of engines. The first stage of the CZ-5 consists of two large YF-77 liquid hydrogen/oxygen engines and the four boosters each have a pair of YF-100 kerosene/oxygen engines.

The rocket engine development and testing took place at a facility hidden in a valley to the south of Beijing. Residents living nearby, already used to ground tremors accompanied by deep, explosive blasts, detected a noticeable increase in testing activity in recent years.

According to official accounts, the first test-firing of the main engine was a failure, as was the second, third and fourth.
“Each failure dealt a heavy blow to the whole rocket team,” CZ-5 designer in chief Li Dong said in a documentary film released by China Central Television in April.

The first two prototypes exploded immediately after ignition, the others perished in flame and smoke due to fuel leaks.
“Some foreign experts said we would never be able to bring the engine from the drawing board to life,” Li said… see more

source: scmp