China's newly-developed heavy-lift carrier rocket Long March 5 blasts off at 8:43pm on Nov 3 at Wenchang Space Launch Center in South China's Hainan Province.[Photo/Xinhua]

The last moment of new heavy-lift carrier rocket Long March 5's launch on Nov 3 was the most breathtaking one in the history of China's aerospace attempts, as the launch time was delayed thrice, nearly three hours from the previously scheduled time, said experts.

The new rocket, which is larger and more complicated than other Long March rocket family members, was scheduled to blast off at 6:00 pm at Wenchang Space Launch Center in South China's Hainan province, but finally rocketed into space at 8:43 pm.

A video broadcast by China's national TV station CCTV recently revealed what happened before its successful launch.

Two emergencies caused the delay. The first one happened to the booster 30 minutes before the scheduled launch time. After one-hour check and discussion, experts decided that the problem wouldn't affect the final success. "We thought it was OK to take an hour to carry out the check during the three-hour launch window," said Lou Luliang, deputy chief designer of Long March 5.

The other delay occurred when liquid hydrogen was being injected into the hydrogen oxygen engine. Liquid hydrogen was stored at -253 C and it could lead to explosion if it reaches the engine which has high temperature. But the engine unexpectedly couldn't be cooled down to the required temperature, which meant the experts had to spend nearly two hours to resolve the problem.

"Unexpected problems are inevitable in such a large project," said Long Lehao, chief designer of the Long March rocket series.