Full coverage: Successful Launch of Long March-7 Rocket

For more on China's new carrier rocket Long March-7, let's bring in my colleague Wu Guoxiu.

Q1. Guoxiu, what makes it different from other rockets that are currently in service in China?

Answer: Well, let's start on its appearance. The rocket- the result of eight years of work by its developers- is over 53 meters -high, with a 3.35-meter diameter. This is not too much different from the current Long March 2, 3 and 4 models that China currently uses, and which the 7 series aims to replace. But a most obvious change is the four rocket boosters. These are double the length of that of China's current rocket and mean a dramatic increase in the rocket's power.

Although it weighs hundreds of tons, its shell is incredibly thin the thinnest part is as thin as an egg shell. This reduces its weight, enabling it to increase its payload. Talking about payload, the Long March 7 can carry 13.5 tons into low Earth orbit, making it comparable to other advanced rockets internationally. Other Chinese medium-lift rockets can currently carry just 8.6 tons. Inside, the new rocket has a more complicated structure, and and a more advanced control system. It uses 143 pieces of software, 30 times more than traditional rockets, which greatly increased its accuracy.

Usually the weather is an important consideration in rocket launches in China. But wet air and rain are hard to avoid at Wenchang, so the Long March-7 has been specially designed for the conditions. It also has a device to overcome gale-force winds.

The new rocket will also be more environmentally friendly. It relies on liquid oxygen and kerosene as propellants, which is cheaper and less dangerous than those used by some of the earlier rockets. It will leave no pollution as it emits only carbon dioxide and water.

Q2. Guoxiu, aside from the rocket, the launch center at Wenchang is also drawing a lot of attention. Why did China build this new launch center?

Answer: China previously had 3 space launch centers Jiu Quan, Xi Chang and Tai Yuan. These are all based inland. So what's special about the new coastal Hainan Space center? Let's find out in this story.

Internationally space launching centers are usually built on low latitudes and as closer as possible to the equator in order to gain initial speed from the earth's rotation. Hainan being one of China's most southern islands makes it ideal for space launches. And, most importantly, the Changzheng No.5 rocket's 5 meter diameter width makes it almost impossible to transport by land. 

"From the aspect of transportation, the 3 space centers we now have inland are not easy to reach through rail, road or air. The only choice remaining is to transport by sea, and therefore a new generation of launching centers need to be build around coastal areas," said Li Xiaohua, chief engineer of Beijing Special Engineering & Designing Academy.

But being based along the coast has its disadvantage as well, as the space center will face great challenge from the island's volatile weather, high temperatures, humidity and fog with high salt levels. These extreme weather conditions are the main difficulties that scientists have to solve before they decide on the location. Among these weather problems, is the notorious typhoon, which is a nightmare especially for space launches.

"We use a steel structure mix with steel reinforced concrete structures for our base, that will greatly enforce the strength in our buildings against typhoons and adverse weathers. For example our vertical assemble testing workshop, we use steel reinforced concrete with rectangle frame enforced structures. Also our launching frame, we use an all steel façade structure to cover the tower, while with steel reinforced concrete in the core, mixing elasticity with toughness against the weather," Li said.

In the detailed examination and review of the structure, the base showed great improvement on its ability to resist typhoon. It also meets the safety requirements for facing a once-in-a-hundred years typhoon. With advance radar technology applied to the center, most weather condition could be accurately forecast 3 days before it occurs, and 3 days is the maximum time a rocket will stay on the launching pad. A launch can begin within three days if favourable weather occurs.