Chinanews.com, Beijing, May 29th, title: "Changqi" expedition kicks off the second shot of the construction of the Chinese space station
Author Guo Chaokai Chen Jie
On the evening of May 29th, the Long March 7 Yaosan rocket was ignited and lifted off at the Wenchang Space Launch Site to accurately send the Tianzhou-2 cargo spacecraft into its intended orbit.
This mission is a crucial battle for the space station’s orbital construction phase. It started the second shot of the Chinese space station’s orbital construction and will send the first "visitor" to the Tianhe core module.
Why can the Long March 7 rocket become the "exclusive train" of the Tianzhou cargo spacecraft?
What secrets are hidden in its "body"?
The reporter interviewed aerospace experts to find out.
Launch site.
Photo by Luo Yunfei
Tianzhou "Exclusive Train"
The Long March 7 rocket is a new generation of medium-sized carrier rocket developed to meet the requirements of the Chinese Space Station project to launch a cargo spacecraft. Therefore, it is also affectionately called the "exclusive train" of the Tianzhou cargo spacecraft.
In April 2017, the Long March 7 Yao-2 rocket successfully sent China's first cargo spacecraft, Tianzhou-1, into the scheduled orbit.
Four years later, the Long March 7 rocket set off again, sending the Tianzhou-2 cargo spacecraft into space.
After that, Tianzhou-2 will dock with the Tianhe core module in orbit to complete the delivery of fuel and materials, laying a solid foundation for the subsequent launch of the manned spacecraft.
According to the space station’s orbit construction mission plan, China will implement 11 consecutive flight missions this year and next, including 3 space station module launches, 4 cargo spacecraft launches, and 4 manned spacecraft launches.
In this regard, Xu Lijie, commander and chief designer of the site 01 of the Long March 7 launch vehicle test team of the First Academy of China Aerospace Science and Technology Corporation, said: “11 missions in 2 years, interlocking, like a relay race. It will be related to the smooth implementation of the China Space Station construction plan. This mission is a key battle that links the previous and the next in the construction phase of the China Space Station project, affecting the hearts of hundreds of millions of people."
Launch site.
Photo by Luo Yunfei
From "zero window" to "narrow window"
This mission is the third launch of the Long March 7 carrier rocket, and it has been four years since the launch of the Long March 7 Yao-2.
During this period, the model team carried out a large number of optimized and improved designs, which not only realized the technological leap from "zero window" to "narrow window" launch, but also simplified and optimized the on-board measurement system and optimized the tank pressurization design. More than 130 improvements make the rocket more economical and reliable, and it is more conducive to mass production and high-density launch.
Xu Lijie said that although the Long March 7 rocket already has the "zero window" launch technology, in order to better adapt to the failure situation and improve the rocket's ability to launch on time, the model team has made efforts to finally expand the "zero window" accurate to the second to 2 A "narrow window" of about minutes.
In other words, if the deviation of the rocket's take-off time is within 2 minutes, the rocket can automatically correct the flight trajectory according to the take-off time, ensuring that the cargo spacecraft can still enter the orbital surface where the core module is located, and improving the adaptability of the Changqi rocket to launch tasks.
In addition, the researchers also changed the rocket boost and the first-stage tail end and the first-stage transition section from composite coating to ordinary coating; after the improvement, the construction process was simplified and the production cycle was shortened.
Taking the transition stage after the first stage of the rocket as an example, the improved production cycle has been shortened from about 18 days to 13 days, laying the foundation for subsequent mass production.
Launch site.
Photo by Guo Wenbin
Future Space Launch "Main Force"
The Long March 7 carrier rocket is the basic model of China's new generation of medium-sized carrier rockets. Based on the Long March 7 rocket, scientific researchers have derived the Long March 7A rocket with high orbit launch capabilities.
With the improvement of the technical solutions of the two types of rockets and the stable performance, the Long March VII series rockets can gradually replace the relevant models of China's active Long March carrier rockets and become the "main force" of China's future space launch missions, performing more major launch missions.
In addition to the 4 launch missions of the Tianzhou cargo spacecraft in two years, the Long March 7 launch vehicle will maintain its frequency of launches twice a year after entering the space station operation phase.
Launch site.
Photo by Guo Wenbin
In addition, the Long March VII carrier rocket has a low-Earth orbit carrying capacity of 14 tons. In terms of "strength", it is more than half than traditional fuel carrier rockets. Therefore, it can not only achieve the launch of large payloads, but also can be matched with upper stages or The second stage adopts multiple start-up technology to realize the launch of large payloads in sun-synchronous orbit or multi-satellite networking.
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