Too advanced to be shown! What exactly is the much-anticipated "reusable spacecraft"?

"Repeatability" is an important way to reduce the cost of space launches, and related technologies have undergone a long period of exploration. In the foreseeable future, we may be able to witness China's space shuttle rushing into space.

Written by reporter Duan Ran****Edited by Ding LinNew Media Editor Wang Shan <br /> Recently, while all space enthusiasts were focusing on the stunning debut of the Tianzhou-6 cargo spacecraft, a small spacecraft called a "reusable test spacecraft" quietly returned to the ground. It is reported that this type of spacecraft was launched by the Long March 2F carrier rocket and successfully returned after 276 days of in-orbit flight.

From the brief text reports, many space enthusiasts associate the X-37B and a series of "space plane" concept designs of the United States, and further extend them to the infinite imagination of future space travel. However, most people are full of doubts about the concept of "reusable spacecraft". What is the difference between this and the manned spacecraft and space shuttle we are familiar with?

High cost of space launches

The mission of manned space flight is not only to send astronauts to space smoothly, but also to send them back to the ground safely after the mission is completed. So far, except for the US space shuttle and some new spacecraft that are still under testing, most of the spacecraft in service are disposable vehicles. They still continue the characteristics of Gagarin's spacecraft: the spacecraft is declared scrapped after a mission is completed. After sending the astronauts back to the ground safely, most of the parts can only be burned during re-entry into the atmosphere, and the only recyclable return capsule can only be used as an exhibit for people to visit at most. This brings a serious problem: since the spacecraft cannot be reused after the mission is completed, a new spacecraft must be manufactured every time a manned space mission is carried out. The resulting launch cost is extremely high, which also greatly affects the efficiency of manned space missions. The high cost and cumbersome procedures have prompted people to seek new vehicle solutions. Thus, the concept of "reusable spacecraft" began to take shape. As early as the 1960s, the National Aeronautics and Space Administration (NASA) began to demonstrate multiple reusable spacecraft programs, and eventually the "Space Transportation System" program was funded. This program, which integrated the aircraft launch layout design, later developed into the familiar "space shuttle" - it takes off like a rocket and lands like an airplane.

▲In 2007, the Space Shuttle Discovery carried out the STS-120 launch mission (Photo source: NASA)

Compared with conventional manned spacecraft, the advantages of the space shuttle are huge: the main vehicle of the International Space Station, the fourth-generation "Soyuz" spacecraft MS type, can only carry a maximum of 3 members or limited cargo at a time, and an average launch frequency of 3.5 times a year can meet the transportation needs of the International Space Station. The space shuttle can send 7 astronauts into orbit at a time, and the huge cargo compartment gives it huge transportation capacity. The most important thing is: the space shuttle can be launched and put into use again. For example, the "Discovery" space shuttle has been launched 39 times in its 27-year service career, transporting 252 astronauts, showing super high efficiency in front of traditional manned spacecraft. Despite this, the space shuttle, as the first reusable spacecraft of mankind, eventually withdrew from the stage of history, and the transportation mission of the International Space Station is still undertaken by "old comrades" such as the Soyuz MS. What's going on? In fact, the problem is still the cost: all in all, the average space shuttle launch costs about $800 million, and the originally expected high attendance rate has not been achieved. Due to the complexity of maintenance work, the launch turnover cycle of the space shuttle is very long, and the shortest launch interval in history is as high as 54 days... Such expensive and slow spacecraft are gradually unable to keep up with the requirements of the times.

▲In 2008, the Atlantis space shuttle was pushed into the factory for maintenance after completing its launch mission (Photo source: scienceblogs.com)

The cheap and efficient Dragon spacecraft

Although the space shuttle is no longer popular, the development of reusable spacecraft is still regarded as the main way to solve the cost problem of space launch missions. In addition to developing the Falcon series of reusable launch vehicles to reduce launch costs, the Space Exploration Technologies Corporation (SpaceX) led by Elon Musk is also focusing on the development of a new generation of reusable spacecraft. In 2006, SpaceX launched the "Dragon" cargo spacecraft, which is designed based on the blunt cone ballistic capsule shape of traditional spacecraft. Although the cost of a single launch is more expensive than the "Soyuz", its cargo capacity is twice that of the latter. Moreover, since the space shuttle, the "Dragon" spacecraft has once again achieved the reuse of spacecraft, which is more conducive to further amortization of costs. After matching the "Falcon 9", the "Dragon" spacecraft has carried out 23 launches in 10 years, 18 of which were cargo missions to the International Space Station. In total, the launch cost of the "Dragon" spacecraft is less than one-tenth of that of the space shuttle.

▲In 2012, the "Dragon" cargo spacecraft carrying out the CRS-11 mission opened its huge solar panels (Photo credit: NASA)

On this basis, SpaceX launched a passenger version, the Dragon 2. The Dragon 2 can carry up to seven passengers at a time, which has reached the standard of the space shuttle at that time. In addition, the spacecraft is designed to be launched 10 times, which further amortizes the launch cost. If the cost saved by the recyclability of the Falcon 9 launch vehicle is taken into account, the average cost of carrying one astronaut on the Dragon 2 has dropped to more than 20 million US dollars. This cheap and efficient spacecraft makes regular flights between the ground and the space station possible in the future.

▲Dragon 2 docking with the International Space Station in 2019 (Photo credit: NASA)

The "Dragon" spacecraft is an epoch-making aerospace product, but its own limitations cannot be ignored. After all, its design is derived from traditional manned spacecraft, and a launch pad is required for launch, and the requirements for the launch site and weather are still high. Moreover, after re-entering the atmosphere at the end of the mission, this type of spacecraft has no maneuverability. Therefore, it is necessary to dispatch search and rescue personnel on the ground to the estimated landing site for recovery, and the manpower and material costs behind this are not small. Moreover, in the space travel that people imagine, I am afraid no one wants to see every return to the ground become a search and rescue site.

China is taking action on space planes

The idea of ​​incorporating the design of an airplane into a spacecraft has never disappeared. If a spacecraft can take off and land like a passenger plane, then future space travel will be as convenient as an ordinary flight. As a result, another form of reusable spacecraft, the space plane, emerged. This spacecraft combines the characteristics of an airplane and a manned spacecraft. On the basis of being reusable, it can achieve the same take-off and landing as an ordinary airplane. In fact, the space shuttle can be regarded as an "incomplete state" of the concept of the space plane - it can only be launched vertically in the traditional way during the launch phase. The difficulty in the development of the space plane lies here: how does the aircraft enter space? The ideal space plane is of course to take off normally, without the help of external rocket boosters to ascend into space. However, given the limitations of today's aerospace technology, the space planes currently being tested by various countries are still boosted by rockets. For example, NASA's "Dream Chaser" micro space shuttle and the X-37B spacecraft.

▲The X-37B spacecraft successfully completed an unmanned in-orbit flight in 2010 (Image source: NASA)

Of course, people are also trying a new compromise plan: a two-section space plane. That is, a large aircraft-shaped vehicle carries the space plane to a certain height and then releases it, and then lets it fly into orbit autonomously. A similar plan has been tested by the United States with the "White Knight". This jet-powered carrier aircraft has launched a spacecraft called "Spaceship 1" at high altitude. Although it did not fly in orbit, it has opened up a new idea for the future of space planes. As a rising aerospace power, my country has also made great achievements in the research and development of reusable spacecraft and has gradually become a world leader. In 2018, CCTV disclosed a model of a two-section space plane plan in my country. In the aerospace science and technology exhibition hall of the 2021 Zhuhai Air Show, the model of the spacecraft named "Tengyun Project" has attracted great attention. From the appearance, this is still a two-section space plane plan. According to reports, this commercial spacecraft is a new generation of earth-to-earth round-trip aircraft that can perform multiple space launch missions, and is expected to complete a technical verification flight in 2025.

▲During the 2021 Zhuhai Air Show, the China Aviation Science and Industry Corporation publicly displayed the "Tengyun Project" aerospace aircraft model (Photo source: NetEase Military)

The "reusable test spacecraft" officially announced this time was actually launched as early as 2020, and successfully returned after two days of in-orbit flight. According to official information, this spacecraft may be a design similar to an aerospace plane. This time, the spacecraft has been in orbit for 276 days, which shows that the technology is relatively mature. Although the official news is only a few words, it can be imagined that in the new track of "reusable spacecraft", Chinese astronauts are gradually exerting their strength and beginning to bear fruit. Perhaps in the foreseeable future, we will be able to see with our own eyes the Chinese aerospace plane piercing the sky and rushing into the universe.

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Produced by: Beijing Science and Technology News | Beijing Science and Technology Media

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