On September 18, 2019,
the Taurus nano-satellite,
which has entered orbit for less than a week with CZ-4B launch vehicle,
successfully deployed its deorbiting sail to initiate a passive deorbiting test.
The camera successfully captured
and transmitted back the pictures of the deorbiting sail during deployment.

▲Picture of the Deorbiting Sail of Taurus Nano-satellite during Deployment

A:Wait a minute…? Deorbit? Say goodbye to space in less than a week after injection?

B:Well...you may not believe it, but the story of this satellite has to start with garbage sorting.

In our daily life, the means for clearing and disposal of garbage are progressing unceasingly. For example, Shanghai has been experimenting with garbage sorting for more than two months.

It is not easy to dispose of the garbage on the ground, let alone the garbage in space. The Taurus nano-satellite has a strong self-awareness: “Begin with me to protect the space environment.”

▲Taurus Nano-satellite

Since the first man-made satellite was launched by the Soviet Union, more than 4,000 space launch missions have been carried out in the world, with more than 8,000 spacecraft involved. At present, there are about 1,500 satellites in orbit. The spacecraft that have failed, as well as the final stages of rockets, operational debris from initiating explosive devices, spacecraft debris, and so on, are mostly wandering in low-earth orbits below 1000 kilometers. In the event of a “scratch”, more space debris will be created. Now there are more than 50,000 derelict spacecraft and space debris on record near the earth.

Never underestimate the dangers of space junk. They fly so fast that they can wreak havoc on a spacecraft. A 10-g piece of space debris is enough to penetrate or even destroy a spacecraft, thus producing more debris. The disaster arising from such chain reaction is depicted in the movie Gravity.

In reality, space junk has posed a threat to in-orbit spacecraft. The most typical case is the crash between “Iridium 33”of the United State and the scrapped “Cosmos-2251” of the Soviet Union at a height of nearly 800 kilometers above Siberia. The crash not only directly resulted in the “death” of Iridium 33, but also produced a large number of debris which scattered from a few hundred kilometers to more than a thousand kilometers in space and has had a great impact on subsequent space programs.

To prevent the rapid “reproduction” of space junk in a vicious circle, it is necessary to control the source of its production. How to prevent dark satellites from becoming space junk, and especially how to make LEO satellites with the largest number re-enter the atmosphere for destruction without polluting the resources of low earth orbit, has become the focus of aerospace studies.

The typical deorbiting mode of spacecraft is divided into active mode and passive mode.In the active deorbiting mode, the spacecraft conducts orbital maneuver using its own power device at the end of its life, so as to reduce the speed of flight, leave the orbit, and gradually fall into the atmosphere. On July 19, 2019, Tiangong-2 space laboratory was controlled to deorbit and re-enter the atmosphere for ablation and decomposition, and a small amount of debris fell into the expected safe waters of the South Pacific. This is a successful case of active deorbiting.

▲Reentering and Return of Tiangong-2 into the Atmosphere (Drawn by Lu Yue)

In the passive deorbiting mode, the flight orbit of the spacecraft is lowered by means of membrane sail device, electric tether, inflatable ball and other external forces. According to the designers of CASC, among all kinds of technologies, the membrane deorbiting sail has advantages of low technical difficulty, low cost and high maturity, and is suitable for different types of spacecraft with different orbits and specifications, so it is most promising for industrial application.

The Taurus nano-satelliteis equipped with a deorbiting sail load based on membrane mechanism technology in order to verify the high-efficiency folding and in-orbit deployment technology of the membrane deorbiting sail, and to measure the deorbiting effect. The area of the deorbiting sail is 2.25 m² when deployed, and is as small as a golf ball when folded. It is arranged in the internal void part of the satellite-rocket separation mechanism.

According to designers, the device adopts the advanced micron-size membrane folding technology, and the deployment/folding ratio reaches the world class level. The device can be added to all kinds of mature small satellite platforms without occupying the envelope of the satellite itself. After a satellite’s service life is over, it only needs to start the sail membrane unlocking command for deployment. The membrane sail will increase the windward area of the satellite and make use of the aerodynamic resistance formed by the thin atmosphere on the orbit to slow down the satellite slowly and make it gradually leave the orbit.

▲Effect picture of deorbiting saildeployed in orbit

Taking a small satellite with an orbit altitude of 750 km and a weight of 15 kg as an example, it can continue to operate in orbit for nearly one hundred years after the end of its service life if no deorbiting measures are taken. The use of the 2.25 m² membrane deorbiting sail can reduce the deorbiting time of satellites to less than a tenth of the original. For satellites of different orbital altitudes and masses, the design team is developing a standard series of deorbiting sail products to meet different deorbiting requirements.

According to the pictures of the Taurus nano-satellite transmitted back, the membrane deorbiting sail is normally deployed in orbit, and the telemetry data shows that the satellite is in good condition and stable attitude.

▲Animation for Operation of the Deorbiting Sail

There is no need to regret its hasty farewell. The ephemeral existence of the satellite ends up with an impressive outcome. This is its mission

Source: Science and Technology Daily