Recently, a landmark event has occurred in space - the Mainland Practice 21 satellite (referred to as the Practice 21 satellite) dragged an invalid Beidou navigation satellite from the crowded geosynchronous orbit to the spacecraft's sparse higher orbit, which marked the successful implementation of the spacecraft's passive displacement and the successful implementation of a new way of space garbage disposal.
On January 26, 2022, Brian Flaeherlin, chief architect of space situational awareness (SSA) of the American Commercial Space Monitoring Corporation, reported the space event from their observation at a webinar hosted by the Center for Strategic and International Studies (CSIS), a US think tank, arguing that the mainland's SJ-21 satellite (Practice XXI) seems to have just played the role of a "space tugboat". On January 22, an invalid Beidou navigation satellite (Beidou-2 navigation satellite G2) was towed from the crowded geosynchronous orbit (GEO) upwards, from an altitude of 21,300 to 21,500 kilometers to an altitude of more than 36,300 kilometers, with an elevation of 15,000 kilometers, sending it into the high-altitude "cemetery orbit" where there are very few satellites.
Schematic of orbital lifting
The Practice 21 satellite was launched on October 24, 2021, when some foreign experts believed that the satellite was not simple, not directly serving ground functional facilities, but clearing the space orbit and protecting the operating satellite. At that time, the mainland claimed that it was a technology verification satellite, mainly to verify the space debris mitigation technology, to put it bluntly, it was a technology that changed the orbit and speed of space debris or spacecraft, but at that time, most people thought that the practice of the Twenty-first satellite might only reduce the orbit and speed of the spacecraft, and did not expect that it could also lift the spacecraft to a higher orbit, throw the scrapped satellite outside the earth, not throw it inward, but throw it outside!
Shijian-21 satellite carries dozens of engines (responsible for attitude adjustment and propulsion), has two technologies of traditional fuel propulsion and electric propulsion, of which electric propulsion technology is very fuel-efficient, it can accurately locate and freely change orbit, has the ability to rendezvous with non-cooperative targets, can freely change orbit to a very close contact with the target want to capture, this orbit will have a brief close coincidence with the target, so it can be very close to the target, it comes with a set of space debris cleaning equipment, the previous simulation animation shows that it is a big net, It is to capture the spacecraft or space scrap in the form of casting a net, and then start the engine to move toward the target orbit.
So why did the mainland let the Shijian-21 satellite carry out such an operation? In addition to the technical verification significance, it may also be to let the "Beidou-2 G2" satellite free up its orbit, because the orbital resources it is in are very valuable, and since this navigation satellite has failed, then we can arrange more advanced Beidou navigation satellites in this orbit to better improve our Beidou satellite navigation system.
The implementation of satellite 21 was also very admired by the Americans, and Flaehern said that "this is a fairly responsible move by China... I hope that other countries will also consider removing large debris from the Geosynchronous Orbit Protected Area. However, because the mainland chose to implement this "space tugboat" technology in the United States during the day, although it is curious, the ground observation equipment is difficult to observe due to the strong sunlight, so the specific process is not very clear to the United States.
Practice 21 satellite can rise from 20,000 kilometers of space orbit to more than 36,000 kilometers of space orbit, the elevation of 15,000 kilometers, and relatively speaking, landing is easier, just slow down to land, and also more fuel-saving, so it is speculated that this satellite can also come to hundreds of kilometers high low Earth orbit, basically can cross the space unimpeded, if there is any more starlink satellite close to the continental space station, The U.S. USA-271 spy satellite is close to the mainland Practice-20 and other acts, and Practice 21 can also act as a "knife guard".
Resources:
"Global Network" January 27, 2022 article "US media hype: Chinese satellites become "space tugboats", dragging a failed satellite away from geosynchronous orbit"
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