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Home / Science / Dealing with celestial waste-removing space junk | Science and Technology

Dealing with celestial waste-removing space junk | Science and Technology

Humans are messy. Wherever they go, they tend to leave the garbage behind and expect others to remove the garbage. This is true even in outer space. The problem of orbiting and the accompanying risk of collision with and damage to an active, possibly expensive artificial satellite has existed for some time. But it is rapidly deteriorating. In the past three years, the number of times this junk hits a satellite in operation has roughly doubled.

At least, this is a calculation made by expert Daniel Oltrogge, whose conclusions come from two of his work. Mr. Oltrogge is an advisor to the Space Data Association, which inputs orbital and maneuvering information from many satellite operators into a computer model that predicts possible collisions in order to protect spacecraft or at least spacecraft with appropriate thrusters from damage . the way. Mr. Oltrogge is also the director of the Space Standards and Innovation Center of the American company AGI, an American company that develops orbital mechanics software that also helps satellite operators avoid collisions.

Part of the problem is that more and more launches. For example, on January 1

3, Richard Branson’s Virgin Group company, Virgin Orbit, will use a modified Boeing 747-400 rocket Put ten satellites into orbit. But the other part is that every year, more than a dozen large pieces of debris orbiting the earth will decompose. About half of these explosions were caused by the remaining rocket fuel on fire, the explosion of old batteries and pressurized tanks, etc. The rest is the result of the collision.

The result is a chain reaction of orbital impacts. Unlike the fictional version of this chain reaction, the latter made the character of Sandra Bullock inconvenient in the 2013 movie “Gravity”, but this real progress is only slow So there are still time constraints. However, if action is not taken as soon as possible, satellite insurance premiums will increase, expenditures for tracking and collision avoidance systems will have to increase, and certain orbits may not be available. If the situation is really bad, the authorities may even have to step in to limit the number of launches.

Stopping this chain reaction that produces orbital garbage means that the excess tons in space are cast into the earth’s atmosphere, and the frictional heat entering it will burn it. No thorough scan is required. It is sufficient to remove a small amount of larger discards each year. How many people are arguing. Yamotomoto Toru of JAXA, the Japan Space Agency, estimates it will be between three and seven. Ted Muellerhaupt of American Aerospace Corporation, a research center funded by U.S. taxpayers, estimates there are a dozen. But it sounds feasible. Unless no one knows what to do.

People are planning exercises. Tokyo-based Astroscale led a practice mission, which is scheduled to take off in March. The telescope proposed to launch a mission named ELSA-d from the Baikonur space shuttle in Kazakhstan. This includes a 175kg mothership (called “attendant”) and a 17kg pod with an iron docking plate that will be used as a virtual target. If all goes well, the maintenance personnel will pop out and retract the pods three times in a continuous more difficult test run, and then the propeller will push the entire beancake into the atmosphere below until fiery bad luck.

In the first test, the maintenance personnel will use the spring to push the pod out, and then when the pod is ten meters away, they will approach the pod again, use the arm equipped with the magnetic head to lock it on the docking plate, and retract it. Arm and pull it back to the server. For the second test, it will be pushed to a position at least 100 meters away before starting to approach. Then, a reaction wheel and a set of electromagnetic torque generators put the pod into the drum involving all three axes of motion at a speed of half a degree per second.

In fact, this is an important turning point, because large pieces of orbital debris usually rotate in this way. Therefore, true orbiting missions will have to deal with such spinning objects. The markings on the pod will help the service staff determine the movement of the prey. Using eight thrusters, it will automatically maneuver until the marks appear stationary on its sensors. This will mean that its movement exactly matches the movement of the clamshell box, so the head can be expanded to complete its work.

For the third capture test, the service personnel will first use its thrusters to move it back a few kilometers from the pod so that the pod is beyond the sensor range. Then it will search for it as if it were looking for a real abandoned spacecraft.

For all technical capabilities, these tests will be required, but real obsolescence poses greater challenges than dummy. On the one hand, unlike Astroscale’s pods, few spacecraft are designed to speed up their own dismantling. In addition, the objects that need to be removed most are also dangerous. A spacecraft that tried to capture such a tumbling debris and miscalculated may be smashed into the blacksmith’s shop, thereby exacerbating the problem it was supposed to solve.

Hurry up
JAXA plans to orbit the abandoned Japanese rocket carrier for a commercial debris removal demonstration that highlights these difficulties. Before designing a spacecraft that can capture any abandoned Japan Space Agency as an experimental target, a reconnaissance mission must first be launched to study it at close range. JAXA has awarded Astroscale the contract for this part of the demonstration, and the company plans to use an airship called ADRAS-J for this work, which will be launched in two years. In order to measure the movement and characteristics of rocket parts that may weigh several tons, ADRAS-J will be close within a few meters. Once the necessary data is collected, another spacecraft can be designed to catch the garbage in subsequent missions.

In this case, magnets will not be used to grab the target because there is no iron in a normal spacecraft. However, it may be feasible to use a harpoon to catch such objects. In a test conducted in 2019, European aviation giant Airbus successfully shot a harpoon from a satellite into a panel 1.5 meters away. However, the panel is connected to a boom extending from the satellite, so this is only the most preliminary experiment. Moreover, the harpoon may miss, bounce or damage part of the target, thereby further destroying the celestial garbage dump.

Another option is to shoot the net. Airbus tested the idea in 2018. The test successfully wrapped a small “cube” that had been pushed seven meters away from the net-throwing boat, although the net was not tethered to the mothership, so it could not be removed from the orbital target. In fact, tethers are difficult to manage on a weightless track, which is why Airbus chose not to use tethers in this preliminary net casting test.Some people doubt this kind of universe retiree It is a wise idea. Chris Blackerby, chief operating officer of Astroscale, predicts that the best way is to design the robot arm so that it tightly grips the fairing of the target vehicle (connecting it to the projectile launch that lifts it from the earth). The shallow cylinder of the platform).

If all goes well, JAXA’s debris removal demonstration will face the final challenge. This is to perform safe re-entry. Many parts of the trapping agent and the re-entering of the trapping agent will undergo frictional melting and slamming, and quickly enter the surface of the earth. If you re-enter a random location, the likelihood of casualties will now exceed the one in 10,000 threshold set by NASA as an acceptable risk level in 1995, and will be adopted in Japan and other countries thereafter. Therefore, the complex will need to be lowered down steep steps to target an uninhabited area (possibly part of the Pacific Ocean).

Regarding the first removal of debris that is actually in orbit, this is likely a European matter, because in 2019, the European Space Agency signed a contract with the Swiss company ClearSpace to capture 100 kg of rocket debris that has been in circulation since 2013 It has been the earth since. This task is planned for 2025.

ClearSpace plans to use a trap equipped with four robotic arms. Unlike harpoon or net throwing, this strategy allows repeated attempts to recover. Even so, Luc Piguet, the owner of ClearSpace, predicts that his spacecraft will spend at least 9 months in the vicinity of the target for testing before it can be guaranteed to be abandoned and slow down enough to descend.

pay off!
The era of serious space cleaning is still far away. In addition to technical obstacles, the removal of garbage will be expensive. In addition to the cost of getting something into orbit, controlling the object’s re-entry requires close attention from fuel, large thrusters, and ground controllers. These things can add millions of dollars (perhaps more than 20 million dollars) to the price tag of a derailed business. For example, the ClearSpace mission may cost as much as 100 million euros ($122 million), although Pigut hopes future work will be cheaper.

However, whether it is cheap is still a question, “Who will pay?” Littering is an example of a textbook about the tragedy of the commons. The solution of one problem is in everyone’s interest, but no one is willing to shoulder the heavy responsibility of solving this problem alone.

Therefore, the solution to the tragedy of the commons must usually be proposed by outside the government. One idea is to impose a special launch tax and assume that the proceeds are used for clean-up operations. Mr. Muelhaupt refers to the more creative proposal as the “bottling system”. Astronauts will pay a deposit for each spacecraft they put into orbit. If the owner fails to get the equipment out of track after the task is over, the work can be done by someone else, who then collects the deposit. This will encourage people to build deorbiting capabilities into satellites from the very beginning, so ultimately there will be no need for dustmen in the sky. The third proposal made by Akhil Rao of Middlebury College in Vermont is to charge rent for each commercial satellite in orbit, which is called an “orbit usage fee.” That will have the same effect.

Support for such plans is growing, although they require both international agreements between countries that have launch facilities and an enforcement mechanism to prevent outsiders with looser rules from weakening such arrangements.

Another point. Just as Jean-Daniel Testé was once the head of the French Air Force Joint Space Command, he pointed out that equipment developed to clear the orbit can also be used to disable satellites. Mr. Testé said that France’s enemies have made progress in orbital robotics, not to mention the lack of any international “space gendarmerie”, which is prompting his country to plan spacecraft to defend its military and intelligence satellites.

Mr. Testé is shy in details. But the French Armed Forces Minister Florence Parly (Florence Parly) revealed more information about the French plan, while its plans by other major powers, including the United States, did not. She foresaw that France would launch special “surveillance” and “active defense” spacecraft to protect its space assets. The latter may be equipped with powerful lasers. As Ms. Parry said, “We intend to blind” the spacecraft. It is preferable not to disintegrate.

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