2023-05-07 04:40:28
What future does the space station have at the end of its lifespan?
- reporter, Jonathan O’Callaghan
- reporter, BBC Future
Deorbiting the International Space Station, the size of a soccer field and heavier than 200 elephants, is a monumental challenge. What future does the space station have at the end of its lifespan?
If you’re drifting in the wrong place in the Pacific eight years from now, you might be in for a shock. About 400 tons of metal will cut through the sky above you and become a ball of fire as it re-enters the atmosphere. And this fiery ball, burning fiercely, will fall into the vast sea, marking the end of one of humanity’s greatest projects, the International Space Station (ISS).
Since construction began in 1998, the ISS is still orbiting the Earth. The first crew arrived at the ISS in November 2000, and so far more than 250 people from 20 countries have visited it. “The International Space Station has been a huge success,” said Joseph Ashwacher, director of the European Space Agency (ESA). More than a dozen partners have participated in the ISS construction program, ESA being one of them. The ISS created in this way has been of great help to the international cooperative relations of various countries, as well as the United States and Russia, which had a cooperative relationship immediately following the collapse of the Soviet Union. “The space station is one of the truly large-scale international achievements,” said Thomas Zurbuchen, who served as NASA’s director of science missions.
But as the decades pass, much of the space station’s hardware is either outdated or out of control in orbit. Perhaps the fate of the Soviet Salyut 7 in 1985, when two cosmonauts tried to repair a crashed station, might repeat itself. “I don’t want to go through that once more,” said Cathy Lewis, a space historian at the US National Air and Space Museum.
The ISS side plans to de-orbit the station in 2031 and safely drop it into the Pacific Ocean through the atmosphere to prevent such a space catastrophe from happening once more. It is expected to be the largest atmospheric re-entry in history. In March, NASA asked Congress to help develop an interorbital transporter (a spacecraft capable of pushing a space station back into the atmosphere) needed for this task. Cathy Lloyders, director of NASA’s manned spaceflight program, said an interorbital vehicle is estimated to cost just under $1 billion.
De-orbiting the ISS precisely is a very difficult task. Russia’s ‘Mir’ space station in 2001 and NASA’s ‘Skylab’ space station in 1979 burned up in Earth’s atmosphere. However, ISS is more than three times larger than Mir, which might be problematic. “This is a significant challenge,” said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “I wouldn’t be happy to see a 400-ton object fall from the sky.”
The ISS project began in 1998 with the launch of the Russian-made Zarya module. Currently, it consists of 16 modules, huge solar panels mounted on metal trusses (a structural structure in which the joints are connected with pins so that the members do not bend), and radiators that dissipate heat. At 109 meters long, the size of a football field, it is the largest man-made structure ever assembled in space. “The space station is like the pyramids in Giza, Egypt,” said Laura Pokzik, a space analyst at the American consulting firm ‘Astraritical’. Currently, 7 crew members are stationed in shifts.
The ISS has extended its life several times over the years. However, the consensus is that extending life beyond 2030 is risky. Alternatives, such as pushing the ISS into higher orbit, are less realistic, according to NASA. Dozens of spacecraft are needed to push the station to a safe altitude. That’s why NASA laid out a plan to push the entire station back into the atmosphere in his report last year.
The International Space Station orbits the Earth at a speed of 27,570 km/h and experiences 16 sunrises and sunsets in a 24-hour cycle.
The orbit of the ISS, which was 400 km, will naturally collapse due to atmospheric drag from 2026, and will fall to regarding 320 km (200 miles) by the middle of 2030. At this point, the last crew member will go to the station to check if there are any equipment or items of historical significance that have not yet been removed, and the station will also be weighed down. However, Asbacher said, “It is still under discussion.”
When the last crew member leaves the ISS, the altitude drops to 280 km due to the drag of the Earth’s thick atmosphere. The altitude is considered a point of no return from which the station can no longer be pulled up once more. This process will take several months. Once the orbit has dropped to this point, the ‘Russian Progress Spacecraft’ will perform the final task of pushing the station back into Earth’s atmosphere.
However, problems have recently been discovered with some Progress spacecraft, and the political situation with Russia has deteriorated. So NASA is considering an interorbital transport as an alternative. “NASA doesn’t want to pin its hopes on Russian involvement,” said Wendy Whitman Cobb, a space policy expert at the Air Force’s Advanced Aerospace Research Institute. Russia has said it may withdraw from the ISS as early as 2025.
Whichever spacecraft is used, the station drops to an altitude of 120 km following this final push. And from this point, it will re-enter the thick atmosphere of the earth at a speed of regarding 29,000 km per hour. During this process, the solar panels will first fall off the structure. “The headwinds are going to be incredibly strong,” McDowell said. According to Mir’s re-entry case study, structure disengagement will occur at an altitude of approximately 100 km. It will take just a few minutes for the panels to all fall off. Then, at regarding 80 km above the surface, the modules themselves will begin to separate from each other and melt due to the thousands of degrees of heat generated during reentry. And the debris from this time will fall across the sky, making several roars.
In the past, Mir’s departure from orbit was a spectacle for viewers around the world. But the ISS is nearly three times larger than the 140-ton Mir space station. So the re-entry of the ISS would be even more spectacular. “Now we have a 400-ton reserve fireball flying through the atmosphere at orbital speed,” McDowell said.
If all goes according to plan, there will be no loss of life caused by this burning wreckage.
During re-entry, unmelted ISS equipment falls into ‘Point Nemo’, a vast area of the Pacific Ocean between New Zealand and South America often used as a spacecraft graveyard. This area is far enough from human habitation to safely dump space equipment. In addition, due to the nature of ocean currents, nutrients are relatively scarce, and marine organisms rarely live there.
Nevertheless, the path that the wreckage of the ISS reaches is several kilometers in width and length, and is expected to be up to 6,000 kilometers, which is expected to show an unprecedented scale.
Therefore, access to this part of the Pacific Ocean should be restricted upon reentry of the ISS to prevent loss of life. “It is still unknown how the planes and ships will be managed,” said McDowell. “But for those who witness it, the end of the ISS will be a spectacular sight.” ” he said. He said, “Scientific investigations must be made to be sure.” The entire re-entry, from the initial separation of the solar panels to the fall on Point Nemo, would be over in regarding 40 minutes.
While an impressive sight, some are concerned that the ISS’s departure from orbit is a waste of resources. This is because the ISS has spent a lot of money sending valuable equipment and useful resources such as truss metal and solar panels into space. “These are sunk costs,” said John Klein, a space policy expert at George Washington University in the US. “What we can reuse, we should reuse.”
End-of-life satellites and many unmanned spacecraft leave orbit and burn up in the atmosphere, but some debris still falls to Earth.
At the end of 2022, several companies, including the US’Sysruna Industries’ and’Astroscale’, presented these reuse ideas to the White House. Some of the space station truss metal might be melted down and used to create new structures or vehicles in space, or the entire module might be removed and repurposed for another space station. “We definitely think there’s an opportunity here,” said Gary Calnon, CEO of SeaSluna. “We want to build a scrapyard in space.”
A NASA spokesperson said while “we welcome suggestions for new and innovative ideas,” NASA “has not requested or received any proposals for repurposing any of the ISS’s major structural components.” On the other hand, Astroscale US President Ron Lopez wants NASA to reconsider the matter. “I hope I get a chance to think regarding all these options,” he said.
For the time being, the plan to drop the entire ISS into the Pacific Ocean will be in effect. This is the dramatic end to decades of human ingenuity and collaboration in space. If you end up drifting across the Pacific in 2031, you’ll have to be careful. This is because you can see hot debris from melting in the sky pouring down from space to Earth. “It will be a spectacular spectacle that can be seen through the media,” McDowell said. “It will be a fireworks display that you cannot miss.”
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