China’s prototype space station has reportedly lost control, and it is on a collision course with Earth. The website Satview has been tracking the space station, and reentry is estimated for Tuesday, April 3rd at 7:37 UTC. The website displays two tracking maps. One shows Tiangong-1’s current path on a global scale, while the other displays a closer view of the object’s current position.
Tiangong-1 measures 10.4 meters long and weighed a total of 8.5 tonnes, including fuel, at launch. Despite its large size, it is highly unlikely to cause any significant damage. As with other falling space objects, Tiangong-1 will burn once it hits Earth’s atmosphere. A small amount of debris may remain, though the risk of being hit by falling space debris is extremely small. In fact, according to the Aerospace Corporation, the odds of being hit by debris are “1mil times smaller than odds of winning Powerball jackpot – even if you live in ‘high risk’ areas.”
However, officials have stated that it is currently unclear where specifically the object will land. The Aerospace Corporation estimates that impact will occur on April 1st, while the European Space Agency predicts it will occur anywhere from March 30th to April 6th.
While pinpointing re-entry is typically much easier, this situation is a bit more complicated. Circling Earth at a height of approximately 250 miles requires a speed of 17,500 mph, resulting in a complete orbit every 90 minutes. This makes estimates tricky. At that height, the outer fringes of Earth’s atmosphere drag on spacecraft, causing it to eventually slow down and plummet toward Earth if it is unable to speed up and correct its orbit.
According to orbital-mechanics engineer Jesse Gossner, aerodynamic forces start having an effect at approximately 100 kilometers. “Above 100 kilometers, it’s a lot, lot, lot thinner than down here, and you certainly wouldn’t be able to survive,” he said. “But it’s thick enough to slow you down.”
Gossner likened Tiangong-1 to a stone skipping on water. “This thing can bounce off the atmosphere because it’s going so fast. If it hits on its smooth side, sort of like a rock skipping on a lake, it’ll bounce. But if it hits on a pointy end or on one end of a cylinder, in the direction of the velocity, it could dig in.”
Gossner also stated that once the spacecraft reaches an altitude of 80 miles, it will be approximately 90 minutes away from crashing. However, even knowing where in the atmosphere it hits is not enough to determine where exactly impact will occur, as the debris can spread across a fairly large area. “It’s really just a guessing game.”
However, considering the fact that 71 per cent of Earth’s surface is comprised of water, there is a high probability that Tiangong-1 will make an ocean landing. Typically, space agencies attempt to de-orbit spacecrafts so that they land in what is known as the Pacific Ocean Graveyard, or Spacecraft Cemetery. This area of the Pacific Ocean lies 3,000 miles off the Eastern coast of New Zealand and is over 2 miles deep. Since 1971, over 263 spacecrafts from 4 nations have crash landed here. However, only the largest make it that far, as smaller spacecrafts burn up before reaching the surface.
Although the likelihood of any space debris causing damage or harming people is extremely low, such an occurrence would be covered as outlined in international space law, with liability falling on the government agency to which the spacecraft belongs. “It’s China’s responsibility if someone gets hurt or property gets damaged by this,” said a NASA representative.