Last week, India intentionally destroyed one of its own satellites in orbit around Earth with a missile, resulting in a large field of space junk currently orbiting Earth.
NASA has called the act a “terrible, terrible thing” that has created an “unacceptable” threat to the crew currently aboard the International Space Station.
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In a town hall held yesterday, NASA Administrator Jim Bridenstine said that “… Intentionally creating orbital debris fields is not compatible with human spaceflight.”
(If the embedded video doesn’t queue up to the right spot, jump to 7:40.)
Bridenstine said that the direct ascent anti-satellite test resulted in 400 pieces of orbital debris from the single event – and this is only what’s been identified. He said that all these pieces cannot be tracked, though because they need to be ten centimeters (about 3.9 inches) or bigger in order to be tracked.
He also noted that the risk of small debris impact to the International Space Station went up 44% over a period of ten days. The good news is that this will eventually all fall back to Earth.
There was also a similar anti-satellite test conducted by China in 2007, and according to Bridenstine, most of the debris from that is still in LEO, and NASA tracks this and shares their data with other countries for free, courtesy of the US taxpayer’s money.
There are about 60 pieces that are bigger than ten centimeters. Of those 60, 24 pieces of debris are above the apogee (the point in which it is the farthest from Earth) International Space Station. What this means is there are at least 24 pieces of satellite debris that have a greater than zero chance of striking the International Space Station.
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So there’s some small chunks of metal floating around that might bump into the ISS. You might be asking – What’s the big deal?
The European Space Agency (ESA) has actually tested the effect of orbital debris impacts. ESA fired a 1.2 centimeter ball into a sheet of metal that was 18 centimeters thick at orbital velocity, which can be around 15 kilometers (9.3 miles) a second for space junk, or as high as 72 kilometers (44.7 miles) a second. (And no, 72 kilometers a second was not a typo.)
The results are, in a word, YIKES.
And keep in mind the above test was done with a 1.2 centimeter projectile. The chunks of dead satellite NASA is tracking consist of projectiles that are, at a minimum, about 8 times that size. So an impact with the ISS would make for a bad day in the office.
There are ways to mitigate this danger though, including putting a thin sheet of aluminum above the the main body of the craft. When a projectile impacts it, most of the kinetic energy turns into heat, essentially vaporizing the projectile and splattering it across the surface, leaving the craft undamaged.
Business Insider reported:
A software-engineering company called Analytical Graphics made a simulation of the debris created by the anti-satellite test, Business Insider’s Dave Mosher reported.
“We modeled 6,500 fragments, basically those that were larger than half a centimeter,” Tom Johnson, the vice president of engineering for Analytical Graphics, said.
Of course, India has done what it can to minimize the perceived risk of their incredibly irresponsible test, saying that all the debris should re-enter the Earth’s atmosphere and burn up within about a month and a half.
G. Satheesh Reddy, the chief of India’s Defence Research and Development Organisation, said a low-altitude military satellite was targeted with the goal of reducing the risk of debris.
“That’s why we did it at lower altitude — it will vanish in no time,” he told Reuters. “The debris is moving right now. How much debris, we are trying to work out, but our calculations are it should be dying down within 45 days.”
Acting US Defense Secretary Patrick Shanahan warned a day after India’s test that the event could create a “mess” in space.’ (Business Insider)
Another danger of tests like these, as Administrator Bridenstine pointed out in his town hall, is that other countries will feel as if they need to demonstrate their capability of removing a satellite from orbit, resulting in even more debris.
As of January 2019, there were about 5000 satellites in Low Earth Orbit (LEO). If a chunk of the destroyed satellite impacts any one of these 5000 satellites, it creates a new debris field, and increases the risk of a cascade effect where satellites keep getting destroyed, creating more and more debris.