As the ISS floats above earth, it's actually hurtling around its orbit at 17,000 mph. Any debris that it encounters at that speed could have major consequences, so the ISS often has to change course throughout its orbit just to avoid space debris from previous missions. According to NASA, there are about 3,000 tons of space debris in a cloud around Earth in low-Earth orbit. There is another belt of debris higher above the earth in geo-synchronous orbit. A team of Japanese scientists proposed a solution using lasers to blast the debris before it can damage the ISS.