I mentioned the Starlink satellite constellation to students in my after-school astronomy and space science club, and afterwards got into a discussion about space junk. I told the students that when I was their age, there were only a handful of man-made objects in Earth orbit. Today, there are thousands of objects in orbit – some useful, many not so much. Many satellites and space probes require multi-stage rockets to get them into orbit and/or to their destination. When a rocket stage is spent, it decouples – and continues in whatever orbit the vessel was currently in at that moment. If the vessel was in a sub-orbital trajectory, the spent stage either burns up, or is guided back to a safe landing – as has been known to happen. If the vessel was in orbit at the moment of decoupling, the spent stage remains in that orbit, becoming space debris. When a satellite or space probe has reached the end … Continue reading →