NASA uses a ‘gun’ that shoots aluminium ball-bearings at thousands of kilometres per hour, to test the impact of space junk against shuttle casings. How does it work?
The gun’s mechanism is simple but effective. A piston is driven into a compression chamber by 1.8 kilograms (four pounds) of gunpowder, which squeezes the hydrogen inside to 7,000 kilograms-force per square centimetre (100,000 pounds-force per square inch).
This propels the aluminium sphere in a plastic sabot down the barrel. A steel stripper rips the shell off and the sphere enters the target tank (with air pumped out to replicate the vacuum of space) and hits the target. A digital camera that captures 100 million frames a second records the impact to the nanosecond.