Joat42 wrote:Loren Pechtel wrote:However, I see a big problem with those backstops--they're in atmosphere. What happens to the air hitting it? If it's powerful enough to stop a bullet it's going to be imparting quite a velocity to the air that touches it. Where does that energy go? Why doesn't it melt whatever eventually stops it?
Well, it was something I wondered about too. Grav-fields in an atmosphere would create some really interesting effects.
You could of course place a low-G field pointing towards the shooter just before the real backstop. That would essentially create a zone with very low air-pressure or even a vacuum.
I considered that but it doesn't work. It's not gravity pushing the air against the backstop, but rather the ambient pressure caused by gravity pulling down on the air. If you're going to create a gravity field sufficient to repel that you need push as hard as the planet is pulling. If this is on Earth that means it's pushing something like 11 km/sec. (Note: Escape velocity is dependent on both surface gravity and density, they don't always move together.) Oops, your nice bullet-destroying backstop is now a perfect spring sending the bullets back at the shooters.