In the next sentence the author also says the damage was caused by foam "hitting the wing nine times faster than a fired bullet." A bullet goes about 900m/s, an

In the next sentence the author also says the damage was caused by foam "hitting the wing nine times faster than a fired bullet." A bullet goes about 900m/s, and the "nine times" figure often symbolizes orbital velocity. It's clear that the reference is to the speed of the collision.