Originally Posted by Lt.JD
If it reaches the ocean intact at that speed it would be liking hitting the ground.
I was shooting with a varmiter and he was telling me a story about shooting his 220 swift (4200 feet per second muzzle velocity) out in very light mist rain. He wasn't getting any hits and he finally figured out the bullets were exploding on the rain drops. And this was only 200 yards. Not 500 or 600 yards. He found fragments in the target so the bullets were almost making it sometimes. And this was less than a mile per second.
People don't even realize that mach 20 is not possible at anything under nosebleed altitudes. There's too much air and if it passed through a high pressure center followed by a low pressure center followed by a high pressure center it would rip it apart. This is probably going to happen at 70 thousand feet with no air to speak of anyway.
Plus you have a size factor. For instance if you drop a mouse down a 1000 foot mine shaft it scurries off. If you drop a small cat it breaks a leg or 2 and suffers some internal injury. Possibly dying depending on the landing. If you drop a person they bounce. If you drop a horse they splash.
Any large object at those speeds pretty much turns to fragments and gasses on any meaningful impact as they are nearly liquid gaseous temperatures anyway depending on the drag and cooling.