Planetary Resources is a company speaking publicly about mining near Earth asteroids for resources. I'm interested the physicality of a claim they make in a video here:
They would like a method to reenter resources into the Earth's atmosphere that is more economic than conventional approaches, and they propose making a metal foam that is super low average density. In particular, they propose turning 100kg of Platinum into a 2m diameter ball. They mention that the terminal velocity of this (presumably at sea level) is <60 mph. Then this would ideally avoid the problems that:
- low masses get burned up in the atmosphere on reentry
- high masses slam into the Earth's surface
This doesn't make intuitive sense to me. Sure, the drag coefficient is high and the mass is low, but that doesn't change the fact that you have to dissipate orbital kinetic energy over a finite distance. How would this avoid the problem of melting due to the heat and thus breaking up in the atmosphere?
If a higher drag to mass ratio was a panacea, then wouldn't we just use parachutes for reentry, even in the initial stages?
meta note: if it proceeds to beta, I may request to migrate this question to http://area51.stackexchange.com/proposals/43283/space-exploration-and-technology