The orbital mechanics in Gravity is simply wrong. "340-360 km is reserved for polar orbits" Consider a perfect polar orbit. At time 0, one satellite is above

The orbital mechanics in Gravity is simply wrong. "340-360 km is reserved for polar orbits" Consider a perfect polar orbit. At time 0, one satellite is above Yamagata heading due north , Japan and another is above Louisville, Kentucky, US also heading due north. These two satellites are on a (possible) collision course directly above the north pole, because all polar orbits go above the poles. "Lanes" wouldn't work because of orbital decay. For example, the HST is ~550 km altitude. That's close enough that natural atmospheric reentry would happen in about 20 years. If that were to occur, it would descend through the lower 'lanes'. Rather, it would only work if every satellite had active station keeping, had an active method to quickly deorbit, never failed, and never blew up (as DMSP-F13 is believed to have exploded due to a battery charging system - http://www.space.com/29996-us-military-satellite-explosion-dmspf13-cause.html http://www.space.com/29996-us-military-satellite-explosion-d... ). But if those assumptions are assumed, then we wouldn't have collisions in the first place.