NASA and SpaceX misjudged the risks from reentering space junk

Enlarge / A European ATV cargo freighter reenters the atmosphere over the Pacific Ocean in 2013.

Since the beginning of the year, landowners have discovered several pieces of space junk traced to missions supporting the International Space Station. On all of these occasions, engineers expected none of the disposable hardware would survive the scorching heat of reentry and make it to Earth's surface.

These incidents highlight an urgency for more research into what happens...