In space, what goes up doesn't necessarily come down. Or at least, not for many years. Anything launched above 620 miles will usually stay in orbit for a century or more. Designing satellites to re-enter the atmosphere at the end of their active life could therefore be a viable option for reducing the buildup of non-functional debris.

This isn't without its complications. While most objects that re-enter the atmosphere will burn up high above our heads, some objects can survive the heat of re-entry and can pose a risk to humans. For example, take this 150-pound titanium motor from a Delta II third stage, which landed in Saudi Arabia in 2001. The chance of falling debris causing a casualty is less than one in 10,000, since most land in the ocean or uninhabited regions. But since NASA and ESA can be held liable for damage, they'll likely be wary of any strategy that would increase re-entry rates.