Why is NASA crashing planes on purpose?

Plane crashes are generally understood to be a bad thing, but NASA is now in the habit of crashing planes on purpose.

In an effort to build a better emergency alert system, a team at NASA's Langley Landing and Impact Research Facility outside Norfolk, Virginia recently dropped a Cessna 172 from 100 feet in the air.

The space agency's Facebook page described the situation:

"With a thunderous rattle, the aircraft plowed into the soil as its windshield shattered, its wings wrenched off and its fuselage flipped — tail over nose — onto its back. Researchers were pleased."

The planned plane crashes are tests developed to help improve the durability of on-board emergency locator transmitters, or ELTs, in the event of a general aviation accident.

See NASA's most Iconic photos:

ELTs are designed to activate within 50 seconds of a plane crash and then transmit coordinates of their position to a satellite. But, as anyone familiar with Malaysian Airlines Flight MH370—or J.J. Abrams' "Lost" for that matter—knows, ELTs don't always work as designed.

Researchers are using sensors to gather crash data and multiple cameras on and off the plane to determine how well five ELTs spread across the intentionally-downed aircraft hold up under severe conditions.

NASA's goal is to ultimately build a device that warns rescuers before a plane actually crashes.