Double Asteroid Redirection Test mission

The Double Asteroid Redirection Test (DART) mission is a NASA-led space mission that aims to demonstrate a technique that will prevent an asteroid from hitting and damaging the Earth. It is expected to be launched next month aboard a SpaceX Falcon 9 rocket to a near-Earth asteroid system called (65803) Didymos.
The asteroid – (65803) Didymos – is larger than average-sized asteroid orbited by a 160-meter-wide moonlet. The DART is expected to crash into the moonlet at 6.6 km per second. This collision is expected to change the speed of the moonlet in its orbit around the main body by a fraction of one per cent. However, this will change the orbital period of the moonlet by several minutes.