Even if you don’t know what you are looking at, this video is intriguing:

So what are we looking at? It is the Multiple Kill Vehicle. It is a kinetic weapon designed to slam itself into an incoming warhead. The MKVs are bundled together and work in groups, as described here:

Multiple Kill Vehicle Completes Hover Test

From the article:

The MKV-L mission is to destroy medium through intercontinental-range ballistic missiles equipped with multiple warheads or countermeasures by using a single interceptor missile. During an actual hostile ballistic missile attack, the carrier vehicle with its cargo of small kill vehicles will maneuver into the path of an enemy missile. Using tracking data from the Ballistic Missile Defense System and its own seeker, the carrier vehicle will dispense and guide the kill vehicles to destroy any warheads or countermeasures.

This video shows different applications of the MKV: