Built by Lockheed Martin under a DARPA program, the Falcon Hypersonic Technology Vehicle 2 (HTV-2) is designed to attack any target on the Earth within 1 hour. It can reach speeds of Mach 20 and was to make a touch down on the Pacific Ocean 30 minutes after a 4,100 nautical-mile flight just last week.

The Falcon is a different type of weapon, it's equipped with high-power, but non-nuclear explosives that should remain undetected by nuclear defense systems. But everything didn't work out as planned. 'Preliminary review of data indicates the HTV-2 achieved controlled flight within the atmosphere at over Mach 20. Then contact with HTV-2 was lost,' said Johanna Spangenberg Jones, a spokeswoman for DARPA. Where did it go? Nobody knows yet ;)