Even with the world's most powerful computers, there's only so much the brains of the U.S. military can learn about flying at 20 times the speed of sound — 13,000 mph — outside of a real test. That happens today, when the Falcon HTV-2 launches. UPDATE: Anyone seen a hot arrow-shaped plane?

Designed by the Defense Advanced Research Projects Agency, the rocket-launched Falcon HTV-2 in theory could carry a payload to any target on Earth in under an hour. In practice, DARPA still has to answer many questions, like what happens to the craft's skin under 3,400-degree Fahrenheit cruising temperatures, and why did the previous test end with a "flight anomaly" that triggered the craft's self-protection measures to send it plunging into the ocean.

After launching from Vandenberg AFB, Calif., aboard an Air Force Minotaur IV rocket sometime this morning, the Falcon HTV-2 will hit speeds of 13,000 mph — enough to travel from New York to Los Angeles in 12 minutes. If all goes to plan, sensors on board and earth-bound monitors will watch the Falcon's maneuvers for a 30-minute flight before another ocean landing. If its successful, the world may become a slightly smaller place.

UPDATE: Well, that's not good. DARPA reports that as it entered its glide path, the tracking systems lost contact with the HTV-2, and the downrange sensors didn't find it, either. There's either an expensive piece of equipment floating somewhere in the Pacific, or the Falcon has joined the heavens permanently.