Today, the U.S. Military’s Defense Advanced Research Projects Agency (DARPA) will conduct the second-ever test flight of the Falcon Hypersonic Technology Vehicle 2, or HTV-2. What’s so special about the HTV-2? Maybe the fact that it can reach top speeds of around 13,000 MPH.

Aboard the HTV-2, you could fly from New York to Los Angeles in less than 12 minutes. A flight from London to Sydney would take you no more than an hour.

Except you won’t be flying on it anytime soon. The HTV-2 is an unmanned aircraft that while maneuverable, glides through the air. It is launched via rocket, which takes it up to the edge of space and drops it off for a hypersonic soar.

This will be the second test-flight of the aircraft. The first occured on April 22nd, 2010. That flight resulted in 9 minutes of “unique flight data.” Why must they perform live tests of the HTV-2? Why can’t they just test it in a wind tunnel?

Wind tunnels capture valuable, relevant hypersonic data and can operate for relatively long durations up to around Mach 15. To replicate speeds above Mach 15 generally requires special wind tunnels, called impulse tunnels, which provide milliseconds or less of data per run. To have captured the equivalent aerodynamic data from flight one at only a scale representation on the ground would have required years, tens of millions of dollars, and several hundred impulse tunnel tests.” According to Schulz, impulse tunnel testing is required to create a portion of Mach 20 relevant physics on the ground.

And even then, we wouldn’t know exactly what to expect based solely on the snapshots provided in ground testing. Only flight testing reveals the harsh and uncertain reality.

Mach 15 isn’t good enough. They need Mach 20, baby.

The HTV-2, which travels at 3.6 miles per sec, reaches surface temperatures of 3,500 degrees Fahrenheit and beyond. This is hot enough to melt steel.

The purpose of this test flight? Other than a demonstration of some mind-blowing technology, it’s about data collecting –

Data from the program informs policy, acquisition, and operations decisions for future Department of Defense Conventional Prompt Global Strike programs. Hypersonic data is collected through extensive modeling and simulation, wind-tunnel testing and two experimental flight tests. The ultimate goal is a capability that can reach anywhere in the world in less than an hour.

The launch will not be shown via live web cast (like the space shuttles), but you can follow it on Twitter with the DARPA account @DARPA_News. It will take off around 10:45 EST according to a recent tweet.

The launch was scheduled for yesterday but was delayed due to weather. It will take place at Vandenberg Air Force Base in California.