The SR-72 unmanned plane flies at six times the speed of sound — about 4,200 miles per hour, 70 miles per minute. However, this plane is not designed for travel, but as a military assault weapon, one that would leave enemies with no time to hide.

Equipped with hypersonic missiles, this futuristic U.S. Air Force craft designed by Lockheed Martin could strike targets across any continent in less than an hour, according to a fact sheet the company provided to Mashable. But for now it remains a vision, not meant to fly until 2030.

See also: Hypersonic Aircraft Travels 260 Miles in 6 Minutes

To reach such speeds, Lockheed Martin and Aerojet Rocketdyne, the companies said to be actively developing the plane, will have to create a new type of engine. Engines found in big commercial airliners can hit speeds up to two-and-a-half times the speed of sound before they're no longer efficient. Other engines keep their efficiency up to four times that speed, but getting to mach six will require a hybrid engine, one that uses a turbine when it's not going too fast, and a supersonic combustion ramjet when it's ready to move.

Lockheed wants to demonstrate the plane's hypersonic missiles by 2018. Five years later, the company plans to fly a single-engine, less powerful version of the plane for a few test runs. If all goes well, the real thing will be airborne by 2030.

But that assumes the airplane will arrive on time, or even at all. Lockheed Martin's most recent fighter-jet project, the F-35, made plenty of headlines for all the wrong reasons. It's the most expensive plane ever built, a "weapon that costs more than Australia," and it's not finished, even though production began in 1996.

Lockheed Martin declined to comment for this article, though a hypersonics program manager, Brad Leland, commented on the aircraft in a post on the company's website.

“Speed is the next aviation advancement to counter emerging threats in the next several decades," Leland said. "The technology would be a game-changer in theater, similar to how stealth is changing the battlespace today.”

The SR-72 may redefine war. But first, it has to exist.

Image: Flickr, Lockheed Martin