A futuristic new hypersonic Air Force jet that promises transatlantic flights from New York to London in about an hour was tested on Tuesday over the Pacific. The X-51A WaveRider jet can go five times faster than the speed of sound without a pilot, and, in theory, could shorten the amount of time travelers have to spend airborne. But this vehicle isn't without its problems, so don't expect to buy a one-hour flight to London any time soon. Here, a concise guide to the revolutionary innovation: 

What makes it go so fast?
The WaveRider — which is small, wingless, and resembles a shark — uses a special "scramjet" engine — shorthand for "supersonic combustion ramjet," says Daniel Lametti at Slate — to reach speeds of up to 4,500 mph. A standard Boeing 787, for example, tops out at 647 mph. The jet works by gobbling fast-moving air into an engine, where it mixes with fuel and is then ignited to produce thrust. Ordinary planes, on the other hand, require the help of turbines to achieve the same effect. As a result, the scramjet is able to reach "dazzling speeds" with no moving parts, says Jason Koebler at US News, making for an "efficient and extremely powerful engine."

Any downsides?
For starters the jet can't start from a standstill, and therefore needs to be dropped from another plane to become airborne. "Since forward motion is what pushes air into the engine, the plane must be brought up to speed before ignition," says Slate's Lametti. That also means the WaveRider is incredibly difficult to start up: One military report likens producing thrust on the scramjet to "lighting a match in a hurricane and keeping it burning."

How did this test flight go?
Not well. While it was expected to go Mach 6 after being dropped from a B-56 Bomber, a faulty control fin compromised the flight and the WaveRider prototype was lost over the Pacific. "It is unfortunate that a problem with this subsystem caused a termination before we could light the Scramjet engine," said Charlie Brink, the X-51A program manager. "All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives."

How did it do on previous tests?
Slightly better. The X-51A was first conceived in 2004, and made history in May 2010 when it was dropped and flew successfully for 140 seconds, reaching Mach 5. After slowing down, "it lost telemetry and was destroyed by controllers on command," says The Washington Post

When can I get a ticket to fly on one?
Not anytime soon. The hypersonic Concorde, for example, which took passengers from New York to London in half the normal time, couldn't turn a profit and was shuttered in 2003. In the case of the X-51A, passenger planes that use the engine "probably wouldn't be economically viable," because the energy and resources required to get the plane up to speed (i.e. another plane) would be "very expensive," says Slate's Lametti. In the short term, the Pentagon is hoping to apply the scramjet's technology to hypersonic missiles, which would be able to hit targets around the world in an hour or less.

Sources: Daily Tech, Fox News, Slate, U.S. News, Washington Post