True to US government secrecy, there's a small space shuttle-like vehicle orbiting the Earth and we have no real idea why. While something of this nature is bound to incite mass speculation, there are a few things we are sure of.

The US Air Force's X-37B space plane, as it's officially referred to, has been cruising around the Earth for a record, 720 days on the OTV-5 mission (Orbital Test Vehicle). The plane just recently broke its existing record of 717 days which was set by the same model on the previous OTV-4 mission.

The X-37B is very small. With a total length of 29 feet and a wingspan of just 15 feet, the plane pales in comparison to previous orbital models which boasted lengths of 122 feet with 78 feet, tip-to-tip, wingspans.

Fittingly, the space plane's missions are top secret. While some would speculate that this plane is essentially a "space weapon," the Air Force denies those claims. In vague statements released by the US government, the aircraft is merely testing technologies for future projects. Of course, outside speculators believe these technologies are related to espionage or even the capturing of satellites. Either way, the powers-to-be are keeping a tight lid on this one.

Though the spacecraft is under the jurisdiction of the US Air Force, it does have NASA roots. The program actually began in NASA in 1999, and was originally set to be part of a dual vehicle project: an Approach and Landing Test Vehicle, or ALTV, and an Orbital Vehicle. However, in 2004, NASA relinquished the X-37 development to the Defense Advanced Research Projects Agency, it then became classified.

Using the design from NASA, the Air Force then produced two X-37Bs, both have been used on the five OTV missions. Boeing is the contract holder for this craft and has been since its inception in 1999, apparently building both units.

The OTV missions are getting progressively longer. The original flight, OTV-1, lasted for just 225 days. The next mission, OTV-2, went round and round for 469 days. OTV-3 stayed up for a whopping 674 days and of course, OTV-4 and 5 surpassed those numbers substantially. This is amazing for two reasons in particular; first the spacecraft was originally designed to stay in orbit for a mere 270 days, so it seems that after the first mission, the scientists made the proper adjustments. And secondly, it appears that longevity may the be the motivating factor of this mission. The testing of technologies for future satellites possibly depends on the X-37B test results in order to maintain functionality for several years in the space environment.

"The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America's future in space and operating experiments which can be returned to, and examined, on Earth," Air Force officials wrote in the X-37B fact sheet. 

Lastly, you can track the X-37B from Earth. Check out Space.com's satellite tracker to see where the X-37B is during a mission.