Whether the X-37B will break the record or not, however, is up to the Air Force, which is famously tight-lipped about the 29-foot craft. In the past they have failed to alert the press to space plane tests until after the mysterious missions are complete and the vehicle is safely back on the ground.
When asked about the mission's end date, Air Force spokeswoman Captain AnnMarie Annicelli said this by email: "The landing date will be determined based on the completion of the program's on-orbit demonstrations and objectives for this mission."
The alleged purpose of the X-37B is to test the viability of various technologies while in orbit – thus its alternative name of Orbital Test Vehicle (OTV). However, the main payload of all four X-37B missions to date has been classified from the public.
Military, aerospace and conspiracy fans alike hold an interest in the X-37B. It is one of the Pentagon's biggest mysteries, and theories range from it being a spy satellite to a space weapons testing platform to a weather-controlling climate dominator (though perhaps the originators of that theory were watching too much GI Joe.)
Compounding that is the fact that all previous X-37B missions have ended at Vandenberg Air Force Base in California, which was heavily associated with the STAR WARS missile defense system in the 1980s.
The Pentagon has denied the seedier rumors, insisting that their plane's purpose is to serve as "an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the US Air Force."
"Technologies being tested in the program include advanced guidance, navigation and control, thermal-protection systems, avionics, high-temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems and autonomous orbital flight, re-entry, and landing," according to the X-37B's fact sheet.
In February, rumors circulated that the X-37B was actually going to make a secretive landing at the Kennedy Space Center in Florida instead of Vandenberg. The reports were denied by the Air Force, which claimed the KSC's preparations for a landing were simply a training exercise.
They have taken a step back on that now, as Annicelli said that "while the program has the capability to land at either KSC or Vandenberg, the landing location is determined by a variety of factors."
The previous X-37B mission began in 2012 and lasted for 22 months. That voyage shattered the orbital endurance record set by – you guessed it – the previous X-37B mission.
