The US Air Force is getting ready to land X-37B, an unmanned space plane that can both enter orbit and land without human intervention, and has spent a record of 665 consecutive days on a low-earth orbit mission. Tuesday is the date set for the return of X-37B Orbital Test Vehicle. The space craft is currently orbiting at 28,044km/h, at a distance of around 350km into the sky. It is unsure exactly what the X-37B is being used for, but the one definitive thing the Air Force will say about it is that it has no plans to develop a manned version. The spacecraft measures up at 29 feet long and 9.5 feet high, about one-fifth of the size of the retired NASA space shuttles. As always with top secret programs, there has been much speculation online about what is being done with the aircraft, theories range from surveillance to a platform for a new generation of kinetic weapons that can be used from space.