NASA may no longer possess a reusable vehicle for traveling to and from low earth orbit, but the United States Air Force has all but established a permanent presence up there. Maybe you've forgotten about the X-37B, the USAF's pilotless, reusable space plane that's been in orbit since launching on March 5, 2011, but it's still up there making laps. Today marks the first day of its second year in continuous orbit, a milestone for the mysterious program that the Air Force will tell us virtually nothing about.