The Air Force yesterday successfully launched its secretive unmanned space vehicle prototype, the X-37B Orbital Test Vehicle (OTV) from Cape Canaveral Air Force Station, Fla., according to service spokesman Capt. Nicholas Plante.

Plante said the Atlas V rocket carried X-37B into low earth orbit to begin its second flight following refurbishment. X-37B spent 224 days, nine hours and 24 minutes in orbit between April and December 2010 in its maiden voyage.

Air Force X-37B Program Manager Lt. Col. Tom McIntyre said yesterday in a statement X-37B is designed for an on-orbit duration of approximately nine months or 270 days. McIntyre said this first re-flight is an important step in the program.

The X-37B’s mission is classified and the Air Force is tight-lipped about its intent, but the service said, officially, X-37B is a Defense Department effort to improve space capability and further develop an affordable, reusable space vehicle. X-37B has been watched closely by interest groups like the Union of Concerned Sciences (UCS) for its ability to return from orbit and land on a runway, which requires extra structure, such as wings, landing gear and heat shielding, to withstand the rigors of re-entry into Earth’s atmosphere (Defense Daily, Dec. 11).

The UCS said the extra structure for a capability to land on a runway also costs a lot more money.