Aircraft

The US Air Force plans to launch the second test flight for the X-37B space plane on 4 March, the service says, provided the weather at Cape Canaveral cooperates.

The Boeing-built 8.8m-long (28.8ft), 4.2m-wide reusable space plane will lift off inside the nose cone of a United Launch Alliance Atlas 5 rocket.

The second unmanned aircraft, known as Operational Test Vehicle-2, is expected to stay on orbit for 270 days or more, collecting test data similar to that from the first flight last year and expanding the flight envelope. The test team will also be paying particular attention to the performance of the electromechanical and autonomous landing algorithms, the service says. There will also be fewer cross-range and wind restrictions for the second flight.

"The first flight was focused on vehicle check out and you obviously want to check things more than once," the air force says. "It's still an X-plane, still an experimental test programme."

The only anomaly in the first flight of OTV-1 was a blown tyre on landing at Vandenberg AFB in California on 3 December 2010; tyre pressure on OTV-2 has been reduced by 15%, the service says.

OTV-1 was launched on 22 April 2010 and returned, with its classified payload, after 224 days and 9h in space.

The USAF will not comment on possible payloads for OTV-2 or the partially classified programme's price tag, saying only that funds for the second test launch have already been allocated and were not tied to the fiscal year 2012 budget released on 14 February, or the still-under-debate 2011 budget.