The US has relaunched its experimental spacecraft the X-37B, ostensibly as a way to test reusable spacecraft technology. Experts believe the project could also be intended to usher in a whole new era of space espionage.
The vessel, measuring 60 meters (196 feet), blasted off from Cape Canaveral, Florida, on Tuesday, carried aboard a powerful Atlas 5 rocket.
Information about how long the X-37B would remain in orbit - and details of its precise mission - was not made available.
The Boeing-built craft, also known as Orbital Test Vehicle, or OTV, is about a quarter the size of a NASA space shuttle. It is powered by solar energy rather than chemical fuel cells, maximizing the time it can remain in space. The X-37B is capable of landing on a conventional runway on its return to Earth.
While the X-37B program has been described by the US military as a way to research the future viability of a reusable spacecraft program, speculation has arisen that it has a more secret function.
'Weaponization of space'
Space experts have said that the craft could be part of a high-tech espionage program, deploying small satellites and interfering with other countries' satellites. Russia has even alleged that the US is exploring ways of putting weapons in space.
The project was embarked upon by NASA in 1999, before it was adopted by the Defense Advanced Research Projects Agency (DEPRA), a research and development arm of the US military.
The vessel launched on Tuesday is the same one that was launched by NASA in 2010, circling the Earth for seven months. A second X-37B returned to Earth in June after 469 days in space - something of an endurance test given its intended span of 270 days.
Both previous orbits were conducted roughly 200 miles (320 kilometers) above the Earth.
rc /jm (AFP, AP, Reuters)