Clear, sunny skies are forecast for Cape Canaveral Wednesday, perfect weather for the launch of a new unmanned spacecraft and the dawn of an era. Just don’t expect the Air Force to tell you what that new era is.

For the first time, the service will launch the X-37B Orbital Test Vehicle, a brand new, unmanned spacecraft to demonstrate the military’s ability to fly into space, circle the globe for months on end, and return intact, only to fly again.

But whether the X-37 space plane is merely showing off nearly two decades of research and development or is actually a precursor to militarizing the final frontier, is far from clear since the vehicle’s payload is classified. An Air Force official won’t even say when it will return to California or where it will land. But it can “loiter” over the globe for more than nine months.

IN PICTURES: The X-37 space plane

“In all honesty, we don’t know when it’s coming back,” said Gary Payton, deputy undersecretary for the Air Force’s space programs, in a conference call with reporters Tuesday.

'Weaponization' of space?

Arms control advocates say it is pretty clearly the beginning of a “weaponization of space” – precursor to a precision global strike capability that would allow the US to hover for months at a time over anywhere it chose with little anyone could do about it.

“The idea of being able to launch an unmanned research platform that can stay up there for months on end provides you with all kinds of capability, both military and civilian,” says Chris Hellman, a policy analyst with the National Priorities Project, a budget watchdog in Northampton, Mass.

He believes the fact that it is an Air Force initiative may say something about what it will ultimately used to do. And that may not sit well with others. “I can see where the prospect of having half a dozen of these things with unknown payloads circling overhead could be very troubling to people,” Mr. Hellman says.

What the Air Force will say is that the X-37 will demonstrate “various experiments” and allow “satellite sensors, subsystems, components, and associated technology” to be transported into space and back. Officials say the vehicle could change the way the service operates by making space operations more “aircraft like” with a vehicle like the X-37 able to take off and later land and then fly again.

When it returns, scientists will determine how many of its components survived the flight and how long it will take to get the craft back into the air. The shorter the turnaround time, the better, since that would mean fewer X-37s would have to be built, regardless of its ultimate mission.

If it takes a long time to get the bird back in the air, “it will make this vehicle less attractive to us in the future,” Mr. Payton said.

Many unknowns, including ultimate mission

Still, there are many unknowns. And analysts who typically know about such things are left to shrug.

“There does not seem to be a publicly acknowledged capability that this thing will lead to,” says John Pike, director of globalsecurity.org, a national security research organization in Alexandria, Va. “If taken at face value, it seems to be simply to satisfy the idle curiosity of the scientific community.”

Mr. Pike believes one of the inherent values of the X-37 could be as a maneuverable satellite which could be used to look over China's shoulder one day, yet evade any attempts to shoot it down.

On the other hand, says Pike, it could amount to nothing more than “recreational engineering,” borrowing a term from the magazine Scientific American. “What’s a few hundred million dollars between friends?”

Whatever it is or represents, the Air Force likes it. Air Force officials say they are already building another X-37 spacecraft that it hopes to fly by 2011.

IN PICTURES: The X-37 space plane