Mysterious X-37B military space plane marks 700 days in a job

Artist’s illustration of the u.s. Air Force’s robotic X-37B space plane in orbit.

(NASA Marshall Space Flight Center)

The u.s. Air Force’s robotic X-37B space plane has now the Earth orbit for 700 days at the latest hush-hush mission.

The mission — known as Orbital Test Vehicle 4, or OTV-4 — began on May 20, 2015, with a launch on a United Launch Alliance Atlas V rocket from Florida’s Cape Canaveral Air Force Station.

As the name implies, the current mission is the fourth for the X-37B program. These orbital trips are getting progressively longer: OTV-1 launched in April 2010 and spent 224 days in space, OTV-2 was launched in March 2011 and orbited the Earth for 468 days, and OTV-3 began in December 2012 and operated for almost 675 days. [Most Dangerous Space Weapons Ever]

Most of the X-37B cargo and operations are classified, so it is unclear exactly what the space planes are doing as they zoom around our planet. But there is nothing nefarious plan, Air Force officials have emphasized.

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“The primary objectives of the X-37B are twofold: reusable spacecraft technologies for America’s future in space and operating experiments which can be returned and examined, on Earth,” Air Force officials wrote on an X-37B fact sheet.

It is interesting that the same fact sheet states that the X-37B is designed to operate for 270 days in orbit — an expensive brand that the three most recent missions have blown past.

The air force is known to own two of the X-37B vehicles, both of which were built by Boeing. Each solar-powered space plane is 29 feet (8.8 meters) long and 9.6 ft (2.9 m high, with a payload bay the size of a pick-up truck bed. (For comparison, the two X-37Bs could fit inside the payload bay of one of NASA’s retired space shuttle orbiters.) Each of the two X-37Bs have flown two missions to date.

The X-37B launches vertically atop a rocket and is horizontal for a runway landing. All four missions have launched from Cape Canaveral, and the first three landed at the Vandenberg Air Force Base in California.

But OTV-4 may buck the latter trend and land in Florida. The air force has changed, the old Shuttle Landing Facility (SLF) at NASA’s Kennedy Space Center, which is next to Cape Canaveral, suitable for the X-37B. And the Air Force officials have said they aim to consolidate the program’s launch and landing activities on Florida’s Space Coast.

The SLF final hosts for a touchdown in July 2011, when space shuttle Atlantis landed there to wrap up the STS-135 mission — the last for the iconic shuttle program.

Follow Mike Wall on Twitter @michaeldwall and Google+ . Follow us @Spacedotcom , Facebook or Google+ . Originally published on .

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