by Tristan Rayner in Exhale on Wednesday 30 April 2014

The X-37B is a kind of robotic space plane, built by the US. It’s been in Earth’s orbit for more than 500 days. And its real purpose is a complete mystery. Intrigued?

Here’s what we do know about X-37B

Constructed in California, the Boeing-built X-37B Orbital Space Vehicle was built for the US Air Force as a test vehicle; not intended to reach production. It is a quarter the size of the Endeavour Space Shuttle. It is equipped with heat-shield protection for re-entry to Earth’s atmosphere.

Currently the X-37B is orbiting at 28,044km/h, at a distance of around 350km in the sky. It can land, but no one will say when that will be.

It’s been in the sky before, after being launched on April 22, 2010, on a rocket. It then landed on December 3, 2010 – blowing a tire and suffering minor damage to its underbelly.

It took off again from Cape Canaveral on December 11, 2012 – now reaching 500 days in orbit.

The Air Force also launched a second model of X-37B on March 5, 2011. Described by the U.S. military as an “effort to test new space technologies”, it landed safely at Vandenberg Air Force Base on June 16, 2012, after 469 days in space. This third mission has now smashed this previous record.

X-37B’s actual functions are still heavily classified.

As you’d imagine, conspiracy theorists are having a field day, and here’s why:

Powered by a solar panel that unfurls once in orbit, X-37B can open with small, shuttle-like payload bay in its middle – think of a clamshell opening from underneath. There’s room for more than just a solar panel too. Exactly what items it carries, and why they need to be in space so long, has proved elusive for analysts, the space community, and the media.

To add further intrigue, the plane is classified as a secret project, yet maker Boeing has released pictures and more than two pages of details on the X-37B. That’s not how secrets are usually dealt with. By contrast, the secret Lockheed SR-71 Blackbird was not declassified until decades after it had been flown in the Vietnam War.

The X-37 started life way back in 1999 when NASA asked Boeing’s Phantom Works division to develop an orbital test vehicle. This was a civilian project, and the X-37 was originally spec’d as an unmanned, robotic spacecraft that would rendezvous with satellites to refuel, repair them, or crash them back to Earth once their lifecycle was complete. But, in 2004, the project was transferred to DARPA and since then, it has been highly classified.

The amateur skywatching community that documents satellites say it’s orbiting between 43.5 degrees north latitude to 43.5 degrees south latitude. That’s a band around the middle of Earth that takes in much of the US, Middle East, and Asia, but is away from Russia, and Europe. Spotters suggest that at the altitude of 350km, it is ideal altitude for spying, but too low to refuel or fix other satellites.

It’s versatile, and has worked well enough that Boeing is contracted to create the next model, the X-37C. It will be at least 65% larger and have the ability to carry up to six astronauts, while operating unmanned.

The X-37B Orbital Test Vehicle

The X-37B Orbital Test Vehicle in the encapsulation cell at the Astrotech facility April 13, 2010 (via US Air Force).

What we can guess

The two most popular theories suggest the vehicle is simply running an extended duration test – a marathon in space. The other theory is that the two previous missions prove the testing phase is complete, and it is now on an extended operation running a mission, or multiple missions.

The long endurance run theory has credit; proving that new, experimental critical components can work reliably for a long-duration in space, close to Earth.

The running-mission has credit too – with two previous missions complete, X-37B can now operate at length. And perhaps it is – observing, spying, experimenting, hosting space-weapons, or collecting data for the NSA. We just don’t know.

Both theories are plausible.

What it isn’t

Plenty of conspiracy theorist have posed the question of X-37B carrying a nuclear payload, to guarantee a ‘first strike’ opportunity (or to have a counter-option in place).

If you have any hope for humanity, that can’t be right. The US is a signatory to The Space Treaty, which is no joke. Space-based weapons of mass destruction are banned.

(One curious example of a space-based weapon that isn’t banned is a Kinetic strike, where objects whizzing around the Earth at great speed are intentionally sent to the ground, causing a meteorite-like impact and widespread damage. This type of attack is also known as ‘Rods from God’.)

An artist's conception of the X-37 Advanced Technology Demonstrator as it glides to a landing on earth.

An artist’s conception of the X-37 Advanced Technology Demonstrator as it glides to a landing on earth. (Via NASA)

General characteristics

Crew: None
Length: 8.9m
Wingspan: 4.5m
Height: 2.9m
Loaded weight: 4,990kg
Powerplant: 1 × Aerojet AR2-3 rocket engine (hydrazine)
Power: Gallium arsenide solar cells with lithium-ion batteries

[Update: As of June 30, X-37B remains in orbit, and has been in space for 566. There has been no further news. We're watching this one and will update with any information we receive.]

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