If all goes well, the US Air Force's mysterious X-37B will blast off into space for the fourth time on 20 May. But for the first time, they're actually telling us what the space plane will be doing — well, some of it anyway.
The US Air Force currently has two of the X-37B planes, which look like miniature versions of NASA's space shuttle. Altogether, they have gone on three missions that lasted a total of 1367 days in space. The last mission ended after 674 days in orbit last October. What the space planes were doing all the time is anyone's guess.
But the Department of Defence has made the unprecedented step of releasing some details of this upcoming flight. We now know, for example, that they will test a new orbital thruster system that could be used to manoeuvre satellites in space. The Hall thruster electric propulsion system, made by Aerojet Rocktdyn, use electricity and xenon and could be used to develop agile new satellites.
Last week, NASA also announced the details of materials science research that will happen on the X-37B. The plane will carry over 100 different materials to test how they hold up in space. This experiment, called Materials Exposure and Technology Innovation in Space (METIS), will gather data for materials that could be used in future probes, telescopes and space craft.
Anything else though? Well, they aren't telling us.
Top photo: The X-37B being launched from Cape Canaveral, Florida, in December 2012. Credit: U.S. Air Force