Another U.S. military mini shuttle blasted off Thursday night to conduct classified experiments in space.

Launched by SpaceX, the space plane with no one aboard took off from Cape Canaveral, Florida. It’s the eighth such flight for the test vehicles known as X-37B. This one will test laser communications and safe navigation without GPS, according to the U.S. Space Force.

It’s not yet clear how long the mini shuttle will remain aloft. The last X-37B circled the globe for a little over a year before returning to Earth in March. Previous missions have lasted months to years.

The Boeing-made reusable space planes were first launched in 2010 and are 29 feet (9 meters) long with a wingspan of almost 15 feet (4.5 meters).

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AP science writer Adithi Ramakrishnan contributed.

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