Another US military mini shuttle blasted off on 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, the US Space Force said.

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.