US military's remote controlled, solar-powered space plane takes off for mystery mission

The US military’s mystery space plane rocketed into orbit again today, this time with an extra load of science experiments.

A United Launch Alliance Atlas V rocket lifts off from Launch Complex 41 at the Cape Canaveral Air Force Station. Source: Associated Press

The X-37B was launched on board a United Launch Alliance Atlas 5 rocket from Cape Canaveral in Florida.

It will be the sixth flight of the X-37B, a solar-powered plane that's flown by remote control without a crew.

Officials aren't saying how long the spacecraft will remain in orbit this time or the purpose of the mission.

The previous mission lasted a record two years, with a touchdown shrouded in darkness at NASA's Kennedy Space Centre last year.

The winged spacecraft, also called the Orbital Test Vehicle, resembles NASA’s old shuttles, but is considerably smaller at 8.8 metres long.

The one just launched features an extra compartment for experiments, including several for NASA.

The Air Force has two of these reusable space planes.

Since the first flight in 2010, the space planes had logged a combined 2,865 days in orbit as of Sunday.

That's seven years and 10 months.

Delayed a day by bad weather, Sunday's launch was the second one for the newly established Space Force.

In March, it hoisted a national security satellite.

United Launch Alliance dedicated Sunday's launch to the health care workers and others who are working on the front lines of the pandemic.