The US military has deployed five unmanned X-37B spacecraft over the last decade, and each flight was longer than its predecessor.
According to the Air Force spokesman Major William Russell, the current mission has no specific end date. The spaceship will not return to Earth until all of its goals have been achieved, he said.
The details of these goals remain a closely guarded secret.
The X-37B program is of general interest because of this secrecy: The Air Force does not divide the locations of the X-37B aircraft while in orbit, although amateur astronomers have made detecting sports the spacecraft with telescopes ,
It is known that the military uses the aircraft to develop reusable space technologies. Officers do not necessarily want to use the same X-37B aircraft multiple times, but the Air Force has designed the aircraft to test new navigation systems, methods of re-entering the Earth's atmosphere, and landing safely on solid ground.
] The X-37B is also popular with space enthusiasts due to its unique design. The small spaceship aircraft fly into orbit on powerful rockets and then drop off to complete their mission. When their tasks are done, they fall back to Earth and land horizontally on a runway, such as a commercial jet or space shuttle orbiter, that comes in to land.
According to Russell, the spokesman for the Air Force, the spaceships will also conduct "experiments" that can be "returned to Earth and examined" after the mission is over. The nature of these experiments is – you guessed it – also top secret.
Speculators have speculated that the aircraft may be involved in spy activities or testing a space weapon. In the US and abroad, both types of projects have priority.
The current X-37B aircraft in orbit, called OTV-5, was launched into space in September 2017 with a SpaceX Falcon 9 rocket. The previous flight for OTV-4 lasted 718 days and ended in May 2017.
The first X-37B launched in April 2010 and returned to Earth about eight months later, for a total of 225 days in space.
] All plans and were built for the US military from Boeing ( BA ) . The financial terms of the contracts are unknown.