Advertisement
10. Orbital Test Vehicle AF X-37B
Joined the Service in 2019
Not retired: N/A
Price: Not specified
This one is a little more enigmatic because the AF X-37B Orbital Test Vehicle's operations—including its cost—have been kept fairly secret. The Air Force declared in 2006 that it intended to construct a Boeing X-37A variant. The company hired to construct this test vehicle was Boeing.

Advertisement
YouTube.com / Vandenberg Space Force Base / AF X-37B Orbital Test Vehicle
Utilised to "demonstrate technologies" that may eventually be turned into a "reliable, reusable, [and] uncrewed" space vehicle is the X-37B Orbital Test Vehicle. Based on what information has come to light about this mysterious programme, the OTV is essentially a means of deploying the military into space without actually sending troops up there.