![Virgin Galactic\'s SpaceshipTwo takes off for a suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)](http://www.ecns.cn/hd/2018/12/14/a9d3934fba3e460c816073372fc9beeb.jpg)
Virgin Galactic's SpaceshipTwo takes off for a suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)
![Virgin Galactic\'s SpaceshipTwo takes off for a suborbital test flight of the VSS Unity on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as Unity made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)](http://www.ecns.cn/hd/2018/12/14/586bcabcd29f4aa98a90cb0cbdaf84df.jpg)
Virgin Galactic's SpaceshipTwo takes off for a suborbital test flight of the VSS Unity on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as Unity made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)
![Virgin Galactic\'s SpaceshipTwo takes off for a suborbital test flight of the VSS Unity on December 13, 2018, in Mojave, California. - Virgin Galactic marked a major milestone on Thursday as Unity made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)](http://www.ecns.cn/hd/2018/12/14/243c5758f0254a7ca3f23d23b3460a93.jpg)
Virgin Galactic's SpaceshipTwo takes off for a suborbital test flight of the VSS Unity on December 13, 2018, in Mojave, California. - Virgin Galactic marked a major milestone on Thursday as Unity made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)
![Virgin Galactic\'s VSS Unity launches for a suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights.(Photo/Agencies)](http://www.ecns.cn/hd/2018/12/14/3bf5aba6b06e4a54b9707d50e6e9ebe8.jpg)
Virgin Galactic's VSS Unity launches for a suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights.(Photo/Agencies)
![Virgin Galactic\'s VSS Unity comes in for a landing after its suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)](http://www.ecns.cn/hd/2018/12/14/71fa3618f0b24c4c9ffdc876f4980b1f.jpg)
Virgin Galactic's VSS Unity comes in for a landing after its suborbital test flight on December 13, 2018, in Mojave, California. Virgin Galactic marked a major milestone on Thursday as its spaceship made it to a peak height, or apogee, of 51.4 miles (82.7 kilometers), after taking off attached to an airplane from Mojave, California, then firing its rocket motors to reach new heights. (Photo/Agencies)