英语翻译

英语翻译
For a list of spaceflights with human crews organised by program,see List of human spaceflights by program.
These chronological lists include all crewed spaceflights that reached an altitude of at least 100 km (the FAI definition of spaceflight),or were launched with that intention but failed.The USA has adopted a slightly different definition of spaceflight,requiring an altitude of only 50 miles.During the 1960s,13 flights of the US X-15 rocket plane met the US criteria but only two met the FAI's.These lists include only the latter two flights; see the X-15 article for a list of all 13.
As of 07 April 2007,there have been 257 manned spaceflights that reached 100 km in altitude,of which 249 reached orbit successfully.