X-51A
X-51A-
More X-51A flights are expected as early as this fall .
更多的X-51A的航班，预计最早在今年秋天。
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The hypersonic X-43A flew faster , but the X-51A flew longer .
的极超音速X-43A条飞行速度更快，但X-51A的飞行时间。
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It 's those newer , pilotless X-Planes that have been in the headlines of late , first with the X-37B that was launched into orbit in April , and then again in late May , with the hypersonic X-51A .
它的那些新的，无人驾驶的X已经在最近，与X-这是在4月发射进入轨道第37B第一头条新闻出现的飞机，然后在5月下旬，再次的极超音速X-51A条。