While that may make suborbital travel safer, it would add significant cost and complexity to an emerging industry that has until now operated largely as the playground of billionaires and dreamy engineers.

出自-2015年12月阅读原文

It is the first to launch suborbital flights.

出自-2015年12月阅读原文

But more recently, companies have begun to plan more affordable " suborbital " flights — brief ventures just to the edge of space's vast darkness.

2015年12月六级真题（第二套）阅读 Section C