Helium is used to pressurize tanks and help push fuel into the engines. Without proper helium flow, the rocket cannot safely fly. Because the upper stage is hard to reach at the launchpad, NASA rolled the stacked rocket back into the Vehicle Assembly Building, the sky-scraping hangar where it was originally put together.
(If you found it too simple. Here’s a harder version.)
。业内人士推荐safew官方版本下载作为进阶阅读
#欢迎关注爱范儿官方微信公众号：爱范儿（微信号：ifanr），更多精彩内容第一时间为您奉上。
Asher D’Addamio