The third part, now that Constellation is cancelled, is to encourage private-sector firms to compete, so as to provide transport to and from the space station.
“星座项目”既然已经被取消，第三部分就是鼓励私人企业相互竞争，来为空间站的往返提供运输服务。
2
They say it could one day replace NASA's Space Shuttle to transport up to 12 tonnes of cargo and astronauts to the International Space Station.
他们说，它有一天可能取代美国航空航天局的航天飞机，向国际空间站运送宇航员和多达12吨的货物。
3
Unplanned sprawl leads to a shortage of green space, strains transport systems, and makes it hard for businesses or housing developers to find sites.