NASA正在加速研究新型载人航天器,以在21世纪初替代现有的航天飞机。 研制这种航天器的计划预计将列入NASA今后5～7年的预算中。 现在正在考虑两种方案。第一种方案是改进方案,对现有航天飞机的设计进行较大的改进;第二种是设计一种大大不同于现 NASA is accelerating research into new manned spacecraft to replace existing space shuttles early in the 21st century. Plans to develop such a spacecraft are expected to be included in NASA’s budget for the next 5-7 years. Two options are now being considered. The first option is to improve the program to make major improvements to the existing space shuttle design. The second is to design a solution that is significantly different from the existing