They were not developed primarily because the main player in the field, NASA, became preoccupied with its part in the Cold War and locked into a ballistic missile mindset.

• 而在一开始没有得到开发是因为这一领域的主要参预者，国家航空航天局当时一门心思投入到冷战之中，倾注于弹道导弹的研究和利用。