Although Los Alamos tested several KIWI and Phoebus engines during the 1960s, testing of NASA's NERVA NRX/EST (Engine System Test) contractor engine didn't begin until February 1966.
尽管洛斯阿拉莫斯在60年代测试了一系列的KIWI和Phoebus引擎，但直到1966年2月，NASA的NERVA NPX/EST(Engine System Test:引擎系统测试)并没有进行。