M-21 was infamous for its faliure rate. The program was canciled
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送交者: steven 于 2010-08-11, 17:43:15:
回答: reconnaissance drone, 无人驾驶侦察机。 由 year2226 于 2010-08-11, 17:37:32:
partly because its failure, and the better Spy satellites were deployed.
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