<P> "Fire in the hole" is a warning that an explosive detonation in a confined space is imminent . It originated with miners, who needed to warn their fellows that a charge had been set . The phrase appears in this sense in state mining regulations, in military and corporate procedures, and in various mining and military blasting - related print books and narratives . </P> <P> NASA has used the term to describe a means of staging a multistage rocket vehicle by igniting the upper stage simultaneously with the ejection of the lower stage, without a usual delay of several seconds . On the Apollo 5 unmanned flight test of the first Apollo Lunar Module, a "fire in the hole test" used this procedure to simulate a lunar landing abort . Gene Kranz describes the test in his autobiography: </P>

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