Here's an excerpt from the New York Times about it:

The phrase was popularized in 1979 by Tom Wolfe in his book about astronauts, ''The Right Stuff.'' The phrase-sensitive reporter wrote: ''The 'envelope' was a flight-test term referring to the limits of a particular aircraft's performance, how tight a turn it could make at such-and-such a speed, and so on. 'Pushing the outside,' probing the outer limits, of the envelope seemed to be the great challenge and satisfaction of flight test.''


Research geographer whose mind is full of too many thoughts to keep to herself. Website: Elsewhere: