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2007-10-12 An Alleged Blunder in the Stealth Bomber's Design

2007-10-12 An Alleged Blunder in the Stealth Bomber's...

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AN ALLEGED BLUNDERIN THE STEALTH BOMBER'S DESIGN Managerial economics is of great use in the aerospace industry, but this does not mean that errors sometimes will not occur. The B-2 "Stealth" bomber has cost billions of dollars to develop. According to Joseph Foa, an emeritUS professor of engineering at George Washing- ton University, its design is fun- damentally flawed because two aerodyn~micistS made °a mistake: they mistook a minimum. point for a maximum point. The B-2 is basically a jet-pow~ ered "flying win~' aircraft. In a secret study for the Air Force, the two aerodynamicists, William Sears and Irving Ashkenas (then at the Northrop Corporation}, used mathematical formulas to deter- mine how an aircraft's volume should be proportioned between wing and fuselage in order to maxi- mize its range. Taking the der- ivative oJ range with respect to vol- ume, they found that this deriva- °tive equaled zero when the total volume was almost all in the wing. Hence, they concluded
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Unformatted text preview: II £ly-ing wing" design would maximize range. But in a subsequent analysis, Foa showed that the second derivative was positive, not negative, under these circumstances. Thus, the "flying wing" design miIlimized range; it didn't marimize it. In Foa's words, "The flying wing was the aerodynamically worst possible choice of configuration." This is a very interesting exam-ple of how important it is to look at the second derivative to make SUIe that you do not confuse a maximi-zation point with a minimi7:ation point. While the backers of the B-2 bomber claiIn that it is a good plane despite this error, no one denies that the error is an embarrass-ment. · .-This discussion is based on W. Biddle, "Skeleton Alleged in the Stealth Bomber's Closet." Science (May 12, 1989). 00...
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