Concorde was doomed to failure from the start because it hit an evolutionary cul-de-sac in terms of aircraft design, new research suggests.
An analysis by Adrian Bejan, professor of mechanical engineering and materials science at Duke University in the USA, has suggested that design trends dominating the aerospace industry have been driven by the constructal law, which he developed in 1996.
The law states that for a system to survive it must evolve to increase its access to flow – a process he says is evident in animal vascular systems, river systems, tree branches and even modern road networks.
In a paper appearing online in the Journal of Applied Physics, Bejan teamed up with Jordan Charles, a researcher and development engineer, and Sylvie Lorente, a professor of civil engineering at the University of Toulouse, to apply his law to the design of commercial aircraft using statistics on design parameters from the historical databases of commercial aircraft.
While many patterns emerged, the two that stood out were the increasing size of commercial aeroplanes and the fact that the relationship of body mass to speed is nearly identical to similar statistics from various animals – suggesting evolutionary constraints found in nature are at work in the aviation industry.
"Larger animals have longer lifespans and travel farther distances, just as passenger airplanes have been designed to do. For example, the ratio of the engine to aircraft size is analogous to the ratio of a large animal's total body size to its heart, lungs and muscles," said Bejan.
One notable outlier in the results was the Concorde, which Bejan points out had limited passenger capacity, a low mass-to-velocity ratio, an off-the-charts fuselage-to-wingspan ratio, massive engines and poor fuel economy.
“The Concorde was too far off from the ratios that evolution has produced in passenger jets," he explained. "It would have had to adhere to the constructal design rules to succeed."
According to Bejan, the same constructal law that underpins animal evolution has also dictated the main design features needed for aircraft to succeed: the engine mass has remained proportional to the body size, the wing size has been tied to the fuselage length, and the fuel load has grown in step with the total weight.
He says the analysis reveals the general design parameters that future passenger aircraft should follow to succeed economically.
"This study gives the rough sketch of what airplane designs will put you in the game," said Bejan. "For design companies, it is money in the bank."
Jose Camberos, research aerospace engineer and lead of design space exploration at the Multidisciplinary Science & Technology Center of the Air Force Research Laboratory at Wright-Patterson Air Force Base in Dayton, Ohio, said he hoped the work would give the field better insight into where the design of aircraft is going.
"There is definitely an analogy to be understood and articulated to explain why engines and airplanes are sized the way they currently are and how that has evolved," said Camberos, who was not involved with this study.
"By looking at the development of aircraft in a larger context in these terms, it may be possible to gain insights into how best to achieve what nature has been able to accomplish already."