The Airplane - Jay Spenser [136]
Before too many more years have passed, the power density (power output relative to weight) of fuel cells will have improved to the point where they can play efficiency-enhancing roles aboard commercial jetliners. For example, more-electric-architecture airplanes like the 787 could use fuel cells as their auxiliary power unit. This fuel cell APU in the tail cone could even provide primary electrical power in flight, offloading the engine-driven generators to make these airplanes even more fuel efficient in the future.
Jet transports as we know them today may one day give way to futuristic concepts such as the blended wing-body (BWB).
NASA
“Prediction is extremely difficult,” Danish physicist Niels Bohr is said to have remarked, “especially about the future.”3 This droll inside joke alludes to prediction at the present moment because of the odd behavior of particles on a subatomic scale.4 But the dangers of making categorical predictions about the future are self-evident. We cannot see what’s ahead for aviation because technological development itself is largely an accidental process. While it is likely that today’s jetliners may someday look as antiquated as the DC-3 does to us now, we certainly cannot predict how human thought will flow, what connections will be made, and which ideas will serve future generations.
Our modern jet transports have tremendous pluses in terms of performance and safety. They’re also highly efficient. Despite being an order of magnitude faster, newer jetliners are more fuel-efficient than most economy cars in the amount of fuel consumed per passenger seat.
Nevertheless, today’s “tube and wing” designs—so called because they have discrete fuselages to house payload and discrete wings to provide lift—do have limitations that frustrate aeronautical engineers. One is that their fuselages generate no lift; they contribute only skin friction that almost doubles the airplane’s total aerodynamic drag.
This leads aviation futurists to contemplate blended wing-body concepts. In a BWB airplane, a flattened and broadened fuselage that provides its own lift merges seamlessly into the wings, creating an airframe that is considerably more fuel efficient and quieter than today’s airplanes.
There are many problems with BWBs that will tend to limit them to lower speeds, lower altitudes, and shorter ranges. They also may not be as inherently stable and may have difficulty meeting safety requirements for takeoff or emergency evacuation.
For airlines, getting passengers to fly aboard BWB airliners would be a very hard sell because the seats would be spread across a wide, roughly triangular floor area with few if any windows. Passengers seated far outboard in this wide cabin would be so far from the airplane’s roll axis that normal banked turns would subject them to large vertical translations through space. Depending on the direction of the turn, the airplane’s bank would feel either like falling through an open trapdoor or rising suddenly skyward in a Ferris wheel.
Consequently, BWBs are more likely to find military and cargo applications than passenger use. Here their structural-weight efficiencies, payload advantages, greater fuel efficiency, avoidance of environmental emissions at very high altitudes, and exceptional quiet could all be put to productive use.
William Thomson (1824–1907), an Irish-born physicist and mathematician of the nineteenth century, was knighted as Lord Kelvin in Scotland for his contributions to electricity, thermodynamics, and other fields (the Kelvin scale of absolute temperature is named after him). Near the end of a long life, this octogenarian made a prescient prediction just as—unbeknownst to him—the airplane was being invented.
“Young man,