No replacements will be forthcoming until energy is cheaper. Already, an average airliner flying at Mach 0.76 has air over the top of the wing going a relative Mach 1.2. This then slows in the form of a shockwave. Shockwaves absorb a great deal of energy.
Even the best Airbus wings, with isentropic recompression still can't go more than Mach 0.8 without generating wing shocks too big to be uneconomic. Either government pays or we don't have them I suspect.
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No replacements will be forthcoming until energy is cheaper. Already, an average airliner flying at Mach 0.76 has air over the top of the wing going a relative Mach 1.2. This then slows in the form of a shockwave. Shockwaves absorb a great deal of energy.
Even the best Airbus wings, with isentropic recompression still can't go more than Mach 0.8 without generating wing shocks too big to be uneconomic. Either government pays or we don't have them I suspect.