That looks quite feasible with the HSCT design, but the real problem will be getting the engine noise reduced, and this involves a high Mach number jet. The Mach number of the jet can not be lowered, requiring some other method, a subject that he is working on at the moment. Lighthill is proud of his aero-acoustical contributions, because they have clearly influenced the whole development of civil aviation, and because they made it possible for jets to be more powerful and quieter. It was mathematically difficult to solve the problem. Turbulence is difficult enough, but then coupled with deciding what noise it generates makes the problem even more difficult.
Turbulence is in a way a vortex phenomenon, an incompressible phenomenon.
Somehow the noise is a by-product. Lighthill is also fond of his biofluiddynamics, understanding that not everyone would be, but to him it is quite important. The topic was his latest biofluiddynamics work about the inner ear and the fluid mechanics in the cochlea. Here again it is quite a problem to formulate the problem. He thinks that most people in hearing regard that lecture as a good summary of what they know of the subject.