The Busemann Biplane consists of two diamond shapes that cancel each-others shockwaves. Which means that it generates no sonic boom or wave drag.
It can be modified to generate lift with a slight sonic boom and CFD simulations (which include skin friction) estimate a lift-to-drag ratio of around 20 (PDF link) vs 7-8 for the Concorde. But for now let's focus on the original zero-lift design.
A shockwave is a sudden discontinuity. Much like a hydraulic jump, it is an irreversible process that generates entropy. So this can't be "undone" by the rarefaction fan at the back. Does this mean that the article is wrong and that the shockwaves, even if there is no sonic boom, still steal energy from the biplane (in addition to the skin friction)?
