It's a multi-variate optimization problem for sure, where mass, specific impulse, thermal protection, structural load, aerodynamics, and entry profile all inter

It's a multi-variate optimization problem for sure, where mass, specific impulse, thermal protection, structural load, aerodynamics, and entry profile all interact. The author may be right. But I'm not yet convinced there is no solution. I am convinced that, if there is, it will cost much more than originally projected.