daleg

There are tons of suitable engines and engine designs. The big problem is: Who would buy it? No manufacturer in the already niche, thin-margined, and overstocked business/charter jet market is going to be the first penguin off the iceberg to find that out. Even with a new subsonic model, one flop can mean a rapid financial death for the company.

There are plenty of other considerations outside of the factory floor and design rooms to consider - operating costs, the availability of qualified A&Ps to fix the thing, the parts network, the cost of the parts (if you buy a $15M plane, you're going to pay $15M plane prices for spares and overhauls). Insurance will surely take their pound of flesh for something that's A) a company's first product B) a new category, and C) supersonic. Finally, with the general public being decidedly anti-aviation, the noise profile of this plane might very well limit where it can fly in and out of. It's a basic matter of aeodynamics, and the same problem that the Concorde experienced almost 50 years ago.

They aren't going to address it because it isn't an actual problem that needs to be addressed. You have far, far more to worry about with radon gas seeping up through cracks in your own home's foundation than a trivially-higher amount of cosmic radiation plinking you for 2-3 hours. BTW, it's the density of a material which offers radiation protection, not solely whether it's a metal or not.