We've been to space and understood radiation for decades, we've known that any potential lunar colony would need radiation shielding for long term habitation and Mars as well, which as a nation we've planned on going to since the Apollo program was still flying.

You're making a false equivalency here, the aircraft has been around for decades we just don't have the financial backing in our space program to actually develop the technology. However, I can guarantee you that it's not as simple as "just make a big electric motor!" Or some enthusiast would have already done it.