I talked a few years ago with a Hungarian well known phisicist (I'm not allowed to tell anyone his name because ge is afraid of the possible"fallout") who worked back then with the Russians in the space race. When he was in Russia he talked with the best Russian scientists and they all said that this was not possible on multiple levels. I only remember on few things:

1. The rocket cannot fly with the required amount of fuel to make such a trip.

2. The space radiation (when you leave the Earth magnetic protection) would kill the astronauts in not years, but possible months.

I don't remember well, but maybe they said that to protect the crew from radiation you would need a few meters of lead shield which weight would be enormous.

There were few others, but I don't remember well, so I would not write it down.