Comment by brazzy
It's very clearly not "beyond imagination". It doesn't require any fundamentally new technology.
It may well be beyond our ability to practically apply those technologies at the required scales and reliability levels, but that's hardly unimaginable.
Preventing cancerous damage from radiation is absolutely beyond our tech.
Unless you consider launching a lead-lined spaceship "within our tech."
The marsonauts won't die before reaching Mars, but their lifespans will be significantly shortened.