At first we don't want 2 space stations spinning. We want 2 space crafts spinning and traveling to somewhere where we have enough gravity to survive (mars). All humans on one ship and cargo/return counter weight as other ship linked together by a tether and spinning for the travel duration.
But yeah we still need to lower the launch cost per kg to make it really feasible and super heavy launch vehicles which don't exist at all at the moment. Realistically we would want to launch 40+ tons directly to mars from earth (Falcon Heavy should be ~13 tons so we would need around 3x the power of that). We don't have anything with enough delta v to do that at the moment.
But yeah we still need to lower the launch cost per kg to make it really feasible and super heavy launch vehicles which don't exist at all at the moment. Realistically we would want to launch 40+ tons directly to mars from earth (Falcon Heavy should be ~13 tons so we would need around 3x the power of that). We don't have anything with enough delta v to do that at the moment.