The deployment of (a) tether(s) in space is not an easy thing and the worst which can happen is a slack tether. Using a tether to link the masses of the habitat to the last stage of the launcher in order to generate artificial gravity by centrifugal force resulting of the rotation of the couple, might therefore be a good idea but it is not obvious that we can succeed to make it operational. Nevertheless, creating artificial gravity in the habitat of the spaceship during the voyage seems to be a must for a successful inhabited mission to Mars.