re: The void between the Earth and Mars
You would plan around the unknowns with several unmanned ERVs and HABs missions to Mars before sending anything with humans in it. This would give you several "safe" structures for a failure of some major part of your HAB while on the surface of Mars. You would also use all means to protect your spacecraft on the way there and back against radiation and some tether system would be used a well to reduce the bone loss issues found with zero-gee.