No, the biggest hurdle is having astronauts survive the journey (health and successful landing/departure of Mars). It would be over 3 years in space to round trip to Mars with current tech. We haven't had an astronaut in space continuously over ~1 year...the body suffers tremendously in a low gravity environment and you would have to handle SO many side effects and redundancies in life support etc.
Artificial gravity would address those issues. The big rocket (ie mass margin) also addresses life support redundancies (and allows you to use simpler, much more reliable methods like used on short duration spaceflights).
Yes, and we have never built artificial gravity and tested it in space, much less its effects on the body. I think this validates how rocket tech is not the limiting factor on reaching Mars.
