SLS and Starship are two kinds of starships that are now being used to bring men to the moon and Mars. But I have to say that I can see the importance of settling on Mars, but I would rather if mankind could go to the stars. In any way is that possible? Well, there is no way of knowing until the Physics is clear. Faster than light is out. So what is left is a Einstein-Rosen bridge [Worm Hole].
How could you get this? The only way is through string theory--branes. String theory needs to be clearer in order to see if branes can do something like that. Branes are funny kinds of things because they are in fact like strings, but in other ways not like strings. That is they are not under space time. They are in space time just like strings. But things in space time can effect space time. For example Gravity. Another example is the Aahronov Bohm effect that effects easily the nature of empty space easily and simply. [Just put a solenoid near the path of a charged particle. It effects the very nature of empty space.]
See this paper by
Tentyukov printed in Russia which discusses a worm hole that is possible to transverse. That is when the metric is not flat.