On Tuesday (Sept. 27), billionaire entrepreneur Elon Musk outlined plans to get hundreds of people to Mars. But are those plans really feasible? 

Musk, who is founder and CEO of the private spaceflight company SpaceX, outlined a plan to build spacecraft that could each transport on the order of 100 people to the Red Planet. The plan would also include a giant new SpaceX rocket, spacecraft and support systems to help get those people to Mars (or destinations beyond). The even-longer-term goal that tops off Musk's vision is for humans alter Mars' atmosphere and environment to make the planet hospitable to life. 

The plan is ambitious in nearly every way, from the technology Musk presented to the time line on which he hopes to accomplish these goals, not to mention the funding that will be required. Even so, the experts we talked to said it doesn't seem impossible, or even unachievable.[Images: SpaceX's Interplanetary Transport for Mars Colonization]