You see in the picture that the sleeping quarters (crew quarters) have a layer of blue around them- thats water, and water is a very good radiation shield. Thats just one idea. There are many ways to protect yourself from radiation, its just a matter on finding the method that weighs the least.

Uh, understand that they don’t have 2 years to produce an actual habitat that will fly, merely a “prototype.” That’s very vague and could be as basic as a wood and foam model. Its basically working on concepts that would work for a habitat that would eventually could be used for deep space travel.