In line with the brutally simple philosophy that is going to be necessary to colonize Mars we have to exist making what appears to be negative aspects of space and making them into positive.

As long as we are in Stellar space we have abundant energy in Sunlight and in interplanetary space that is continuous.

In reality the universe is full of water though of course localized.

There is no friction in travel so the shape of the space craft is irrelevant - the space station could go to Mars

Just as the shape is irrelevant so is the size as there is no resistance in space.

The space shuttle is the most complex engineering structure in history - because it was restricted in size - in space all the functions can be given their required space - as set out in the modular design and as requires simplicity can reign.