[Moonman62]

Distance from Earth to Mars = 34,000,000 miles

...

And most of that distance would be covered in freefall.

[HonkyTonkMan]

Could we not make a comparison of sailing? The currents and wind carry our ship, but we need provision, a sturdy vessel, and skill to guide us safely.

Larger distance, more time, greater potential for problems.

[Secret Agent Man]

Theyd have to have rotating section for gravity. They cant do well otherwise.