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This is more of a question than an opinion - This has always been something that I never could understand. You see any Hollywood (or other) movies concerning Mars exploration and the 'ship' always has nuclear engines and a rotating crew compartment to provide SG. Other than expense - which would be significant - why can this not work. Also, other than the aforesaid expense, why was the ISL built in its present form and not as a rotating wheel a la 2000AD! Was/is it just a matter of money or were there tech. reasons?