Early attempts to build Space Colonies faltered for two reasons: cost of construction and risk to Earth. Conventional rockets couldn't carry the necessary materials, making the cost of building astronomical. Also, if a city fell into the atmosphere, its enormous battery system could disintegrate over populated areas, killing thousands. Smart Materials and Fuel Cells reduced the cost and risk of both, and the human experience with Arcologies was a great help with the design. Although still costly, space colonization moved forward, supported by wealthy individuals (looking for a new escape) and the military.