The diagram below is from NASA Publication SP-413, Space Settlements: A Design Study. Here is a quote from page 175: “An upper limit to the speed of growth of space colonization is estimated by assuming 3 years for the duplication of a habitat by a workforce equivalent to 12 percent of a habitat’s population. Only 56 years are required at this rate for the construction of communities in space adequate to house a population equal to that of the Earth today.”
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