NASA weighing risk of adding crew to megarocket's 1st flight
The space agency's human exploration chief said Friday that his boss and the Trump administration asked for the feasibility study.
Under that plan, Gerstenmaier said, nearly three years are needed between an unmanned flight test and a crewed mission to make launch platform changes at Kennedy Space Center.
NASA normally prefers testing rockets without people, although for the inaugural space shuttle flight in 1981, two pilots were on board.