title: US human spacefaring questioned.
authors: Eric
authors: E
authors: Hand
mesh_terms: D006801:Humans; D013026:Space Flight / Q000191:economics* / Q000295:instrumentation* / Q000639:trends; D018531:Spacecraft / Q000191:economics / Q000592:standards*; D014481:United States; D018557:United States National Aeronautics and Space Administration / Q000191:economics / Q000639:trends