Trump's Space Ambitions Are Too Big for One President

It is not the job of presidents to know the specifics of space exploration and its mind-bending physics, or to contemplate deeply the timescales and technology required for a high-stakes mission to another planet. But usually they have some sense of what’s remotely possible, and of what they’ve asked their space agency to do. In the spring of 2017, President Trump signed a significant piece of legislation about the future of NASA. The bill, among other things, reaffirmed a top priority for the American space program: Sending humans to Mars by the 2030s.