There are people out there who know more about these things than we armchair theorists.
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U.S. astronaut Scott Kelly is a veteran of four space flights. He holds the record for total accumulated days in space, as well as for the longest single mission by an American: a full year aboard the International Space Station (ISS). He clearly knows a thing or two about what's possible in the realm of space flight, and he just told the world he doesn't doubt Elon Musk.
"When Elon Musk said he was going to launch his rocket and then land the first stage on a barge, I thought he was crazy" Kelly said on Tuesday. "And then he did it. I'm not going to ever doubt what he says, ever again."