On the USA Science and Engineering Festival blog, astronaut John Grunsfeld describes what it's like to rocket into space. Astronauts first spend two hours strapped in on the launchpad, "flipping switches and thinking about our training and the jobs we have to do." They count down to ignition, mindful of the 4.5 million pounds of explosive in the fuel tanks. After liftoff, the shuttle accelerates out of Earth's atmosphere in less than nine minutes, causing each astronaut to feel like they weigh 700 pounds. An instant later, they are weightless. On Starts With a Bang, Ethan Siegel shares…
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