You're on the fourth human mission to Mars, and you're told the Odyssey spacecraft designed to take you there will be the smoothest ride you'll ever take. It features a newly christened electric propulsion engine which was in the late stages of testing during the first three missions. The mission st arts and the spacecraft travels at a crawl, and you wonder if it's broken. A week goes by and you're now traveling at more than 400,000 kilometers (250,000 miles) per hour, and your mind is blown as to how fast you're going, how quickly that happened, and that this mission might be more awesome than you thought. ...read more read less