This is a work of fiction: Since the invention of rockets, their propulsion systems have gone essentially unchanged. We still depend on blasting some type of propellant out the rear to shoot the rocket forward (Newton’s Third Law – check it out). There’s two problems with this method: propellant is always in limited supply, and you can’t really go very fast, so we use gravitational assist from planets to get us places. It still takes years, and that’s just inside our solar system. What if we could go to our Moon in hours or Mars in a couple days, and even turn around mid-flight if we forgot our toothbrush?
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It continues in this vein for almost another 500 words.