(snip) a cryptic startup called SpinLaunch starts suborbital test flights of a rocket that is launched using an enormous centrifuge. Here's the gist: A centrifuge the size of a football field will spin a rocket around in circles for about an hour until its speed eventually exceeds 5,000 miles per hour. At that point, the rocket and its payload will feel forces 10,000 times stronger than gravity. When the centrifuge finally releases the rocket at launch speed, it should, practically speaking, fly through the stratosphere until it fires its engines at the periphery of our atmosphere. (snip) SpinLaunch hopes its...