ASTR 101 Lecture Notes - Lecture 13: Rocket Sled, Escape Velocity, Weightlessness
14 Apr 2016
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In the last unit we learned how we can calculate the orbits of objects moving under the influence of gravity. We"re now going to apply that to various circumstances. We start with a very simple definition: an object is said to be moving. Ballistically" if it moves only under the influence of gravity: no rockets firing, no air resistance, or any other force. To create ballistic motion, we need to set something in motion quickly and then eliminate the driving force. An example would be throwing a stone into the air: when it leaves your hand it is now moving ballistically if we can ignore air resistance. A rocket that is launched will be moving ballistically as soon as the motors or engines shut off. In the cold war, the big fear was intercontinental ballistic missiles, here"s a map showing the presumed russian forces of icbms at that time.
