In this second in a series of programs on space exploration, Francis Clauser discusses how Newton's third law explains the propulsion of rocket ships. Speeds of over 25,000 miles per hour are needed to escape the earth's atmosphere and 16,000 miles per hour to put a rocket in orbit around the earth. Fuels that can be used to propel rockets include hydrazine and nitric acid. A model of a three stage rocket is shown to demonstrate how man will begin space travel.