National Geographic video on Rockets
JONNY PHILLIPS Of all the different methods of propulsion invented by mankind, for pure, unadulterated, heart stopping excitement nothing really compares to rockets.
RICHARD AMBROSE: OK - I am about to initiate the launch sequence. Now stand right back and witness the explosive power of rocketry. Whoa!
JONNY PHILLIPS (SYNC - TO RICHARD): Um - I think we're gonna need bigger rockets, don't you?
NARRATOR: Well boys, how about the biggest rocket of all time? Imagine 50 jumbo jets at full power, strapped to a 36 storey building. That's Saturn 5.
It takes something like this to catapult man to the moon. But where does the colossal thrust actually come from?
RICHARD AMBROSE (PTC): Inside a rocket motor fuel is turned into gas through combustion and the gas is then forced out the back. And the reason why escaping gas pushes a rocket forward is explained by Newton's Third Law of Motion.
JONNY PHILLIPS (PTC): Which is, as I'm sure you'll remember from school, that every action has an equal and opposite reaction.
RICHARD AMBROSE (PTC): That's the theory but what we need is a practical demonstration. Now as Jonny opens the valve on this pressurized gas canister the air will rush out but at the same time an equal and opposite force will propel it this way. Go on Jonny - open it up.
JONNY PHILLIPS (PTC): So there you have it. The basics of rocketry. Well what did you expect? It's not rocket science.
NARRATOR: The rocket's launch speed does not depend on the astronaut flooring the throttle but on how quickly the gas escapes from the exhaust.
Space rocket exhausts are hour glass shaped because gas flows at an accelerated rate if it's forced through a narrow section into a wider end.
NARRATOR: The exhaust is crucial no matter what the size of the rocket.