One Of The Most Amazing Endeavors Man Has Ever Undertaken Is The Explo

One of the most amazing endeavors man has ever undertaken is the exploration of space. A big part of the amazement is the complexity. Space exploration is complicated because there are so many interesting problems to solve and obstacles to overcome. You have things like: The vacuum of space Heat management problems The difficulty of re-entry Orbital mechanics Micrometeorites and space debris Cosmic and solar radiation Restroom facilities in a weightless environment And so on... But the biggest problem of all is harnessing enough energy simply to get a spaceship off the ground. That is where rocket engines come in. Rocket engines are on the one hand so simple that you can build and fly your own model rockets very inexpensively (see the links at the bottom of the page for details). On the other hand, rocket engines (and their fuel systems) are so complicated that only two countries have actually ever put people in orbit. In this edition of How Stuff Works we will look at rocket engines to understand how they work, as well as to understand some of the complexity. The Basics When most people think about motors or engines, they think about rotation. For example, a reciprocating gasoline engine in a car produces rotational energy to drive the wheels. An electric motor produces rotational energy to drive a fan or spin a disk. A steam engine is used to do the same thing, as is a steam turbine and most gas turbines. Rocket engines are fundamentally different. Rocket engines are reaction engines. The basic principle driving a rocket engine is the famous Newtonian principle that to every action there is an equal and opposite reaction. A rocket engine is throwing mass in one direction and benefiting from the reaction that occurs in the other direction as a result. This concept of throwing mass and benefiting from the reaction can be hard to grasp at first, because that does not seem to be what is happening. Rocket engines seem to be about flames and noise and pressure, not throwing things. So let's look at a few examples to get a better picture of reality: If you have ever shot a shotgun, especially a big 12 guage shot gun, then you know that it has a lot of kick. That is, when you shoot the gun it kicks your shoulder back with a great deal of force. That kick is a reaction. A shotgun is shooting about an ounce of metal in one direction at about 700 miles per hour. Therefore your shoulder gets hit with the reaction. If you were wearing roller skates or standing on a skate board when you shot the gun, then the gun would be acting like a rocket engine and you would react by rolling in the opposite direction. If you have ever seen a big fire hose spraying water, you may have noticed that it takes a lot of strength to hold the hose (sometimes you will see two or three firemen holding the hose). The hose is acting like a rocket engine. The hose is throwing water in one direction, and the firemen are using their strength and weight to counteract the reaction. If they were to let go of the hose, it would thrash around with tremendous force. If the firemen were all standing on skateboards, the hose would propel them backwards at great speed! When you blow up a balloon and let it go so it flies all over the room before running out of air, you have created a rocket engine. In this case, what is being thrown is the air molecules inside the balloon. Many people believe that air molecules don't weigh anything, but they do (see the page on helium to get a better picture of the weight of air). When you throw them out the nozzle of a balloon the rest of the balloon reacts in the opposite direction. Imagine the following situation. Let's say that you are wearing a space suit and you are floating in space beside the space shuttle. You happen to have in your hand a baseball. If you throw the baseball, your body will react by moving away in the opposite direction. The thing that controls the speed at which your body moves away is the weight of