# The History Of Space Travel

## The history of space travel. We have gone from the throw away rocket to the now reusable shuttle. I talk about what a rocket really is and how they work.

Rockets are the only engines that can operate in the near emptiness of outer space. This is why rockets can be used to propel spacecraft from the earth to the moon, from the planets to the stars. The modern rocket can travel faster than any vehicle.

When you think of a rocket, you are most likely thinking of the bullet shaped space ship that goes soaring through space. But, a rocket is, in fact, the name for the engine. Rockets can supply the power to anything that needs to be propelled. It can launch a space craft, and automobile, a missile, or even a boat.

The simplest explanation of a rocket would be a tube of fuel closed at one end and open at the other. When the fuel burns it is turned into a gas. The hot gas expands and then pushes outward in all directions. In the rocket. The expanding gas will come out the open end. The rushing gas then will cause the container to move in the opposite direction. The faster the gas comes out, the faster the container will move.

The way a rocket works can most easily be explained by Isaac Newton's three laws of motion.

In Newton's third law he talks about the force that gives the rocket power. The law quite simple states that for every action there is an equal reaction in the opposite direction. An example for this would be paddling a canoe: The paddle pushes the water backwards, while the canoe is pushed forward.

Once a rocket is launched, its speed will increase as long as it's engines fire. This is explained by Newton's second law: Acceleration depends on the amount of force applied. The greater the force--the faster the rocket.

Newton's first law is called the law of inertia. It says that an object that is not moving will not--unless it is acted upon by dome outside force. In launching a rocket, force has to be applied to overcome inertia.

Rockets do not need air to fly like and airplane does. In fact, it will work better in outer space where there is no air. Air creates friction against the rocket and slows it down. At higher altitudes the air gets thinner. In outer space there is almost no friction to slow the rocket down.

Rockets do well in outer space for another reason. To burn, fuel must combine with a chemical called oxidizer. Oxygen is the most common oxidizer. There are large amounts of oxygen in the air. An airplane takes in oxygen and uses it to burn its fuel. A rocket, on the other hand, carries its own oxidizer in liquid or solid form; inside their cases. They do not need to rely on oxygen from the air.

If we want a rocket to go fast, we must make sure its engines are operational long enough for it to get to the proper speed. This can take several minutes. That will depend mostly on the weight of the rocket. For this reason, the weight of the rocket shell must be keep down as much as possible.

To keep weight down, light weight metals and strong light weight plastics must be used in the shell. When the fuel tanks are empty, the pressure must be maintained inside the rockets. If it is not, they would collapse and break. When fuel is in the tanks, the pressure of the fuel and oxidizer is what keeps the rocket rigid.

There are two types of rocket fuel, liquid and solid. The mixture of fuel and oxidizer is called propellant. The rocket engineer is the one who chooses the propellant. This will be chosen based on the job the rocket has to do. Liquid propellants would be used if the rocket needs exceptional power. Solid propellants would be used for longer flights.

When the rocket is launched, the fuel must be ignited. There are several different ways that this can be done. In every method, the ignition has to take place inside the rocket engine.

A single rocket could be built to carry payloads into space. This, however, would not be very efficient or economical. The weight of the fuel and the fuel tanks would be too much. An enormous thrust would be needed to lift this rocket and accelerate it to the correct speed.

A rocket needs most of its thrust during lift off in order to over come it's inertia. Once it is started, the rocket becomes much lighter as its propellants are burned. What that means is that there is a constant decrease in the amount of weight that the thrust must accelerate. Because of this, the rockets will gain speed very fast.

It takes just a few seconds after flight for a rockets fuel tanks to no longer be full. The tanks themselves are really very heavy. These empty tanks are now an unnecessary weight for the rocket shell.

Engineers have solved the problem of this unneeded weight after take off. They mount one or more rockets on the top of each other. The smallest rocket is on top and the largest, of course, on the bottom.

The bottom rocket is the main launch rocket. The method of stacking rockets is called staging. Each rocket being called a stage. Each stage has its own engine and propellants. The combination of stages is called a multistage rocket. The launching rocket is called the first stage or the booster. The next stage is called the second stage, and on to the final or upper stage.

The booster is dropped as soon as it has used up all of its fuel. This usually takes place within the first two minutes. It is now that the engines of the second stage begins to fire. When it burns up its fuel, it too is released, and the engines of the third stage begin to fire.

Each stage is lighter and lighter in weight than the one before it. As the stages go, they carry less fuel as it needs less thrust to accelerate. Each stage goes faster than the one before it. The last stage will go the furthest and the fastest.

Most rockets are used only one time. After they are launched, they fall back to earth after the fuel is used up. These are called expendable launch vehicles.

Today, though, the more advanced rockets return to earth safely. These rockets can be used again and again. This is the case with the space shuttle. It is the first manned, reusable rocket vehicle. The main part to this is the reusable orbiter. It looks somewhat like and airplane and is piloted by astronauts. The orbiter is mounted on a huge structure made up of a liquid propellant rocket and two recoverable solid propellant rockets.

After the solid propellant rockets use up all of their fuel, they drop away from the orbiter and fall back to earth. They are brought down with the use of parachutes. These rockets fall into the ocean and are then recovered to be used again.

Because both the orbiter and the solid propellant rocket can be reused so many times, the shuttle is the most economical way to get payloads into outer space.