It's Just Rocket Science - Part 1
A look at the basic principles of rocketry
In its simplest form, a rocket is just a flying container of fuel open on one end to give a controlled flight.
There are three basic parts to a rocket: the fuselage, or exterior shell of the rocket, the fuel, and an optional payload. In a shuttle mission, the payload is the shuttle itself. It is assisted into orbit by three other detachable, reusable rockets. In an intercontinental ballistic missile (ICBM), the payload is a nuclear warhead or other high-explosive device. A rocket also requires an ignition source to start the burn of fuel.
The bulk of a rocket will generally be its fuel, and one of the major engineering problems of rocketry is containing burning fuel so that it burns steadily and doesn't blow up the entire fuselage. When rockets fail, it is most often because some component of the fuel containment system failed.
The fuel itself can be a liquid or a solid and can be anything combustible. For instance, the shuttle uses liquid hydrogen and oxygen. The clouds of exhaust that you see when the shuttle takes off is just water vapor. The fuel in a rocket contains a lot of potential energy in the form of chemical energy, and when it is burned, the potential energy is transformed into kinetic energy, the energy of motion.
Once the fuel is ignited, the rocket is launched, and will follow trajectory that will almost always take the shape of a parabola (like an upside-down dish). In the absence of Earth's gravity, it would take very little energy to propel the rocket in a straight line indefinitely, but on Earth, the rocket must accelerate to travel any appreciable distance. If a rocket is going to break free of the grip of Earth's gravity, it must achieve escape velocity - it must accelerate until it is traveling at least 25,000 miles per hour.
If the rocket is pointed straight up, and there are no other forces (such as wind) acting on the rocket besides gravity and air friction (which pull and push down on the rocket respectively), the rocket will either travel away from the Earth if it reaches escape velocity, or it will fall straight back down after a time. Technically, this trajectory is still a parabola. If the rocket is aimed slightly off the vertical, either pointed in a direction at launch and does not reach escape velocity, it will travel in a parabola until it lands. The closer to the horizontal the rocket is directed, the shallower the parabola.
Next week, we'll examine factors that make rocket flight more complex.
