Rocketry Basics

A Basic Introduction to Rocketry

What is a rocket?

• A rocket in its simplest form is just a chamber with a gas under pressure.

• A small opening at one end of the chamber allows the gas to escape, and when it does, it propels the chamber foward. – A good example of this is a balloon. Air

inside a balloon is compressed by the balloon’s rubber walls which causes air pressure. When the end of the balloon is released, air escapes through it and the balloon goes in the opposite direction.

Rockets are balloons?• When we think of rockets, we don’t really

think of balloons. • Instead, we think of the giant vehicles that

carry satellites and spacecraft into space, but they have a lot in common.

• The only major difference is the way the pressurized gas is made. – In balloons, the rubber walls compact the

gas, making pressure– In space rockets, the gas is made by

burning propellants that can be solid or liquid in form or a combination of the two.

Types of Rockets

• There are several types of rockets. These include:– Missiles (for military use)– Space Vehicles (both manned and

unmanned)– Sounding Rockets (suborbital, research,

and weather)– Amateur (model rockets)

Stages of Rocket Flight

• Preparation• Ignition and Liftoff• Powered Ascent• Coast• Recovery System

Deployment• Descent• Recovery

Movement of the Rocket• What causes a rocket to move?

– Newton’s Third Law of Motion: For every action there is an equal and opposite reaction

• Rocket motor = energy conversion device– Gases are stored in the combustion chamber until

enough pressure builds up to force some gasses out of a nozzle.

• Thrust is made by how much pressure is built up and how much gas shoots out of the nozzle

• The shape of the combustion chamber, the shape of the nozzle

Movement of Rockets Cont’d

• Chinese fire arrows were not very reliable.– Most of the time, they blew up when launched.– The ones that did launch went on crazy paths

and most of the time did not land where they were supposed to.

• Modern rockets have propellants that are more reliable.

• Propellants are not just the fuel. They are the fuel and the oxidizer. – The fuel is the substance that burns but for

burning to take place, there must be an oxidizer (oxygen)

Movement of Rockets cont’d

• No matter which type of rocket, a nozzle is used for the escaping matter.

• The more weight (mass) that the rocket has, the more thrust (force) is needed to lift it off the ground. – Liquid rockets are easier to control the thrust.– They use computers in the rocket’s guidance

system. The computers control the amount of propellant that goes into the combustion chamber (and out of the rocket).

Payloads are anything that the rocket is carrying. This can be people,

satellites, fireworks, warheads, or anything else.

Solid Propellant Rockets

• Solid propellants are solid and dry. • They contain both the fuel and oxidizer

combined together in the chemical itself. • Usually the fuel is a mixture of hydrogen

and carbon and the oxidizer is oxygen compounds

Solid Propellant Rockets cont’d

• The parts of a solid propelled rocket are simple. – nozzle: where the gases escape– case: usually a relatively thin metal that is

lined with insulation to keep the propellant from burning through

– insulation: the propellant itself is packed inside the insulation layer

– propellant: solid mixture of hydrogen, carbon, and oxygen.

– igniter: what is lit to cause the burning of the propellant.

Liquid Propellant Rockets

• The other type of rocket is a liquid propellant rocket. – The fuel and the oxidizer are kept in

separate tanks until they are ready to be launched.

– They are forced into the combustion chamber.

– There, they ignite and liftoff occurs.

Liquid Propellant Rockets cont’d

• Liquid propellant rockets have a few more parts than solid rockets. – oxidizer and fuel tanks: hold the materials

until they are ready to be mixed.– pumps: pump the oxidizer and fuel into the

combustion chamber.– combustion chamber: where the fuel and

oxidizer are mixed.