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Understanding the Delta II Rocket
 
Delta II Rocket Component Definitions

Composite Payload Fairing - The payload fairing is used to encapsulate, or surround, the spacecraft to protect it from temperature, humidity, contamination and wind as the rocket climbs toward orbit. The fairing is released at the fringes of the atmosphere to expose the spacecraft to space in preparation for placing the spacecraft in the proper orbit. Composite is a description of the material used to build the fairing.

Avionics - The avionics is the electrical "brain" of the rocket. Avionics are electrial systems that control the rocket during flight.

Isogrid Fuel Tank - The first stage fuel tank is the structure containing RP-1, the fuel, for the first stage which is mixed with the liquid oxygen (LOX) to run the main engine. Isogrid is a description of the structure of the internal part of the tank.

Isogrid First-Stage Liquid Oxygen Tank - The first-stage liquid oxygen (LOX) tank is the structure containing the oxidizer for the first stage which is mixed with the fuel to run the main engine. Isogrid is a description of the structure of the internal part of the tank.

Graphite Expoxy Motors (GEM) - The graphite epoxy motors are the solid rocket motors attached to the first stage. These motors help propel the entire rocket along with the main engine. When nine motors are used, six are started at T-0. When they run out of solid propellant they are jettisoned from the rocket and at the same time the remaining three motors ignite and assist the first stage in getting the rocket to the predetermined altitude mentioned above in the main engine explanation. The reason they are called graphite epoxy motors is because that is the material used to build the motor casings. The motors are lighter and stronger than aluminum.

RS-27A Engine - This is the first stage engine that begins operation at T-0 (launch). This is why it is called the main engine. It is used to carry the entire rocket to a predetermined altitude, along with the solid rocket motors, before shutting down, allowing the first stage to separate from the second stage. The engine uses liquid oxygen and RP-1, a fuel, mixed together to run the engine.
 
 
NASA's John F. Kennedy Space Center