In the first generation of liquid-propellant rockets, the nose cone carries the payload, which consists of either a warhead or scientific instruments. The section adjacent to the nose cone usually contains such guidance equipment as a gyroscope or gyrocompass, accelerometers, and a computer. Next to this section are the two main tanks, one holding the fuel and the other the oxidizing agent. If the size of the liquid-propellant rocket is comparatively small, both the fuel and the oxidizer can be forced into the rocket motor by pressurizing the propellant tanks with an inert gas. For large rockets this method is not practical, because the tanks would be disproportionately heavy. In large liquid-propellant rockets, therefore, the required delivery pressure is produced by pumps, situated between the tanks and the rocket motor. Because the quantities of propellants to be pumped are very large (even the V-2 rocket burned 127 kg/280 lb of propellants per sec), the pump required is a high-capacity centrifugal pump driven by a gas turbine. The assembly, consisting of the gas turbine with its auxiliary fuels, the pumps, and the rocket motor and its related equipment, constitutes the so-called rocket engine of a liquid-propellant rocket.
Rocket Nozzles
High-performance rocket engines, such as those used in space vehicles operating in near-vacuum conditions, require very large nozzles to reach supersonic jet-exit velocities. The nozzle must have a converging section from the combustion chamber to the narrowest portion, called the throat, at which sonic velocity is reached, followed by a diverging passage. The nozzle exit diameter may be four or five times the diameter of the combustion chamber.
