launch vehicle(redirected from launch vehicles)
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launch vehicleAny system by which the necessary energy is given to a satellite, spaceprobe, etc., in order to insert it into the desired orbit or trajectory. Expendable multistage launchers were used originally, and are still being used and developed: ESA's Ariane and NASA's Titan and Delta families are examples. The reusable space shuttle was developed by NASA so that recovery of the vehicle is possible.
Rocket propulsion is a form of jet propulsion: all the propellant is carried in the vehicle at take-off and the hot combustion gases, resulting from the mixture of fuel with reactant, are ejected at high speed through a nozzle to produce the necessary force – termed thrust – to lift the vehicle off the ground. Modern launchers generally consist of two, three, or four stages; the final stage carries the spacecraft into the desired orbit, the satellite separating from the stage when orbital velocity is reached. There are design variations in the type of propellant used, which may be either solid or liquid, the means of carrying the propellant, and the process by which the tanks, etc., are discarded.
a multistage (two- to four-stage) rocket used to lift artificial earth satellites, unmanned space probes, manned spacecraft, orbital stations, and other payloads into space. Depending on the performance characteristics and the capability of injecting a payload of a given weight into orbit, launch vehicles can be classified as light (up to 500 kg), medium (up to 10 tons), heavy (up to 100 tons), and extra heavy (more than 100 tons). Most launch vehicles are based on intercontinental or intermediate-range ballistic missiles.
The fuel components generally used in the first stage of a launch vehicle are kerosine and liquid oxygen; this combination is used in the Vostok (USSR) and the Atlas-Agena (USA) rockets. The liquid-propellant rocket engines of the upper stages usually operate on high-energy fuels; examples are the Cosmos (USSR), the Atlas-Agena (USA), and the Titan 2 (USA) rockets. The upper stages may also operate on liquid hydrogen and liquid oxygen, as do the Atlas-Centaur and the Saturn 5 (USA) rockets.
A distinctive feature of the final stages of some launch vehicles is the possibility of restarting their engines; this permits maneuvering to change the altitude and inclination of the orbit and to launch a payload from an earth orbit. In addition to liquid-propellant rocket engines used as the main engines in the majority of launch vehicles, solid-propellant booster engines are sometimes attached to the first-stage housing, as in the case of the Thrust-Augmented Thor-Agena (USA) rocket.
Payloads ranging in weight from several kg to several tens of tons can be placed in circular earth orbits with the required velocity using launch vehicles. All launch vehicles are characterized by a relatively small weight and a large fuel capacity (the weight of the fuel is between 85 and 90 percent of the rocket’s launch weight). The launch weight ranges from several tens of tons up to several thousand tons. The duration of the powered flight trajectory of some launch vehicles is more than 17 min. The flight covers a wide altitude range.
G. A. NAZAROV