Launch vehicle

Launch vehicle

By Wikipedia,
the free encyclopedia,

http://en.wikipedia.org/wiki/Launch_vehicle

A Saturn V launch vehicle sends Apollo 15 on its way to the moon.

In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure. Usually the payload is an artificial satellite placed into orbit, but some spaceflights are sub-orbital while others enable spacecraft to escape Earth orbit entirely. A launch vehicle which carries its payload on a suborbital trajectory is often called a sounding rocket.

Types of launch vehicles

Ukrainian LV Zenit-2 is prepared for launch

Expendable launch vehicles are designed for one-time use. They usually separate from their payload, and may break up during atmospheric reentry. Reusable launch vehicles, on the other hand, are designed to be recovered intact and used again for subsequent launches. For orbital spaceflights, the Space Shuttle is currently the only launch vehicle with components which have been used for multiple flights.

Launch vehicles are often characterized by the amount of mass they can lift into orbit. For example, a Proton rocket has a launch capacity of 22,000 kg (48,500 lbs.) to low Earth orbit (LEO).

Launch vehicles are also characterized by the number of stages they employ. Rockets with as many as five stages have been successfully launched, and there have been designs for several single-stage-to-orbit vehicles. Additionally, launch vehicles are very often supplied with boosters. These supply high thrust early on in the flight in parallel with other engines on the vehicle. Boosters allow the remaining engines to be smaller which reduces the stages burnout mass and thus allows for bigger payload.

Other frequently-reported characteristics of launch vehicles are the nation or space agency responsible for the launch, and the company or consortium that manufactures and launches the vehicle. As examples, the European Space Agency is responsible for the Ariane V, and the United Launch Alliance manufactures and launches the Delta IV. Many launch vehicles are considered part of an historical line of vehicles which share a name. For example, the Atlas V is the latest member of the Atlas rocket family.

Non-rocket spacelaunch‎ alternatives are at the planning stage.

Vehicle assembly

Various methods, each with specialized equipment, are used to get an assembled launch vehicle on its launch pad. In some launch systems, like Delta II, the vehicle is assembled vertically on the pad, using a crane to hoist each stage into place. The Space Shuttle orbiter, external tank, and solid rocket boosters are assembled vertically in the Vehicle Assembly Building and then a special crawler-transporter moves the entire stack upright to the launch pad. The Soyuz rocket is assembled horizontally in a processing hangar, transported horizontally, and then brought upright once at the pad.

These assembly activities take place as part of the overall launch campaign for the vehicle.

Derivation and related terms

The term derives from the American satellite program, Project Vanguard, as a contraction of the phrase "Satellite Launching Vehicle" abbreviated as "SLV" as a term in the list of what the rockets were allocated for: flight test, or actually launching a satellite. The contraction would also apply to rockets which send probes to other worlds or the interplanetary medium.

In the English language, the phrase carrier rocket was used earlier, and still is in some circles in Britain. A translation of that phrase is used in German, Russian, and Chinese. The U.S. Air Force detested the term carrier, which would refer to their competition, the aircraft carriers of the U.S. Navy. For this reason they called one airplane which carried another a conveyor.

Suborbital launch vehicles

Current suborbital launch vehicles include SpaceShipOne.

Orbital Launch vehicles

Orbital launch

A Soyuz lifts off from the Baikonur Cosmodrome in Kazakhstan heading for the ISS

The delta-v needed for orbital launch is generally between 9300 and 10,000 m/s, although there is no upper limit.

The delta-v needed can be considered to be a combination of air-drag (determined by ballistic coefficient), gravity losses, altitude gain and the horizontal speed necessary to give a suitable perigee.

Minimising air-drag means having a reasonably high ballistic coefficient which generally means having a launch vehicle about 10-20m long (longer still for hydrogen fueled stages as hydrogen has low density), as well as leaving the atmosphere early on in the flight, giving an air drag of around 300 m/s.

The horizontal speed necessary is around 7800 m/s..

The delta-v for altitude gain varies, but is around 2 km/s for 200 km altitude.

The calculation of the total delta-v for launch is complicated and in nearly all cases numerical integration is used; adding the delta-v's gives a pessimistic result since the rocket can thrust at an angle to reach orbit, which saves fuel as it can gain altitude and horizontal speed simultaneously.

Regulation

Under international law, the nationality of the owner of a launch vehicle determines which country is responsible for any damages resulting from that vehicle. Due to this, some countries require that rocket manufacturers and launchers adhere to specific regulations to indemnify and protect the safety of people and property that may be affected by a flight.

In the US any rocket launch that is not classified as amateur, and also is not "for and by the government," must be approved by the Federal Aviation Administration's Office of Commercial Space Transportation (FAA/AST), located in Washington, DC

Calendar of upcoming launches

Spaceflight Now maintains a "Worldwide launch schedule" listing upcoming launches.