Launch vehicle

From Wikipedia, the free encyclopedia

A launch vehicle or carrier rocket is a rocket used to send a payload into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure.^[1] 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.

Contents 1 Types of launch vehicles 2 Derivation and related terms 3 Orbital launch 4 Calendar of upcoming launches 5 References 6 See also

[edit] Types of launch vehicles

Expendable launch vehicles are designed for one-time use. They usually separate from their payload, and then break apart upon 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 and Falcon 1 are currently the only launch vehicles with reusable components.

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 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.

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 Space Alliance manufactures and launches the Delta IV. Many launch vehicles are considered part of a historical line of vehicles which share a name. For example, the Atlas V is the latest member of the Atlas rocket family.

[edit] Derivation and related terms

The term derives from the American term "Satellite Launching Vehicle".

In the English language, the phrase "carrier rocket" was also used, and is still used by some circles in Britain. A translation of that phrase is used in German and Russian. The US Air Force adopted the term Launch Vehicle because they thought the term "carrier rocket" sounded too navalised.

[edit] Orbital launch

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 20m long (longer still for hydrogen fuelled stages as hydrogen has low density), 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.

[edit] Calendar of upcoming launches

Main article: 2007 in spaceflight

Spaceflight Now maintains a "Worldwide launch schedule" listing upcoming launches.^[2]

[edit] References

[edit] See also

• List of human spaceflights
• List of launch vehicles
• List of spaceflights by year
• Rocket launch
• Space Exploration