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In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad, and other infrastructure. Although a carrier rocket's payload is often an artificial satellite placed into orbit, some spaceflights are sub-orbital, while others enable spacecraft to escape Earth orbit entirely. A launch vehicle used for a sub-orbital flight is often called a sounding rocket.
Types of launch vehicles
Expendable launch vehicles are designed for one-time use. They usually separate from their payload and disintegrate during atmospheric reentry. In contrast, reusable launch vehicles are designed to be recovered intact and launched again. The Space Shuttle was the only launch vehicle with components used for multiple orbital spaceflights. SpaceX is developing a reusable rocket launching system for their Falcon 9 and Falcon Heavy launch vehicles. A second-generation VTVL design was announced in 2011. The low-altitude flight test program of an experimental technology-demonstrator launch vehicle began in 2012, with more extensive high-altitude over-water flight testing planned to begin in mid-2013, and continue on each subsequent Falcon 9 flight. Non-rocket spacelaunch alternatives are at the planning stage.
Launch vehicles are often classified by the amount of mass they can carry into orbit. For example, a Proton rocket can lift 22,000 kilograms (49,000 lb) into low Earth orbit (LEO). Launch vehicles are also characterized by their number of stages. 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 supplying high early thrust, normally burning with other engines. Boosters allow the remaining engines to be smaller, reducing the burnout mass of later stages to allow larger payloads.
Other frequently-reported characteristics of launch vehicles are the launching nation or space agency and the company or consortium manufacturing and launching the vehicle. For example, the European Space Agency is responsible for the Ariane V, and the United Launch Alliance manufactures and launches the Delta IV and Atlas V rockets. Many launch vehicles are considered part of a historical line of vehicles of same or similar name; e.g., the Atlas V is the latest Atlas rocket.
By launch platform
- Land: spaceport and fixed missile silo (Strela) for converted ICBMs
- Sea: fixed platform (San Marco), mobile platform (Sea Launch), submarine (Shtil', Volna) for converted SLBMs
- Air: aircraft (Pegasus, Virgin Galactic LauncherOne, Stratolaunch Systems), balloon (ARCASPACE), JP Aerospace Orbital Ascender, proposal for permanent Buoyant space port
There are many ways to classify the sizes of launch vehicles. The US civilian space agency, NASA, uses a classification scheme that was articulated by the Augustine Commission created to review plans for replacing the Space Shuttle:
- A sounding rocket cannot reach orbit and is capable of sub-orbital spaceflight
- A small lift launch vehicle is capable of lifting up to 2,000 kg (4,400 lb) of payload into low earth orbit (LEO)
- A medium lift launch vehicle is capable of lifting between 2,000 to 20,000 kg (4,400 to 44,100 lb) of payload into LEO
- A heavy lift launch vehicle is capable of lifting between 20,000 to 50,000 kg (44,000 to 110,000 lb) of payload into LEO
- A super-heavy lift vehicle is capable of lifting more than 50,000 kg of payload into LEO
The leading European launch service provider, Arianespace, also uses the "heavy-lift" designation for its >20,000 kg (44,000 lb)-to-LEO Ariane 5 launch vehicle and "medium-lift" for its array of launch vehicles that lift 2,000–20,000 kg (4,400–44,100 lb) to LEO, including the Starsem/Arianespace Soyuz ST and pre-1999 versions of the Ariane 5. It refers to its 1,500 kg (3,300 lb) to LEO Vega launch vehicle as "light lift".
Each individual stage of a rocket is generally assembled at its manufacturing site and shipped to the launch site; the term vehicle assembly refers to the mating of rocket stage(s) with the spacecraft payload into a single assembly known as a space vehicle. Single-stage vehicles (such as sounding rockets), and multistage vehicles on the smaller end of the size range, can usually be assembled vertically, directly on the launch pad by lifting each stage and the spacecraft sequentially in place by means of a crane.
This is generally not practical for larger space vehicles, which are assembled off the pad and moved into place on the launch site by various methods. NASA's Apollo/Saturn V manned Moon landing vehicle, and Space Shuttle, were assembled vertically onto mobile launcher platforms with attached launch umbillical towers, in the Vehicle Assembly Building, and then a special crawler-transporter moved the entire vehicle stack to the launch pad in an upright position. In contrast, vehicles such as the Russian Soyuz rocket and the SpaceX Falcon 9 are assembled horizontally in a processing hangar, transported horizontally, and then brought upright at the pad.
As an alternative, Project Vanguard provided a contraction of the phrase "Satellite Launching Vehicle" abbreviated to "SLV". This provided 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.
Orbital launch vehicles
Sounding rockets are normally used for brief, inexpensive space and microgravity experiments. Current human-rated suborbital launch vehicles include SpaceShipOne and the upcoming SpaceShipTwo, among others (see space tourism). The delta-v needed for orbital launch using a rocket vehicle launching from the Earth's surface is at least 9,300 m/s (31,000 ft/s). This delta-v is determined by a combination of air-drag, which is determined by ballistic coefficient as well as gravity losses, altitude gain and the horizontal speed necessary to give a suitable perigee. The delta-v required for altitude gain varies, but is around 2 km/s (1.2 mi/s) for 200 km (120 mi) altitude.
Minimising air-drag entails having a reasonably high ballistic coefficient, which generally means having a launch vehicle that is at least 20 m (66 ft) long, or a ratio of length to diameter greater than ten. Leaving the atmosphere as early on in the flight as possible provides an air drag of around 300 m/s (980 ft/s). The horizontal speed necessary to achieve low earth orbit is around 7,800 m/s (26,000 ft/s).
The calculation of the total delta-v for launch is complicated, and in nearly all cases numerical integration is used; adding multiple delta-v values provides a pessimistic result, since the rocket can thrust while at an angle in order to reach orbit, thereby saving fuel as it can gain altitude and horizontal speed simultaneously.
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[which?] countries require that rocket manufacturers and launchers adhere to specific regulations in order 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.
Specific to launch vehicles
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- See for example: "NASA Kills 'Wounded' Launch System Upgrade at KSC". Florida Today.
- "SpaceX says 'reusable rocket' could help colonize Mars". Agence France-Presse. Retrieved 4 October 2011.
- "Elon Musk says SpaceX will attempt to develop fully reusable space launch vehicle". Washington Post. 2011-09-29. Retrieved 2011-10-11. "Both of the rocket’s stages would return to the launch site and touch down vertically, under rocket power, on landing gear after delivering a spacecraft to orbit."
- Lindsey, Clark (2013-03-28). "SpaceX moving quickly towards fly-back first stage". NewSpace Watch. Retrieved 2013-03-29. (subscription required (. ))
- there are no Russian roadless terrain or railway car based mobile launchers converted for spacecraft launches.
- NASA Space Technology Roadmaps - Launch Propulsion Systems, p.11: "Small: 0-2t payloads, Medium: 2-20t payloads, Heavy: 20-50t payloads, Super Heavy: >50t payloads"
- HSF Final Report: Seeking a Human Spaceflight Program Worthy of a Great Nation, October 2009, Review of U.S. Human Spaceflight Plans Committee, p. 64-66: "5.2.1 The Need for Heavy Lift ... require a “super heavy-lift” launch vehicle ... range of 25 to 40 mt, setting a notional lower limit on the size of the super heavy-lift launch vehicle if refueling is available ... this strongly favors a minimum heavy-lift capacity of roughly 50 mt ..."
- "Launch services—milestones". Arianespace. Retrieved 2014-08-19.
- "Welcome to French Guiana". arianespace.com. Arianespace. Retrieved 2014-08-19.
|Wikidata has a property, P375, for space launch vehicle (see uses)|
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