Launched roller coaster
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The launched roller coaster is a modern form of roller coaster which has increased in use in the last decade[clarification needed]. In place of a traditional chain lift, the launched coaster initiates a ride with high amounts of acceleration via one or series of Linear Induction Motors (LIM), Linear Synchronous Motors (LSM), catapults, or other mechanisms employing hydraulic or pneumatic power. These are some of the fastest rides in the world.
Launched coasters mainly feature improved speed, and capability to accommodate more "thrilling" layouts. These coasters, however, can be less reliable than traditional chain-lifted coasters, and are considered to require heavier maintenance.
LIM / LSM 
LIM and LSM coasters use propulsion via electromagnets, which utilize large amounts of electricity to propel the coaster train along its track into the ride elements (e.g. inversions, twists, turns and short drops). Seven design companies managing these types of rides are Vekoma Industries, Intamin, Gerstlauer, Premier Rides, Maurer Söhne, Zierer and MACK Rides.
Electricity is transferred into a motor so that it controls the speed at which it will urge the car forward. LIMs are mainly used in Premier Rides roller coasters and Intamin impulse coasters. However, LIMs are also used for transport systems and the Tomorrowland Transit Authority in the Magic Kingdom for low acceleration, unlike what most roller coasters use for high acceleration.
Fluid pressure 
Hydraulic-launched roller coasters give the riders high acceleration, yet with improved smoothness, over the electromagnetic and catapult launch mechanisms. The Swiss manufacturer Intamin pioneered this new style.
The heart of the system is several (usually eight) powerful hydraulic pumps, each capable of producing around 500 horsepower (373 kW). Hydraulic fluid is pumped into several different hydraulic accumulators (energy storing devices) containing two compartments separated by a piston. As the incompressible hydraulic fluid is pumped into one compartment a gas in the other compartment is compressed.
At launch, the fluid under pressure from the accumulators is used to drive a number (typically 16 or 32) of hydraulic motors, which spin a large winch drum that rewinds a cable attached to a catch-car under the train in a matter of seconds. The catch-car moves in a groove in the center of the launch track with the motor at one end, and the waiting train at the other.
While the train inches forward, the pusher moves back from the motor towards the train. Once the pusher connects, the anti-rollback braking system drops beneath the track, giving the train the green light to be launched. In the Kingda Ka roller coaster, the system as a whole can produce a peak power of up to 20,800 hp (15.5 MW) for each launch.
These launches are considered capable of giving a far greater and smoother acceleration than the LIM/LSM styles. The acceleration from a LIM/LSM launch is greatest at the beginning and dies off rapidly towards the end of the launch, but the acceleration from a hydraulic launch remains nearly constant throughout the launch.
The first hydraulic launch coaster was Xcelerator reaching 82 mph (132 km/h) in 2.3 seconds. The world's current tallest and 2nd fastest coaster Kingda Ka at Six Flags Great Adventure, which opened in the spring of 2005 is capable of reaching 128 mph (206 km/h) in 3.5 seconds.
Hydraulic launched rides usually have a tower after the launch, with differing layouts afterwards depending on the park's financial resources. Top Thrill Dragster brakes after the tower and Kingda Ka features a single 130 ft (40 m) hill after the tower, while Storm Runner at Hersheypark offers a series of overbanked turns and inversions after its 180 foot (55 m) tower drop. Rita at Alton Towers does not have a tower, only airtime hills and banked turns. Stealth at Thorpe Park has a large tower that travels to the left over the top hat, and then slows on an airtime hill with magnetic brakes. Xcelerator at Knotts Berry Farm offers two overbanked turns after the tower. Along with the height and speed, these coasters, named "Rocket Coasters" in the industry, are considered more comfortable because of a smoother launch than LIM-style launches.
A recent newcomer to the hydraulic launch industry is Vekoma, who opened a coaster in 2004 called Booster Bike at Toverland in the Netherlands, said to give riders a sensation of racing on high performance motorcycles over a low twisted layout, at speeds up to 47 mph (75 km/h). The cars imitate real motorcycles, and the riders sit in the same posture as real bikers.
Hydraulic launch technology faces competition from S&S Power, a leading manufacturer in vertical amusement rides, who in recent years created a new breed of coasters with pneumatic launch power. Their coaster model, the Thrust Air 2000, was first built in Kings Dominion in Doswell, Virginia, USA, under the name Hypersonic XLC. The coaster has been clocked to launch from the rest at station to 80 mph (128 km/h) in 1.8 seconds. The coaster proceeds to ascend a tower at 90 degrees and descends vertically. Another compressed air–launched coaster, built in Fuji-Q Highland, is Dodonpa. This coaster is capable of launching passengers from 0 to 106.9 mph (171 km/h) in 1.8 seconds.
Other styles 
In the catapult launch, a large diesel engine or a dropped weight winds a cable to pull the train until it accelerates to its full speed.
These rides are often not very tall, and usually achieve speeds of 60 mph (96 km/h).
Flywheel launches are used on some Anton Schwarzkopf designed shuttle loop coasters and Zamperla Motocoasters. A large flywheel is spun at high speeds and is attached to a cable that propels the train forward.
Electric motor and spring tension 
Arrow Dynamics' Launched Loop coasters, which were popular in the 1970s and 1980s, use a powerful electric motor and tensioned springs to propel a launch car forward. The launch car pushes the train outward to a drop, and then returns to its position. After the train reaches the opposite platform, another catch car works the same way. An example of this is Irn Bru Revolution.
Friction wheels 
Another type is launch is by friction wheels. The launch track consists of a series of horizontal tires that pinch the brake fins on the underside of the train. One example of this is the Incredible Hulk Coaster at Universal's Islands of Adventure
- "How Kingda Ka works photos- Pictures of the hydraulics that power Kingda Ka roller coaster at Six Flags Great Adventure, New Jersey". Themeparks.about.com. 2010-06-19. Retrieved 2011-12-04.
- Counterweight launch system on Schwarzkopf rides
- Flywheel launch system on Schwarzkopf rides
- Intamin official website