An Accelerator Coaster is a hydraulically launched roller coaster model from Intamin. The model usually consists of a long, straight launch track, a top hat tower element, and magnetic brakes that smoothly stop the train without making contact. The technology was developed by Intamin engineers as an alternative to electromagnetic launch systems, such as the Linear Induction Motor (LIM) and Linear Synchronous Motor (LSM), that are found on earlier launched roller coasters like the Flight of Fear and The Joker's Jinx. Unlike the earlier linear induction motors, the Accelerator Coaster's launch system exhibits constant acceleration and is capable of reaching greater speeds.
Accelerator Coasters with the top hat element are known to perform an occasional rollback – when the train is unable to complete the top hat element and rolls back to the starting point – which can occur due to a number of different factors. Despite this, Accelerator Coasters have a great track record for safety and are extremely power efficient, especially compared to older technologies such as the classic chain lift found on most roller coasters. Formula Rossa, the world's fastest coaster, and Kingda Ka, the world's tallest, are some of the most well-known installations around the world.
Despite these world-record setting achievements, Accelerator roller coasters have been infamous for their long terms of mechanical issues with its launch. Examples of these being Xcelerator at Knott's Berry Farm or Top Thrill Dragster at Cedar Point and as of 2022, Accelerator Coasters are no longer being produced.
Technology
An Accelerator Coaster's launch system operates on the same basic principle as a Super Soaker, but on a much larger scale. The coaster's power source is several hydraulic pumps, each capable of producing . These pumps push hydraulic fluid into several accumulators. These accumulators are divided into two compartments by a movable piston, one side filled with hydraulic fluid and the other with nitrogen gas. The nitrogen is held in large tanks directly beneath the actual accumulator. As the hydraulic fluid fills the accumulators, it pushes on the pistons, compressing the nitrogen. It takes approximately 45 seconds to pressurize the accumulators with all pumps operating. All of this pressure is released during each launch, which typically lasts between 2 and 4 seconds.
The heart of the launch system is a large winch, around which the launch cables are wound. This winch is driven by hydraulic turbines. The two launch cables are attached to the winch on its ends, and run through two grooves on top of the launch track. The cables are attached to the sides of the catch-car, which runs in a trough between the grooves. A third, single retractor cable is attached to the rear of the catch-car, it runs around a pulley wheel at the rear end of the launch track and returns to the hydraulic building along the bottom of the launch track, where it is wound in the opposing direction on the winch's drum.
The train connects to the catch-car with a solid piece of metal known as a "launch dog" that drops down from the center car. The launch dog is normally retracted and is held in place by a small magnet, but the launch area has electrical contacts that demagnetize the magnet and cause the launch dog to drop down. The launch dog drops down at an angle, similar to the chain dog that a lifted coaster uses to connect to the lift chain.