The use of LSMs in roller coasters is used to launch and accelerate roller coaster car along a straight section of track.  A basic LSM roller coaster works with a set of permanent magnets is implemented in the roller coaster track, with the north and south electromagnets alternating.  There is also a set of electromagnets (a north and a south) called armatures placed inside the car of the roller coaster at specific intervals.  These armatures would then be placed strategically so that the left magnet on the track would repel the armature magnets in the car and attracted to the magnet to the right, causing the car to move forward.  The same set-up is symmetrical on the other side of the roller coaster car as well.  

For LSM roller coasters, the north electromagnet in the armature would be placed intentionally in between a north magnet on the right and a south magnet on the left on the roller coaster track.  Thus, the two north magnets would repel each other, while the armature north magnet would be pulled toward the south magnet to the front.  This would cause an overall forward motion.  When the armature magnets attract toward the permanent magnets on the track, polarization of the armature magnets is needed to allow the roller coaster car to continually move forward.  Here, a "synchronized" pulse turns electromagnets on and off in sequence to accelerate the roller coaster car to its full speed.  It is this force between the armature magnets and the permanent magnets on the coaster track that allows the roller coaster to travel.  

What are some advantages and disadvantages from using a LSM roller coaster?

Like the LIM, the advantages of the LSM is that it can accelerate roller coasters up a hill from 0 to 100 mph, in as little as 7 seconds. Also, because the LSM have few parts and no physical contact, it requires low maintenance and is a very reliable launch system.  

However, because the armature magnets and the permanent magnets on the track must be synchronized at precise intervals, a minor error in timing could cause a failure to launch, and could actually slow the car down instead of speeding it up.  Although  this may not seem like a much of a problem, LSM roller coasters use the same physics to brake the cars.  Instead of using conventional  brakes, a LSM roller coaster uses magnetic impulses in the reverse direction; therefore, if the impulses were to become out of sync, an acceleration could occur in the reverse direction causing a huge accident in the loading dock.  Also the sheer weight of the armature magnets will cause for more energy to be used to move the roller coaster car. 

What are some rides that utilize LSMs?

Superman:  The Escape at Six Flags Magic Mountain , built by Intamin, a Swiss coaster and ride manufacturer, became the first roller coaster in the world to utilize an LSM in 1997, and can accelerate its riders to 100 mile per hour while shooting them up a 415 ft high vertical incline. 

Other rides include the Rock 'N' Roller Coaster at Walt Disney World in Orlando, Florida, and Volcano: The Blast Coaster at Paramount's Kings Dominion in Virginia.

Basic Diagram of How a LSM Roller Coaster Works

Superman:  The Escape at Six Flags Magic Mountain

Volcano: The Blast Coaster at Paramount's Kings Dominion