What makes an exciting roller coaster?

It is thought that the origins of roller coasters date back to the 17th century, when ice slides were built in Russia. Woodenframed structures up to 20 m tall would be sprayed with water and left to freeze so that thrillseekers could toboggan down them. To this day, there are roller coasters across Europe known as Montagnes Russes, Russian Mountains.

Opinion differs as to whether the French or Russians introduced wheeled carts to the slopes. Catherine the Great is reported to have demanded a design to be erected in 1784 using wheeled carts instead of sledges on ice. Others claim that Belleville and Paris were the first – in 1817 – to introduce cars to rides.

What is accepted is that the first golden age of the roller coaster was during the 1920s, when there were more than 3,000 of them in operation. For a variety of reasons, including war and financial depression, the rides were so out of favour by the late 1970s that they faced extinction, with only 300 surviving.

Now, the number is up to nearly 4,000 and rides are being built at a rapid rate around the world. The use of magnetic and hydraulic propulsion systems has generated even faster rides with greater acceleration. The introduction of new technology such as virtual reality is set to increase the riders’ sensory experiences.

Design considerations

Most roller coaster ‘trains’ are not powered and rely on a chain or launch mechanism to take them to the first, and usually tallest hill. Gravity then carries them around the twists and turns of a track, back to the start again. Potential energy is gained as a train is pulled to the top of a hill, and when the train rushes down a slope this is converted into kinetic energy. Kinetic energy is greatest at the lowest point of the roller coaster, where the train is at its fastest, and determines how high a train will be able to climb to gather potential energy on future inclines. It also ultimately dictates how long the ride will last.

It is this interplay between potential and kinetic energy that keeps a train moving over bumps and through loops, despite loss of energy through friction and wind resistance, so that brakes are needed to bring it to a complete stop at the station. These basic laws of physics are used not only to design a track, but to create a safe but thrilling experience for a rider.

Unpleasant bumpy and jerky tracks were a problem for older roller coasters, and users could end up with bruises on hips, knees, shoulders or ribs. The current design approach, however, means a smooth ride is at the heart of a design. Using computer models, engineers have direct control over the flow of forces and can create a virtual ride that can be analysed before it is built.

Fraser Ross, Concept Engineer for Vekoma Rides Manufacturing, uses this modelling when creating new roller coasters. A new ride developed by Vekoma called Orkanen, at Farup Sommerland in Denmark, is an example using the updated design method. It boasts organic, naturally flowing shapes, limited lateral swinging dampened by shock absorbers, padded ergonomic seats for comfort and a restraint system designed for children as small as 1.1 m tall. The ‘suspended family coaster’ has been well received since it opened in 2013, and five more have been ordered for theme parks worldwide.

Feel the force

Positive G-forces are experienced by passengers when moving upwards at speed, while accelerating, when pulling back up at the bottom of a drop or going through a tight corner. They are negative when decelerating, cresting over the top of a hill and when dropping back down. Concept engineers take into account the vertical, lateral and longitudinal accelerations on the passengers and the train. Human tolerances depend on the magnitude of the G-force, the length of time it is applied and the direction in which it acts. People would experience a higher G-force falling into bed than on a roller coaster; however, the duration of that G-force to the bed is so short it is almost imperceptible.

The limit for positive, or vertical, G-forces for a thrilling but comfortable experience where the blood is forced away from the head so the body feels heavy, is around 6Gs, the same experienced by fighter pilots. Entering into the bottom of a loop, riders would usually experience around 4Gs of vertical force, which effectively means five times their bodyweight is being pushed into their seat. This feeling only lasts for a split second, so is thrilling but not too intense.

For an ‘airtime moment’, when there is a fluttering, breathless feeling in the pit of the stomach, engineers can incorporate a ‘camelback’, or hump-shaped hill that travels in a straight line, with 0Gs (or less) of vertical acceleration, which will make riders lift out of their seats and add a sense of thrill to a ride.

When a train accelerates or decelerates, longitudinal forces act forwards and backwards, pushing passengers back into their seats or forwards into their restraints, making a launch seem even faster, or braking more urgent. Both positive and negative lateral G-force accelerations are experienced as a train races round curves, with the tightness of a curve determining the magnitude of the lateral force being experienced by a passenger.

Thrills not spills

G-force is only one of the ingredients needed to create a thrilling ride. Brendan Walker, Professor of Creative Industries at Middlesex University and Principal Research Fellow in Computer Science at the University of Nottingham, has been dubbed the ‘world’s only Thrill Engineer’ by The Times. He works with theme parks on rides and says that an exciting ride relies on a combination of physical and psychological elements. Rides are designed to excite the senses, and this should begin with the appearance of a roller coaster. It should look impressive, exciting and even a little intimidating to someone waiting to ride it, to set their expectations for a thrilling ride.

Roller coasters should also make people feel as if they can do the impossible, such as fly unaided or survive a high drop. Features such as loops and plunges are incorporated, which act on the vestibular system in the inner ear. This system senses acceleration and a yanking feeling, known as ‘jerk’, to create thrilling sensations.

Professor Walker explains that roller coasters should make riders feel as if they have lost control, which triggers the body and mind’s state of alertness, or arousal. This can be caused by unusual forces such as jerk, or varied jerks known as ‘jounce’. The feeling of being out of control can be triggered by rapid acceleration as well as sudden drops and loops, but variety and the element of surprise are needed to sustain a state of arousal.

Combinations of features might include a negative G-force experience known as a ‘hop’ to produce a lurching feeling in the stomach, followed by a pull out of a drop to create positive G-force, with designers manipulating a rider’s expectations and building suspense. The clothoid loop is a defining feature in many modern roller coaster designs – see Inverted teardrop.

Generating momentum

In order for riders to feel the force of a clothoid loop or corkscrews, the train they are sitting in has to have enough kinetic energy to reach a high enough speed to carry them, upside down, safely through the loop. While the great majority of roller coasters use traditional lift hill chains to pull a train up the initial highest hill, now rides are being built that are capable of launching trains at much higher speeds.

Electromagnetic launch systems, introduced at the end of the 1990s, require no moving parts and so require less maintenance than hydraulic launch systems or traditional lift hill chains. They use electrical impulses to attract or repel ‘fins’ on the underside of roller coaster trains. Vekoma uses two types: linear induction motors (LIM) and linear synchronous motors (LSM).

The main difference between the two is where the magnets are positioned. LIMs use sets of electromagnets mounted on a track, to which alternating current is applied to create a magnetic field. A train is propelled rapidly forward when its metal fin passes through the magnetic field generated.

In contrast, strong magnets are secured to a train on a track in an LSM system and rely on the basic principles of attraction and repulsion (using a DC motor). When a train approaches magnets on the track, it is attracted to them, and when it passes over them the magnetic field is reversed to propel the train away from the magnet, forward down a track. When sets of track magnets are fired rapidly, they can propel a train at great speeds.

Alternatively, hydraulic launch systems, which have similar function principles to a ‘catapult’ mechanism on an aircraft carrier (although powered by steam), are used for the world’s three fastest roller coasters – see Hydraulic motors.

Hydraulic launches have the advantage of consistent power requirements and are used on some of the world’s fastest coasters, including the Formula Rossa at Ferrari World in Abu Dhabi. This ride uses 48 hydraulic motors to fire riders to 240 km/h in five seconds.

New experiences

Professor Walker believes one of the biggest barriers to creating bigger, faster and more imaginative rides is risk aversion. As roller coasters cost in the region of £10million to £20million to build, the parks need to ensure a wide enough demographic of customers to make the investment worthwhile, which can limit innovation.

However, new ride design software is allowing engineers to create more organic roller coaster elements which have not been seen before. Rides using organic shapes are designed to create more fluid, graceful, less artificial rides to give the effect of flying or diving into water. The next generation of roller coasters could look radically different from the geometrically shaped ones with specially shaped loops and vertical drops we know today.

New track shapes will be created such as a cross between a clothoid loop and a corkscrew. This will allow the rider to experience the sensation created by a clothoid loop and corkscrew simultaneously. By mixing the two, a ride will not only look new and exciting, but will provide new stomachchurning sensations for riders too.

Marcus Gaines from the European Coaster Club has seen other innovative trends being implemented. More manufacturers are coming up with lap bar designs that give riders greater freedom of movement. Lap bars used to be popular, and were used on rides with only positive G-forces, such as Scorpion at Busch Gardens, Florida, but now they are being used utilised by some companies on coasters with negative G-forces and inversions other than a standard vertical loop.

The shape of the seat also plays a role in securing the rider in place. The design can make rides seem scarier, particularly if customers are flung upside down, enhancing the adrenalin buzz of a ride.

There is also a move away from steel tracks back to wooden ones, to capture a bygone age of roller coasters, and to save money as they’re typically cheaper to build than big steel coasters. While they are not currently popular in the UK, elsewhere firms are pushing their limits, building faster, steeper wooden roller coasters with loops. In the US, Rocky Mountain Construction unveiled its first wooden roller coaster to go upside down in Silver Dollar City, Missouri, in 2013, and will unveil the world’s first launched wooden roller coaster at Dollywood, in Tennessee, this spring. Last year, Martin & Vleminckx Rides built two wooden coasters in China that featured corkscrew inversions.

A trend that is starting to make its way into theme parks is the incorporation of virtual reality into roller coasters. For the past couple of years, Mack Rides in Germany, in partnership with a local university, has been working on combining VR with roller coasters. In 2015, the public got the chance to try out the world’s first VR Coaster at Europa Park, in Rust, Germany.

Alton Towers has been working with the Guildfordbased firm, Figment Productions Ltd, to revamp its Air roller coaster to create a VR roller coaster experience. From April 2016, the ride will have an outof- this-world theme and is to be called Galactica with riders wearing headsets based on the Samsung Gear VR system.

Figment has developed Vector VR, a patent pending system that includes a custom sensor, fixed next to a rider’s seat, with an inertial measurement unit that constantly monitors the movement at that point on the train and compares it to a ‘master path’ captured by the same sensor.

The visuals that show up on a rider’s headset controlled by the Vector software algorithms sync with the sensor so they match the motion of the roller coaster train and position the rider in the right space in the virtual world. The headset also adds tracking for rotational head movements, completing the picture to match what the rider sees with what their vestibular system tells their brain they should be seeing. This is key to minimising motion sickness and the system means that a 90° sweep can easily be manipulated to become a 360° turn. Galactica riders will also be in a prone position intended to increase the sensation of flying, allowing riders to stretch their hands out and feel the wind in their face.

On the up

Just as roller coasters seem to push and pull their riders in different directions, the future of the rides themselves is diverging. Use of organic-shaped rides and virtual reality technology will lead to more immersive and smoother experiences for riders, while noisy, back-to-basics wooden tracks will play on more primal fears to arouse the senses.

What is certain is that there will be faster, more testing experiences on offer than ever before. There are now nearly more than 4,000 coasters to ride, in what is being hailed as the dawn of the second golden age of roller coasters.

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This article has been adapted from "What makes an exciting roller coaster", which originally appeared in the print edition of Ingenia 66 (March 2016).