Superconductors: An essential road to fly
Superconductors are fascinating materials that losses their electrical resistance completely at a very low temperature close to absolute zero or 0 Kelvin. For instance, under normal circumstances, materials may lose energy due to their electrical conduction, and hence our mobile phones, laptops, and other electronic devices heat up when they are charged. Whereas, superconducting materials do not lose energy and conduct perfectly with no resistance. Subsequently, superconducting materials have allowed for important technological advances in computing, generators, particle accelerators, power transmission, MRI scanners and the magnetic fields produced by superconductors help us produce detailed images of the inside of the body.
K. Onnes, a Dutch physicist from the University of Leiden in the year 1911, discovered the nature of superconductivity in mercury. During his research on mercury, the resistance of mercury suddenly vanished when he cooled it to a temperature below 4.2 Kelvin (-269°C). The liquid helium is also at the same temperature and these historical perspectives on mercury are the reason behind the invention of superconductors.
The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition from normal to the superconducting state when it is cooled below the critical temperature. This expulsion will repel a nearby magnet and hence a superconductor behaves like a perfect diamagnet, but there is more than this involved in the Meissner effect. One of the most important and well-known demonstrations of the Meissner effect is its ability to make a magnet levitate above a superconductor hence this blog titled “Superconductors: An essential road to fly”.
High-temperature superconductors (HTS) are used in many AC applications such as transformers and fault current limiters etc. and DC applications like NMR, Maglev train, high field coil, and MRI. For above said applications HTS magnets are created from REBCO conductors and Bi2223 or Bi2212 (BSCCO) conductors. HTS are defined as materials with a critical temperature (the temperature below which the material behaves as a superconductor) above 77 K (−196.2 °C), the boiling point of liquid nitrogen.
Maglev is derived from magnetic levitation. Maglev is used in train transportation that uses two sets of electromagnets. The first one is used to repel and push the train up off the train track and the second one is used to move the elevated train ahead. When we use the train on a track, there is a lot of friction whereas while using a maglev, we take advantage of the lack of friction. Such trains rise approximately 10 cm off the track. There are two types of maglev that are possible: 1. High-speed, intercity maglev systems: The speed limit is 400 km/hr, and 2. Low-speed, urban maglev systems: the speed limit is 80–200 km/hr. The Shanghai maglev train is the only maglev train in commercial operation that can be considered high-speed. Japan operates two independently developed maglev trains. One is HSST by Japan Airlines and the other, which is better known, is SCMaglev by the Central Japan Railway Company.
Superconducting Maglev trains work on the principle of magnetic repulsion between the cars and the track. The word maglev is the combination of two words ‘magnetic’ and ‘levitation’. The magnetic levitation is achieved by an electrodynamic suspension system (EDS). The rails (guideway) contain two sets of cross-connected metal coils wound into a “figure eight” pattern to form electromagnets and the train itself has superconducting electromagnets, which are known as bogies. The train rests on rubber wheels when the train stops.
To begin the motion of the magnetic levitation train, the train moves forward slowly on these wheels allowing the magnets beneath the train to interact with those of the guideway. Once the train reaches 150 km/hr, the magnetic force is strong enough to lift the train 100 mm off the ground and eliminate friction to allow for increasingly high speeds. The same magnetic forces have been used to lift the train to move it forward and keep it centered within the guideway. This is the same technology used by Tesla’s Hyperloop, which makes the ride smooth and the train exceptionally safe.
Undoubtedly, the research on superconductors is instrumental for the advancements of science and technology as an essential road to fly and beyond.