Editing Linear motor (section)

=== High acceleration ===
High-acceleration linear motors have been suggested for a number of uses.
They have been considered for use as [[weapon]]s, since current [[armour-piercing]] ammunition tends to consist of small rounds with very high [[kinetic energy]], for which just such motors are suitable. Many amusement park [[launched roller coaster]]s now use linear induction motors to propel the train at a high speed, as an alternative to using a [[lift hill]].

The United States Navy is also using linear induction motors in the [[Electromagnetic Aircraft Launch System]] that will replace traditional [[steam catapult]]s on future aircraft carriers. They have also been suggested for use in [[spacecraft propulsion]]. In this context they are usually called [[mass driver]]s. The simplest way to use mass drivers for spacecraft propulsion would be to build a large mass driver that can accelerate cargo up to [[escape velocity]], though [[reusable launch system|RLV]] launch assist like [[StarTram]] to [[low Earth orbit]] has also been investigated.

High-acceleration linear motors are difficult to design for a number of reasons. They require large amounts of [[energy]] in very short periods of time. One rocket launcher design<ref name="coilgun">{{cite web|url=http://www.coilgun.info/theory/electroguns.htm|title=Magnetic Materials - Electromagnetic Guns|publisher=coilgun.info|access-date=2014-11-22|archive-date=2008-05-16|archive-url=https://web.archive.org/web/20080516063621/http://www.coilgun.info/theory/electroguns.htm|url-status=dead}}</ref> calls for 300 GJ for each launch in the space of less than a second. Normal [[electrical generator]]s are not designed for this kind of load, but short-term electrical energy storage methods can be used. [[Capacitors]] are bulky and expensive but can supply large amounts of energy quickly. [[Homopolar generator]]s can be used to convert the kinetic energy of a [[flywheel]] into electric energy very rapidly. High-acceleration linear motors also require very strong magnetic fields; in fact, the magnetic fields are often too strong to permit the use of [[superconductivity|superconductors]]. However, with careful design, this need not be a major problem.<ref>{{Cite journal|journal = Superconductor Science and Technology|year = 2010|title = A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system|first1 = F. |last1 = Yen|first2 = J. |last2 = Li|first3 = S. J.|last3 = Zheng|first4 = L.|last4 = Liu|first5 = G. T.|last5 = Ma|first6 = J. S.|last6 = Wang|first7 = S. Y.|last7 = Wang|volume = 23| issue=10 |pages = 105015|doi = 10.1088/0953-2048/23/10/105015|arxiv = 1010.4775|bibcode = 2010SuScT..23j5015Y| s2cid=119243251 }}</ref>

Two different basic designs have been invented for high-acceleration linear motors: [[railgun]]s and [[coilgun]]s.