Editing Electrothermal-chemical technology (section)

== Background ==
[[Image:XM360.png|right|thumb|The XM360.]]

The constant battle between [[vehicle armour|armour]] and armor-piercing round has led to continuous development of the main battle tank design. The evolution of American anti-tank weapons can be traced back to requirements to combat [[Soviet Union|Soviet]] tanks.  In the late 1980s, it was thought that the protection level of the Future Soviet Tank (FST) could exceed 700&nbsp;mm of rolled homogeneous armour equivalence at its maximum thickness, which was effectively immune against the contemporary [[M829]] [[kinetic energy penetrator|armour piercing fin stabilized discarding sabot]].<ref>Ropelewski, ''Soviet Gains in Armor/Antiarmor Shape US Army Master Plan'', p.69</ref>  In the 1980s the most immediate method available to NATO to counter Soviet advances in armour technology was the adoption of a 140&nbsp;mm main gun, but this required a redesigned turret that could incorporate the larger breech and ammunition, and it also required some sort of automatic loader.<ref>Schemmer, ''Army, SecDef's Office at Loggerheads over Antiarmor'', p.53</ref> Although the 140&nbsp;mm gun was considered a real interim solution, it was decided after the fall of the Soviet Union that the increase in muzzle energy it provided was not worth the increase in weight. Resources were therefore spent on research into other programs that could provide the needed muzzle energy. One of the most successful alternative technologies remains electrothermal-chemical ignition.

Most proposed advances in gun technology are based on the assumption that the solid propellant as a stand-alone propulsion system is no longer capable of delivering the required muzzle energy.  This requirement has been underscored by the appearance of the Russian [[T-90]] main battle tank.  The elongation of current gun tubes, such as the new German 120&nbsp;mm L/55,<ref>The length of the cannon can be found by multiplying the diameter of the barrel and the caliber length.  For example, the M256, which is a 120 mm L/44, has a total length of 5.28 m, while the 120 mm L/55 has a total length of 6.6 m.</ref> which was introduced by Rheinmetall is considered only an interim solution as it does not offer the required increase in muzzle velocity.<ref>Sharoni, ''The Future Combat System'', p. 29</ref>  Even advanced kinetic energy ammunition such as the United States' [[M829A3]] is considered only an interim solution against future threats.<ref>Pengelley, ''The new era in tank main armament'', p.1522</ref> To that extent the solid propellant is considered to have reached the end of its usefulness, although it will remain the principal propulsion method for at least the next decade{{clarify|date=July 2015}} until newer technologies mature.<ref>Sharoni, ''The Future Combat System'', p.30</ref> 

ETC technology offers a medium-risk upgrade and is developed to the point that further improvements are so minor that it can be considered mature.{{citation needed|date=July 2015}}  The lightweight American 120&nbsp;mm [[XM291]] came close to achieving 17 MJ of muzzle energy, which is the lower-end muzzle energy spectrum for a 140&nbsp;mm gun.<ref>Diamond, ''Electro Thermal Chemical Gun Technology Study'', p.5</ref>  However, the success of the XM291 does not imply the success of ETC technology as there are key parts of the propulsion system that are not yet understood or fully developed, such as the plasma ignition process.  Nevertheless, there is substantial existing evidence that ETC technology is viable and worth the money to continue development.  Furthermore, it can be integrated into current gun systems.<ref>Sauerwein, ''Rheinmetall's NPzK''</ref>