Editing Electrothermal-chemical technology (section)

== Operational principle ==
[[Image:ETC.png|right|thumb|upright=1.35|A diagram of a working electrothermal-chemical gun.]]

An electrothermal-chemical gun uses a plasma cartridge to ignite and control the ammunition's propellant, using electrical energy as a catalyst to begin the process.  Originally researched by Dr. Jon Parmentola for the U.S. Army, it has grown into a very plausible successor to a standard solid propellant tank gun.  Since the beginning of research the United States has funded the XM291 gun project with US$4,000,000, basic research with US$300,000, and applied research with US$600,000.{{Citation needed|date=August 2008}}  Since then it has been proven to work, although efficiency to the level required has not yet been accomplished.  ETC increases the performance of conventional solid propellants, reduces the effect of temperature on propellant expansion and allows for more advanced, higher density propellants to be used.  It will also reduce pressure placed on the barrel in comparison to alternative technologies that offer the same muzzle energy given the fact that it helps spread the propellant's gas much more smoothly during ignition.<ref>Hilmes, ''Aspects of future MBT conception''</ref>  Currently, there are two principal methods of plasma initiation: the flashboard large area emitter (FLARE) and the triple coaxial plasma igniter (TCPI).

=== Flashboard large area emitter ===
Flashboards run in several parallel strings to provide a large area of plasma or ultraviolet radiation and uses the breakdown and vaporization of gaps of diamonds to produce the required plasma.  These parallel strings are mounted in tubes and oriented to have their gaps azimuthal to the tube's axis. It discharges by using high pressure air to move air out of the way.<ref>Diamond, ''Electro Thermal Chemical Gun Technology Study'', pp.11-12</ref>  FLARE initiators can ignite propellants through the release of plasma, or even through the use of ultraviolet heat radiation.<ref>Diamond, ''Electro Thermal Chemical Gun Technology Study'', pp.13-15</ref>   The absorption length of a solid propellant is sufficient to be ignited by radiation from a plasma source.  However, FLARE has most likely not reached optimal design requirements and further understanding of FLARE and how it works is completely necessary to ensure the evolution of the technology.  If FLARE provided the XM291 gun project with the sufficient radiative heat to ignite the propellant to achieve a muzzle energy of 17 MJ one could only imagine the possibilities with a fully developed FLARE plasma igniter.  Current areas of study include how plasma will affect the propellant through radiation, the deliverance of mechanical energy and heat directly and by driving gas flow.  Despite these daunting tasks FLARE has been seen as the most plausible igniter for future application on ETC guns.<ref>For further technical information on FLARE ''see:'' P. Diamond</ref>

=== Triple coaxial plasma igniter ===
A coaxial igniter consists of a fully insulated conductor, covered by four strips of aluminium foil.  All of this is further insulated in a tube about 1.6&nbsp;cm in diameter that is perforated with small holes.  The idea is to use an electrical flow through the conductor and then exploding the flow into vapour and then breaking it down into plasma.  Consequently, the plasma escapes through the constant perforations throughout the insulating tube and initiates the surrounding propellant.  A TCPI igniter is fitted in individual propellant cases for each round of ammunition.  However, TCPI is no longer considered a viable method of propellant ignition because it may damage the fins and does not deliver energy as efficiently as a FLARE igniter.<ref>TCPI is also covered in ''Electro Thermal Chemical Gun Technology Study'' by P. Diamond</ref>