Editing Artillery (section)

===Multiple round simultaneous impact===
[[File:MRSI-trajectories.svg|thumb|Illustration of different trajectories used in MRSI: For any muzzle velocity there is a steeper (> 45°, solid line) and a lower (<45°, dashed line) trajectory. On these different trajectories, the shells have different flight times.]]
{{MRSI_animation_SMIL.svg}}
Multiple round simultaneous impact (MRSI) is a modern version of the earlier [[time on target]] concept. MRSI is when a single gun fires multiple shells so all arrive at the same target simultaneously. This is possible because there is more than one trajectory for a round to fly to any given target. Typically one is below 45 degrees from horizontal and the other is above it, and by using different sized propellant charges with each shell, it is possible to utilize more than two trajectories. Because the higher trajectories cause the shells to arc higher into the air, they take longer to reach the target. If shells are fired on higher trajectories for initial volleys (starting with the shell with the most propellant and working down) and later volleys are fired on the lower trajectories, with the correct timing the shells will all arrive at the same target simultaneously. This is useful because many more shells can land on the target with no warning. With traditional methods of firing, the target area may have time (however long it takes to reload and re-fire the guns) to take cover between volleys. However, guns capable of burst fire can deliver multiple rounds in a few seconds if they use the same firing data for each, and if guns in more than one location are firing on one target they can use Time on Target procedures so that all their shells arrive at the same time and target.

MRSI has a few prerequisites. The first is guns with a high rate of fire. The second is the ability to use different sized propellant charges. Third is a fire control computer that has the ability to compute MRSI volleys and the  capability to produce firing data, sent to each gun, and then presented to the gun commander in the correct order.<ref>{{cite journal |last1=Hu |first1=Xin Jun |last2=Wang |first2=Hang Yu |title= Effectiveness Calculation of Multiple Rounds Simultaneous Impact Shooting Method Based on Monte Carlo Method |journal=Applied Mechanics and Materials |date=September 2013 |volume=397–400 |pages= 2459–63 |doi=10.4028/www.scientific.net/AMM.397-400.2459|s2cid=111026161 }}</ref><ref>{{cite web |title= Multiple Rounds Simultaneous Impact, adjustable simulation |url=https://www.geogebra.org/m/r82YhC8d |website= GeoGebra | date= 30 May 2017}}</ref>  The number of rounds that can be delivered in MRSI depends primarily on the range to the target and the rate of fire. To allow the most shells to reach the target, the target has to be in range of the lowest propellant charge.

Examples of guns with a rate of fire that makes them suitable for MRSI includes UK's [[AS-90]], South Africa's [[Denel G6]]-52 (which can land six rounds simultaneously at targets at least {{convert |25|km|0|abbr= on}} away), Germany's [[Panzerhaubitze 2000]]<ref>{{cite web |title=Hungary purchases a brutal military beast that can eliminate targets from over 60 kilometres |url= https://dailynewshungary.com/hungary-purchases-a-brutal-military-beast-that-can-eliminate-targets-from-over-60-kilometres/ |website= Daily News Hungary |date= 9 January 2019}}</ref> (which can land five rounds simultaneously at targets at least {{convert|17|km|0|abbr=on}} away), Slovakia's [[155mm SpGH ZUZANA|155 mm SpGH ZUZANA 2]],<ref>{{Cite web |title=Kotadef article on 155mm SpGH Zuzana |url=https://kotadef.sk/projekty/zuzana/?lang=en |access-date=2025-01-02}}</ref> and [[K9 Thunder]].<ref>{{Cite web |title= Finnish Army report on K9 Thunder |url=https://maavoimat.fi/en/self-propelled-howitzer-k9-thunder |access-date=2025-01-02}}</ref>

The [[Archer Artillery System|Archer project]] (developed by BAE-Systems Bofors in Sweden) is a 155&nbsp;mm howitzer on a wheeled chassis which is claimed to be able to deliver up to six shells on target simultaneously from the same gun. The 120&nbsp;mm twin barrel [[AMOS]] mortar system, joint developed by [[BAE Systems Hägglunds|Hägglunds]] (Sweden) and [[Patria (company)|Patria]] (Finland),<ref>{{Cite web | place = [[Finland|FI]] | url= http://www.patriahagglunds.fi/ |title= Patria hagglunds |access-date=April 4, 2010 |archive-url= https://web.archive.org/web/20100404172145/http://www.patriahagglunds.fi/ |archive-date=April 4, 2010 |url-status= dead |df=mdy-all}}</ref> is capable of 7 + 7 shells MRSI. The United States [[XM2001 Crusader|Crusader]] program (now cancelled) was slated to have MRSI capability. It is unclear how many fire control computers have the necessary capabilities.

Two-round MRSI firings were a popular artillery demonstration in the 1960s, where well trained detachments could show off their skills for spectators.