The XM1203 NLOS-C

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I noticed that the XM1203 ("FCS NLOS-C") never got publicity with the appropriate emphasis, describing its true nature. Most who wrote about it were distracted by the vehicle mass. Even I commented - if at all - rather disparagingly about it, focusing on the by today's standard short barrel (38 calibres) and its thus hardly satisfactory range.

The XM1203 was - as its equally gold-plated and just as cancelled predecessor project, the XM2001 Crusader - equipped with a special feature: A liquid cooling of the gun.

Liquid cooling is traditionally only applied if the associated high weight is acceptable; this was accepted with Maxim-style heavy machine guns, and is still accepted with some naval gun designs (example). Evaporation cooling with water enables a gun to maintain its maximum rate of fire well beyond what its thermal mass would allow for (air cooling is weak and reduces the sustained rate of fire of howitzers to about 1-3 rpm). A SPG such as PzH 2000 can sustain its highest rate of fire for approximately a minute. The XM1203 was able to do so at least until it ran out of ammunition (24 shells at 10 rpm ~ 138 seconds). Its liquid cooling was relatively light weight:

"Following firing, the breech opens and the Automated Cooling and Cleaning System (ACCS) sprays a water/glycol mixture to extinguish residual propellant embers, clean the laser window, wet the breech seal and cool the propellant chamber."*

quote source: Army AL&T, April-June 2008, p. 45

THIS was the most defining feature, not the by now ordinary networking stuff, by now ordinary maximum rate of fire, the obsolete barrel length or the 'only 50% too heavy for C-130J' weight.

What kind of army would define requirements for such a capability?

Well, I can tell what kind of army would NOT pay much attention to such a capability: An army that expects to face counterfires by long-range artillery. Such an army would expect its own artillery to change positions often, typically after firing a short burst of smoke shells or a MRSI strike** of maybe four HE shells. There is rarely going to be an opportunity to fire multiple MRSI missions on different targets before the "scoot" part of "shoot & scoot".***

Furthermore, an army that expects very high expenditures of munition per day - typical planning would be 200/day and barrel, Ukraine fighting reached peaks of 450/day and barrel!) would likely insist on a larger onboard munition supply, such as 60 shells.

What kind of army is left? I suppose an army that expects to beat up small 3rd rate or worse armies that pose little artillery counterfires threat, possibly after a quick deployment by (heavy) airlift. And one can read this off the design!

S O

defence_and_freedom@gmx.de

*: They used a laser to ignite the propellant, not some percussion cap. 
**: Multiple shells arriving within few seconds because they were fired at different elevation angles with different quantity of propellant modules. This is relevant for lethal shells (not smoke) and meant to exploit the surprise effect. All shells arrive before the targeted troops can leave the area or find cover. This is more lethal per shell (more efficient) than long bombardments with regular intervals between explosions. 
***: The SPG (or classically the entire battery) fires a few shells, then leaves the area in haste before counterfires arrive. The firing of shells can be measured by hostile radars and hostile fire control can calculate the point of origin. That's why artillery locations are very dangerous after firing commenced from there.

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