Saturation fire. Also the newer rockets for MLRS are amazing. And these weapons arent very large compared to many ship fired missiles. There is a certain amount of time it simply takes to get a air asset airborne then on to the target. In the time it may take a F-18 or VTOL to the target area a barrage of MLRS could already have arrived and given fire on the spot for a while.
And no reason to have these on a landing ship or pretty much any other missile besides Defensive weapons in my opinion. This would be ment for smaller vessels like destroyers cruisers and frigates maybe it could even fit on a LCS. I figure you could build a reloadsystem that could sustain a hell of alot of fire with a good magazine of missiles.
I honestly do no think such a system would be particularly valuable aboard a naval vessel, at least not at the cost (in fiscal, space and displacement terms) of other types of systems.
At present the US Army is in the process of transitioning over to the M31A1 rocket for the GMRLS, which would provide a max range of ~70 km and deliver a single 200 lb HE warhead. Such a system does allow a very high volume of 'saturation' fire to be delivered very rapidly, and with the addition guidance components, allows both greater range and accuracy in artillery fires delivery. However, such a system is really only useful for either saturation fire or area of effect attacks with HE warheads, and if saturation fire missions are conducted, that level of fire is not able to be maintained without having a very large number of launchers available.
Aboard a ship, the 5" naval cannon is what is would typically be used for fire support missions, This would typically allow a sustained ROF of ~10 rounds per minute (if using a Mk-45 5" gun) out to ~24 km, with each shell weighing ~60 lbs IIRC. However, the naval gun is a multi-purpose weapon, being able to provide naval fire support as well as having anti-air and anti-ship engagement capabilities. With inclusion of the Italian Vulcano ER and LR 5"/127mm cannon ammunition, it would provide a 5" naval cannon with unguided 70km range, or a GPS/INS-guided 100km range. Plus with inclusion of other types of 5"/127mm ammunition for anti-air, a cannon can provide much greater flexibility.
Granted, if the most important characteristic was the immediate delivery of a high volume of fire, a MRLS would be best, since ~6 5" cannon rounds would be needed to equal the amount of delivered explosives from a single M31A1 MRLS rocket warhead. Additionally, systems like the M270A1 GMRLS can load, launch and fire a 12 salvo barrange within 5 minutes, which means 2,400 lbs of HE every five minutes. This of course assumes that there are ample stocks of the M31A1 rockets available, with each weighing 650+ lbs. A 5" cannon would likely only be able to deliver 1,500 lbs of HE every 5 minutes, however most USN destroyers armed with a Mk-45 cannon could potentially maintain a bombardment of up to an hour, or ~18,000 lbs of HE delivered over that timeframe. A GMRLS system consisting of 12 rocket tubes in the launcher would take ~ 40 minutes to deliver an equivalent amount of explosive, but that would require there being 90 rockets aboard to be fired, which would require a significant amount of space aboard ship for a magazine.
In short, such a system could potentially be developed or adapted for use aboard ship, but would only provide a short to mid-ranged shore/land bombardment capability. Given the limitations of space aboard naval vessels, the system would also likely be in place of the more versatile naval cannon, which IMO would make it a rather poor trade off, since there are questions in terms of which system would have a lower total displacement (launcher and munitions) for a small decrease in the amount of time required to deliver
nn weight of explosive on target.
Please note, for the numbers used in estimates and times, certain figures and assumptions provided by the WAG Institute were used. In particular, for ease of calculation purposes, it was assumed that the ready magazine for both the Mk-45 gun as well as the hypothetical M270 launcher were able to be immediately reloaded without delay from the standing magazine where the 'non-ready' 5" ammunition or M31A1 rockets would be stored. Also, the OTO Melara 5"/127mm naval cannons have a sustained ROF of ~20 rounds per minute, vs. the ~10 rounds per minute of the BAE Systems Mk-45, which would mean that the OTO Melara naval gun would take only ~30 minutes to deliver 18,000 lbs of HE on target using all the same assumptions used for the Mk-45 gun and M-270 MRLS.
-Cheers
