For the past 20 years, however, NGFS has been the realm of the 5-inch Mk 45 gun found in pairs on Spruance -class destroyers and Ticonderoga -class cruisers (the former are now all decommissioned) and singly on Arleigh Burke -class destroyers. Generally speaking, this gun is too small and too short ranged, with too few of them to adequately support Marines ashore. Notably, 5-inch Mk 45 guns were found only on the Navy’s very high-end multipurpose warships, likely making them too valuable to regularly put into risky situations close to the shore. More capability was obviously needed for adequate support.
That need is beginning to be addressed with the deployment of the 6-inch/155-mm Advanced Gun System (AGS) on the Zumwalt -class destroyers. The AGS will return to the Fleet a 6-inch, 220-pound round not seen in decades. In its basic ballistic form, the round will have a range of about 24 nautical miles (nm), similar to that of the vaunted Iowa -class battleships. It will also be able to launch a rocket-assisted shell, the long-range land attack projective, a record 63 nm or more. This adds a significant capability for supporting Marines and influencing events ashore. (However, significantly fewer of these rounds will be available—perhaps only 10 percent of the magazine load. 1 ) Table 1, below, attempts to quantify the Navy’s naval fires capability since World War II leading up to the AGS, including a comparison to a Marine artillery battery of six M777 6-inch howitzers. 2
If the AGS works well on the Zumwalt class, the Navy should consider adding it to future Flight III Burke -class destroyers. (However, the size and mount weight will certainly be issues for naval architects to consider, and it may prove unsuitable.) The Navy would also be wise to consider adding an AGS mount or two to the forthcoming LR(X), the follow-on to the Whidbey Island/Harpers Ferry -class landing dock ships (LSDs), which would then provide amphibious readiness groups (ARGs) with some very useful organic firepower. This would support an embarked Marine Expeditionary Unit with nearly the equivalent of another Marine M777 battery of artillery that would be available early in the operation and have great mobility.
The Electromagnetic Railgun
The AGS will add a much needed, but interim capability to the Fleet. The real promise going forward, as the Zumwalt class is both experimental and limited to only three ships, is the electromagnetic railgun (EMRG). Instead of using traditional chemical propulsion, the EMRG relies on massive amounts of electrical force. When doubled from current testing, some 64 mega-joules (MJ) of energy will be available to propel a 40-pound kinetic energy (KE) round at Mach 7 out to 200 or more nautical miles.
Due to its speed, the EMRG will rely on solid shot—a round without any explosives. This increases not only safety for the ship, as there won’t be any magazine explosions, but the amount of storage space. The round is much smaller, and with no companion propellant charge, perhaps four times the number of rounds currently found in a Burke -class DDG 5-inch/Mk 45 magazine could be stored, in the neighborhood of 2,400 rounds per mount. The rate of fire is targeted at 6 to 12 rounds per minute, or 360 to 720 rounds per hour.
According to MJ energy calculations to date, the EMRG KE round will be at least two to eight times as powerful as today’s specialized (to include the long-range land attack projectile) and conventional artillery rounds. Translating the effect into 1,000-pound warhead equivalents (such as the Mk 83 bomb and Tomahawk missile warhead) is also illustrative. Based again on an MJ energy comparison (the “MJ” case, for example, is estimated at 16.9 MJs per railgun KE round versus around 1,012 MJs per Mk 83), one gets a low-end of 60 rounds per 1,000-pound warhead equivalent.
Another calculation quotes a KE round as being “three to five times more effective than today’s naval round” and takes the lower figure (“3X” case) versus the explosive charge of a conventional 5-inch round. This leads to a figure of 19 railgun KE rounds equaling a 1,000-pound warhead, which results in each railgun shooting somewhere between 10 to 31 1,000-pound equivalents per hour (based on 10 rounds per minute/600 per hour.) 3 Assuming that four guns fire for four hours, this equates to between 160 and some 496 total Tomahawk warhead equivalents—all reaching their targets at maximum range in a mere six minutes of flight time. Other preliminary railgun calculations hint at even more lethal performance. (And future generations of this technology have the potential for even greater muzzle velocity—say 300 vice 64 MJ; a range of 250 nm, 300 nm, and more; and impact force.) Table 2 describes key railgun performance in comparison to the AGS. Again, a reference battery of Marine M777 6-inch artillery is used.
Assuming an initial operational capability date of 2025, the new EMRG mount could be placed in the DDG-51 Flight IV—the first unit, scheduled for construction starting in 2030—with testing on one or more DDG-51 Flight IIIs and Zumwalts prior. This may prove challenging, given the relatively limited space in the DDG-51 design for added growth and the need for additional electrical power generation and associated electrical storage/capacitor/mount support equipment (which for the first generation or two may be significant). But with the Zumwalts , some number of DDG-51 Flight IIIs and the early (of eventually 33 planned) Flight IVs, perhaps about 20 AGS or EMRG guns will eventually be in service in the late 2030s—enough to provide one or two per deployed expeditionary strike group (ESG).
Arming the Amphibious Ready Group
To add even more firepower, the Navy should also consider adding EMRGs to future amphibious ships. This way, an ARG can carry its own organic NGFS capability. During World War II, every amphibious ship—and every merchant marine ship, for that matter—carried guns for self defense. Large attack transports carried one or more 3- to 5-inch gun, with the single 5-inch/Mk 38 being standard by 1943. Eight-thousand ton LSDs similarly le d with the 5-inch/Mk 38. With an enclosed mount weight of about 21 tons and a destroyer magazine capacity of some 575 rounds, 5-inch/Mk 38 guns were commonplace on small 2,500-ton destroyers (ships of the Fletcher class had five each) and even smaller 1,700-ton destroyer escorts (ships of the Rudderow and Butler classes had two). Further merchant marine “Liberty” ships typically carried a 4-inch gun aft and a 3-inch gun forward, plus many smaller ones. To operate the guns, a naval armed guard detachment of about 36 men was part of a ship’s company. Leveraging this historical precedent of arming amphibious ships— even those in the near future, which may be built more to commercial rather than military standards—could pay big dividends for the Navy.
To add to the total number of guns and provide organic ARG capability, one or two EMRG mounts could be installed in the forthcoming LR(X)-class ships, as well as all other future amphibious ships. 4 This LSD replacement is due to start construction in 2019 and continue through 2033. Earlier models could be built with an AGS mount, or space/weight could be programmed in for an upgrade when the EMRG mounts are available (perhaps in 2025 with the fifth or sixth unit). Beyond the purpose of self-defense, as in the past, these guns will add a powerful offensive capability to the ARG.
If the Navy fully mans the LR(X), a ship’s company would provide the personnel necessary to operate the mounts. If the LR(X) is perhaps a military-civilian hybrid, a return of something like the naval armed guard would be in order for the ship’s gunnery division in addition to other necessary detachments for communications and other concerns (as is already common). The ARG then of the late 2030s could include between two and four organic EMRG mounts, plus one or two more attached as part of a larger ESG. Four EMRG guns would provide a 200 nm range at a combined 24 to 48 rounds-per-minute with a total magazine capacity of nearly 10,000 rounds. Under full-up conditions, meaning no equipment casualties, and chock-full magazines, four railguns could deliver ordnance to a thousand targets in four hours with the warhead equivalence of between 160 and nearly 500 Tomahawks. A ship could be 100 miles out to sea and hit targets 50 miles inland across a range of some 130 miles in either direction and along the coastline 170 miles in either direction. This is greater than the entire 296-mile long coastline of Oregon. Three ships could cover the 840-mile long California coast or half of the East Coast.
NGFS at eight times the range of any past system with two to eight times the weapons effect of any current gun is the EMRG promise. For the first time since at least Vietnam and probably the Korean War, the Navy would have the ability to solidly support Marines ashore with naval fires. This never-before-seen capability would compliment the “…From the Sea” vision and the emerging Marine 21st-century amphibious assault/maneuver warfare “2.0” capability.
Implications for Power Projection
Beyond naval gunfire support, the EMRG has similarly great potential in regards to the broader issue of general power projection. According to Commander Phillip Pournelle’s May 2013 Proceedings article “The Rise of the Missile Carriers,” one strike-mile equals a thousand pound warhead delivered one nautical mile. Thus, one can see the potential impact a mere four railguns will have in comparison to a carrier launching multiple raids of four dozen aircraft, a strike group’s worth of, say, five Tomahawk-armed Burke -class DDGs, and a Captain Wayne Hughes-inspired cheaper, dedicated “land attack”/“heavy” frigate squadron heavily laden with offensive missiles. 5
As Figure 1 shows, the railgun will add a tremendous capability to the carrier strike group (CSG), the ARG/ESG, and potentially all U.S. Navy task forces. In the best case, it will compare favorably inside its range with the CSG itself or multiple ships launching hundreds of missiles. (Even the more conservative “MJ” case is the equivalent to a 12-plane squadron of carrier aircraft, while the higher end is close to 80 percent of the carrier air wing. Another option is adding the “5 DDG” and “EMRG 3X Case” together, so a CSG’s five DDG escorts carry missiles and a railgun.)
Operators and tacticians may consider the return of the gun line as a true power projection tool. Adding EMRGs organically to an ARG with more attached as part of an ESG would provide a world-class NGFS and impressive power projection capability, increasing their ability to act independently—which has been the goal since the ESG concept was introduced in the 1990s. The Navy may even wish to consider the return of task forces led by light carriers, such as the well deck-less LHA-6 and -7, loaded with unmanned aerial vehicles. They could focus more on scouting, while EMRG gun- and missile-equipped ships took the lead on strike missions. 6 None of these alternate combinations can replace the inherent and awesome capability of a full-up CSG, but they will certainly add to projectable American naval power and provide additional littoral options and overall greater flexibility—especially when something less than a nuclear-powered carrier would do or when the big flattop is otherwise occupied.
Guns were the arbiter of naval power for arguably 500 years. Starting about 100 years ago, aircraft, submarines, torpedoes, and then missiles surpassed them. But new developments hold the near-term promise of returning the naval gun to a place of prominence. Strategists, operators, and tacticians should begin to factor this into their planning for the not-so-distant future Navy.
1.155mm/62 (6.1”) Advanced Gun System, 11 November 2012, www.navweaps.com/Weapons/WNUS_61-62_ags.htm  .
2. The primary source for the tables was www.navweaps.com  , though many other websites were consulted to develop entirely open-source data for illustrative and comparison purposes. Any errors in the data are the author’s.
3. LCDR David A. Adams, USN, “Railguns are Revolutionary,” U.S. Naval Institute Proceedings , vol. 129, no. 2 (February 2003), 33–37. Edward Chen, “Railguns: A Revolution in Naval Warfare from the World of Science and Fiction,” Dartmouth Undergraduate Journal of Science , Spring 2007, 7–10.
4. VADM Kevin P. Green, USN (Ret.), “Get Serious about Naval Gunfire Support,” U.S. Naval Institute Proceedings , vol. 136, no. 5 (May 2010), 48–52.
5. CDR Phillip E. Pournelle, USN, “The Rise of the Missile Carriers,” U.S. Naval Institute Proceedings , vol. 139, no. 5 (May 2013), 30–34. CAPT Wayne P. Hughes, USN (Ret.), Naval Post Graduate School Principle Investigator , “New Navy Fighting Machine: A Study of the Connections Between Contemporary Policy, Strategy, Sea Power, Naval Operations and the Composition of the United States Fleet,” August 2009, 45–50.
6. CAPT Wayne P. Hughes, USN (Ret.), “New Navy Fighting Machine: A Study of the Connections Between Contemporary Policy, Strategy, Sea Power, Naval Operations and the Composition of the United States Fleet,” 17–21 and 28–33.