Most naval antiballistic missile system proposals are built around the Standard missile, but a more cost-effective alternative might be found in the Mk 45 5-inch/54 caliber naval gun.
Since the Gulf War, a number of articles have appeared in Proceedings on the proposed naval antiballistic missile (ABM) system.1 While lacking in specific performance information, they have broken the concept down into a lower-tier capability, using a modified Standard SM-2 Block IV (A) missile, and an upper-tier exo-atmospheric capability based around a modified Standard carrying a kinetic kill warhead or something that can fit in a Mk 41 vertical launcher.2 What they have overlooked is what may well be a better ABM system, the Mark 45, single 5-inch (127 mm) L/54 medium-caliber dual-purpose naval gun.
The last time guns were considered openly for use as ABM weapons was in the late 1960s and early 1970s, during the development of the Safeguard system. At that time, the discussions centered around the work of Dr. Gerald Bull and his High Altitude Research Project (HARP).’ During the early 1960s, Bull was able to fire a 6-kilogram (kg) projectile to an altitude of 45 kilometers (km), using a modified 4-inch (157-mm) antiaircraft gun. A modified 16-inch (406-mm) naval gun fired an 84-kg projectile to 180 km.4 Bull proposed a gun-based ABM system deployed around U.S. population centers and firing both smart (radar- guided) and dumb rounds. A single dumb round would provide a kinetic kill capability by releasing a cloud of ball bearings in the path of incoming missiles.5
Today, the Navy intends to use modified Standard SM-2 Block IV missiles to engage theater ballistic missiles (TBMs) within the atmosphere (typically below 20 km altitude). While it is not specifically stated, the Navy likely will follow the Army’s Patriot ABM practice of firing two missiles—costing more than $600,000 each—at each incoming target. This is because the target missile cannot be reengaged should the first engagement fail.
To perform in the ABM role, the Standard SM-2 Block IV missile will be modified to incorporate a more effective warhead (larger shrapnel size), a multimode seeker (semi-active and infrared), and an improved fuze.6 These are many of the same modifications considered for the Patriot missile after the Gulf War. The Army later dropped this approach in favor of the ERINT kinetic-kill vehicle, in part because of the lack of an assured kill using a fragmentation warhead.7 For example, during the engagement of a chemical-submunition-armed Scud missile, a fuzing delay of 0.001 second would move the center of the warhead blast 2.1 meters.8 For the 11-meter Scud, this might place the majority of the blast damage behind the warhead, leaving the chemical payload intact.
Plans for the Navy’s upper-tier capabilities are less clear. It likely will use the Lightweight Exo-Atmospheric Projectile (LEAP) kinetic-kill vehicle. How to propel the 22-kg projectile hundreds of kilometers into space is under consideration.9 Candidates include a modified Standard SM-2 Block IV missile, a modified Army Theater High Altitude Air Defense System (THAADS) missile, or something designed from scratch. Navy use of the THAADS missile would mean a return to liquid-fueled missiles, after a lapse of almost three decades. Development of the naval upper-tier capability can be expected to be lengthy and expensive.
When considering the lowly Mk 45 naval gun for an ABM role, a number of obvious questions arise. Does the Mk 45 have the needed range? Can an ABM projectile be fitted into a 5-inch diameter package? Can it take the approximately 20,000 Gs involved in being fired from the Mk 45? Will it perform at least as well as the Standard SM-2 Block IV (A) missile? Finally, can a cost-effective weapon be delivered in time? The short answer is “probably” for the lower-tier capability and “probably not” for the upper tier.
The Mk 45 is capable of firing a 32-kg projectile at 807 meters per second to a height of 15 km and a distance of 23.6 km, with a rate of fire of 16-20 rounds per minute and a traverse capability of 340°.10 The Standard SM-2 missile has a maximum altitude of more than 20 km, with a range capability in excess of 56 km (30 nautical miles). Use of sabot configurations with base-bleed or rocket-assisted projectile technologies can increase the range of the Mk 45, but without incorporating radical changes to the gun system, the Mk 45 will never achieve ranges near those of the SM-2. For the lower-tier ABM capability, though, it doesn’t need them.
A review of Patriot performance during the Gulf War indicates that most ABM engagements occurred at relatively short ranges, under 20-km slant range." This is the result of detection ranges around 100 km or less and intercepts below 20 km. The radar detection range and the velocity of the incoming missile are the keys to determining when a firing solution will be made and from that, where the intercept will occur. Given that the Patriot is faster than the SM-2 and has comparable radar capabilities, the 20-km slant range for the lower-tier ABM envelope should be realistic. This is an envelope the Mk 45 should be able to fill, using lightweight, saboted projectiles that incorporate base-bleed and rocket-assist technologies.
Next, we must address the need to fit an ABM seeker and kill vehicle into a 5-inch diameter package. The Standard SM-2 Block IV (A) missile will use a dual semi-active radar and infrared seeker to target theater ballistic missiles.12 Within the fleet, a comparable missile design in a smaller package is available in the RIM-116, Rolling Airframe Missile. A lightweight, supersonic, quick-reaction, point-defense missile, the RIM-116 uses a dual passive radio frequency and infrared guidance system, packaged in a 5-inch airframe.13 The British Starstreak man-portable surface-to-air missile (which is being considered for an ATBM role) uses three laser-guided sub-projectile “maneuverable darts” to achieve a high success rate—all in a 5-inch diameter package.14
In the field of advanced artillery munitions, the BONUS/155 projectile, produced by Bofors, packs two multiband infrared-guided submunitions into a 155-mm round. The German SMART 155 projectile uses a multichannel infrared/millimeter wave sensor. The 120-mm Strix mortar round uses an infrared guidance package, and the 81-mm Merlin mortar shell uses a millimeter wave sensor.15 For the Mk 45, both semi-active laser and infrared seekers were developed in the 1980s; a command-guided, anti-cruise-missile projectile called the Terminal Defense Round was proposed in the early 1990s; and a GPS-guided fire support round currently is under development.16
The ability to develop and harden complex seeker packages is quite advanced. Developing new or adapting existing seeker packages for a 127-mm ABM precision-guided projectile (ABMPGP) should be technically achievable. Development of a dual-mode seeker similar to the SM-2 Block IV (A) would be more challenging.
Given the high closing velocities (up to 6,000 meters per second) of an ABM engagement, guidance, seeker field of view, targeting accuracy, and weapon maneuverability are key issues. With accurate targeting data from the Aegis system, the time delay between weapon firing and missile intercept can be a factor in system performance. The near instantaneous acceleration of the Mk 45 ABMPGP to perhaps more than 1,000 meters per second will minimize corrective maneuvers needed to counter atmospheric effects and TBM maneuvering.
Even with high velocity, some vehicle maneuverability will be required to ensure a kill. For the smaller Mk 45 ABMPGP kinetic-kill vehicle, high maneuverability over the entire ABM envelope is essential. The Standard SM-2 uses tail-mounted airfoil controls, as does the Navy 5-inch and Army 155-mm Copperhead semi-active guided, antiarmor projectiles. Numerous small solid-propellant side thrusters could provide needed maneuverability, even in the upper altitudes, where airfoil performance falls off. The OTO Breda 76-mm course-corrected shell uses six small rocket motors and uplinked guidance commands to make course corrections.17 The Naval Surface Warfare Center at Dahlgren and Lockheed Martin have developed a 60-mm “small-caliber smart munition” that uses a K-Band up-link and S-Band down-link for guidance control and solid-propellant thrusters to give the round a 40-G maneuvering capability.18 Use of similar solid-propellant side thrusters could maximize ABM maneuverability and reliability while simplifying system design and lowering projectile weight.
The Navy has yet to define its engagement policy, but the SM-2 Block IV (A) probably will be salvoed in pairs to achieve an acceptable possibility of a single-shot kill. Any Mk 45 ABMPGP system will have to equal or exceed this performance.
A fragmentation warhead is possible in a Mk 45 ABMPGP, but it would bring with it all the fuzing shortcomings inherent in the SM-2 Block IV (A). Jettisonable kinetic-kill penetrators could improve kill potential while virtually ensuring a TBM warhead impact.19 This is the technique used by the Starstreak. Any fuzing required in the kinetic kill vehicle is used to increase the number of large fragments before impact and does not rely on blast or overpressure to damage the incoming missile. Fuzing errors are therefore less critical. With a highly accurate, lightweight, maneuvering projectile, the possibility of a single-shot kill for the Mk 45 ABMPGP may equal or exceed that of a Standard SM-2 Block IV (A).
The possibility of a single-shot kill for each potential round will be determined by seeker type, sensitivity, field of view, projectile speed, and maneuverability. With the 20-round-per-minute firing rate of the Mk 45 system, multiple ABMPGP rounds can be used to engage a theater ballistic missile. Up to seven Mk 45 ABMPGPs could engage a single target, given a Scud-type missile aimed in the general vicinity of the ship, detection by the SPY-1 radar at something more than 100 km, and engagements commencing at 20-km altitude and continuing to 5 km.
The lower-tier Standard missile will be a multimode missile, with an ABM, antiaircraft, and antiship role. The Mk 45 ABMPGP also might be a multimode system; given the high velocity and accuracy of the round, it may be capable of antiaircraft and anticruise-missile roles. Having designed a maneuverable rocket-assisted projectile with a seeker optimized to engage theater ballistic missiles, it should take a much smaller effort to design and field a family of Mk 45 precision-guided rounds. The infrared seeker for the FIM-92A Stinger is 70-mm (2.75 inch), the AIM-9 Sidewinder is 127-mm (5 inch), and the Strix mortar round is 120-mm. These small infrared seekers, coupled with the seekers of the Starstreak, RAM, Merlin, BONUS, and others, offer the possibility of firing a round tailored for the specific target. It would not replace the Standard SM-2 missile, but a MK 45 smart round might offer a low-cost alternative with superior performance in specific engagement envelopes.
Should the Mk 45 ABMPGP meet or exceed the ABM performance of the SM-2 Block IV (A), the relative cost-effectiveness of the two systems must be considered. The SM-2 Block IV currently is in initial low-rate production.20 Production of the SM-2 Block IV (A) will not begin until at least fiscal year 1998, with the upper-tier capability fielded at a date yet to be determined. The RIM- 676 SM-2 Block II missile has had a unit cost varying from $525,000 to $601.000.21 Full-scale production of the SM-2 Block IV with the ABM modifications easily could drive these costs higher. Assuming a cost of $700,000 for the Standard SM-2 Block IV (A) and a two-missile salvo per target, each engagement would cost $1,400,000.
Estimating the cost of a yet-to- be-developed Mk 45 ABMPGP is more difficult. Government estimates typically are based on costs for systems of similar complexity. For the Mk 45 ABMPGP, these might include the RIM- 116A, the Starstreak, the M-712 Copperhead, the SMART 155, BONUS, Merlin, and Strix.
The last per-unit cost of the semi-active laser-guided 155-mm Copperhead projectile was $37,000.22 The RIM-116A dual passive radio frequency/infrared guidance missile has an estimated per unit price of $166,000, and the Starstreak has a $107,000 per-unit cost.23 Serial production prices for the BONUS, SMART 155, Strix, and Merlin are estimated at $12,200, $9,200, $18,900, and $15,730 in 1994 dollars, respectively.24 Costs for the Mk 45 ABMPGP will be determined by the amount of design reuse (off-the-shelf technology such as propulsion and controls) and production quantities. Assuming a per-unit cost of $150,000-$200,000 (based on RAM and Starstreak figures), seven to nine projectiles could be fired for the same cost as two Standard missiles. Using a production cost closer to the $15,000 Merlin, the gun-fired projectile may be cost effective even when compared with the ABM modifications being incorporated into the Standard SM-2.
When compared with the Standard SM-2 Block IV (A), the gun-fired round would appear to offer performance and costs advantages in the lower-tier ABM role. All Aegis-associated design efforts currently under way for the Standard ABM capability will be applicable to the Mk 45 ABMPGP. Incorporating the proposed Advance Naval Gun modification to the Mk 45 would increase the gun’s rate of fire to 40 rounds per minute or 14 rounds during a Scud engagement.25 With development and possible deployment of the regenerative liquid-propellant 155-mm gun by the Naval Surface Warfare Center, the technology from the Mk 45 ABMPGP could be fielded on the future SC-21 destroyer. With a range of as much as 138 km, this new gun, coupled with base-bleeding and solid-rocket technology, could increase the capabilities of the ABMPGP significantly.26 Should a rapid fielding of the Mk 45 ABMPGP be required, a hardened variant of the Starstreak with a more powerful laser bore- sighted and interfaced to the Aegis fire-control radar would be a likely candidate, as would a round using the guidance and thrusters of the small-caliber smart munition and a terminal infrared seeker.
The Mk 45 ABMPGP should meet the Navy’s requirement for a lower-tier ABM capability, but it is inadequate for the upper-tier capability, which includes engagements at ranges of hundreds of kilometers. According to published reports, the Navy upper-tier ABM capability will be deployed on board Aegis-equipped Ticonderoga (CG-47)-class cruisers and Arleigh Burke (DDG-51)-class destroyers. One article listed a 122-missile capability for the cruisers and 90-missile capability for the destroyers, but these numbers are somewhat misleading.27 If the lower-tier Standard missile were loaded into every slot of the vertical launcher, it would exclude a number of other missile systems, such as Harpoon, Tomahawk, and the future land-attack missile.
The upper-tier missile, with its 22-kg LEAP kinetic kill projectile obviously is not a multimode weapon system, and the ship’s weapons loadout should reflect this. Filling 20% of a Ticonderoga's missile loadout with upper-tier ABM missiles would provide a 25-missile capability, which wouldn’t last long against an enemy with a respectable launch capability, such as North Korea. Only when the ship is located well behind the battle lines will it be able to be loaded almost exclusively with upper-tier ABMs.
The upper-tier capability envisioned by the Navy relies on the small LEAP kinetic kill projectile. When used against relatively unsophisticated systems such as the Scud, the LEAP should perform adequately, but with the proliferation of ABM systems (e.g., Patriot, SA-10, SA-12, and THAADS), corresponding TBM improvements can be expected. The use of simple decoys (gas- filled mylar dummy warheads) and submunition warheads will complicate exo-atmospheric ABM operations. The current Navy program will rely on the SPY-1 radar system to differentiate among these multiple targets, often at ranges of hundreds of kilometers, and will require precision directional control of the LEAP projectile to ensure a warhead kill. Use of submunitions will increase the importance of an exo-atmospheric system, since their release typically will occur after the missile reenters the atmosphere. While technically achievable, the Navy’s upper-tier program is complex and somewhat limited in capability.
There are three feasible gun-based alternatives to the current upper-tier missile design. The first option is to develop an exo-atmospheric capability around the 155-mm naval gun. With a range of more than 100 km, the 155-mm technology, coupled with a rocket-assisted projectile, might be able to place a 30-kg LEAP kill device above 30 km. This will be more assessable once the 155-mm naval gun program matures.
The second option is to develop an updated version of the Mk 71, single 8-inch (203 mm) Lightweight Gun Mount.28 The Mk 71 was developed and tested in the late 1960s as replacement for 5-inch guns on ships as small as destroyers. The rapid-fire (12 rounds per minute) system may be able to propel a LEAP or ERINT type warhead to the needed range and altitude using a rocket-assisted projectile or rocket-assisted/sabot configuration if the gun incorporates HARP features. This would be an expensive retrofit, but the Mk 71 system would go a long way toward satisfying the Marine Corps’ requirement for naval gunfire support.
The third, and perhaps quintessential, gun-based ABM system is built around the Mk 7 16-inch (406 mm) guns of the Iowa (BB-61) class battleships. The Mk 7 system can propel ABM projectiles weighing hundreds of kilograms into the upper atmosphere.29 In addition, the 16-inch Mk 7 would allow the use of active systems to counter decoys; for example, lightweight mylar decoys would be stripped away by a cloud containing hundreds of kilograms of fine sand or ash particles, allowing targeting and destruction of the warhead by follow-on projectiles. The technique also is environmentally safe.
With three turrets and nine barrels, a rate of fire of two rounds per minute, and a storage capability of 1,220 rounds, the battleship would be an exceptional ABM platform and easily would answer the needs of the Marine Corps.30 Using technology from the 1960s HARP program, modified (smoothbore, extended-barrel) 16-inch guns could fire rocket-assisted smart projectiles thousands of kilometers, giving the battleships strategic capabilities at bargain-basement cost.31 The obvious drawbacks to a 16-inch gun system are the limited number of battleships, the costs of maintaining and manning the ships, and the recent pressure to scrap the four ships remaining in the Navy’s inventory.
When the battleships go, the United States will lose a unique capability. Current plans are to equip all Aegis-capable ships with the upper-tier capability, but does the Navy actually need that many platforms? The upper-tier naval ABM system is spoken of as a strategic capability, with one cruiser able to defend Japan from the Korean threat. With a Standard missile-based system, equipping all Aegis-capable ships makes sense for logistics but not costs.
Prepositioning three battleships near potential ABM hot spots—the Mediterranean, the Persian Gulf, and in the Pacific near Korea—would allow a fairly rapid response to future conflicts. By placing the ships in the Naval Reserve Fleet, maintaining them at a minimum (maintenance) crew level, and mothballing the 5-inch gun systems, non-underway costs could be reduced. Targeting data could be provided via data-link from any Aegis-equipped ship. Training could be provided by the fourth battleship.
Following World War II, the military began to turn away from gun-based systems for all but bombardment and short-range air-defense missions. Today, with the advances in technology, the Mk 45 5-inch, naval 155-mm, Mk 71 8-inch, and Mk 7 16-inch systems offer great potential for ABM, antiaircraft, and surface applications. For the Navy, virtually everything required is in place. Like the famous German 88-mm antiaircraft/antitank gun of World War II, the naval gun should become truly all-purpose.
1 Willard G. Fallon, “Combating the Ballistic Missile Threat," U.S. Naval Institute Proceedings, July 1994, pp. 31-34; Capt. Rodney Rempt, USN, "Killing Scuds From the Sea," U.S. Naval Institute Proceedings, June 1993, pp. 52-58; and Cdr. John E. Carey, USN, “Fielding a Theater Ballistic-Missile Defense,” U.S. Naval Institute Proceedings, June 1993, pp. 56-58.
2 Fallon, p. 33.
3 William Lowthin, Arms and the Man (San Francisco: Presidio Press, 1991), p. 48.
4 G. V. Bull and C. H. Murphy, ParisKanonen—the Paris Guns (Wilhelmgeschutze) and Project HARP (Herford and Bonn: Verlag E. S. Mittler & Sohn Gmbh, 1988) p. 232.
5 James Adams, Bull's Eye, The Assassination and Life of Super gun Inventor Gerald Bull (New York: Times Books, 1992), p. 76.
6 Carey, p. 58.
7 Barbara Opal, “U.S. Army Orders Raytheon to Stop Work on Patriot,” Defense News, 31 October 1994, p. 3.
8 Theodore A. Postol, “Lessons of the Gulf War Experience with Patriot,” International Security, Winter 1991/92, vol. 16, no. 3, p. 129. Postol lists a terminal velocity of 2.3 to 2.4 km/sec for the Iraqi Scud variants used during the Gulf War. These have a terminal velocity 40% higher than the standard Scud B (1.7 km/sec).
9 Rempt, p. 56.
10 Jane’s Information Group, Jane's Weapons Systems, 1988-89, “Naval Guns & Rockets” (Coulsdon, Surrey, UK: Jane’s Information Group, 1989), p. 370.
11 For a detailed description of Patriot performance during the Gulf War, see Postol. pp. 119-71.
12 Carey, p. 56.
13 Jane’s information Group, DMS Market Intelligence Report, Missile Forecast, “RIM-116A RAM,” May 1994, pp. 1-10.
14 Jane’s Information Group, DMS Market Intelligence Report, Missile Forecast, “Starstreak,” May 1994, pp. 1-3.
15 Jane’s Information Group, DMS Market Intelligence Report, Ordnance & Munitions Forecast, August 1995, Merlin, Strix, SMART 155, and BONUS sections.
16 Technical information and history on 5-inch and 60-mm projectile development by the Naval Surface Warfare Center was provided by Mr. Dennis Hagan, with the approval of Capt. Jack Overton, commander of the Center.
17 Jack Kerrigan, “Munitions,” Defense News Marketing Supplement, July 1995. p. 24.
18 Norman Friedman, The Naval Institute Guide to World Naval Weapons Systems, 1994 Update (Annapolis, MD: Naval Institute Press, 1994), pp. 49-50.
19 All performance results are dependent on the geometry of the ABM engagement. The location of the target with respect to the TBM launch point determines its trajectory. Location of the ship, whether it is between the launch point and target (missile passes over the ship) or beyond the target (ABM missile/projectile has to travel to and beyond the target to intercept) is critical in determining the area coverage of any ABM system.
20 “RIM-66/67 Standard,” May 1994, pp. 1-17.
21 Ibid., pp. 11-14.
22 Ted Nicholas and Rita Rossi, U.S. Weapon Systems Costs, 1992, vol. 12, “M-712 Copperhead" (Fountain Valley, CA: Data Search Associates, 1992) pp. 6-8.
23 “RIM-116A RAM," p. 3, and "Starstreak,” p. 1.
24 Jane’s Information Group, Ordnance and Munitions Forecast.
25 E. R. Hooton, Jane's Naval Weapons Systems, 1994 (Coulsdon, Surrey, UK: Jane’s Information Group, 1994), p. 370.
26 "Martin Marietta Develops Naval Gun Technology,” Defense News, 28 November-4 December 1994, p. 21.
27 Rempt, p. 54.
28 Jane's Weapon System 1988-89, p. 369.
29 Carey, p. 57.
30 Jane 's Weapons System, 1988-89, p. 369.
31 Bull claimed that using rocket-assisted projectiles, a 272-kg payload could be fired more than 1,800 km. “Iraq: heir to HARP project?” Jane's Defense Weekly, 28 April 1990, p. 770.
Lieutenant Commander Denny, a Naval Reserve Intelligence Officer with NR JAC Molesworth 0167, is a civilian engineer with the U.S. Army Missile Command.