The officers and crew of the USS Cheyenne (SSN-773) knew their proud ship was about to be destroyed. They had sunk four enemy warships and a submarine on the current patrol, but now a helicopter and maritime-patrol aircraft (MPA) were hounding them from above. The Cheyenne couldn’t outrun the aircraft, and because she had sailed into shallow waters, she couldn’t go deep to evade them, either. The MPA prepared to launch a torpedo at the submarine as the hovering helicopter provided guidance with its dipping sonar. The officer of the deck watched helplessly through the periscope as the MPA opened its weapons-bay doors, when suddenly the skipper bellowed, “Launch the Flyswatter!”
The torpedoman acknowledged the order, quickly loaded a Mark 1 SubSurface-to-Air Missile (SSAM) “Flyswatter” canister into the 3-inch countermeasures system, and pressed the launch button. As the Cheyenne sped up and maneuvered again to throw off the enemy, the canister floated to the surface. A modified Stinger missile burst from the canister and started its flight along course 320º, using a bearing supplied from the periscope. It quickly acquired the large hovering helicopter, homed in on its target, and brought it down with a fiery explosion.
Meanwhile, the circling MPA witnessed this destruction and rapidly gained altitude and speed to put distance between itself and the surprising new threat. This momentary lapse provided the Cheyenne the few crucial minutes she needed to break contact, reestablish her stealth, and live to fight another day. . . .
This hypothetical situation illustrates how U.S. submarines can be vulnerable if discovered by enemy aircraft while in shallow water. By developing a missile to either destroy or deter enemy aircraft, U.S. submarines can be provided a means to “swat” away aerial threats. If that missile can be fired from the ship’s countermeasures system, it will enhance the submarine’s defenses while not costing it any offensive firepower, in contrast to many of the options currently being developed for this mission.
Eliminating a Remaining Vulnerability
From its inception through today, the submarine’s most important characteristic has been its stealth. Commander Robert Smith described this vital factor in his Proceedings General Prize Essay Contest winner in 1966:
What is it, then, that defines the submarine? It is not speed. There are ships that go faster. Nor is it weapons. The submarine possesses none that cannot be carried in other hulls. Least of all is its defensive strength. The submarine is a heavyweight, but it has a glass jaw. The unique attribute of the submarine, from which all its other virtues flow, is simply its ability to hide in the sea.1
Since World War II, submarines have eliminated many of their stealth vulnerabilities, making them even more fearsome weapons today. World War II submarines were less capable submerged, so generally operated on the surface. This exposed them, however, to radar detection and aircraft attacks. Grand Admiral Karl Dönitz, who directed German U-boat operations throughout the war, described the impact of these two forces in his war diary in 1943, writing, “The enemy radar location device . . . is together with enemy aircraft at present the worst enemy of the U-boat. . . . The location device is robbing the U-boat of its most important characteristic, its undetectability.”2 Of course, modern submarines no longer operate on the surface, eliminating this massive weakness. Radio direction-finding provided another primary means that antisubmarine forces could locate enemy submarines. Today’s submariners, however, understand the risk they run every time they transmit, and have learned from the mistakes of Admiral Dönitz and his U-boats.3 This eliminates another flaw in submarines’ stealth, making them even more deadly today.
If today’s submarines are found by the enemy, in most cases they can still effectively defend themselves. A submarine located by an enemy surface or subsurface vessel can launch its own weapons or sprint away to reestablish its stealth. If that same submarine is tracked by antisubmarine-warfare (ASW) aircraft, it can go deep in an effort to break contact. Thus, in the vast majority of situations it is extremely difficult for ASW forces to find a submarine, but if they do that boat still has many ways in which it can defend itself.
Yet there is one important situation in which modern submarines are still vulnerable. If a submarine is detected by aircraft in the littorals, it cannot outrun the enemy, cannot hide by going deep, and cannot shoot back; neither fight nor flight is a viable option. To complete the submarine’s dominance of the oceans, both shallow and deep, the U.S. Navy needs to devise a means of destroying or deterring airborne threats before they can attack our submarines.
Design Goals
To solve this problem, the Navy should develop what could be called a “SubSurface-to-Air Missile,” or SSAM. When developing this system, the following goals should be kept in mind:
Keep it simple, sir: Shooting down aircraft is not a submarine’s primary mission, and so the SSAM should be developed strictly as a last-resort weapon, to be used only when being followed and attacked by enemy aircraft and without means of escape. It should not be intended as a means to go on the offensive against aircraft, nor should it be designed to interface with Aegis or any other friendly platforms.
Targeting: The SSAM only needs to be able to hit relatively easy targets like hovering helicopters and large MPA; fighter jets and high-altitude bombers are not a threat to the submarine.
Size: The SSAM should be small, so that it can be easily stored, loaded, and fired, and does not force the submarine to carry fewer torpedoes, land-attack missiles, or torpedo countermeasures.
Infrastructure: The system should be developed to require minimal submarine alterations. No new firing ports or hull penetrations should be required, thus keeping down costs.
Technology: The SSAM should rely, as much as possible, on existing technology to reduce development expenses and time. Compared with the technology involved in shooting down exoatmospheric ballistic missiles and sea-skimming cruise missiles, the technology needed to shoot down a nearby hovering helicopter is relatively simple.
Minimal operating restrictions: If the submarine is attempting to escape from aircraft, going fast and deep are still its best options. Thus, the SSAM launch should not restrict the submarine’s speed or depth. Furthermore, it should be a simple device that does not require complicated officer and crew preparations and operation; they will likely have their hands full already.
Minimal opportunity cost: The submarine’s primary mission is to destroy enemy ships and land targets with its torpedoes and Tomahawks, so the SSAM should not be fired using these launch systems. Most U.S. submarines have four torpedo tubes, meaning that if a SSAM has to be loaded there the ship’s offensive capability is cut by 25 percent at any one time. It is critical to develop a way to launch the SSAM so as to not weaken the submarine offensively.
Starting with these goals for a modest yet capable SSAM, the Navy can develop a relatively inexpensive weapon that does not replace precious torpedoes, Tomahawks, or countermeasures, yet can be quickly loaded and fired in the hopefully unlikely event an American fast-attack is trapped and threatened by enemy aircraft.
Current Work
Several individuals and defense contractors have recently made impressive efforts to give submarines a method of shooting down aircraft, but many of these proposed weapons have serious drawbacks. Some attempts have envisioned a launch system in the submarine’s sail, such as the Submarine Short-Range Defense System patented by C. Roger Wallin through the Naval Undersea Warfare Center (NUWC) and the “Anti-Air Weapon for Submarines” being developed by the French company DCNS.4 In these systems, the submarine would extend a mast near the water’s surface and then launch a missile at the target. However, this would require extensive modifications to submarines’ sails in order to install and operate the mast. More important, this would make the submarine more vulnerable by forcing it to slowly operate at periscope depth as it prepared and raised the mast and then fired the weapon. These systems are interesting, but the expense and the limitations they put on the ship are serious issues.
Alternatively, the German company Diehl is developing the Interactive Defense and Attack System for Submarines (IDAS).5 This system uses a canister containing four missiles loaded in a torpedo tube. Once fired, the missile accelerates to the surface and then attacks targets such as ASW helicopters or surface vessels. It can be guided by the submarine via a fiber-optic cable and has a range of approximately 12.5 miles.6 In addition, Raytheon has been developing a submarine-launched AIM-9X Sidewinder, which appears to be designed to be fired from the ship’s vertical launch system (VLS). In a 2005 test, an AIM-9X was launched from a stationary vertical platform and was able to successfully track and destroy a slow-moving helicopter drone.7 In 2009, Raytheon, Northrop Grumman, and NUWC successfully launched an AIM-9X test missile shape from a submerged Tomahawk capsule-launching system.8
Both the IDAS and submarine AIM-9X look to be highly capable systems with excellent chances of destroying enemy aircraft—but at what cost? There is no free lunch, and in this case the submarines must sacrifice some of their offensive firepower to carry and deploy these weapons. That is a tradeoff they should not make. Submarines are amazing platforms for destroying enemy warships, but they are not ideal for shooting down aircraft. Just because the technology now exists to perform this function does not mean it should be attempted at the expense of the antisurface, antisubmarine, and strike missions.
Virginia-class submarines are likely the best submarines in the world, and are capable of carrying about 27 torpedoes and missiles for launch through their torpedo tubes, and 12 Tomahawk missiles in their external VLS.9 If the only Tomahawks they carry are in their VLS, then forcing them to carry even one AIM-9X would reduce their strike capability by more than 8 percent. Similarly, if the AIM-9X can be launched through the torpedo tubes, carrying just one would cut the submarine’s torpedo inventory by almost 4 percent. That is too large an opportunity cost for how capable the Virginia class is, and so there must be a better solution rather than weakening our own ships’ offensive capabilities. The surface fleet’s cruisers and destroyers must often sacrifice their formidable offensive firepower to carry defensive missiles to protect the aircraft carrier. The submarine fleet should not follow this example, but should look for ways to better boats’ defenses without weakening their offensive punch.
Enter the ‘Flyswatter’
To accomplish the design goals outlined above, the submarine fleet should develop a weapon launched from the ship’s internal 3-inch countermeasures system, based on a hybrid of a Submarine-Launched Expendable Bathythermograph (SSXBT) and either the FIM-92 Stinger missile or the Thales Starstreak missile. By relying on proven technology and keeping the design goals humble, submarines can be provided with a flexible, easily deployed weapon that will not take the place of a torpedo, Tomahawk, or countermeasure.
The SSXBT is a probe launched from submarines’ 3-inch countermeasures systems that provides a sound velocity profile by floating to the surface, deploying a sensor, and relaying the information back to the submarine via a wire.10 Replacing the sensor apparatus with a missile would yield a convenient means of protecting the missile from sea pressure while getting it to the surface. The SSAM would certainly be heavier than the SSXBT, but adding a simple floatation device that inflates using a small CO2 canister would ensure the entire system would be positively buoyant. The SSXBT has a cable assembly that feeds through the breech door, meaning it could be reengineered as a way to pass last-minute targeting data to the missile, such as a periscope bearing to a hovering helicopter. The same guillotine assembly already on the SSXBT could be used to cut the wire once the missile is away, or to allow the submarine greater mobility as it tries to evade the enemy.11 Finally, the same sensor that determines when the SSXBT has reached the surface and that controls sensor deployment could be used to initiate missile launch.
Using a modified Stinger missile would provide additional advantages but require some important modifications first. The Stinger has been effectively used for decades, is lightweight, and is relatively inexpensive. Its diameter of 2.72 inches means it could fit into the countermeasures system with enough room for the surrounding canister walls. However, at 5 feet in length, it is too long to fit into the 3.2-foot SSXBT body.12 This is most likely the largest challenge, but could be overcome by reengineering the 30-year-old missile using smaller hardware or by sacrificing some of its approximately 3-nautical-mile range.
An even better option is the British Starstreak close-air defense missile. Currently deployable from land, sea, or air platforms, the Starstreak accelerates to Mach 3 in less than one second. It deploys three separate fragmenting warheads that are laser-guided to the target by the main missile body, is designed to attack targets with short exposure times such as very close helicopters, and has an impressive 4-nautical-mile range. The original Starstreak, however, is slightly too large for the 3-inch countermeasures system, although it is approximately 5 inches shorter than the Stinger.13 This problem could be overcome by eliminating the first-stage rocket that propels the weapon out of the launch tube. This first-stage rocket extinguishes before exiting the launcher so as to protect the human operator, but is unnecessary when the missile is canister-launched at sea. The size could be further condensed by reducing the number of projectiles to two instead of the current three. The ship-based variant is called the Seastreak; the SSAM variant could be known as the Substreak.
Both the conventional Stinger and Starstreak are aimed at their target before firing, so the SSAM design would have to address this issue. The best solution would be to supply the missile with an initial bearing to fly, and then let it acquire its target once in flight. This bearing could be supplied by the periscope or sonar before launch, or while the canister rises to the surface through the connecting wire. In addition, getting the missile to successfully deploy out of the canister while vertical could be challenging, but it would not be drastically different from these missiles’ normal launch method.
In the unlikely event there is space remaining, a beacon, similar to the Submarine Emergency Position Indicating Radio Beacon, could be added to the canister.14 This could provide coordinates and signal that a U.S. submarine was under aerial attack as a means to call for friendly air support to fend off the threatening aircraft. The submarine’s location already would have been revealed to the enemy, so communicating would not do further damage and could potentially provide some relief. Something as simple as a commercially available emergency beacon, such as the tiny 116-gram Ocean Signal RescueMe device, could do the trick.15
SSAM Advantages, Potential Problems
The SSAM would have several important advantages over systems currently in development, including the VLS-launched AIM-9X. Considering the design goals mentioned earlier, the SSAM would meet every one of them, but its biggest question is its technical feasibility given the size constraints.
Most important, the SSAM would not sacrifice the submarine’s offensive firepower. Furthermore, by using the internal countermeasures system, the ship would not have to sacrifice a torpedo countermeasure. Their small size would allow them to be rapidly interchanged, and would also allow numerous SSAMs to be carried instead of just one or two Sidewinders.
The SSAM is also an attractive option because it would have a minimal effect on the submarine’s and crew’s operations. Whereas an AIM-9X launch would require the submarine to complete a long procedure at slow speeds at periscope depth when it should be evading the aircraft, the SSAM can be easily launched “over the shoulder” and with minimal speed or depth restrictions. Furthermore, the SSAM can be launched by a single torpedoman instead of requiring the attention of several watch officers, allowing them to focus on evading the threat.
Finally, the SSAM would get the job done while not being overly ambitious. The Sidewinder is certainly a more capable and advanced weapon, but the submarine is not a fighter jet, nor should it attempt to be one. The Stinger and Starstreak also have good track records, and although limited in range they would be enough to buy the submarine time to escape. Even if the missile misses, any helicopter pilot is going to think twice about conducting a low hover to deploy his dipping sonar when he knows he’s a sitting duck for the next attack. When a fly is buzzing around your head, it is great if you can kill it with a flyswatter, but sometimes shooing it away is enough.
This is admittedly a very rough design. There are challenging obstacles to overcome, such as how to condense the missile’s length, perfecting the launch from a floating canister, and the initial targeting after launch. By relying on existing proven systems such as the SSXBT and taking advantage of the work already being done at NUWC, however, the SSAM “Flyswatter” could help mitigate one of the modern submarine’s last remaining vulnerabilities.
1. CDR Robert H. Smith, Jr., USN, “The Submarine’s Long Shadow,” U.S. Naval Institute Proceedings, vol. 92, no. 3 (March 1966), 30–39.
2. Peter Padfield, War Beneath the Sea: Submarine Conflict During World War II (New York: Wiley, 1995), 331.
3. CAPT William Hoeft, Jr., USN (Ret.), “In the Deep, Run Silent Again” U.S. Naval Institute Proceedings, vol. 139, no. 1 (January 2013), 12.
4. C. Roger Wallin, “Submarine Short-Range Defense System,” US Patent 7779772, filed 25 June 2007, issued 24 August 2010. “DCNS Innovates with a New Weapon System for Submarines: Anti-Aircraft Self-Defence,” DCNS Group press release, 26 October 2012, http://en.dcnsgroup.com/news/dcns-innove-avec-un-nouveau-systeme-darmes-pour-sous-marins-lautodefense-anti-aerienne/.
5. Norman Friedman, “Maritime Vulnerability,” U.S. Naval Institute Proceedings, vol. 135, no. 1 (January 2009), 90–91.
6. “IDAS: The Revolutionary Multi-Role Weapon for Submerged Submarines,” Diehl Defence, 16 January 2016, www.diehl.com/fileadmin/diehl-defence/user_upload/flyer/IDAS_07_2008.pdf.
7. “Successful Test of an AIM-9X Missile by a Raytheon-Led Team Demonstrates Potential for Los Cost Solution in Littoral Joint Battlespace,” Raytheon Company press release, 6 February 2006, http://investor.raytheon.com/phoenix.zhtml?c=84193&p=irol-newsArticle&ID=813037.
8. “Raytheon-Led Littoral Warfare Weapons Team Demonstrates Successful Underwater Launch,” Raytheon Company press release, 14 September 2009, http://investor.raytheon.com/phoenix.zhtml?c=84193&p=irol-newsArticle&ID=1331411.
9. Norman Polmar and Richard R. Burgess, The Naval Institute Guide to the Ships and Aircraft of the U.S. Fleet, 19th ed. (Annapolis, MD: Naval Institute Press, 2013), 73.
10. “Submarine-Launched Expendable Bathythermograph,” Lockheed Martin, September 2005, www.sippican.com/stuff/contentmgr/files/a704392149ca51dbe166f1b20bbf91c0/sheet/ssxbt92005.pdf.
11. Ibid.
12. E. R. Hooten, Jane’s Naval Weapon Systems: Issue Forty-Two (Alexandria, VA: Jane’s Information Group, 2005), 453. Lockheed Martin, “Submarine-Launched Expendable Bathythermograph.”
13. “StarStreak II: High Velocity Missile (HVM),” Thales Group, November 2010, www.thalesgroup.com/sites/default/files/asset/document/Thales%20HVMII%2011_10.pdf. Hooten, Naval Weapon Systems, 441.
14. “T-1630 Sepirb,” Ultra Electronics Ocean Systems, December 2005, www.ultra-os.com/images/pdf/sepirb.pdf.
15. “Ocean Signal RescueMe PLB1,” Datrex product description, www.datrex.com/index/catalogdetail/pdt_id/1049.