As a senior research engineer with Penn State University Applied Research Lab, I assure readers that I am not endorsing a specific design of the very lightweight torpedo, but rather highlighting the unique benefits that such a weapon could bring to a variety of missions in general.
Spring 2021
It was a sight not seen since the last world war. The largest armada of ships to sail into battle began to break through the early morning haze, 82 ships in all, including their newest carrier, commissioned just nine months earlier. The world was shocked at the events of the last year. Saber-rattling they called it. Little did they know that Operation Leaping Dragon had been in execution for more than three years. Two decades of planning were soon to come to fruition in a glorious and swift invasion. The Americans and their pompous claims to defend the rogue nation will arrive too late to be of any assistance. The occupation will be complete in three days, and the feeble U.S. carrier force will be more than two days away from the engagement.
The admiral, looking across the array of ships from the carrier bridge, could not help but smile at the brilliance of the events unfolding. He did not notice the beginning of the attack against his force. A seemingly imperceptible shift in the formation on the port side-two cruisers, a troop transport, and a destroyer began to slow, while another destroyer rolled into a hard port turn, as if in retreat. It was the crackle of radio reports entering the bridge that caused his attention to shift.
"Admiral," the young bridge officer announced, "the cruiser Razorback reports loss of all engines. The cruiser Fortune reports the same." The admiral turned quickly in the direction of the two troubled warships just as a destroyer collided with a supply ship, the destroyer's bow slicing deep into the side of the large vessel. A fire erupted. A shout from the starboard bridge shifted the admiral's attention to the other side of the armada. Four more ships were slowing rapidly, disrupting the formation as other ships maneuvered to avoid the stricken vessels. The admiral's mind raced-What is this? How could this happen to so many ships at such an inopportune time? Then he saw it—a small spray of water just astern of a cruiser, which then rapidly slowed. Something had exploded under the stern of that now-crippled ship. Within ten minutes, more than half of the ships in the mighty armada were dead in the water. Ten others had collided, causing one to settle rapidly by the bow and igniting a ferocious fire on the supply ship carrying fuel for the invasion force.
The reality of their situation came to the admiral some time ago; he was under attack from an unseen foe, a submarine, he surmised, or more accurately several submarines. But what was this new weapon that seems to disable rather than destroy? Several ships reported hearing high-speed screws of torpedoes, but the explosions, which disabled his fleet, were not the size typical of submarine-launched torpedoes. And for so many ships to be attacked in such a short period would mean he must be opposed by a fleet of such submarines. Not a single ship had been sunk by the attack, yet his entire force was in turmoil. Success was no longer a certainty. Yet turning back would bring dishonor and disgrace.
What the admiral didn't know would shake him to the core. Just two American submarines had carried out this attack, each using only four of its on-board torpedo inventory.
A Naval Scalpel
This is a glimpse of the potential for changing the face of undersea warfare. Up to now, submarine-launched weapons followed one axiom—bigger is better. The destructive force of one torpedo can break apart and sink a cruiser within minutes. A single cruise missile can level a multi-storied building. A ballistic missile can level a city. Submarines are rarely used in maritime intervention operations except in a supporting role because of the extreme damaging force of their arsenal. You cannot use an axe when a scalpel is needed.
The rapid advance of technology can provide the submarine with just such a scalpel. The opportunity exists to augment the destructive capability of large-warhead torpedoes with a small, highly accurate and agile torpedo, built to disable rather than destroy. The rapid sinking of an enemy ship leaves the foe with a significant loss but an easy decision: acknowledge their sacrifice but carry on with the mission. In contrast, the disabling of an enemy ship not only removes that asset from the pending fight, but also leaves the group commander with a strategic decision; leave the vessel behind, provide it a guard, or take it in tow. The latter two options remove other assets and slow the progress of the fight. If left behind, the vessel becomes an obstacle to other ships and disrupts the easy movement of the formation. In the confusion, collisions are possible, with added potential for fires and flooding.
Known as the Common Very Lightweight Torpedo (CVLWT), this new breed of torpedo is a small, short-range rapid-attack weapon. Pennsylvania State University Applied Research Laboratory is developing it under the sponsorship of the Office of Naval Research and the Undersea Defensive Systems Program Office, as an anti-torpedo torpedo. Required to be fast and agile, it is smaller than the current lightweight torpedo: 6.75 inches in diameter, about 9 feet long, and one-third the weight of the Mark 46 lightweight torpedo. The key to its performance is a state-of-the-art-processing architecture known as the Torpedo Intelligent Controller. This architecture uses a form of fuzzy logic to track multiple targets and find the target of interest with surprising accuracy.
The CVLWT can be designed to allow the launch platform to pre-program the attack point on the hull of the target ship (propellers, rudder, or a specific location such as a magazine or main propulsion space). This allows the selection of a less-than-lethal attack, where the target ship is disabled and the crew stranded with minimal loss of life. The weapon could be employed individually for short-range encounters, or in a multi-warhead, independently targeted configuration using the Mark 48 heavyweight torpedo propulsion for significantly longer range attacks. The combination of Mark 48 propulsion driven by the CVLWT guidance and control has been proven in dozens of in-water development tests. With its advanced sonar processing, the very lightweight torpedo has demonstrated proven performance in salvo launches and through collaborative tactics can independently target multiple units of an opposing force.
New ASW Tool
This capability is also highly suited for antisubmarine warfare when faced with a foe hiding in a rugged, shallow terrain or under the Arctic ice canopy. The multi-warhead configuration can be designed to target multiple potential contacts in the area of the hiding submarine, greatly increasing the opportunity of a hit. Although the smaller warhead may not sink the target submarine, it will inflict significant damage, which will make the sub react, thus flushing the prey from the security of its hiding place. Additionally, in situations where multiple false contacts are not an issue, the multi-warhead heavyweight weapon could target the single-threat submarine with all its CVLWTs, having them detonate at different locations along the submarine's hull.
The CVLWT employs a high power density, closed-cycle propulsion system that gives it very high speed and maneuverability over a significant range. Its compact size gives the added benefit of low weight and low cost as compared to most conventional lightweight torpedoes, making it suitable for employment by aircraft, ships, and submarines. Its high maneuverability and surgical accuracy allow employment of a much smaller warhead to render a consistent mission kill while minimizing human loss. The enemy becomes discouraged and defeated by their inability to transit the seas and press the attack.
The CVLWT would augment the current torpedo inventory, not be a replacement. The larger-warhead weapons are necessary to deal with warships and submarines that are already in position for attack, or continue to press the attack even after they are disabled. But the addition of this mid-level offensive capability increases the options available to the surface, submarine, and aviation communities in dealing with an aggressor in a more controlled manner when the political or strategic environment calls for limited engagement or modified restraint to defuse a volatile situation with minimal loss of life. It also could provide an effective defense to swarm tactics of small boats, allowing multiple engagements with a smaller weapon to rapidly reduce the number of units at sufficient standoff range.
Leveraging the Sub's Stealth
The value of this weapon shines through in classic maritime interdiction operations. In many cases, a submarine is the only platform positioned to observe illegal or terrorist-related activities on a ship at sea. This is because the presence of aircraft or surface ships is readily detected by the offending ship, and plans are altered. Once other forces are ordered in, illicit activity ceases, and participating ships depart before these forces arrive. A submarine armed with this type of weapon would allow the on-scene commander to order a disabling strike that would prevent the threat ship from escaping while minimizing loss of life. The disabled craft would be unable to evade surface forces, which could then board and seize cargo or personnel. For a hostage or highjack situation, this torpedo would disable the pirated ship, rendering it incapable of being used as a weapon similar to the airliners of 9/11. In an air-drop configuration, this same ability to disable a ship could be conducted by any number of aircraft or unmanned aerial vehicles.
Homeland security and port protection would also benefit from this torpedo. It could be employed from fixed launchers around domestic ports and vital shoreline facilities, such as power-generation plants, against rogue vessels. The same capability could be carried to foreign ports to provide protection to U.S. forces overseas. The very lightweight torpedo can augment other non-destructive security measures while providing a final line of defense if those methods fail. In these scenarios, the limited range of the weapon is a benefit to avoid attacks against friendly shipping in the area while providing maximum protection for the assigned facility.
The torpedo's lightweight design makes it ideally suited for employment from unmanned aerial vehicles. Its smaller size increases the number of torpedoes an aircraft can carry by a factor of three—an inventory advantage that any pilot will agree adds substantially to mission success. The torpedo is designed to minimize mutual interference when multiple weapons are employed. This increases the probability of a hit and reduces fratricide among weapons. With the ability of precisely selecting the point on the target to hit, the attacker can scale the level of attack based on the situation. This type of response would be valuable in some situations, such as the MS Achille Lauro passenger ship highjacking in 1985.
As the mission of our armed forces evolves from large, campaign-level actions against highly capable and armed forces to the asymmetric threats appearing today, it is necessary to transform our undersea arsenal to provide for limited engagement with effective disabling capability while minimizing casualties to passengers and crew who may be presumed innocent. A highly accurate, light-weight torpedo, which can be employed from a myriad of platforms, selectively attack multiple points along a ship or submarine hull, and deter the actions of both elite and rogue forces, is just the weapon that is needed for this new era of asymmetric warfare.
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Science and Technology = Options
By Captain Doug Marble, U.S. Navy
Picture a future naval battlespace where the commander chooses from a suite of integrated manned and unmanned systems allowing thoughtful placement of platforms and sensors, enabling greater situational awareness, and extending knowledge of the battlespace. High-payoff science and technology investments will breathe life into this vision. Providing warfighters the right tools is essential to winning on the battlefields of today and tomorrow.
Future defense strategy will require us to address our adversaries' anti-access strategies. These will likely include force value mismatches, such as mines. Antisubmarine warfare (ASW) is also rapidly encountering this as highly capable diesel-powered submarines proliferate and our ASW platforms are renewed with smaller numbers. Novel developments in computing, materials, communications, and environmental prediction can augment forces with off-board and autonomous systems.
During the past decade, steady focus on greater sensing autonomy has brought success in mine-countermeasures reconnaissance using autonomous underwater vehicles (AUV), low-power imaging sonars, and computer-aided identification. For littoral battlespace sensing, focus on persistent sampling gliders and AUVs to improve acoustic predictions has resulted in advances. All these technologies have helped explosive ordnance disposal and harbor search, autonomous hull inspection, and special operations.
These mission successes have encouraged a push into the most complex undersea mission-ASW. Off-board ASW systems present significant science and technology challenges: Can many distributed sensors provide large array effectiveness? Can power be conserved while preserving capability and increasing persistence? Can adaptive mobility effectively optimize sensing? How far can automation be embedded? Off-board systems business challenges are also important-fewer Sailors or the same number working elsewhere? Long-term costs relative to platforms?
Sound science and technology investments have given us options today—initial capabilities to perform straightforward unmanned mine countermeasures (MCM) and ASW missions. For MCM, multiple AUVs working in concert have surveyed, detected, and classified bottom, mine-like objects, cueing reacquisition vehicles, which take and transmit a close-up snapshot to a tactical control center. Other specialized platforms receive and execute clearance instructions—getting the Sailor out of the minefield. Hull inspection vehicles build maps as they navigate along hulls. A complete aircraft carrier hull search has been done in four hours. Docking stations for AUVs provide options for recharging power supplies and off-loading data.
Tomorrow's understanding of the physical environment will provide a tactical advantage and allow off-board sensors the ability to adapt to environmental changes. Research is increasing the fidelity of ocean/atmosphere specification so a commander will be able to view the predicted battlespace, and know the geophysical structure will assume that form at the appropriate time. Explicit descriptions of acoustic and electromagnetic variability will provide accurate decision aids for performance assessment covering the entire marine battlespace.
Low-power, off-board, fixed ASW sensors combining acoustic and magnetic sensing show great promise to autonomously classify subsurface targets. Mobile mixed-sensor surveillance clusters also promise to provide adaptive and self-maintaining barriers and open-ocean sensor fields which adjust density and change location under commanders' control. A goal of science and technology has been to unchain maritime patrol aircraft from line-of-sight, high-data-rate sonobuoy datalinks. Successful in-buoy processing enables satellite communication control of long-lived sonobuoy fields. Coupled with smaller sized sources, such a field provides a powerful multistatic active search system where detections enable rapid reacquisition and localization. Once detection is made and associated with a reasonably tight location, a vertical-takeoff unmanned aerial vehicle (VTUAV) from a littoral combat ship can complete the engagement. The vehicle will deploy with a new, lighter digital magnetic search sensor—the result of a decade of development—designed to penetrate to all submarine depths. A higher flying second VTUAV provides geophysical background removal and real-time communications with the ship. The contact is destroyed with a prompt-attack weapon, light enough to accompany the localization sensor, dropped near the target on command from the LCS.
Certainly manned platforms cannot cover the entire battlespace, and they are increasingly vulnerable to less expensive, highly capable mines and submarines. These new concepts provide an opportunity for U.S. naval forces to inexpensively add sensing and engagement power to the battle. Off-board systems aren't silver bullets and have yet to be wrung through acquisition, but there is hope that their elements will be cheaper than methods required to counter them, presenting their own form of asymmetry to potential opponents. This prospect alone should give our adversaries pause as they consider our future order of battle. Navy science and technology continues to press the issues of autonomy, efficient use of power, acoustic communications, and sensors.