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RUM-139 Vertical Launch ASROC (VLA)

The RUR-5 Anti-Submarine Rocket (ASROC) is a ballistic missile designed to deliver the Mk 46 Mod 5 torpedo to a water entry point. Navy surface ships employed the ASROC with two different payloads -- either a nuclear depth charge that used a W-44 nuclear device or the Mk-44 or Mk-46 lightweight acoustic torpedo. The ASROC weapons were relatively small devices designed to fit inside the distinctive eight-cell box launcher found on almost all cruisers and destroyers of that era. The rockets were about fifteen feet long, approximately thirteen inches in diameter, and weighed about a ton.

The very first CalTech program for the Navy was the Mousetrap anti-submarine rocket launcher. Building from that, the NOTS organization developed the Rocket-Assisted Torpedo (RAT) and finally the Anti-Submarine Rocket (ASROC). NOTS proposed the weapon as an alternative to a Bureau of Ordnance (BuOrd) request to its labs in 1955 to consider the potential for launching a nuclear depth charge from ASW ships. NOTS engineers, concerned with the inflexibility of a weapon that would turn conflict suddenly nuclear, proposed a rocket-propelled weapon with a payload either of a nuclear depth charge or a conventional acoustic homing torpedo, specifically the Mark 44. BuOrd agreed with the concept of weapons flexibility, and in 1956 began funding NOTS development of ASROC.

The nuclear depth charge configured ASROC was a relatively simple device, as it was nothing more complicated than a ballistic, unguided rocket with a depth charge as payload. The torpedo is a very sophisticated weapon, employing for its time, state of the art technology for the propulsion and guidance systems. The torpedo is about eight feet long, weighs about 600 pounds and is also carried in tubes on escort ships. After water entry, the torpedo powered up and chased the sub using either passive or active sonar.

When employing either weapon, the idea was to place the weapon as close to the predicted position of the enemy sub and let the weapon work as designed. In the case of the depth charge, after water entry, it simply sank and detonated at a preset depth. The resulting shock wave did the rest -- water doesn't compress, but sub hulls do.

One of the few shortcomings of ASROC was its launch mode. Fired from canisters at a fixed ballistic angle, ASROC could provide only limited coverage without turning the ship. With the advent of Vertical Launch Systems (VLS) on the Navy's Spruance, Ticonderoga and Arleigh Burke classes of ships, NOSC re-designed ASROC for vertical launch mode, enabling the weapon to provide 360-degree ASW standoff capabilities for those ships, plus the high rate of fire characterizing VLS weapons. The ASROC capability has been in the fleet since 1960, and it is currently planned to continue as a viable anti-submarine weapon until the year 2025.

The RUM-139 Vertical Launch ASROC (VLA) is intended to provide vertical launch-capable surface combatants (without ASROC rail launchers) with an all-weather, quick reaction, standoff antisubmarine weapon capability. It is installed in Aegis ships (cruisers and destroyers) with the Mk41 Vertical Launching System (VLS) and DD 963-class destroyers with Mk 41 VLS. VLA includes a solid propellant booster with thrust vector control (TVC) to guide the missile from a vertical orientation through a pitchover maneuver into a trajectory intended to deliver the torpedo to an aim point on the ocean surface.

Pre-launch commands for the VLA are provided by the ASW Combat System (ASWCS) which includes the Mk 116 Mod 6 (or 7) Underwater Fire Control System (UFCS), the Naval Tactical Data System (NTDS) data link receive capability, hull-mounted sonar AN/SQS-53B (the primary acoustic sensor for VLA targeting), towed tactical array sonar AN/SQR-19, data processor AN/SQQ-28 for sonobuoy data transmitted from a Light Airborne Multi-Purpose System (LAMPS) Mk III helicopter, and the operators. The AN/SQS-53B and AN/SQR-19 are shipboard sensors which provide detection, classification, and localization (position and movement of target) information for processing by the UFCS. NTDS allows another platform (ship or aircraft) to share information that it has on enemy submarine position and movement with a VLA ship by transmitting the information for use by the UFCS. LAMPS Mk III can relay similar submarine information from its deployed sonobuoys to its assigned VLA ship. Localization information, in conjunction with environmental data at the launch ship (surface winds, relative humidity, for example), is used by the UFCS to compute an aim point (intended water entry point) for the VLA.

VLA missile inspection, as well as component replacement, missile assembly, and checkout (test) are conducted at an Intermediate Maintenance Activity (IMA) where the VLA missile is placed into a canister for storage or transportation to the ship. The canister is loaded into the VLS aboard ship and the VLA is fired from the canister. No corrective maintenance of VLA will be performed aboard ship. Component repair will be conducted at the depot level.

The VLA program was initiated in the early 1980s to fulfill the need for a mid-range attack capability for surface ships with vertical launch systems. The VLA program was canceled in April 1988, in anticipation that another acquisition program, Sea Lance, would result in a longer-range ASW standoff weapon. In late 1988 Congress provided funding for a one-time buy of 300 VLAs until the surface ship-launched Sea Lance was fielded. This quantity was subsequently defined as 100 missiles for LRIP, with an additional 200 missiles for full production. VLA development continued, with OPEVAL occurring in August 1990. COMOPTEVFOR concluded that VLA was not operationally suitable and that low reliability precluded evaluation of operational effectiveness. FOT&E was conducted during June through August 1992 (missile assembly and encanisterization at the intermediate maintenance activity at the Naval Weapon Station, Yorktown, VA during June-July, and at-sea operational testing at an underwater test range of the Pacific Missile Range Facility, Barking Sands, HI during late August).

The ship-fired, ASROC-delivered Mark 45 nuclear torpedo was parachute deployed before entering the water and searching for and finding the submarine target. The torpedo, moving at 40 knots until reaching the proper depth in the water, then began a horizontal movement toward the target. Once in place, the warhead detonated. SWORDFISH was a low-yield nuclear weapon test (less than 20 kilotons) of an antisubmarine rocket (ASROC) delivery system conducted in the Pacific. The underwater test produced a spectacular eruption on the ocean surface. Operation Sailor Hat involved using numerous conventional explosives to simulate nuclear blasts. Delta, the last Sailor Hat test in the ship evaluation program, was conducted to study seismological data, underwater acoustics, radio communications, cratering, air blast effects, cloud growth, fire ball generation, and electromagnetic data.


Length: 192 inches
Diameter: 14.1 inches (body)
Weight: 1408 pounds
Power Plant: Solid Propellant Rocket
Warhead: MK 46 MOD 5 Torpedo
Guidance: Terminal Acoustic Homing with MK 46 Torpedo
Program: 438 missiles
Total program cost (TY$) $630.2M
Average unit cost (TY$) $0.84M
Full-rate production FY93

Prime Contractor
Loral Cleveland, OH


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Page last modified: 06-12-2017 17:40:39 ZULU