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damage or loss if they were to strike ice keels under the Arctic ice.2 Towed arrays also impose limitations on the speed and maneuverability of the towing ship, a factor that could be critical for submarines. U. S. single-hull submarines have severe space limitations for stowing the array, towing cables, and winch machinery. In U. S. submarines the array itself is housed in a long sheath that is fitted to the submarine deck, and related gear is fitted into ballast tanks. The Soviet combat submarines, which are all double-hulled, can accommodate gear in the between- hulls space.
Despite these limitations, the reduction in the noise level of the Soviet submarines and the vulnerability of U. S. seafloor-installed detection systems make towed arrays extremely important to the U. S. Navy.
In general, there are three categories of towed arrays in U. S. service:
- Tactical towed array sonar (TACTAS) in cruisers, destroyers, and frigates
- Surveillance towed array sonar system (SURTASS) fitted in tug-type surface ships and being evaluated for submarine use
- Submarine towed-array sonars, some previously referred to as submarine tactical array sonar system (STASS).
Development of operational towed arrays began in the 1960s, although the deployment of variable-depth sonars (VDSs) in U. S. ASW ships in that period probably delayed the towed array efforts.3 The VDS installations permitted the lowering of a sonar head beneath the surface and thermoclines, away from ship-generated noises. But in time towed arrays would provide much more capability. There was, of course, opposition to submarine towed arrays from some experts because of the limitations on mobility, plus some towed arrays were lost during operations.
Surface Combatant Ships: The first surface ship towed array was the SQR-14 towed array surveillance system (TASS) for ASW escorts. This set soon evolved into the SQR-15/16/17 series.
The SQR-15 remains in use on board the frigate Bronstein (FF-1037), some ships of the Garcia (FF-1040) class, and six ships of the Spruance (DD-963) class. The Spruance sets are cross-decked from one ship to another and will be discarded by about 1989 when the recently introduced SQR-19 becomes available for those ships. The SQR-15 towed array of the McCloy (FF-1038) was fouled by a Soviet Victor Ill-class attack submarine off the Carolina coast in November 1983.
Now being procured for surface ships
Sonar | Table 1 Surface Ship Towed Arrays Ships |
SQR-15 | Garcia class; six Spruance class |
SQR-17A | Few Knox (FF-1052)-class ships |
SQR-18A(V)1 | A'uo.r-class ships with VDS |
SQR-18A(V)2 | Knox class without VDS; Oliver Hazard Perry (FFG-7) class assigned to Naval Reserve Force |
SQR-19 | Ticonderoga (CG-47) class beginning with the Antietam (CG-54); Arleigh Burke (DDG-51) class; Spruance-class: Oliver Hazard Perry- class active force ships. |
are the improved SQR-18 and SQR-19 series. (See Table 1)
Few details of these systems are available. On these 35 ships of the Knox class fitted with VDS, the SQR-18A(V)1 tail is towed from the VDS housing. The non- VDS version of the array is 730-feet long and is towed with a 5,000-foot cable.
The SQR-19 array has a nominal diameter of 31/4 inches and is towed at the end of a 5,600-foot cable. The array section of the SQR-19 weighs about 10,000 pounds; the shipboard electronics weigh 12,900 pounds; and the array handling equipment weighs another 16,800 pounds. The SQR-19 installation is also being considered for the four Kidd (DDG-993)-class variants of the Spru- ance class. Only these towed arrays have a possibility of detecting modem submarines at long distances where the radius of the LAMPS-series SH-60B Seahawk helicopters and SH-2F helicopters can be employed.
Submarines: Most modem U. S. attack submarines (SSNs) as well as strategic missile submarines (SSBNs) have towed arrays. A set designated the STASS was apparently the first fitted in SSNs, followed by the towed-array component of the BQQ-5. The BQQ-5 is the large, multi-function sonar installation that was provided for the Los Angeles (SSN-688)- class submarines. Earlier submarines of the Sturgeon (SSN-637) and Permit (SSN-594) classes, and the Glenard P. Lipscomb (SSN-685), and Narwhal (SSN-671) were upgraded to the BQQ-5 configuration.
In the older, Lafayette (SSBN-616)- class strategic-missile submarines the BQR-15 has a towed array. In the newer Trident submarines of the Ohio (SSBN- 726) class, there is a towed-array component of the BQQ-6 sonar system. The BQQ-6 is essentially the BQQ-5 of SSNs, but without an active mode. An improved BQQ-9 thin-line towed array and signal-processing system is now being fitted to the Trident SSBNs.
There is little information available to the public on Soviet towed-array efforts. Some escort ships have been observed with array-type installations, probably under evaluation. Most notable has been the pod fitted atop the upper rudder of several Soviet SSN classes—the Victor III, Sierra, Akula, and modified Yankee. The pod probably houses a trailing-wire communications antenna or a thin-line towed array. The pod arrangement probably is used to move the tow away from the SSN propellers. Other means of keeping trailing wire antennas clear of screws
have been observed in other Soviet submarine classes. If indeed the Soviets have deployed a thin-line acoustic array in their SSNs, the implications for their ASW capability are considerable.
SURTASSIT-AGOS program: All of the above-described U. S. towed arrays are tactical. They provide detection and fire control data for on-board weapons. The surveillance towed array or SUR- TASS program is intended to provide very long range detection of submarines in regions where SOSUS is not deployed and where SOSUS has been destroyed. In areas where SOSUS is operating, the T-AGOS can be used to help triangulate contacts more accurately.
The Navy initially planned for 18 SURTASS ships, given the designation T-AGOS, which indicates a ship operated by the Military Sealift Command (T-) a miscellaneous auxiliary (AG), and ocean surveillance (OS). There are now 28 ships in the program, 19 of the Stalwart (T-AGOS-1) class and at least nine ships of a small waterplane area twin hull design (SWATH). The Stalwarts are 2,285- ton, 224-foot monohull ships similar to the Powhatan (T-ATF-166) oceangoing tugs. The SWATH ships, displacing 4,200 tons and 231-feet in length, are believed to be the largest SWATH ships ever attempted.
While no maximum number of T-AGOSs has been announced by the Navy, in 1985 the Chief of Naval Operations said 24 T-AGOSs were the minimum requirement. Ten of the Stalwart class have been completed and are being operated by MSC with civilian crews.
The UQQ-2 SURTASS towed array is a flexible, tube-like structure some 2,600-feet long containing numerous hydrophones towed by a 6,000-foot cable. The array is neutrally buoyant when at depth, with the depth being varied to compensate for environmental conditions. Typical array operating depths are 500 to 1,500 feet, with towing speeds of about three knots.
Data from the hydrophone array are generated at a very high rate. They are “pre-processed” on board the T-AGOS and sent at a much lower rate, reduced by a factor of ten, via satellite to shore stations. The data rate from ship to shore is about 32,000 bits (32 kilobits) per second.4 The data could be provided to warships in the area.
Civilian manned and unarmed, the vulnerability of the T-AGOS ships to hostile action during a conflict is a major concern of some naval officers.
SURTASS Submarines: This vulnera
bility factor and other consideration^
caused the Navy to install a UQQ'- . ; TASS array in one of the two Ethan a (SSN-608) transport submarines in to evaluate the potential for a su
tow.
This is an innovative approach
It could permit ope £
survivability issue.
; tO
the
ships
tion in areas that U. S. surface might wish to avoid for political re However, the SURTASS submarin cept does raise the problem of es ^ ing active links from the submarine ^oU,
relay satellite. Little has been
but there
are
elec-
this aspect of the concept, obvious technical solutions ( 0 ynljt tronic and possibly laser) that vv<j>^*teCtion- the probability of intercept or L ^ TASS Airship: There have ^,Sairship proposals to develop a ^^VpASSK towed array sonar system (M ^ jjeas When previously proposed, sUCajrs|iip
were ignored because no ^aV/nianne^ with ^
program existed. However, Wl1" : ll0w
"‘Navy an
ntial f°r
and unmanned surveillance a'r*a'^y and under development by the | fnr ^is
Coast Guard, there is potenti
TheP recent Soviet develop®®®*® fof
submarine quieting make it nece
ssary
aluate
* -
Western ASW forces to rf'evj^eCtion.
role of passive-versus-active sUb-
and the significance of non'ae°JJjovveVCr’ marine detection methods. passive detection cannot be a ^ 0j(j6r, because a large number sUbiua- “noisy” Soviet and Third Wor shoii^ rines still exist. Those submarine not receive a “free ride. |0nger
While the U. S. Navy can no^ de. rely exclusively on passive jj? tection as it has since World ^ gtjji ting ships with acoustic tails 1 important program.
Tom Stefanick, Strategic An,is^'’T'oT- HCi' ind Naval Strategy (Lexington,
nd Company, 1987). itqNR* i 1
Captain Leonard A. LeSchack, . Ed^ ^ :orArctic,” pp. 74-80. Major e . uCr
Ukeson, USA (Ret.) “Fighting $ Septcn ce,” U. S. Naval Institute Proceed S 987, pp. 81-85. , . hl. nep'h
The SQS-35(V) Independent Varta gKn°x Le IVDS) is now carried only on ' ' g) frigates- h £ 052)-class and the Glover (Fr- .f,<-troy^rS . afld umbers of modernized FRAM /np-692)* .^ '/etcher (DD-445), Allen M- 5“a"!.0dified Jearing (DD-710) classes, and n'
■herman (DD-931) destroyers w 5.
VDS. jT-AG°S’ i ii-
Norman Polmar, “SURTASS an j^go, pp- Java! Institute Proceedings, Mare ,
24- ,, , USN (Liaf
Captain Franklin D. Buckley- Array h . ■MATASS: Moored Airship Towed M lystem,” U. S. Naval Institute Proc 980, pp. 124-127.
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Proceedings
/ Octo'
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