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159
The Ships and Aircraft of the U. S. Fleet: Torpedoes
By Norman Polmar
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•yj, rnar‘ne rocket) launchers; the S-3 Mk ^ and Orion aircraft; and the d Captor (encapsulated torpedo) jtsne" ^de Mk-46 has fully replaced ^Predecessor, the Mk-44, in U. S. na 1Ce an<d *s also used by many allied t les> Including those of Britain and
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Mowever, the existing Mk-46 Mod
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Torpedoes remain principal antiship a^d antisubmarine weapons, despite e development of guided missiles atld other advanced weapon systems, otpedoes can be carried by a variety naval platforms, are relatively unsophisticated in their launching pro- ^ nres, and can be produced in vari- sizes and configurations. These ures make the torpedo a most use- ar*d versatile weapon.
The main U. S. torpedoes are the so called light torpedoes (500 lbs.) for tt-range attacks against submarines fo t^"e heavV torpedo (3,500 lbs.) sh' USe a^amst submarines and surface Ps at longer ranges. The current ■ S. light torpedo is the Mk-46, and e long-range “fish” is the Mk-48. k °wcver, the older, Mk-37 torpedo is e‘ng kept in service because of the t,8 C°St Ks planne<T replacement, 4^ ^'48, ancl the shortage of Mk-
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he Mk-37 is a submarine-launched As^° used primarily for close-in ■ Introduced just over two decades a801 the Mk-37 was originally just an th°Ust'c"h°ming torpedo. However, e Mod 2 has wire guidance which j rrn*ts control signals from the ^hing submarine to steer the tor- to counter enemy countermea-
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which the torpedo’s internal ^U' ance could not overcome. About l. ^ Mk-37 torpedoes remain avail- ^ for use in U. S. submarines.
^ e Mk-46 can be launched by ^any platforms: on almost all U. S. MkS^rS> desttoyers, and frigates from '32 torpedo tubes or ASROC (anti- 1 and 2 torpedoes have limited effectiveness against modern Soviet submarines. The Mk-46 torpedoes are now being modified by receiving improved acoustic guidance and countermeasure resistance features under the near-term improvement program (NEARTIP). This Mk-46 Mod 5 NEARTIP torpedo is scheduled to become operational during Fiscal Year (FY) 1979- Funds for giving 1,260 torpedoes NEARTIP conversions are included in the FY 1979-1980 budgets.
Even the NEARTIP version of the Mk-46 will have limited capabilities against future deep-diving, doublehull Soviet submarines. Thus, the Navy has initiated the advanced lightweight torpedo (ALWT) program to develop a new short-range torpedo, now designated as the Mk-XX.
The heavy submarine-launched Mk-48 torpedo has been the subject of intense controversy, principally because of its high cost—currently about $894,000 per weapon.* The Mk-48 was developed to replace the Mk-14 and Mk-16 torpedoes in the antiship role, and the Mk-37 and
•Based on FY 1979 "buy” of 127 torpedoes; the Navy request was for 319 weapons which would have produced a per weapon cost of $574,000. These costs include associated program expenses.
Designation | Launch Platforms | Operational | Weight Length | Diameter | Propulsion | Guidance | Notes |
Mk-37 Mod 2 | Submarines | 1957 | 1,690 lbs. 13.5 ft. (4.1 m) | 19 in. (484.5 mm) | electric | wire; active-passive acoustic | Range 5 miles |
Mk-37 Mod 3 | Submarines | 1957 | 1,430 lbs. 11.25 ft. (3.4 m) | 19 in. (484.5 mm) | electric | active-passive acoustic | Range 5 miles |
Mk-46 Mod 0 | Aircraft | 1966 | 568 lbs. 8.5 ft. (2.6 m) | 12.75 in. (324 mm) | solid-propel lant | active-passive acoustic |
|
Mk-46 Mod 1/2 | Surface ships (Mk-32 tubes and ASROC); aircraft | 1967-1972 | 508 lbs. 8.5 ft. (2.6 m) | 12.75 in. (324 mm) | liquid monopropellant | active-passive acoustic | Mod 4 in CAPTOR mine; Mod 5 is NEARTIP |
Mk-48 Mod 1/2 | Submarines | 1972 | 3,450 lbs. 19.1ft. (5.8 m) | 21 in. (533.6 mm) | liquid monopropellant | wire; active-passive acoustic | Range 20+ miles; deep diving |
Mk-XX | Surface ships (Mk-32 tubes and ASROC); aircraft | 1980s | 500 lbs. 8.5 ft. (2.6 m) | 12.75 in. (324 mm) |
| active-passive acoustic | ASW Advanced Light-Weight Torpedo (ALWT); Mk-46 replacement |
NT-37C Mod 2 | Submarines | Not USN | 1,708 lbs. 13.5 ft. (4.1m) | 19 in. (484.5 mm) | liquid-mono propellant | wire; acoustic | Anti-submarine; modified Mk-37 |
NT-37C Mod 3 | Submarines | Not USN | 1,448 lbs. 11.25 ft. (3.4 m) | 19 in. (484.5 mm) | liquid-mono propellant | acoustic | Anti-submarine; modified Mk-37 |
Mk-45-F Mod 0/1 | Submarines | Not USN | 2,555 lbs. 18.75 ft. (5.7 m) | 19 in. (484.5 mm) | electric | wire; acoustic | Anti-submarine; Freedom Torpedo; modified Mk-45 with conventional warhead; Mod 1 has wake-homing |
guidance; range 5-8 miles
Mk-45 ASTOR (antisubmarine torpedo) in the ASW role. In several respects the Mk-48 is probably the most capable torpedo in service with any navy. It possesses a number of advanced guidance features, including sophisticated passive-active acoustic search, as well as wire guidance. However, because of the Mk-48’s high cost, the Mk-37 has been retained for short-range use against submarines. (The Mk-37’s warhead is too small to be effective against surface ships.)
After a lengthy development period, the Mk-48 went into production in 1972. More than 1,400 Mk-48s had been delivered to the U. S. Navy through the beginning of 1978. Torpedoes now in production, along with the 127 being bought in FY 1979, will bring the total Mk-48 procurement to 2,771 through 1981. The Navy originally planned to buy over 4,000 of these torpedoes, but recent Department of Defense studies, which mainly dropped certain Soviet ships from the submarine target list, have led to reducing the Mk-48 procurement. Interestingly, these reductions occur as the numbers of large Soviet naval and merchant ships are increasing. Thus, with the Mk-37, almost 4,000 torpedoes will be available for some 90 attack submarines and approximately 40 strategic missile submarines in the 1980s.
Also, the Department of Defense has approved the sale of an initial increment of 12 Mk-48s to Australia, which has six modern diesel attack submarines. Several other nations have expressed interest in the Mk-48.
The availability of the Mk-48 has led to the phasing out of the Mk-45 ASTOR, the U. S. Navy’s only torpedo with a nuclear warhead. Some Mk-45 bodies have been mated with conventional warheads, while discarded Mk-37 torpedoes are being fitted with improved engines and guidance. These reworked torpedoes are being provided to foreign navies as the Mk-45-F (Freedom Torpedo) and the NT-37C, respectively.
Although not technically a torpedo, the SUBROC (submarine rocket) must be mentioned with torpedoes. This antisubmarine weapon is fired from standard 21-inch submarine torpedo tubes. It projects a nuclear depth charge to a distance of 25-30 nautical miles from the launching submarine. SUBROC’s limitations include the need to obtain release authority for use of a nuclear weapon, and the probable need for the launching submarine to use active sonar.
Whereas the conventional Mk-37 and Mk-48 torpedoes are carried in both attack and ballistic missile submarines, the nuclear-warhead SUBROC is found only in the Permit (SSN-594) and later classes of nuclear-powered attack submarines. With the phasing out of the Mk-45 ASTORs, the SUBROC has become the only nuclear ASW weapon available to U. S. undersea craft. The last SUBROC was delivered
in mid-1972, and the weapons that remain are becoming dated. If the existing SUBROCs are not soon updated or replaced by a new weapon, the U. S. submarine force may not have a nuclear-armed ASW weapon in the 1980s.
Submarine-launched, nuclear-armed ASW weapons—either torpedoes of SUBROC-type weapons—appear to have value in certain war-fighting scenarios, and hence in deterrence, especially against enemy strategic missile submarines. The Soviet submarine force is believed to have nuclear-armed torpedoes. The Soviet SS-N-15 AS'^/ missile is a SUBROC-type weapon with a nuclear warhead and a range estimated by some sources as about 25 nautical miles; the similar SS-N-16 is a weapon with a torpedo payload. (N° other navies are believed to have nuclear-armed torpedoes.)
The replacement of the nucleararmed Mk-45 ASTOR by the conventional Mk-48 probably marks the firs1 time in history that a nuclear weapon has been phased out in favor of an advanced conventional weapon. Thar move now takes on considerable significance for future U. S. antisubmarine capabilities as the “moment o* decision” nears for the SUBROC.
The future of nuclear-armed torpedoes and SUBROC in the U. S. Fleec is questionable. However, the torpedoes will remain an important aiU
surface, and submarine-launched
weapon for the foreseeable future.