18-inch Mk.7 (450 mm)

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18-inch Mk.7 deployed by the PT-3

Description

18-inch Mk.7 was an American lightweight torpedo developed by Bliss-Leavitt in 1911 as the first American torpedo used on submarines and surface vessels alike. By 1917 an airborne Mk.7 Type D variant was developed, but it has never seen serial production. Mk. 7 remained in service until the end of the World War 2, primarily on the O-type submarines.

Currently, the only vessel using the torpedo is the PT-3 torpedo boat. Due to the short range and relatively low speed, it's best used against barges rather than more mobile targets.

Vehicles equipped with this weapon

General info

Torpedo characteristics
Torpedo Mode Mass (kg) Maximum speed in water (km/h) Travel distance (km) Depth stroke (m) Arming distance (m) Explosive type Explosive mass (kg) TNT equivalent (kg)
No 720 59 3.65 1 50 TNT 93 93

Effective damage

With a 93 kg warhead the Mk. 7 can destroy any coastal vessel and a majority of a low-BR destroyers, larger vessels will require a hit directly on the magazines to achieve a kill, though ships equipped with a torpedo bulges might be completely immune to the weapon.

Comparison with analogues

The closest peer among US torpedoes is the Mk.8-3 C/D, a torpedo with nearly double the explosive mass, 15% slower speed (50 km/h instead of 59 km/h) and over triple the range, making it overall by far more versatile weapon.

The closest foreign equivalent would be the Japanese Type 44 No.2 which has a similar mass and same calibre, but a better speed, higher explosive mass and a slightly longer travel distance.

Name Country
of origin 		Diameter
(mm) 		Mass (kg) Explosive
type 		TNT equivalent
(kg) 		Max speed
(km/h) 		Max range
(km)
12.75 inch Mark 44 USA flag.png 324 235 HBX 54.4 56 5.49
12.75 inch Mark 46 USA flag.png 324 235 TNT 44.5 91 7.30
18 inch Mark XII Britain flag.png 450 702 TNT 176 74 1.37
18 inch Mark XV Britain flag.png 450 817 Torpex 395.2 61 3.20
18 inch Type 38 No.2 B Japan flag.png 450 663 Shimose 104.5 59 2.00
18-inch Mk.7 USA flag.png 450 720 TNT 93 59 3.65
21 in Mk.8 USA flag.png 533 1,252 TNT 146 50 9.14
21 inch Mark I Britain flag.png 533 1,270 TNT 102 56 11.00
21 inch Mk.20 Bidder Britain flag.png 533 821 TNT 89 37 11.00
21 inch Type 43 (1910) Japan flag.png 533 1,187 Shimose 143 50 8.00
45-36NU USSR flag.png 450 951 TNT 200 76 4.00
53-38 USSR flag.png 533 1,615 TNT 300 82 4.00
53-39 USSR flag.png 533 1,780 TNT 317 94 4.00
53-56 USSR flag.png 533 2,000 TNT 400 93 8.00
53-57 USSR flag.png 533 2,000 TNT 306 83 18.00
53-65 USSR flag.png 533 2,070 TNT 300 126 12.00
Bliss-Leavitt Mk.1 USA flag.png 533 680 TNT 91 50 3.66
C/06D Germany flag.png 450 810 TNT 122.6 50 5.90
G6c Germany flag.png 533 1,008 TNT 160 50 5.00
G7 Germany flag.png 500 1,365 TNT 249.6 69 4.00
G7a Germany flag.png 533 1,528 SW39a 358.4 81 6.00
H/8 Germany flag.png 600 2,160 SW39a 268.8 67 6.00
LT 1A/1 Germany flag.png 450 812 TNT 250 74 2.00
Mark 35 USA flag.png 533 803 Torpex 196 50 13.71
Mk.8-3 C/D USA flag.png 533 1,373 TNT 174.2 50 12.35
Mk.13 USA flag.png 569 884 TNT 178 56 5.21
Mk.15 USA flag.png 533 1,559 TNT 224 83 5.50
Mk.16 USA flag.png 533 1,766 Torpex 915.2 85 6.40
Mk.IV Britain flag.png 533 1,454 TNT 234 65 7.30
Mk.IX Britain flag.png 533 1,693 TNT 340 67 9.60
Mk.IX** Britain flag.png 533 1,693 Torpex 587.2 76 10.00
Mk.V Britain flag.png 533 1,736 TNT 305 74 4.57
Mk.VIII Britain flag.png 533 1,566 TNT 327 84 4.57
1909R France flag.png 450 716 TNT 144 61 2.00
Model 1919V France flag.png 550 1,358 Picric acid 261.8 80 2.00
Model 1923DT France flag.png 550 2,100 TNT 308 72 9.00
1926V France flag.png 400 674 TNT 144 81 2.00
L3 France flag.png 550 910 TNT 200 46 5.00
Pattern 1910 USSR flag.png 450 665 TNT 100 54 3.00
Pattern 1912 USSR flag.png 450 810 TNT 100 80 2.00
R.G.F. Mark VI** Britain flag.png 450 700 TNT 134 56 5.49
S.I.170/450X5,25 Italy flag.png 450 860 TNT 170 76 4.00
S.I.270 Italy flag.png 533 1,715 TNT 270 74 4.00
S.I. 250/533,4X7,5 Tipo A Italy flag.png 533 1,781 TNT 250 76 4.00
S.I. 270/533,4X7,2 Tipo I Italy flag.png 533 1,700 TNT 270 89 4.00
S.I. 270/533,4X7,2 Tipo M Italy flag.png 533 1,715 TNT 270 93 4.00
S.I. 270/533X6.84 Tipo L Italy flag.png 533 1,700 TNT 270 93 4.00
Seal DM2A1 Germany flag.png 533 1,370 TNT 250 61 20.00
SET-40 USSR flag.png 400 550 TNT 80 54 8.00
SET-53M USSR flag.png 533 1,480 TNT 100 54 14.00
SET-65 USSR flag.png 533 1,740 TNT 205 74 16.00
SET-72 USSR flag.png 400 730 TNT 80 74 8.00
Type 2 Japan flag.png 450 1,000 Type 97 448 72 3.00
Type 6 Japan flag.png 533 1,432 Shimose 223.3 65 7.00
Type 8 No.2 Japan flag.png 610 2,362 Shimose 380.6 70 10.00
Type 43 Japan flag.png 450 663 Shimose 104.5 48 5.00
Type 44 No.2 Japan flag.png 450 750 Shimose 121 65 4.00
Type 54 model 3 Japan flag.png 533 1,600 TNT 100 44 6.00
Type 72 mod.1 Japan flag.png 533 1,760 TNT 300 120 10.00
Type 89 Japan flag.png 533 1,660 Type 97 384 83 5.50
Type 90 Japan flag.png 610 2,540 Type 97 480 85 7.00
Type 93 Model 1, Mod 2 Japan flag.png 610 2,700 Type 97 627.2 91 20.00
Type 93 Model 3 Japan flag.png 610 2,800 Type 97 998.4 91 15.00
W.200/450X5,75 Italy flag.png 450 930 TNT 200 81 3.00
Whitehead A 110/450 Italy flag.png 450 936 TNT 110 56 4.00

Usage in battles

Much like all lightweight torpedoes, it's best used against large, slow targets with no torpedo defense. When using it, one must remember about the minimum arming distance, which is 50 m, or triple the full length of the PT-3. When faced with multiple fast coastal vessels and no alternative targets, it's worth to just launch torpedoes in a general direction of the enemy vessels - sometimes lucky hits are the best one can hope for.

Pros and cons

Pros:

  • Low mass

Cons:

  • Low maximum range
  • Relatively low speed
  • Small explosive filler

History

The Mk. 7 was the first American steam-driven torpedo that could be used by both submarines and surface vessels alike. Designed in 1911, it was also the first American wet heater torpedo.

The exact calibre of the torpedo was 17.7 inch, or 450 mm, though in the US it was typically rounded to "18 inch". It carried the Mk 7 Mod 5 warhead with 326 pounds of either TNT or TPX and a Mk 3 Mod 1 contact fuse. Torpedo had two modes, a low-pressure for 3,500 yards (3.2 km) travel distance and a high-pressure for 6,000 yards (5.5 km).

During the WW1 it has seen use primarily on the American K, L, M, N and O class submarines. With the retiring of the last of the O-class in 1946, the Mk. 7 ended its 34 years of career in the US Navy.

Media

Excellent additions to the article would be video guides, screenshots from the game, and photos.

See also

Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:

  • reference to the article about the variant of the cannon/machine gun;
  • references to approximate analogues by other nations and research trees.

External links


Torpedoes
USA 
450 mm  Mk.7
533 mm  Bliss-Leavitt Mk.1 · Mark 35 · Mk.8 · Mk.8-3 C/D · Mk.15 · Mk.16
569 mm  Mk.13 · Mk.13-6† · Mk.13-6 Case†
Germany 
324 mm  Mark 44
450 mm  C/06D · LT 1A/1 · F5W† · F5b†
500 mm  G7 · G6c
533 mm  G7a · Seal DM2A1
600 mm  H/8
USSR 
400 mm  SET-40 · SET-72
450 mm  Pattern 1910 · Pattern 1912 · 45-36NU‡ · 45-36AN† · 45-36MAN†
533 mm  53-38 · 53-39 · 53-56 · 53-57 · 53-65 · SET-53M · SET-65
Britain 
450 mm  R.G.F. Mark VI** · Mark XII‡ · Mark XV‡
533 mm  Mark I · Mk.IV · Mk.V · Mk.VIII · Mk.IX · Mk.IX** · 21 inch Mk.20 Bidder
Japan 
324 mm  Mark 46
450 mm  Type 2 · Type 38 No.2 B · Type 43 · Type 44 No.2 · Type 91 Model 2† · Type 91 Model 3†
533 mm  Type 6 · Type 43 (1910) · Type 54 Model 3 · Type 72 Model 1 · Type 89
610 mm  Type 8 No.2 · Type 90 · Type 93 Model 1, Mod 2 · Type 93 Model 3
Italy 
450 mm  F200/450† · S.I.170/450X5,25 · W.200/450X5,75 · Whitehead A 110/450
533 mm  S.I.270 · S.I. 250/533,4X7,5 Tipo A · S.I. 270/533,4X7,2 Tipo I · S.I. 270/533X6.84 Tipo L · S.I. 270/533,4X7,2 Tipo M
France 
400 mm  1926DA†
450 mm  1909R
550 mm  L3 · Model 1919V · Model 1923DT
Sweden 
450 mm  m/38† · m/41†
  † = Aerial torpedo
‡ = Aerial and ship-launched torpedo

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