Complete List of All U.S. Nuclear Weapons

Last changed 14 October 2006

If a weapon name is an active link, click on it to see a picture of the weapon, or a page on it (if one exists).

Mk-I

Bomb
28
120
8,900
15 – 16 Kt
Airburst
Used in combat in 1945, never stockpiled; only 5 bomb assemblies completed, all retired by Nov 1950
Gun-assembly HEU bomb; "Little Boy" dropped on Hiroshima

Mk-II
Bomb
Theoretical design, never produced
Low-efficiency plutonium implosion bomb

Mk-III

Bomb
60.25
128
10,300
18, 20-23, 37, 49 Kt
Airburst
Used in combat in 1945; mass production 4/47-4/49, 120 produced; all retired late 1950
Plutonium implosion bomb; "Fat Man", Model 1561; Mods 0, 1, 2

Mk-4

Bomb
60
128
10,800 – 10,900
1, 3.5, 8, 14, 21, 22, 31 Kt
Airburst
Entered service 3/49; produced 3/49-5/51; 550 produced (all mods);
Retired 7/52-5/53
Implosion fission bomb; redesigned weapon based on Mk-III Mod 1; first IFI weapon; first assembly-line produced nuclear weapon; used type C and D pits, composite Pu-HEU cores; 3 mods

T-1 / TX-1
Atomic Demolition Munition
About 8
?
About 150
Low kiloton
Time delay
Entered service, withdrawn, late 1940s
Developed at Picatinny Arsenal for the U.S. Army. The only U.S. nuclear weapon ever developed outside of the nuclear laboratory system. Gun-assembly HEU weapon.

W-4
Warhead
60
90
6,500
Airburst
Canceled 1951
Planned warhead for the Snark SSM cruise missile; Mk-4 bomb derivative

Mk-5

Bomb
43.75
129 – 132
3,025 – 3,175
6, 16, 55, 60, 100, 120 Kt
Airburst or contact
Entered operational stockpile 5/52;
last retired 1/63;
140 bombs (all mods) produced
92 lens high efficiency implosion bomb; used type D pit, composite cores; first weapon with major size/weight reduction over Fat Man; used as primary (1st stage) in the first thermonuclear devices; 4 mods; first weapon to use auto IFI

W-5
Warhead
39; 44
76
2,405 – 2,650; 2,600 (XW-5-X1)
same as Mk-5
Airburst or surface
Start of manufacture 4/54 (Regulus), 7/54 (Matador);
retired 7/61 – 1/63;
35 (Regulus), 65 (Matador) produced
Warhead for the Matador (MGM-1) and Regulus 1 (SSM-N-8) SSM cruise missiles; application to the Rascal air-to-surface canceled; first missile warhead; produced by modifying stockpile Mk-5 bombs

Mk-6

Bomb
61
128
7,600 – 8,500
8, 26, 80, 154, 160 Kt
Airburst or contact
Manufactured from 7/51 to early 1955; 1100 bombs (all mods) produced; last retired 1962
Improved high-yield lightweight Mk-4; 7 mods; some Mk-4Ds were converted Mk-6 Mod 0; early mods had 32 lens implosion system, Mod 2 and later had 60 lens system

Mk-7

Bomb
30.5
183
1,645 – 1,700
8, 19, 22, 30, 31, 61 Kt
Airburst or contact
Manufactured 7/52 – 2/63; in service July 1952-1967; 1700 – 1800 produced
Mk-7 "Thor"; multipurpose light weight tactical bomb; 92 lens implosion system; 6-7 yields; 10 mods, PAL A used on late mods

W-7
Warhead
30 – 30.5
54.8 – 56
900 – 1,100;
970 (W-7-X1 / X2);
983 (Betty)
90 T; 2 – 40 Kt
Airburst, surface, hydrostatic
W-7 warhead manufacture begun 12/53;
BOAR: stockpiled 1956 – 1963, 225 produced;
Corporal: stockpiled 1955 – 1965, 300 produced;
Honest John: stockpiled 1954 – 1960, 300 produced;
ADM: stockpiled 1955-1963, 300 produced;
Betty: stockpiled 6/55 – 1960, 225 produced;
Nike Hercules: canceled 1956
Multipurpose warhead – BOAR air-surface rocket, the Corporal (M-2) and Honest John (M-3) ballistic missiles, ADM, Betty Mk 90 ASW depth bomb, Nike Hercules SAM missile warhead (W-7-X1/X2); 7 yields, 4 mods; Corporal yield 2-40 Kt (several options), ADM yield low (90 T?), Betty yield 32 Kt

Mk-8

Bomb
14.5
116 – 132
3,230 – 3,280
25 – 30 Kt
Pyrotechnic delay
Manufactured 11/51 – 5/53; in service 1/52 – 6/57; 40 produced (all mods)
Earth penetrating weapon, gun-assembly HEU bomb, nicknamed "Elsie" (for LC – light case), 2 mods; replaced by the Mk-11

W-8
Warhead
Canceled May 1955
Gun-assembly warhead, intended for use as a cratering warhead for the Regulus missile

W-9
Artillery Shell
11.02 (280 mm)
54.8
803; 850
15 Kt
Mechanical time delay airburst
Manufactured 4/52 – 11/53;
Retired 5/57; 80 produced
Used in T-124, the first U.S. nuclear artillery shell; gun-assembly HEU weapon, modified TX-8; replaced 1-for-1 by W-19; only 20 280mm cannons were ever made

Mk-9 / T-4
Atomic Demolition Munition
120 – 200
Time delay
Stockpiled 1957;
retired 1963
The T-4 was built from recycled W-9 warheads; gun-assembly HEU weapon; replaced by W-45

Mk-10
Bomb
12
1,750; 1,500
12 – 15 Kt
Airburst
Canceled May 1952
"Airburst Elsie", a reduced size/ weight derivative of the Mk-8; superseded by the Mk-12

Mk-11

Bomb
14
147
3,210 – 3,500
Pyrotechnic delay
Manufactured 1/56 – 1957; in service 1/56 – 1960; 40 produced
Improved Mk-8 gun-assembly weapon, replaced Mk-8 on 1-for-1 basis; stockpiled as the "Mk-91 penetration bomb"

Mk-12

Bomb
22
155
1,100 – 1,200
12, 14 Kt
Timer or contact
Manufactured 12/54 – 2/57;
Retired 7/58 – 7/62; 250 produced
High-speed fighter-bomber weapon; 92-point implosion weapon; nicknamed "Brok"; probably first weapon using beryllium tamper; 4 versions stockpiled – 2 prototypes, 2 mods

W-12
Warhead
22
900
Low Kt
Airburst
Canceled Nov 1955
Talos (Navy)/Talos-W (Army) surface-air missile warhead

MK-13
Bomb
61
128
7,400
32 Kt (Upshot – Knothole Harry shot)
Airburst or contact
Canceled Aug 1954
High-yield Mk-6 follow-on, 92-point implosion system; superseded by TN Mk-15/39

W-13
Warhead
58
100
6,000 – 6,500
Airburst or contact
Canceled Sept 1954
Early warhead intended for Snark cruise missile, Redstone ICBM; superseded by TN Mk/W-15/39

TX / MK-14

Bomb
61.4
222 – 223.5
28,954 – 29,851; 31,000
5-7 Mt; 6.9 Mt (Castle Union shot)
Airburst
Stockpiled 2/54 – 10/54;
5 produced
First deployed solid-fuel thermonuclear weapon; recycled into Mk-17 weapons by 9/56; used 95% enriched Li-6; 64 ft parachute

MK-15

Bomb
34.4 – 34.7; 35
136 – 140
7,600
1.69 Mt (Castle Nectar), 3.8 Mt (Redwing Cherokee)
Airburst, contact (F/F or rtd), laydown
Manufactured 4/55 – 2/57;
Retired 8/61 – 4/65; 1200 produced (all mods)
First "lightweight" U.S. TN bomb; used HEU secondary casing; 3 mods; 1×3 ft and 1×12 ft ribbon parachutes

W-15
Warhead
34.5
6,400 – 6,560
Canceled Feb 1957
Class "C" TN missile warhead derived from MK-15, canceled in favor of very closely related W-39

TX-16

Bomb
61.4
296.7
39,000 – 42,000
6 – 8 Mt
Airburst
Stockpiled 1/54 – 4/54;
5 produced
First deployed thermonuclear weapon; weaponized version of Ivy Mike device; only cryogenic TN weapon ever deployed

EC-17
Bomb
61.4
224.9
39,600
11 Mt (Castle Romeo shot)
Airburst
Stockpiled 4/54 – 10/54; 5 produced
"Emergency Capability" weapon (deployed prototype); used natural lithium; free fall bomb

MK-17

Bomb
61.4
296.7
41,400 – 42,000
10 – 15 Mt
Airburst or contact (Mod 2 only)
Manufactured 7/54 – 11/55;
Retired 11/56 – 8/57; 200 produced
Similar to MK-24, different secondary; heaviest U.S. nuclear weapon, 2nd highest yield of any U.S. weapon (along with similar Mk-24); 3 mods; Mod 2 contact fused; 1×64 ft. parachute; replaced by the Mk-36

MK-18
Bomb
60
128
8,600
500 Kt (Ivy King shot)
Airburst or contact
Manufactured 3/53 – 2/55;
Retired 1/56 – 3/56; 90 produced (all mods)
Very high-yield MK-6/Mk-13 follow-on; largest pure fission bomb ever deployed; nicknamed the SOB ("Super Oralloy Bomb"); 92-point implosion system, all HEU core; 2 mods;
Retired by conversion to lower yield Mk-6 Mod 6; superseded by TN Mk-15 and Mk-28

W-19
Artillery Shell
11.02 (280 mm)
54
600
15 – 20 Kt
Mechanical time delay airburst
Production began 7/55;
Retired 1963; 80 produced
Used in T-315 atomic projectile; improved W-9; gun-assembly HEU weapon

Mk-20
Bomb
60
128
6,400
Canceled Aug 1954
Improved high-yield MK-13; superseded by TN MK-15

Mk-21
Bomb
56.2; 58.5
149 – 150
15,000 – 17,700
4 – 5 Mt
Airburst, contact, laydown
Manufactured 12/55 – 7/56;
Retired 6/57 – 1//57; 275 produced (all mods)
Redesigned Shrimp TN device with 95% enriched Li-6 fuel; 3 mods, all "dirty"; "clean" version tested, never deployed; Mod 1 contact fused; Mod 2 also had w/boosted primary;
Retired by conversion to Mk-36-Y1 Mod 1

W-21
Warhead
52;
145
15,000 – 16,000
Canceled
For B-58, SM-64A 56 Navaho

Mk-22
Bomb
51
18,000
1 Mt
Canceled April 1954
UCRL design based on the Morgenstern/Ramrod devices; canceled following Morgenstern fizzle (Castle Koon)

W-23
Artillery Shell
16
64
1,500; 1,900
15 – 20 Kt
Mechanical time delay airburst
Production began 10/56;
Retired 10/62;
50 produced
US Navy "Katie" shell; W-19 (11 inch shell) internal components adapted to 16 inch shell body

EC 24
Bomb
61
225
39,600
13.5 Mt (Castle Yankee shot)
Airburst
Stockpiled 4/54 – 10/54;
10 produced
"Emergency Capability" weapon (deployed prototype); used enriched Li-6; free fall bomb

Mk-24
Bomb
61.4
296
41,400 – 42,000
10 – 15 Mt
Airburst
Manufactured 7/54 – 11/55;
Retired 9/56 – 10/56;
105 produced
Similar to MK-17, different secondary; heaviest U.S. nuclear weapon, 2nd highest yield of any U.S. weapon (along with similar Mk-17); 2 mods (Mod 2 with contact burst canceled); 1×64 ft parachute; replaced by the Mk-36

W-25
Warhead
17.35 – 17.4
25.7 – 26.6
218 – 221
1.7 Kt
Time delay
Manufactured 5/57 – 5/60;
Mod 0 retired 8/61 – 1965, all retired by 12/84;
3150 produced (all mods)
MB-1 Genie AAM warhead; unboosted composite implosion warhead; first "sealed pit" weapon; 2 mods, Mod 1 had environmental sensing device safeties

Mk-26
Bomb
56.2
150
15,000 – 17,700
Canceled 1956
Mk-21 sibling design

Mk-27
Bomb
30.2
125 – 142
3,150 – 3,300
Airburst or contact
Manufactured 11/58 – 6/59;
Retired 11/62 – 7/65; 700 (all mods) produced
Navy TN bomb; This UCRL design was a competitor with the LASL Mk-28 to satisfy the Class "D" light weight TN bomb requirement; 3 mods

W-27
Warhead
30.25 – 31
75
2,800
2 Mt
Airburst or contact
Manufactured 9/58 – 6/59;
retired 8/62 – 7/65;
20 produced
Regulus I (SSM-N-8) SSM cruise missile warhead; considered for several other systems all of which were were canceled: the F-101 and B-58 bomb pods, and the Rascal, Regulus II, and Matador cruise missiles

Mk-28

Bomb
20; 22
96 – 170
1,700 – 2,320
Y1: 1.1 Mt,
Y2: 350 Kt,
Y3: 70 Kt,
Y5: 1.45 Mt
FUFO: F/F or retarded, airburst or contact, laydown
Manufactured 1/58 – 3/58, 8/58 – 5/66; retirement of early mods began 1961, last one retired 9/91; 4500 produced (all mods)
Multipurpose TN tactical and strategic bomb; longest weapon design in U.S. (33 years); 2nd largest production run of any U.S. weapon design; Y4 was fission only; 20 mods and variants; PAL A (Y1), B (Y2), D (Y3, Y5); replaced by B-61 and B-83 bombs; 1-point safety problem with primary discovered after start of initial manufacture, halting production for 5 months

W-28
Warhead
20
60
1,500 – 1,725
70 Kt – 1.45 Mt
Airburst or contact
Manufactured 8/58 – 5/66, entered service (Hound Dog) 1959 and (Mace) 1960;
Hound Dog retired 1/64 – 1976, Mace retired 1970;
production – 900 (Hound Dog), 100 (Mace)
Warhead for the Hound Dog (AGM-28) and Mace (MGM-13) cruise missiles; 5 mods; PAL A and B

W-29
Warhead
52; 35
145
3,500
Canceled Aug 1955
Canceled in favor of Mk-15

W-30
Warhead
22
48
438; 490; 450
300 T; 500 T (Talos and TADM); 4.7 Kt; 19 Kt
Airburst, contact, time delay
TADM: stockpiled 1961 – 1966, 300 produced;
Talos: manufactured 2/59 – 1/65, retired 1/62 – 3/79; 300 produced
Multipurpose warhead: Talos SAM/SSM, XW-30-X1 TADM (Tactical Atomic Demolition Munition) warhead; Talos – 1 yield, 3 mods; TADM – 2 yields stockpiled

W-31
Warhead
28 – 29; 30
39 – 39.3
900 – 945
1, 2, 12, 20, 40 Kt
Airburst, timer, surface
Honest John: manufactured 10/59 – 12/61, retired 7/67 – 1987, 1650 produced;
Nike Hercules: manufactured 10/58 – 12/61, retired 7/67 – 9/89, 2550 produced;
ADM: stockpiled 9/60 – 1965, 300 produced
Multipurpose boosted fission warhead: Honest John SSM, Nike Hercules SAM, ADM (Atomic Demolition Munition);
Versions used: Honest John: W-31 Mod 0, 3; Nike-Hercules: W-31 Mod 0, 2; ADM: Mk-31 Mod 1;
4 yields stockpiled: 2 for Nike-Hercules, 3 for Honest John (2, 20, and 40 Kt)

W-32
Artillery Shell
9.45 (240 mm)
400; 450
Canceled May 1955

W-33
Artillery Shell
8 (203 mm)
37
240 – 243
5 – 10 Kt, 40 Kt (Y2)
Mechanical time delay airburst
Manufactured 1/57 – 1/65;
Retired 9/92; 2000 produced
W-33 used in the T-317 atomic projectile; gun-assembly HEU weapon; used titanium to reduce weight and size; 4 yields (Y1 – Y4) using different internal HEU assemblies, high yield variant may be boosted; 2 mods

W-34
ASW warhead / Bomb
17
32
312; 320; 311
11 Kt
Hydrostatic, laydown, impact
ASW: Manufactured 8/58 – 12/62;
retired 7/64 – 1971 (Lulu), 7/64 – 1976 (Astor);
2000 Lulu, 600 Astor produced;
Hotpoint: Manufactured 6/58 – 9/62;
Retired by 1965;
600 produced
Multipurpose warhead for ASW (antisubmarine warfare) and tactical use; ASW: Mk-34 Lulu depth bomb, Mk-44 Astor torpedo; tactical: Mk-105 Hotpoint bomb, first parachute retarded laydown weapon; 2 mods; boosted fission implosion device identical to the Mk-28 primary

W-35
Warhead
20; 28
1,500 – 1,700
1.75 Mt
Canceled Aug 1958
Early LASL TN ballistic missile warhead, intended for Atlas, Titan ICBMs, Thor, Jupiter IRBMs; competitor with UCRL W-38; canceled in favor of W-49 (a modified Mk-28)

Mk-36

Bomb
56.2; 58; 59
150
17,500; 17,700
9 – 10 Mt
F/F or retarded airburst or contact
Manufactured 4/56 – 6/58;
Retired 8/61 – 1/62; 940 produced (all mods)
Two-stage TN strategic bomb; Y1 "dirty," Y2 "clean", each in two mods; parachutes 1×5 ft, 1×24 ft ribbon; all Mk-21s converted to Mk-36 in 1957;
Retired in favor of Mk-41; at retirement this weapon represented almost half of the megatonnage of the U.S. arsenal

W-37
Warhead
30
900; 940
Canceled Sept 1956
Intended to be a high-yield multipurpose companion to the W-31; XW-37 was redesignated XW-31Y2

W-38
Warhead
32
82.5
3,080
3.75 Mt
Airburst or contact
Manufactured 5/61 – 1/63; retired 1/65 – 5/65; Production: 110 (Atlas), 70 (Titan)
Warhead for Atlas E/F and Titan I ICBMs; used Avco Mk 4 RV; first UCRL designed TN ballistic missile warhead; competitor with LASL W-35/49

Mk-39

Bomb
35, 44 (tail section)
136 – 140
6,650 – 6,750
3-4 Mt (2 yields, Y1 and Y2)
Airburst, contact; mod w/low-level retarded laydown
Manufactured 2/57 – 3/59;
Retired 1/62 to 11/66; 700 produced (all mods)
Improved Mk-15, Mk-39 Mod 0 same as TX-15-X3; used gas-boosted primary to reduce weight; thermal batteries, improved safeties; 3 mods; parachutes: 1×6 ft, 1×28 ribbon, 1×100 ft

W-39
Warhead
34.5 – 35
105.7
6,230 – 6,400
3.8 Mt (2 yields, Y1 and Y2)
Redstone: stockpiled 7/58 – 1963, 60 produced;
Snark: manufactured 4/58 – 7/58, retired 8/62 – 9/65, 30 produced
Warhead for Snark cruise missile, Redstone MRBM, B-58 weapon pod;
Versions: Redstone Mk-39Y1 Mod 1 and Mk-39Y2 Mod 1, Snark Mk-39Y1 Mod 1; W-39 identical to Mk-39 except for fuzing system

W-40
Warhead
17.9
31.64
350; 385 (Y1)
10 Kt (Y1)
Airburst or contact
Bomarc: manufactured 9/59 – 5/62, retired by 11/72, 350 produced;
Lacrosse: manufactured 9/59 – 5/62, retired 10/63 – 1964, 400 produced
Warhead for Bomarc SAM and Lacrosse SSM; boosted implosion system adapted from Mk-28 primary; initially deployed version (produced 6/59-8/59) not 1-point safe, Mod 2 retrofit required; 2 yields

Mk-41
Bomb
52
148
10,500 – 10,670
25 Mt
FUFU: F/F or retarded, airburst or contact, laydown
Manufactured 9/60 – 6/62;
Retired 11/63 – 7/76; 500 produced
Highest yield U.S. weapon ever deployed; only U.S. 3-stage TN weapon; Y1 "dirty," Y2 "clean"; parachutes 1×4 ft, 1×16.5 ft;
retired in favor of Mk-53

W-41
Warhead
50
9,300
Canceled July 1957

W-42
Warhead
13 – 14
18.5
75 – 92
Proximity
Canceled June 1961
Intended for air-to-air (e.g. GAR-8), surface-to-air (e.g. Hawk) applications

Mk-43

Bomb
18
150 – 164
2,060 – 2,125
70 Kt – 1 Mt;
Y1: 1 Mt,
Y5: 500 Kt
F/F or retarded, airburst or contact, laydown
Manufactured 4/61 – 10/65;
retirement (early mods) began 12/72, last retired 4/91;
1000 produced (all mods)
Laydown bomb for high-speed low-altitude delivery; 5 yields; Y4 is fission only; PAL B (mod 2); Parachutes: 1×4 ft, 1×23 ft ribbon; last version retired was MK-43Y2 Mod 2

W-44
ASW warhead
13.75
25.3
170
10 Kt
Hydrostatic
Manufactured 5/61 – 3/68;
retired 6/74 – 9/89;
575 produced
ASROC (RUR-5A) ASW warhead; plutonium implosion warhead, similar to primary for Mk-43

W-45
Warhead
11.5
27
150;
MADM: 350
500 T; 1, 5, 8, 10, 15 Kt
Airburst, surface, time delay, command
Terrier: manufactured 4/62 – 6/66, retired 7/67 – 9/88, 750 produced;
MADM: manufactured 1/62 – 6/66, retired 7/67 – 1984, 350 produced;
Bullpup: manufactured 1/62 – 1963, retired 7/67 – 1978, 100 produced;
Little John: manufactured 9/61 – 6/66, retired 7/67 – 1970, 500 produced
Multipurpose UCRL designed tactical warhead; small implosion design; Y1 (1 Kt): Little John SSM, Terrier SAM,MADM (Medium ADM); Y2: Little John, MADM; Y3 (unboosted): GAM-83B Bullpup ASM, MADM; Y4 (boosted, 1 Kt): Bullpup, Little John, Terrier, MADM

Mk-46
Bomb
37
6,400
Mt range
Canceled Oct 1958
"Clean" and "dirty" versions tested during Hardtack I; was to have replaced Mk-39; development of improved design continued as Mk-53

W-46
Warhead
35-40
Canceled April 1958
Warhead planned for Redstone, Snark, B-58 pod warhead; Redstone/W-46 canceled in favor of Titan II/W-53

W-47
Warhead
18
46.6
Y1: 717 – 720;
Y2: 733
Y1: 600 Kt;
Y2: 1.2 Mt
Airburst or contact
EC-47 manufactured 4/60 – 6/60, retired 6/60, 300 produced;
W-47 manufactured 6/60 – 7/64, retired 7/61 – 11/74, 1060 produced (Y1 and Y2) – only 300 in service at a time
Polaris SLBM TN warhead; breakthrough in compact, light high yield design; integral warhead/beryllium re-entry vehicle; 3 versions: EC-47, W-47Y1, W-47Y2; several severe reliability problems required repeated modification and remanufacture (in 1966 75% of the stockpiled Y2s were inoperable, correction took until 10/67)

W-48
Artillery Shell
6.1 (155 mm)
33.3
118 – 128
72 T
Mechanical time delay or proximity airburst, or contact
Manufactured 10/63 – 3/68; retirement (135 Mod 0s) 1/65 – 1969, all 925 Mod 1s retired 1992; 1060 produced (all mods)
Small diameter linear implosion plutonium weapon, 2 mods

W-49
Warhead
20
54.3 – 57.9
1,640 – 1,680
1.44 Mt
Airburst or contact
Manufactured 9/58 – 1964;
Thor retired 11/62 – 8/63 (a few to 4/75);
LASL developed ICBM/IRBM warhead; Used in Thor (Mod 0,1, 3), Atlas (Mod 0, 1), Titan, Jupiter (Mod 0, 1, 3, 5) warhead; 2 RVs used Mk-2 heat sink and Mk-3 ablative; 2 yields, 7 mods; Mk/W-28 adaptation with new arming/fuzing system; PAL A; successor to W-35

W-50
Warhead
15.4
44
409 – 410
Y1: 60 Kt;
Y2: 200 Kt;
Y3: 400 Kt
Airburst or contact
Manufactured 3/63 – 12/65;
retired 4/73 – 4/91;
280 produced
TN warhead for Pershing SSM (Mod 1, 2), Nike Zeus SAM (canceled 5/59); Mod 1 equipped with PAL A; 3 yields, 2 mods

W-51
Warhead
22 T
Became XW-54 Jan 1959
Very small spherical implosion warhead, initial development by LRL, development transferred to LASL and design redesignated W-54

W-52
Warhead
24
56.7
950
200 Kt
Airburst or contact
Manufactured 5/62 – 4/66;
retired 3/74 – 8/78;
300 produced
Sergeant SSM warhead; 2 yields, 3 mods; PAL A (Mod 2); warhead test in 1963 showed Mods 1 and 2 to be useless, Mod 3 was first to achieve rated yield

Mk-53

Bomb
50
148 – 150;
Y2 144
8,850 – 8,900
9 Mt
FUFO: F/F or retarded, airburst or contact, laydown
Manufactured 8/62 – 6/65; retirement (early mods) began 7/67, last 50 retired from active service (but retained in permanent stockpile) early 1997; 350 produced, 50 still in stockpile
Carried by B-47, B-52; B-58 used Mk-53BA (in BLU-2/B pod); 4 mods, Y1 "dirty" version, Y2 "clean" version; fissile material all HEU, no plutonium; parachutes: 1×4 ft, 1×16.5 ft ribbon, 3×48 ft ribbon; last 50 retired in favor of B-61 Mod 11; part of the U.S. "enduring stockpile"

W-53
Warhead
37
103
6,200
9 Mt
Airburst or contact
Titan II warhead

W-54
Warhead
10.75
15.7
50 – 51
250 T
Contact or proximity
Manufactured 4/61 – 2/65; retired 7/67 – 4/72; 1000 – 2000 produced
GAR-11/AIM-26A Falcon AAM warhead; originally called "Wee Gnat"; adaptation of Mk-54

Mk-54
Warhead
10.75
17.6
50 – 55
10, 20 T
Time delay
Manufactured 4/61 – 2/65;
retired 7/67 – 1971;
400 produced
Warhead for Davy Crockett M-388 recoilless rifle projectile; 2 yields; 2 mods; very light, compact spherical implosion plutonium warhead

Mk-54 SADM
Atomic Demolition Munition (ADM)
16
24
150 (complete);
59 (W-54 only)
Variable, 10 T – 1 Kt
Time delay
Manufactured 8/64 – 6/66;
retired 1967 – 1989;
300 produced
SADM:
M-129/M-159 SADM (Special Atomic Demolition Munition) used a Mk-54 warhead package very similar to Davy Crockett; 2 mods; mechanical combination lock PAL

W-55
ASW
13
39.4
470
Mid Kiloton Range
Hydrostatic
Manufactured 1/64 – 3/68, 3/70 – 4/74;
retired 6/83 – 9/90;
285 produced
SUBROC (UUM-44A) ASW missile thermonuclear warhead; based on the 202 Kt Hardtack I Olive device

W-56
Warhead
17.4
47.3
600; 680
1.2 Mt
Airburst or surface
Manufactured 3/63 – 5/69;
retired 9/66 (early mods), Mod-4 retired 1991-93;
1000 produced (all mods), 455 Mod-4s produced
Minuteman I and II warhead, based on UCRL W-47, competitor with the W-59 for Minuteman; 4 mods, retrofit of early mods required to fix reliability problem, blast and radiation hardening added later

Mk-57
Bomb
14.75
118
490 – 510
5 – 20 Kt
Retarded airburst, retarded laydown, F/F contact, hydrostatic
Manufactured 1/63 – 5/67; retirement (early mods) started 6/75, last retired 6/93; 3,100 produced
Light weight multipurpose tactical strike/depth bomb; boosted implosion fission weapon; modular design, 6 mods; PAL B; 1×12.5 ft ribbon parachute;
Retired in favor of B-61

W-58
Warhead
15.6
40.3
257
200 Kt
Airburst or contact
Manufactured 3/64 – 6/67; retired 9/68-4/82; 1400 produced
Polaris A-3 warhead, each A-3 carried three multiple re-entry vehicles (MRVs), first MRV warhead in service

W-59
Warhead
16.3
47.8
550 – 553
1 Mt
Airburst or contact
Manufactured 6/62 – 7/63;
retired 12/64 – 6/69;
150 produced
Warhead for Minuteman I/Mk 5 RV and the canceled Skybolt; version of LASL "J-21" design;

W-60
Warhead
13
20
115 – 150
Very low
Proximity
Canceled Dec 1963
Typhon SAM warhead

MK/B 61

 

Bomb
13.3
141.64
695 – 716
Variable (4 yields), 0.3 – 340 Kt;
Mod 3: 0.3 – 170 Kt;
Mod 4: 0.3 – 45 Kt;
Mod 7/11: 10 – 340 Kt;
Mod 10: 0.3 – 80 Kt
FUFO: retarded and F/F, contact or airburst, laydown
Manufactured 10/66 – early 90s; early mods retired 70s – 80s; 3150 produced, 1350 in service
Multipurpose tactical/strategic bomb; basic design adapted to many other weapon systems; 4 yields; 11 mods, 5 in service; PAL B, D, F; uses IHE in primary; parachute: 1×17 ft or 1×24 ft ribbon; longest production run of any U.S. nuclear weapon, oldest design in service; part of the U.S. "enduring stockpile"

W-62
Warhead
RV Body: 21 in;
Warhead: 19.7 in
RV Body: 72 in;
Warhead: 39.3 in
Warhead/RV: 700-800 lb;
Warhead: 253 lb
170 Kt
Airburst or contact
Manufactured 3/70 – 6/76;
early mods retired starting 4/80;
1725 produced, 610 in active service;
Minuteman III/Mk-12 RV warhead; remaining W-62s part of U.S. "enduring stockpile", but will be removed from active service under START II (to be replaced by W-88s)

W-63
Warhead
Canceled Nov 1966
LRL design for Lance SSM warhead; ER ("neutron bomb") design; (canceled in favor of W-70

W-64
Warhead
Canceled Sep 1964
LASL design for Lance SSM warhead; ER ("neutron bomb") design; canceled in favor of W-63

W-65
Warhead
Mt range
Canceled Jan 1968
Sprint ABM warhead, canceled in favor of W-66

W-66
Warhead
18
35
150
Kt range
Manufactured 6/74 – 3/75;
retired from service 8/75, ret. from stockpile 1985;
70 produced
Sprint ABM warhead, ER ("neutron bomb") warhead

W-67
Warhead
150 Kt
Canceled Dec 1967
LRL ICBM/SLBM multiple warhead, intended for Poseidon and Minuteman-III

W-68
Warhead
367
40 – 50 Kt
Airburst or contact
Manufactured 6/70 – 6/75; retired 9/77 – 1991; 5250 produced
Poseidon Mk-3 RV warhead, each missile carried 10 RVs; aging problems with explosive required complete rebuilding of stockpile 11/78-83 (3200 rebuilt, others retired); largest production run of any U.S. warhead

W-69
Warhead
15
30
275
170 – 200 Kt
Airburst or contact
Manufactured 10/71 – 8/76;
retired 10/91 – 9/94;
1500 produced
SRAM (short range attack missile, AGM 69A) air-surface missile warhead; derived from Mk-61; initially removed from active service 6/90 due to fire safety concerns

W-70
Warhead
18
41
270
Mods 0,1, 2: variable from 1-100 Kt;
Mod 3: 1 Kt
Airburst or contact
Manufactured 6/73 – 7/77 (Mods 0-2), 8/81 – 2/83 (Mod 3);
retired 7/79 – 9/92;
Mods 0-2: 900 produced, Mod 3: 380 built
Lance SSM warhead; LRL successor to W-63 design; 4 mods; Mods 0, 1, 2: TN warhead with 3 yield settings (1-100 Kt), Mod 1 had improved selection of yields; Mod 3: enhanced radiation ("neutron bomb") version, 2 yield options (slightly less than 1 Kt, and slightly more than 1 Kt), both 60% fusion and 40% fission; PAL D

W-71
Warhead
42
101
2,850
5 Mt
Airburst (command & delay timer)
Manufactured 7/74 – 7/75;
retired from service 1975, ret. from stockpile 9/92;
30 produced
Spartan ABM warhead, used thermal x-rays for exoatmospheric RV kill

W-72
Warhead
15
79
825
ca. 600 T
Contact
Manufactured 8/70 – 4/72;
retired 7/79 – 9/79;
300 produced
Walleye (AGM-62) guided glide bomb warhead; W-72 was a modified W-54, salvaged from retired AIM-26A Falcon AAM; yield was significantly enhanced over Falcon version

W-73
Warhead
<17
Canceled Sept 1970
Condor ASM warhead; derived from Mk-61; canceled in favor of a conventional HE warhead

W-74
Artillery Shell
6.1 (155 mm)
2 yields (both >100 T)
Canceled June 1973
Linear implosion pure fission plutonium warhead; intended to replace W-48

W-75
Artillery Shell
8 (203 mm)
>100 T
Canceled 1973
"Big brother" of W-74, similar design

W-76
Warhead
363
100 Kt
Airburst or contact
Manufactured 6/78 – 7/87;
active service;
approx. 3000 produced
Trident I and Trident II Mk-4 RV TN warhead, missiles can carry 8-14 RVs; developed by LANL; part of the U.S. "enduring stockpile"

B-77
Bomb
18
144
2,400
Variable, Kt to Mt range
FUFO
Canceled Dec 1977
High yield strategic TN bomb, intended to replace Mk-28 and Mk-43; PAL D; costly, heavy delivery system lead to cancellation, warhead design continued with B-83

W-78
Warhead
21.25
67.7
400 – 600
335 – 350 Kt
Airburst or contact
Manufactured 8/79 – 10/82;
active service;
1083 produced, 920 in service
Minuteman III/Mk-12A RV warhead; LANL design derived from W-50 with a new lighter primary; part of U.S. "enduring stockpile", but will be removed from active service under START II (to be replaced by W-88s)

W-79
Artillery Shell
8
44
200
Variable – 100 T to 1.1 Kt (Mod 0), 0.8 Kt (Mod 1)
Proximity airburst or contact
Manufactured 7/81 – 8/86; ER version retirement started mid-80s, all retired 9/92; 550 (325 ER, 225 fission) produced
Plutonium linear implosion weapon, used in XM-753 atomic projectile (AFAP); Mod 0: dual capable – pure fission or enhanced radiation (ER of "neutron bomb"), 3 yield options; Mod 1: fission only; PAL D

 

W-80-0
Warhead
11.8
31.4
290
Variable: 5 Kt and 170-200 Kt
Airburst or contact
Manufactured 12/83 – 9/90;
active service;
367 produced
SLCM warhead; uses supergrade plutonium; PAL D; LANL design derived from Mk/B-61 warhead; now stored ashore; part of the U.S. "enduring stockpile"

W-80-1
Warhead
11.8
31.4
290
Variable: 5 Kt and 150-170 Kt
Airburst or contact
Manufactured 1/81 – 9/90;
active service;
1750 produced, 1400 in service
Warhead for ALCM (1000 in service), ACM (400 in service); PAL D; LANL design derived from Mk/B-61 warhead; part of the U.S. "enduring stockpile"

W-81
Warhead
<13.5
2 – 4 Kt
Canceled 1986
USN Standard SM-2 SAM warhead; PAL F; variant of Mk/B-61 warhead, enhanced radiation version initially planned, later converted to fission only

W-82
Artillery Shell
6.1 (155 mm)
34
95
<2 Kt
Airburst
W-82-0 canceled in Oct 1983; W-82-1 canceled in Sept 1990
155 mm companion to the the W-79, for use in XM-785 atomic projectile (AFAP); original Mod 0: dual capable – pure fission or enhanced radiation; Mod 1: fission only; PAL D

B-83

Bomb
18
145
2,400
Variable, low Kt to 1.2 Mt
FUFO: F/F or retarded, airburst or contact, laydown
Manufactured 6/83 – 1991;
active service;
650 produced
Current high-yield strategic TN bomb; PAL D; uses IHE, fire resisitant pit; parachutes: 3×4 ft, 1×46 ft; 1×5 ft, 1×46 ft

W-83
Warhead
1,700 – 1,900
PAL D

W-84
Warhead
13
34
388
Variable: 0.2 – 150 Kt
Airburst or contact
Manufactured 9/83 – 1/88;
inactive stockpile;
300-350 produced
GLCM warhead, missile scrapped under INF Treaty; LLNL design derived from LANL Mk/B-61 Mod 3/4 warhead; uses IHE, PAL F; part of the U.S. "enduring stockpile"

W-85;
alternate image
Warhead
12.5
42
880
Variable: 5 – 80 Kt
Airburst or contact
Manufactured 2/83 – 7/86;
retired 1988 – 3/91;
120 produced
Pershing II SSM warhead; derived from LANL Mk/B-61 Mod 3/4 warhead; uses IHE, PAL F; upon retirement the W-85 was recycled into B-61 Mod 10 bombs

W-86
Warhead
Delayed
Canceled Sept 1980
Earth penetrating warhead for the Pershing II SSM, canceled due to change in mission from hard to soft targets

W-87

Warhead
21.8
68.9
500 – 600; 440
300 Kt;
upgradeable to 475 Kt
Timer or proximity airburst, contact
Manufactured 7/86 – 12/88;
active service;
525 produced
Peacekeeper (MX) ICBM/Mk-21 RV TN warhead (missile carries 10); RV/warhead weighs 800 lb; LLNL design; primary uses IHE and fire resistant pit; yield upgradeable by adding HEU rings to secondary; part of the U.S. "enduring stockpile"; after MX retirement, will equip Minuteman III

W-88
Warhead
21.8
68.9
<800
475 Kt
Timer (w/path length correction) and proximity airburst; contact
Manufactured 9/88 – 11/89; active service;
400 produced
Trident II Mk-5 RV warhead; does not use IHE; uses HEU jacket with secondary stage; production terminated by FBI raid on Rocky Flats; part of the U.S. "enduring stockpile"

W-89
Warhead
13.3
40.8
324
200 Kt
Airburst or contact
Canceled Sept 1991
SRAM (short range attack missile) II warhead; LLNL design; safety features: PAL D, IHE, FRP; also considered for Sea Lance ASW missile

B 90
Bomb
13.3
118
780
200 Kt
retarded airburst, retarded contact, F/F airburst, F/F contact, hydrostatic
Canceled 1991
USN nuclear strike/depth bomb; intended to replace Mk-57; PAL D; 1×26 ft parachute

W-91
Warhead
310
10, 100 Kt
Canceled Sept 1991
SRAM-T (short range attack missile – tactical) warhead; SRAM-T was a SRAM II derivative for the F-15E Eagle fighter/bomber; LASL TN design orignally called "New Mexico 1"; safety features: FRP, IHE; 2 yields

---

Abbreviations:

• AAM Air-to-Air Missile
• ABM Anti-Ballistic Missile
• ACM Advanced Cruise Missile
• ADM Atomic Demolition Munition
• AFAP Artillery Fired Atomic Projectile
• ALCM Air Launched Cruise Missile
• ASM Air-Surface Missile
• ASW Anti-Submarine Warfare
• ER Enhanced Radiation ("neutron bomb")
• EC Emergency Capability
• F/F Freefall
• FRP Fire Resistant Pit
• FUFO Full-fuzing Options
• HEU Highly Enriched Uranium
• ICBM Intercontinental Ballistic Missile
• IFI In-Flight Insertion
• IHE Insensitive High Explosive
• IRBM Intermediate-Range Ballistic Missile
• Kt Kilotons
• LANL Los Alamos National Laboratory (nee LASL)
• LASL Los Alamos Scientific Laboratory
• LLNL Lawrence Livermore National Laboratory (nee LRL)
• LRL Lawrence Radiation Laboratory (nee UCRL)
• MK Mark
• MRBM Medium-Range Ballistic Missile
• Mt megatons
• PAL Permissive Action Link
• Pu Plutonium
• RV Re-entry Vehicle
• SAM Surface-to-Air Missile
• Rtd Parachute-retarded
• SLBM Sea-Launched Cruise Missile
• SSM Surface-to-Surface Missile
• T tons
• TN Thermonuclear
• UCRL University of California Radiation Laboratory
• USN US Navy

---

Principal Sources:
Swords of Armageddon by Chuck Hansen, 1995
U.S. Nuclear Weapons: The Secret History by Chuck Hansen, 1988
Nuclear Weapons Databook: U.S. Nuclear Forces and Capabilities by Thomas B. Cochran, William M. Arkin, and Milton M. Hoenig, 1984
NRDC Nuclear Notebook prepared by Robert S. Norris and William Arkin of the Natural Resources Defense Council, published in The Bulletin of the Atomic Scientists.
Especially in issues:

• July/August 1996
• July/August 1995

Nuclear Weapons of the United States by James N. Gibson, 1996.

 

U.S. Nuclear Weapon Enduring Stockpile

Last changed 31 August 2007

The U.S. nuclear arsenal is divided into three levels of stockpile readiness. These are:

• Operationally Deployed: These are active stockpile (fully operational) weapons and mated with delivery systems such that they are ready to be used in combat. All warheads counted under arms limitation agreements belong to this category.
• Active Stockpile: Fully operational weapons, available for immediate use, whether or not they are operationally deployed. Reasons for an active stockpile weapon to not be operationally deployed include:
  • Its assigned to a delivery system is not currently operational (in particular ballistic missile submarines spend one-third of their time not on patrol),
  • It is a spare for deployed warheads (should a deployed warhead require maintenance, for example), and
  • It is part of the responsive force — an inventory of warheads that are kept in operational condition (tritium reservoirs installed, etc.) to permit immediate deployment (for example to upload the number of wartheads on a ballistic missile, or reloads for bomber aircraft).
• Inactive Reserve: Weapons that are kept intact, but are not maintained in operational condition. This means that limited life components are removed from the weapons and may not be available to immediately return them to service. "Limited life components" principally mean tritium-containing components such as tritium reservoirs and neutron generator tubes. Some weapons currently in this category (e.g. the W84) will be dismantled.

At the beginning of 2007 the U.S. nuclear arsenal was composed of eight types of nuclear warheads (in thirteen variant mods) that are operationally deployed, with an estiamted count of 5,736 active stockpile warheads. For the first time the 2007 Annual Report on Implementation of the Moscow Treaty listed the aggregate number of U.S. operationally deployed strategic nuclear warheads which as of 31 December 2006 stood at 3,696. No official breakdown of this number is available, however if one assumes that ICBMs have 95% availability, 66% of SLBMs are on patrol, and 90% of bombers are on-duty with their full combat load, then this tally exactly matches the offical operational count.

One of the active warheads (the W87) is currently being redeployed (replacing the W62) after having been taken off of operational duty in the 1990s.

There are also 589 warheads of two types that are inactive, these are not kept in operational condition and one of these warheads (the W84) is slated to be completely dismantled.

The total number of warheads of all levels of readiness stands at 9,962 warheads. It should be pointed out that although precise numbers are cited here to keep tallies consistent and avoid cumulative rounding errors, they are in fact approximations. Even if exact numbers were available for one specific moment in time, continuing stockpile changes as a result of deployment shifts and inspection and maintenance actions causes actual numbers to fluctuate.

The total megatonnage of the deployed nuclear arsenal is about 1,430 Mt (but this is influenced by the choice of deployed weapons for bombers); for the entire active arsenal it is 2,330 Mt. The all-time high point in explosive yield was in 1960 when the U.S. held 20,491 Mt in its stockpile. The size of nuclear arsenals are often evaluated using "equivalent megatonnage" a scaling procedure that compensates for the fact that smaller explosions cause relatively more blast destructive for the amount of explosive energy released. An EMt value of one indicates the destructive effect of one 1 megaton bomb. Since most warheads in the U.S. arsenal are much less than one megaton this measure results in a larger value than the raw megatonnage. Using this measure the destructiveness of the deployed arsenal becomes 2,090 EMt, and the total active arsenal 3,405 EMt.

The United States has produced about 70,000 nuclear weapons of 72 major types since their invention. At the end of the Cold War in 1991 the United States had an active arsenal of some 23,000 weapons of 26 major types. Since that time actual nuclear warhead production has been completely shut down in the U.S., although warhead modification, retrofit, and maintenance activities continue. Much of the original nuclear weapons manufacturing infrastructure has been dismantled, and the focus of the remaining nuclear infrastructure has shifted to maintaining and extending the life of the remaining weapons, as well as dismantling surplus weapons.

The only strategic arms treaties still in force between the U.S. and the Russian Federation is the Moscow Treaty on Strategic Offensive Reductions (also called "the Moscow Treaty," the Strategic Offensive Reductions Treaty, or SORT) and the START I treaty, which will expire in December 2009. The Moscow Treaty was signed by Presidents George W. Bush and Vladimir Putin on 24 May 2002 and ratified by the U.S. Senate on 6 March 2003, and by the Russian Duma on 14 May 2003. The Moscow Treaty sets lower warhead limits than the effective limits of START I and requires both sides to reduce their deployed strategic nuclear warheads to between 1,700 and 2,200 warheads by midnight 31 December 2012. Strangely, the deadline for compliance is the same moment as the expiration of the treaty so it is questionable whether the warhead limit ever legally takes effect.

 

The Moscow Treaty does not require the destruction of any of the warheads taken out of deployment. Given the lengthy period the Moscow Treaty gives for reductions (more than a decade) and the debatable effect of its limit, the actual effect it will have on U.S. and Russian arsenals remains to be seen. U.S plans appear to take into account reduction to the SORT upper limit of 2,200 however.

Current plans are to completely retire and dismantle the oldest warhead in the U.S. arsenal, the W62 carried by the Minuteman III missile. Retirement of the W62 began in October 2006, and is being replaced by W87 warheads that have been in storage since they were removed from Peacekeeper (MX) missile upon its retirement. Five other deployed warheads (the B61-3, B61-4, W76, W78 and W80-1) will be reduced in number to bring the count down to 2,200. This will required removing 3,759 of these five warheads from deployment (given that 553 W87s are being returned to duty); together they number 4,302 of the currently deployed force. Partial dismantlement of these warheads is expected, but former Secretary of Defense Donald Rumsfeld has indicated that most the warheads removed from deployment will be kept in the U.S. stockpile.

Actual production of new warheads halted in 1989. In January 1997, the first new weapon modification since the production shutdown entered service – the B61 Mod 11 (B61-11) ground penetrating ("bunker busting") bomb. This was a modification of B61 Mod 7s that were already in the stockpile. Remanufacture and updating of subsystems of existing weapons is on-going as part of a stockpile Life-Extension Program (LEP).

In the FY2005 budget congress authorized $36.6 million for two new nuclear weapons programs – the Robust Nuclear Earth Penetrator (RNEP), and the Advanced Concepts Initiative (ACI). The RNEP was intended to explore the design of a new "bunker busting" warhead, while the ACI explored other weapons concepts. Poor reviews of the RNEP concept led to the deletion of funding from the FY2006 budget. The ACI on the other hand was replaced by the Reliable Replacement Warhead (RRW) program, to which its funds were transferred. The National Nuclear Security Administration (NNSA) requested funding of $9.351 million for RRW in the FY2006 budget.

According to the NNSA budget request the RRW:

"Is to demonstrate the feasibility of developing reliable replacement components that are producible and certifiable for the existing stockpile. The initial focus will be to provide cost and schedule efficient replacement pits that can be certified without underground tests.

This program justification is similar to the pre-existing stockpile LEP which also develops reliable replacement components, though not for warhead pits (the hollow plutonium core found in each warhead) or other non-replaceable "physics package" (nuclear explosive) components. A key motivation for interest in replacement pits is long standing concern about how long pits manufactured decades ago would remain reliable against corrosion and other forms of deterioration. In general the original formulation of RRW seems to have been a more thorough going and ambitious version of LEP. The latter program was conservative – it attempted to minimize changes to the warhead – while RRW sought to remanufacture the entire weapon.

In November 2006 the JASONs, a select panel of scientific advisors, issued a report reviewing seven years of research on plutonium pit deterioration and found that they would remain reliable for up to 100 years. This finding seemingly undercut the NNSAs FY2006 budget justification for the RRW program.

On 7 January 2007 The New York Times reported that the interagency Nuclear Weapons Council would announce the following week a major decision for RRW. The two nuclear weapon labs, it was revealed, had developed competing proposals for RRW – neither of which was in the mold of "LEP-plus". Instead both labs proposed replacing the entire existing arsenal of warheads with new designs. The Los Alamos National Laboratory (LANL) proposal drew on aspects of many weapons from the stockpile and pulled them together in a novel design that has never undergone testing. he Livermore National Laboratory in California, approached the problem with very different philosophies, nuclear officials and experts said. The Lawrence Livermore National Laboratory (LLNL) proposal was based on a robust warhead design that had been tested in the 1980s, prior to the nuclear testing moratorium. This weapon (which might possibly be either the CALMENDRO or MUNSTER warhead designs previously considered for deployment in the 1980s) has never entered the nation’s nuclear stockpile.

Reportedly the new decision on RRW however would not select between the two proposals, but would instead combine them, yielding yet another novel warhead.

The tables below give a summary breakdown of the U.S. stockpile. Clicking on the last column of the table will bring up a detailed description of the correspondng weapon.

United States Nuclear Weapon Stockpile

Designation
Warhead Type
Yield (Kilotons)
Active
Stockpile
Inactive
Total
First Produced
Click For More Info

B61
  Mod-3
  Mod-4
  Mod-7
  Mod-10
  Mod-11
Bomb
  Tactical
  Tactical
  Tactical
  Strategic
  Tactical/Strategic
0.3 / 1.5 / 60 / 170
0.3 / 1.5 / 10 / 45
10 / ? / 340
0.3 / 5 / 10 / 80
0.3? / ? / 340
200
200
215
0
20
186
204
224
206
21
386
404
439
206
41
10/1979*
8/1979*
9/1985
1990
1/1997

W62/Mk-12
Ballistic Missile
Warhead/RV
170
330
250
580
3/1970
Start of retirement 10/2006, completion in 2009
To be dismantled

W76/Mk-4
Ballistic Missile
Warhead/RV
100
1712
1318
3030
6/1978*

W76-1/Mk-4A
Ballistic Missile
Warhead/RV
100
0
0
0
Life extension mod; first delivery 9/2007

W78/Mk-12a
Ballistic Missile
Warhead/RV
335
785
20
805
8/1979*

W80
  Mod 0
  Mod 1
  Mod 2
  Mod 3
Cruise Missile Warhead
  Sea Launched
  Air Launched
  Sea Launched
  Air Launched
5 / 150
100
1450
0
0
194
361
0
0
294
1811
0
0
12/1981
12/1981*
Life extension mod: 2006
Life extension mod: 2008

B83-0/B83-1
Bomb-Strategic
low to 1200
320
306
626
6/1983

W84
Cruise Missile Warhead
0.3 / ? / 150
0
383
383
6/1983
to be dismantled

W87/Mk-21

Ballistic Missile
Warhead/RV
300
10
543
553
4/1986
Began replacing W62 10/2006
Current deployment rate one per week
330 to be deployed by 2009

W88/Mk-5
Ballistic Missile
Warhead/RV
475
404
0
404
9/1988
No Graphic Available

* To be partly dismantled as part of Moscow Treaty arsenal reduction.

Principal Sources:
Chuck Hansen. Swords of Armageddon 1996, VI-439 to VI-442.
Chuck Hansen. U.S. Nuclear Weapons: The Secret History 1988
Thomas B. Cochran, William M. Arkin, and Milton M. Hoenig. Nuclear Weapons Databook: U.S. Nuclear Forces and Capabilities 1984
Robert S. Norris and Hans M. Kristensen. The Bulletin of the Atomic Scientists, Vol. 59, No. 1 (Jan./Feb. 2003), p. 74-76.
The B61 Family of Bombs, Robert S. Norris, Hans M. Kristensen, Joshua Handler in The Bulletin of the Atomic Scientists, Vol. 62, No. 1 (Jan./Feb. 2006), p. 68-71.
James N. Gibson. Nuclear Weapons of the United States 1996.
Jonathan Medalia. Nuclear Weapons: The Reliable Replacement Warhead Program, CRS-RL32929, Congressional Research Service, The Library of Congress, 9 March 2006.

 

 

Principles of Nuclear Weapons Security and Safety

Last changed 1 October 1997

Due to their extreme destructiveness, nuclear weapons require stringent measures to ensure that they are never detonated, either intentionally or by accident, except under properly authorized circumstances. In addition, since most nuclear weapons contain strongly radiotoxic materials (plutonium and tritium) it is important to prevent accidental release of these materials in an accident.

The first line of defense against accident is to design into the weapon an "exclusion zone" that encloses the detonation system and physically prevents electrical energy from reaching it. Access from the firing system is provided by a "strong link". This is a mechanism (a motorized switch for example) that maintains physical isolation unless it is closed by the arming system. The strong link is thus the ‘draw bridge’ across the exclusion zone ‘moat’.

Now it is possible for an accident of some kind (a crash, fire, munition explosion, lightning strike, etc.) to destroy the integrity of the exclusion zone or the strong link and theoretically open the possibility of the detonation system being activated. To prevent this, there is one or more "weak links" is inserted into the detonation system inside the exclusion zone. These weak links will fail, rendering the weapon inoperable, when exposed to abnormal stresses (heat, acceleration forces, etc.) that are below the level that could possibly disrupt exclusion zone integrity.

Result – any accident that could circumvent the exclusion zone/strong link protections will disable the weapon by breaking the weak links first.

The first line of defense against unauthorized activation is a lock on the weapon. The earliest locks were mechanical combination locks, but since the early 1960s a more sophisticated system called a "permissive action link" (PAL) has been increasingly employed. A PAL is an electronic (originally electro-mechanical) device that prevents arming the weapon unless the correct codes are inserted into it. Two different codes must be inserted, simultaneously or close together. This is the "two man rule" principle – which requires it to be impossible to arm any nuclear weapon through the actions of a single individual. The codes are usually changed on a regular schedule. PALs have been developed in several versions of increasing sophistication, designated A through F.

Once the PAL has been enabled, it now possible to arm and fire the weapon. The "unique signal generator" is a technique for making the weapon extremely discriminating about the arming signal so that spoofing signals, noise, or other interference will not cause arming. There is a signal recognition system in the weapon that responds only to a single, very specific, complex signal. This signal is produced by the unique signal generator (which is actually outside the weapon). A more recent approach has been to replace the unique (analog) signal approach with digital communinications and codes.

Once the weapon is armed, "environmental sensing devices" (ESDs) prevent detonation of the weapon unless it is properly delivered to the target. These devices detect external effects that should occur during the delivery process, things like – free fall period, acceleration curves, temperature, pressures, etc. Unless these effects are detected in the proper sequence, and fall within specified parameters, the weapon will not detonate.

There are other safety measures that have been included in some or all modern weapons:

• "Fire resistant pits" (FRPs) that prevent molten plutonium from escaping in a fire (probably by containing it within the high melting point beryllium reflector shell);
• "Insensitive high explosives" (IHE), these use the explosive TATB which is highly resistant to "cooking off" in a fire, or being detonated by mechanical shock;
• Insulating containers may be used to reduce the influx of heat from a fire,
• "Limited retry" may be used in a PAL. This disables the PAL if the wrong combination is entered too many times, requiring factory service to restore (the same way ATMs will eat a ATM card if the wrong PIN number is entered repeatedly).
• Weapons can also use active self-damaging mechanisms that break bomb components, requiring factory repair before the weapon can be fired, if tampering (including excessive retrys) is detected. Recent weapons have "noviolent" (non-explosive) disablement systems. These systems can also be activated by remote command in some weapons.

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Sources

• The Swords of Armageddon, by Chuck Hansen, Chuckelea Pub., 1995.
• Nuclear Weapons Databook Volume I: U.S. Nuclear Forces and Capabilities, by Thomas B. Cochran, William M. Arkin, and Milton M. Hoenig; NRDC, 1984.
• Managing Nuclear Operations, Ashton B. Carter, John D. Steinbruner, Charles A. Zraket ed.; Brookings Institute, 1987.

PAL
Category
Description

(none)
Mechanical combination lock

A
Four-digit, 10-position electromechanical coded switch (most retired or replaced by 1987)

B
Ground & airplane-operable 4-digit coded switch (later version with limited try followed by lockout until reset)

C
Single-code 6-digit switch, limited try followed by lockout

D
Multiple-code 6-digit switch, limited try followed by lockout

F
Multiple-code 12-digit switch, limited try followed by lockout