U.S. Underwater Nuclear Testing
and
Derived Effects Data

(Updated 29 October 2012)

References:
WT-1003(EX) Operation Wigwam, Scientific Director's Summary Report. (12.8 MB PDF)
DNA 6038F Operation Hardtack I – 1958 (35~ MB PDF)
WT-1608: Operation Hardtack – Project 1.3 Surface Phenomena from Underwater Bursts (13.9~ MB PDF)
WT-1629(EX) Operation Hardtack – Project 3.5: Loading and Response of Submarine Hulls from Underwater Bursts. (3.7~ MB PDF)
Effects of Nuclear Weapons, Chapter 6; 1977

Operation Crossroads

Shot Baker was fired from a depth of 90 feet in water only 180 feet deep. Yield was 23.5 kilotons.

Operation WIGWAM

On 14 May 1955, at 126°16' W 28°44' N (560~ miles off the coast of Baja California) in water about 16,000 feet deep, the US Navy tested a Mark 90 “Alias Betty” Nuclear Depth Bomb with a yield of 32~ kilotons.

The device itself was suspended at a depth of 2,000 feet under the barge YC-473 via a cable for the test, and around the device at varying distances to measure the effects of the NDB in the anti submarine role were three instrumented sub-scale submarine models dubbed SQUAWs.


SQUAW Outboard and Inboard Profiles

The SQUAWs were simplified 4/5th scale models of SS 563 Tang class submarines 134 feet long, with 14.5 foot diameter pressure hulls constructed of 1” thick HTS plate with a yield strength of 56,000 PSI, using one dimensional bends only for economy of production. Pressure hull end caps were constructed of STS. Total beam was about 22' 12”, and displacement was about 400~ tons. Engine-Generators were simulated with 4/5th scale cast iron weights weighing 11,900 lbs each. Motors were also 4/5th scale cast iron weights, weighing 25,000 lbs each. Batteries were simulated by concrete weights. Three were constructed by Long Beach Naval Shipyard and designated SQUAW 12, 13, and 29 respectively.

The following effects on the SQAWs during WIGWAM were observed:

The shockwave from the device at 2,000 feet produced a spray dome on the surface with a 7,000 foot radius and a central height of 170 feet. This was followed by a second spiky dome from the bubble pulse which rose to about 900 feet.

The following radiological effects on the ocean were observed after the WIGWAM shot.

Area of Contamination
(square miles)

Time From Initiation

Radiation
3 feet above ocean surface
(millirems/hr)

5.5

+30 Minutes

250,000 (250 REMs)

13.1

+24 Hours

70 (0.07 REMs)

19

1.7 Days

10 (0.01 REMs)

25

2.7 Days

3

80

4 Days

1

250

10 Days

0.2

Statements made after WIGWAM concerned what had been learned concerning weapons effects:

When submerged to a depth of 250 ft, a well-designed, modern submarine structure having a hydrostatic collapse depth of 1,465 ft will be ruptured if closer than 7000 ft to the detonation of a nuclear device having a radio-chemical yield of 32 kt and occurring at a depth of 2000 ft in deep (over 6000 ft) water.”


These criteria indicate that a light-hulled fleet type submarine (650-ft static collapse) may be expected to receive lethal damage when operating at a depth of 250 ft if a 32-kt weapon is detonated 2000 ft deep at a range of less than 14,000 ft in deep water.”

As well as one semi-humorous finding regarding the excellent transmission of the sound of the shot:

The sounds [of the initiation] were well perceived through the hulls of surface ships at considerable ranges. A Greek ship just off the Golden Gate [568 nautical miles to the north-east] radioed the Coast Guard at San Francisco asking if that city had just been hit by a severe earthquake. The ship had been badly shaken but was undamaged and would render assistance if needed!”

Operation HARDTACK I (Shot WAHOO)

Video of Operation HARDTACK I can be found at the Internet Archive HERE

Shot WAHOO, a subsurface nuclear detonation in the HARDTACK I series of tests was fired at 1330 on 16 May 1958 at Eniwetok Atoll. The device was suspended 500 feet below a target barge via cable.

With a water depth of 3,000 feet, and with an estimated yield of 9 kilotons, Wahoo produced a spray dome some 3,800 feet in diameter, with a central height of some 840 feet.

Engineering Spaces: Personnel were generally calm, though considered it violent. In some cases personnel were frightened.

Lower Sound Room: Shock wave sounded like water rushing by the ship. Shock wave shook ship violently with a loud cracking noise. Personnel were somewhat frightened.

Bosun's Locker: Ship vibrated violently, first fast then slow. Sounded like water pouring into the ship. Personnel were considerably frightened.

Shot UMBRELLA, a shallow underwater nuclear detonation in the HARDTACK I series of tests was fired at 1115 on 8 June 1958 at Eniwetok Atoll. The device was fired from the bottom of Eniwetok lagoon at a depth of 150 feet.

With an a estimated yield of 8 kilotons and in very shallow water, Umbrella produced a spray dome that was truly massive, with a maximum height of about 5,000 feet.

Conclusions

From the above tests previously detailed, the following was learned:

Calculations/Math

Surface Wave Motions From Deep Underwater Bursts

Peak to Peak Wave Height (ft) = 40,500 * ( (Yield0.54) / RangeBurst

Yield is in kilotons and the RangeBurst is in feet. Accuracy of the above equation is ±35%.

Thus, a ship 5,000 feet from a 32 kiloton device initiated in deep water would encounter peak waves between:

40,500 * ( (320.54) / 5,000 = 52.63 feet
52.63 feet * 0.35 = 18.4 feet
52.63 + 18.4 = 71.03
52.63 – 18.4 = 34.23
34 and 71 feet in height.

Other equations are available for computing the Peak Wave length and period. They are:

Length of Peak Wave (ft) = 1010 * Yield0.288
Period of Peak Wave (Sec) = 14.1 * Yield0.288

In both cases, yield is again in kilotons.

Scaling Factors for Underwater Bursts in Deep Water

Notes: Yield is in Kilotons, and Distances are in meters.

50 PSI Distance= Yield0.342 * 6,769.5
100 PSI Distance = Yield0.342 * 3,705.4
200 PSI Distance = Yield0.342 * 2,028.2
400 PSI Distance = Yield0.342 * 1,110.2
500 PSI Distance = Yield0.342 * 914.4
600 PSI Distance = Yield0.342 * 780.4
700 PSI Distance = Yield0.342 * 682.5
800 PSI Distance = Yield0.342 * 607.7
900 PSI Distance = Yield0.342 * 548.5
1000 PSI Distance = Yield0.342 * 500.5
1500 PSI Distance = Yield0.342 * 352.7
2000 PSI Distance = Yield0.342 * 270
2500 PSI Distance = Yield0.342 * 225.7