Operation Wigwam

{{Infobox nuclear weapons test

| name = Operation Wigwam

| picture = 300px

| picture_description = Wigwam test detonation.

| country = United States

| test_site = Pacific Ocean off California

| period = 1955

| number_of_tests = 1

| test_type = Underwater

| max_yield = {{Convert|30|ktTNT|lk=in}}

| previous_series = Operation Teapot

| next_series = Project 56 (nuclear test)

}}

File:Operation Wigwam test.ogv

Operation Wigwam involved a single test of the Mark 90 "Betty" nuclear bomb. It was conducted between Operation Teapot and Project 56 on May 14, 1955, about 500 miles (800 km) southwest of San Diego, California. 6,800 personnel aboard 30 ships were involved in Wigwam. The purpose of Wigwam was to determine the vulnerability of submarines to deeply detonated nuclear weapons, and to evaluate the feasibility of using such weapons in a combat situation.{{Cite web | url= https://apps.dtic.mil/sti/pdfs/ADA995001.pdf | archive-url= https://web.archive.org/web/20211201122003/https://apps.dtic.mil/sti/pdfs/ADA995001.pdf | url-status= live | archive-date= December 1, 2021 |title=Operation WIGWAM, Report of Commander, Task Group 7.3 | format=61 pg. PDF | date=July 22, 1955 | access-date=December 1, 2021}} The task force commander, Admiral John Sylvester, was embarked on the task force flagship {{USS|Mount McKinley}}. Wigwam was the first atomic test in the deep ocean, and it remains the only test that has been conducted in water deeper than {{cvt|1000|ft}}.{{Cite journal | doi = 10.1121/1.1908930 | journal = J. Acoust. Soc. Am. | title = Measurement of the attenuation of low-frequency underwater sound | year = 1957 | last1 = Sheehy | first1 = M. J. | last2 = Halley | first2 = R.| volume = 29 | issue = 4 | pages = 464–469 |bibcode =1957ASAJ...29..464S| doi-access = free }}{{Cite journal | doi = 10.1785/0120150024 | journal = Bulletin of the Seismological Society of America| title = WIGWAM reverberation revisited | year = 2015 | last1 = Dushaw | first1 = B. | volume = 105 | issue = 4| pages = 2242–2249 | bibcode = 2015BuSSA.105.2242D| url = https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/105/4/2242/332323/wigwam-reverberation-revisited | access-date=July 14, 2018| url-access = subscription }}

Detonation layout and test

File:The 1955 Wigwam test.jpg

The test device was suspended to a depth of {{Convert|2000|ft}} by cable attached to a barge. A {{Convert|6|mi|km|0|spell=on|sp=us|abbr=off|adj=on}} tow line connected the {{convert|205|ft|m|adj=on}} Cherokee-class fleet tug, {{USS|Tawasa|AT-92|6}}, to the shot barge. Suspended from the tow lines of other tugs were three miniature unmanned target submarines designated "SQUAWS", each packed with cameras and telemetry instruments. Those targets were {{cvt|132|ft|2.625|in|m|1|abbr=on}} long, {{Sfrac|4|5}} scale of the SS-563 prototype hull ({{USS|Tang|SS-563||}}) to assess effects of the explosion on a submarine hull.

The time of detonation was 13:00 local Pacific Time (noon Pacific Standard Time).

The equipment intended for direct measurement of the explosion-generated underwater bubble was not operational at the time of the shot, but based on other measurements, the bubble's maximum radius was calculated as {{Convert|376|ft}}, and its pulsation period approximately 2.83 seconds.{{Cite web|url=https://apps.dtic.mil/sti/pdfs/ADA995030.pdf |archive-url=https://web.archive.org/web/20211201122002/https://apps.dtic.mil/sti/pdfs/ADA995030.pdf |url-status=live |archive-date=December 1, 2021 |title=Operation WIGWAM, Scientific Director's Summary Report |format=178 pg. PDF |date=October 10, 1958 |access-date=December 1, 2021}}

See also the table at List of United States' nuclear weapons tests.

Underwater sound

The underwater sound from the Wigwam explosion was recorded on bottom-mounted hydrophones at Point Sur and Point Arena off California, and at Kāneʻohe Bay off Oahu, Hawaii. The sound emanating from the explosive test began as an intense water shock wave. As the sound traveled away from the test point, it reflected from topographic features, such as islands and seamounts, located throughout both the North and South Pacific Basins. The reflected sound was then recorded as hours-long coda{{cfn|date=June 2025}} at Kaneohe and Point Sur. Some of the acoustic energy travelled round trip distances of over {{convert|20,000|km|order=flip}}. The sound signals provided one of the early measurements of underwater sound attenuation at low frequencies.

Detonations

The detonations in the United States' Wigwam series are listed below:

class="wikitable sortable" \|+ United States' Wigwam series tests and detonations
style="background:#ffdead;" \| NameThe US, France and Great Britain have code-named their test events, while the USSR and China did not, and therefore have only test numbers (with some exceptions – Soviet peaceful explosions were named). Word translations into English in parentheses unless the name is a proper noun. A dash followed by a number indicates a member of a salvo event. The US also sometimes named the individual explosions in such a salvo test, which results in "name1 – 1(with name2)". If test is canceled or aborted, then the row data like date and location discloses the intended plans, where known. !style="background:#efefef;" \| Date time (UT) !style="background:#ffdead;" \| Local time zoneTo convert the UT time into standard local, add the number of hours in parentheses to the UT time; for local daylight saving time, add one additional hour. If the result is earlier than 00:00, add 24 hours and subtract 1 from the day; if it is 24:00 or later, subtract 24 hours and add 1 to the day. Historical time zone data obtained from the IANA time zone database.{{Cite web\| title=Time Zone Historical Database\| publisher=iana.com\| url=http://www.ietf.org/timezones/\| access-date=March 8, 2014}} !style="background:#efefef;" \| LocationRough place name and a latitude/longitude reference; for rocket-carried tests, the launch location is specified before the detonation location, if known. Some locations are extremely accurate; others (like airdrops and space blasts) may be quite inaccurate. "~" indicates a likely pro-forma rough location, shared with other tests in that same area. !style="background:#ffdead;" \| Elevation + heightElevation is the ground level at the point directly below the explosion relative to sea level; height is the additional distance added or subtracted by tower, balloon, shaft, tunnel, air drop or other contrivance. For rocket bursts the ground level is "N/A". In some cases it is not clear if the height is absolute or relative to ground, for example, Plumbbob/John. No number or units indicates the value is unknown, while "0" means zero. Sorting on this column is by elevation and height added together. !style="background:#efefef;" \| Delivery,Atmospheric, airdrop, balloon, gun, cruise missile, rocket, surface, tower, and barge are all disallowed by the Partial Nuclear Test Ban Treaty. Sealed shaft and tunnel are underground, and remained useful under the PTBT. Intentional cratering tests are borderline; they occurred under the treaty, were sometimes protested, and generally overlooked if the test was declared to be a peaceful use. PurposeInclude weapons development, weapon effects, safety test, transport safety test, war, science, joint verification and industrial/peaceful, which may be further broken down. !style="background:#efefef;" \| DeviceDesignations for test items where known, "?" indicates some uncertainty about the preceding value, nicknames for particular devices in quotes. This category of information is often not officially disclosed. !style="background:#ffdead;" \| YieldEstimated energy yield in tons, kilotons, and megatons. A ton of TNT equivalent is defined as 4.184 gigajoules (1 gigacalorie). !style="background:#efefef;" class="unsortable" \| FalloutRadioactive emission to the atmosphere aside from prompt neutrons, where known. The measured species is only iodine-131 if mentioned, otherwise it is all species. No entry means unknown, probably none if underground and "all" if not; otherwise notation for whether measured on the site only or off the site, where known, and the measured amount of radioactivity released. !style="background:#ffdead;" class="unsortable" \| References !style="background:#efefef;" class="unsortable" \| Notes
Wigwam{{Anchor\|Wigwam}} \| {{Dts\|1955\|5\|14}} 20:00:00.0 \| style="text-align:center;" \| PST (−8 hrs) \|\| Pacific Ocean off California {{Coord\|28.7333
126.2667\|type:event\|name=Wigwam\|display=it}} \| {{Sort\|000000

class="wikitable sortable"

|+ United States' Wigwam series tests and detonations

style="background:#ffdead;" | NameThe US, France and Great Britain have code-named their test events, while the USSR and China did not, and therefore have only test numbers (with some exceptions – Soviet peaceful explosions were named). Word translations into English in parentheses unless the name is a proper noun. A dash followed by a number indicates a member of a salvo event. The US also sometimes named the individual explosions in such a salvo test, which results in "name1 – 1(with name2)". If test is canceled or aborted, then the row data like date and location discloses the intended plans, where known.

!style="background:#efefef;" | Date time (UT)

!style="background:#ffdead;" | Local time zoneTo convert the UT time into standard local, add the number of hours in parentheses to the UT time; for local daylight saving time, add one additional hour. If the result is earlier than 00:00, add 24 hours and subtract 1 from the day; if it is 24:00 or later, subtract 24 hours and add 1 to the day. Historical time zone data obtained from the IANA time zone database.{{Cite web| title=Time Zone Historical Database| publisher=iana.com| url=http://www.ietf.org/timezones/| access-date=March 8, 2014}}

!style="background:#efefef;" | LocationRough place name and a latitude/longitude reference; for rocket-carried tests, the launch location is specified before the detonation location, if known. Some locations are extremely accurate; others (like airdrops and space blasts) may be quite inaccurate. "~" indicates a likely pro-forma rough location, shared with other tests in that same area.

!style="background:#ffdead;" | Elevation + heightElevation is the ground level at the point directly below the explosion relative to sea level; height is the additional distance added or subtracted by tower, balloon, shaft, tunnel, air drop or other contrivance. For rocket bursts the ground level is "N/A". In some cases it is not clear if the height is absolute or relative to ground, for example, Plumbbob/John. No number or units indicates the value is unknown, while "0" means zero. Sorting on this column is by elevation and height added together.

!style="background:#efefef;" | Delivery,Atmospheric, airdrop, balloon, gun, cruise missile, rocket, surface, tower, and barge are all disallowed by the Partial Nuclear Test Ban Treaty. Sealed shaft and tunnel are underground, and remained useful under the PTBT. Intentional cratering tests are borderline; they occurred under the treaty, were sometimes protested, and generally overlooked if the test was declared to be a peaceful use.
PurposeInclude weapons development, weapon effects, safety test, transport safety test, war, science, joint verification and industrial/peaceful, which may be further broken down.

!style="background:#efefef;" | DeviceDesignations for test items where known, "?" indicates some uncertainty about the preceding value, nicknames for particular devices in quotes. This category of information is often not officially disclosed.

!style="background:#ffdead;" | YieldEstimated energy yield in tons, kilotons, and megatons. A ton of TNT equivalent is defined as 4.184 gigajoules (1 gigacalorie).

!style="background:#efefef;" class="unsortable" | FalloutRadioactive emission to the atmosphere aside from prompt neutrons, where known. The measured species is only iodine-131 if mentioned, otherwise it is all species. No entry means unknown, probably none if underground and "all" if not; otherwise notation for whether measured on the site only or off the site, where known, and the measured amount of radioactivity released.

!style="background:#ffdead;" class="unsortable" | References

!style="background:#efefef;" class="unsortable" | Notes

Wigwam{{Anchor|Wigwam}}

| {{Dts|1955|5|14}} 20:00:00.0

| style="text-align:center;" | PST (−8 hrs)
|| Pacific Ocean off California {{Coord|28.7333

126.2667|type:event|name=Wigwam|display=it}}

| {{Sort|000000

}0–{{Convert|610|m|abbr=on}}

| underwater,
weapon effect

| Mk-90 B7 "Betty" depth bomb

| style="text-align:center;" | {{Sort|000300000|30 kt}}

| Deep water submarine hull test, including nuclear depth bomb, to gauge surface contamination. Used instrumented "squaws", subscale sub pressure hulls. Tested shielded warships with base surge.

References

= Explanatory notes =

= Citations =

{{Reflist|refs=

{{Citation| url=http://www.nuclearweaponarchive.org/Usa/Tests| access-date=January 6, 2014| last=Sublette| first=Carey| title=Nuclear Weapons Archive}}

{{Citation| last1=Yang| first1=Xiaoping| first2=Robert| last2=North| first3=Carl| last3=Romney| date=August 2000| title=CMR Nuclear Explosion Database (Revision 3)| publisher=SMDC Monitoring Research}}

{{Citation| publisher=Department of Energy, Nevada Operations Office| date=December 1, 2000| title=United States Nuclear Tests: July 1945 through September 1992| type=DOE/NV-209 REV15| location=Las Vegas, Nevada| url=http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf| access-date=December 18, 2013| url-status=dead| archive-url=https://web.archive.org/web/20061012160826/http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf| archive-date=October 12, 2006}}

}}

External links

{{Internet Archive short film|id=gov.doe.0800018|name=Nuclear Test Film—Operation Wigwam (1955)}}
[https://www.ctbto.org/specials/testing-times/14-may-1955-wigwam/ 14 May 1955—Wigwam]—A description of the WIGWAM test and its radiation aftereffects at the Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission Web site

Category:1955 in California

Category:1955 in military history

Wigwam

Category:Articles containing video clips

Category:Explosions in 1955

Category:May 1955 in Oceania

Category:Military history of the Pacific Ocean