View source for Operation Hardtack II

{{Short description|Series of 1950s US nuclear tests}}
{{Use American English|date=December 2024}}
{{Use dmy dates|date=December 2024}}
{{Infobox nuclear weapons test
 |name                = Operation Hardtack II
 |picture             = [[File:Hardtack_II_Sandford.gif|300px]]
 |picture_description = Hardtack II Sanford, 4.9 kilotons.
 |country             = United States
 |test_site           = {{plainlist|
* NTS Area 12, Rainier Mesa
* NTS Areas 5, 11, Frenchman Flat
* NTS, Areas 1–4, 6–10, Yucca Flat
}}
 |period              = 1958
 |number_of_tests     = 37
 |test_type           = balloon, dry surface, tower, underground shaft, tunnel
 |max_yield           = {{convert|22|ktTNT|lk=in}}
 |previous_series     = [[Operation Argus]]
 |next_series         = [[Operation Nougat]]
}}

{{GeoGroup|article=Operation Hardtack II}}

'''Operation Hardtack II'''<ref name=LT_1 /> was a series of 37 [[nuclear test]]s conducted by the United States in 1958 at the [[Nevada Test Site]]. These tests followed the ''[[Operation Argus]]'' series and preceded the ''[[Operation Nougat]]'' series.

With test moratoriums on the horizon, American weapons labs rushed out many new designs. A hard deadline for testing was set at midnight (0000 hrs), 31 October 1958, as negotiations were set to start that day, and the schedule shows it, with 29 tests executed in October, four of them on the last day.  One other test was cancelled because weather delays postponed it across the midnight deadline.  After the conclusion of Hardtack II, the United States announced a unilateral testing moratorium, which the Soviet Union joined after two last tests on 1 and 3 November.<ref>{{cite web | url=http://nuclearweaponarchive.org/Usa/Tests/ | title=Gallery of U.S. Nuclear Tests }}</ref>  In September 1961, the Soviet Union resumed nuclear testing — including the test of the most powerful nuclear device ever designed, the ''[[Tsar Bomba]]'', in October — and the United States followed suit with ''[[Operation Nougat]]''.

==Nuclear tests==
===Tamalpais===

The Tamalpais test was conducted in the U12b.02 adit of Rainier Mesa by Lawrence Radiation Laboratory on October 8, 1958.<ref name="LT_6" /> The shot took place in a 394-foot-long hook-shaped drift ending in an unusually large test chamber lined with salt blocks as part of an experiment in preparation for [[Project Gnome]].<ref>{{cite web |last1=Nifontov |first1=B.I. |last2=Protopopov |first2=D.D. |last3=Sitnikov |first3=I.E. |last4=Kulikov |first4=A.V. |title=Underground Nuclear Explosions - Problems of Industrial Nuclear Explosions |url=https://apps.dtic.mil/sti/tr/pdf/ADA397133.pdf |website=Defense Technical Information Center |publisher=Atomizdat - Atomic Energy Commission |access-date=15 January 2025 |page=18 |date=October 1966}}</ref><ref name="Holmes & Narver report">{{cite web |title=Completion Report - Operation Hardtack, Phase II |url=https://apps.dtic.mil/sti/tr/pdf/ADA995180.pdf |website=Defense Technical Information Center |publisher=Holmes & Narver Inc. |access-date=15 January 2025 |pages=59–61}}</ref> Additional experiments included measuring permanent tunnel displacement, seismic ground shock measurement, gas sampling by Oak Ridge National Laboratory, and electromagnetic pulse measurement by the Department of Defense Effects Test Group.{{r|"Holmes & Narver report"|p=23}}<ref name="DNA report">{{cite web |last1=Ponton |first1=Jean |last2=Rohrer |first2=Stephen |last3=Maag |first3=Carl |last4=Shepanek |first4=Robert |last5=Gravitis |first5=Inara |title=Operation Hardtack II - Technical Report |url=https://apps.dtic.mil/sti/pdfs/ADA130929.pdf |website=Defense Technical Information Center |publisher=Defense Nuclear Agency |access-date=15 January 2025 |pages=96–100 |date=December 3, 1982}}</ref><ref name="ORNL gas sampling">{{cite web |last1=Clark |first1=W.E. |title=The ORNL Gas Sampling Experiment in Connection with the Tamalpais Event |url=https://www.osti.gov/servlets/purl/4753212 |website=Department of Energy Office of Scientific and Technical Information |publisher=Oak Ridge National Laboratory |date=January 7, 1963}}</ref> The detonation of the .072 kiloton device released significant radioactive contamination and damage to the U12 tunnel complex, with radiation levels of 50R/h at the main portal and in the 10,000 R/h range in the tunnel immediately following detonation.<ref name="DNA report" /><ref name="Caging the Dragon">{{cite book |last1=Carothers |first1=James |title=Caging the Dragon - The Containment of Underground Explosions |date=1995 |publisher=Lawrence Livermore National Laboratory |location=Livermore, CA |url=https://apps.dtic.mil/sti/tr/pdf/ADB213716.pdf |access-date=15 January 2025}}</ref>{{rp|421}} The following day, workers reentered the tunnel and triggered a significant hydrogen gas explosion that further damaged the tunnel and injured three workers. Following the tunnel's evacuation, a second hydrogen explosion occurred later the same day.<ref name="Holmes & Narver report" /><ref name="Caging the Dragon" />{{rp|421–423}}

===Adams===
Adams was planned to be the final test of Hardtack II, but due to unfavorable winds the shot was never fired. The shot was intended to be a balloon test, and had been fully assembled and raised to firing altitude when it was cancelled. After midnight and the start of the moratorium, the device was lowered to the ground and disassembled. The Soviet Union would continue nuclear testing until 3 November.<ref>{{Cite report| publisher = Los Alamos National Lab. (LANL), Los Alamos, NM (United States)| last = Meade| first = Roger Allen| title = Hardtack II| access-date = 2024-01-23| date = 2022-09-12| url = https://www.osti.gov/biblio/1887122}}</ref>

A 31 October 1958 meeting of the Atomic Energy Commission following the cancellation resulted in the following note:<ref>{{Cite report| publisher = US Department of Energy (USDOE), Nevada Operations Office.| last = William E Ogle| title = An Account of the Return to Nuclear Weapons Testing by the United States After the Test Moratorium 1958-1961| access-date = 2021-07-16| date = October 1985| url = https://www.osti.gov/opennet/detail?osti-id=16156584|pages=107–108}}</ref>
{{Blockquote
|text=[{{Zwsp}}[[Alfred Starbird|General Alfred Starbird]]{{Zwsp}}] said there will always be a question as to whether the final shot should have been fired in view of its importance [redacted] but he believed that the other considerations were of overriding importance.
}}

==List of nuclear tests==

{{See also|List of nuclear weapons tests of the United States}}

{| class="wikitable sortable"
 |+ United States' Hardtack II series tests and detonations
 |-
 !style="background:#ffdead;" | Name <ref group=note>The 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.</ref>
 !style="background:#efefef;" | Date time ([[Universal Time|UT]])
 !style="background:#ffdead;" | Local [[Time Zone|time zone]]<ref group=note>To 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 [[tz database|IANA time zone database]].</ref><ref>{{cite web| title=Time Zone Historical Database| publisher=iana.com| url=http://www.ietf.org/timezones/| access-date=8 March 2014}}</ref>
 !style="background:#efefef;" | [[List of nuclear test sites|Location]]<ref group=note>Rough 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.</ref>
 !style="background:#ffdead;" | [[Elevation]] + height <ref group=note>Elevation 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.</ref>
 !style="background:#efefef;" | Delivery <ref group=note>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.</ref><br />Purpose <ref group=note>Include weapons development, weapon effects, safety test, transport safety test, war, science, joint verification and industrial/peaceful, which may be further broken down.</ref>
 !style="background:#efefef;" | [[List of nuclear weapons|Device]]<ref group=note>Designations 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.</ref>
 !style="background:#ffdead;" | [[Nuclear weapon yield|Yield]]<ref group=note>Estimated energy yield in [[TNT equivalent|tons, kilotons, and megatons]]. A ton of TNT equivalent is defined as 4.184&nbsp;gigajoules (1&nbsp;gigacalorie).</ref>
 !style="background:#efefef;" class="unsortable" | [[Nuclear fallout|Fallout]]<ref group=note>Radioactive 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.</ref>
 !style="background:#ffdead;" class="unsortable" | References
 !style="background:#efefef;" class="unsortable" | Notes
 |-
 ! ''Otero''{{anchor|Otero}}
 | {{dts|format=dmy|1958|9|12}} 20:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3q {{coord|37.04985|-116.03255|name=Otero|display=inline}}
 | {{sort|001079|}}{{convert|1229|m|abbr=on}}–{{convert|150|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W54|XW-54]] ?
 | style="text-align:center;" | {{sort|000000380|38&nbsp;t}}
 | Venting detected, {{convert|6|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | [[Nuclear weapon design#One-point safety|1-point test]], failed, device similar to ''HT-I Sequoia''.
 |-
 ! ''Bernalillo''{{anchor|Bernalillo}}
 | {{dts|format=dmy|1958|9|17}} 19:30:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3h (n?) {{coord|37.04944|-116.03352|name=Bernalillo|display=inline}}
 | {{sort|001079|}}{{convert|1229|m|abbr=on}}–{{convert|150|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W54|XW-54]]
 | style="text-align:center;" | {{sort|000000150|15&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 |  1-point test, repeat of ''Otero'', also failed.
 |-
 ! ''Eddy''{{anchor|Eddy}}
 | {{dts|format=dmy|1958|9|19}} 14:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Eddy|display=inline}}
 | {{sort|001432|}}{{convert|1282|m|abbr=on}} + {{convert|150|m|abbr=on}}
 | balloon,<br />weapons development
 |
 | style="text-align:center;" | {{sort|000000830|83&nbsp;t}}
 | Venting detected, {{convert|12|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | {{convert|154|lb}} test device successful.
 |-
 ! ''Luna''{{anchor|Luna}}
 | {{dts|format=dmy|1958|9|21}} 19:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3m {{coord|37.04919|-116.03447|name=Luna|display=inline}}
 | {{sort|001080|}}{{convert|1230|m|abbr=on}}–{{convert|150|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W54|XW-54]] ?
 | style="text-align:center;" | {{sort|000000015|1.5&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test, repeat of ''Otero/Bernalillo'', still unsafe.
 |-
 ! ''Mercury''{{anchor|Mercury}}
 | {{dts|format=dmy|1958|9|23}} 22:00:00.0
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12f.01 {{coord|37.19274|-116.20024|name=Mercury|display=inline}}
 | {{sort|001982|}}{{convert|2038|m|abbr=on}}–{{convert|55.78|m|abbr=on}}
 | tunnel,<br />safety experiment
 | [[W47|XW-47]] primary ?
 | style="text-align:center;" | {{sort|000000100|10&nbsp;t}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_34 />
 | 1-point test, declared success despite yield, XW-42 test, similar to'' Pascal-C'' and ''San Juan'' devices.
 |-
 ! ''Valencia''{{anchor|Valencia}}
 | {{dts|format=dmy|1958|9|26}} 20:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3r {{coord|37.04956|-116.03057|name=Valencia|display=inline}}
 | {{sort|001077|}}{{convert|1227|m|abbr=on}}–{{convert|150|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W47|XW-42]] ?
 | style="text-align:center;" | {{sort|000000020|2&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test, declared success despite yield, similar to ''Pascal-C'' and ''San Juan'' devices.
 |-
 ! ''Mars''{{anchor|Mars}}
 | {{dts|format=dmy|1958|9|28}} 00:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12f.02 {{coord|37.19301|-116.20131|name=Mars|display=inline}}
 | {{sort|002039|}}{{convert|2082|m|abbr=on}}–{{convert|42.67|m|abbr=on}}
 | tunnel,<br />safety experiment
 | [[W48|XW-48]]
 | style="text-align:center;" | {{sort|000000130|13&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_34 />
 | 1-point test, similar to ''Tamalpais'' and ''Ceres''.
 |-
 ! ''Mora''{{anchor|Mora}}
 | {{dts|format=dmy|1958|9|29}} 14:05:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Mora|display=inline}}
 | {{sort|001742|}}{{convert|1282|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000020000|2&nbsp;kt}}
 | Venting detected, {{convert|340|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | Full yield test of device similar to ''Otero'' et al., fizzled.
 |-
 ! ''Hidalgo''{{anchor|Hidalgo}}
 | {{dts|format=dmy|1958|10|5}} 14:10:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Hidalgo|display=inline}}
 | {{sort|001392|}}{{convert|1282|m|abbr=on}} + {{convert|110|m|abbr=on}}
 | balloon,<br />safety experiment
 | Moccasin
 | style="text-align:center;" | {{sort|000000770|77&nbsp;t}}
 | Venting detected, {{convert|11|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | This 1-point test failed; similar to ''Coulomb-C''.
 |-
 ! ''Colfax''{{anchor|Colfax}}
 | {{dts|format=dmy|1958|10|5}} 16:15:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3k {{coord|37.04882|-116.03491|name=Colfax|display=inline}}
 | {{sort|001122|}}{{convert|1229|m|abbr=on}}–{{convert|107|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000000055|5.5&nbsp;t}}
 | Venting detected, {{convert|240|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | 1-point test of device similar to ''Otero'' et al., failed.  Unstemmed shaft.
 |-
 ! ''Tamalpais''{{anchor|Tamalpais}}
 | {{dts|format=dmy|1958|10|8}} 22:00:00.13
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12b.02 {{coord|37.19525|-116.20133|name=Tamalpais|display=inline}}
 | {{sort|002027|}}{{convert|2152|m|abbr=on}}–{{convert|124.05|m|abbr=on}}
 | tunnel,<br />weapons development
 | [[W48|XW-48]]
 | style="text-align:center;" | {{sort|000000720|72&nbsp;t}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_34 />
 | Full yield test, similar to ''Mars'' and ''Ceres''.
 |-
 ! ''Quay''{{anchor|Quay}}
 | {{dts|format=dmy|1958|10|10}} 14:30:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 7c {{coord|37.0947|-116.0245|name=Quay|display=inline}}
 | {{sort|001324|}}{{convert|1294|m|abbr=on}} + {{convert|30|m|abbr=on}}
 | tower,<br />weapons development
 | [[W50 (nuclear warhead)|XW-50]] ?
 | style="text-align:center;" | {{sort|000000790|79&nbsp;t}}
 | Venting detected, {{convert|200|Ci|GBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Concept feasibility test, similar to ''HT-I Linden''.
 |-
 ! ''Lea''{{anchor|Lea}}
 | {{dts|format=dmy|1958|10|13}} 13:20:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Lea|display=inline}}
 | {{sort|001742|}}{{convert|1282|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat ?
 | style="text-align:center;" | {{sort|000014000|1.4&nbsp;kt}}
 | Venting detected, {{convert|240|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_148 />
 | Full yield test of device similar to ''Otero'' et al., fizzled.
 |-
 ! ''Neptune''{{anchor|Neptune}}
 | {{dts|format=dmy|1958|10|14}} 18:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12c.03 {{coord|37.19381|-116.20057|name=Neptune|display=inline}}
 | {{sort|002049|}}{{convert|2080|m|abbr=on}}–{{convert|30.02|m|abbr=on}}
 | tunnel,<br />safety experiment
 | [[W47|XW-47]]
 | style="text-align:center;" | {{sort|000001150|115&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 /><ref name=LT_34 />
 | 1-point test, failed, similar to ''HT-I Hickory'' and ''HT-II Titania''. First NTS subsidence crater at Rainier despite low yield and depth buried.
 |-
 ! ''Hamilton''{{anchor|Hamilton}}
 | {{dts|format=dmy|1958|10|15}} 16:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 5 {{coord|36.8022|-115.9331|name=Hamilton|display=inline}}
 | {{sort|000955|}}{{convert|940|m|abbr=on}} + {{convert|15|m|abbr=on}}
 | tower,<br />weapons development
 | [[XW-51]] ? Quail
 | style="text-align:center;" | {{sort|000000012|1.2&nbsp;t}}
 | Venting detected, {{convert|200|Ci|GBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | ''Davy Crockett'' prototype test, fizzled, extremely small device ({{convert|16|kg|abbr=on}}).
 |-
 ! ''Logan''{{anchor|Logan}}
 | {{dts|format=dmy|1958|10|16}} 06:00:00.14
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area A12e.02 {{coord|37.18399|-116.20206|name=Logan|display=inline}}
 | {{sort|001871|}}{{convert|2155|m|abbr=on}}–{{convert|283.58|m|abbr=on}}
 | tunnel,<br />weapons development
 |
 | style="text-align:center;" | {{sort|000050000|5&nbsp;kt}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 /><ref name=LT_34 />
 | ABM warhead test, small ({{convert|28.6|kg|abbr=on}}, {{convert|28|x|29|cm|abbr=on}}) kiloton-range device, successful.
 |-
 ! ''Dona Ana''{{anchor|Dona Ana}}
 | {{dts|format=dmy|1958|10|16}} 14:20:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Dona Ana|display=inline}}
 | {{sort|001432|}}{{convert|1282|m|abbr=on}} + {{convert|150|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000000370|37&nbsp;t}}
 | Venting detected, {{convert|6|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | Low yield test, similar to Otero et al.
 |-
 ! ''Vesta''{{anchor|Vesta}}
 | {{dts|format=dmy|1958|10|17}} 23:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area S9e {{coord|37.1226|-116.0347|name=Vesta|display=inline}}
 | {{sort|001294|}}{{convert|1294|m|abbr=on}} + 0
 | dry surface,<br />safety experiment
 | [[W47|XW-47]] primary
 | style="text-align:center;" | {{sort|000000240|24&nbsp;t}}
 | Venting detected, {{convert|4|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test, failed, similar to ''Wrangell, Oberon, Sanford''.
 |-
 ! ''Rio Arriba''{{anchor|Rio Arriba}}
 | {{dts|format=dmy|1958|10|18}} 14:25:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 3s {{coord|37.0411|-116.0267|name=Rio Arriba|display=inline}}
 | {{sort|001244|}}{{convert|1224|m|abbr=on}} + {{convert|20|m|abbr=on}}
 | tower,<br />weapons development
 | [[Mark 7 nuclear bomb|Mk-7]]
 | style="text-align:center;" | {{sort|000000900|90&nbsp;t}}
 | Venting detected, {{convert|120|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Low yield Mk-7, successful, fired on wooden tower.
 |-
 ! ''San Juan''{{anchor|San Juan}}
 | {{dts|format=dmy|1958|10|20}} 14:30:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U3p {{coord|37.04976|-116.03325|name=San Juan|display=inline}}
 | {{sort|001158|}}{{convert|1229|m|abbr=on}}–{{convert|71|m|abbr=on}}
 | underground shaft,<br />safety experiment
 | [[W42 (nuclear warhead)|XW-42]] ?
 | style="text-align:center;" | {{sort|000000000|no yield}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test, successful, safe design extrapolated from ''Pascal-C'' and ''HT-II Valencia''. Unstemmed shaft.
 |-
 ! ''Socorro''{{anchor|Socorro}}
 | {{dts|format=dmy|1958|10|22}} 13:30:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Socorro|display=inline}}
 | {{sort|001722|}}{{convert|1282|m|abbr=on}} + {{convert|440|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat ?
 | style="text-align:center;" | {{sort|000060000|6&nbsp;kt}}
 | Venting detected, {{convert|1000|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_148 />
 | Full yield test of XW-54 primary, successful, similar to ''Otero'' et al.
 |-
 ! ''Wrangell''{{anchor|Wrangell}}
 | {{dts|format=dmy|1958|10|22}} 16:50:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 5 {{coord|36.798|-115.9298|name=Wrangell|display=inline}}
 | {{sort|001400|}}{{convert|940|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W47|XW-47]] Canary ?
 | style="text-align:center;" | {{sort|000001150|115&nbsp;t}}
 | Venting detected, {{convert|17|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Full yield test fizzle, similar to ''Vesta, Oberon, Sanford''.
 |-
 ! ''Oberon''{{anchor|Oberon}}
 | {{dts|format=dmy|1958|10|22}} 20:30:??
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 8a {{coord|37.1829|-116.0691|name=Oberon|display=inline}}
 | {{sort|001363|}}{{convert|1355|m|abbr=on}} + {{convert|8|m|abbr=on}}
 | tower,<br />safety experiment
 | [[W47|XW-47]]  primary Canary ?
 | style="text-align:center;" | {{sort|000000000|no yield}}
 | Venting detected, {{convert|17|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_163 />
 | 1-point test, successful, similar to ''Vesta, Wrangell, Sanford''.
 |-
 ! ''Rushmore''{{anchor|Rushmore}}
 | {{dts|format=dmy|1958|10|22}} 23:40:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B9a ~ {{coord|37.1347|-116.0417|name=Rushmore|display=inline}}
 | {{sort|001435|}}{{convert|1285|m|abbr=on}} + {{convert|150|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W47|XW-47]]  primary Canary ?
 | style="text-align:center;" | {{sort|000001880|188&nbsp;t}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Low yield test, fizzled, similar to ''Mercury, Neptune, Titania''.
 |-
 ! ''Catron''{{anchor|Catron}}
 | {{dts|format=dmy|1958|10|24}} 15:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 3t {{coord|37.0427|-116.0277|name=Catron|display=inline}}
 | {{sort|001245|}}{{convert|1225|m|abbr=on}} + {{convert|20|m|abbr=on}}
 | tower,<br />safety experiment
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000000210|21&nbsp;t}}
 | Venting detected, {{convert|4|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 />
 | 1-point test, similar to ''Mora'', failed, fired on wooden tower.
 |-
 ! ''Juno''{{anchor|Juno}}
 | {{dts|format=dmy|1958|10|24}} 16:01:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area S9f {{coord|37.12361|-116.03776|name=Juno|display=inline}}
 | {{sort|001287|}}{{convert|1287|m|abbr=on}} + 0
 | dry surface,<br />safety experiment
 | Logan
 | style="text-align:center;" | {{sort|000000017|1.7&nbsp;t}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test to determine safety limits.
 |-
 ! ''Ceres''{{anchor|Ceres}}
 | {{dts|format=dmy|1958|10|26}} 04:00:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 8b {{coord|37.1814|-116.0691|name=Ceres|display=inline}}
 | {{sort|001360|}}{{convert|1350|m|abbr=on}} + {{convert|10|m|abbr=on}}
 | tower,<br />safety experiment
 | [[W48|XW-48]] AFAP
 | style="text-align:center;" | {{sort|000000007|700&nbsp;kg}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test of atomic artillery shell, similar to ''Tamalpais'' and ''Mars''.
 |-
 ! ''Sanford''{{anchor|Sanford}}
 | {{dts|format=dmy|1958|10|26}} 10:20:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 5 {{coord|36.798|-115.9298|name=Sanford|display=inline}}
 | {{sort|001400|}}{{convert|940|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W47|XW-47]]  primary Canary ?
 | style="text-align:center;" | {{sort|000049000|4.9&nbsp;kt}}
 | Venting detected, {{convert|750|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Full yield test, successful, similar to ''Vesta, Oberon, Wrangell''.
 |-
 ! ''De Baca''{{anchor|De Baca}}
 | {{dts|format=dmy|1958|10|26}} 16:00:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=De Baca|display=inline}}
 | {{sort|001742|}}{{convert|1282|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000022000|2.2&nbsp;kt}}
 | Venting detected, {{convert|380|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 /><ref name=LT_148 />
 | Full yield test, disappointing yield, similar to C''atron'' and ''Mora''.
 |-
 ! ''Chavez''{{anchor|Chavez}}
 | {{dts|format=dmy|1958|10|27}} 14:30:??
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 3u {{coord|37.0443|-116.0305|name=Chavez|display=inline}}
 | {{sort|001241|}}{{convert|1225|m|abbr=on}} + {{convert|16|m|abbr=on}}
 | tower,<br />safety experiment
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000000006|600&nbsp;kg}}
 | Venting detected, {{convert|100|Ci|GBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_163 />
 | 1-point test of device similar to ''De Baca'', failed, fired on wooden tower.
 |-
 ! ''Evans''{{anchor|Evans}}
 | {{dts|format=dmy|1958|10|29}} 00:00:00.15
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12b.04 {{coord|37.19477|-116.20563|name=Evans|display=inline}}
 | {{sort|002025|}}{{convert|2282|m|abbr=on}}–{{convert|256.03|m|abbr=on}}
 | tunnel,<br />weapons development
 | [[W47|XW-47]]  primary Canary ?
 | style="text-align:center;" | {{sort|000000550|55&nbsp;t}}
 | Venting detected on site
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_34 />
 | Full yield test fizzle, similar to ''Blanca''.
 |-
 ! ''Mazama''{{anchor|Mazama}}
 | {{dts|format=dmy|1958|10|29}} 11:20:??
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 9 {{coord|37.12648|-116.04196|name=Mazama|display=inline}}
 | {{sort|001297|}}{{convert|1282|m|abbr=on}} + {{convert|15|m|abbr=on}}
 | tower,<br />weapons development
 |
 | style="text-align:center;" | {{sort|000000000|no yield}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_163 />
 | Fizzle.
 |-
 ! ''Humboldt''{{anchor|Humboldt}}
 | {{dts|format=dmy|1958|10|29}} 14:45:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 3v {{coord|37.0477|-116.0256|name=Humboldt|display=inline}}
 | {{sort|001238|}}{{convert|1228|m|abbr=on}} + {{convert|10|m|abbr=on}}
 | tower,<br />weapons development
 | [[XW-51]] ?
 | style="text-align:center;" | {{sort|000000078|7.8&nbsp;t}}
 | Venting detected, {{convert|1|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | Repeat of ''Hamilton'' with higher yield, extremely small device (16&nbsp;kg).
 |-
 ! ''Santa Fe''{{anchor|Santa Fe}}
 | {{dts|format=dmy|1958|10|30}} 03:00:00.1
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area B7b ~ {{coord|37.0866|-116.0245|name=Santa Fe|display=inline}}
 | {{sort|001742|}}{{convert|1282|m|abbr=on}} + {{convert|460|m|abbr=on}}
 | balloon,<br />weapons development
 | [[W54|XW-54]] Gnat
 | style="text-align:center;" | {{sort|000013000|1.3&nbsp;kt}}
 | Venting detected, {{convert|220|kCi|TBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_6 /><ref name=LT_148 />
 | Similar to devices fired in many preceding shots, yield below predictions.
 |-
 ! ''Ganymede''{{anchor|Ganymede}}
 | {{dts|format=dmy|1958|10|30}} 11:00:??
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area S9g {{coord|37.123|-116.035|name=Ganymede|display=inline}}
 | {{sort|001294|}}{{convert|1294|m|abbr=on}} + 0
 | dry surface,<br />safety experiment
 | [[W45 (nuclear warhead)|W-45]]
 | style="text-align:center;" | {{sort|000000000|no yield}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_163 />
 | 1-point test of W-45/Swan variant, successful.
 |-
 ! ''Blanca''{{anchor|Blanca}}
 | {{dts|format=dmy|1958|10|30}} 15:00:00.15
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area U12e.05 {{coord|37.18589|-116.20289|name=Blanca|display=inline}}
 | {{sort|001913|}}{{convert|2168|m|abbr=on}}–{{convert|254.51|m|abbr=on}}
 | tunnel,<br />weapons development
 | [[W47|XW-47]] primary Canary
 | style="text-align:center;" | {{sort|000220000|22&nbsp;kt}}
 | Venting detected, {{convert|510|Ci|GBq|abbr=on}}
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 /><ref name=LT_34 /><ref name=LT_148 />
 | Test of alternate W-47 primary in TN mockup, successful, similar to ''Evans'', shot vented to atmosphere through the side of the mesa.
 |-
 ! ''Titania''{{anchor|Titania}}
 | {{dts|format=dmy|1958|10|30}} 20:34:00.2
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] Area 8c {{coord|37.1773|-116.0699|name=Titania|display=inline}}
 | {{sort|001353|}}{{convert|1343|m|abbr=on}} + {{convert|10|m|abbr=on}}
 | tower,<br />safety experiment
 | [[W47|XW-47]] primary Canary
 | style="text-align:center;" | {{sort|000000002|200&nbsp;kg}}
 |
 | <ref name=LT_1 /><ref name=LT_150 /><ref name=LT_24 /><ref name=LT_6 />
 | 1-point test of original XW-47 primary, declared safe despite yield, similar to ''HT-I Hickory'' and ''HT-II Neptune''.
 |-
 ! ''Adams''<br>''(canceled)''{{anchor|Adams}}
 | {{dts|format=dmy|1958|10|31}}
 | style="text-align:center;" | PST (–8&nbsp;hrs)|| [[Nevada National Security Site|NTS]] ~ {{coord|37.044|-116.068|name=Adams|display=inline}}
 | {{sort|001220|}}{{convert|1220|m|abbr=on}} + ???
 | Balloon,<br />weapons development
 |
 | style="text-align:center;" | {{sort|000000000|unknown yield}}
 |
 |
 | Test planned for ''Hardtack II'', but held up by atmospherics that would have shattered windows in Las Vegas, and could not be completed in time before start of moratorium negotiations.
 |}
{{Reflist|group=note}}

==References==

{{Reflist|refs=
<ref name=LT_1>{{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}}</ref>
<ref name=LT_24>{{citation| last=Hansen| first=Chuck| year=1995| title=The Swords of Armageddon, Vol. 8| publisher=Chukelea Publications| location=Sunnyvale, CA| isbn=978-0-9791915-1-0}}</ref>
<ref name=LT_150>{{citation| url=http://www.cancer.gov/i131/fallout/Chapter2.pdf| access-date=5 January 2014| title=Estimated exposures and thyroid doses received by the American people from Iodine-131 in fallout following Nevada atmospheric nuclear bomb tests, Chapter 2| publisher=National Cancer Institute| year=1997| archive-date=21 December 2010| archive-url=https://web.archive.org/web/20101221175816/http://www.cancer.gov/i131/fallout/Chapter2.pdf| url-status=dead}}</ref>
<ref name=LT_6>{{citation| publisher=Department of Energy, Nevada Operations Office| date=1 December 2000| title=United States Nuclear Tests: July 1945 through September 1992| type=DOE/NV-209 REV15| location=Las Vegas, NV| url=http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf| access-date=18 December 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=12 October 2006}}</ref>
<ref name=LT_34>{{citation| publisher=Sandia National Laboratories| date=1 July 1994| title=Official list of underground nuclear explosions| url=http://nuclearweaponarchive.org/Usa/Tests/Nevada.html| access-date=18 December 2013}}</ref>
<ref name=LT_148>{{citation| url=http://www.nuclearweaponarchive.org/Usa/Tests| access-date=6 January 2014| last=Sublette| first=Carey| title=Nuclear Weapons Archive}}</ref>
<ref name=LT_163>{{citation| publisher=Defense Nuclear Agency, Department of Defense (Washington, DC)| title=Operation Hardtack II, 1958| type=DNA6026F| url=http://www.dtra.mil/documents/ntpr/factsheets/Operation_HARDTACK_II.pdf| access-date=31 October 2013| archive-url=https://web.archive.org/web/20130218012645/http://www.dtra.mil/documents/ntpr/factsheets/Operation_HARDTACK_II.pdf| archive-date=18 February 2013| url-status=dead}}</ref>
}}

==External links==
* {{Internet Archive short film|id=OperationHARDTACK_BasicEffectsStructuresandMateriel1958|name=Operation HARDTACK Military Effects Studies Part I: Basic Effects Structures and Materiel (1958)}}
* {{Internet Archive short film|id=OperationHARDTACK_UnderwaterTests1958|name=Operation HARDTACK Military Effects Studies Part II: Underwater Tests (1958)}}
* {{Internet Archive short film|id=OperationHARDTACK_HighAltitudeTests1958|name=Operation HARDTACK Military Effects Studies Part III: High Altitude Tests (1958)}}
* {{Internet Archive short film|id=OperationHardtackMilitaryEffectsStudiesPartIv-Sub-kilotonEffects|name=Operation HARDTACK Military Effects Studies: Part IV - Sub-kiloton effects }}

{{US Nuclear Tests}}
{{Authority control}}

[[Category:Explosions in 1958]]
[[Category:Nevada Test Site nuclear explosive tests|Hardtack II]]
[[Category:1958 in military history]]
[[Category:1958 in Nevada]]
[[Category:1958 in the environment]]