Project 58/58A

{{Short description|Series of 1950s American nuclear tests}}

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

{{Use mdy dates|date=November 2018}}

{{Infobox nuclear weapons test

|name = Project 58/58A

|picture = Coulomb C.gif

|picture_description = Coulomb-C, 0.5 kilotons.

|country = United States

|test_site = {{plainlist|

• NTS Area 12, Rainier Mesa
• NTS, Areas 1–4, 6–10, Yucca Flat}}

|period = 1957–1958

|number_of_tests = 4

|test_type = dry surface, underground shaft, tunnel

|max_yield = {{convert|500|tTNT|lk=in}}

|previous_series = Operation Plumbbob

|next_series = Operation Hardtack I

}}

{{GeoGroup|article=Project 58/58A}}

Operation Project 58/58A was a series of 4 nuclear tests conducted by the United States in 1957–1958 at the Nevada Test Site. These tests followed the Operation Plumbbob series and preceded the Operation Hardtack I series.

All the tests in Project 58 were one-point safety tests.{{cite web |title=Projects 57, 58, and 58A |url=http://nuclearweaponarchive.org/Usa/Tests/Proj57-58.html |work=The Nuclear Weapon Archive}} They were intended to freeze device designs prior to full-scale tests at Operation Hardtack I. No significant yield was expected from either, but the second, Coulomb-C, a surface test conducted on December 9, produced an unanticipated yield of 500 tons. Shortly after detonation, fallout readings of fifty roentgens per hour were recorded on the Mercury Highway, and, as the cloud moved toward the southwest, personnel at Jackass Flats involved in construction for future nuclear rocket testing were forced to take cover. Eventually, the cloud reached the Los Angeles area where readings caused public concern.U.S. Department of Energy, Battlefield of the Cold War, The Nevada Test Site, Volume 1, Atmospheric Nuclear Weapons Testing, 1951-1963, [http://www.freeinfosociety.com/media/pdf/4688.pdf DOE/MA-0003] {{Webarchive|url=https://web.archive.org/web/20120525044108/http://freeinfosociety.com/media/pdf/4688.pdf |date=May 25, 2012 }}

class="wikitable sortable" |+ United States' Project 58+58A series tests and detonations
style="background:#ffdead;" | Name 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. !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. All historical time zone data are derived from here:{{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 + height 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. !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. Purpose Include 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
Pascal-C{{anchor|Pascal-C}} | {{dts|1957|12|6}} 20:15:00.0 | style="text-align:center;" | PST (–8 hrs) || NTS Area U3e {{coord|37.04992
116.03159|name=Pascal-C|display=inline}} | {{sort|001122

}{{convert|1202|m|abbr=on}}–{{convert|80|m|abbr=on}}

| underground shaft,
safety experiment

| XW-42 ?

| style="text-align:center;" | {{sort|000000100|10 t}}

|

|

| One point safety test, partially successful (?).

|-

! Coulomb-C{{anchor|Coulomb-C}}

| {{dts|1957|12|9}} 20:00:??

| style="text-align:center;" | PST (–8 hrs)
|| NTS Area S3i {{coord|37.0443|-116.0305|name=Coulomb-C|display=inline}}

| {{sort|001225|}}{{convert|1225|m|abbr=on}} + 0

| dry surface,
safety experiment

| Moccasin

| style="text-align:center;" | {{sort|000005000|500 t}}

| I-131 venting detected, {{convert|69|kCi|TBq|abbr=on}}

|

| One point safety test, upper bound overtest. Similar to the Moccasin device fired in Hardtack II Hidalgo. Failure, 500 ton explosion.

|-

! Venus{{anchor|Venus}}

| {{dts|1958|2|22}} 01:00:00

| style="text-align:center;" | PST (–8 hrs)
|| NTS Area U12d.01 {{coord|37.19475|-116.20068|name=Venus|display=inline}}

| {{sort|002073|}}{{convert|2104|m|abbr=on}}–{{convert|30.48|m|abbr=on}}

| tunnel,
safety experiment

| XW-47 primary ?

| style="text-align:center;" | {{sort|000000005|500 kg}}

|

|

| One point safety test, partially successful (?). Similar to Hardtack II Oberon and Sanford devices.

|-

! Uranus{{anchor|Uranus}}

| {{dts|1958|3|14}} 22:00:00

| style="text-align:center;" | PST (–8 hrs)
|| NTS Area U12c.01 {{coord|37.193397|-116.20014|name=Uranus|display=inline}}

| {{sort|002033|}}{{convert|2068|m|abbr=on}}–{{convert|34.75|m|abbr=on}}

| tunnel,
safety experiment

| XW-48

| style="text-align:center;" | {{sort|000000005|500 kg}}

|

|

| One point safety test, partially successful (?). Similar to devices fired in Hardtack II Mars, Tamalpais, and Ceres.

|}

{{reflist|group=note}}