Operation Hardtack I

Operation Hardtack I
Hardtack I Oak, an 8.9 megaton explosion.
Information
Country	United States
Test site	Bogallua (Alice), Enewetak Atoll; Eninmen (Tare), Bikini Atoll; Enjebi (Janet), Enewetak Atoll; Johnston Island, Johnston Atoll; Namu (Charlie), Bikini Atoll; Pacific Proving Grounds; Pokon (Irvin), Enewetak Atoll; Runit (Yvonne), Enewetak Atoll; Teiter (Gene), Enewetak Atoll; Yurochi aka Irioj (Dog), Bikini Atoll
Period	1958
Number of tests	35
Test type	air drop, balloon, barge, dry surface, high alt rocket (30–80 km), underwater explosion
Max. yield	9.3 megatons of TNT (39 PJ)
Navigation
Previous test series	Project 58/58A
Next test series	Operation Argus

Operation Hardtack I was a series of 35 nuclear tests conducted by the United States in 1958 at the Pacific Proving Grounds. These tests followed the Project 58/58A series and preceded the Operation Argus series.

Operation Newsreel was a series of three high-altitude nuclear tests conducted as part of Hardtack I. The individual tests in the series were Orange, Teak and Yucca.

Aerial shot of the explosion during Hardtack I Poplar

Tests

See also: List of nuclear weapons tests of the United States

United States' Hardtack I series tests and detonations

Name	Date time (UT)	Local time zone	Location	Elevation + height	Delivery Purpose	Device	Yield	Fallout	References	Notes
Yucca	28 April 1958 02:40:00.3	edst (12 hrs)	Pacific Proving Grounds	0 + 26.21 kilometres (16.29 mi)	balloon, weapon effect	W-25	1.7 kt			ABM development - part of Operation Newsreel (high altitude tests). Fired "about 85 nmi (157 km; 98 mi) northwest of Bikini".
Cactus	5 May 1958 18:15:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	1 m (3 ft 3 in) + 1 m (3 ft 3 in)	dry surface, weapons development	Mk-43 primary	18 kt			LASL test of a MK-43 primary in a thermonuclear system mockup. Similar to Elder. 596 ft (182 m) crater southwest of the Redwing Lacrosse crater; crater later became the Cactus Dome.
Fir	11 May 1958 17:50:00.1	MHT (11 hrs)	Namu (Charlie), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development		1.4 Mt			Clean 2-stage TN device, only 90 kt fission, 93.4% fusion yield.
Butternut	11 May 1958 18:15:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 3 m (9.8 ft)	barge, weapons development	TX-46 primary ?	81 kt			TX-46 primary test, similar to Oak and Yellowwood.
Koa	12 May 1958 18:30:00.1	MHT (11 hrs)	Teiter (Gene), Enewetak Atoll	2 m (6 ft 7 in) + 0.81 m (2 ft 8 in)	dry surface, weapons development	XW-35	1.4 Mt			XW-35 ICBM warhead test.
Wahoo	16 May 1958 01:30:00.5	MHT (11 hrs)	Pokon (Irvin), Enewetak Atoll	0 - 150 m (490 ft)	underwater, weapon effect	Mk-7	9 kt			Mk-7 deep underwater explosion effects, water depth 3,200 ft (980 m).
Holly	20 May 1958 18:30:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 4 m (13 ft)	barge, weapons development	XW-31Y3	5.9 kt			XW-31Y proof test.
Nutmeg	21 May 1958 21:20:00.2	MHT (11 hrs)	Eninmen (Tare), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	early XW-47 ?	25.1 kt			2 stage thermonuclear device, possible W47.
Yellowwood	26 May 1958 02:00:00.1	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 3 m (9.8 ft)	barge, weapons development	TX-46, became W-53	330 kt			LASL developmental test of a "clean" TX-46 warhead design. Fizzled, low burn in secondary. Retry in Oak.
Magnolia	26 May 1958 18:00:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 4 m (13 ft)	barge, weapons development	"Cougar"	57 kt			Proof test.
Tobacco	30 May 1958 02:15:00.2	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 2.7 m (8 ft 10 in)	barge, weapons development	XW-50	11.6 kt			Exploratory shot, XW-50 Nike-Zeus prototype, 2nd stage failed to ignite.
Sycamore	31 May 1958 03:00:00.1	MHT (11 hrs)	Namu (Charlie), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	TX-41	92 kt			"Clean" TX-41 fizzle; predicted yield 5 Mt total, 200 kt fission; low level burning in 2nd stage; similar to Poplar and Pine.
Rose	2 June 1958 18:45:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 4.5 m (15 ft)	barge, weapons development	XW-49 ? Primary	15 kt			Exploratory shot, possible XW-49, 80 kt fusion expected, 2nd stage failed to ignite.
Umbrella	8 June 1958 18:15:00.2	MHT (11 hrs)	Pokon (Irvin), Enewetak Atoll	0 - 50 m (160 ft)	underwater, weapon effect	Mk-7	8 kt			Shallow underwater explosion on lagoon bottom at 150 ft (46 m). Crater 915 m × 6 m (3,002 ft × 20 ft).
Maple	10 June 1958 17:30:00.1	MHT (11 hrs)	Yurochi aka Irioj (Dog), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development		213 kt			"Dirty" 2-stage test, predicted to be 89% fission.
Aspen	14 June 1958 17:30:00.1	MHT (11 hrs)	Namu (Charlie), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	XW-47 ?	319 kt			Possible XW-47 prototype, 2 stage.
Walnut	14 June 1958 18:30:00.1	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 2 m (6 ft 7 in)	barge, weapons development		1.5 Mt			Thermonuclear prototype development test.
Linden	18 June 1958 03:00:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 2.5 m (8 ft 2 in)	barge, weapons development	XW-50 primary ?	11 kt			Possible XW-50 primary.
Redwood	27 June 1958 17:30:00.1	MHT (11 hrs)	Yurochi aka Irioj (Dog), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	XW-47 ?	412 kt			Possible XW-47 prototype, 2-stage, 250 kt fission yield expected; similar to Aspen, Nutmeg, Dogwood devices.
Elder	27 June 1958 18:30:00.1	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 2.7 m (8 ft 10 in)	barge, weapons development	TX-43	880 kt			TX-43 laydown bomb test, 50% fission yield expected, similar to Cactus.
Oak	28 June 1958 19:30:00.1	MHT (11 hrs)	Bogallua (Alice), Enewetak Atoll	0 + 1.8 m (5 ft 11 in)	barge, weapons development	TX-46/53	8.9 Mt			Prototype test of the LASL designed TX-46 system. Similar to Butternut and Yellowwood. Crater 1,750 m × 80 m (5,740 ft × 260 ft).
Hickory	29 June 1958 00:00:00.9	MHT (11 hrs)	Eninmen (Tare), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	XW-47 primary ?	14 kt			Possible XW-47 primary test, similar to Hardtack II Neptune and Titania.
Sequoia	1 July 1958 18:30:00.1	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 2 m (6 ft 7 in)	barge, weapons development	XW-50 primary ?	5.2 kt			Similar to Hardtack II Otero, test of Hardtack I Pisonia primary.
Cedar	2 July 1958 17:30:00.1	MHT (11 hrs)	Namu (Charlie), Bikini Atoll	0 + 3.4 m (11 ft)	barge, weapons development		220 kt			2-stage "clean" thermonuke device, predicted fission yield 30 kt.
Dogwood	5 July 1958 18:30:00.2	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 3 m (9.8 ft)	barge, weapons development	XW-47 ? Piccolo	397 kt			Similar to Redwood, Aspen, Nutmeg; possible XW-47 prototype, Piccolo 2nd stage.
Poplar	12 July 1958 03:30:00.1	MHT (11 hrs)	Namu (Charlie), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	TX-41	9.3 Mt			TX-41 "clean" 2-stage variant; similar to Pine and Sycamore; largest of Hardtack I, and 5th largest U.S. test ever.
Scaevola	14 July 1958 04:00:??	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	2 m (6 ft 7 in) + 6 m (20 ft)	barge, safety experiment	XW-34	no yield			XW-34 1-point safety test, successful.
Pisonia	17 July 1958 23:00:??	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	0 + 2 m (6 ft 7 in)	barge, weapons development	XW-50 ? TN, sequoiah pr	255 kt			Probable prototype XW-50 thermonuclear design, modified Tobacco device, used Sequoia primary.
Juniper	22 July 1958 04:20:00.1	MHT (11 hrs)	Eninmen (Tare), Bikini Atoll	0 + 3 m (9.8 ft)	barge, weapons development	XW-47	65 kt			"Most radical UCRL shot", "entirely new concept", last Bikini atmospheric shot, probable XW-47 candidate.
Olive	22 July 1958 20:30:00.2	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 3 m (9.8 ft)	barge, weapons development		202 kt			Concept feasibility test, 2-stage thermonuclear device, established high yield/light weight; weight 100 kg (220 lb) (yield/weight ratio 2 kt/kg).
Pine	26 July 1958 20:30:00.2	MHT (11 hrs)	Enjebi (Janet), Enewetak Atoll	0 + 3 m (9.8 ft)	barge, weapons development	Mk-41	2 Mt			TX-41 "clean" 3-stage variant; similar to Poplar and Sycamore.
Piñon (canceled)	August 1958	edst (12 hrs)	Pacific Proving Grounds	3 m (9.8 ft) +	air drop, weapon effect		unknown yield			A proposed international demonstration of a clean thermonuke. Cancelled by President Eisenhower in the runup to the 1958 test moratorium.
Teak	1 August 1958 10:50:05.6	jamt (-11 hrs) Believed in use during Dominic, Fishbowl,HT I.	Launch from Johnston Island, Johnston Atoll , elv: 3 + 0 m (9.8 + 0.0 ft); Detonation over Johnston Island, Johnston Atoll	N/A + 81.3 kilometres (50.5 mi)	high alt rocket (30–80 km), weapon effect	W-39	3.8 Mt			ABM effects test. Miscalculation resulted in detonation directly above launch site. Part of Operation Newsreel (high altitude tests), carried on a Redstone rocket.
Quince	6 August 1958 02:15:??	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	1 m (3 ft 3 in) + 1 m (3 ft 3 in)	dry surface, weapons development	XW-51 ?	no yield			Probable XW-51 test, fizzle.
Orange	12 August 1958 10:30:08.6	jamt (-11 hrs) Believed in use during Dominic, Fishbowl,HT I.	Launch from Johnston Island, Johnston Atoll , elv: 3 + 0 m (9.8 + 0.0 ft); Detonation over Johnston Island, Johnston Atoll	N/A + 45.5 kilometres (28.3 mi)	high alt rocket (30–80 km), weapon effect	W39	3.8 Mt			ABM effects test, W-39 warhead, part of Operation Newsreel (high altitude tests), carried on a Redstone rocket.
Fig	18 August 1958 04:00:??	MHT (11 hrs)	Runit (Yvonne), Enewetak Atoll	1 m (3 ft 3 in) + 0.5 m (1 ft 8 in)	dry surface, weapons development	XW-51 ?	20 t			Probable XW-51 test, similar to Quince, successful, last atmospheric shot at Enewetak.

External links

• The short film Operation HARDTACK Military Effects Studies Part I: Basic Effects Structures and Materiel (1958) is available for free download at the Internet Archive.
• The short film Operation HARDTACK Military Effects Studies Part II: Underwater Tests (1958) is available for free download at the Internet Archive.
• The short film Operation HARDTACK Military Effects Studies Part III: High Altitude Tests (1958) is available for free download at the Internet Archive.
• The short film Operation HARDTACK Military Effects Studies: Part IV - Sub-kiloton effects is available for free download at the Internet Archive.