Nuclear Weapons Tests on Open Wire



Many of you are familiar with the atmospheric testing of nuclear weapons from 1945 to 1963, and certainly are cognizant of the underground weapons and devices which were exploded in Nevada, Alaska and Colorado.  There was also a long series of very high atmospheric tests above the Pacific Ocean in 1962 using Redstone medium range and Thor intermediate range missile delivery systems. 

Until the Nuclear Test Ban Treaty was signed between the Soviets and the Americans in 1963, these tests were conducted in a multiplicity of situations by the A.E.C, the U. S. Air Force, the U. S. Army, the U. S. Navy and in conjunction with some foreign allies.  Some weapons/devices were perched on towers, others exploded underwater, others dropped from planes or suspended by dirigibles or balloons or sent aloft by missiles and launched from ships as depth charges and then detonated.

The largest number of these tests were accomplished as science experiments, other to modify the explosive power of the nuclear weaponry or to test various improved theories in nuclear physics.

However, while the vast majority of these tests were primarily “military” in nature, there were a number of dedicated tests which were “civil” in nature.  That is, primary weapon tests were “civil effects tests” by subjecting various metal, concrete and wooden structures, network architecture such as natural and petroleum gas pipelines, compressor or filling stations as well as electric power and street lighting equipment, to the explosive force of a fission weapon.

One very important civil effects test conducted by the Atomic Energy Commission was Operation Doorstep in 1953, where various frame houses revealed their inadequacies in construction by increasing degrees of damage and destruction following a nuclear test in Nevada.  The results of damage were analyzed post-test to determine personnel survival during a real war-event and whether bodily damage by improved construction techniques might be predicted. 

Building upon that limited structural analysis was the Operation Cue, Shot Apple II test which subjected a wider range of structures to the tremendous power of a 25 kt fission weapon at the Nevada Test Site (N.T.S.) on May 5, 1955.   The five-fifty-five test was carried out with various American construction organizations and utility industry participants.  Most notably for our discussion here, the Edison Electric Institute.  They represented the Investor-owned electric utilities.   Two “doom towns” were constructed at 4,700 foot  and 10,500 foot distances from the shot tower perched 500 feet above the desert floor at the N.T.S.  These ‘towns’ comprised housing of various types, warehouse and industrial buildings, as well as a small electric utility setting comprising two single main bus substations at each distances from the shot tower,  two short 69-kV flexible tower transmission lines feeding the sub as well as distribution feeders radiating from the sub carrying electric distribution services on wooden poles.  These were both the 11-kVY/6.6-kV single phase and 5-kV under build voltage levels.  Open wire power distribution and aerial power cable lashed to a messenger were part of the setup.  Southern California Edison was a substantial player in these tests, having donated much of the equipment, including several utility trucks parked along side the sub and distribution lines.  Secondaries were also carried on spreader brackets and drops to the houses were included.

The results were dramatic post shot.  In the final analysis, the aftermath of the test revealed damage to the electric system was that what could be expected during a major hurricane or tornado event and was repairable, with the exception of automatic operation components.

What many people may not be aware was the susceptibility of aerial wire to a nuclear weapons explosion was learned over the 1945-1955 period in three similar situations.  One unintended and the other two intended subjecting of such equipment to blast effects.

The first was the unwitting and unexpected failure of some recording instruments and cameras during the “Trinity” July 16, 1945 initial test of a nuclear device in New Mexico.  Strung out from the observation post were many aerial wire (twisted field wire) lines to the various instruments planted about the test area whereby results on the power and duration of the world’s first nuclear explosion might be recorded.  Unfortunately, these failures of equipment were due to the surprising power of electromagnetic pulse, the plasma event which accompanied the explosion at the top of the 100 foot tower.  This pulse knocked out considerable instrumentation which might have rendered the results more effective.  Yet much was learned from that initial experiment to prevent similar situations from occurring in the future.  In effect, this “blinding” the eyes of the instrumentation in many locations could be prevented if sufficient precautions were taken by future nuclear test administrators.

The second was the use of “Doom Towns” as spoken about in the earlier part of our discussion above.

The third nuclear experiment subjected communications equipment to the blast of a fission weapon in two separate tests: May 19, 1953 (Shot 9) and June 4, 1953 (Shot 10).   It is my pleasure to bring some unique, fascinating and little known facts to your attention regarding this event and how it impacted open wire telecommunications equipment operation.  The event was named “Harry,” the ninth in a series of weapons tests collectively recognized as “Operation UPSHOT KNOTHOLE,” carried out as part of this 1953 series when a 32-kiloton fission weapon was donated atop a 300-foot tower.

 Upshot Knothole Preliminary Discussion

The Nevada Proving Ground, or Nevada Test Site (N.T.S.), was the site of this ninth series of atmospheric tests conducted from March 17 to June 20, 1953.  This series is well known for two particular reasons, outside of our important discussion of tactical communications systems’ affected by such bursts: a) one test (“Grable”) was delivered via a gun-type enriched uranium artillery shell targeted by a 280 mm atomic cannon and, b) our discussion’s  test, “Harry,” having delivered the heaviest and most concentrated fallout contamination of geography downwind of the N.T.S., than any nuclear test ever carried out in the contiguous United States.  One report stated that a  total of 30,000 person-roentgens (p-r) of external gamma ray exposure occurred from the Harry shot alone.  Considering that this amount was derived from a sum total of 85,000 p-r  delivered during the same period up until 1958 was truly mind-boggling.

This series of tests also highlighted the largest Department of Defense involvement of any nuclear experiment, which included “Exercise Desert Rock V.”  “The Nuclear Battlefield” concept placed troops within test theaters for both tactical maneuvers, helicopter operations, officer observer programs, troop orientation, training and military vehicles and equipment damage effects.  The total number of military participating was 20,100.  These involved not only armed forces personnel actively engaged in troop maneuvers, but scientific and support activities carried on before, during and post-test.  Part of these tests’ objectives included civil defense participation so the amount of damaged sustained by civilian structures and food stuffs.  The Sixth Army contributed 2,000 troops which were activated to provide support services such as radiation safety, communications, medical care, transportation, security and construction requirements for the event.  Several other personnel complements included, for our relevant discussion here, men from the 505th Signal Service Group (Composite Company) and the 412th Engineer Construction Battalion who assembled the facilities and placed the equipment in service for the test.  2,000 U. S. Air Force personnel also attended to the shot’s preparation, including a Weather Reconnaissance Squadron and various Indian Springs AFB and Kirtland AFB Test Groups (Atomic).  The U. S. Marine Corps Provisional Atomic Exercise Brigade also played a significant role where the Helicopter Atomic Test Unit utilized three helicopters and ten Marines.  A number of troops from foxholes and trenches were subsequently airlifted after the explosion to a site 1.2 miles south of ground zero, after which, the aircraft proceeded to an anti-contamination station. 

Those interested in the full history of the Upshot-Knothole nuclear test series is invited to research the project further elsewhere, as it is an interesting series of tests.   However, for our discussion, let’s proceed to the ninth in the series, “Harry Shot,” which featured the effects of nuclear weapons on communications systems.

Preparations for “‘Dirty’ Harry” (Shot 9) 


The objective of the project was, “. . . subject selected signal communications-electronics items of equipment and material to air burst atomic weapons to determine the effects thereon. . . the effects data obtained, together with data made available from other atomic tests, may be used in the preparation of a suitable guide for Signal and Communications Officers in planning tactical and non-tactical communications installations and facilities in atomic warfare.”

Below is a diagram of the facilities constructed for Shot Harry, which included single pole aerial wire, cable and various terminal and guyed structures.


The inadequacies of previous tests involving communications equipment were clearly obvious, as these had been installed on board ships (during the Bikini tests) and did not represent qualification as “tactical” in nature.  The nuclear detonations above Hiroshima and Nagasaki failed to return adequate information where telecommunications equipment was concerned and hence, the air burst effects of nuclear weapons on communications equipment was greatly lacking.  Thus, the need for specialized experiments using tactical telecommunications, radio and field telephone equipment was essential.  The Engineering and Technical Division, Office of the Chief Signal Officer, the Signal Corps Engineering Laboratories and other interested agencies began to investigate the forthcoming Upshot Knothole series of atmospheric tests as a means to secure adequate information.

The damage correlation was achieved by the following definitions:

  • Severe Damage: Damage severe enough to completely prevent the military function and subsequent repair of the lines unless they were completely rebuilt by a major repair process.
  • Moderate Damage: Sufficient to prevent military use until extensive repairs were affected.
  • Light Damage: Injury which would not seriously interfere with immediate military operation, but some restoration necessary to achieve usefulness.
  • Negligible Damage: No repairable needs.

The Harry Shot was sponsored by the Los Alamos National Laboratories and fired at 5:05 a.m. from a 300 foot tower with a yield of 32-kilotons.

Eight Signal Corps Engineering Laboratories personnel, including the project officer and assistant project officer, were assigned and worked out of the Camp Mercury, Nevada field outpost.  To construct, from the designs suggested by the Laboratories’ engineers, were a component of the Corps, the 16th Signal Battalion, Detachment A.  

High speed photography was used to record the damage inflicted on various elements used in the experiment.  Because desert dust posed a problem and might impede proper photographic clarity, a stabilizing light concrete coating on the surface of the desert floor was spread in several areas and would have been used throughout the test area, had not the budget  been expended prior to the test date.  The planned date of the test was May 2, 1953, however, actual shot date occurred on May 19th, 5:05 am local Nevada time, owing to meteorological conditions.  At the time, this 32-kiloton explosion utilized the most efficient use of fissionable materials in a bomb or device detonated up to that time.  

The general equipment and line material categories subjected to this test were divided as following:

Wire: Pole line, aerial cable, aerial un-insulated conductor, teletype, switchboards and telephone sets

Radio: Vehicular radio, fixed plant and mobile radio teletype

Mechanical: Radio antennas and towers

General Engineering: Shelters and huts as well as “miscellaneous” materials such as manholes, ducts and hand holes.

Relevant to our topic is “Wire” here, and we will discuss this in depth.  


Planning began with the determining of both thermal energy and peak over-pressure demands expected from the test.  However, when the Signal Corps began to design the range site and procure equipment for the forthcoming projected test, the Los Alamos Laboratory had not yet determined the expected yield or height of burst to be demonstrated as Shot Ten.  This left Signal Corps engineering personnel to calculate their plan based upon an assumed weapon capable of a 30-kiloton yield and 2400 foot air burst height.

Several open wire and cable-carrying pole lines were designed to determine “radial thrust and banding” effects.  Transverse loaded pole lines were designed to differ from the radial-situated lines so that their behavior under high speed cameras could be recorded and covered in order to determine differing effects encountered.

Both guyed and un-guyed poles were used.  Some poles were naked.  Rather pole lines were built without crossarms, cables attached and wire to differentiate between fully “loaded” lines with all equipment and line materials attached and varying effects between them.

Plan of Project 

Below is illustrated, from a film made of the test program, the pole line, cables and test area with the various radial and transverse pole lines incorporating the test project.  The photos available from the test report on microfilm were so poor that even these photographs made from the test film are superior to the report illustrations.

The radial pole line incorporating a single ten foot arm, with 30-inch steel span braces, wooden pins, glass insulators and drop brackets used for transpositions were built.  This line began 9,080 feet north east of ground zero (GZ) and extended directly straight 1,250 foot beyond.  

There were 52 standard creosoted Southern Yellow Pine 30′ class 7 poles at 150-foot spacing set five and one half feet in the soil.  These were well  tamped following their mechanical setting by an earth auger.  Poles numbered D-14, D-28, D-41 (6950′, 4750′ and 2900′ from GZ) were four-way storm guyed.  Termination poles were located a 9080 and 1250 feet and dead-ended with triple guying.  


The crossarms carrying open wire were W-10 type carrying eight each of No. 104 Copperweld conductors.  The transposition system was designed for a “C” carrier with drop brackets.  Slung below the crossarm assemblies was one 26-pair, lead-covered cable lashed to a W-115 strand with 0.045-inch diameter, stainless steel lashing wire; one five pair, rubber cable (CX-162/G) lashed to a W-115 strand with 0.045-inch diameter lashing wire; one spiral four cable (CX-1065/G) self-supporting; and from 1 to 11 WD-1/TT field wires (only one pair of field wires ran the entire length of the pole line).

The line was transposed for a Type “C” carrier, using standard drop brackets.  

In the photo above, you’ll wonder what the rectangular equipment represented on the horizontal member above.  These were field telephones which allowed testing of the open wire and cable post-test.

The Post-Test Results

The pole lines received varying damage depending upon the distance from the shot.  

The  most distant open wire from ground zero exhibited negligible impairment, and was considered “lightly damaged.”  For example, poles experienced thermal damage with light surface charring of those faces cast towards the explosion center.  Crossarms also illustrated similar charring at this 1,250 level.  The overpressures exacted from the impact of the explosion was 16.6 p.s.i.  This powerful wind twisted the arms slightly but were serviceable and did not impede the operation of the line.

Insulator pins were undamaged, as were most toll insulators used on the construction, with the exception of two broken ones at the 1,400 foot distance.  What was most important was the tie wires and conductor were not separated from the insulator ruin and yet were serviceable post-shot.

Where the guys and anchors were afixed to the terminal poles and storm guyed installations along the route, damage was hardly noticeable.  Tension on anchors and guys remained as when installed pre-test.

These minor damages above did not degrade the operation of the open wire, as the 104 Copperweld did not separate from the poles, and despite the contact of a burned WD-1/TT wire and barbed wire from a land mine fence blown across the aerial wire, removal of this debris allowed the open wire to be operated smoothly, thus any shorts were eliminated.

Where the 26-pair lead sheathed cable was concerned, the only damage the length of the pole line was minimal–where at the 1,250-2,000 foot level, the last six poles saw the lead sheath rupture and separate from the strand.  When tested, only one pair was found to be “defective” and the paper-covered conductors were heated up and operable post-shot.  However, if moisture, in the form of rain, sleet or wet snow had occurred after the event, it was clear this cable would fail if immediate repairs were not made.

Some superficial burning, in the form of slight blackening and roughening due to the heat energy exacted by the detonation, could be discerned where the five-pair rubber covered cable (CX-162/G) type was affixed to the lashing wire.  Between two poles at the 1,250 and 2,750 foot levels, lashing wire was broken.  Here, the cable sagged, but did not break below the overhead strand.  There was also some blackening of the rubber jacket on the spiral four cable (CX-1065/G) type.  There were cracks in the sheath due to the thermal effects of the detonation.

Field wire, correlating to “bridle wire,” a soft annealed copper, was installed at several locations along the pole line.  This wire was affected more drastically than the open wire and cable installations because of heat.  Bare conductor was blackened and some melting of the insulation of the wire was evident.

Cable transfer relays were installed on poles at the 1,250 and 2,750 foot levels.  Since the cable emerged from the ground where manholes and hand holes were placed in order to transition to the open wire connections above, the relays were expected to have some damage.  They did not experience any damage.  However, the lead sheath on the riser cables melted for several inches and paper-insulated pairs were burned, but not mechanically damaged or dislodged. The relays were found to be usable.  One cable transfer relay was manhole mounted and did not see damage from the blast.  

Junction terminals and their enclosures were metal and did not dislodge, experience damage or fail to function when re-energized.   

In brief, Shot 9, did not inflict serious damage upon the pole line to a significant degree furthest from the shot tower. 

Below is a photo still from the film which captures the instant when the terminal structure with double buck arms, three guys, terminals and anchors, was hit by the precursor blast wave.  Smoke was the result of the thermal wave bouncing against the wooden structure and momentarily creating a charring effect.


However, those structures closer to the shot’s main blow, received significant injury.  Here are some of the effects noted where section poles lay from 600′ to around 2900′ from the blast:

“The pole line as a whole received severe damage from pole D-52 out to, and including pole D-37.  In this section of the line 16 poles were splintered at the base of the poles, broken or disintegrated into one or more pieces and blown about the area along the pole line.  There was a miscellaneous conglomeration of crossarms, pins, insulators, open wire, lead covered cable, rubber covered cable, spiral four cable, and field wire snarled together along this section of the pole line.  The degree of severe damage stopped abruptly at pole D-36,” quoted the report no. AD-357977.  In summation, the report revealed the following effects delivered to the Lateral Pole Line, quoting:

  1. Crossarms: All crossarms from pole D-52 through pole D-37 were ripped from the poles or broken by impact by the ground.  Many of the crossarms were broken and thrown as much as 450 ft. from their original positions.  There was slight thermal burning on all crossarms which decreased in intensity out to the distant end of the pole line.
  2. Insulator pins: Pins from pole D-52 through D-37 received severe damage.  No insulator pins were damaged from pole D-36 through pole D-1.
  3. Glass insulators: All glass insulators were either melted, broken or blown about the area from pole D-52 through pole D-37.  Insulators on poles fro D-36 through D-1 received varying degrees of thermal damage causing them to darken.  The extent of this darkening diminished toward the distant end of the line.  No tests were made to determine whether or not this darkening affected their insulation properties.
  4. Guys and anchors: The triple dead-end guys on pole D-52 and the four-way storm guys on Pole D-41 were twisted and on the ground at their original positions.  The back guys on poles D-28, D-14 and the triple guys on pole D-1 were slightly loosened.  The side and front guys on pole D-1 were taut.  The anchor rods for poles D-52 and D-41 were slightly protruded but otherwise in the ground.
  5. Open wire: The 104 CS wires between poles D-52 and D-37 were broken and snarled up in the vicinity of the pole line and received severe damage.  From pole D-36 to pole D-1, the open wire was blackened and abnormally sagged.  The clearance at transposition crossovers was reduced considerably, and high winds would have caused intermittent short circuits.  The open wire circuits would have been operable subsequent to minor repairs to this portion of the pole line.
  6.  26 pair lead covered cable: From pole D-52 through pole D-37, the lead covered cable was melted, broken and snarled up on the ground in the vicinity of the pole line and received severe damage.  From pole D-36 to pole D-1, there was slight scorching and roughening of the cable decreasing in intensity toward the distant end of the pole line.  This cable showed considerable darkening under the suspension clamps from pole D-36 to pole D-1.  The cable splices showed no apparent damage.  The lashing wire and messenger (strand) wire were intact from poles D-36 through D-1.  This cable would have been operable in the section of the line from poles D-36 through D-1.  
  7. 5 pair rubber covered cable: this cable was burned, broken and snarled uip on the ground between pole D-52 and D-37, receiving severe damage.  From pole D-36 to pole D-1, there was scorching and roughening of the cable, and darkening under the suspension clamps, decreasing in intensity toward the far end of the line.
  8. Junctions and Terminals: The junction boxes and terminal strips between poles D-52 and poles D-37 were either broken or blown about the area.  Some of these items could not be found after the shot.
  9. Field telephones: Due to the distance located from the shot, these instruments at 8,350 feet received any damage and were operable.

Regarding the Transverse Pole Line, which was 1,050 feet in length, 3,425 feet from ground zero, these effects were measured and observed.

  1. Poles: All eight poles C-1 through C-8 were broken off and thrown to the ground.  Poles C-1 and C-8, poles which were triple guyed, were broken off about six feet from the surface.  Poles C-2 through C-7 were broken off at the surface.  All poles received severe damage.
  2. Crossarms: Several of the crossarms were broken in half at the center and several appeared to be serviceable.
  3. Insulator pins: A number of the insulator pins were pulled out of the crossarm.  Those pins remaining in the crossarms were serviceable.
  4. Glass insulators: Several of the glass insulators were broken.  Those not broken were serviceable.
  5. Guys and anchors: The triple guys on the two and poles and the anchors were intact and serviceable.
  6. Open wire: The 104 CS wires although bunched together on the ground were not broken and all would have been usable.
  7. 26 pair lead covered cable: This cable was broken in several places and lying on the ground.  It remained attached to the messenger (strand) on pole.  It received severe damage.
  8. 5 pair rubber covered cable: This cable was broken in several places and lying on the ground still attached to the messenger on the poles.  It received severe damage.
  9. Junctions and terminals: These items sustained no apparent thermal or blast damage.
  10. Field telephones: The field telephones on poles C-1 and C-8 were shielded from the thermal flux and received no significant thermal or blast damage.

Let’s move on to the second burst of a fission weapon–made distinctive by the delivery of the weapon by nuclear cannon and as the second use in American nuclear weapons development by uranium “gun type” weaponry.

Shot 10: ‘Grable’

atomic_annie02Photo Credit: U. S. Department of Defense.  May 25, 1953 first delivery of nuclear weapon by artillery canon.

 Let’s discuss the Grable test of Operation Upshot-Knothole where major damage was inflicted upon the open wire and aerial cable installations.  It occurred at the N.T.S. detonation site at 8:30 am, May 25th, 1953, demonstrated by 15-kiloton yield gun-type uranium fission weapon exploded  524 feet above the desert.  This test was sponsored by the Department of Defense and the Los Alamos National Laboratories.

Below is a plan of the project, re-using many of the original Shot 9 pole line materials left undamaged by the first shot