History Magazine > 1998
(Click above for larger image)
The Story of the War of 1898
Was it an explosion from a coal-dust fire, or was it a mine? This
reportfrom a study commissioned by National
Geographic magazineprovides compelling evidence.
After a period of uneasy peace, Cuban rebels
in 1895 renewed their struggle against the Spanish rulers of the island. To quell
this latest insurrection, Spain sent General Valeriano Weyler, who forced thousands
of Cubans into concentration camps. Joseph Pulitzer's New York World and
William Randolph Hearst's New York Journal thundered with demands for U.S.
intervention to aid the Cuban guerrillas. The sensationalist newspapers dubbed
Weyler "the Butcher" and published storiessome true, some notabout
his atrocities against Cubans. Spain, reacting to U.S. loathing of Weyler, removed
him, temporarily easing tension between the two nations. But in January 1898,
anti-American rioting broke out, and U.S. Consul Fitzhugh Lee (nephew of Confederate
General Robert E. Lee and himself a Major General in the Confederate Army) urged
official Washington to protect the lives of U.S. citizens on the volatile island.
President William McKinley ordered the Maine to Cuba.
On 25 January 1898, the battleship steamed into Havana Harbor. McKinley, trying
to still the war drums, wanted the Maine to show the flag, prove that U.S.
warships had the right to enter Havana, and then get out. On 15 February the Maine
was to head for New Orleans in time for Mardi Gras. By then, McKinley hoped, anti-Spain
fervor should have died down.
But at 2140 on the night of 15 February, a massive explosion tore through the
ship, killing 250 men and two officers. (Mortal injuries raised the final toll
A Court of Inquiry questioned survivorsincluding commanding officer Captain
Charles D. Sigsbeeand interpreted the reports of divers. The theory that
a mine had destroyed the ship stemmed primarily from eyewitness testimony. The
report of diver W. H. F. Schluter was particularly significant. He said he could
see green paint on a bottom plate that was "all torn ragged and it looked to be
inward." Bottom plates on the outside were painted with antifouling green paint.
So this produced the image of a plate being blasted from the outside and turned
"You are sure they were not bent out?" the court asked Schluter.
"Yes, sir; I am sure," he replied.
"And the green paint you saw was on the part bent inward?"
"The green paint was on the part bent inboard. . . . My opinion is, I believe
that she was blown up from the outside and in, because there was no explosion
from the inside [that] could make a hole like that, from the way them plates stood
around in different directions." The Court concluded that the extensive damage
"could have been produced only by the explosion of a mine." But it was "unable
to obtain evidence fixing the responsibility . . . upon any person or persons."
After the court's finding was revealed in March, McKinley no longer could ignore
the call for war. "Remember the Maine and the hell with Spain" became a
But was it a mine?
The question lingered until 1911, after the U.S. Corps of Engineers, in an
unprecedented feat, built a cofferdam around the ship, pumped out the water, and
exposed the wreckage. A Board of Inquiry based much of its analysis on photographs
of physical evidence that the previous investigation had sensed but not seen:
bottom plates that were bent inward, presumably by an external force, such as
a mine. The board focused on a section of outside plating that "was displaced
inward and aft and crumpled in numerous folds."
Although the 1911 report placed the location of the explosion farther aft,
the 1911 inquiry's conclusion agreed with that of 1898: "The board believes that
the condition of the wreckage . . . can be accounted for by the action of gases
of low explosives such as the black and brown powders with which the forward magazine
were stored. The protective deck and hull of the ship formed a closed chamber
in which the gases were generated and partially expanded before rupture."
The question disappeared. Historians writing after 1911 took for granted that
someoneSpanish sympathizers, perhaps, or disgruntled guerrillas hoping to
goad the United States into warhad set a mine that blew up the Maine.
After reading a newspaper story in 1974 about the sinking of the Maine,
Admiral Hyman G. Rickover decided to reexamine the issue. He recruited historians,
archivists, and two Navy experts on ship design: Robert S. Price, a research physicist
at the Naval Surface Weapons Center at White Oak, Maryland, and Ib S. Hansen,
assistant for design applications in the Structures Department at the David W.
Taylor Naval Ship Research and Development Center at Cabin John, Maryland. Among
Price's Navy projects had been an analysis of the wreckage of the nuclear-propelled
submarine Scorpion (SSN-589), which was lost in May 1968.1
The Hansen-Price analysis, as Rickover called it, was the heart of a short
book published in 1976.2 The 23-page
analysis reached this conclusion: "We found no technical evidence . . . that an
external explosion initiated the destruction of the Maine. The available
evidence is consistent with an internal explosion alone. We therefore conclude
that an internal source was the cause of the explosion. The most likely source
was heat from a fire in a coal bunker adjacent to the 6-inch reserve magazine.
However, since there is no way of proving this, other internal causes cannot be
eliminated as possibilities."
Again, historians rallied around the Rickover solution, and after 1976 most
discussions of the Spanish-American War concluded that there was no mine.
As the 100th anniversary of the sinking of the Maine approached, David
W. Wooddell, senior researcher on the editorial planning council of National
Geographic magazine, suggested that the magazine commission an analysis of
the disaster based on computer modeling not available to Rickover and his team.
Advanced Marine Enterprises (AME), a marine engineering firm often used by the
U.S. Navy, accepted the mission.
The AME analysis, which was announced in the February 1998 issue of National
Geographic, examined both the mine and the coal bunker theories. The report
declared that "it appears more probable, than was previously concluded, that a
mine caused the inward bent bottom structure and detonation of the magazines."
Some experts, including Rickover's researcher Hansen and respected analysts
in AME itself, do not accept the conclusions of the AME report. Following are
excerpts, published in cooperation with National Geographic, to give readers
a chance to judge for themselves.
back to top
Carrying large quantities of coal on board was a source of constant hazards
for ships of the time, and even today. Coaling operations inevitably left a ship
covered with a layer of fine, black dust, creating a fire hazard and the potential
for a coal dust explosion. However, a thorough cleaning would significantly reduce
the risk of sufficient coal dust collecting on deck. Fires inside the coal bunkers
were recognized as a constant hazard. Coal will naturally oxidize when exposed
to air, producing heat. If this heat is not dissipated, it will feed the reaction,
causing it to accelerate. Typically, the rate of the reaction will double for
every 15-20F increase in temperature.3
As the temperature reaches 750-800F, incipient combustion
occurs, followed ultimately by self ignition and flame.4
A higher moisture content in the coal will increase this heating
tendency.5 Once one of these fires
is started, it can be difficult to extinguish, often requiring emptying of the
bunker to ensure removal of hot spots. The Titanic had a fire burning in
one of her coal bunkers when she left Belfast for Southampton, prior to her fateful
voyage. Stokers worked for several days to extinguish the blaze, and plans had
been made to have the New York City Fire Department meet the ship upon its arrival
in New York.6
There are various ways of storing coal while minimizing the risk of spontaneous
combustion. One method, widely used in modern coal-burning facilities, is simply
to use the coal before any appreciable heating can occur.7
Another is to compact the coal when it is stacked, thereby minimizing
the amount of air which can flow through the stack, and depriving any potential
fires of oxygen. If the coal cannot be compressed, then limiting the size of the
stack can help allow sufficient air flow to dissipate the heat.8
Stowing different sizes of coal together should be avoided.
The finer pieces, which are more prone to react due to their increased surface
area relative to their weight, will tend to collect near the bottom of the stack,
while the larger lumps allow air to circulate through the pile.9
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The "mine explosion" locations concluded by reports filed in
1898 and 1911 were at Frame 18 and near Frame 30. The 1975 study sponsored by
Admiral Hyman Rickover, however, concluded that the sinking was not caused by
a mine explosion at all, but rather, the spontaneous combustion and "heat transfer"
from coal dust.
One common way of detecting a coal fire is by seeing or smelling the vapor
associated with the reaction. Another, less subjective method is to insert probes
into the stack, looking for potential hot spots. However, temperatures within
the stack can vary, so several probes are necessary, and there is no guarantee
that all hot spots will be detected.10
Conditions on the Maine were far from ideal for preventing spontaneous
combustion. The coal bunkers had last been filled with bituminous coal in November
, and the ship had spent most of the last three months at anchorage in Key
West, Florida.11 The tall,
narrow shape of the coal bunkers would have made it difficult to compress the
coal to eliminate air flow, however, it would easily allow fine particles to collect
at the bottom of the bunker, where hot spots would be most difficult to detect.
With no means of forced ventilation, the small vent for the bunker could not have
allowed sufficient excess air flow to dissipate additional heat, and the omnipresent
moisture of the tropics would have ensured that the coal was moist. The forwardmost
bunkers, immediately outboard of the 6-inch Reserve Magazine on the port side
and the 10-inch Handling Room on the starboard side, were among the last to be
emptied, so they were full, with over 37 tons of coal in the port bunker and over
24 tons in the starboard bunker.
To examine the heat-transfer theory, the AME team made a computer model
to evaluate "the effects of a coal fire in the bunker immediately outboard of
the 6-inch Reserve Magazine." The heat-transfer study was based on the following
- All heat transfer occurs through the steel, since steel is much more conductive
- Only the plating of the decks, frames and bulkheads was effective in transferring
heat. Plating stiffeners had an insignificant effect on the thermodynamics and
were therefore not modeled.
- Heat transfer to spaces above the protective deck was considered negligible,
due to the layer of wood laid down upon the deck, which would have insulated the
spaces above from the deck below.
- The structure on starboard side, aft of Frame 30, and forward of Frame 24
has minimal impact on the analysis as it is relatively far from the heat source.
- The shell plate acts as a heat sink, being in contact with the water. The
shell plate was not included in the model. Instead, boundary conditions were placed
at the edges of the floors and girders, where they attach to the shell plate,
and were set to a constant temperature of 80.
- Heat transfer by convection was negligible, because the vent was so small
and no forced ventilation existed.
- The initial temperature for a majority of the structure is assumed to be 80.
The initial temperature within the 6-inch Reserve Magazine and within the Coal
Bunker is assumed to be 100. This is considered to be conservative. A higher
initial temperature would permit the temperature within the magazine to reach
a critical value sooner.
- The temperature input (load) is assumed to be a constant temperature of 1000F.
This is considered to be a low (conservative) value for the assumed temperature
of the bulkhead close to a coal fire. A higher input temperature would result
in temperatures within the magazine reaching a critical value sooner.
- The 6-inch Reserve Magazine contains black powder, it is properly stowed and
is therefore within 4 inches of the bulkhead.
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The Coal Bunker Theory A assumes the collapse of inner bottom
grillage before the inner bottom and shell plating exceeded elastic limits. Despite
the contrary tenor of the recently conducted study, some prominent officials within
the AME organization are clinging to this theory-Admiral Rickover's-as the cause
of the ship's sinking.
The fire itself was modeled as a constant temperature source (1,000F)
applied to the bulkhead between the Coal Bunker and the 6-inch Reserve Magazine
at Frame 27, at a point just above the deck. The assumed temperature is within
the range of temperatures at which coal burns and is thought to be reasonable
for a local area of combustion with a restricted air supply. It was assumed that
the fire would have to be burning close to the bulkhead, or the surrounding coal
would have helped to insulate it. The thermal energy from the constant temperature
was assumed to be dissipated throughout the plating, the air in the 6-inch Reserve
Magazine, and eventually through the frames into the sea. The outermost edge of
each frame, where they would meet the shell plating, served as a constant temperature
heat sink, maintaining the same temperature as the water (80F).
Next, the AME team made a transient heat-transfer analysis to determine "how
quickly the air in the 6-inch Reserve Magazine could attain temperatures required
The shell was considered to act as a heat sink, with a constant temperature
of 80F (below the waterline). The edges of the floors and girders are set
to 80F. The load applied to the bulkhead is a constant temperature of 1000F
over an area approximately 12 inches by 12 inches. The constant temperature is
applied at Frame 27 (middle of the 6-inch Reserve Magazine) on the longitudinal
bulkhead between the coal bunker and the magazine, centered 18 inches above the
innerbottom. . . .
(Click above for larger image)
The transient analysis indicated that within four hours, temperatures 12 inches
off the bulkhead would have reached almost 395F, and six inches off the
bulkhead the temperatures would have been in excess of 645F. Meanwhile,
the deck above would barely have begun to warm up. After six hours, temperatures
12 inches off the bulkhead would have been approaching 420F, and six inches
off the bulkhead the temperatures would exceed 660F. This is well above
the temperature required for combustion for the location of the canisters, four
inches off the bulkhead. However, the platform deck above would be heated only
to about 167F, and a thermometer on the far side of the room would barely
have begun to register the temperature increase.
The protective deck and the bulkheads at Frames 24 and 30 were chosen as areas
where increased temperatures might be observed by the crew. The maximum temperature
within these areas occurred in the protective deck, immediately above the applied
heat source. The maximum temperature of the protective deck was predicted to be:
88 after 4 hours, and 95 after 24 hours.
The analysis was run again, this time with a source temperature of only 800F,
and similar results were obtained.
The finite element analysis indicated that a coal fire burning close to the
bulkhead could have raised the temperature of powder stowed in the 6-inch Reserve
Magazine, close to the bulkhead, to the point of being hazardous in only a few
hours. This is significant, since testimony [at the 1898 inquiry immediately after
the sinking] indicated that routine checks had been made of the temperatures in
the magazines, however, there were intervals of several hours between these routine
The testimony provided at the first inquiry is sometimes contradictory as to
contents of the 6-inch Reserve Magazine, however, all agree that some form of
powder was stowed in this space, probably black powder for saluting. The testimony
indicates that it was properly stowed, which suggests that it was stowed in copper
canisters on the wooden racks. Any canister stowed in the rack against the bulkhead
between the coal bunker and the magazine could have been heated to several hundred
degrees, hot enough to cause the powder to explode. If any of these canisters
were in direct contact with the steel bulkhead, they would have heated much more
The results of the finite element analysis cannot be considered conclusive,
as there is no direct evidence supporting several assumptions included in the
analysis. There is no evidence concerning exactly how and where powder was stowed
in the 6-inch Magazine. There is no evidence that a coal fire was burning in the
coal bunker. Even if there were a fire, there is no guarantee that it would have
been close enough to the bulkhead to heat the magazine. Any such fire presumably
would have started from a hot spot that previously had gone undetected. The heat
buildup in the magazine could not have been in progress for more than a few hours
prior to the last temperature check on the magazine. However, the analysis does
indicate that if a hot spot went undetected in the bunker close to the magazine
bulkhead, this hot spot could have developed into a fire. And if powder were stowed
in the magazine, close to the same bulkhead, the powder would have been heated
enough to explode. And all this could have occurred without the routine watch
having noticed a temperature increase. While there is no direct evidence proving
that a coal fire led to the explosion that destroyed the ship, the available evidence,
combined with the results of the analysis, indicates that a coal fire could have
been the first step in the Maine's destruction.
After the analysis of the heat-transfer, or coal-fire, cause for the destruction
of the Maine, the report takes up the possibility that a mine could have
been the cause. Using modern analytical techniques, the AME analysts conducted
damage assessments based on:
- Damage from a small mine of 75 to 100 pounds, black powder, exploding beneath
the ship, specifically addressing whether it could touch off an internal magazine
explosion in the 6-inch Reserve Magazine, giving results consistent with the known
damage to the USS Maine. (The 100-pound weight was chosen, and the analysis
also included gun cotton as an explosive material.)
- Damage from a larger mine explosion of more than 100 pounds of black powder,
exploding beneath the ship, specifically addressing whether it could touch off
an internal magazine explosion in the 6-inch Reserve Magazine, giving results
consistent with the known damage to the USS Maine. (Two larger mine sizes
were investigated, 200-pound and 500-pound. Both black powder and gun cotton were
assumed as explosive materials.)
The approach employed for the damage assessment was to:
- Examine historical records of the damage evidence resulting from naval inquiries
conducted in 189812 immediately
after the sinking, and again in 1911.13
- Gather reference materials on mines of the Civil War, Spanish-American War,
and Russo-Japanese War (1904-1905) eras.
- Gather reference materials on explosive characteristics of black and brown
gunpowder, and gun cotton (nitrocellulose).
- Gather reference materials on the plans of the ship, and thicknesses of hull
plates and bulkhead steel, as well as, it was hoped, some metallurgical information
on the types of steel used.
- Computer model enough of the ship, including internal bulkheads in the key
areas around the coal bunker and forward magazines, so that modeling damage .
. . can be performed to a reasonable level of confidence.
- Run the dynamic computer models under each of the scenarios, and reach conclusions
on each of the scenarios.
The AME analysts chose three kinds of explosives for analysis: black powder,
used for saluting guns; brown powder, used to fire projectiles; and gun cotton,
used as a high explosive in mines and torpedoes.
While reference material made available to use had useful data on black powder
and gun cotton, no technically meaningful data was found for brown powder, perhaps
because manufacture of this material stopped sometime prior to World War I. In
the absence of specific data, brown powder similar to black powder has been assumed
because each is a mixture of potassium nitrate, charcoal, and sulfur, although
brown powder has a lower sulfur contact (3% versus 12%) and a correspondingly
higher potassium nitrate content. The reduced sulfur content may result in a slower
rate of deflagration, but the higher potassium nitrate would support a more complete
burning of the charcoal and thus release more energy.
The weapons-effects models used for the damage assessment require explosive
characteristics inputs in terms of either TNT equivalencies or by providing the
combustion and detonation energies. The available references provided no data
on the needed energies but did provide sufficient information to derive TNT equivalencies.
The following table lists the TNT equivalencies of black powder and gun cotton,
and the reference source.
Heat of Explosion
NOTE: Some uncertainty exists regarding the brisance of
black powder. The indicated value was based on testing the powder when detonated
by tetryl lead azide, a high explosive. Uncertainty arises because it is not clear
how much, if any, of the measured brisance was caused by the tetryl lead azide.
If most or all of the brisance was caused by the tetryl lead azide, then black
powder when ignited by low-order methods such as spark, flame, or friction may
have little or no shock holing characteristics.
The sensitivity of the explosives to accidental detonation/deflagration is
required only for the black/brown powder, since that is the only material known
to be stored in the affected magazines. Examination of Drop Test (Impact Sensitivity)
results yield an impact velocity sensitivity of 12.6 feet per second.15
The 10-second temperature for explosion test is 385C
(725F). However, the longer the exposure to heat, the lower the ignition
temperature.16 Since sulfur
is the primary means of burning the charcoal in black powder and the autoignition
temperature of sulfur is 232C (450F), we have assumed a long-term
(greater than 10 seconds) heat sensitivity of 450F.17
Steel plating from the Maine's hull, thought to be available from the Naval
Historical Center, Washington Navy Yard, could not be obtained.
. . .18 Conclusions
in this section have been drawn by analysis and deduction
by an AME metallurgical engineer, based on re-view of technical
references, consultation with forensic metallurgists, and
In the second half of the 19th century, steel ships (as opposed to wrought
iron) were built in increasing numbers and by about 1890, the changeover was essentially
complete.20 The battleship Maine structural
drawings refer to the ship as an "armored steel cruiser" and the term "steel"
appears on the drawings in reference to plating thickness. Steel used to construct
the Maine is known to be of U.S. origin and fabrication.21
Steel plate fabrication in the 1890s was accomplished by hot rolling operations.
Typical compositions of "mild steel" were approximately 0.2% carbon, with strength
characteristics comparable to today's designation SAE (Society of Automotive Engineers)
1020, with nominal yield strength (Sy) of 40,000 pounds per square inch (psi).
. . .
AME's estimate for yield strength of Maine structural steel, in consultation
with other experts,22 is Sy=40,000 psi;
plus 10%, minus 20%. For our analysis, we have chosen the average of these upper
and lower bounds, or Sy=38,000 psi. Similarly, our estimate for ultimate tensile
strength (Su) is 60,000 psi. Both values have importance when using computational
methods to characterize structural failures under explosive loading.
Toughness is a measure of a material's ability to absorb energy before fracture.
It depends on both strength and ductility. A ductile material is one that can
undergo considerable plastic deformation before fracture. Hot rolled mild steel
plate in the normalized condition typically shows an elongation per unit length
(strain) of 30% in tension test specimens, and is therefore quite ductile. . .
Observation of Maine explosion damage in photographs shows very high distortion
of plating and structural members prior to failure, indicating that the steel
was a reasonably tough material. AME believes that 30% elongation is a good estimate
of ductility and that the structure was in the range of or above the transition
temperature, i.e., still "tough," in the warm Caribbean waters of Havana Harbor.
In order to use the internal blast damage model to analyze a ship of riveted
construction rather than welded construction, a factor must be included to account
for the reduced effectiveness of riveted construction when subjected to explosive
blasts. . . . Finite element models were developed of typical lap and butt joints
on board the Maine. The connections were evaluated for effectiveness under a membrane
load in the plate. . . .
(Click above for larger image)
The shell of the Maine is typically 20.4-pound plate (nominal half-inch thickness)
with foreaft lapped seams and athwartship butt seams. . . . [T]he joints were
typically constructed of double rows of rivets and that the majority of rivet
pairs were adjacent to each other, not in a staggered pattern. . . .23
[T]he butt joints were single-strap, double-riveted joints.
. . .
The interaction between rivets and plates is very complex. In order to model
this structure, the rivets were assumed to be beam elements with end beams representing
the rivet heads. The end restraints of the end beams connecting with the plates
were manipulated to represent the bearing and bending that occur at riveted connections.
. . . The material properties of the shell elements were represented using a stress
strain curve with a yield strength of 34 ksi, or thousand pounds per square inch
(corresponding to the type of steel used for the shell plating). The material
properties of the beam elements were represented using a stress strain curve with
an assumed yield strength of 30 ksi (corresponding to the type of steel used for
the rivets). The beam elements representing the rivet head were input as elastic
material with an elastic modulus of 30,000 ksi. . . .
In order to determine the ultimate capacity of the riveted connections, the
pressure load on the connection was applied in increments until excessive deformation
of the connection occurred. The . . . ultimate strength of the joint was determined
by looking for significant areas of strain above 20%. The membrane load that caused
this type of strain was considered to be the ultimate strength of the joint. .
The lap joint and the butt joint show similar ultimate capacities. The results
indicate that the joint begins to deform inelastically at about 35% of the total
load (34 ksi). At 45% of the load, significant portions of the plate around the
rivet holes have predicted strains above the 20% strain criteria. At this strain,
rupture may occur. This is the predicted ultimate capacity of the joint.
The finite element model shows that the failure of the joint occurs due to
pull of the rivet through the plate material. Photographs of the damaged Maine
support this predicted failure mode. The lap joint and the butt joint show similar
Using this approach, it was estimated that the ultimate capacity of a typical
riveted joint on the Maine occurs at a membrane load of approximately 45% of the
plate yield stress. This number was used to adjust the blast damage model failure
criteria for riveted connections.
Shock wave holing of the hull was analyzed to determine the possible mine sizes
and standoff distances that would hole the shell of the ship and transmit enough
explosion energy into the ship to ignite the magazine.
The method used to calculate the conditions necessary for initiating a hole
in the outer hull of a ship by explosion of a nearby mine relates (not equates)
the incident explosion energy to the energy absorption capability of the hull
plating in which the hole would be formed. Since part of the incident explosion
energy will be reflected rather than absorbed by the plate, the incident explosion
energy will be greater than the energy absorbed by the plate. By geometry, the
incident energy per unit area of the plate is proportional to the energy of the
charge divided by the square of the distance from the target plate, while the
energy absorption capability of an area of plate is proportional to its strain
energy (integral of stress times strain) up to rupture, multiplied by its thickness.
Since we cannot equate these energies, we simply set up two dimensionless variables,
one involving energies and one involving linear dimensions, thereby ensuring similitude.
The relation between these two variables is acquired from numerous experiments.
Calculation of the size of an opening follows similar logic. Calculations of the
amount of energy that can be absorbed by the plate up to its rupture show this
energy to be a small fraction of the incident energy (on the order of 5%). One
can assume that the remainder of the incident energy is transmitted into the ship
space beyond the opening as blast energy. This would seem to be an upper bound
on energy transmitted, and test evidence supports this position.
The inputs needed for the shock wave hole and the blast energy vented through
the hole calculations are: charge weight, standoff, plate thickness, yield strength,
and plate backing. Two possible mine explosives were considered: black powder
and gun cotton. . . . Three weights (100, 200, and 500 pounds) and three standoffs
(contact, middepth [7 feet], and bottom [14 feet]) were analyzed for each explosive.
. . . A thickness of .5 of an inch (taken from the ship structural drawings) and
a yield strength of 38 ksi were used. The shell plate was air-backed.
The interior blast damage model was then run to determine if the residual energy
for any of the mines that shock-holed the bottom plating was sufficient to fail
the inner bottom plating and vent explosion energy into a magazine above. It can
be assumed that once explosive energy and gases are vented into a magazine, the
magazine will ignite. The modeling showed that even the smallest residual TNT
(i.e., TNT equivalent weight of energy vented through hole . . . 6.5 pounds from
the 100-pound black-powder contact mine) would cause failure of the inner bottom
and, therefore, ignition of a magazine's contents. It can then be assumed that
for the charge weights and standoffs shown in Table, if the mine holed the shell
below a magazine and transmitted energy into the interior of the ship, it would
ignite the magazine.
Damage assessments for the effects of explosions of various charge weights
and initial source locations in the forward magazines of the Maine were
conducted using an interior blast damage model . . . similar to those in use by
the U.S. Navy as a diagnostic tool. . . . The model calculates the intense pressure
that is generated during an explosion as a function of time and then systematically
determines the effects of the quasi-static overpressure acting on the plating
of the decks, bulkheads, and overheads that form the boundaries of compartments
exposed to the blast, beginning with the compartment that contains the source
explosive. An experimentally derived boundary plate failure criteria is used to
determine when a pressurized compartment's boundary plates begin to fail and adjacent
compartments are opened to the blast pressure, or when the blast pressure begins
to vent either to the atmosphere or to the sea (in the case of a failure of the
submerged portion of the hull plating). . . .
[T]he Maine was constructed using riveted connections. A finite element
analysis of a riveted lap joint and a single strap butt joint typical of the types
used on the Maine, showed that eccentricities in the loading produce high
localized stresses in the plating around the head of the rivet that results in
a connection failure when the membrane stresses in the plating are only about
45% of the yield stress for the material (the stress level at which permanent
deformation begins to occur). This means that under blast loading, the individual
plate segments that comprise a compartment boundary panel will tend to unzip along
lines of riveted connections without any appreciable stretching, or bulging, of
the material. . . .
The results of the shock wave holing study showed that the residual explosive
energy in the inner bottom compartment under the 6-inch Reserve Magazine from
a 100-pound black-powder mine exploded at maximum holing distance would be equivalent
to the explosive energy developed from the detonation of 6.5 pounds of TNT. This
equivalent explosive charge weight was used as an input to the model. The results
of the assessment showed that this amount of explosive energy was sufficient to
cause a failure in the inner bottom plating and to ignite the contents of the
magazine. Since the 100-pound mine produces the least amount of residual explosive
energy, it was concluded that any mine size and attack geometry that was capable
of holing the outer shell would also penetrate the inner bottom and ignite the
contents of the magazine.
A model for an initial explosion in the forward 6-inch Magazine produced a
scenario showing that the explosion could not have occurred in the 10-inch Magazine.
The report then looks at an initial explosion in the 6-inch Reserve Magazine.
This scenario assumes that the initial explosion occurred in the 6-inch Reserve
Magazine, and that 7,200 pounds of black and brown powder (approximately 80% of
the maximum allowed loadout) was exploded.24 It
was also assumed that the inner bottom and outer bottom plating below the magazine
was intact at the time of the explosion. This loading condition corresponds to
the scenario postulating that the explosion was initiated by a local hot spot
in the coal bunker outboard of the magazine. An initial explosion in the 6-inch
Reserve Magazine of such a magnitude produces an initial damage propagation pattern
that is supported by the historical evidence. Immediately following the explosion,
the watertight bulkheads at Frames 24 and 30 and the longitudinal bulkhead separating
the 6-inch Reserve Magazine from the 10-inch Shell Room fail. This allows the
blast pressure to propagate forward into the Fixed Ammunition Room, aft into the
Forward Fireroom, and across the ship from port to starboard. Failure of the starboard
Shell Room bulkhead opens the 10-inch Magazine to the blast after just 0.73 ms
(miliseconds). At this time, the blast also begins to propagate upward into the
Electrical Storeroom on the Platform Deck level. The forward 6-inch Magazine is
opened to the blast 1.25 ms after the explosion. The side shell forward of Frame
24 fails at 1.43 ms. Initial outer bottom failures occur on the port side between
Frames 24 and 30 at 1.64 ms. Additional failures in the outer bottom plating occurs
on the port side between Frames 21 and 24 approximately 2 ms later. The initial
side shell failures on the starboard side occur just forward of Frame 24, but
not until 5.02 ms after the explosion. The blast continues to propagate upward
and forward in a general port to starboard direction. After 100 ms, pressures
throughout the forward section of the ship have equalized. The outer bottom hull
plating on the starboard is essentially unsupported but remains intact. The Main
Deck has failed forward and aft of Frame 30, starting on the port side. . . .
A review of the damage propagation predicted by the model correlates very well
with damage descriptions. . . with one notable exception. The 1911 damage evidence
indicates that a section of outer hull B and C strakes was displaced upward, inward,
and to aft and starboard. This type of damage cannot be explained by the model
results. The model correctly identifies a failure of the outer hull plating in
this area. However, the model can predict only if and when a plate begins to fail
and the direction that the center of a plate is moving at the time of failure.
. . . Where or how a particular plate fails is irrelevant to the analysis, and
once it has been determined that a particular plate has failed, the geometry of
the plate is no longer a concern. Only the total mass of the plate is used to
estimate the rate at which venting into an opened compartment occurs. . . .
[A]t least 50% of maximum indicated loadout (10,600 pounds) would have to be
exploded in order to produce outer bottom damage on the port side between Frames
21 and 30 and to initiate venting through the Main Deck above the Forward Fireroom.
Further, if 100% of allowable contents are exploded, the model indicates outer
bottom failures on the starboard side between Frames 24 and 30 and a probable
failure of the keel web in this region. Since the predictions of starboard bottom
failure are unsupported by the physical evidence, it is concluded that a loadout
of between 60% and 80% of allowable is a reasonable estimate of the magazine contents
at the time of the explosion.
To assess the effects of a submerged mine venting residual explosive energy
into the magazine, it was decided to conduct an additional analysis of the 80%
loadout case (7,200 pounds of explosive material) by including vent openings in
the outer and inner bottom plating beneath the magazine. . . . The results . .
. show that venting has little effect on the early stages of the blast propagation.
. . . It appears that the explosive event is over before any appreciable venting
through the bottom occurs. The extent of the final damage is comparable for both
cases (i.e. bottom intact and bottom open to sea).
Next, the report looks at the effects of a sequenced explosion of the contents
of all three forward magazines, based on the assumption that 80% of the contents
of each magazine (a total of 38,800 pounds of black and brown powder) would be
exploded. This scenario would apply to either an explosion caused by a mine or
a coal bunker fire.
In general, the extent of the overall damage predicted by the model correlates
well with the descriptions of the physical damage included in the 1911 Report.
However, the prediction of outer hull plating failures on the starboard side between
Frames 24 and 30 is contradicted by the physical evidence, which states that the
outer hull plating on the starboard side is intact for the most part. This suggests
that the estimate of 38,800 pounds of explosive content may be too high. A more
precise estimate of the magnitude of the explosion cannot be made without the
aid of additional assessments. It is also possible that the starboard outer hull
plating could have unzipped along the keel strake but reMained relatively
intact. The model cannot predict how a particular plate fails.
(Click above for larger image)
The 1911 investigation used the above photo to bolster its
case that a mine caused the Maine to sink. The upturned outer bottom plating seemed
to be the tell-tale evidence. Admiral Rickover's study concluded, however, that
the plating "was bent inward by the dynamic effects of the magazine explosion
and the sinking of the ship." Ironically, the recent AME study returned to the
same photo to reach its conclusionthat a mine probably caused the initial
explosion that eventually sank the ship.
(Click above for larger image)
Results of the finite element modeling of welded versus riveted connections
demonstrate that steel plates connected to ship's structure can withstand plate
deflections of only about 15% of welded connections. This conclusion was based
on the modeling determination that riveted joints fail at about 45% of the steel
plate's yield strength.
Results of this modeling were used to adjust the plate-failure criteria contained
in the internal blast damage model.
Results of the heat-transfer modeling indicate that heat transferred from a
coal fire in the Coal Bunker could elevate temperatures in the 6-inch Reserve
Magazine beyond an estimated ignition level of 450F in four hours.
Results of the shock holing and the shock velocity models indicate a 100-pound
black-powder mine could penetrate both the outer shell and inner bottom to ignite
magazine contents. The modeling also indicates that mine standoff distances large
enough to prevent shock holing are also large enough to prevent ignition of magazine
contents, due to critical shock impact velocities. The shock holing model, however,
is unable to determine plate failure due to non-shock-wave loads such as those
produced by underwater explosion bubble expansion pressures and bubble collapse
impulses. Results of the internal blast damage modeling confirm the 6-inch Reserve
Magazine was the first magazine to mass detonate, followed in short order by the
6-inch and 10-inch Forward Magazines. . . .
We conclude that while a spontaneous combustion in a coal bunker can create
ignition-level temperatures in adjacent magazines, this is not likely to have
occurred on the Maine, because the bottom plating identified as Section
1 would have blown outward, not inward. Others have postulated that the inward
bending of this panel could have resulted from the failure of the top of the watertight
bulkhead at Frame 30 in an aft direction, pulling the inner bottom and outer shell
plating and attached structure with it.25
This scenario seems implausible, because while failures to a bulkhead from
quasi-static overpressure have been known to pull pieces of connected deck plating
with it in welded structures, on the Maine the bulkhead to deck rivets
would fail long before sufficient bending moments could be imposed on the stiffened
inner bottom/outer shell grillage.
Another theory [i.e., Rickover's] poses that the inrush of flooding water somehow
could have not only reversed the downward bent plates and attached structural
support to an inward position 180 from its original location, but to have
done so without similarly affecting adjacent plating is also deemed implausible.
The most plausible explanation for the position of this plating is that non-shock-wave
loading from an underwater mine, located beneath this plate section, caused the
rivet connections to fail and pushed the plate section up into the ship; it in
turn took the inner bottom plating above it up into the 6-inch Reserve Magazine
at the inboard aft corner and ignited the contents. Most likely, the plate position
just prior to ignition of the magazine contents did not move aft of the watertight
bulkhead at Frame 30, but the ensuing magazine mass detonation pushed it and the
watertight bulkhead aft and nearly horizontal in its observed final position.
In this scenario, the smooth appearance of the outer shell compared to the severe
crumpling of the inner bottom plating can be explained, due to the fact that the
inner bottom plates were only 5/16 of an inch thick, while the outer bottom plating
is a half-inch thick and nearly three times as strong in banding resistance. Also,
the inner bottom plating is forced into a tighter bend radius than the outer plates.
Since the Shell Holing and Internal Blast Damage Models cannot simulate this
type of failure, finite element modeling would have to be conducted to confirm
our determination more conclusively. This level and type of modeling was neither
planned nor included in our estimates for performing the damage assessment. .
This study strengthens the arguments in favor of a submerged mine as the cause
of the sinking. . . .
The summary conclusion of this study is that the explosions that caused significant
damage to the Maine, and were related to the ship's sinking, could have
been by either of two possible causes:
- a magazine explosion induced by proximity to a coal bunker fire
- a magazine explosion induced by an under-ship mine.
The coal bunker could have experienced a local area of combustion, which would
have gone undetected from the top of the bunker. If in proximity to the bulkhead
that divided the bunker from the 6-inch Reserve Magazine, the magazine is predicted
to have experienced a heat rise to a level sufficient to cause ignition of the
gunpowder in the magazine. The temperature of the combustion in the bunker was
assumed to be 1,000F. After four hours, starting at ambient conditions of
100F within the magazine, the temperature six inches from the bulkhead within
the magazine was predicted to be 645F. Gunpowder is predicted to ignite
at a temperature of 450F. The predicted high temperatures are sufficient
to have caused the contents of the 6-inch Reserve Magazine to explode, which would
have in turn caused the Forward 6-inch Magazine and 10-inch Magazine to explode.
The damage resulting from this series of explosions is unlikely to result in the
inward bent bottom structure.
(Click above for larger image)
It is plausible that a mine caused the explosion in the 6-inch Reserve Magazine,
which in turn caused the explosions in the 6-inch and 10-inch Forward Magazines,
leading to the sinking of the Maine. Shock holing predictions show that
a 100-pound black-powder mine could penetrate both the outer shell and inner bottom
to ignite the 6-inch Reserve Magazine contents. Blast-damage modeling confirms
that sequential detonation of the 6-inch Reserve Magazine, 6-inch Forward Magazine,
and 10-inch Forward Magazine would result in damage consistent with the physical
evidence, with the exception of the inward-bent outer bottom plating. A reasonable
explanation for the position of this plating is that an underwater mine failed
the rivet connections and pushed the plate section up into the ship, followed
by ignition of the 6-inch Reserve Magazine. In addition, the size and location
of the soil depression below the Maine is more readily explained by a mine
explosion than by magazine explosion alone. While it is possible that the depression
was independent of the explosions, it cannot be ignored. The sum of these findings
is not definitive in proving that a mine was the cause of the sinking of the Maine,
but it does strengthen the case in favor of a mine as the cause.
In view of the predicted damage resulting from an under-ship mine and the similarity
of the recorded damage to the ship (and the coincidental depression in the harbor
bottom), it appears more probable than was previously concluded that a mine caused
the inward bent bottom structure and detonation of the magazines. Unfortunately,
it is impossible to go back in time to obtain all the facts. A mine could have
caused the explosions; but how would that mine have been placed and why? A bunker
fire could have caused the explosions, but how can the inward bent plate be explained?
It is left to the independent reviewers of the data to evaluate the information
and form an opinion.
- Norman Polmar and Thomas B. Allen, Rickover: Controversy
and Genius (New York: Simon and Schuster, 1982). back to article
- H. G. Rickover, How the Battleship Maine Was Destroyed
(Washington, D.C.: Government Printing Office, 1976). A revised edition was published
in 1995 by the Naval Institute Press, with a new foreword by Francis Duncan, Dana
M. Wegner, Ib S. Hansen, and Robert S. Price. A new appendix gives details of
World War II ship damage not available in 1976. The authors use this data to bolster
their findings that a mine did not destroy the Maine. back
- Handbook 1081, Primer On Spontaneous Heating And Pyrophoricity
(U.S. Department Of Energy (DOE). back to article
- Environment Safety and Health Bulletin EH-93 -4, The
Fire Below: Spontaneous Combustion in Coal; U.S. Department Of Energy. back
- Handbook 1081 (U.S. DOE). back to
- William H. Garzke Jr., David K. Brown, Arthur D. Sandiford,
John Woodward, and Peter K. Hsu, "The Titanic And Lusitania: Final Forensic Analysis,"
Marine Technology, October 1996. back to article
- Fire Protection Handbook, 16th edition (National
Fire Protection Association [NFPA]). back to article
- Ibid. back to article
- Handbook 1081 (U.S. DOE). back to
- Fire Protection Handbook (NFPA). back
- "The Report of the Naval Court of Inquiry Upon the Destruction
of the United States Battleship Maine in Havana Harbor February 15, 1898,
Together With Testimony Taken Before the Court" (Washington, D.C.: Government
Printing Office, 1898-Library of Congress). back to article
- The Report of the Naval Court of Inquiry, 1898.
back to article
- Report on the Wreck of the Maine, 14 December 1911.
back to article
- All figures in table from Cooper and Kurowski, Introduction
to the Technology of Explosives (VCH Publishers, 1996) or Explosives and
Demolitions (Department of the Army, FM 5-25, Feb. 1971). back
- T. L. Davis, The Chemistry of Powder and Explosives
(New York: J. Wiley & Sons, 1941). back to article
- Cooper and Kurowski, Introduction to the Technology
of Explosives. back to article
- Sax and Lewis, Hazardous Chemicals Desk Reference
(New York: Van Nostrand Reinhold, 1987). back to article
- N. Cary, Head, Curator Branch, Naval Historical Center,
Washington, D.C. back to article
- S. Hering, M. Mat. Sci., B. Met. E., Advanced Marine Enterprises,
Arlington, Virginia. back to article
- D. A. Fisher, The Epic of Steel (New York: Harper
& Row, 1963) Chapter 18. back to article
- D. Wegner, Curator of Models, Carderock Division, Naval
Surface Warfare Center, Bethesda, Maryland. back to article
- H. Keith, Ph.D., Forensic Metallurgist, Marathon, Florida;
T. Foecke, Materials Scientist, National Institute of Standards and Technology,
Gaithersburg, Maryland. back to article
- The Report of the Naval Court of Inquiry; Rickover.
back to article
- Robert H. Cole, Underwater Explosions, (Princeton,
NJ: Princeton University Press, 1948). back to article
- Rickover analysis. back to article
Mr. Allen is a prolific writer and military historian and is the
author of "Remember the Maine?" which appears in the February 1998 issue
of National Geographic magazine. Mr. Allen and the U.S. Naval Institute
gratefully acknowledge National
Geographicparticularly the magazine's Senior Researcher, David W.
Wooddellfor allowing Mr. Allen to adapt its Maine report for publication
in Naval History.
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