La versione originale italiana di questo articolo è sul blog 11-settembre dell'autore.
"Alternative" theories claiming that no hijacked aircraft struck the World Trade Center and the Pentagon have recently resurfaced. In the case of the WTC attacks, the sheer number of eyewitnesses and the abundance of evidence are sufficient to show clearly the absurdity of these "no-plane" theories. However, the matter is quite different for the Pentagon strike and therefore deserves further discussion.
If we assume that no plane hit the Pentagon, then we are invariably faced with the alternative suggestion of a missile. A truck bomb is absolutely out of the question because of the utter lack of evidence for this kind of attack.
It should be noted that some alternative theories suggest that the Pentagon was indeed hit by an aircraft, but not by Flight 77. Such theories consider a drone or a smaller aircraft. Either way, they imply the impact of an aircraft and as such cannot be considered "no-plane" theories and are beyond the scope of this article.
The missile theory had been sidelined because many, in the US 9/11 truth movement, felt strongly that the lack of clear audiovisual evidence of the impact of AA77 was a sinister booby-trap prepared by US authorities to ridicule once and for all the entire truth movement at the appropriate time (for example, by releasing new footage or pictures, or by showing the debris of AA77 set up in a hangar). However, a 2007 speech by the late Cuban leader Fidel Castro, in which he accused the US government of orchestrating a colossal criminal operation with vast media coverage to conceal what he believes was a coup, has given new life to the missile theory.
Castro in fact claimed that "only a projectile could have created the geometrically round orifice created by the alleged airplane". He is certain that no plane hit the Pentagon and that one of the many missiles in the US arsenal was used instead.
I entirely disagree with this theory, because not only there is no evidence to support it, but there is, in my opinion, considerable evidence that allows to rule it out. Let's examine this evidence in detail.
I will not focus on the individual types of ordnance available in the US military arsenal or on the acronyms that identify the various missile types and flight profiles. Specialist websites already cover these in excellent detail. Rather, I will deal with the main evidence at the crime scene which allows to exclude the possibility of a missile attack at the Pentagon.
First of all, let's consider the only characteristic of a missile attack that I think is worth examining in detail: the angle of the attack profile. Here are some frames of special high-speed footage taken during test firings in US proving grounds, which I think speak more clearly than many words.
Effects on the target
The pictures show clearly that the missile is not designed to explode upon impact against the target (in this test, a reinforced-concrete structure). It must penetrate the structure, piercing its hardened outer shell, and then detonate inside it, producing a pressure and thermal gradient whose effect is actually enhanced by the resistance provided by the structure.
In practice, penetration is achieved thanks to the kinetic energy of the missile and to the use of penetrators made of steel and, more recently, titanium, which enclose the explosive charge.
When detonation occurs, the entire structure is subjected to extremely intense stresses from the inside outward, due to the detonation of the explosive charge carried by the missile body and of any ammunition stored inside the target.
This is clearly visibile in the picture below, which shows that the entire structure is affected simultaneously and in all directions with the same intensity.
Obviously, the effects of the explosion are greater if the volume inside the target is small and if there are few pathways for venting the overpressure. An explosion in an open space is less destructive than the same explosion in an enclosed space.
Therefore, the asymmetries of the various observable macroeffects are not linked to the directionality of the stresses but to the different resistance provided by the materials and the design of the interior cavity in which the explosion occurs.
The explosion of a conventional demolition charge occurs in any case according to a rough symmetry, linked mostly to the shape of the charge and the resistance of the container, but in large spaces these effects in practice do not have a clearly identifiable role with respect to the extent of the resulting destruction.
In theory, the detonation speeds of high explosives allow us to model, as a first approximation, the explosion of a charge of this type as a static point-like charge which develops its effects spatially with a spherical geometry.
For particular applications, such as the interception of rapidly approaching airborne targets, missile charges have been developed which have a directional distribution of the effects of the explosion (shrapnel distribution and pressure wave). The purpose of these charges, which take advantage of particular geometries of the explosive and employ multiple-trigger electronic systems, is to maximize the destructive effects in the chosen direction, reducing the spatial dispersion of the pressure gradient and especially of the shrapnel formed by the charge container.
This requirement arises from the need to minimize the weight of the charge, accordingly reducing the total weight of the missile: this allows to increase its agility in performing course corrections and its maximum speed, and also allows to reduce the flight time to engage the threat.
Directional charges, therefore, are conceived to be used with point-like targets (to concentrate the effects of the explosion on a small surface, to overcome the resistance of the target and destroy it, as in the typical case of armor piercing), or to create walls of shrapnel and high-pressure regions in specific portions of space, in a direction which is not aligned with the missile axis (a typical example is the use of directional charges that explode at right angles to the trajectory in order to strike a target as the missile flies alongside).
The presence of a directional charge does not imply at all that the effects of the explosion, especially within an enclosed space, are nonexistent in the other spatial directions. An explosion is in practice an instantaneous phenomenon, which triggers subsequent mechanical phenomena related to the repeated impacts of secondary projectiles which draw their kinetic energy from the force impulse received during the explosion.
The trajectories of these secondary projectiles are a bundle of straight lines which converge at the point where the charge is located.
Of course, the first-approximation model stops when the pressure waves strike the resisting structure, because at that point the reaction of the target is tied to the actual characteristics of the medium and of the structures that are hit (pressure and thermal gradient, resistance and resilience of the materials, type and uniformity of the materials, presence or absence of discontinuities between the resisting elements, impulsive resistance of the materials to the impact).
Models for studying impulsive phenomena are very complex, indeed because they cannot be approximated by derivable functions. By definition, a function, in order to be derivable, must be continuous, but this makes it impossible to use such functions to approximate impulsive phenomena, which by definition are not continuous. It is necessary to resort to advanced computational systems, which are in any case approximate and are normally presented in higher-level courses on mathematical analysis or in the teaching of mathematical methods for engineering.
Certainly it is not appropriate, here, to delve into such models, because the challenge would be truly difficult and would require a solid experimental stage. However, for the purpose of this discussion it is sufficient to bear in mind that the detonation of a main charge is substantially omnidirectional and is intended to shatter the resisting structure from the inside, generating the maximum possible number of secondary projectiles (shrapnel, impacted objects which in turn strike other objects) having an extremely high kinetic energy, in addition to pressure and thermal peaks capable of disabling personnel and equipment.
Also, we must not forget that wave phenomena, essentially of the pressure-related type, are affected strongly by reflection and refraction. The direction of the motion of the missile, instead, does not have a substantial effect on the mode of detonation, because the time frame after initial impact is extremely small.
Analysis of the trajectories of the secondary projectiles allows to identify easily the position of the charge at the time of the explosion: it lies at the vertex of the three-dimensional bundle of trajectories of the secondary projectiles. To trivialize matters extremely, a missile is merely a vehicle which carries a bomb into a target.
The vertical or horizontal mode of target attack is chosen only to facilitate this task of the missile: to achieve penetration of the target and "deposit" a bomb, which then explodes.
These concepts are clearly shown by the final frames of the two image sequences shown above. The effects of the explosion are in practice undistinguishable in a horizontal or vertical attack. They are the same: what changes is only the path along which the charge is deposited inside the target.
Clearly I am greatly simplyfing the matter, but all this allows us to understand that the choice of the angle of attack does not depend on technical issues of the vehicle, but rather on the tactical requirements of the target (e.g., a surface target masked or not by other buildings) or by operational requirements (striking sites below ground, as in the case of underground command bunkers) and on the structural features of the target (weak points such as air intakes).
One other variable that needs to be considered is that the flight profile of the missile affects considerably the surprise effect and the ability of the target to react preventively. This is why cruise missiles usually are terrain-following, i.e., they fly at very low altitude, following the contour of the terrain according to computerized maps stored in their guidance system. This flight profile allows to use the shape of the terrain to avoid radar detection and any local defense systems.
The Milosevic photo
The effects of missile-related explosions on a non-reinforced building are quite evident, as shown by the well-known picture of Slobodan Milosevic's home, hit by missiles of this kind.
This photograph is featured often in Internet articles that analyze the damage to the Pentagon and is usually "interpreted" in a distorted way to provide support for preconceived theories. Let's try to analyze it correctly, in order to find aspects which may be useful in a subsequent investigation of the Pentagon event.
First of all, the explosion effect inside the target is absolutely evident. Note the effect on the eaves, which "swell" upward and outward. The severed column on the upper floor has been pushed outwards, the ceiling is gone and the roof has exploded upward (notice the edge of the floor slab, which has failed, and the downward bulge of the portico ceiling).
The missile easily penetrated the masonry and exploded in the rooms at the rear, which were completely devastated by the shockwave. Their non-bearing walls collapsed outward completely. These walls were certainly weaker and their collapse provided ample pathways for the outward venting of the pressure peak.
Debris was propelled at quite a distance from the building in all directions, in a pattern which is compatible with the presence of interior obstacles which hindered force propagation. The arrangement of the debris is certainly not due only to the vertical collapse.
However, the most interesting evidence is the least evident. Note the corner of the house that lies to the left of the struck portico, especially the correspondence between the damage on the inner edge (which has been affected more) and the outermost one.
The damage to both edges clearly shows that they were hit from the inside of the portico outward, with a pressure wavefront and with secondary projectiles which expanded (and therefore progressively decreased their energy) as they advanced away from the portico: this means that the forces were directed from the inside of the building outward.
Other evidence would be observable in a higher-resolution version of the photograph, but what we have is already enough to make our argument quite solid.
Let us now try to understand, at least on a basic level, the structure of the Pentagon in the impact area.
The Structure of the Pentagon
A brief summary of the construction features of the Pentagon is needed in order to place the analysis in context. The Pentagon has five floors above ground level and at least two basement floors (not all information is reliable, due to obvious secrecy reasons). It was built in haste (between 1941 and 1943) during World War II, with a particularly strong reinforced-concrete structure based on concrete columns with a steel spiral reinforcement which enclosed the core with the steel reinforcement rods.
Viewed from above, it appears to have five pentagonal concentric rings, labeled A-E from the innermost one to the outermost one. Structurally, however, it was built in independent sections.
The large horizontal surface and the small number of floors allowed to erect the Pentagon rapidly because work was carried out simultaneously on the various sections (wedges). Each wedge was connected to the adjacent ones by expansion joints which also provided an appropriate structural response of the building to temperature variations.
The Pentagon has five concentric rings when viewed from the air, but its cross-section reveals that there are actually only two separate rings, because there is a first outer block (rings E-D-C), followed by a ground level drive ("A-E Drive") and by a second block, which forms the innermost rings (B-A) starting from the second floor.
The vertical supporting structure of the Pentagon consists of columns which belong to three types, characterized by 6, 8 and 10 vertical rods forming the reinforcement of the central core, around which the strengthening steel coil winds. The assembly is filled with concrete. The ground floor is essentially built on columns with 8 or 10 rods, while the upper floors typically have 6-rod columns.
The remains of this particular metallic reinforcement can be seen in a portion of one of the destroyed columns of the Pentagon:
At the ends of each column, the metallic reinforcement is linked to the floors slabs, consequently providing a structure of great strength, rigidity and load-bearing capacity both for compressive stresses and shear stresses.
The picture below shows the damage to column 3L in the region where it was tied to the upper floor slab, which in this specific case is the ceiling of the ground floor (first floor in US English) and the floor slab of the first floor (second floor in US English).
Column structure, therefore, can be shown schematically as follows:
The picture allows to appreciate the robustness of the assembly and the interlocking of the ends of the column in the horizontal structures, which in turn are particularly strong and based on a grid of reinforced concrete beams.
The diagram below shows schematically the structure of a floor slab:
Combined with the veritable forest of columns that supports it, the floor slab is a highly resistant yet slender horizontal structural member, which played a very important part in the building's response to the attack.
This structure was enclosed by a composite outer wall, with 6 inches of Indiana limestone as its outer face, followed by 8 inches of brick and, at the columns, 10 inches of concrete.
In the renovated section affected by the attack, the windows were blastproof and weighed 1600 pounds each. The panes were 1.5 inches thick and mounted on steel frames which in turn were supported by steel supports linked to the floor slabs, creating another very tough assembly.
The inner masonry also included a thin layer of Kevlar embedded in the plaster in order to provide better resistance of the wall against penetration of shrapnel or bullets of portable weapons and to reduce inward projection of debris in case of an impact against the building's face (secondary projectiles which in an external impact would detach from the wall even in the absence of direct piercing).
The damage to the building has already been described in this article (in Italian), which also offers a tentative reconstruction of the events linked to the attack.
The picture below shows the area to the left of the main entry hole in the building, immediately after the attack and before the impacted section collapsed.
Therefore, prior to the collapse, the damage reported and documented in the ASCE report can be summarized schematically as shown in the picture below, which clearly shows the portion of the building face that was penetrated.
The following pictures summarize the level of the damage inflicted inside the building to the individual columns.
First floor (second floor in US English):
The plan view of the ground floor, the one most directly affected by the impact, shows that the damage lies along a bundle of preferential directions, which are aligned with the direction from which the aircraft originated. Indeed, some internal columns, which were knocked down but remain attached at their base, show the same inclination with respect to the building's face.
This, in itself, in the light of what has already been discussed with regard to missiles, casts strong doubts on any theory which explains the damage to the Pentagon with an explosion inside the building. One should also refer to this article by Mother (in Italian).
In an explosion, one would expect the destruction to radiate in all directions from the point of explosion, generating a substantially spherical region of equivalent damage (i.e., of damage of the same level). Such a region would be circular in plan view. The main trajectories (substantially pressure-related effects) and the trajectories of the secondary projectiles (mechanical effects of objects which in turn have been struck by main effects) would belong to a single bundle whose vertex would lie at the point of explosion.
Besides the bundle of main trajectories of destruction, another aspect which is highly "suspicious" if one assumes a missile-related explosion is the progressive narrowing of the damaged region, with a highly elongated roughly conical shape, which contrasts sharply with what is actually known to occur in explosions caused by missiles.
If one considers that the level of destruction is roughly associable with the level of energy transferred to the structures, it is very difficult to think that an omnidirectional explosion could cause, inside a building with large interior spaces which are mutually equivalent in terms of structural strength, a highly elongated pattern having a practically triangular cross-section in plan view, and in which the energy-related effects decrease only in one preferential directions, without any indications outside that affected region.
These two aspects alone completely rule out the possibility that the Pentagon might have been hit by a missile. If we then consider that the floor slabs remained substantially intact, with no craters in the floor or in the ceiling, the theory of a missile explosion becomes totally unfounded.
In this regard, one only needs to view the following pictures, which clearly show that the floor slabs, where they failed, were not affected by high-explosive detonations: they were only affected by localized stesses caused by leverage of the nearmost column, which due to shear stress disrupted the integrity of the horizontal member. Here are a few examples of these localized failures.
Ground floor ceiling:
One might object that the region being discussed was not actually affected by the structural collapse and that in the collapse area things might have gone quite differently. Not so: the evident asymmetry of the damage with respect to the collapsed region is in any case evidence of high directionality of the damage wrought to the building and is inherently incompatible with the effect of high explosives.
(this article continues here)