Torpedo Running Depth was Optimal for Striking USS Liberty, not El Quseir
By Ken Halliwell (November 14, 2004)
The torpedo blast hole, on the starboard side of USS Liberty, is about two-thirds of the distance back from the bow to the front edge of the superstructure. It was a significant battle damage feature and well documented via many photographs taken from different perspectives.
Upon close inspection of the photographs, you will see the hull's horizontal weld-lines. These weld-lines are identically placed on all Victory Ship hulls (USS Liberty was a converted Victory Ship). Thus, they provide critical points of reference for analytical purposes.
By treating the photographs as perspective drawings and applying engineering drawing analysis techniques, the blast's hole dimensions and center (i.e., the point where the torpedo hit) were determined. To validate and enhance the photographic analysis work, actual blueprints of a Victory Ship hull were used to obtain dimensional and structural data.
The analysis revealed that the blast hole appeared somewhat oval-shaped with a short smoke stack sitting on top. The "smoke stack" or vertical tear was about 8' high. The main hole was at least 36' wide and 16' high - yielding a total height of 24' when including the vertical tear hole.
In photographs, it's clear that the bottom edge of the blast hole appears flattened. This was likely due to the strength of the double-bottomed hull resisting and limiting blast force damage. Generally, like all forces in nature, the path of least resistance determines a blast force's dominate direction of propagation or expansion. In this case, the water-air interface above the blast's center offered the path of least resistance. As such, a large portion of the blast's intense force rapidly projected upward, along the side of the ship, likely contributing to production of the vertical tear, and finally resulting in a large, vertical water spray in the air.
In the images above, the blast force is idealistically depicted as a perfect circular zone, with a diameter determined by the horizontal edges and curvature of the blast hole. The center of this circular blast force zone is the focus or center of the torpedo blast - marking where the torpedo hit and its running level. As you can see, the vertical centerline appears very near, if not exactly matching, one of the ship's major vertical frames or ribs. The horizontal centerline appears about 12' below USS Liberty's estimated operating draft level (21' 6") during the attack. In other words, the torpedo's running depth was about 12' (close to 4 meters) below the water's surface.
Using a blueprint of one of USS Liberty's major frames, with operating draft level and torpedo running depth added, a comparison was made with an outline of El Quseir's hull sitting at various draft levels. As you can see below, the comparison revealed the torpedo's running depth was too low to reliably strike El Quseir. If El Quseir carried a full load of fuel and cargo (i.e., riding at her maximum 14' draft level), then the torpedo would have likely hit her bottom, but if she carried less than a full load of fuel and cargo (i.e., riding a few feet less than her maximum draft), then the torpedo would have likely missed.
Thus, to ensure striking El Quseir's hull one would expect the torpedo's running depth to be no greater than about 7'(about 2 meters) or half El Quseir's maximum draft. With the torpedo's running depth at about 12', it was slightly more than half of USS Liberty's maximum draft (22', 6"). So, it appears that the torpedo's running depth was optimally set to strike USS Liberty's Victory Ship hull and not El Quseir's hull - as depicted in the image below. (Note: the torpedo boats all carried pamphlets that gave the maximum draft of El Quseir; thus, they all had data available to set an optimal torpedo running depth for targeting El Quseir.)