Excalibur
This class vessel was originated when President Sheridan expressed the need for large warships in the Interstellar Alliance fleet. The Whitestar fleet had served admirably, but being no longer in production, their numbers were down after recent conflicts. Sheridan envisioned a vessel powerful enough to ensure dominance over any known foe.
When the engines promptly malfunctioned, the ship was towed to the weapons testing site. The vessel's heaviest weapons were used to destroy two asteroids. The first was fragmented by the heaviest standard batteries on the bow of the ship. The second, larger asteroid was similarly fragmented by the Vorlon-based main guns of the ship.
| In this image, we can see that there are actually
six cannons of this type in the bow section of the ship. It is unknown
why only four beams were fired at the asteroid in the test; but as Drake
and Garibaldi did not seem surprised by the test, it can be assumed that
the weapons were functioning within expected parameters at the time.
Assuming Sheridan's assessment is correct, each of the four cannons delivered
slightly greater than 1/4 of a Whitestar's total firepower. Thus,
the firepower of each cannon cannot be much greater than 3125 terawatts.
However, this calculation is generous, as it is based on the upper
limit of Whitestar firepower.
The size of this asteroid is not known. In the novelization, it is described as "small." The second asteroid is described as "large," and about the size of a Whitestar. Thus, this asteroid is a fraction of the size of a Whitestar. If we assume that the diameter of the asteroid is equal to half the length of a Whitestar, a generous volume estimate is 1,025,000 cubic meters. Fragmenting an asteroid this size could be accomplished using a centrally buried explosive with a yield of two kilotons. However, a centrally buried bomb is much more efficient than a beam weapon for fragmenting an asteroid - the beam has to penetrate to deep within the asteroid and cause fragmentation by thermal expansion. Thus, a ballpark estimate for the firepower of the combined forward batteries is between 1.4 terawatts and 12500 terawatts, with each of the four cannons that were fired delivering between 350 gigawatts and 3125 terawatts. |
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| The A Call to Arms novelization states that the second target was "a large asteroid, the size of a Whitestar cruiser" on page 69. The upper limit on the size of the Whitestar class is 250 meters long and 125 meters in width. If we generously assume that the diameter of the asteroid is equal to the upper limit of the length of the Whitestar, it has a volume of 8,200,000 cubic meters. |
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This image shows the asteroid clearly fragmenting,
with large chunks of rock being scattered in all directions. Fragmenting
an asteroid this size with a buried explosive would require a yield of
15.6 kilotons, the approximate yield of the "Little Boy" bomb dropped on
Hiroshima in the final days of World War II.
The novelization states that the asteroid was destroyed in less than one second, but it took nearly two seconds in the movie (55 frames at 30 fps). Thus, a ballpark estimate for the firepower of the main guns is 65 terajoules, with a power level between 35 and 65 terawatts. |
Energy beams are less efficient tools for asteroid fragmentation than buried explosives, to be sure. But the degree of difference in unclear. If we assume that energy beams are a full order of magnitude less efficient for this task, and assume that the asteroid is a full 1000 meters in diameter, a generous upper limit on the firepower of the main guns is 42,000 terajoules (10 megatons) at an instantaneous power level of 23,000 - 42,000 terawatts. Interestingly, this is on the same order of magnitude as the upper limit of Whitestar firepower, further emphasizing the generosity of that upper limit.
The Excalibur had to be towed to this test site because the propulsion systems were not functioning. However, this does not affect the validity of the above calculations.
Since this weapon should be on a vessel with a much higher power reserve, such as a Vorlon warship, it is doubtful that the weapon is as powerful as its true Vorlon counterpart, even in one shot measurements. To put it simply: the Vorlons have more power to pump into their weapons.
| During the 13 episode run of Crusade, the main guns were used several more times. In War Zone, they were used to destroy a Drakh vessel that was on a collision course with the Excalibur. The Drakh vessel was already a flaming wreck from the fire of the Excalibur's standard guns and the squadron of Thunderbolts in the battle, but the ship was closing rapidly and had to be destroyed quickly. The shot from the main guns completely destroyed the incoming vessel with ease. |
Main guns destroy incoming Drakh vessel. |
| In Each Night I Dream of Home, the main guns were used to destroy another Drakh vessel. This ship was larger than any other Drakh vessel seen in Crusade, and appeared to be much larger than the Excalibur. |
Main guns destroy a huge Drakh battle wagon. |
| In Racing the Night, the Excalibur was being pulled down toward a planet by a gravity beam. When the engines were unable to overpower the beam, Gideon ordered Thunderbolts to attack the beam's source. After several bombing runs were unsuccessful, Gideon ordered to fire the ship's main guns at the target. The destruction of the beam's power source resulted in a titanic explosion that ejected matter into orbit and caused a huge shock wave on the surface. When the ship was able to maneuver 53 seconds after firing (according to a crewman's report), the beam was no longer active. |
Main guns destroy the gravity beam's power source. |
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In The Long Road, a Technomage attempted to use a mine to focus his power so he could destroy an Earthforce warship in orbit. The warship's captain requested assistance from Gideon, who ordered the main guns to destroy the mine. The mine was destroyed, leaving surrounding trees unscathed. |
Main guns destroy a mine on the surface of a planet. |
It is difficult to estimate firepower from the first two instances mentioned above, as the beams probably caused the Drakh vessels' engines to explode in the first example, especially given the level of destruction. This is obviously what happened to the huge Drakh mother ship in the second example, as the beam hit only the starboard engine. The third example is equally elusive, as the resilience of the equipment on the ground is unknown beyond the fact that it can withstand missile attacks from Thunderbolts.
However, the fourth example is more interesting. The mine's size can be estimated and the amount of damage is evident.
Gideon, Galen, and another Technomage observe the mine. Note the trees on the far side of the mine. Those trees are approximately 20 pixels tall, and the visible portion of the mine (nearly the entire width) is 200 pixels wide. Assuming these trees are as large as mature redwood trees at 100 meters, the mine has a very generous estimate of 1000 meters in diameter. The near trees flanking the characters have much more narrow trunks than redwood trees, indicating less height. |
Close-up view of the mine. Note the size of the windows relative to the entire width of the mine. |
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This image displays the remains of the mine after the Excalibur destroyed it. Galen is in the foreground observing the secondary fires. The mine appears to be completely destroyed. However, the surrounding trees appear unscathed. The grass Galen is standing on appears green and unharmed. While the mine is destroyed, there is no smoking crater where it once stood, and even some structures are still standing. This is sobering evidence of the generosity of the above calculations. It appears that orders of magnitude less damage was inflicted than the destruction caused by the "Little Boy" bomb that was dropped on Hiroshima and leveled sixty thousand buildings, or the estimated 2 megaton Tunguska asteroid impact that leveled trees for hundreds of square miles. |
| The Excalibur also sports several arrays of anti-starfighter batteries. These are typically banks of three rapid firing pulse weapons that have rotating barrels. They strongly resemble "gatling guns" and appear to be controlled either by remote or by computer. |
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This image clearly shows that each of the three cannons has independent firing control. |
This image shows that there are multiple batteries of this type of weapon. |
This large cannon on the ship's bow rotates to track a target. It can rotate at least ninety degrees to each side. In this image, a large red pulse is exiting the barrel, about to deliver its destructive energy to its target. |
This image shows the rare firing of both beam cannons on this turret. The three cannons on this turret fire independently of each other. Note the wide firing arc as this turret turns well away from the ship's axis. |
This upper limit is further demonstrated by the fact that Captain Gideon immediately ordered the main guns to fire at the two ground targets attacked in Crusade. He did not attempt to use the standard batteries, regardless of the full minute of vulnerability after firing the main guns. These two examples can be viewed above. In one of these examples, another Earthforce Captain, in command of an Omega class destroyer, tells Gideon that his own ship does not have the capability to quickly destroy a target on the ground, but that Gideon's ship does. Gideon reluctantly orders the main guns to fire. This implies that the standard batteries on both ships have insufficient range to destroy a target from synchronous orbit.
