The Nova cannon is a massive weapon, the emitter barrel is nearly three meters wide, and lined with monopole polarized nickle. The entire apparatus masses in at an impressive 1,250 tons, making it only feasible for the largest of ships to mount. The majority of the mass is dedicated to shielding the host ship from the blast generated by the weapon. Nearly 3/4 of the weight is a pressure cast alloy of iron and lead with trace amounts of vanadium, molybdem, and boron. This blocks heavy particle emisson into the ship.
Within the reinforced casing, multiple MASERs are focused on a single point filled with a mixture of vaporized iron, and tritium, an exotic heavy form of hydrogen, also known as Hydrogen-3. The masers superheat the vapor into plasma in a few milliseconds, and during that time, the mixture, controlled by a magnetic jar undergoes a nuclear fusion reaction.
The resulting blast is channeled by the magnetic bottle through the nickle lined barrel at 1/4 the speed of light. Nova cannons have a strategic range measured in millions of kilometers, able to strike planets, asteroids, and stationary targets with devastating results.
Mobile ships are able to avoid long range nova bolts with ease as they are not at all subtle. At short range the weapon is powerful in ship to ship combat, vaporizing enemy ships with alarming ease. Such a weapon would seem unstoppable, save for several key drawbacks.
The nova cannon cannot deliver sustained fire. The weapon needs signifigant amounts of time to cool after firing, and to be recharged for a second blast. Sustained firing can cause signifigant degridation of the cannon lining that can lead from radiation, and thermal leakage into the host ship to a failure of the magnetic jar, and the thermonuclear disintigration of the host ship.
The cannon also requires near constant maintainence. Basic maintainence indicates that the MASER emitters should be disassembled and inspected for damage every other discharge, while the nickle barrel, and mag-field generators should be inspected daily. Inspecting the barrel itself is a dangerous task as it sends a sailor into the barrel to inspect for damage to the liner, such as microscopic cracks, or other stress fractures and deterioration. A second hazard involves exposure to radioactive elements within the cannon. Radioactive isotopes embed themselves in the liner of the cannon, making inspections dangerous to the inspector.
All negatives aside, the Model XX is a signifigant improvement over the Model X which could only be fired once, and then had to be completely replaced.