Editing WH40K: Nova Cannons

=='''Nova Cannons'''==

''“If one weapon could be said to exemplify the righteous fury of the God-Emperor’s wrath, it would be the Nova cannon.”''<br />–Captain Laurent Strophes

Nova Cannons are a classification of exceptionally powerful weaponry that can only be mounted upon capital ships. Mounted below the heavily armoured prows of Imperial Navy cruisers and battleships, Nova Cannons have few equals in terms of their range or destructive power. While variation exists, a typical Nova Cannon consists of an array of potent gravimetric impellers designed to accelerate a projectile to a fraction of the speed of light. These projectiles vary more than the nature of the cannons themselves, ranging from sophisticated plasma warheads which burn with the ferocity of a small star for a fraction of a second, to implosive devices which exert destructive gravitational forces upon all those caught within several thousand kilometres of the detonation. In any case, a well-used Nova Cannon is a terrifying thing to face, as much a psychological tool as a weapon.

The weapons however are often ill-favoured by the Imperial Navy, with most captains preferring to utilise the more traditional torpedoes. Those few who favour the weapon understand that it is difficult to use and often rendered useless at close ranges. Firing The noVa cannon

Nova Cannons are extremely powerful weapons, easily able to wreak vast destruction upon enemy vessels at great range, but are inaccurate and require a stable vessel to fire effectively. Due to the lethal nature of their warheads, nova cannon shells are not armed for a fraction of a second after firing, allowing them to travel many tens of thousands of kilometres through the void before they become truly deadly. For these reasons and several others, nova cannons follow a number of specific rules when firing which do not apply to other weapons.

If a ship performs a Manoeuvre Action with a total modifier of greater than Difficult, it may not fire its Nova Cannon in the same turn. Similarly, a Crippled ship may not fire its nova cannon. Once a Nova Cannon has fired, its crew must spend the subsequent turn reloading and preparing the weapon for a second firing. This means a Nova Cannon may only fire once every other turn.

When firing a Nova Cannon, nominate a single point anywhere within the weapon’s maximum range that is more than 6 Space Units from the ship and in the vessel’s Fore firing arc. That is the target point. The difficulty of targeting with a nova cannon is such that all attack rolls with the weapon suffer an additional –4D penalty. Otherwise, the attack roll is resolved normally using a character’s Skill during a Shooting Action, including the normal modifiers for range. A successful attack roll means that the shot was on target and detonates at the desired point. A failed attack roll means that the shot was not on target and has instead detonated too soon or too late. However, such is the power of these weapons that even an inaccurate shot may still damage the enemy. For every degree by which the attack roll failed, the target point moves 1SU away from the firing ship if the attack roll was an even number (i.e. a number ending in 0, 2, 4, 6 or 8), or 1SU towards the firing ship if the attack roll was an odd number (i.e. a number ending in 1, 3, 5, 7 or 9).

In either case, any vessel within 1 SU of the target point will be hit by the shell’s detonation, dealing the weapon’s normal damage. Damage from a Nova Cannon shell ignores armour. Any damage dice that roll a 6 causes one Critical Hit. If a Critical Hit is scored, then roll 1D extra damage and apply the results as normal. Such is the power of the Nova Cannon that it may cause multiple Critical Hits in this way, rather than a maximum of one as is the case for most weapons.

An accurate Nova Cannon shell can potentially deal far more damage. If the attack roll succeeds by two or more degrees, then a single vessel within 1 SU of the target point (chosen by the firer) suffers an extra 2D damage. As noted above, damage dice rolling natural 6s cause additional damage.

{| style="width: 100%;" class="article-table" cellspacing="1" cellpadding="1" border="3"
|-
| style="text-align: center;"|<u>'''Name'''</u>
| style="text-align: center;"|<u>'''Type'''</u>
| style="text-align: center;"|<u>'''Appropriate Hull Types'''</u>
| style="text-align: center;"|<u>'''Scale'''</u>
| style="text-align: center;"|<u>'''Space Range'''</u>
| style="text-align: center;"|<u>'''Atmosphere Range'''</u>
| style="text-align: center;"|<u>'''Rate of Fire'''</u>
| style="text-align: center;"|<u>'''Ammo'''</u>
| style="text-align: center;"|<u>'''Damage'''</u>
|-
| style="text-align: center;"|Mars-pattern Nova Cannon
| style="text-align: center;"|Cannon
| style="text-align: center;"|Cruisers
| style="text-align: center;"|Capital
| style="text-align: center;"|6-100/200/400
| style="text-align: center;"|12-200/400/800km
| style="text-align: center;"|1
| style="text-align: center;"|20
| style="text-align: center;"|12D+1
|-
| style="text-align: center;"|Ryza-pattern Nova Cannon
| style="text-align: center;"|Cannon
| style="text-align: center;"|Cruisers
| style="text-align: center;"|Capital
| style="text-align: center;"|6-90/180/360
| style="text-align: center;"|18-180/360/720km
| style="text-align: center;"|1
| style="text-align: center;"|20
| style="text-align: center;"|13D
|}

==='''Mars-pattern nova cannon'''===

Though Nova Cannons are quite rare, even by standards of starship construction, the Mars pattern is the most common construction template. These massive cannons—hundreds of meters in length—fire an enormous shell that echoes a traditional explosive shell, though on a much larger scale. These shells are accelerated to near relativistic velocities, causing an explosion that detonates with more force than dozens of plasma warheads.

''Core Architecture'': This weapon Component is always revealed by successful active Sensors checks—it is too large to be concealed.

==='''Ryza-pattern nova cannon'''===

This variant replaces the massive explosive shells with a highly unstable plasma-based macro-bomb. These weapons are even more power-hungry than a Stygies pattern, but are believed to be slightly more effective as well. With this additional power does come some additional questions of stability, as weaponising such a huge quantity of plasma carries its own danger.

''Core Architecture'': This weapon Component is always revealed by successful active Sensors checks—it is too large to be concealed.

''Overheating Systems'': For every five degrees of failure on a test to fire a Ryza-pattern Nova Cannon, the firing vessel
suffers one Critical Hit. If a Component is affected by the critical hit, it is always the Nova Cannon.

=='''Sources'''==
*Rogue Trader - Battlefleet Koronus (pages 15-16; 35-37)
*thedemonapostle