I'm making some ships for xenos races and instead of making them insanely big with hundreds of thousands of crew I took more to Star Wars. Thus I have some hard hitting small ships. To make it fair and so they aren't immediately blown out of the void I've taken to using size like for the ground battles so it's harder to hit them.

I was wondering if anyone had made similar rules that I could steal from

for example: I have a ship -20 to hit on a ship approx 1/4 the size of an imperial frigate

On ‎08‎/‎09‎/‎2017 at 3:50 AM, hereth37 said:

I'm making some ships for xenos races and instead of making them insanely big with hundreds of thousands of crew I took more to Star Wars.

In fairness, this is kind of a default part of the 40k setting; a warp capable starship is almost invariably star-destroyer-sized or bigger.

On ‎08‎/‎09‎/‎2017 at 3:50 AM, hereth37 said:

Thus I have some hard hitting small ships. To make it fair and so they aren't immediately blown out of the void I've taken to using size like for the ground battles so it's harder to hit them.

A ship 1/4 the length of an Imperial Frigate would be...what? about 300, 400 metres long?

I wouldn't necessarily give them a size-based penalty to hit: if you can hit a Viper-class Sloop (950m long) as easily as a Repulsive-class Grand Cruiser (7,400m long), then clearly the static size of the target isn't a determining factor in accuracy in void war (which, given that you are aiming for a 'bulls-eye' a couple of square kilometres in size several tens of thousands of kilometres away, is kind of obvious in hindsight)

However, your little super-gunboats are presumably very, very manoeuvrable. What I would do is focus on evasive maneuvers:

By default:

Evasive Maneuvers: -10 maneuver test. For every degree of success, enemies suffer -10 penalty to BS tests to hit. Evading ship suffers same penalty

Make Evasive Manveuvers something your gunships can do as a 'free manoeuvre' (make it a special property of either the hull or the plasma drive), and limit or reduce the penalty to its own shooting.

Oh - one counter-comment: Said ships are going to be relatively weakly armed (because it physically won't have the space to carry all-up warship macrobatteries beyond maybe a couple of mounts (say, 1 strength 1 or strength 2 battery), but also weakly armoured. Obviously the basic rules account for this, but you might also consider making them vulnerable to turret fire at closer range; a ship that small is not going to be enormously more heavily armoured than a Starhawk Bomber, so sufficient defensive fire might actually cause the odd point of damage...

18 hours ago, Magnus Grendel said:

clearly the static size of the target isn't a determining factor in accuracy in void war (which, given that you are aiming for a 'bulls-eye' a couple of square kilometres in size several tens of thousands of kilometres away, is kind of obvious in hindsight)

However, your little super-gunboats are presumably very, very manoeuvrable. What I would do is focus on evasive maneuvers:

By default:

Evasive Maneuvers: -10 maneuver test. For every degree of success, enemies suffer -10 penalty to BS tests to hit. Evading ship suffers same penalty

Make Evasive Manveuvers something your gunships can do as a 'free manoeuvre' (make it a special property of either the hull or the plasma drive), and limit or reduce the penalty to its own shooting.

You make a good point. I like the test idea, but if the evading ship has the same penalty, then dodging well makes it impossible to hit for either party. I know why you would want that, moving fast makes it harder to aim for you too, but with an already 40-30% chance, decreasing it more seems extreme.

4 hours ago, hereth37 said:

I like the test idea, but if the evading ship has the same penalty, then dodging well makes it impossible to hit for either party.

If that's a built in property of the 'gunship drive' or 'gunship macrocannon, though, you can put in whatever exemptions you like.

This thing clearly won't have a proper battery of macrocannons because it can't - it physically won't have the space. So if you're going to invent a weapon mount, why not invent one that deals with this problem?

Hereth-Pattern Macrocannon

Single Macrocannons mounted in a powered turret, these weapons are designed to be used singly or in pairs on very light ships. Their turrets use massive servo-motors to allow the whole cannon assembly to be laid onto a target quickly and to keep it stable whilst the firing ship performs the extreme manoeuvres generally required to survive a combat environment.

Strength 1

Damage 1D10+2

Crit 5

Range 5

Special: Fast Tracking - this weapon suffers no penalty for Evasive Manoeuvres carried out by the firing ship.

Space 1

Power 2

SP 1

8 hours ago, Magnus Grendel said:

Hereth-Pattern Macrocannon

Single Macrocannons mounted in a powered turret, these weapons are designed to be used singly or in pairs on very light ships. Their turrets use massive servo-motors to allow the whole cannon assembly to be laid onto a target quickly and to keep it stable whilst the firing ship performs the extreme manoeuvres generally required to survive a combat environment.

Strength 1

Damage 1D10+2

Crit 5

Range 5

Special: Fast Tracking - this weapon suffers no penalty for Evasive Manoeuvres carried out by the firing ship.

Space 1

Power 2

SP 1

Doing all the work for me again.

One of the 'quests' I've given my players is to help conquer a system "For The Imperium!". But this would mean they could only help in small skirmishes on the side. So I was thinking about how to implement something similar to above in regards to Imperial ships. However the whole size to distance thing you said earlier makes sense, so maybe a negative to hit for moving fast? Like -20 for running on land.

In the lore there's often frigates groups doing strikes on larger ships and getting away with it, but I've never seen rules like this before. Is it fair to say with the vanilla rules that the larger the ship the better? How could I implement this so that the tiny frigate they have can do something in a larger battle with big ships?

51 minutes ago, hereth37 said:

One of the 'quests' I've given my players is to help conquer a system "For The Imperium!". But this would mean they could only help in small skirmishes on the side.

Depends on what size of ship they've got....if it's an existing group of players, though, with a transport or frigate, then probably, yes.

Note that it needn't be small skirmishes so much as 'special operations' - Rogue Traders are obviously totally legitimate individuals and would not have any skills acquired during dubious and illegal pursuits.

Which is a shame, because an armed, upgraded small warship or armed transport with a crew experienced at silent running, avoiding patrols, deceiving their way through inspections, etc, would be very useful in delivering special operations teams, sneaking in to attack orbital auspex installations, laying mines, sabotaging ships at dock, and generally sneaking about the place the same way a smuggler normally would and delivering explosions and Militarum Tempestus commandoes rather than illegal xenotech.

51 minutes ago, hereth37 said:

So I was thinking about how to implement something similar to above in regards to Imperial ships. However the whole size to distance thing you said earlier makes sense, so maybe a negative to hit for moving fast? Like -20 for running on land.

Again, specifically it's Evasive maneuvers.

• Flying in a straight line doesn't make you hard to hit, no matter how fast you go (this is why you can shoot down torpedoes)
• Being a small target doesn't make you hard to hit (see shooting at a sloop versus a grand cruiser)

It's a combination of size, range, speed and erratic movement.

Okay....wordy explanation incoming:

You can't 'dodge' a las-bolt, because it arrives before you see it coming (it arrives at the speed of light, after all!) and lances and energy macrobatteries are not a million miles away from that in speed either. Besides which, 15 VU is only half a light second - even at a few G acceleration, you can only be a couple of metres off the position inertia would have put you in if you were just 'coasting'. Certainly a kilometre-long ship can't 'pull up' enough to clear its own silhouette and generate a miss.

What you can do is make yourself hard to aim at. Macrocannons are huge things that make WWII battleship cannons look like popguns. Traversing them takes minutes (it's a half-hour combat round, remember) and the bearings have to be 0.001 degrees radian accurate in laying the guns to hit a 1km target at 10,000 km range.

That's what 'evasive manoeuvres' represents - randomly varying acceleration and heading a bit - not enough to change overall course but enough to make it hard to predict where you'll be...say ten minutes from now?

which is why I'd say a small ship with a manoeuvrable drive (your gunships) should be good at evasive manoeuvres - they have to move a smaller distance off their course to clear their own silhouette, and they can probably do it faster to boot.

The PCs ship....I'd leave it as is. Trust me, with a decent crew and PCs, even a Rogue Trader in an armed transport (a Vagabond or Carrack, anyway) can easily take on and beat a generic frigate. The PC's higher stats and abilities (especially master of ordnance) is a huge advantage.

51 minutes ago, hereth37 said:

In the lore there's often frigates groups doing strikes on larger ships and getting away with it, but I've never seen rules like this before. Is it fair to say with the vanilla rules that the larger the ship the better? How could I implement this so that the tiny frigate they have can do something in a larger battle with big ships?

Not as black and white as this. Larger ships are definitely not always better.

A frigate group can easily beat up a big ship well-handled, but in one of two ways:

• Working together. If you have access to Battlefleet Koronus, there are rules in there for NPC warship squadrons. This is perfect for your needs. Essentially, as long as they stay in formation, they co-ordinate their attacks, and attack as if they were a single ship. This means:
  • The target's void shields only apply once for the squadron instead of once per ship
  • The same is true for the target's armour.
  • Only one roll to hit is made for the guns, but for every battery of the same type after the first, the squadron gets +10 BS and the battery's effective strength is increased by 1.
• By using torpedoes. fast destroyers with torpedo tubes have historically been a nemesis of battleships, because they can launch from the very extreme edge of the battleship's firing range then fall back whilst the torpedoes close to attack range, and battleships lack the speed and manoeuvrability to evade torpedoes that only need to get within 10,000km to trigger their terminal guidance - and in Rogue Trader, said torpedoes also penetrate void shield, leaving only the ship's defensive turrets and armour as a means of defence.

1 hour ago, hereth37 said:

How could I implement this so that the tiny frigate they have can do something in a larger battle with big ships?

Magnus already wrote the answer that I support: work in group and use your speed to hit-and-run tactic.

The size should matter, but except when the ship is a sitting duck (does not accelerate), it would be always used together with acceleration. Thus since Maneuverability is abstract, you may pretend it's already factored in. E.g. in a debris field what matters is how quickly you can get the ship's cross-section out of the collision course, and whether it can be done would depend on

Maneuverability ~ a/r

- where a is acceleration and r is radius of cross-section (from the given direction). Granted, it's crude, because proportions differ, MoI differ and thrusters can be distributed differently, so different ships would need different a/r rates for different maneuvers. But the rest of the model is not a good simulation either.

On ‎26‎/‎09‎/‎2017 at 10:29 AM, TBeholder said:

The size should matter, but except when the ship is a sitting duck (does not accelerate), it would be always used together with acceleration. Thus since Maneuverability is abstract, you may pretend it's already factored in. E.g. in a debris field what matters is how quickly you can get the ship's cross-section out of the collision course, and whether it can be done would depend on

Maneuverability ~ a/r

- where a is acceleration and r is radius of cross-section (from the given direction). Granted, it's crude, because proportions differ, MoI differ and thrusters can be distributed differently, so different ships would need different a/r rates for different maneuvers. But the rest of the model is not a good simulation either.

Nevertheless, it's a good enough 'shorthand' - it's what my waffly explanation above was trying to get at; "dodging" is moving your cross-sectional area out of the way of your opponent's planned firing solution (not the shot itself - Rogue Trader engagements happen at such a short range by speed-of-light standards that you're not going to dodge a shot once it's fired) between the time they tell the gun crew where to point the barrel and the time they pull the trigger.