Since im trying to flesh out some rather untouched aspects of the pre-written scenario called "Dark Frontier", I've run into a situation. Namely trying to determine the speed of a gun-cutter (as it is described in the old Apocrypha: Vehicles for Dark Heresy) in Void Units.

Now according to the rules for hit and run attacks in Rogue Trader, a H&R attack can be done against an enemy vessel as long as it is within a range of five void units.

This could either mean that assault craft can travel up to five VU's in roughly 30 minutes (a strategic round/turn is described as being rouhly 30 minutes long).

OR

It means that the assault craft can travel the distance to the enemy vessel, unload it's cargo of saboteurs, let them plant bomb charges, get back to the assault craft and return to the mothership in 30 minutes.

I think it would be safe to assume that the latter of the options would be correct, since the PC leading the hit and run attack will be free to preform other actions the strategic round after the H&R. This must mean that the Player Character have returned to the ship and isn't stuck fighting on the enemy vessel.

Now, it isn't really described what sort of vessels they use for boarding actions in Rogue Trader, but since the starship combat system is sort of an extrapolation on the rules for Battlefleet Gothic, I think it would be safe to assume that you can use some stats described in BFG for correlation purposes. The normal boarding vessel in BFG would be the Shark Assault Boat, and they have a Speed of 30 centimeters per Ordnance Phase.

But the important thing to remember here is that assault craft isn't the same as a gun-cutter, BUT on the same page in the BFG rulebook it says that Fury Interceptors have the same speed as Shark Assault Boats.

According to the description, I'd say that a gun-cutter and a void interceptors are pretty similar in design (remember that Interceptors in WH40K are not the same thing as the one-manned jet fighters of today, or even analogus to X-Wing fighters of Star Wars, but rather big craft with a crew of between two and four men and the craft sporting several arrays of las cannons, anti void-craft missiles etc. etc.). Of course a gun-cutter would likely be less manouevrable and not be as heavily armed as an interceptor designed to shoot down void bombers and torpedoes, but would you agree that it would be safe to assume that a Gun-cutter would have more or less the same speed as an Interceptor, and thereby have the same speed as an assault boat or similar boarding craft? (In other words: a speed of at least 5 VU's per tactical turn?)

I assume you want to run the space battle using the RT space combat rules, otherwise it's easy enough to narrate.

Keep in mind, in BFG, that the smaller ordinance ships actually move twice as fast as the large ships. They move every Ordinance Phase. Frigates tend to have movement @ 25cm per turn, cruisers @ 20cm, and Battleships @15cm. Ordinance craft range between 20-30cm, based upon type, translating to 40-60 every turn of the owning player. So, pretty fast little buggers. I would probably take either the Speed value of a Frigate or Cruiser (or average them) and double it, and make that the approximate Speed of the guncutter.

Knowing little of BFG I will ask:

Should an assault ship be able to out run a capital ship speed wise?

Should a fighter/bomber/assault boat have a speed approaching or surpassing a Raider?

I would think that an Ordinance class vessel, as I believe BFG calls them, with the ability to close to a ship attack, and return in 30 minutes and fight off enemy fighters along the way would equate to a speed 10-15 with Maneuverability: +30 or more?

Something along these lines as a base:

Speed: 15 Maneuverability: +30

Hull Integrity: 2- 5 Armor: 2- 5

dvang said:

Yes it is the space combat rules im after. I could narrate the matter, but I thought I'd give the Void Master of the group his time in the spotlight and show of his fancy piloting skills. And like you say, I could handle it by narrating the matter, but if I do that it will be too obvious GM-fudging, and the sense of risk in manouvering past a blockade of frigates armed with turrets, and the sense of accomplishment of succeeding would sort of be lost if I just fudge it.

It is true that ordinance craft move during both players't turn in BFG, and having played a long match of BFG quite recently I agree that it should be represented.

In another thread concerning torpedoes I posted a suggestion for torpedoes having a speed of 10 (since Sword Class Frigates have a speed of 8 in Rogue Trader, and a speed of 25 cm in BFG, while torpedoes have a speed of 30 in BFG). But I wasn't quite sure of the rules in BFG back then as I am now. So giving ordinance craft a speed of 20 (void bombers being a bit slower, they could have a speed of 15) would be appropriate.

ItsUncertainWho said:

Hmm, the Manouverability modifier would conflict with Apocrypha: Vehicles if I changed it to +30 (in the Apocrypha a gun-cutter has a Manouverability modifier of +/-0), so I'll have to think about it. (I'd like to adhere to the official rules released as much as possible so it won't conflict with future releases all too much, causing a bunch of continuity errors in the campaign)

As for the Hull Integrity and Armour I'll have to get back to that when im more familiar with the sense of scale of damage different weapons can inflict. The Hit and Run action has simplified this to quite an extent, where the boarder will have to roll a pilot check modified by the enemy vessel's turret rating. If the boarder fails s/he have to turn back, if s/he fails by four or more degrees s/he is shot down (and killed depending on the GM's mood or if the character has any fate points left to burn).

It's hard to translate such an over-simplified method into appropriate Hull Integrity and Armour for an Ordnance class vessel, and exactly how many "hits" the turrets will have to inflict to shoot it down, how much damage each individual hit would inflict etc. etc.

Gonna have to wrap my head around that one. I really don't want the numbers for Hull Integrity and Armour to be arbitrary and having a bad correlation to the damage a bunch of turrets would inflict.

Tricky, tricky. But I appriciate the help and suggestions.

I'd say that Apocrypha: Vehicles' manouverability and RT ship manouverability aren't related 1:1.

Hm... having guncutters be that much faster than starships sounds wrong, when you think about it - while the latter have more mass, they've also got stronger engines to compensate. And there's no air/water resistance, which usually results in that pesky square thingy.

A possible solution would be to have the starship provide the initial acceleration for the cutter, essentially firing it at the other ship. Thus, the cutter would benefit from extremely strong engines without actually having to carry these engines...

Cifer said:

Nothing about starship movement in 40k actually makes sense in RW physics terms. In any case, it's pretty much established that the bigger ship = slower ship, otherwise Battleships would be as fast as frigates. 'Ordnance' vessels (fighters, bombers etc) are much faster than capital ships in BFG, presumably the same will apply when we get rules for them in RT.

Varnias

I had not even thought to look at the Apochrypha Gun Cuter. I just looked at the Raider class stats and compared them to the rest of the ships. The ones I listed would be along the lines of the next size class down from a Raider.

As for the maneuver score I think that the small size of the ordinance ships vs. larger ships would dictate the score, an elephant swatting a fly. Where in atmosphere the Apochrypha score would be more appropriate since the elephant is now the Gun Cutter and the fly the guardsman and his las cannon.

Cifer

An F-18 is that much faster than a carrier or destroyer.

As for using the base speed of the launch vehicle, that is too complicated and would cause the ordinance vehicles to be unable to turn around and return to ship if their carrier maneuvered away.

Cifer said:

I have to disagree with you on that one Cifer. While the void might not have any air or water resistance, any body in the void will still be subjected to inertia. Larger bodies tend to suffer more from inertia than smaller bodies do. Hence a starship would be slower than a little gun-cutter. (even the smallest starships are pretty massive after all).

Also there's the engines to consider. Even a frigate is a pretty huge super-structure, and I'd imagine that the main thrusters need considerable aid from correctional thrusters in order to travel in a straight path. Just imagine the mathematics of placing the main thrusters EXACTLY IN THE MIDDLE behind the vessel, to maximize the thrust in propelling the ship forwards. Even if the AdMech do have access to some serious sci-fi technology, I'd imagine that even they would have difficulties in such exact placement of such large machinery. Hence, unaided by correctional thrusters, the ship wouldn't be able to navigate properly. Meaning that if the captain said "Full speed ahead!" the ship would turn sideways.

Correctional thrusters would solve this, but they would also subject the ship to several opposing forces and thus limit the energy efficiency of the main thrusters, which of course would limit the overall velocity of the vessel. On a gun-cutter however, these opposing forces would be too minute to have a noticeable effect, mainly because it is much smaller.

Then there's also the balancing technicality to consider that a gun-cutter isn't a warp capable vessel, and have no way near the same operational capabilities as a frigate would. So all in all, having a gun cutter being faster and more manouevrable in real space than a frigate would be reasonable.

I have to disagree with you on that one Cifer. While the void might not have any air or water resistance, any body in the void will still be subjected to inertia. Larger bodies tend to suffer more from inertia than smaller bodies do. Hence a starship would be slower than a little gun-cutter. (even the smallest starships are pretty massive after all).

Inertia is only a problem for maneuvering, not for actual speed. And assuming that an engine's power can be scaled the same way as the size of a vessel (a vessel three times the mass has engines three times as powerful), it would remain the same, relatively speaking.

(Let's not get into that pesky Constant Acceleration = Constant Speed business...)

Also there's the engines to consider. Even a frigate is a pretty huge super-structure, and I'd imagine that the main thrusters need considerable aid from correctional thrusters in order to travel in a straight path. Just imagine the mathematics of placing the main thrusters EXACTLY IN THE MIDDLE behind the vessel, to maximize the thrust in propelling the ship forwards. Even if the AdMech do have access to some serious sci-fi technology, I'd imagine that even they would have difficulties in such exact placement of such large machinery. Hence, unaided by correctional thrusters, the ship wouldn't be able to navigate properly. Meaning that if the captain said "Full speed ahead!" the ship would turn sideways.

I'd assume the maths behind the whole thing to be the smallest problem - it's not like modern day engineering doesn't need to tackle exactly the same problem and isn't capable of microscopic precision when it comes to engineering. The rest is a matter of scale and calculation power, the latter of which wouldn't exactly be lacking when you've got the cogitators and scribes of a forgeworld at your disposal.

Correctional thrusters would solve this, but they would also subject the ship to several opposing forces and thus limit the energy efficiency of the main thrusters, which of course would limit the overall velocity of the vessel. On a gun-cutter however, these opposing forces would be too minute to have a noticeable effect, mainly because it is much smaller.

They wouldn't. While the opposing forces would be much smaller, there also wouldn't be as much force needed to move the much smaller vessel.

Then there's also the balancing technicality to consider that a gun-cutter isn't a warp capable vessel, and have no way near the same operational capabilities as a frigate would. So all in all, having a gun cutter being faster and more manouevrable in real space than a frigate would be reasonable.

I don't think a guncutter and a frigate should make any attempt at balance, considering the somewhat different costs involved.

HAH! I might have got something: structural integrity. The one thing that doesn't easily scale with size. A larger ship using scaled-up engines might tear itself apart if it doesn't use much stronger components.

There's precedent, not just in sci-fi in general, but in BFG itself as has been explained earlier in the thread. Small fighter-like craft move nearly twice as far in the same amount of time as large craft. Examples:

BFG:

- A standard Battleship moves 15cm every time it's the owning player's turn.

- A standard Cruiser moves 20cm every time it's the owning player's turn

- A standard Frigate moves 25cm every time it's the owning player's turn

- A standard Destroyer moves 30cm every time it's the owning player's turn

- Imperial assault boats and fighters move 30cm every Ordnance Phase, for each player turn, and thus move 60cm every time it comes back to the owning player's turn.

- Imperial bombers move 20cm every Ordnance Phase, for each player turn, and thus move 40cm every time it comes back to the owning player's turn.

So, you can see it is built in to how WH40k ships work that mass has an affect on speed. Don't forget, WH40k spacefacing is based loosely on the Age of Sail, so this is no surprise.

If you are looking for a technical reason... how about the fact that the larger ships have TWO drives and not one. Plasma for normal sub-space thrust and Warp for taking the ship through Warp Space. Thus, their size to power ratio does not scale upwards relatively since they have to accomadate room for both kinds of drives. Perhaps as the size goes up, the Warp Drives are required to be exponentially larger and more powerful to compensate. Thus, as a rough example, a Frigate might have a Warp Drive the same size as their Plasma Drive. Whereas, a Battleship might require a Warp Drive 5 times the size of the Plasma drive to take it through the warp safely. Thus, sub-space thrust is sacrificed to allow the ship to navigate the warp. We don't really know, but it's as good a reason as any. The point is, WH40k space travel does have varying speeds for different masses of craft, however you want to justify it.

Keep in mind that a gun-cutter is not an ordinance class vessel. Heck you could fit a few in the bays of a Fury intercepter, which 60-70 meters of engines and weapons. I don't think that an atmospheric craft like a gun-cutter could compete with true space craft.

A gun-cutter could work for extreme close in boarding, but if a rogue trader wants something useable in combat conditions they should invest in a Shark assault boat.

SomVone said:

You have a few sources confirming that?

From what I've gathered a Space Marine Thunderhawk is basically a form of gun-cutter (albeit a really heavy duty kind), and they are very much considered an ordinance class vessel. I seem to recall some instances in the Horus Heresy novels where the thunderhawks were actually used as void capable fighter/bombers.

There are several reasons why larger ships should have lower acceleration...

1. Larger structure requires larger structural support per unit volume due to strength being a function of cross-section, but mass being volume.
2. Larger drives require a volume-based linear increas of radiator area to shed heat as they scale, but surface area goes up as the square of the cube root of the ship; therefore larger ships require more and more of their surface area for radiators to keep from overheating.
3. larger ships have larger distances from the artificial grav generators; if they are in fact field effect, that means they can't compensate as strongly on larger areas.
4. larger planes of hull are more subject to internal stress fractures from higher thrust-induced metal fatigue.

It's thus reasonable that a larger ship accellerates more slowly.

Larger ships are more likely to have a higher total delta-V and thus maximum speed, due to a lower proportion of mass devoted to drives, but since we don't use realistic thrust in RT (nor in BFG), that's not a viable issue.

I am sorry if this is a stupid question. But what is a gun-cutter spesificly. I mean, I know its a landing ship, but where is it from and why use one? The Lex40k does not have anything on it.

Thunderhawks are Ordnance in BFG, and operate as Fighters/Assault boats for Space Marines IIRC. And, a guncutter *is* a void-craft as well as an atmospheric craft. In fact, many of the Ordnance, such as the Shark Assault Boats, also can operate in atmosphere. Yes, I would say that guncutters would count like ordance just as assault boats/fighters/bombers would. Don't forget that a guncutter, as described, seats 6 crew, carries multiple weapons, and has a cargo hold large enough to accomodate 30 people. That's big enough to carry an entire platoon of troops, which I think is about what a Thunderhawk carries.

InquisitorGray said:

From the Apocrypha: Vehicles pdf:

Guncutters are custom-designed heavily armed shuttles and landers, often favoured by Rogue Traders, explorers and less savoury elements. They are also serious firepower mounts, designed for space, though many can also make shuttle runs planetside as well. They are clearly combat-ready and usually covered with heavy weaponry. As such, hey immediately project and inimidating appearance, and are often useful for dangerous negotiations and smuggling operations. Most can only carry a small crew and a limited number of passengers or high value cargo, sacrificing capacity for speed, armament and protection.

To me that sounds like a cross between a space marine thunderhawk and a starhawk fighter (with the thunderhawk being bigger and have greater transport capabilities, and the starhawk probably being more heavily armed but roughly as fast as the guncutter).

dvang said:

Uhm, that's not what I can read from the Apocrypha: Vehicles. According to that source a guncutter has a crew of 2 (one pilot and one gunner/co-pilot) and can have up to 12 passengers.. Then again I guess you could cram 30 people into a cargo hold designed to carry only 12 people, but you'd have to worry a little about air supply, and it wouldn't have enough crash webbing for everyone.

Mind telling med what source you have for these figures? I've only got access to Apocrypha: Vehicles right now, and I'd like to read more. But Lexicanum doesn't know anything about guncutters.

Forsaken Bounty demo adventure for RT talks about the guncutter, which is where I got that information.

dvang said:

Alright then.

I guess that "guncutter" is a sort of catch all term for a variety of void and atomspheric capable craft, sporting a serious weapons platform and have some sort of cargo capability as well.

Still like you've said and I've proposed, I think it would be safe to assume that a guncutter is an ordinance class vessel like the Shark Assault Boats or Fury Interceptors.

Whoops I Was thinking a guncutter was basically an upgunned Valkyrie, rather then the far larger vehicle it seems to be.

Sorry.