I was wondering what you all thought of the rules for Starship movement, and if you'd change them in any way?

Now, correct me if I'm wrong but (as I read it) at the start of each turn you choose to travel half or all of your Speed regardless of what you did last round, is this right?

So if you choose to travel half speed (e.g 4) and "Adjust Speed" down by 2 (now travelling 2 VU), by your next turn you again have to choose whether to travel 4 or 8? This seems pretty screwy to me. Surely unless you burn retro's or thrusters you'd continue at your current speed, no? So if last turn I chose to travel 2 VU and this turn I didn't Adjust Speed then surely I'd still be travelling 2 VU? There is no real reason why my ship would suddenly jump back up to 4 Speed causing me to have to roll again to drop it back to 2. My players would have a fit if I told them that's how it works!

Maybe allow the Pilot to make a Speed change of 1 as a free un-rolled action, and any more must be rolled for on a 1VU per Degree of Success basis? Also, if using Flanking Speed you only take the highest success rolled. For example last turn I got 3 successes causing me to add 3 to my current speed. If I try to eek out even more power from the engines, I'd need to roll 4 successes to get an extra point of speed, then 5 successes to get another one, etc, but once at these speeds I maintain them until I choose to change them.

Any thoughts on this?

Also, what are you thoughts on turning? Does it seem right that you turn a full 90 degrees all in one go as a standard turn? I was thinking of having it where you turn 45 degrees half way through your movement and the final 45 degrees at the end. Also, if you're in a cruiser with a turn of only 45 degrees then you make this turn in the middle OR at the end, your choice.

What this would mean with the Come to New Heading manoeuvre is that you could turn 90 degrees instead of 45 degrees at the middle and end of your movement to represent it being a tricky manoeuvre (you having to make a Pilot Test).

Again, any thoughts?

How would/do you approach the speed and turning rules if different to the RAW, or are you happy with them as written?

And finally, how would you keep track of the combat in a reasonably realistic way without using a map and counters, but just using descriptions?

Any and all ideas are welcome!

he system that appears in Rogue Trader is an abstraction of the Battlefleet Gothic rules (the 40k fleet game). One of the key features there is that, unless you purposely 'Burn Retros', the ships always move at least half movement whether you want them to or not. I have always liked this on two accounts:

Firstly, it accurately portrays the bulk of the ships involved and the lack of inertia in the void. My first reaction to reading Battlefleet Gothic way back when was similar to yours now:

"Why, if I burn retros and come to a standstill this turn, am I forced to get back to moving next turn?"

I have come to see it in regards to the 40k Background that the massive plasma drives you see on the rear of any Imperial ship are clearly (and indeed visibly on the models) hundreds of times larger than any of the ship's retro thrusters. These huge drives can't simply be stopped and started in a battlefield situation. You can burn retros for a time to cancel some of your forward momentum, but once the retros cut out you will begin to accelerate again.

And secondly, I enjoy the tactical aspect. Unlike in ground based combat, where you can see the position of yourselves and your enemy at a glance, in space you constantly have to think a couple of turns of movement ahead. Manoeuvring to set up a broadside while all members of the combat are in constant motion is key to the game. In essence this whole system is designed to capture the feel of Sail-Powered Navel battles, and such ships had limited control of speed.

As for turning, I generally like the rules as they are. Its all about getting in a position to apply the firepower you have, while avoiding the firepower of the enemy. The options for turning as they are mean that the players have to choose wisely.

Having said all that, I am making a few minor tweaks to the rules for the Navel aspects of my game. Notably that any ship that isn't in motion (if it has adjusted its speed to zero, for example) becomes considerably easier to hit, which also applies to spacestations. A few other elements of Battlefleet Gothic might migrate across too, which should be fine as at least some of my group have experience with it.

I can't speak on doing this without the models and board/map, as I already have far too many appropriate models. I guess you'd be best running it fully abstract from a point of view within the player's ship. General range and direction of target and a battlefield layout is all you really need them to know.

That went on longer than I expected for my first post here (long, long time lurker), but I finally felt like I had something to say.

Welcome to the fray Gideon. And please accept an honourable mention for a very well written and clever first post.

OP: From the view of my studies in physics I agree with you. Ships should have an acceleration value, rather than a speed. Maximum speed should be limited in theory by relativistic factors and in practice by difficulty to maneuver, since there is (practically) no friction in the void. There should be a bit of a rule for how easy or tricky it is to turn on and off that acceleration, this might include retro thrusters or more likely turning your ship around to use the main motor to decrease your speed with your acceleration value. It should be quite easy to rotate your ship around its point of balance, but that would only change what part of your ship was to the front. There should be a proper 3d-vectorbased system for placement, movement and shooting, it is allright if this does not simulate relativistic effects. That would be such an awesome game if to play spacecombat in a SCIENCEfiction setting.

However, the 40k world is governed by the rule of cool much more than the laws of physics. It is way much more grimdark and omnious with mighty spaceships slowly gliding towards eachother guns blasting, than doing loads of math over relativistic effects. Most players have a "gut feeling" for how sailing and rowing ships look when in combat, due to popular media. On the other hand I can recall only Bablyon 5 as an example of popular media that depicts the physics involved in spacecombat properly ( and I have honestly not played the space combat game based on the B5 franchise, maybe chek that out?). And as Gideon pointed out, RT is based on BattleFleet Gothic. BFG s based on Man-o-War that was about ship combat in the WHfantasy universe. A lot of the rules stayed the same.

All that said, if you manage to houserule the RT system to have acceleration and proper inertia, rather than stupid set speeds, I'd be more than happy to steal it and use it in my campaigns.

It is daffy, isn't it, since you can shut the drive down for 'silent running'...

What I do is simply have them moving at the same speed at the beginning of next turn. This way a ship using 'silent running' can 'drift' forward at it's former speeds while not running the engine. But, yeah, the BFG and RT to an extent both suffer from the law of anime that says "Constant Thrust equals constant velocity".

It's hardly loads of maths though is it? All you need to do is "remember" what speed you were traveling last round... and thats really it. Still, a very interesting and welcome post

I think I just have the problem that there's all that technology and the only 2 speeds a plasma drive has are "Half" and "Full"? I understand it comes from a board game but it doesn't sit right with me and I know for a fact it won't for my players. And in case anyone's thinking it, "much of the technology was lost" doesn't fit either... they're basically adjusting the thrust port to allow more or less propulsion through (like a jet fighter), or adjusting the amount of fuel being pumped through (like an accelerator), or maybe even adjusting the number of people running on the Speed Treadmill... or all of the above! If they can do it for land vehicles, titans, fighter jets and god knows what else they can do it for a Starship. After all its not rocket science! (even though it... erm... IS rocket science.... um).

I like the idea of silent running but still moving at your last known speed. But how long would you say it would take to re-start the plasma drives? A couple of hours (4 turns) ?

In fact how long would people reckon on the complete prep time of a ship from fully off to Ready for Action?

Speaking as someone with a basic knowledge of physics that neither knows nor cares about anything more complicated than terminal velocity, I don't think there's that much wrong with the system. The main problem is that it seems to be almost entirely hoiked from Battlefleet Gothic and not much work has gone into it to change it for Rogue Trader.

In Battlefleet Gothic ships had to move at least half speed and up to full speed. Turns could be split into smaller turns over the course of movement as long as the ship had moved far enough. Thus a cruiser could move half speed, turn 10 degrees, move a little again and turn another 35. For some reason this has been left out of Rogue Trader - go figure.

Now we are talking... threadmills! I need treadmills for my next ship design.

Remembering speed from last turn is a good idea, combined with a small span of acceleration values and breaking values. Breaking value should be lower since all the engine exhausts sit at the back. Lets say 0-4AAU (Arbitrary Acceleration Units) for acceleration and 0-1 for breaking. That works awesome when travelling in a straight line. However, when I want to turn my ship... Let's say I'm travelling at 14ASU (Arbitrary Speed Units) in the direction that we have arbitrarily named "north". Then I use my side trusters to rotate the ship 90 degrees right around it's center of mass (for the simplicity of calculation, we assume this is done instantly). This will keep me travelling at 14ASU in the same direction as before but with my port side in the direction of travel. Then I apply my 4 points of acceleration in the direction my prow is now pointing. I will now travel 14ASU "north" and 4ASU "east". So far not too bad, if you want to calculate the total speed you only have to do:

total speed = SQR( (northward speed)^2 + (eastward speed)^2 ) This can be done on the fly with a simple calculator, as long as the component speeds are in 90 degrees angles to eachother. But this total speed is not that important... It would of course be nice to know the value and direction of this new line of travel. For that we need to bring out the Trigonometry. But we don't need to know that, as long as we keep thinking of the ship as having two distinct speeds, one northwards and one eastwards. We just need to move it the correct distance in both directions each turn, while applying acceleration as needed.

If I then turned my ship 122 degrees to my right to bring my huge port cannons to bear on a target, I would have to apply my 4 points of acceleration in the direction of... *smoke from my ears* ... ok, lets break down this application of acceleration into one north and one east vector. We need a trigonometry able calculator or a sine table. The built in calculator in windows can do sine functions. so sin(angle of deviation from north)*acceleration = acceleration aplied to the ships northward speed. Same goes for eastward speed. So you will need to remember speed in two dimensions "east" and "north" for example. You will need to calculate each application of your acceleration along these two dimensions.

If you want to keep it simple. Restrict your spaceships to be positioned in distinct 45 degrees angles from North (like that chaos star you know) So they can be facing North, Northeast, East, Southeast, South etc Then, when the ships acceleration kicks in you do this simple math:

Is the ship pointing in one of the four main directions? If yes, apply full force of acceleration in that direction. Ships pointing west will of course subtract their acceleration from their eastward speed. A negative speed eastward will mean the ship is moving to the west.

Is the ship pointing in one of the combined directions? Apply 0.7 times of that acceleration to both the component directions. 0.7 is an approxiation of 1/(sqr(1^2+1^2)) = 1/sqr(2) So an acceleration of 4 in the NorthEast direction would increase speed by 2.8 to the north, and 2.8 to the east. Feel free to make a small list of these calculations, so you don't have to break out your calculator in the middle of the game. Some clever ideas I got. Restrict big heavy ships as to how much they are allowed to turn each round, their side trusters might not be able to handle that much. Name the directions "terrawards" and "spinwise" or something similarily inspirational instead of east and north.

If you are feeling adventurous, please go ahead and allow 22.5 degree positions as well, but I won't tell you the multipliers for those vectors.

And thus we have decently simulated a flat plane inertiabased combat system. It is only a slight increase indifficulty of math, but a big increase in the difficulty of visualisation to expand our gameboard to be three dimensional.

I hope I didn't math-crit you to death now...

After reading that last post, I'm just about ready to leave the rules as written!

Quite a few misunderstandings of physics in this thread.

For one, there's plenty of "inertia" in space. What it lacks is friction. Secondly, there isn't a terminal velocity in space (again, because there's no friction to cause drag).

The best space rules I've ever seen as far as realism goes were the ones from FASA's BattleSpace.

EDIT: Mellon's post is perfect, and BattleSpace actually utilized all that physics.

I don't so much want complete realism, just a little MORE realism, but I think I know what house rules I will and won't be using now.

Cheers everyone!

Lord Commissar said:

I think this is the first time ever someone called one of my posts perfect. I'm actually blushing here. Thank you! *happy*

It's always been my interpretation that your ships speed represents what ever the current speed is. So if your speed is 4 vu, you can move that up one or down one using the adjust speed action. From that point on your speed is now considered either a 3 or a 5 until u take further actions to change it. Half speed would represent turning on the retro's to slow the ship down for manouvers, and then if u chose to move full, than the retros are switched off.

as far as turning, smaller ships like transports, raiders and frigates turn 90 degrees, but larger ships can only turn 45 degrees per turn (standard turns without special manouvers).

dragonmarkeddm said:

There is no keel, there are no wheels, no rudder or anything like that wich can turn the linear movement into a circular (that is what most planetbound vehicles does when they turn). There is no friction that will slow you down. With a spaceship you can only push in a new direction. The problem I have with the current rules for turning is that the ship should really keep going in the direction it went before turning, just having the side of the ship in the direction of travel. Then the engines should start accelerating the ship towards the new direction, while it keeps floating with unchanged speed in the old direction of travel. Unless you have a big bunch of gravity, such as a planet or a star to slingshot around... but that's another discussion.

There is really no reason to have a max speed on a ship as long as you stay a bit below the speed of light. Speed of light would mean travelling roughly 3.5 AU per 30 min round. This means a one way trip from Holy Terra to Mars when they are on maximum distance (opposite sides of sol). As long as you go slower than this, you don't need to worry about max speeds on spaceships, they just keep accelerating. I'm not sure how AU would translate to voidunits. Does someone know?

Mellon said:

I don't know exactly how much distance a VU is meant to cover, but I remember that it was variable so it could really be anything. An AU, however, is approximately 24 million km so, convert the VU and what ever actual distance it represents to km and divide 24 million by that number.

VUs are about 10,000 km square.

The "you will drift the amount of your current speed and then can move from there" method people are talking about makes great sense. However, the "drift and move" system makes it very easy to overshoot and take ages to get back in range.

Given the 2d nature of my tabletop, for "drift and move" I'd have two vectors, x and y, or long and short, based on the shape of my dining room table. For each vector, you have a speed and a direction, up or down, left or right. As the GM I have the most mass, so down is to me. right is to my right, and so on.

Each turn being 20 minutes, you could make a case that turning a 2km vessel 90 degrees (or more) could cause problems for the grav plates or some other hand waving tech reason. Thus if you want to slow down, it takes two turns to four turns to reverse the direction of a small ship and apply full speed in the opposite direction.

In "drift and move" you should be able to change facing without applying thrust. Your vectors would stay the same, just your facing changes.

However, all this will make it very easy to go off the map, and VERY easy for a ship with equal thrust to escape. The RaW, which has a very nautical feeling, will keep the combat on the table longer and make it easier to stay engaged.

One idea I had was a zoom factor that cut the speed in half and make every VU twice as big if the ships drift away from each other but are not disengaging. When they get close enough, you zoom back in and use the speeds as listed.

I think we'll have to play some variants out to see how they work in play.

The rules as written are NOT vector motion mechanics; they are lifted directly from Battlefleet Gothic.

Yes, they really have to make effort to not go forward; it's totally unrealistic, but it's the way the ships have worked.

Yes, there is no realistic reason the ships should be hit with a maximum speed, but hey, that's what BFG does, too.

It makes for a good minis game, even if it's REALLY unrealistic.

aramis said:

I can well believe these BFG movement rules are more fun than vector motion. I remember playing a traveler game (Mayday?) that used vector motion in a realistic manner, and 95% of the turns were spent turning around to get in range again.

Nojo509 said:

Mayday. Or Bk2 of the [Classic] Traveller RPG. (Which is gridless, but otherwise same as Mayday.) Brilliant Lances was the TNE version...

I've seen the same way-too-much-time-maneuvering... when people had too high an initial engagement velocity. In Traveller, and in Full Thrust, and in B5W...

BFG is fun, if anime-esque. Better, it's simple.

40K:RT always felt like GW's homegrown Traveller Universe (so many tropes are borrowed from Traveller, and they were a Traveller Licensee before they launched Warhammer; 40K arises as they ended their license... the announcement of MegaTraveller killed almost all extant Traveller licenses.)... but Traveller ship combat was one area where Traveller was über-cumbersome. And BFG ran the exact opposite direction: Playability uber alles.

RTRPG is likewise playability focused from what I can see.

aramis said:

But... Rogue Trader RPG isn't a minis game... is it?

I think making the rules a liitle more realistic doesn't have to delve into the world of vectors, inertia and quantum mechanics.

Is it too much to ask for a rough turning circle rather than turning 90 degrees in one go like you've just stepped out of an episode of Automan (wow! Blast from the past! I bet many of you don't remember Automan! ).

I can picture the scene in-game now.... (goes into a wavy flashback sequence)

Pilot: "We can't outrun them my Lord"

Captain: "If we can't out-pace them, then we'll just have to out shoot them! Hard to Port!"

Pilot: "But sir, we're currently travelling at 120,000 kph! Do you think thats a good id..."

Captain: "Just do it man or I'll have your head!"

The ship lurches 90 degrees in the blink of an eye, sending crew slamming into the ships interior walls, as the ass-end of the vessel snaps off and continues on it's old course.

Pilot: *Sigh*

I think the "overshooting and having to turn back, thus loosing several turns of action" problem that an inertia based system would give rise to is easy to solve by two changes. The first is longer weapon ranges. The second is some player experience in predicting combat situations. I don't mind that it is easy for my enemy to get away from me during spaceship combat, if their ship has a better acceleration. The void is huge. I'll just go bomb their homeplanet until they come back and fight me :-)

But I must agree that not all roleplayers would enjoy the tactical challenge that comes with a true vector system. So the current BFG-based system probably works much better if you feel like the rules often gets into the way of the roleplaying. I know that when I introduce these inertia movement rules to my player group, I will have them run a few mockup battles with different setup of ships beforehand to let them get a feel for the system, because it is quite counterintuitive.

Graver said:

Looking at the various combat systems, it can be.

In point of fact, the rules provide enough detail to break out models and play out both man to man and ship to ship as minis combat games.

I ran many of my combats in DH without minis, but the big intense ones, minis on maps. Same with WFRP. (Tho' for REALLY big battles, we broke out WFB...) Most detailed combat systems in RPGs are written very much like minis games; Inquisitor (GW MInis game) is almost to being playable as an RPG. The line is often blurry between minis games and RPGs.

RTRPG has mimicked the way ships operate in BFG most probably because so much of the definition of ships in the 40K universe is BFG...

Good point Aramis.

I think it's all about having fun and enjoying the game.

I've had plenty of great battles in Star Wars RPG, and the movement of ships there both in-game and movies are totally unrealistic. Yet, space combat was engaging and fun, that's what matters.

The RT setting has a similar concept, since W40K has always been more fantastic than realistic.

The simple set of rules work well, and all the better to be able to concentrate on telling a great story and getting the action going rather than counting numbers.

PS: This reminds me of the classic discussion of old, 'How on earth does a Dreadnought fit in a Rhino'.

Graver said:

Actually I would bet a lot of people are going to be using bfg minis for this game. I know my group is.

On another note, I am a collector of spaceship miniatures rule and have played pretty much everything out there right now. I can say without a doubt that vector systems, while accurate, are not really all that fun, especially for new players or anyone that just wants to "shoot at cool ships". There is a dedicated group of people ie. engineers, that have an interest in this sort of brain exercise but for the vast majority 'Cinimatic Movement' works the best by far.

I'm not saying BFG is the best way to go. In my opinion the game is total crap. But it way more accessable to people than vector based games.

ps. For my money the Babylon 5: A Call To Arms game is the best space miniatures combat game made. It takes its base from Full Thrust and fixes the boring spots of BFG to make a really exciting and accessable game for veterans and novices alike.

LEGION3000 said:

Thank you for that review. I'm sure going to check it out.

Rest of your post was a good read as well. It's nice to hear from someone with a lot of practical experience in the matter.