Did anyone else do that math? I figured out that 1 VU is equel to 240 times the speed of light.

SlumberingMage said:

Can you show your work?

I'm no maths genius, but that doesn't sound right at all.

C = 300,000 kps or 1,080,000,000 kph

VU = 10,000 km

Speed is measured in 30min turns. therefore a ship with a speed of 1 is moving 20,000 kph.

By my exceedingly crude calculation a ship moving at C would would have a Speed of about 5,400.

As a side point Voyager I is currently travelling at approximately 60,000 kph. so about Speed 3.

A ship with speed 1 = 20,000 kph

Divide that by 60 minutes, Divide that by 60 seconds

= 5.555kps

Speed 10 = 55.555 kps

Seems quite slow.

don't forget that VU isn't a fixed measurement. It's not clearly defined and depends on the situation according to the book. Therefore, math of this kind is never a certainty.

SlumberingMage said:

Your comment either absolutely makes no sense (1 VU is equal to 240*C? C isn't a distance, its a speed) or is ridiculously far off. If we're assuming you just left out several words ("I figured out that a ship moving 1 VU in half an hour is equal to 240*C), then you hilariously messed up on your calculations somewhere.

A ship moving 240*C would have an in-game speed of 12,960,000 (12 million, 9 hundred and sixty thousand). Another fun thought experiment, a ship would need to have a speed of 54,000 in order to move at the speed of light.

Another fun thingy: A ship with speed 5 would take 10,800 years to travel a single light-year. Or, to travel to our nearest Star neighbor (Promixa Centauri) it would take 46,440 years.

Jeez, that's kinda depressing...

Pretty much the only ship (Race) in the game that can move at that speed are the Necrons with their frictionless drives (the Warp and Eldar Webway don't count because they're not realspace). And even then its not a combat movement speed, its their non-combat travel speed. Their tactical speed is somewhere in the range of 'normal'. I'm not a 40k expert, there could be other races with FTL drives (the Demiurge?).

Am I wrong anywhere?

The Kroot also have a unique FTL so do the Tyranids.

crisaron said:

Erm... no they don't. Kroot Warspheres use the Warp.

crisaron said:

The Tyranids use the warp as well, they just do so in a strange manner.

Also, Kroot starship tech was initially based on Ork tech, so there's really not a lot that's "special" about it. Kroot Warspheres are big and tough, but they are hardly technological marvels.

My olde data book then suggests that spaceship 'Earth' = Speed 5.

Curse those Orks and their kunnin' calculus, able to hit a moving planet with their Speed 3 Roks!

Now that I think about it, I don't think I understand space ships having a speed limit... An object in motion will stay in motion unless acted upon by an outside force. There is no outside force in space (other than gravity, which is the weakest force in the universe), so as long as the engine is on, shouldn't a space ship's speed increase indefinitely? (ignoring, for the moment, the fact that the faster you go, the more mass-ive you become).

i.e. Voyager has been permanently accelerating since the day it was launched. It will continue to accelerate forever until it hits something or comes to close to a celestial body and gravity grabs it. Why are space ships, with superior engines, different? I know this is trying to bring logic into WH40K (or any tabletop for that matter) but I'm just curious if my thoughts have legitimacy.

Most situations can be abstracted by setting the speed in relation to whatever other ship/celestial body happens to be nearby, but it doesn't make much sense, no.

Especially when the book says that while a ship can be slowed down to a 'halt' - whatever that means in space - its forward thrusters aren't powerful enough to actually allow for a reverse.

Really, if it can slow down, it should be able for a reverse.

Darkheyr said:

What I think they are getting at is that the forward thrusters would take so much time to move the mass of a "halted" ship in reverse, at any speed greater than docking, as to render the operation worthless in open space.

You can obviously decelerate rather quick. Accelerating in reverse should be equally efficient. There is, by pure physics, no difference between reversing or simply decelerating in space.

Hence, if reverse is worthless in battle, so is trying to "stop", because its exactly the same.

WhiteLycan said:

There are plenty of things in space that can act as an outside force. Space is filled with dust for example - granted it won't slow you down more then a very marginal amount, but it'll still slow you down. There are large objects that you can crash in, as well as small objects (such as asteroids). The larger ones'll even actively "pull" you in. Gravity at work and it is far from a weak force. There is also nebulae and so forth.

A spaceship that does nothing but accelerate has a giant problem if it can't slow down or change course fast enough. Also: there's mini-meteorites in space (bullet-sized rocks or smaller) which means that your outer hull is pretty much constantly under threath of bombardment when in a solar system and flying something as huge as a imperial spaceship (and also outside of it far from uncommon). The faster you go the higher the impact of those rocks is, so your force fields' ability to cope with the impacts is increased the faster you go.

Basically: there's quite a few reasons to not want to accelerate all the time when in space. I think of the speed value as the value that the spaceship in question can maintain if they also want to be able to change heading, stop or reverse it relatively quickly or escape a gravity field of a planet/star/sattelite, combined with the maximum speed that'll overload their shields through the sheer kinetic energy released on it by the impact of mini-meteorites.

You are missing the fact that speed isn't absolute - it's relative.

Whether you accelerate or not has unpredictable effects, because your relative speed to a planet might be catastrophically different from your relative speed to that micro-meteorite. In fact, accelerating towards a planet might actually REDUCE your speed relative to that micrometeorite hitting you from behind. Or cause it to not hit it all. Shield stress caused by such objects should be rather random, no matter your speed in relation to whatever celestial body you happen to be close to. Since speed is relative, there is also no point in maintaining "slow" speed to be able to change your heading - because it always works the same. For combat encounters, all that matters is your speed in relation to your enemy. For entering orbit, its your speed in relation to the object to be orbitted. You really don't care that you are going at 4578 VU in relation to the sun, just like YOU don't care about your speed in relation to the sun right now. Or that suns relative speed to the galactic core.

Most of you are missing the fact that RT is not flying in space, it's Sailing in space.

Nah, we aren't. It's the classical 'space is an ocean' trope present in most Sci Fi settings.

I mean, RT even has the realism of fighting at large distances. Can't even do that in Star Trek or Star Wars for cinematic reasons.

It's fine. I enjoy it. But sense it makes not

I believe Larkin was referring to the principle of 'Steerage Way', where a ship's rudder loses effectiveness the slower the ship is moving, making it harder to turn. The given game mechanic does somewhat reflect this, requiring a pilot check and several degrees of success just to slow down and still be able to turn. I'd guess this is because the main engines are always firing and can't be easily shut off in only a half hour - it is an artificial star after all! The ship's thrusters may be able to counterattack the drive's power to the point it's almost stationary, but going in reverse would require damping the main drive. Fine for docking, not smart in combat.

Or something.

Exactly. The ship's current speed effects its ability to manuever, determining just how wide the turn is, because the thrusters are basically fighting against the main engines to turn the ship. While more powerful thrusts would obviously be able to turn the ship better, the output of the engines would still be the larger deciding factor in how wide or sharp of a turn the ship would be making. For the simple reason that they're bigger and more powerful than the manuvering thrusters could ever be.

Which goes the same for reversing. Considering just how massive the engines on Imperial starships are, a little set of thrusters isn't going to be able to bring the ship to a complete halt very easily. I wouldn't be surprised if it took days for a ship to decellerate to a complete halt.

Umm.. The maneuvering thrusters are not going to fight the main engines.. they can't. It would mean they would have to be more powerful than the main engines and thus you should be flying backwards.

I would suggest that you not look too closely at this as it is purely a game mechanic to give a fun and simple space combat system, instead of the nightmarish complexity of a realistic newtonian one would bring. Any attempt to justify or examine it will just lead to headaches, and physics will take a disliking to you, imposing a hefty negative modifier to aquisition rolls anytime you need something from him.

You are still all missing the concept of relative speed.

If thrusters can slow down a ship in relation to object A, they can effectively make it fly away backwards in relation to object A. In the meanwhile, they might only have cut their speed in half in relation to object B, and aren't reversing at all. A deceleration of 2 g is effectively an acceleration of 2 g - backwards. If the main engines are too powerful for the ship to reverse, they couldn't slow down at all.

Equally, turns aren't "wider" in space due to speed. Turns are always the same. Now, the time needed until you are actually flying into the direction your ship is pointing - in relation to object A - is of course dependent on your speed. In relation to object A, which again might be very different from your speed in relation to object B.

Ilsoth has it dead on, really. A realistic approach would be mindbreaking. Just like realistic space battles would be boring on TV.

Heck, realistic air fights would be boring on TV. Dogfights arent state of the art anymore.

The problem with the relativistic approach to looking at it is there can be more than 2 objects on the game board at one time, and the size of 1 VU is constant (Which is to say all the VU on the board are the same size). Take for instance if there are 3 ships on the board, 2 traveling towards each other along x axis and one traveling perpendicular to them, along the y axis... Now describe what happens when some or all decide to alter their speeds in various ways... without having physics come up behind you and stick a knife in you. The only way relativistic (not talking light speed either) speed analogies work is if each 1x1 VU square can be a different size and that size can change from round to round (even then there are problems if you do it for long enough for some of the distances to approach zero).

As to slowing down it would normally be done by flipping the ship around half way through your journey and having your main engines apply thrust.

Yup. It really would be a pain to try and rule everything by normal physics or other scientific logic. Some things could be changed I guess, such as ships being allowed a reverse, but usually its just not worth the hassle. Not to mention that most people, myself included, don't mind the "space is an ocean" trope enough to bother.

Its WH40k. I *want* those massive ships slugging it out with broadsides. Just like I want to see starfighter dogfights in Star Wars. Part of the setting, science be damned

llsoth said:

Well.. duh.

I was trying to keep things in simple terms here, it's not like anyone here has a degree in physics, myself included.

I was also pointing out that the mechanics, while lacking completelyin the finer points of the issue, still don't a bad job of representing how the ships move through space.