Rogue Trader RPG sneak Peaks (40k)

[Imperial Overlord]

As this relates to an rpg, I put this in games not OSF.

Fantasy Flight Games has released a starter adventure and some pregenerated characters for its Rogue Trader RPG. There's some interesting tidbits and a nice first look at some of the material.

Rogue Trader

[Vehrec]

Cool. I know at least one player who has been holding out specifically for Rogue Trader type material to play with. Now if only I could convince someone to play the psyker. The whole 'statistical certainty of having your head explode of being devoured by demons if you play for long enough' seems to sap people's willingness to peruse the awesome power of the psyker.

[Feil]

Given that the game is supposed to be about people flying around in an extremely powerful space ship, shouldn't there be some kind of space travel and space combat rules? The starter adventure seems to indicate that it is just Dark Heresy with some new character classes and a higher power level....

[Imperial Overlord]

Given that the game is supposed to be about people flying around in an extremely powerful space ship, shouldn't there be some kind of space travel and space combat rules? The starter adventure seems to indicate that it is just Dark Heresy with some new character classes and a higher power level....

There are space travel/space combat rules, according to previous updates. Starter adventures tend to be bare bones, rules wise. That's one of the reasons there no psykers PCs (they've also tweaked the psyker rules).

[Akkleptos]

And I thought this thread would had something to do with these Rogue Traders (even if remotely). Silly me! Sorry.

[Hawkwings]

Hey, I love playing the psyker. Awesome (overpowered) abilities, and the chance to become a daemonhost and kill everything, what's not to like?

[Imperial Overlord]

Hey, I love playing the psyker. Awesome (overpowered) abilities, and the chance to become a daemonhost and kill everything, what's not to like?

As long as the fate points you save not horribly dieing because of your kick ass psychic abilities keep pace with the fate points you burn to not explode from your horribly powerful psychic abilities, everything is good.

[DPDarkPrimus]

Playing with a chance for horrible things to happen randomly is WHY you play a psyker.

[Gunhead]

I'm somewhat interested how they've managed the powerlevel in Rogue Trader. I'm less than thrilled about DH in general, comes off way too medieval shit in space to my taste. From the preview it does look RT will use the same system laid out in DH. Which means I'll propably get this just to rip off ideas.

-Gunhead

[Imperial Overlord]

New tidbit out, about designing your ship for Rogue Trader. Unfortunately, it also reveals they completely dropped the ball when it comes to ship speeds. Acceleration in single digits gravities. Ouch.

[Vehrec]

First homerule, sight unseen. Ships now will have their acceleration increased by adding three zeroes to the end of it.

[Feil]

Mass, too. The listed masses are off by a factor of about 100, assuming density comparable to modern warships.

Your adjustment to acceleration may be too high. A ship crossing the solar system in 1 dayfrom a V of 0 to a V of 0 - which seems about right to me for a fast ship - would take a sustained burn of 320 gravities. So adding two zeroes would be appropriate, but three probably excessive, unless you want ships zipping around star systems in a span of hours.

I wrote a long-email commenting on and explaining the errors in mass and acceleration figures to FFG and suggesting formulas for the generation of realistic ones. I'll let you know if I get a reply.

[Aaron]

Well this looks interesting, definitely worth a purchase even if I just use to steal ideas for DH.

[Imperial Overlord]

40K tends to have ship accelerations in tens or hundreds of gravities. So far most of it looks good (I've already stolen Amputator Rounds for a DH adventure). I hadn't done any math on the masses (although they seemed to low) so I refrained from commenting.

[Feil]

40K tends to have ship accelerations in tens or hundreds of gravities. So far most of it looks good (I've already stolen Amputator Rounds for a DH adventure). I hadn't done any math on the masses (although they seemed to low) so I refrained from commenting.

Mass / (length*beam^2) for density, compare to real world substances and structures. For instance, if the Jericho-class, the first listed hull, was made entirely of styrofoam, it would mass about 18 megatonnes. The listed mass is 9 Mt.

[Connor MacLeod]

New tidbit out, about designing your ship for Rogue Trader. Unfortunately, it also reveals they completely dropped the ball when it comes to ship speeds. Acceleration in single digits gravities. Ouch.

Someone's been reading James Swallow's Blood angels novel. Too bad though that that novel has battle barges pulling upwards of 12 gees lollol

40K tends to have ship accelerations in tens or hundreds of gravities. So far most of it looks good (I've already stolen Amputator Rounds for a DH adventure). I hadn't done any math on the masses (although they seemed to low) so I refrained from commenting.

Or hundreds or thousands of gravities (or more.) It really depends on the source or author. Flight of the Eisenstein IIRC had a big ass vessel moving at hundreds of gees (the phalanx, NecronLord did those calcs) and Execution Hour had the Planet Killer pulling 100+ gees on its own (and it makes the Emperor class look agile.) Nevermind various sources that had ships crossing stated sitstances or inter-system dinstances in a matter of hours (Ghosts novels, Grey Knights novels, etc.)

Mass / (length*beam^2) for density, compare to real world substances and structures. For instance, if the Jericho-class, the first listed hull, was made entirely of styrofoam, it would mass about 18 megatonnes. The listed mass is 9 Mt.

What about hull thickness? Its a merchant ship not a warship, and we dont really know its exact dimensions or shape. Most are roughly hammerhead or bulky, but this ship seems to have a length/width ratio alot higher than some other vessels. It might also be measuring the WIDEST point (the engine and nose sections tend to be wider than the main bodies to some degree anyhow.) And hull thicknesses will hardly be uniform either.

If it is off, it won't neccesarily be off by much, and it DOES say "approximately" so its not as if its an exact figure in any case.

[open_sketchbook]

An unloaded cargo ship with wide open, mostly featureless cargo bays making up a great deal of it's bulk might end up wieghing very little for it's size.

[Feil]

Mass / (length*beam^2) for density, compare to real world substances and structures. For instance, if the Jericho-class, the first listed hull, was made entirely of styrofoam, it would mass about 18 megatonnes. The listed mass is 9 Mt.

What about hull thickness? Its a merchant ship not a warship, and we dont really know its exact dimensions or shape. Most are roughly hammerhead or bulky, but this ship seems to have a length/width ratio alot higher than some other vessels. It might also be measuring the WIDEST point (the engine and nose sections tend to be wider than the main bodies to some degree anyhow.) And hull thicknesses will hardly be uniform either.

If it is off, it won't neccesarily be off by much, and it DOES say "approximately" so its not as if its an exact figure in any case.

With an irregular hull shape (with fins or something), one could conceivably construct a mental picture of the space ship that was slightly more dense than styrofoam.

An unloaded cargo ship with wide open, mostly featureless cargo bays making up a great deal of it's bulk might end up wieghing very little for it's size.

The warships have comparable densities. Presumably either loaded and empty mass are similar or the listed mass is the loaded mass.

[Imperial Overlord]

40K tends to have ship accelerations in tens or hundreds of gravities. So far most of it looks good (I've already stolen Amputator Rounds for a DH adventure). I hadn't done any math on the masses (although they seemed to low) so I refrained from commenting.

Mass / (length*beam^2) for density, compare to real world substances and structures. For instance, if the Jericho-class, the first listed hull, was made entirely of styrofoam, it would mass about 18 megatonnes. The listed mass is 9 Mt.

I know how to do the math, I was just too damn tired at the time.

[The Yosemite Bear]

Just tell me mon-keigh, when can I join you as team sniper, no I don't want to mention why I got kicked out of the Craftworld?

[Feil]

Got a reply, which was polite but definitively a "no, nothing is going to change". I've asked for permission to post the exchange in case anyone is interested. Some things he said that might be of interest to potential 40k analysts are that 40k ships are supposed to take several weeks to navigate star systems (which matches the given acceleration figures, although it does not match the other figures derived in the 40k analysis thread) and that the ships are supposed to be that light because of hi-tech materials and structures. Any metal which is flexible enough to withstand changes in temperature and the sheering forces of a turning miles-long spaceship, conductive enough to withstand proximity blasts from nuclear weapons, strong enough to withstand compression forces from ramming other spaceships, and yet considerably less dense than styrofoam is worth making note of....

[Connor MacLeod]

Got a reply, which was polite but definitively a "no, nothing is going to change". I've asked for permission to post the exchange in case anyone is interested. Some things he said that might be of interest to potential 40k analysts are that 40k ships are supposed to take several weeks to navigate star systems (which matches the given acceleration figures, although it does not match the other figures derived in the 40k analysis thread)

Some sourcres do support that, others don't. It may be these engines are a brand peculiar to this portion of space (I'm assuming RT will be like Dark heresy and take places in a specific sector), or it may simply be one of those ship qualities that vary (since its been established in 40K that ship performance can vary dramatically depending on where its built, rebuilt, refurbished, etc.)

Alternately, the single digit G's might be a conditional factor (IE during combat, or something, where power allocation must be balanced between different systems.

and that the ships are supposed to be that light because of hi-tech materials and structures. Any metal which is flexible enough to withstand changes in temperature and the sheering forces of a turning miles-long spaceship, conductive enough to withstand proximity blasts from nuclear weapons, strong enough to withstand compression forces from ramming other spaceships, and yet considerably less dense than styrofoam is worth making note of....

Its 40K. Magic materials are not an unknown here. You can use daemons to shape charge nukes, for crying out loud. Having a low mass material probably owuld be some osrt of advantage (easier to push the ships, and achieve higher accels.)

That said, I'm not sure I'd call it styrofoam. A very low density material, true, but hardly styrofoam. (I got something approaching Wood density, but I was still fudging things there. I don't have an precise internal volume for the Sword firgate.) The Sword is very very narrow, tall, but much of its length is also rather slim (there's the beaked prow which is fairly huge, and of course the engines.) "approximately" 6 megatons isn't that far off.

And I will say its a far cry from starship masses as in the novels (millions of tons for a 4 mile battleship, hundred thousand tons for a destroyer, 400,000 tons for an unknown warship, and that was an Abnett novel..) This source isnt neccearily the first to establish the "millions of tons/megatons" idea either. The Iron Hands novel had a strike cruiser at that range, and a Mars class battlcruiser in wolf's honour (albeit damaged IIRC) was "tens of millions" of tons.

In any case calling them approximate (s well as being fairly vague in what KIND of mass we're tlaking about) offers plenty of fudge factor anyhow. At best we can treat them as nice, definitive lower limits.

[Feil]

Got his permission to post the e-mails, so here it is if anyone is interested.

To: Project Leader, Rogue Trader Roleplaying Game
Concerning: serious technical errors on pp 194-195, Rogue Trader Preview 2

Dear sir or madam,

I am dismayed to note that the space ship masses listed in the Hulls section of the Rogue Trader Preview number 2, pages numbered 194 and 195, are low to the point of physical impossibility. All of them are impossibly low, but I will comment exclusively on the first one.

The ship''s dimensions are listed as 2.25km long, 0.3km abeam. Assuming that the ship is about as tall as it is wide, this gives us a total volume of 2.25km*0.3km*0.3km = 202500000 m^3.

The listed mass is 9 megatonnes, e.g. 9000000000kg. This gives the space ship a density of 44kg/m^3

This is 50% less than the density of Styrofoam.

A useful method to compute accurat e figures is to compare with real-world ships. The American Nimitz-class carrier weighs roughly 1 megatonne and has a volume of roughly 330m*50m*15m = 255000 m^3, hence a density of 3900kg/m^3.

Applying the formula

mass = LENGTH*BEAM*BEAM*3900kg/m^3

should give realistic masses for the space ships in Rogue Trader.

This formula would give the ship I have been considering (the Jericho-class) a mass of 790 megatonnes.

---

The acceleration figures given are also extremely low, although since these have no immediate real-world analogue, it is harder to say by how much. However, assuming that the players should be able to cross a star system and come to a stop in about one day, we can draw some conclusions:

The Solar system is roughly 80 astronomical units in diameter.

Crossing the Solar system in 1 day and being stationary at the end of the journey requires a 1/2 day burn to the mid-point of the solar system, a 180 d egree turn, and a 1/2 day burn to the far point of the solar system.

Crossing 40 astronomical units in 1/2 day (mathematically equivalent to crossing 80AU in 1 day and being stationary at the end) requires a sustained acceleration of 320 gravities.

Acceleration rates can be calculated by the formula: (acceleration = distance / time^2).

I humbly ask that you revise the rulebook for the coming Rogue Trader roleplaying game in light of this information.

Sincerely,
[redacted]

[redacted]:


Thanks for your note regarding physics in Rogue Trader. It's fun to examine the difference between fantasy and reality, and always great to see the wealth of real-world experience that our players have to offer.


In the 41st Millennium, spacefaring ships use extremely lightweight yet strong materials in their construction. For the most part, humans use an adamantium/ceramite alloy. In addition to the great reduction in mass, ceramite conducts very little heat, making it extremely well-suited to engines and well as helping to make the ship's armour highly resistant to heat- and energy-based weapons.


As for the acceleration question, warp-capable starships in the 41st Millennium do not use FTL drives as theorized by today's astrophysicists. The "Warp Drive" in the Warhammer 40,000 universe exists only to rip open a hole in reality through which to fly the ship, and the standard engines do the rest, steered by specialist Psykers known as Navigators. Speeds and times do not exist within the Warp as they do to observers in realspace.


As with all RPGs, these exist as mere guidelines. Your Game Master will figure out how long it takes your ship to get from Point A to Point B based on many factors. As J. Michael Straczynski once said about the speed of one of his fictional starships, "It moves at the speed of plot."


Yours,


Jeremy Stomberg
FFG

[redacted]:


One more bit about star system crossing: Journeys through "realspace" are actually lengthy affairs, with a starship taking weeks or even months to traverse a star-system. Such a voyage can take just as long as a voyage through the warp to a distant star, (and sometimes longer, due to the capricious nature of the warp).


Jeremy Stomberg
FFG

[Feil]

Incidentally, crossing an 80AU solar system at a sustained 3 gravity burn with an initial and final V of 0 relative the star would take 10.5 days.

[DPDarkPrimus]

There are unofficial calculations of time spent in warp vs real time based on a White Dwarf article that I've used for Dark Heresy before to get rough estimates of travel time, but the variances of both are enough that for the most time it really is up to the GM to decide how long a trip takes.