This question has probably surfaced before, but it has come up in our group again and as the GM I would like to know the concensus among the RT Community. Our games are heavy on exploration and conquest.

What is the effective range of an auspex on a ship when charting star systems/clusters? Is it possible to determine weather systems have no possibility of bearing life and/or material exploitation?Has anyne developped GM mechanics for this?

How have others approached this? Its just that at the moment we are playing a campaign where we are rolling for each system when we arrive (using the GM kit system creator) rather than scanning the systems long range. We still want to randomly roll for the systems, but we also want to cut down the 70 odd star systems in the area that the RT and his crew are exploring.

Hard to say, the adventures seem to say that the scanners have an effective range/effectiveness of whatever the story requires. Case in point: The starting adventure in the core book on Magoros not only has the scanners die every hour because of pulsar radition, but can't detect a ship drifting in the icy asteroid belt farthest out from the sun. Similarly, in Edge of the Abyss, no explanation is offered as to why a Rak'Gol Marauder ship suddenly catches your ship in orbit by surprise and forces them to withdraw.

http://darkreign40k.com/drjoomla/index.php/component/docman/doc_download/293-rogue-trader-star-system-generation-utility

This would make system generation much quicker. Lots of fun extra detail, too.

As to the sensors, eh. Assume maybe a day for a general scan of the system, another day for general details of a planet, years for a detailed down-to-the-metre scan.

Errant said:

Thanks. I did download the Gen Utility in the past, ...but it seems to have been greatly improved. Will save me a lot of effort. However I was thyinking more for the range of the scan. Obciously you cant get details about creatures and geography from a long range sacn outside a system, I was just wondering if long range scans from way outside the system would reveal things such as Hydrosphere, size and the number of celestial phenomena. Is there any fluff on this? (I seem to remember that the star of damocles book had somescanning in it..) or better still,,, what are we capable of doing in this day and age...

Captain Harlock said:

When the enemy spots your ship by the exhaust plume, it not only knows that a ship is there, it also knows the ship's exhaust velocity, engine mass flow, engine power, thrust, acceleration, ship's mass and ship's course. Not only can it tell a warship from a cargo freighter with all that information, but it can also tell the class of warship, and maybe make a good stab at determining which particular member of that class it is. The Space Shuttle's much weaker main engines could be detected past the orbit of Pluto. The Space Shuttle's manoeuvering thrusters could be seen as far as the asteroid belt. And even a puny ship using ion drive to thrust at a measly 1/1000 of a g could be spotted at one astronomical unit.

If it produces a heat signature, you can track it. Through our knowledge of physics, once you are tracking it and can devise its velocity and the amount of thrust, you can estimate its mass, which means you can figure out easily if you're facing a fleet of battleships or a raider. For more in-depth explanation, AKA "Why there is no stealth in space", click here

Warning: Using all the facts in this piece breaks stealth and detection in Rogue Trader. Or any space game, for that matter.

Captain Harlock said:

Today's tech can get atmospheric components at 30+ AU, so a RT ship should be able to do quite a bit better.

From the edge of a system, say 30 AU, a ship with decent sensors should be able to pick out any planets in a couple hours, then with a focused scan on an Earth-like planet, get atmospheric components, general shape of the continents, rough estimate on hydrosphere, and presence of life pretty quick. Large celestial phenomena would also be detected pretty easy, but it may take a while to pick out small or dim anomalies.

Fortinbras said:

Yeah, it does. Except that it is generally wrong. IIRC, that page assumes a chemical propellant, which behaves quite differently than a plasma propellant. It also assumes an ease in detecting a heat source that dosent exist. Something as small as a ship hull at 310K is almost impossible to detect much past the moon without alot of luck. The ability to scan for heat sources as dim as a starship over the entire sky in real time is still complete fantasy.

Please, elaborate on the properties of plasma as a form of exhaust as opposed to chemical reaction. There's one really big source I can see every time I stick my head out a window, and I don't even have a telescope.

As for the "Our engines are grimdark" argument, I recall an anecdote in BFG about a new star in the sky in the form of a Sword-class frigate or Lunar-class cruiser that was built by a primitive society mining minerals for generations. You're telling me that couldn't easily be detected?

Also, even the distance between the Earth and the Moon is, at 384,000km, way beyond anything the books offer in the way of detection.

And keep in mind I'm just showing him what the current capabilities are.

Fortinbras said:

A chemical propellant is going to be very high density and hot. Means you should get alot of blackbody radiation off the exhaust plume. A plasma drive is going to be low density with all its EM radiation coming out of either recombination of ions or cyclotron radiation from the ions travelling along the field lines of the magnetic bottle. The biggest difference would be in that there isnt anything you can to about the chemical propellant's plume, but if you recombine the plasma and detach it from the field lines before the plasma leaves the ship, all you would have is a high speed jet of cold neutral gas.

That would be the ideal situation, and probably not completely doable, but it should give you alot less of a drive plume than that web site assumes.

Note tho that 40k ship drives arent actually possible under todays theory.

Fortinbras said:

11 years actually.

Lunar class cruiser.

The sky gods collected a tribute of the feral worlds tribes metals every vernal equinox.

Seeing something in orbit such as satellites and such is fairly easy with the naked eye, the international space station for instance is clearly visible and very bright. So something the size of a lunar cruiser (not to mention its construction gantry) would be very bright.

korjik said:

So in reality plasma drives are just as hot as chemical drives, but you can neutralize them through magic. Makes sense, I suppose, but that seems like something the Imperial Navy would view as a capricious waste of energy unless running silent.

I think the key is that using the sensors and augury requires a scrutiny check. The sensors may detect the heat from your engines, but does the augur operator notice it among all the background noise and other stellar phenomena. Hiding on the far sides of planets, great asteroids, in asteroid fields, ice rings, dust clouds, etc makes it more difficult to pick out a ships signature. I assume that Rogue Trader ships don't usually have advanced cogitators to sift through all the sensor data, and mainly rely on the trained eyes of the augur operator.

Fortinbras said:

I guess what they say about a sufficiently advanced technology is true then.

Okay lets look at this again.

Desired Result:

You jump to the outskirts of a star system, uncharted before now, and want to catalog the 'planets' and other 'major bodies' in that system.

Factors:

• Imperial Technology (we can document fluff too in this regard, perhaps psykers can help too)
• Cubic AU's (Actual AU's - distance from Earth to Sun) to SCAN 'around' the main star.
• Solar radiation, orbital planes, solar occlusion of bodies in the system, the speed of light.
• Anomalies & Hazards to travel in-system.

First Impressions:

Solar systems are, by their nature, quite large. To accurately map a solar system consider that you must make very broad sweeps with sensors across a vast swath of space around a star (centering on the star at first is an idea, perhaps you can establish a plane of rotation the planets generally follow, excluding highly eccentric orbits), assuming it is not a binary or trinary. Also assume that if you do not do so in a finite period of time you might 'miss' bodies occluded by other bodies, the sun, radiation belts, et cetera and that you must make complete sweeps with sensors -many- times to catch what you missed with each successive scan, correct errors or 'ghosts' in the scans with duplicate data, and develop a 'map' of the system with any passing accuracy at all.

This means you are going to take quite a long time to complete the scan unless your technology allows for extremely quick scans over huge areas with minute errors. Even then you have to get around the sun to see what is behind it relative to your position on entry in to the area around the system at a 'relatively' safe jump point. Errors and time come into play with the limiting factor of the speed of light. A standard auspex/auger is not FTL. It has a speed limit.

Say we do a scan of an entire system. Our 'scan' signal, after many many days, has crossed the entire solar system and returned to us in the form of pings (mass detection, spectrometry, radiation spikes in the infrared, light shifting over time). You have to do it over and over again to sift out errors. Some of those signals will be distorted by God-Emperor knows what on their way back to your augers/auspexes.

Meanwhile you don't dare go rushing into the system or even through its Oort cloud at high speed unless you want to knock down your void shield (the thingy that prevents dust and micro meteorites from puncturing your hull on a good day). Mapping hazards to your vessel is very important also.

I'll think about this some more when its not past 1am in the morning. Time for sleep. This promises to be an interesting discussion.

On page 10 of Edge of the Abyss it talks about a system survey. Make note of the times and information gained.

This is very close to what I use in my games as a base (modified by player rolls among other things).

llsoth said:

For those without the book this example is for a three planet system from fluff. Durations are as follows:

3 hours for initial (passive) sweep - general information about the class, size, and locations of planets and satelites

3 hours for second (passive) sweep - atsmospheres, lifesigns, hostile presences for each planet

34 hours for third (active) sweep - no additional information

3 hours for a fourth (active-focused) sweep - reclassified a satelite as a possible starship on third planet

The distance between the outermost third planet and the sun is 16.6 VUs

In additional repsonse to the original poster:

From page 216 in the Core rulebook we know that Active Augury scans the area around the ship and takes aprox. 30 minutes. Success reveals basic and important information about planets, satelites, stars, phenomena and ships within 20 VUs of the ship, with each degree of success adding an additional 5 VUs. Silent running vessels are automatically detected within the range of the scan.

From page 217 in the Core rulebook we know that a Focused Augary of a single ship can be done at extreme range and takes aprox. 30 minutes. There are four different levels of very detailed information revealed for varying degrees of success, a failure would indicate that no additional information was obtained.

On page 213 in the Core book it clearly states in reference to SUPRISE that the fury of a plasma drive is almost impossible to hide in open space. And that sensors are prone to all manners of interference.

On page 192 in the Core book under Sensors it states auger arrays can detect asteroids and vessels from thousands or even millions of kilometers (A player would need 16 degrees of success to get 100 VUs distance with an Active Augury, so I am assuming these millions of kilometers sensors are rare or involve a different proceedure. This is not a question of scale as it specifically indicates starships and asteroids.)

On page 86 in the Core book it indicates that Scrutiny is capable determining a vessel's mass, velocity, and more when using a ship's sensors.

I think in answer to your question that perhaps there is a degree of scale and detail involved in finding what works best for you. My players have't gotten to this point yet but I think it would be fair to say that a ship on the outer edges of one system could detect the next nearest system +1 for each degree of success, maybe determine the size of the systems, and what class of star they had enough to plot it on their star charts and go to explore it later, ruling out systems that seem small or unlikely to sustain life, etc. Then once they arrive outside a new system I would have them make rolls based on Active Augary and Focused Augury, to plot the system.

Ragnar Trollskin said:

To be able to scan a system your sensors would have to be able to detect things from billions of kilometres, otherwise you'd pick up pretty much nothing, given that our solar system is, if you are at the same distance from the Sun as Pluto, 5,946,000,000km in diameter, and that's only to detect the Sun from that distance. You'd have to be able to scan even further to detect any planets on the opposite side of the Sun.

Remember that VUs are only usually used in Combat, and that VUs are an abstract unit, the rules specifically state that VUs can represent any distance the GM wants.

I think that we should not over think this one, instead go with playability. Defining an actual range to sensors is difficult at best as we don't even know what those sensors are.

I would say that basic info comes quickly and at great range. More detailed info is slower and you need to be closer. Then adjust for your vision and play style of Rogue Trader. In my games I do not want them to have to spend a great deal of time charting a system so it happens fairly fast like in the edge of the abyss example. Millage may vary though so just go with what feels right to you and will fit in with your game.

Ragnar Trollskin said:

Wait? Void Units or Astronomical Units? 166,000km seems a bit small an orbit for the outermost planet!

GalagaGalaxian said:

It is actually AU.

llsoth said:

Great! I had totally missed that bit of fluff. This answers some of my question, at least to the normal range and extent of a typical augur scan when arriving to a system.

Now if only we could find fluff about the maximum augur can range....

"The distance between the outermost third planet and the sun is 16.6 VUs"

VU's?

or real AU's?

bobh said:

*points up two posts*

Haha I must have been really distracted not to notice the other posts.