I wanted to start a tabletop game of Dark Heresy. What system does it use, is it a game Grid like in Dungeons and Dragons? If so, how much distance is each square, is it 1m by 1m? Wouldn't that take a large amount of table space if i were to build say, a 300m long hallway, wich really isn't that unreasonable in a universe where 5km long ships exist? Or even a planet? Is there another system i could use?

There's no grid. Feel free to convert it into a tabletop style thing for combats though with 1 meter > 1 inch. Or 1 meter > 2cm. That should fit most normal sized models well.

From what I've seen the game basically has no support for specifically tabletop play. We sometimes draw maps of our encounters so we can visualize and be more tactical in the group I play with.

Honestly, we just use a sheet with a nice grid, with an edge that looks like a data slate.

Each square on the grid represents 1m.

Then we just roleplay a situation, looking around, investigating, etc. We ask the game master (constantly lol), "ok, I go in that room... are the lights on? what do I see? is there a desk? are there any computers? etc...". Generally, our GM describes the situation and locations as far as we ask him to. If there is something of note that we haven't asked because we don't know what he's plotting, he will of course tell us "Upon entering you notice blablabla".

Generally, each one of us will say where we are headed, what are we doing, etc, who opens doors, who's checking what. Until the game master breaks the (fun) news to us with the words that bring joy and a relentless berzerker gaze on our eyes: "Roll initiatives"

Then we draw with our pencils in our grid sheet. The GM will outline the rough location, making sure to explain where cover is, walls, doors, etc. Then we get a more visual grasp of the situation, and our GM lets us specify the general location of where our characters are located at the moment the combat begins.

Then we each draw our initials stating where we are and where we are facing. "I was checking something around here, looking this way at this thing" and so on. Generally at this point, our characters notice something is not right, and our psiker does a sense presence and I'll do an auger array scan, so we can locate our enemies if we don't explicitly see them.

As combat evolves, we will tell the GM where we move, taking into account our AG bonus movement, taking turns to erase our initials and draw them at the new location.

It sounds clunky, but it's much faster done than written

Dark Heresy was explicitly designed with using miniatures in mind. Look at "The Tactical Map" sidebar p.194 of the main rulebook. At least that's the case in the old Black Industries copy I have. Dunno if they have removed it in subsequent reprintings, as FFG do seem to have been moving away from the miniatures/mapped out combat towards more narrative combat. Many of the actions are slightly less useful (or at least a bit more difficult to take account of, or the level of detail given is unecessary) in narrative combat, though it is perfectly possible to play it that way, and many do. The suggested way to play is with a grid with 1 square = 1 metre (though playing without a grid with 1 inch = 1 metre is also ok). Now, you are right that this means that large space are going to take up a lot of room. However, you are likely to only need a grid when doing close combats anyway (at ranges of 50m or less). Most Dark Heresy fights are fairly tight affairs. At longer ranges there is much less need to keep track of precise locations. Whether someone is in cover or not is not likely to change if you are shooting at them at 200m or 100m. If you do a large sweep around their cover it is still pretty much a simple thing to keep track of.

So basically, in your 300m corridor, don't use a grid until the targets are much closer to each other. However, when they get to within a few tens of metres of each other, break out the grid.

Simrobert2001 said:

Fairly easy solution for this from 2nd Edition D&D's Combat and Tactics book.

For long distance battles, use multiple scales on the same grid.

Near the characters use a 1 square = 1 meter scale. Also, near the Heretics / Xenos / Demons, use the same 1 square = 1 meter scale.

But when there is a large distance between the two groups, use a larger scale like 1 square = 10 meters long. This makes a battle between two groups of snipers at each end of your sample 300m hallway much easier to handle. Just be certain to clearly designate on the map where one scale ends, and the other begins.

Also remember that you only need to be using a grid during combat. If the characters are just exploring an abondoned ship, then a map, picture of the area, or well given description is all you need.