So I was looking through RoB the first time and glossed over it. I read it again tonight and now am wondering how does this thing work?

By the description it looks like it's more like a "placed explosive" type device that keeps going once you start it. Then it has a stat block that looks like a weapon you would aim & fire. I think i'ts the range and rate of fire that's confusing me along with the text in the entry about approaching an active one being dangerous. The range thing makes some sense with the description I guess. It sets up sympathetic vibrations in a place up to 100m away. I'm guessing it would be a BS test to "hit" the target area/structure. You just let it run the damage increases as in the descriptive text. ok

I'm assuming that there is some time to get away safely or a safe area the operator would be in or else you couldn't use one without the danger of being shaken to bits. and the fact that it doesn't destroy itself would lead me to believe there is some sort of safe zone. Also the lack of a definition of "attempting to approach" one. I'd assume that since the damage around an active one is half, that the area would also be half. I could see if you leave it long enough to increase damage it would be dangerous to stay next to it, or some other delay type thing.

But could you basicaly just not leave it continuously on and reposition it each round on a new location/target? it's designation type of "heavy" weapon meaning usualy requires bracing (but space marines don't have to) so with a RoF of S it would be a half action to "fire" it.

I guess looking at it compared to other heavy weapons the lack of any penetration means it wouldn't be broken at all to let it be used like a standard heavy weapon. it's not gonna be very good against armored vehicles and no use at all against something not on the ground. Ok so a pretty nice auto 10 damage to most hordes. It's also more req and requires exotic weapon proficiency so other weapons will be better for most purposes.

Thoughts?

I'd not really encountered such a thing in canon before, so I kind of skimmed it as well. I assumed that it was some kind of large device (perhaps like a bulky mole mortar) that was placed on the ground, set up by someone competent, and then switched on. It'd then kind of 'thump' away at the ground, eventually building up a sympathetic vibration in the desired area that would slowly crumble hardened defences by simply shaking the earth under them.

I see it as siege machinery, and something that would take a good deal of time to focus its power and function. You'd build a zig-zag trench up into range of a city's walls, set it up behind a bunch of sandbags, and leave it on for a few hours to do it's work. I certainly don't see it as a combat weapon, or something that would be any use against a vehicle. But then: I barely read it!

I think you need to aim it, it's a weapon after all. It has a Range of 100 and a Blast(10) quality. I'd say you have to aim it thus.
You set it up, camouflage it, direct it's sound emitter at the target area (use Full aim!), turn it on and leave.

Alex

Pretty much. I'd have thought it wasn't so much as a weapon to aim per se, but to fiddle with buttons; like setting up an oscillascope, or similar.

Ok, so mechanical questions that follow: what kind of roll to use? I'm assuming BS since it's a ranged weapon.

How long does this take to set up? my assumption is that the S rate of fire means a single action and you're good.

how long until it starts working? I assume immediate as above.

How far away do you have to go and do you have time to get away? and why would you not have a way to shut it off if the walls come down and you need to rush in immediately?

And if it doesn't function like this why is it listed as a weapon instead of a tool? at least the entry on melta bombs talks about the lenght of time on the timer and mentions a demolition roll to use.

I guess I'm just frustrated at the lack of any clarity.

Nathiel said:

Half Action to set-up (Ready Action), optionally a Full action for aim, Half Action to flip this thing on (Standard Attack). So: 5 to 10 seconds, 1 or 2 turns. Use of Jump Pack is advised.

Nathiel said:

Starts working immediately as you fire it off. The knowledge of remoting it must have been lost over time. Most likely the remote control at one point was worn out or got lost and nobody knew how to build a new one.

Nathiel said:

I would say yeah a BS test seems reasonable to aim it, although I would probably allow a tech use test if the player preferred. and if it fails scatter the blast as usual.

I would say taking a standard attack action to select a new target seems reasonable BUT because the escalating damage is caused by the build up of vibrations in an area reaiming it would reset it to the minimum damage it can do in my opinion. Even just reaiming it slightly would cause destructive interference in the harmonics, so just treat it as turning it off and on.

I would say it does indeed start working immediately

I personally don't think the description makes sense as it is, I think it has been written assuming that the SED affects an area around the device rather than a targetted blast area within 100 meters of the device (or farther if you assume it can fire at long range as it probably can). I would instead say that person sitting by the control panel is safe so long as the device is not targeting a point within 10 meters of itself. Any building within the blast area takes the full damage of the device per round, any person in the blast area must make a very hard agility test or be knocked down and suffer half damage. I think I would say vehicles just suffer half damage each round they remain in the blast (they count as a person but auto fail their agility test) I see it as very much an anti fortification weapon

If you don't like my opinion of this I would say by "approaching" what it means is close enough to flip switches on the control panel. so as long as you are a short distance away you are safe. It is probably a rule in place to prevent people from resetting it in combat, you just have to set it up and wait for its battery to drain

personally I think the reason its a heavy weapon instead of a tool is so that players and GM's realise how massively bulky it is. for example if a GM won't allow you to have more than 1 heavy weapon per person (a very reasonable limitation) then you cant walk around toting a heavy bolter with the SED on your back

I'd take completely the other tack with this... Mainly as I see it as more of a bit of siege machinery than a 'point and fire' weapon.

Maybe a Tech-use or Demolitions roll to set up. Perhaps even an Appraise roll as well to focus it on weak structural points. Perhaps a couple of minutes of tinkering around. Maybe up to half an hour... depending on the ground, conditions, target, et cetera.

You switch it on, and then it starts working, but does no damage immediately. It (and the clue is in the name!) escalates in power as it builds up a sypathetic vibration through the ground, in the same way that bridges start to sway.

I'd probably have it take at least a few minutes to get going. Depending on the size of the target, it could take hours (remember that it's a siege weapon).

I thought the 'escalation' part was the plus 1d10 every 10 rounds it continuously on part. It does say they can take down structures in a matter of minutes in the description and the power pack lasts for up to an hour of continuous us, so why can't you turn the darned thing off once the building is down?

Is the damage in the stat block just to structures or to all targets in the area? If you target a small but well fortified bunker for example, how much damage does it do to the targets inside? the whole damage or the ag test to fall for half every round?

Personally I think the weapon has two damage areas: the one it is aimed at and its own immediate vicinity. That's how I'd run it.

Alex