Hi all, first post

I've recently decided to run a campaign for some friends of mine and am at a very early planning stage (I'm basically throwing lots of ideas at paper and will re-evaluate and revise them later).

My question pertains to gravity and how it, and its effects are mitigated in the 40k universe.

Is it explained anywhere how ships generate gravity for their crews? Especially given that it is generated to take effect vertically like on earth rather than a horizontal axis along the line of the ships acceleration. If so does the explanation go into detail? How do ships mitigate the g-forces generated by the acceleration? If a ship is constantly accelerating at 5g, how are the crew not affected?

I'm thinking it could be fun to have my PCs have to suffer through high gravity situations while performing evasive manoeuvres or hard burns of the plasma drives etc.

If there are good explanations of how this technology works in universe, if someone is able to link it I would appreciate it =) If not I guess it's a suspension of disbelief

It's largely suspension of disbelief. There are Gravity Generator plates, which are large slabs of metal. Their manufacture is a closely-guarded secret of some few forgeworlds, and is nearly a lost art. It's common for less endowed shipmasters to do without grav-plating throughout some parts of their ship, prioritising critical areas.

What Errant said.

Essentially, the standard science fiction trope; we have normal gravity because the special effects budget won't cover zero-G...

Gravetic technology is something that's not understood by the bulk of the imperium (but then neither is much if any technology) but clearly reasonably well understood by the mechanicus, because you rarely ever see a ship without gravity in stories or background. Equally, it's based on the same technology (in reverse) used for skimmers such as Land Speeders and their civilian equivalents, which are common(ish) amongst rich Imperial nobility.

It is disable-able, because one of the 'creeping fear' moments in Ark Of Lost Souls (a Deathwatch mission) is realising that there's no power anywhere on the ship but there's still gravity , and a mission exploring derelic ships in Dark Heresy has occasional areas where gravity has dropped out. Nevertheless, no damage results speak about losing gravity, so you're going to have to more or less hulk the ship do disable it beyond local damage.

Given that it's possible to create artificial gravity with the technology, it's not too far a stretch of disbelief to allow it to shield the crew from inertia and/or impacts. Not perfectly from gunfire (so a nearby macrocannon hit will still knock everyone to the floor), because the knocks are unexpected, and if you overrun the engines you can expect to overrun your inertial shielding a bit, pushing you into your seat. Atmospheric slingshots, etc, will also set up vibrations in the hull.

Ultimately, ships are shielded from the inertial effects of their acceleration simply because they must be. A 5G instantaneous acceleration whilst the Master Helmsman pulls some Han Solo shennanigans is fine. 5G for the few hours or so it would take to reach safe warp transition altitude above a star will kill every single person on the ship.

Thanks for the responses, that was what I figured was the case, but thought I would check =)

I've been reading books by Alastair Reynolds recently (Revelation Space series, which is excellent by the way) and in many of those they have to deal with the g-forces of constant acceleration until within a fraction of light speed. They have no faster than light travel so anybody not in sleep caskets usually have to wear mechanical frames to assist them going about their tasks =) A lot of them however have nanomachines augmenting their physiology which would perhaps help mitigate the potential damage constant acceleration could cause along with their flight suits. Seemed like it would be fun to bring some slightly more realistic physics over into RT, but I think it would cause more problems than it is worth =) Maybe I will throw it in once or twice just to mix things up if they're in a smaller craft and it becomes damaged in some way

Some interesting info on g force tolerance from wikipedia =)

The human body is better at surviving g-forces that are perpendicular to the spine. In general when the acceleration is forwards (subject essentially lying on their back, colloquially known as "eyeballs in" ^[13] ) a much higher tolerance is shown than when the acceleration is backwards (lying on their front, "eyeballs out") since blood vessels in the retina appear more sensitive in the latter direction ^{[ citation needed ]} .

Early experiments showed that untrained humans were able to tolerate a range of accelerations depending on the time of exposure. This ranged from as much as 20 g for less than 10 seconds, to 10 g for 1 minute, and 6 g for 10 minutes for both eyeballs in and out. ^[14] These forces were endured with cognitive facilities intact, as subjects were able to perform simple physical and communication tasks. The tests were determined to not cause long or short term harm although tolerance was quite subjective, with only the most motivated non-pilots capable of completing tests. ^[15] The record for peak experimental horizontal g-force tolerance is held by acceleration pioneer John Stapp , in a series of rocket sled deceleration experiments culminating in a late 1954 test in which he was clocked in a little over a second from a land speed of Mach 0.9. He survived a peak "eyeballs-out" force of 46.2 times the force of gravity, and more than 25 g for 1.1 sec, proving that the human body is capable of this. Stapp lived another 45 years to age 89, but suffered lifelong damage to his vision from this last test.

Short term shocks may be caused by impacts , drops, earthquake, or explosion. Shock is a short-term transient excitiation and is often measured as an acceleration. Very short duration shocks of 100 g have been survivable in racing car crashes.

Seemed like it would be fun to bring some slightly more realistic physics over into RT, but I think it would cause more problems than it is worth

In a universe where massive muscle augmentations and extra organs somehow means you can got more time between eating, not less, not a single flying craft looks even vaguely aerodynamic except the ones belonging to races who are advanced enough for it not to matter, city-sized ships travel between star systems by taking a shortcut through hell and then expect chain-gangs to lay broadsides precisely enough to hit targets at 20,000km, and can sneak up on people despite the thermal output of a massive fusion reactor at their heart by declaring 'silent running', and cockney fungus whose guns only work because, Wiley Coyote-style, no-one's explained to them that they shouldn't, fight cthulu-killing zombie terminators from before the dawn of civilization for the title of 'biggest threat to the galaxy', the last thing you want is to try and add is "realistic physics".

I love 40k to bits, but trust me, it can only end badly.

That said, it would not surprise me to see internal blood-vessel and cellular strengthening for tolerance of G-Force being a common augmentation for things like fighter pilots, along with augmetic heart and circlulatory upgrades.

Gravity works on voidships in much the same manner as everything else - by the Grace of the Beneficent God-Emperor, who on his Golden Throne beams out pure Rule of Cool to allow the universe to keep running day by day.

Also don't forget the Power of the Plot. Powerfull weapon it its.

Gravity Generators, Gravplates and Antigrav Struts.

AKA. Ancient Techno-Sorcery and Space Magic.

I'd have to imagine that, in "physics" terms, the grav-tech manipulates gravitons to create a sort of bubble of gravity, as if there were significantly more mass in the object than there actually is without actually adding to it's density. (now that I think about it, basically in an identical fashion to dark matter)

In terms of rules... lemme get back to you on that one.

I'd have to imagine that, in "physics" terms, the grav-tech manipulates gravitons to create a sort of bubble of gravity, as if there were significantly more mass in the object than there actually is without actually adding to it's density. (now that I think about it, basically in an identical fashion to dark matter)

In terms of rules... lemme get back to you on that one.

Close, but more sophistication is required. After all, gravity appears to work straight 'down' on each deck - there is no interaction from the gravity generators on the deck above, and a consistant 1G appears on all decks (rather than the inverse square one might expect as you move away from a single layer of generators.

I think gravity on ships is something you just respond with "Sshh. Don't ask."

It is also interesting to note that, according to the fluff, most small craft (Shuttles and fighters and such) do NOT have gravitic technology. (One product made it a fairly big deal that the Aguila class shuttle could be equipped with grav plates for the comfort of it's VIP passengers!). This would suggest that the Grav plates/ inertial dampening systems are fairly power hungry devices that need that huge fusion reactor to function!

I'm currently developing a Dark Heresy mission set on an orbital monastery (a murder mystery inspired by the book/movie The Name of the Rose ); the penitent brothers of the monastery forgo the 'luxury' of gravity plating, relying instead on centrifugal force of the rotating monastery (an enormous wheel) to simulate gravity. Hence, gravity (or the impression thereof) varies with distance from the center, with the 'hub' being Zero Gravity, the 'inner circle' Low Gravity, the main ring Normal Gravity, and the outer edge High Gravity. The monks' quarters within the monastery placed according to the 'weight of sins' they must atone for.

I'm currently developing a Dark Heresy mission set on an orbital monastery (a murder mystery inspired by the book/movie The Name of the Rose ); the penitent brothers of the monastery forgo the 'luxury' of gravity plating, relying instead on centrifugal force of the rotating monastery (an enormous wheel) to simulate gravity. Hence, gravity (or the impression thereof) varies with distance from the center, with the 'hub' being Zero Gravity, the 'inner circle' Low Gravity, the main ring Normal Gravity, and the outer edge High Gravity. The monks' quarters within the monastery placed according to the 'weight of sins' they must atone for.

I thought that the gravitational force was due to the speed at which the object was spinning, in which case wouldn't it be stronger the closer you get to the centre?

I'm currently developing a Dark Heresy mission set on an orbital monastery (a murder mystery inspired by the book/movie The Name of the Rose ); the penitent brothers of the monastery forgo the 'luxury' of gravity plating, relying instead on centrifugal force of the rotating monastery (an enormous wheel) to simulate gravity. Hence, gravity (or the impression thereof) varies with distance from the center, with the 'hub' being Zero Gravity, the 'inner circle' Low Gravity, the main ring Normal Gravity, and the outer edge High Gravity. The monks' quarters within the monastery placed according to the 'weight of sins' they must atone for.

I thought that the gravitational force was due to the speed at which the object was spinning, in which case wouldn't it be stronger the closer you get to the centre?

The center- or centre- is turning slower than the outer edge. The outer surface of a tire (or tyre) is spinning faster than the axle, even though both are making the same number of rotations.

I thought that the gravitational force was due to the speed at which the object was spinning, in which case wouldn't it be stronger the closer you get to the centre?

find something heavy (-ish) and tie it to one end of a rope/string (depending on the object).

Go outside, and spin this rope/string (kinda like a lasso I suppose) with the heavy bit in the far end. It's movement should aproximate a circle. Feel the pull on the rope? That's what substitutes for gravity.

Now try it with a longer piece of rope/string. If I recall the experiment correctly, you should actually be able feel the change in the pull of your end of the string.

As a note aside, a station has to be quite big to provide rotational "gravity" which is reasonably homogeneous.

As I recall, it must be atleast a kilometer in radius, if the difference in effective gravity felt by your feet and your head should be less than 1%. In this particular case, bigger is better

I'm currently developing a Dark Heresy mission set on an orbital monastery (a murder mystery inspired by the book/movie The Name of the Rose ); the penitent brothers of the monastery forgo the 'luxury' of gravity plating, relying instead on centrifugal force of the rotating monastery (an enormous wheel) to simulate gravity. Hence, gravity (or the impression thereof) varies with distance from the center, with the 'hub' being Zero Gravity, the 'inner circle' Low Gravity, the main ring Normal Gravity, and the outer edge High Gravity. The monks' quarters within the monastery placed according to the 'weight of sins' they must atone for.

I like this idea.... may have to steal!

As a note aside, a station has to be quite big to provide rotational "gravity" which is reasonably homogeneous.

As I recall, it must be atleast a kilometer in radius, if the difference in effective gravity felt by your feet and your head should be less than 1%. In this particular case, bigger is better

'Bigness' is not a problem in the 40Kverse. That said, wouldn't the speed of rotation be just as much a factor as size? The Cyclotron amusement park ride is quite small (compared to a space station), but it creates pseudo-gravity...

I like this idea.... may have to steal!

Go nuts. I'll try to post a map of the monastery when I get the details worked out.

'Bigness' is not a problem in the 40Kverse. That said, wouldn't the speed of rotation be just as much a factor as size? The Cyclotron amusement park ride is quite small (compared to a space station), but it creates pseudo-gravity...

Bigness certainly isn't

And speed is what matter, that's not the issue.

The issue is that is there's a difference between the g-effect experienced by your head and the g-effect experienced by

your feet, this can get extremely uncomfortable, even lethal (if the difference is large enough for long enough time). To make the difference between experienced g-effects small, make the radius of the station large.

Part of the experience of the cyclotron amusement is exactly that difference of g-effect*, but it doesn't last very long so it's not exactly risky.

* I assume. Never tried it myself. I get sick to my stomach looking at those things