dangerous decompression

also this should work the opposite way for water, incoming water should pull people and objects next to the hull into the ship/station/pipe

...Given the size of the opening and the proximity of the bodies to it, the first clip wasn't unreasonable. At 14psi the air rushing out a hole that size would push quite hard on something immediately adjacent to it, though it wouldn't push for very long without a huge space to feed it.

The second clip... I suppose if you had one of those football-field internal hangers I occasionally see built with a bunch of debris floating around right next to where the hole is then it would be possible, but the pressure differential would drop off quickly as you got further from the hole.

its a video game.

also the speed setting was turned up in those videos for effect, i've used the mod before and the actual force it applies by default is significantly less

i don't think you understand at all what i wrote when i referred to water, because i am not saying that objects should go out when water comes in. i literally said "this should work the opposite way for water"

if this wasn't a reading mistake then im not quite sure what your argument is for water since that all seems to prove my point

many people have been sucked into things because of underwater Delta-P without an implosion also occuring. https://en.wikipedia.org/wiki/2022_Caribbean_diving_disaster

also the reason air pressure is commonly thrown around when people argue against explosive decompression is because they don't know the Venturi effect or Bernoulli's principle. the air pressure is always going to be low, even at the hole since the air is moving VERY FAST. this means you can easily plug the hole, and tiny holes on craft like the ISS hardly cause any devastation and can be sealed easily. this is why it is better to look at the actual force generated by the mass of the air and its velocity rather than the air pressure itself.

in regards to clip 2:

AI prompt (im too lazy to do the math myself): "a cubic compartment containing 11390.625 cubic meters of oxygen pressurized at 14 psi is pushing air through a 6.5 square meter aperture into the open vacuum (0 psi) of space. what is the speed the air travels through the aperture? what is the volumetric flow rate of the air? what is the force and acceleration, in Newtons, acting on a 15.625 cubic meter cube with a mass of 500kg? how quickly will the compartment be completely evacuated of air?"

i assumed the room in that video was 9x9x9 light armor blocks, just eyeballing it. here are the results:

Speed of Air: 367.4 m/s

Volumetric Flow Rate: 2388.1 m^3/s

Force: 603291.5 N

Acceleration (at the start): 1206.583 m/s^2

Time until the compartment is completely empty of air: 4.26 seconds (also what space engineers calculated, based on the particle effect disappearing at ~4.3 seconds)

these are all simple calculations so if you feel that the AI is unreliable feel free to do them yourself

and for reference, a large-grid small thruster generates 1,080,000 N of force. 2160 m/s^2 of acceleration on a single light armor block (not counting its own weight).

562.5 m/s^2 on itself AND a light armored block

to our minds, this scenario seems unrealistic but you have to remember that this change is happening instantly. the engineer is instantly deleting a block, a massive hole instantly appears on a room that is fully pressurized, there is no explosion inflicting its own pressure, etc.

Tael is right in saying that "the pressure differential would drop off quickly as you got further from the hole," realistically only the block right next to the hole should've gone flying so quickly. the others would still float out too, albeit much slower.

calculating a super realistic pressure gradient for this could be costly for the game engine but a simple fall-off equation that just decreases the newtons of force applied based on distance would still faithfully simulate this enough that the average person wouldn't care at all

There is an error in the reasoning and calculation. Air pressure, and therefore pressure force (and thus acceleration force), does not act on only one side of the block, but also on the opposite side, in the opposite direction. The resulting (acceleration) force is therefore given by the difference in air pressure on both opposite sides of the block.

For the above equation to be valid, the block would have to move in a channel that tightly surrounds it and does not allow air to flow around the block – in which case the air pressure would act on one side and a vacuum would be on the other side.

In essentially the same way can be calculated the accelerating force, acceleration, and velocity of a projectile in the barrel of a firearms. All you need to know is the maximum pressure in the barrel, the weight and diameter of the projectile, and the length of the barrel. Such a calculation is, of course, only very approximate.

Translated with DeepL.com

i studied this subject for a year, the air pressure in this scenario does not act equally on all sides.

for simplicity, lets assume the front of the cube is the side that is facing towards the hole, and the back is the side facing away from the hole

the pressure on the front side of the cube is lower, because the air on that side is at a higher velocity. since the air on the front is retreating away from the cube, it also does not physically push against the cube and produce drag (there is a negative relative velocity).

the pressure on the left, right, top, and bottom sides is all going to be roughly equal and cancel each other out.

the reason a barrel is required to make a gun shoot far is because it relies on air pressure forcing gas to expand in a closed chamber. the air pressure on the front of the bullet is going to be roughly constant and may increase slightly, while the air behind the bullet is rapidly increasing in air pressure because there is nowhere for it to go

meanwhile, in this situation it would be more accurate to compare the working physics to an airfoil, where the extremely fast moving air on the front of the block and the slower air on the back result in the cube rapidly accelerating. the air pressure on the front of the cube is rapidly decreasing, while the air pressure behind it is decreasing at a significantly slower rate. yes, the air behind the cube moving much faster than the cube will ever move, so this effect only lasts ~4.3 seconds.

however, 600,000 Newtons of force acting upon the 500kg cube even for half a second is enough to send it flying at ~600m/s. to get it to fly at 100 m/s (the limit for space engineers), you only need that extreme pressure difference to persist for roughly 0.08 seconds. we have already established that the room takes ~4.3 seconds to completely drain, so the force applied by the end of those 0.08 seconds is no less than 588,837 N.

this hole is dumping 2388 cubic meters of air per second and all the air particles are moving at ~367.4 m/s

for reference: the speed of air over the wing of a Cessna 172 is only ~63.9 m/s at cruising speed, generating enough lift for an aircraft twice the weight of this cube that is also experiencing drag.

the pulling and pushing forces acting on this cube seem so extreme on paper but you have to keep in mind this is a 2.5m x 2.5m unobstructed hole that is appearing instantly on a room containing nearly 12,000 cubic meters of air, we have never tested or seen anything like this in the real world. the holes on the ISS are tiny and the ISS only contains about 1,000 cubic meters of air, which makes their flow rate significantly less and therefore only objects extremely close to the hole are rapidly pulled towards it. the pressure difference of 14 psi is also easy to block off with any solid object.

having chamber walls would actually result in this becoming less effective, as the difference in air pressure alone is not enough to move the 500kg cube fast enough that the air pressure wouldn't have completely bled off by the time the cube escapes the barrel.

summary: the air pressure never equalizes until it reaches zero (open vacuum of space) so the effect persists for ~4.3 seconds, the negative relative velocity between the air in front of the cube and the cube itself also means that the pressure immediately in front of the cube does not equalize and slow the cube down (no drag), the primary action of this movement is not that of pressure alone but also of lift generated by the movement of air, and the open air on the sides of the cube allows for the acceleration of air to generate the force necessary - so chamber walls would hinder the effect.

so no, we do not only need to know the maximum pressure in the barrel and the measurements of the projectile, these are two completely different scenarios

also a correction for one of my previous statements, i initially agreed with Tael's assessment of the pressure differential dropping off over distance, but now that i think of it this would actually not have a big effect.

the cubes at the back of the room should still be accelerating for a shorter period of time, since they have less air behind them. still, its hardly going to be noticeable, and they'll reach the speed cap of 100m/s way before then

unless there were bends and curves in the room that slowed the movement of air and generated turbulence, the air is only being slowed by friction with the walls, so the difference would not be noticeable across just 9 meters.

given that the room is shaped like a cube, if you stood off to the side of the hole and pushed yourself against the wall, you might have live a few hundred milliseconds longer as the air will have to force itself into the stream at a slower rate. still probably enough force that it would kill you almost instantly though.

https://en.wikipedia.org/wiki/Byford_Dolphin

Note: An object accelerated by gas pressure cannot exceed the maximum speed of the gas flow. If the object were to move faster than the surrounding gas flow, negative pressure would occur at the rear of the object and the object would be slowed down. So, even during acceleration, the pressure force acting on the rear of the object will decrease.

Note two – it should be possible to calculate and model how the gas will flow in the chamber when expanding through the opening into the vacuum. In other words, how the pressure and flow velocity in the chamber volume will change over time.

From this, it should then be possible to calculate more accurately how the object will be accelerated by the pressure and flow of gas.

Unfortunately, I don't have the necessary knowledge to make such a calculation...

BTW - that accident involving divers in a hyperbaric chamber... 9 atmospheres is quite a high pressure... It's roughly the pressure in the tires of a truck.

There are quite a lots videos on the internet showing accidents during wheel and tire repairs. And that's with tires with a volume of 100-200 liters (0.1-0.2 m3)... On an oil rig, these hyperbaric chambers could have a volume of at least 50 m3...

Translated with DeepL.com

I am glad that you are presenting good and logical arguments. Thumbs up!

yes, you're right about the object being unable to exceed the speed of the air.

you also bring up a good point with the acceleration, as soon as the object starts speeding up it the acceleration will drop off rather quickly, but even with that it should still be possible for it to reach 100m/s+ almost immediately

to get the math to be precise we'd have to create a lot of fall-off equations accounting for time and the changing velocity.

i might consider graphing those equations just to double check it now that you mention the acceleration fall-off, im not sure if it makes a big difference in SE, but it could limit the top speed of the cube to about ~150 m/s, which would be noticeable in SE2

and yes, the hyperbaric chamber incident is a pretty extreme example, but i was just linking it to show a popular example of explosive decompression

thank you!

Ah but there is a drop-off in differential pressure over distance. As previously stated the room in not a gun-barrel and has a diameter significantly larger than the hole, and without something adding pressure above 14psi behind the camera the total air flow in the middle of the room can't exceed the air-flow out of the hole. While the theoretical 9x9x9 room will still empty of air very quickly, there is a massive difference in push between the 14psi doing the speed of sound out of the hole, and the (per lazy back of the envelope math) .25psi doing 7m/s from the back third of the room.

yea i think you are right, probably shouldn't second-guess myself

i feel like the effects of seeing debris rapidly spew away from a ship after it takes its first hit and seeing debris spew into a submarine are definitely worth the price, but thats just me.

this doesn't apply to just airlocks, it provides greater visual feedback on pressurized compartment hits, provides Delta-P realism, and provides a minor punishment for bad compartment design.

it shouldn't be too bad for performance though, just apply an impulse to blocks/debris/items along a vector towards the first hole. this is all stuff that is already calculated everytime you fire a weapon, bump into something, walk, jump, etc.

the size and location of the hole and the direction of air travel is also already something SE1 calculcates and a simple spatial query to gather all the objects within a few meters of the hole is no worse than a damage radius calculation.

the effect does not need to be extremely realistic, and usually the first hole will be close enough to any other immediate holes that the realism of the effect wont be jeopardized by applying it to just 1-4 of those holes. even with this though, the cost of this calculation is so insignificant it wouldn't hurt to run it for every hole that appears, especially since these holes are highly unlikely to appear all within the same frame, and the room will likely be completely depressurized within 5 seconds.

thank you for your reply

Careful there, you might get someone to respond with "challenge accepted" X)

More seriously though, yes it would look good, but as the relatively tame design pictured above should demonstrate people will not hesitate to get crazy. It is certainly a feature I'd like, but when paired with the new detail blocks and the block-fracturing we have the potential for someone fitting a lot of shotguns to produce a lot of tiny holes and a lot of internal debris in a very short period of time, and if they keep SE1's ricochet mechanics (or improve on them) then those holes could be all over the place.

As such, I'm not saying the mechanic shouldn't be there, just that it may be prudent to find a way to simplify the math that still looks good when implemented.

true, i forget people can also put hundreds of guns on a single grid now

Tael - In reality, cannon fire has been used in space on only one occasion – on the Soviet orbital station Almaz/Salyut-3 in unmanned mode in 1974 (at end of misssion) . The weapon used was a 23 mm Richter R-23/261P or 225P revolver aircraft cannon (a very unique design, single-barrelled, 2600 rounds per minute). It took several tens of seconds for the stabilization engines and gyroscopes to restore the station's stability after a single shot...

https://www.youtube.com/watch?v=u6FIhn0tGTY

That said, you may need to clarify the point of your comment on the revolver-cannon. Sure, its a bad idea IRL, but this is a discussion on ship-mounted AP-shotguns and decompression in a space-game.

Just how carelessly we build ships, because the game's imperfect physics allow us to...