Vaccsuits and decompression.

[parmasson]

I am envisioning a planetary system for this Sunday.

Illa System (Mind Flayer enclave)

A binary system with two red stars, one rocky "Venus Lite" world, six gas giants, a burned out brown dwarf, and three or four asteroid belts.

Venus Lite:
Same as Venus but with a surface pressure of 420 psi , not 1200+.

To get to the point….
Would going from an exterior pressure of 420 psi to 14 psi cause trouble for someone in a vaccsuit? Would you make them decompress for an hour or two?

 

[Spinward Scout]

Three atmospheres is where narcosis can begin (it also depends on how much time is spent at that pressure - and how fast you come out of that pressure). 420 psi is 30 atmospheres of pressure. I'd personally say 10 hours of decompression. That's if the person inside the VaccSuit survives the pressure. I'll have to look that one up.

Hope that helped,

Dameon

 

[far-trader]

Hmm, I was thinking that a vacc-suit wouldn't be a problem at all. They always struck me more as hard suits than soft (excluding the form fitting tailored vacc-suits, and even then maybe not).

It's more like deep diving in a submarine, no worry with the right precautions. It's not like deep diving in a scuba suit (again unless the vacc-suit is a soft suit). The vacc-suit is pressurized to standard atmosphere and resists outside pressures (within a range).

The real question is how many atmospheres can a vacc suit stand? Off the shelf standard suits are likely to only be made to tolerate vacuum to maybe a few atmospheres. Special hard suits might go a bit further. In the same class as battle dress but built for hazardous natural environment work. There's a chart somewhere for armor value rated by atmospheres of pressure but I don't recall just where it was.

 

[Spinward Scout]

Ok, 420 psi is approximately the equivalent of a 700 foot dive (near as I can figure). Not impossible. But the only dive tables I can find online are in spanish and only go to 140 feet. I'd still go with the 10 hours. 1 hour at 70 feet (about 3 atmospheres) requires 1 hour decompression (or a 1 hour stop at 10 feet below the surface). Multiply that by 10 and it's 700 feet. I doubt that's completely correct, but it was my first guess. Unless you have a SCUBA guru in your group, I'm sure 10 hours will work. Or you could even say 4.2 hours derived from the 420 psi (if you don't mind not being technical). Either way, if you roleplay it out, boredom will set in, probably just like if they were in a decompression chamber...

 

[parmasson]

Hmmm… I wonder if the CT “hard suit” from JTAS #9, pg 47 would afford more protection?
Affords more protection in hostile environments than the “soft suits”.

 

[Spinward Scout]

Do they need to be in suits? Or can they be in a pressurized vehicle - a submarine on wheels so to speak...

 

[TheEngineer]

Standard Vacc-Suit takes up to 5 bar pressure(according to MT encyclopedia).
Maybe those 30 bar are something for a hostile environment hard suit. You would not have to mess around with decompression, too.
Anything "soft" seems not to be useful in an overpressure environment.

 

[parmasson]

Atmosphere is not breathable. Sulfur dioxide, carbon dioxide all sorts of nasty stuff. Insidious classification to be sure. Typical temperature about 200-300 degrees F.

Hartsuits seem to be the answer so no decompression is needed.

 

[princelian]

The record SCUBA dive (using tri-mix gas to lower the oxygen content) was on the order of 310 m (~31 atmospheres, which is 434 psi). Dive duration probably wasn't long - human endurance at such depths is very very short. Deeper dives have been done using specialized equipment.

Hard suits are definately a necessity on this world, and a suit puncture would be fatal extremely quickly. At 30 bar, SO2 and CO2 are going to be highly corrosive and pretty reactive. Also the suit air would probably ignite when it super-compressed, a phenomenon that happens in submarines if they lose hull integrity.

Bad place to be outside of a thick-hulled ship or ATV, and were I the Captain, I'd probably require my folks to be suited inside the ATV if the work they were doing was in any way hazardous.

However, a soft suit with the right gas mix could get a stranded crew from the ATV to the ship, if it's no more than 30 minutes.... They could survive the pressure, just not the external gases.

 

[parmasson]

"Also the suit air would probably ignite when it super-compressed, a phenomenon that happens in submarines if they lose hull integrity."

Sweet!

 

[Plankowner]

^^ Makes this old Submariner Shudder just reading it.

 

[Anthony]

Originally posted by princelian:
[QB] The record SCUBA dive (using tri-mix gas to lower the oxygen content) was on the order of 310 m (~31 atmospheres, which is 434 psi).

The record for dives is 701 meters (by COMEX SA, Hydra 10), with hydreliox.

 

[TheEngineer]

Hu, I really dont like pressure....

 

[Malenfant]

Originally posted by Kurega Gikur:
Atmosphere is not breathable. Sulfur dioxide, carbon dioxide all sorts of nasty stuff. Insidious classification to be sure. Typical temperature about 200-300 degrees F.

Hartsuits seem to be the answer so no decompression is needed.

Strictly speaking that's not really "Insidious". In fact, if the temperature is that low it's a lot more habitable than Venus is, and that apparently only rates a "Corrosive" classification.

EDIT: and for the love of god, please use "atms" or "bars" to refer to surface pressure! Although "pascals" is technically the correct unit, it's a bit much to ask for that here because it's not that intuitive... but "psi" means nothing to most people - planetary scientists and meteorologists certainly don't use it to refer to surface pressure, and "(earth) atmospheres" or "bars" just makes more sense all round to most people.

 

[aramis]

Deep pressure to 30 ATM is doable... quite survivable... and the trick is keeping the PPO2 below (IIRC) 300millibars (9in of Mercury is what comes to mind).
So in a 30000millibar atmosphere, you are going to need non-reactives; helium works but will leak away through helium's ability to tunnel through most metals (very slowly). Forget the technical term for that.

You should be fine with a 0.2% O2 mix... but the density will make respiration a bit tiring.

Current USN Experimental Fluid Filled Deep Diver suits (which look nearly identical to the ones in The Abyss, and work the same) are using a perflourocarbons, as it holds O2 stably, and ret releases it to hemoglobin, will pick up CO2, is basically incompressible, and is non-toxic... and I know they've taken them to 1000m depth and beyond. They guys I've met who have used them say the worst part is transitioning... and that they know why the mice struggle. There is a good info page on Wikipedia (Liquid Breathing)

One proposed solution to the difficulty of moving the volume is to have outlets at the bottom of the lungs connecting to the bronchial tubes, and a throat vent (Tracheotomy) for input point.

Also: current navy hardsuits with standard atmosphere are rated for 2000 feet. (http://www.mediacen.navy.mil/pubs/allhands/jun00/pg14.htm)

 

[Spinward Scout]

No decompression with the Fluid Filled Suits or HardSuits, Aramis?

 

[parmasson]

"EDIT: and for the love of god, please use "atms" or "bars" to refer to surface pressure! Although "pascals" is technically the correct unit, it's a bit much to ask for that here because it's not that intuitive... but "psi" means nothing to most people - planetary scientists and meteorologists certainly don't use it to refer to surface pressure, and "(earth) atmospheres" or "bars" just makes more sense all round to most people."

All right, fine. 3/4ths chain of mercury then.
Or 53.1 English cubits of water perhaps....
(That is 900 inches of Hg for you laymen out there)

*poke, poke*
Heheheheheheheheh. (evil giggle)

 

[Malenfant]

Well if you're going to be like that then you should measure ship lengths in Cubits

 

[aramis]

For the hardsuits, no. Internal is 1 Bar

For the fluid filled, there is no decompression time, but from what I've read and heard, you have about an hour of "drip-dry" time and some lung tissue irritation. At present, the Navy program is very experimental; the divers involved are all volunteer, all trained sat-rats, and all gung-ho. The two I talked to were UDT specialists.

At present, they have a few hours of limit time, due to exhaustion; the fluid is hard to move through the windpipe.