Ship's Atmosphere

[BackworldTraveller]

A ship has 1dTon of atmosphere aboard per dTon of ship space.

a) If the vessel wishes to depressurise, where does it put that volume of gas? There is no specific component in the vessel design that specifically accepts that. Admittedly, if 1dTon were liquified, it would be 10 litres or so, but as a de-pressurisation method, that isn't ideal. At 135 atm pressure it could be stored in a 100l tank - but that would be relatively heavy and dangerous in battle.

b) How long would it take to de-pressurise by saving the air?

c) Air recycling systems suggest that the cost to replace the scrubber filters, chemicals, etc. is part of the two-week maintenance cost for staterooms. Most systems have a considerable safety margin. What is the life of a scrubber before it becomes useless? Is 4-Weeks reasonable? or 4-Months or longer?

d) Assuming that there is a volume of storage capacity for air, if a ship loses all its atmosphere how many times can it replace it? Or is venting the cargo hold to on-load the cargo a serious threat to the wellbeing of all aboard?

 

[tjoneslo]

A ship has 1dTon of atmosphere aboard per dTon of ship space.

a) If the vessel wishes to depressurise, where does it put that volume of gas? There is no specific component in the vessel design that specifically accepts that. Admittedly, if 1dTon were liquified, it would be 10 litres or so, but as a de-pressurisation method, that isn't ideal. At 135 atm pressure it could be stored in a 100l tank - but that would be relatively heavy and dangerous in battle.

https://en.wikipedia.org/wiki/Diving_cylinder#Working_pressure

A quick google of SCUBA equipment shows standard TL-7 tanks are rated for 200 to 300 bar. Using more advanced, high TL materials, you can probably achieve higher pressures. so 100 liters per dton of atmosphere space may be a low estimate.

b) How long would it take to de-pressurise by saving the air?

Given the presence of a Fuel processor which is capable of gathering plasma hot hydrogen, and cooling and refining several 10s of tons into liquid in a a few hours, I suspect the limits lie in the ability to move the air to the compressor as part of the air system in the ship.

That may be an interesting option. The air isn't compressed. It's cryogenic liquid and stored next to the fuel tanks. You would need at least two different tanks (Nitrogen and Oxygen are liquid at different temperatures), plus a small tank of extra constituents.

c) Air recycling systems suggest that the cost to replace the scrubber filters, chemicals, etc. is part of the two-week maintenance cost for staterooms. Most systems have a considerable safety margin. What is the life of a scrubber before it becomes useless? Is 4-Weeks reasonable? or 4-Months or longer?

Some of this will depend on how poor quality of the air you are breathing you are willing to accept. There are a few members here who are or were members of submarine crews. They would be much more able to talk about what poor quality but still breathable air is like.

d) Assuming that there is a volume of storage capacity for air, if a ship loses all its atmosphere how many times can it replace it? Or is venting the cargo hold to on-load the cargo a serious threat to the wellbeing of all aboard?

It would not surprise me that part of the maintenance cost for the life support system is making sure the tanks holding the atmosphere are fully charged with a standard atmosphere, and given the size of the tanks, there may be three or four full charges.

 

[Condottiere]

You could store the pressurized air next to the hull, and have blow out panels in case the tanks are breached.

 

[Timerover51]

A somewhat related question for the thread. For ships built on either Thin or Dense Atmosphere planets, what atmosphere pressure is used on board the ship?

If they use Standard Pressure, i.e. atmosphere 6, to someone used to Thin Atmosphere, that is going to feel like Dense Atmosphere, while to someone used to Dense Atmosphere, that is going to feel like Thin Atmosphere. The same would hold true for passengers from either a Thin atmosphere or a Dense world.

From the atmosphere chart on page 90 of Book 3, T5.10 rule book, it looks like the following is the atmosphere breakdown on a Standard Atmosphere world. The chart does make for interesting reading.

Dense equates to a minus 1000 meters, or about 1.13 atmosphere.
Standard is at the surface, so 1 atmosphere.
Thin starts at 1000 meters, so about .9 atmosphere.
Very Thin starts at 8000 meters, so about .37 atmosphere.
Trace begins at 12.000 meters, or about .19 atmosphere.

The Thin figures strikes me as a bit too low, and I would go with more like 5000 to 6000 feet, about 1500 to 1800 meters, or about .83 to .80 atmosphere.
I might also go with about 20,000 feet for Very Thin, as you need supplemental oxygen at that altitude.

The data on atmosphere verses height come from the following:

https://www.mide.com/air-pressure-at-altitude-calculator

 

[whartung]

Yea, none of those seem too limiting for healthy beings, not to the point of needing extra equipment. There may be an acclimation period, but it's not sea level to Everest kind of difference.

Mind, I've never been in "dense" atmosphere, only "thin" (11,000+). Mild bout of altitude sickness, but it passed readily.

 

[Garnfellow]

My players have a ship built by a Vegan concern, so the environmental defaults are low gravity, low pressure oxygen-nitrogen atmosphere and temperature of 95 degrees or so. Any time the computer glitches the ship reverts to the default.

 

[Fovean]

My players have a ship built by a Vegan concern, so the environmental defaults are low gravity, low pressure oxygen-nitrogen atmosphere and temperature of 95 degrees or so. Any time the computer glitches the ship reverts to the default.

Love that, great world building there.

 

[McPerth]

A somewhat related question for the thread. For ships built on either Thin or Dense Atmosphere planets, what atmosphere pressure is used on board the ship?

If they use Standard Pressure, i.e. atmosphere 6, to someone used to Thin Atmosphere, that is going to feel like Dense Atmosphere, while to someone used to Dense Atmosphere, that is going to feel like Thin Atmosphere. The same would hold true for passengers from either a Thin atmosphere or a Dense world.

From the atmosphere chart on page 90 of Book 3, T5.10 rule book, it looks like the following is the atmosphere breakdown on a Standard Atmosphere world. The chart does make for interesting reading.

Dense equates to a minus 1000 meters, or about 1.13 atmosphere.
Standard is at the surface, so 1 atmosphere.
Thin starts at 1000 meters, so about .9 atmosphere.
Very Thin starts at 8000 meters, so about .37 atmosphere.
Trace begins at 12.000 meters, or about .19 atmosphere.

The Thin figures strikes me as a bit too low, and I would go with more like 5000 to 6000 feet, about 1500 to 1800 meters, or about .83 to .80 atmosphere.
I might also go with about 20,000 feet for Very Thin, as you need supplemental oxygen at that altitude.

The data on atmosphere verses height come from the following:

https://www.mide.com/air-pressure-at-altitude-calculator

In MT:SOM, when talking about life support, the old hand told he had his engineer to slowly adapt the gravity to the target one, so that the passengers will get used to it while in travel.

I guess the same would be used with atmosphere, so helping to aclimatate the passengers, and probably avoiding the height illness-like a lower atmosphere pressure would cause (or the opposite, if a higher one).

 

[Black Vulmea]

Yea, none of those seem too limiting for healthy beings, not to the point of needing extra equipment. There may be an acclimation period, but it's not sea level to Everest kind of difference.

When I was a park ranger I dealt with HAPE cases in the Sierra Nevada, above 2500 m; you don't have to be at 8000 m to have significant symptoms.

The crew of the Wreck in my solo game recently dealt with this, departing a world at 1.23 G and 162 kPa for a gas giant satellite at 0.31 G and 46 kPa. With only eight days to acclimate, a few passengers showed symptoms of AAS - acute acclimation sickness - an condition well known to starship medics. Acclimate - some far future flavor of acetazolamide - is taken as a preventative, and stewards are tasked with making sure passengers are hydrating and if necessary using compression masks to ease the adjustment.

There's also something called the Buriina protocols, used to acclimate Imperial Marines in a hurry, but they're applied by Navy doctors in controlled conditions, and as Captain Mul noted, free trader passengers aren't jump troops.

In the real world, ideally you gain no more than 500 m per day based on the elevation where you sleep for the night, which is about 5 kPa on Earth, between 2500-6000 m, and about half that at higher elevations.

Gamelords' The Mountain Environment goes into this in some detail for different atmospheres.

 

[Timerover51]

My players have a ship built by a Vegan concern, so the environmental defaults are low gravity, low pressure oxygen-nitrogen atmosphere and temperature of 95 degrees or so. Any time the computer glitches the ship reverts to the default.

I am certain that default would make passengers from a Cold, Dense Atmosphere planet very happy.