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tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Large Ship Calculations

The Zoom meeting of 2022/03/27 turned up a new requirement for development of Large Ship in the NewMars (FluxBB) environment...

There is now, and certainly will be in future, a need for calculations to be performed to address various questions that have and will come up routinely.

The concept for this topic is NOT to engage in discussion of pro's and con's of the price of tea in China.

The vision I have for this topic is as a repository of carefully performed and clear (to the high school level) calculations.

Discussion as to the accuracy of calculations is fair game and encouraged if errors occur.

On the other hand, members who contribute to this topic are expected to produce accurate work which will withstand intense scrutiny.

Fortunately, the membership already includes several who can provide carefully reasoned and documented calculations.

(th)

tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Re: Large Ship Calculations

Arising from the Zoom meeting of 2022/03/27 is a need to know the volume of the Large Ship (Prime) habitat ring.

The purpose is to determine the mass of the air (as defined by Large Ship (Prime)) to be maintained in the Ring.

At present, the ring consists of at least two levels, and that number may increase.  It will NOT decrease.

The dimensions of the cabin level is given as 19 meters wide, 238 meters long, and 3 meters thick(high).

If we have someone willing to take this on, please provide a calculation showing the volume of each level, and the mass of the Ship Standard atmosphere.

It has been decided that (at this stage) 2500 tons of mass can be allocated to structure, with 2500 tons held in reserve for consumables, passengers and odds and ends of equipment not permanently mounted to the ship itself.

Update: The mass of atmosphere should be charged to the consumables budget, not to the ship structure budget.

In either case, the mass is needed.

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

The air volume is across 3 sections of the ship
1 ring

V= π (R2 - r2) h

h= 19 m
R= 37.76 m
r= 31.76 m

V = 24,893.30448 m³

2 3 x connecting tunnels shafts

V = l × w × h

l= 27.26 m
w= 3 m
h= 3 m

V = 245.34 m³ for 1 x 3 = 736.02 m³

3 central hub.

V=Bh  or  V=πr2h

h= 9m
r=  22.86 m

V= 1,292.45868 m³

Earth air is 14.7 PSi and that is 1.225 kg/m³ but with the habitat air ready for mars being just a partial 3.5 PSI the mass will be much less.
we talked about partial atmosphere in Habitat air
and  Pressurized Air in Suits

Volume totals
V = 24,893.30448 m³   Ring
V =     736.02 m³        Tunnel
V =   1,292.45868 m³   Hub
---------------------
v = 26,921.78316       Large ship prime totals

if we were using earth air 1.225 

Mass of air would be 26,921.78316 m³ x 1.225 kg/m³ = 32,979.184371 kg or 32.979184371 mT

So 1/2 psi gives 16.5 mT of air

tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Re: Large Ship Calculations

For SpaceNut re #2 ... Thanks for giving this new topic a running start!

Just FYI ... it is easy to remember the rule of thumb for Mars habitat atmosphere, if you remember the sequence  3 - 5 - 8.

You'll find that others try to use decimals to the 10th place to make a point, but no child is going to remember the decimal points.

Each child must grow up (On Mars) knowing how to set the air for safety ... 3 psi Oxygen 5 psi neutral gas 8 psi total Habitat pressure.

As you recall from GW Johnson's postings on the subject, the choice of 3 psi partial pressure allows for use of 3 psi pure Oxygen in an EVA suite without pre-breathing.

To be fair, RobertDyck has also published on this subject, but his writings use decimals that no one can possibly remember.

3 - 5 - 8 .... just remember those numbers, and you'll be able to set your habitat dials without reading a book.

(th)_

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

I set the stage to calculate the mass of the air inside the large ship prime not a formula of its contents.

1 cubic meter of Oxygen 0.342 kg/m³
1 cubic meter of Nitrogen is 0.7996 kg

what are the mix and what are they in proportion as you can not solve it with unknowns.

tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Re: Large Ship Calculations

For SpaceNut .... thanks for continuing to develop this topic!

The prescription for Habitat Air is 3 parts (3 psi Oxygen) and 5 parts (5 PSi Nitrogen or Argon or a mixture)

The total air pressure is 8 PSI.

I apologize for not having the metric equivalents memorized.

If the end product is kilograms of mass, then the pressures will need to be given in metric units.

All that has been done before, in the archive, but is is just as easy (i suspect) to recover the data from the Internet.

however, the end result of your work will be a figure that can be used to guide designers as they weigh the contribution of atmosphere to the mass budget of the entire vessel.

I am going to be quite surprised if the mass inside the cabin ring is more than 100 kilograms,. but I'm prepared to be surprised.  The mass of the column of air above us, standing on the surface of the Earth, combines to exert 15 PSI. T ** think ** that means the mass of the air column extending up to space is equal to 6.804 kilograms per square inch.

But the pressure in a habitat ring will be artificially maintained.

I (for sure) will be ** very ** interested in the outcome of your investigation.

Update at 10:30 local time ... In case anyone would like to follow through with the calculation, here are the dimensions to be plugged into the formula shown by SpaceNut:

Outside diameter of habitat ring: 75 meters
Inside diameter (less thickness of two decks) 75 less (6*2) >> 75 - 12 >> 63 meters

Width of ring: 19 meters (this is the height variable in the examples given by SpaceNut).

The volume of the two living spaces contains a mixture of Oxygen and Inert gas (Nitrogen or Argon or a mixture).

The ratio is 3-5-8 ... 3 psi Oxygen, 5 psi Inert, 8 psi total.

The desired result is the mass of the gas inside the volume consisting of the two decks.

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

The purpose of the low pressure is to get rid of the per-breathing of pure oxygen for hours to rid the body of nitrogen....
The pressure is the ration of each that makes the air to breath.
Yes we want metric units and the example for earth is above.

from large ship topic
Atmosphere: 2.7 psi O2, 3.5 psi N2, 1.14 psi Ar, add a little CO2 and water vapour, total pressure ½ Earth at sea level (7.34 psi); Spacesuit pressure: 3.0 psi pure oxygen (Important for calculating nitrogen in ship's atmosphere. And ship's oxygen is 10% lower.)

tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Re: Large Ship Calculations

For SpaceNut re #7

The contents of post #7 are interesting and valuable, and they deserve to be published in a more appropriate topic.

This topic is about calculations, and we do not yet have a precise number for the mass of the atmosphere in the Large Ship (Prime) Habitat Ring.

I'd like to have this number in hand before the next Zoom meeting if possible.

The issue to be addressed is the matter of providing sufficient space between the pressure hull and the cabin deck.

We have extremes between 2 meters (preferred for safety) and nothing at all (the default).

The question raised was the mass of the atmosphere that would be needed if the pressure hull is set out by 2 meters, while the cabin floor remains where the pressure hull is now.

To review the factors:

Outer diameter of ring: 75 meters
Inner diamter of ring: 74 minus 6 * 2 (12) >> 62 meters
Height of cylinder to be computed: 19 meters

Air composed of 3 parts Oxygen and 5 parts inert gas (Nitrogen or Argon or mixture) for a total of 8 PSI.

The desired mass total would be given in kilograms.

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

I gave full air psi so all that had to be done was divide by 2....

Total ships air mass gives 16.5 mT of air

tahanson43206

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Registered: 2018-04-27

Posts: 19,221

Re: Large Ship Calculations

For SpaceNut re #9

Thank you ** very ** much for doing the calculation .... Would you be willing to show the steps you used?

Hopefully this topic will become a valuable resource for high school students, and perhaps a few college as well.

Showing the steps you went through will be helpful for their reference.

16.5 metric tons of air seems high, but I'm assuming you calculated correctly, so it is what is is.

In any case, adding the 2 meter outer ring for safety separation would add 8 metric tons.  That is not trivial, so it needs to be weighed against other needs, but for now, I'm assuming the safety ring between pressure hull and cabin floor can be justified.

As we have discussed in several topics, nothing is to be welded or bolted to the pressure hull.

Nothing is to be glued or otherwise affixed to the pressure hull.

No one is to be walking, skipping or jumping on the pressure hull.

Thanks again for your hard work on this important element of the design!

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

Not true but is limited to attachment points to the hull that raise those items above it to leave it with a gap to those surfaces.
Even inside a submarine things are affixed to the hull...it is limited ex floors are attached to the hull which are many through out the various classes.
We are building to this type of model even for space with inner and outer hull design.

we are doing something similar for the decks

We will be designing for things that pass through the hull items like this

this one is fiber and electrical in nature

RobertDyck

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Re: Large Ship Calculations

th: I have to contest several things you just posted. The walking surface of the habitation ring is to be applied directly to the pressure hull. That means it will be "clipped" to the pressure hull directly. The walking surface will spread out the force of standing / walking / skipping / jumping, but that will be transferred to the pressure hull. The walking surface is just a flooring material that is affixed to the risers of the pressure hull. The walking surface will prevent any point loads to the thin material between risers, but realize flooring is directly affixed to the pressure hull.

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,428

Re: Large Ship Calculations

Another part of the oxygen one board has to do with more life support

repost
I have been looking back on the use of a greenhouse as a part of life support and have made a couple posts about where nasa is Mars Lunar Greenhouse

This could be something that we not only can use as a base design onboard the ship but since the level of people that might remain on the large ship continuing to grow food we will want a similar system on the mars surface to give replacement parts and general knowledge for its use.

The buried units on the mars surface will require a sleeve for it to reside within.

Mars-Lunar Greenhouse (M-LGH). Funded by NASA Ralph Steckler Program, our team has designed and constructed a set of four cylindrical innovative 5.5 m (18 ft) long by 1.8 m (7 ft) diameter membrane M-LGHs with a cable-based hydroponic crop production system in a controlled environment that exhibits a high degree of future Lunar and/or Mars mission fidelity.

Bioregenerative Life Support
• Per Person Basis
 0.84 kg/day O2
 3.9 kg/day H2O
 50% of 11.8 MJ/day [BVAD Values, 2006]
•2000 Cal/day diet
•Buried habitat
•Six month crew change duration
•Solar for energy supply
•Autonomous deployment

Average daily water consumption 25.7 L day-1
Average daily CO2 consumption 0.22 kg day-1
Average daily elec. power consumption 100.3 kWh day-1 (361 MJ)

24 ± 4 g biomass (ww) per kWh, or
(83 g biomass (ww) per MJ)
edible + non-edible biomass

35.9 min day-1 labor use for operations

so this needs to be looked at as well not only for the co2 aspects but for the food throughput. The inner deck has a circumference of 218.36232 meters x 18 meter width x 3 or less ceiling height.
if the per person is  5.5 m (18 ft) long by 1.8 m (7 ft) we have about 363 units within the decks area that can supply just that many people fr food and oxygen recycling.