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Old November 23rd, 2018, 05:22 PM
nobby-w nobby-w is offline
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Default A NASA study about space habitats plus related docs

This is a study that I turned up with some google-fu on the topic of population and facilities on space habitats. It covers a lot of ground and makes for some interesting reading.

https://settlement.arc.nasa.gov/75Su...Contents1.html

This is a discussion of the efficiency of various crops for life support and food production.

https://pdfs.semanticscholar.org/f1f...32afe48e8b.pdf

From a little google-fu, it would appear that a human needs about 400-600g of oxygen per day on average.

https://www.quora.com/How-much-oxyge...CO2-is-exhaled

Some NASA bumf about space habitats

https://www.nasa.gov/pdf/146558main_...%204_10_06.pdf
http://www.marsjournal.org/contents/.../Lange2003.pdf
https://www.nasa.gov/pdf/176994main_..._HSE_TG2-1.pdf

Another study about space habitats

http://space.nss.org/media/NSS-JOURN...-Transport.pdf

Some discussions of life support using algae

https://ntrs.nasa.gov/archive/nasa/c...9670025254.pdf
https://www.researchgate.net/publica..._Myers_to_Mars

A discussion of the thermal control systems on the ISS

https://www.nasa.gov/pdf/473486main_...s_overview.pdf

A discussion of the power system on the ISS

https://www.edn.com/design/power-man...--power-system

Some observations
Once upon a time I had occasion to stay in an apartment complex in Jakarta called Kalibata city. This was a large complex with something of the order of 10,000 apartments. There were a lot of shops and other facilities on-site (including an underground shopping mall), giving it the feel of what living in an arcology might be like.

In this facility, studio apartments were typically about 18m2, two bedroom apartments were about 33m2 and three bedroom apartments about 43m2. The designs were fairly space efficient, but a bigger budget for folding fittings and using 3 dimensions more might reduce the floor space significantly. Note: all the apartments had a wet floor bathroom with a shower, toilet and basin, plus a little balcony. People often put a washing machine on the balcony.

With appropriate use of technology, one might surmise that a studio apartment might fit in a bit less space than that. Some folks in Hong Kong live in really small apartments, and my wife's stepfather has a house with 3 stories of about 2m x 3m floor area (he built it himself).

In traveller terms, one could surmise that a studio flat with high-tech folding fittings might fit in a space as small as 2-3 dtons (about the size of a stateroom) but would represent just a few percent of the total space taken up by a resident.

Executive summary:
About 1,750 m3 (125 dtons) of space per long-term permanent resident, including agriculture and recreational space. Recreational space is about 30% of the total. If you added starport facilities, power plants, cooling,1 fuel tankage and suchlike, the total would probably be more like 200dt/resident or more.
About 40-50 m2 of the most efficient hydroponics to meet oxygen requirements. Food requirements are considerably greater, somewhere about 150-200m2 per person depending on the crop mix.
230kg of algae culture per human for oxygen regeneration, estimated 2.2 m3 per human for the apparatus.
If the diameter is too small, coriolis force can be enough to cause nausea on spinning habitats. Conventional wisdom suggests something in excess of 1km to get the gradients and spin rates small enough for this not to be an issue.
A population of 100,000-200,000 is needed to support an economy. A population of 500,000 or more is needed to support a skill base sufficiently diverse for a long-term self-sustaining culture.
Radiator panels can dissipate about 400-500 watts per square metre using ammonia as a coolant.
The ISS has a crew of up to 7 and power consumption (including all science payloads) of 70-90kw. This suggests a power consumption of the order of 10kw per resident. A habitat with a full economy might need more than that depending on the industry present.
The ISS has approximately 2,500m2 of solar panels supplying a peak capacity of 120kW. This suggests about 50w per square metre.
For each resident, you would require something like 20m2 of radiators and 200m2 of photovoltaic arrays (assuming efficiency equivalent to that deployed on current spacecraft, which converts at around 38% efficiency)

This suggests that a self-sustaining (culturally and economically) space habitat would start in the region of 100-200 million dtons. For 500,000 residents it would require 10 million m2 (10km2) of radiators and 100km2 of photovoltaic arrays. Think big.

1 Cooling gets glossed over in Traveller, but it is a significant problem on a space station. Dissipating the heat from a large nuclear reactor is not a trivial undertaking in space. Also, power usage by artificial gravity systems gets glossed over, but they're gravitics right? Perhaps centrifugal gravity and large PV arrays might be popular for larger space habitats simply because the demands of dissipating heat from the power to supply artificial gravity systems could be too great.
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Last edited by nobby-w; November 25th, 2018 at 09:34 AM..
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Old January 27th, 2019, 09:55 PM
wellis wellis is offline
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So would massive O'Neill cylinders be the type of space colony most useful for housing large populations?
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Old January 28th, 2019, 04:11 PM
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So would massive O'Neill cylinders be the type of space colony most useful for housing large populations?
Some variant on the design would likely be the best approach unless you want to postulate some fairly pulpy mcguffinite in your setting. The pattern has the following advantages:
  • It has two contra-rotating cylinders; as long as the bearings hold out it can mix and match zero-g and centrifugal gravity sections.
  • Aluminium is strong enough to use as a construction material and both aluminium and titanium can be mined from lunar regolith. If you place the colony in the L4 or L5 position, you can deliver construction materials with a mass driver on the surface of the moon, and they won't need excessive delta-v at the receiving end. You can catch the materials with what is essentially a giant kevlar net. This means that the millions of tons of construction materials can be delivered to their destination cheaply - in fact it will be more expensive and use more power to refine the aluminium than it would to fire it to a rendezvous at the L4 or L5 point of the moon with a mass driver.
  • Even if you have gravitics in your setting, centrifugal gravity is going to use less power. Either PV cell arrays or radiators to disperse heat from a reactor will be very large, of the order of 10's of square kilometres depending on the power requirements. Roughly, PV cells can generate 50w per square metre and radiators can remove 400w per square metres. A large power saving from centrifugal gravity will be reflected in commensurately smaller requirements for power generation or heat dissipation.
  • The hull of the cylinders is relatively amenable to additive manufacturing techniques.
While a classic O'Neill cylinder is a single void so it could be evacuated by breaching the hull, apparently the odds of a large enough meteoroid actually hitting an object the size of a space habitat are astronomically low. Shielding capable of stopping cosmic radiation and micrometeorite impacts can be added to a habitat of this type fairly readily. It would take a deliberate attack to cause an evacuation event.
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Old January 29th, 2019, 07:18 AM
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How costly would it be to create an O'Neill cylinder out of something like bonded superdense or something you imagine?
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Old January 29th, 2019, 10:32 AM
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Originally Posted by nobby-w View Post
Some variant on the design would likely be the best approach unless you want to postulate some fairly pulpy mcguffinite in your setting. The pattern has the following advantages:
  • It has two contra-rotating cylinders; as long as the bearings hold out it can mix and match zero-g and centrifugal gravity sections.
  • Aluminium is strong enough to use as a construction material and both aluminium and titanium can be mined from lunar regolith. If you place the colony in the L4 or L5 position, you can deliver construction materials with a mass driver on the surface of the moon, and they won't need excessive delta-v at the receiving end. You can catch the materials with what is essentially a giant kevlar net. This means that the millions of tons of construction materials can be delivered to their destination cheaply - in fact it will be more expensive and use more power to refine the aluminium than it would to fire it to a rendezvous at the L4 or L5 point of the moon with a mass driver.
  • Even if you have gravitics in your setting, centrifugal gravity is going to use less power. Either PV cell arrays or radiators to disperse heat from a reactor will be very large, of the order of 10's of square kilometres depending on the power requirements. Roughly, PV cells can generate 50w per square metre and radiators can remove 400w per square metres. A large power saving from centrifugal gravity will be reflected in commensurately smaller requirements for power generation or heat dissipation.
  • The hull of the cylinders is relatively amenable to additive manufacturing techniques.
While a classic O'Neill cylinder is a single void so it could be evacuated by breaching the hull, apparently the odds of a large enough meteoroid actually hitting an object the size of a space habitat are astronomically low. Shielding capable of stopping cosmic radiation and micrometeorite impacts can be added to a habitat of this type fairly readily. It would take a deliberate attack to cause an evacuation event.

The 2000 cities of my TC Earth are all Oneill like, are on the cylinders primarily to save energy (less maintenance to maintain then solar power and the only working fusion at the time of their construction was expensive He3, the reason for all that lunar regolith to be processed in the first place.


There are bearings but they are a failsafe, huge permanent magnets are in place to keep the spin frictionless while other electromagnets regulate it.


I have huge solar foundries/mills that a constant stream of material from the surface goes to for heating, shaping and casting.


The impetus for all this is a plague that reduces the human population to 1 billion. So, a rather single-minded total species focus.
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Old January 29th, 2019, 05:35 PM
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[ . . . ]
The impetus for all this is a plague that reduces the human population to 1 billion. So, a rather single-minded total species focus.
The rationale I'm using for space habitats in my 'verse under construction is in early colonisation phases, boosting into orbit was relatively expensive, even with SSTOs.

Relatively few worlds existed initially that were habitable without substantial terraforming work. These were colonised quickly and formed the basis of the early interstellar economy. Because of the cost of lifting supplies into orbit a network of space stations and habitats were established to support shipping.

Fuel, raw materials and other supplies could be mined in places that were cheaper to ship from. This supported large-scale terraforming programmes on other worlds and economic development on the intrinsically habitable worlds.

Although cheaper orbital take off/landing tech and smaller, cheaper ships became widespread, the spacegoing infrastructure still remained and there is a substantial interstellar network of quasi sovereign and outright sovereign habitats.

The 'verse also has a large population of stateless spacegoers derisively called smegulons (think something like the belters from the Expanse). These folks have a habit of squatting and refurbishing space, asteroid and old habitats such as mines on low-g worlds or moons. Although not terribly well organised, they still form a large subculture that is largely independent of state control and sufficiently well armed to ensure it stays that way.

Needless to say, smegulons are associated with piracy, smuggling and supply and fencing of all manner of illicit goods. They can often provide discreet repair and upgrade services for starships. For a party of adventurers, staying on the smegulons' good side can be a boon, athough from time to time they may request a favour of folks able to go downside into full gravity.

Most space habitats have some indigent homeless smegulon population. Some are outright squatted and taken over by smegulons.
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Old August 26th, 2020, 06:47 PM
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and my wife's stepfather has a house with 3 stories of about 2m x 3m floor area (he built it himself).
Any chance of photos, or a rough floorplan sketch?
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Old August 27th, 2020, 11:22 AM
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Any chance of photos, or a rough floorplan sketch?
No photos I'm afraid, but the floor plan was roughly as below. The building was located in what was effectively a slum in Jakarta; there were lots of self-built houses much like it around there.



Floor area, roughly 2m x 3m
Construction, Wood frame, plywood walls, sheet metal roofing.
The kitchen had a little bit of bench space and a two ring Rinnai gas stove.
The bathroom had a squat-and-hover toilet and a cistern for washing water.
The mezzanine had their stuff stored in it.
The living room had a furry blanket on the floor. The family could sleep there or use it as a living room.
They had a dog, which lived in the attic.
The house had plumbing for a tap to fill the cistern. Jakarta's water is sterilised with salt and isn't drinkable, so bottled water is the norm for cooking and drinking.
Power came from a highly unsafe looking connection to a shared meter outside the house. Capacity was probably 900W or 1,300W.

Total cost to build, approx 20m IDR. (about $1,350 USD).
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Old August 27th, 2020, 01:14 PM
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Thank you. That's impressive -- a better use of space than many of the "tiny homes" that have been gaining in popularity. I had a moment at first where I couldn't visualize the stairs, but I wasn't paying attention to the mezz height. What's more impressive is that the home slept four.. and a dog. I would have thought a house pet to be right out of the question.
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Old August 27th, 2020, 02:05 PM
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Thank you. That's impressive -- a better use of space than many of the "tiny homes" that have been gaining in popularity. I had a moment at first where I couldn't visualize the stairs, but I wasn't paying attention to the mezz height. What's more impressive is that the home slept four.. and a dog. I would have thought a house pet to be right out of the question.
The stairs are very steep - almost a ladder.
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