Designing a Venus Cloud Base

[RuBisCO]

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Mr. Rubisco,

Incorrect titles, implied wrong pronoun, triggered, so triggered!!!

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Is really annoying when you drop numbers without have a real idea or reference of what are you talking about

That is low considering I did all the numbers 2 years ago, you can read it on that thread you conveniently forgot.

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they evaporate that water carrying that heat to the top of the envelope, this cool down few degrees the plants layer and the human habitat below.

What use is that if all sides of the balloon are hotter then the interior?

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If we use the special emissivity cover to radiate heat directly to space, then that is all we need for plants and us. 

How? How are you going to do that under kilometers of clouds???

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I am an evidence machine, is time that you provide once a while some evidence.. "as the 1gw air conditioner."

READ THE PREVIOUS THREAD!!!

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Take a look to the amount of radiation that people receive in airplanes.. then reduce a bit the altitude and increase the time exposure by 50 years. 
Then try to convince all inhabitants they will not die from cancer.

Airline pilots, people of Ramsar and people of elevated altitude have no increased rate of cancer. Linear No Threshold Model of radiation induce cancer does not hold up below 100 mSv/a.

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The higher cities are at 4000m in bolivia.  You may have some towns at 5000m but without much stadistic data. At 5000m you have 2 times the shielding than at 7500m.

If your going to argue that we have no generational data at 7500 m as a problem, then do please tell me why you think there will be no problem with at 90% gravity? We have no data, ergo problem.

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Helium and hydrogen lifting capacity is reduced. Air may increase.. not sure.. if is at higher temperature. You still can do that at 54km, you dont include the habitat inside the lifting envelope, but you deposite there all your waste heat from the machines and you apply special emissivity coefficients to the envelope (different top from bottom) to harvester heat.

You forced me to find my original spreadsheet, and guess what, it was at 55.5 km, external temperature of 284 K or 11°C. My design consisting of 10 modular habitat balloons and 20 hydrogen balloons, total lifting 100,000 tons. Each balloon is 214 m in diameter, total mass of balloons assuming 100 g per m^3 (which is 0.18 mm, beach ball thickness of PVF) is 430 tons (0.43% of total mass) (to simplify calculations all balloons are the same diameter and assumed spheres). 29,393 tons of air (44% O2, 56% N2) is required, plus 4097 tons of H2 is required.

The same at 50 km the balloons are now 173 m in diameter, total mass is 286 tons (not including layers of insulation) and requires 34630 tons of air (20% O2, 80% N2), plus 4263 tons of H2. You need more gas by mass at lower altitude.

http://www./download/cbnrb4qrbn8ucoy/Float3.ods

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The envelope needs certain thick to support the structure, you can divide that thick in 2 or 3 layers

Or you can just make one single layer, make it thicker.

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I don't understand, now you want a city at 65km?

Only had wind speed data for 65 km, the speed reduces the lower you go.

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Reduce the day/night cycle is welcome.. but not really necessary.. I will put this as last of requirements.

Yeah because who cares how long plants have no light?

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About wind speed, I am not interested in wind speed at certain layer.. I am interested in wind gradient.. the difference of wind speed at different layers.. that is the energy you can harvester.
At lower altitudes from 48 to 50, is when most of the speed change happen.

And why can't you drag uninhabited section down there to generate power from 55.5 km?

 

 

[AngelLestat]

20 hours ago, RuBisCO said:

That is low considering I did all the numbers 2 years ago, you can read it on that thread you conveniently forgot.

Ok, I have time to see your work, seems serious. And I did not forgot.. I never read it at that time.

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What use is that if all sides of the balloon are hotter then the interior?

Is not like real tropical forest, where the water vapor rises carrying that extra heat that it took from the ground and transport 2 km up until it condense releasing the heat.
In this case it carries that heat but it would not condense because is warmer.  Unless you have a surface that is colder.. that is where the next breakthrough saves the day:  

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How? How are you going to do that under kilometers of clouds???

From what I understand from this technology, the key is emitting heat in a frequency that can not be absorbed by the atmosphere and reflect at the same time sunlight or other types of frequencies.
They have achieved 5 celsius of passive cooling against the environment.
This should be tuned for venus, for example you have some heat spectrum free in the water region or other chemicals, so you choose an emission in a special spectrum range.. this mean.. that you only absorb in this same spectrum, and if nothing is emiting in that same spectrum then you are cooling.  That is why is titled "radiating directly to space".
You still need to fight against convective heat from the atmosphere, but it helps a lot. At the end, it will all depend on the cost/benefics

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Airline pilots, people of Ramsar and people of elevated altitude have no increased rate of cancer. Linear No Threshold Model of radiation induce cancer does not hold up below 100 mSv/a.

The problem with radiation is mostly the unknown, because is very hard to prove if someone get sick due radiation, or if someone born with a defect by radiation, or if you get cancer.. or if your sperms receive damage and you pass a genetic error to your child's (or 2 generations before). Nobody wants to receive radiation if they can avoid it, so paid a bit more the electricity bill may be fine for them, more if its payload bill is reduced.
You can have also those who dont care and they want other kind of cities designs with better view.
Venus does not have magnetic shielding.. but the atmosphere works fine, I guess the risk limit should be 55.5km, no just for ionized radiation, also for UV and other drawbacks that I mention.
The perfect altitude will depend on the needs and manufacture development, if you are just starting colonize, you need every kg you can get, then you can start playing with other designs.
But I see your points, maybe we should fine a middle ground.

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If your going to argue that we have no generational data at 7500 m as a problem, then do please tell me why you think there will be no problem with at 90% gravity? We have no data, ergo problem.

The only point that I made is that at 5000m you have 2 times more shielding than at 7500m  (for UV and Ionized), this mean that even if you have data at 5000m, it does not compare with 7500m.

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You forced me to find my original spreadsheet, and guess what, it was at 55.5 km, external temperature of 284 K or 11°C. My design consisting of 10 modular habitat balloons and 20 hydrogen balloons, total lifting 100,000 tons. Each balloon is 214 m in diameter, total mass of balloons assuming 100 g per m^3 (which is 0.18 mm, beach ball thickness of PVF) is 430 tons (0.43% of total mass) (to simplify calculations all balloons are the same diameter and assumed spheres). 29,393 tons of air (44% O2, 56% N2) is required, plus 4097 tons of H2 is required.

The same at 50 km the balloons are now 173 m in diameter, total mass is 286 tons (not including layers of insulation) and requires 34630 tons of air (20% O2, 80% N2), plus 4263 tons of H2. You need more gas by mass at lower altitude.

http://www./download/cbnrb4qrbn8ucoy/Float3.ods

 

 

Heh.. the work you with the 55.5km base was fine, the other had many concept errors..
One problem was strategic choice, In the 50km case you choose to active cooling the whole envelope to 22c!!  (you need coat for that, more if we take into account that the air is dry, your cooling by sweating increase)
First, is not even needed, because hot air rise and cool air goes down, so if you start to cool the habitat in the bottom of the envelope, you will see that you can have 27c in the human space and few meters above the human zone the temperature will start to rise fast until it reach few tenths lower than the outside air. This mean that your average temperature inside the envelope, can be 65.5, and the outside air 66, and those 0.5c in the whole envelope are the ones you need to cool down from the habitat area.
But that is not even the most effective way to do it. Because if you use very good insulators in the habitat area, and you dont connect the human area with the envelope. Then you will need a lot less of cooling.
I made the math, and you are wasting as 200 to 400 times more energy this way.. (without count the 22c you choose)
Now.. that is not even all.. when you decide to cool the whole envelope, you also decrease its lifting vs the outside air.. that is why you lifting capacity at 55km increased vs 50km.
But well, we can merge many of these methods including yours to find the ultimate solution. 

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Or you can just make one single layer, make it thicker.

If you have more layers you can pass argon (which you get for free trying to separate the other gases) by inside working as a very good insulator, is the one used in the most quality windows.

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Yeah because who cares how long plants have no light?

Good point
mmm... Even using the faster winds, you have a problem with the night hours that you need to solve with artificial light.  Increase a bit the cost, but no the energy consumption.. There was a new breakthrough with incandescent lights, for example led had a lumen efficiency of 15, this new light bulb has an efficiency of 40, it works in any choosen spectrum and might be cheaper than led..   

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And why can't you drag uninhabited section down there to generate power from 55.5 km?

 

You need longer cable?   mmm  is not really an excuse..  taking into account this special case, it can be done without lost efficiency, instead use a kite, you can drag a small rigid wing with a turbine generator, it will be cheaper than the kite for this special use. The benefit of the kite that you don't need transport energy by the cable, and your generator unit can be in the habitat (this way you can use them above you) Very longer cables are not ideal to use the kites as propulsions.  The habitats needs to counter the meridional wings.. so aerodynamic designs should be having into account.  
How it will look the kite:

 

 

Edited January 17, 2016 by AngelLestat

[Rakaydos]

Ideally, the base will be designed to survive 50km in short streches, during emergency repairs or for extra power at midnight,  but intended to fly at 55 for regular operation

[RuBisCO]

4 hours ago, AngelLestat said:

Ok, I have time to see your work, seems serious. And I did not forgot.. I never read it at that time.

Is not like real tropical forest, where the water vapor rises carrying that extra heat that it took from the ground and transport 2 km up until it condense releasing the heat.
In this case it carries that heat but it would not condense because is warmer.  Unless you have a surface that is colder.. that is where the next breakthrough saves the day:  

From what I understand from this technology, the key is emitting heat in a frequency that can not be absorbed by the atmosphere and reflect at the same time sunlight or other types of frequencies.
They have achieved 5 celsius of passive cooling against the environment.
This should be tuned for venus, for example you have some heat spectrum free in the water region or other chemicals, so you choose an emission in a special spectrum range.. this mean.. that you only absorb in this same spectrum, and if nothing is emiting in that same spectrum then you are cooling.  That is why is titled "radiating directly to space".
You still need to fight against convective heat from the atmosphere, but it helps a lot. At the end, it will all depend on the cost/benefics

Ok let me get this straight, you think one experiment means that you have the technology that somehow makes it all worthwhile to build a cloud city at 50 km, instead of 55.5 km, those 5.5 km are that worth it to risk it all on a technology so radical it been done once. Yes cost/benefit, I would bet the benefit of passive cooling is worth the extra 5.5 km, then having all these contrived cooling system just to fly 5.5 km lower!

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The problem with radiation is mostly the unknown, because is very hard to prove if someone get sick due radiation, or if someone born with a defect by radiation, or if you get cancer.. or if your sperms receive damage and you pass a genetic error to your child's (or 2 generations before). Nobody wants to receive radiation if they can avoid it, so paid a bit more the electricity bill may be fine for them, more if its payload bill is reduced.
You can have also those who dont care and they want other kind of cities designs with better view.

The problem with 90% gravity is mostly unknown, how do we not know all the children will grow three eyes and shot laser beams out of their skulls? 55.5 km is equal to 6000 m here on earth, thousands of people are working above that right now, millions are flying above that right now, there are hundreds of thousands of people that have been living for generations at higher natural background radiation loads then that! Just because we don't know, does not mean it does in fact do anything bad.

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The only point that I made is that at 5000m you have 2 times more shielding than at 7500m  (for UV and Ionized), this mean that even if you have data at 5000m, it does not compare with 7500m.

Hey we got data at 100% earth's gravity, but not 90% so we can't compare can we?

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Heh.. the work you with the 55.5km base was fine, the other had many concept errors..
One problem was strategic choice, In the 50km case you choose to active cooling the whole envelope to 22c!!  (you need coat for that, more if we take into account that the air is dry, your cooling by sweating increase)
First, is not even needed, because hot air rise and cool air goes down, so if you start to cool the habitat in the bottom of the envelope, you will see that you can have 27c in the human space and few meters above the human zone the temperature will start to rise fast until it reach few tenths lower than the outside air. This mean that your average temperature inside the envelope, can be 65.5, and the outside air 66, and those 0.5c in the whole envelope are the ones you need to cool down from the habitat area.
But that is not even the most effective way to do it. Because if you use very good insulators in the habitat area, and you dont connect the human area with the envelope. Then you will need a lot less of cooling.
I made the math, and you are wasting as 200 to 400 times more energy this way.. (without count the 22c you choose)
Now.. that is not even all.. when you decide to cool the whole envelope, you also decrease its lifting vs the outside air.. that is why you lifting capacity at 55km increased vs 50km.
But well, we can merge many of these methods including yours to find the ultimate solution. 

Oh look at that if on the spreadsheet I raise the hab temperature to 333 K and reduce the balloon size to 172 m diameter (vs 174 m, to lift 100 kt exact)  then the amount of gas needed is 29,531 tons,  which is still above the 29393 tons needed at the higher altitude, but ok that is tiny, fine what ever, the gas needed is inconsequential between these two schemes. 

I never even calculated how much cooling would be needed in total, but just to pump out heat from growing plants though, will already be enough to make up for the mass of larger balloons for flying at a 55.5 km.

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If you have more layers you can pass argon (which you get for free trying to separate the other gases) by inside working as a very good insulator, is the one used in the most quality windows.

Or we could just fly at 55.5 km and not need any insulator at all.

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You need longer cable?   mmm  is not really an excuse..  taking into account this special case, it can be done without lost efficiency, instead use a kite, you can drag a small rigid wing with a turbine generator, it will be cheaper than the kite for this special use. The benefit of the kite that you don't need transport energy by the cable, and your generator unit can be in the habitat (this way you can use them above you) Very longer cables are not ideal to use the kites as propulsions.  The habitats needs to counter the meridional wings.. so aerodynamic designs should be having into account.  
How it will look the kite:

A 6 km cable is not that big of a problem, even you admit it.

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mmm... Even using the faster winds, you have a problem with the night hours that you need to solve with artificial light.  Increase a bit the cost, but no the energy consumption

It may be possible to engineer plants that can survived 48-72 hours of darkness.

[Findthepin1]

39 minutes ago, RuBisCO said:

It may be possible to engineer plants that can survived 48-72 hours of darkness.

Speaking of which, how will we survive that? If you're free-floating in the habitable altitudes, your day will be something like four Earth days long. If you're tethered to the ground it'll last months. Can we adapt to a four-day cycle between sunrises? What's the theoretical limit for us humans to adapt to a day length?

[Kaos]

I am sure we can adapt to any day length. If not biological then technological. Artificial light and shadows might do the tricks. Perhaps all of Venus will use only one time zone then. Perhaps even the same time zone as the Moon and asteroids. Only Earth and Mars will orient the sleeping cycle to the sun, as it is of usable length.

[Rakaydos]

1 hour ago, Kaos said:

I hourssurnto any day length. If not biological then technological. Artificial light and shadows might do the tricks. Perhaps all of Venus will use only one time zone then. Perhaps even the same time zone as the Moon and asteroids. Only Earth and Mars will orient the sleeping cycle to the sun, as it is of usable length.

Or more dramAtically, a soletta at the sun-venUs l1 could Interrupt the day, turning 48 hours of daylight INto 16 ho urs of morning/ day, 16 hours of night/eclipse, and 16 more hours of evening. Reverse It woth artificial lighting at night.

[RuBisCO]

13 hours ago, Findthepin1 said:

Speaking of which, how will we survive that? If you're free-floating in the habitable altitudes, your day will be something like four Earth days long. If you're tethered to the ground it'll last months. Can we adapt to a four-day cycle between sunrises? What's the theoretical limit for us humans to adapt to a day length?

those people in the antarctic or arctic do go insane now and then don't they?

10 hours ago, Rakaydos said:

Or more dramAtically, a soletta at the sun-venUs l1 could Interrupt the day, turning 48 hours of daylight INto 16 ho urs of morning/ day, 16 hours of night/eclipse, and 16 more hours of evening. Reverse It woth artificial lighting at night.

If we could terraform Venus, but leave its 4 month long days, we could make a whole ecosystem that lives by seasonal-days, it would make an interesting sci-fi setting.

[fredinno]

4 hours ago, RuBisCO said:

those people in the antarctic or arctic do go insane now and then don't they?

If we could terraform Venus, but leave its 4 month long days, we could make a whole ecosystem that lives by seasonal-days, it would make an interesting sci-fi setting.

Part of the reason Venus is hell is because of its slow a** rotation.

[RuBisCO]

5 minutes ago, fredinno said:

Part of the reason Venus is hell is because of its slow a** rotation.

if superotation is maintained and a thick enough atmosphere, it should be possible to maintain a nice climate all ye/ I mean all day long.

[AngelLestat]

Here on earth there is people living in high latitudes, which they have 6 months of night and 6 months of day.
So I guess yes.. we can adapt.
Even crops if we select those seeds in each generation that work best in those conditions. We can improve that with genetic manipulation, or just lights and shadow as I said. Wait 10% less between day/night cycles by flying high would not do much.

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Now we need understand the estimative cost cost of each element, material and energy to know what strategy looks better for an hábitat.

Materials and elements, from the cheapest to most expensive.

Atmosphere:
Nitrogen---> the most cheap useful element, weights less than oxygen, leaks 4 times slower, number 1 lifting gas.
Oxygen --> it will come from plants and as bioproduct of co2 to carbon fibers.
Co2 to carbon high quality fibers --> This will be more cheap than earth due co2 concentration, Link.  You can do almost all with carbon.
Argon--> useful as thermal gas insulation.
Sulfur --> very usefull as construction material and other process.
Sulphuric Acid --> The most chemical used in industry.
Water--> This will have a high demand, h2 as lifting gas is not recommended.
Helium--> It said 12ppm which is higher than earth atmosphere, Not sure the amount at cloud level, but it will be very welcome.

Surface:
All kind of elements can be mined in concentrations that will depend on location, it can be done with current tech, 10 to 15 years of extra development to the final design.
There is a big chance to find water reservoirs trapped in the ground, this would be of great help for the Venus Economy and its development.

Energy

Cloud Level: This will be cheaper than earth depending on the materials used and how advanced we would be in manufacture.
Surface: We can exploit thermal differences between 800c and 450c on geologic active locations.
It will be possible to use microwave beamed energy from the floating habitats.

Habitat lifting capacity

Volume-Surface mass ratio:

 

             

Radius	Volume/Surface	Mass T
25	8	22
50	17	183
100	33	1466
200	67	11700
400	133	93866
800	267	750933

That is simple math to see how the volume increase much faster than the surface which give us that ratio of difference.
But is not very accurate because the surface should be stronger to carry bigger mass and for structure support, plus all problems related with bigger scale, but even taking all those thing into account, we can expect that the cost for surface will decrease in respect to the lifting gas cost for bigger habitats, so big habitats can float at higher altitude.

Cooling requirements with respect height
This give us another estimative, we need 1/150 to 1/300 the amount of energy needed to cool the whole envelope.
Because the habitat volume will be 150 times smaller than the envelope, and it will also depend on the insulation.
This ratio does not change depending the size of the habitat, the only that change is the power consumed depending the height. But that extra cost should be similar to the surface cost increase to allow passive cooling.
I will like to make a graph with real values when I have time.  

Then we need to add other pros and cons due height and size.
This can all be resumed in a graph of Height / Cost relation with different lines matching each factor and for the 3 cases, small outpost, medium city, big city..  That will give us an estimative of the best choice for each case. 

 

On 17/1/2016 at 11:06 PM, Rakaydos said:

Ideally, the base will be designed to survive 50km in short streches, during emergency repairs or for extra power at midnight,  but intended to fly at 55 for regular operation

Not sure, that can be only done with bag envelopes, no rigid.  There are many issues with bag envelopes for big structures.

23 hours ago, RuBisCO said:

Ok let me get this straight, you think one experiment means that you have the technology that somehow makes it all worthwhile to build a cloud city at 50 km, instead of 55.5 km, those 5.5 km are that worth it to risk it all on a technology so radical it been done once. Yes cost/benefit, I would bet the benefit of passive cooling is worth the extra 5.5 km, then having all these contrived cooling system just to fly 5.5 km lower!

Look.. you are helping.. but when you enter in this mode "lets ignore what he said and lets focus to twist and counter the thing I can, just to disagree", is not helping and takes us nowhere.
I explain that even without that tech.. you only need 1/150 or 1/300 (with insulation) the amount of energy needed to cool the habitable zone, even if it share the same volume, because cool air stays down.
And you dont need 22 degrees for comfort zone, 28 C with 25% of relative humidity you are perfect.

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55.5 km is equal to 6000 m here on earth, thousands of people are working above that right now, millions are flying above that right now, there are hundreds of thousands of people that have been living for generations at higher natural background radiation loads then that! Just because we don't know, does not mean it does in fact do anything bad.

You are just trying to ignore any kind of drawback?  UV increase, ionized radiation increase.. we know just that.. UV protection carries an extra cost for the surface, we can not do much with the other, so we need to accept it as a low drawback that it may be worth it.
by the way.. only airline crew receive high doses, not the passengers. 

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I never even calculated how much cooling would be needed in total, but just to pump out heat from growing plants though, will already be enough to make up for the mass of larger balloons for flying at a 55.5 km.

If you include plants, the volume does not increase much, also plants does not need so much cooling. Is the sun or UV what it kill them, not so much the temperature.

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Or we could just fly at 55.5 km and not need any insulator at all.

Ok, help me to calculate how much the cost increase with 30% more surface, rigid structure and scale difficulties vs insulation.

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A 6 km cable is not that big of a problem, even you admit it.

I admit it..  the same than many other things, you are the one allergic to admit something xd
Flying at higher altitude can be a good choice depending the size of the habitat and its design or purpose.
But I want to understand those cost choices better.

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It may be possible to engineer plants that can survived 48-72 hours of darkness.

Yeah, but only if that does not decrease the growth rate too much.. if we put the plants in vertical structures as buildings, then it will be more easy to provide artificial shadow-light when is needed.

[Kaos]

Regarding the problems of UV radiation and cooling: Perhaps it would be useful to have some uncrewed balloons above the station, high enough to have low temperatures. These balloons are connected to the main balloon colony by kilometer long cables which hold the things together, transport electricity and some cooling gas or fluid. This coolant is cooled down to say 270 K in the upper station and used in the lower station to cool it energetically efficient.

Advantage: Main station is UV safe and lower, so it needs less volume for the same lift, but needs less energy for cooling.

Disadvantage: Such a large structure is more likely to to experience different wind speed in its components. The connection has to be stable enough to do so.

What do you think about cooling balloons?

[AngelLestat]

The different wind speed with just 4 or 5 km difference is not a big deal.. The 5 km of air conduct should be thermally isolated.

But in resume, just cool the habitat is not so energy intensive, but it may be a inflection point in that decision with bigger habitats.. not sure the magical number.

We already have many things solve, it would be good to sum it all up in a plan and then compare this with a mars habitat plan.  With the first steps and deltav using rockets (delta heavy or others) to make an small outpost, and then the long term of how a city would be and its economy.
It would be nice to set this once for all, what planet has more sense.

[Rakaydos]

13 minutes ago, AngelLestat said:

The different wind speed with just 4 or 5 km difference is not a big deal.. The 5 km of air conduct should be thermally isolated.

But in resume, just cool the habitat is not so energy intensive, but it may be a inflection point in that decision with bigger habitats.. not sure the magical number.

We already have many things solve, it would be good to sum it all up in a plan and then compare this with a mars habitat plan.  With the first steps and deltav using rockets (delta heavy or others) to make an small outpost, and then the long term of how a city would be and its economy.
It would be nice to set this once for all, what planet has more sense.

If you do compare it, do it an another thread.

But for the venus habitat altitude, remeber that when damaged the base will slowly decend- you want a safety margin to allow for repairs before you reach uninhabitable altitudes.

So the habiat needs radiation shielding to haandle 56 KM, thermal shielding to handle 50 KM (at least for a short time), and the capability to make external repairs even at 50 KM, while powering itself through the night at 56 KM. The habitat hovers at the half-bar, and if something goes wrong they can fix it (or evacuate to functional sections and cut the broken section loose) before they go below the 50 KM marker.

[Findthepin1]

What if the broken section is the balloon?

EDIT: Idea! We can make the balloon divided into "pods" like the things inside orange slices. Cut open an orange and you'll see them, they're like a centimetre long. There'd be lots of sort of balloon-pods inside the larger balloon. If one pops, it'd be insignificant.

Edited January 20, 2016 by Findthepin1

[Rakaydos]

4 minutes ago, Findthepin1 said:

What if the broken section is the balloon?

EDIT: Idea! We can make the balloon divided into "pods" like the things inside orange slices. Cut open an orange and you'll see them, they're like a centimetre long. There'd be lots of sort of balloon-pods inside the larger balloon. If one pops, it'd be insignificant.

Well, the balloon isnt under pressure, so it wont be a big blowout like Mark Watny's Airlock-cannon. it'll take time to lose lifting gas (unless the rip is at the very top of the balloon, but it still has to "burp" if the baloon is at all rigid) and since breathing air is also a lifting gas the habitat has a very low terminal velocity. (large cross section + low effective weight)

[Findthepin1]

28 minutes ago, Rakaydos said:

Well, the balloon isnt under pressure, so it wont be a big blowout like Mark Watny's Airlock-cannon. it'll take time to lose lifting gas (unless the rip is at the very top of the balloon, but it still has to "burp" if the baloon is at all rigid) and since breathing air is also a lifting gas the habitat has a very low terminal velocity. (large cross section + low effective weight)

I'd rather 1 or 2% of the good air get out than 100%.

[AngelLestat]

12 hours ago, Rakaydos said:

If you do compare it, do it an another thread.

is the same I am saying in the other thread and in this thread.  Here to find a plan and understand the problems, then in the other thread to compare that plan with a mars plan.. trying to solve problems is the only way to understand the difficulties of each case.

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But for the venus habitat altitude, remeber that when damaged the base will slowly decend- you want a safety margin to allow for repairs before you reach uninhabitable altitudes.

So the habiat needs radiation shielding to haandle 56 KM, thermal shielding to handle 50 KM (at least for a short time), and the capability to make external repairs even at 50 KM, while powering itself through the night at 56 KM. The habitat hovers at the half-bar, and if something goes wrong they can fix it (or evacuate to functional sections and cut the broken section loose) before they go below the 50 KM marker.

The only way to ensure that safety margin is letting the envelope to expand or contract. (venting gas or adding gas helps, but is not enough)
But there is no problem with heat if you go down to 50km or even less for few days in case the city is big. Take into account that volume/surface ratio increase with scale.  This mean the heat capacity (volume) is bigger over the heat flux (surface). In simple words.. it will take a lot of time to heat that huge volume.

53 minutes ago, Findthepin1 said:

What if the broken section is the balloon?

EDIT: Idea! We can make the balloon divided into "pods" like the things inside orange slices. Cut open an orange and you'll see them, they're like a centimetre long. There'd be lots of sort of balloon-pods inside the larger balloon. If one pops, it'd be insignificant.

The only thing that can compromise a big envelope, would be a huge break of epic proportions due bad design. If you design your surface well enough, you can limit until what point a damage/rift can spread, that way to separate volume into pods is a nice way to do it if you want to increase the safety, but it brings other drawbacks with light and view (if the city is inside the envelope) and with cost/weight because you are increasing the surface area.  For example expand the city using many modular envelope that can be added.. increase a lot the surface and decrease the aerodynamics.
Not sure if we can be able to figure out what could be the best city/envelope design. For example in airships manuals they always talk that rigid airships are way more superior to blimps, but those airships are designed to travel at 40m/s, a city should be designed to have a maximum speed of  7m/s, even if in normal circustances only needs 2m/s to maintain its latitude. Because if you reach the poles it would not be possible to leave the twin cyclones. The people would not die because it has a huge diameter, but you need to counter as 20m/s of meridional winds to go back.

Another question is: envelope bag with cables, or envelope bag with city inside, or rigid structure (allowing some expansion).
If the city is not inside the envelope, you can take advantage of the sun heat and different surface emissivity top and bottom to trap heat and increase your lifting. But few degrees in temperature should not be such a big deal of change in altitude, I don't remember rubisco calculations..

[Rakaydos]

1 hour ago, AngelLestat said:

Another question is: envelope bag with cables, or envelope bag with city inside, or rigid structure (allowing some expansion).
If the city is not inside the envelope, you can take advantage of the sun heat and different surface emissivity top and bottom to trap heat and increase your lifting. But few degrees in temperature should not be such a big deal of change in altitude, I don't remember rubisco calculations..

Rigid citybag with supplementary cablebags, I'd think.

[Dr.K Kerbal]

Sweet. also looks like your fingers are probably bleeding though

[fredinno]

How in the world do you extract water vapour from the atmosphere? There's more water in the driest of deserts On Earth, than in Venus' atmosphere (in PPM)

[Findthepin1]

8 hours ago, fredinno said:

How in the world do you extract water vapour from the atmosphere? There's more water in the driest of deserts On Earth, than in Venus' atmosphere (in PPM)

Water vapour in Venus' atmosphere is at 20 ppm at the surface. It'll be higher further up because it is a lifting gas in that atmosphere (I think) and there is likely more of it at the 1-atm level because it's part of the chemical reactions that cause the gigantic permanent global sulphuric-acid lightning storm at about that altitude. However, if it isn't accessible at that height, you can go to the surface where the partial pressure of water is around 0.186 percent of an atm. That's 20 ppm (0.00002) times 93 atm. I may be wrong, but that amount seems extractable.

[fredinno]

11 hours ago, Findthepin1 said:

Water vapour in Venus' atmosphere is at 20 ppm at the surface. It'll be higher further up because it is a lifting gas in that atmosphere (I think) and there is likely more of it at the 1-atm level because it's part of the chemical reactions that cause the gigantic permanent global sulphuric-acid lightning storm at about that altitude. However, if it isn't accessible at that height, you can go to the surface where the partial pressure of water is around 0.186 percent of an atm. That's 20 ppm (0.00002) times 93 atm. I may be wrong, but that amount seems extractable.

But the water would all float up anyways. And anything that needs you to go to the surface- forget it.

[AngelLestat]

On 20/1/2016 at 5:58 PM, Rakaydos said:

Rigid citybag with supplementary cablebags, I'd think.

I found this, Geodesic spheres:

https://www.youtube.com/watch?v=OuwHsQgRDn4

 Is the only structure that becomes stronger at bigger sizes, there is another video in the links that show the same structure with a guy in each triangle, is also the structure more faster to build.

Another possibility is tensegrity sphere.

https://www.youtube.com/watch?v=Y-Ny3BfhVdw

If we shape it as an ellipsoid, we can add a mechanism in the middle to allow certain expansion and contraction, then ballonets to let enter co2 and internal pressure envelopes to compress the air.  With those 3 mechanism is safe enough of any kind of problem.
 

22 hours ago, fredinno said:

How in the world do you extract water vapour from the atmosphere? There's more water in the driest of deserts On Earth, than in Venus' atmosphere (in PPM)

How insects extract water from the deserts?
Earth has an average water of 5000ppm, but much higher in some places or much lower in others, this is equal to 15000km3 of water.
Venus has an average of 20ppm, but its atmosphere is 90 times ours, this is equal to 6000km3 of water, to that, we need to add the water trapped in the ground that should be much higher.
You also have different concentrations at different places. In the clouds you have 60ppm of water-acid and is easy to catch when it "rains".
If you go at 10 or 30 km, you dont have liquid water as in the clouds, but there is a concentration of 150ppm of pure water, you can condensate that with special surfaces and different methods to economize energy.   

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I update the info post, now is complete I guess. There is now a chart that explain the different values find on temperature, altitude and pressure on different sources, like probes or sats. Problem was that latitude in some was not included and probes only measure pressure, and altitude is an approximation.  

Edited January 22, 2016 by AngelLestat

[fredinno]

"How insects extract water from the deserts?
Earth has an average water of 5000ppm, but much higher in some places or much lower in others, this is equal to 15000km3 of water.
Venus has an average of 20ppm, but its atmosphere is 90 times ours, this is equal to 6000km3 of water, to that, we need to add the water trapped in the ground that should be much higher.
You also have different concentrations at different places. In the clouds you have 60ppm of water-acid and is easy to catch when it "rains".
If you go at 10 or 30 km, you dont have liquid water as in the clouds, but there is a concentration of 150ppm of pure water, you can condensate that with special surfaces and different methods to economize energy.   "

It's not linear like that, all the water would float to the upper atmosphere due to being a lifting gas.