Cloud cities

[AngelLestat]

Third time that I will type all this. I had 2 electricity cuts meanwhile I was doing it. The first time got me just in the finish :S

AngelLestat, from what I can gather you are talking about a mostly passive system correct? With only a relatively small airconditioning system to cool the city. You mentioned aerogel covering the city in a two odd centimeter thick layer, surely you must know how brittle aerogel is and my problem is how are you going to solve the problem of the expansion and contraction of the envelope?

I'll contribute more later but education calls.

I guess there is not much thermal difference in venus at that height, but nothing is certain, also winds will put soe stress to the structure.

So lets see..

We would have a rigid structure of graphene composites or wherever. Then we cover all that with fabric, then we have the 2 layers from the envelope.

Between the 2 layers and the fabric, we would have the aerogel, in triangle pieces one aside of the other (tetris style), so if there is expansion or contraction, pieces will push between them but without limits to grow (becouse is just 1/3 of the envelope), and they not weight much, so that force it will be almost null.

The fabric and the envelope layers needs to have low friction coefficient.

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nylon is not going to survive contact with concentrated sulfuric acid, it will dissolve very rapidly! Or is this one of the many internal insulating layers your speaking of?

I was talking about "earth" hot air ballons. To make a case of stratification, nothing more.

… where is the cool air coming from that transfer around the city?

Well, I just remove all the other sentences becouse they dont add much to the discussion, but this one is really important.

Sharp question. In principle, yes this will meaning that I need to cold also all city process. But then I realize that I have a bigger problem in my design.

I can not heat the air to 100C or more, so I can not have a higher average temperature than outside.

The heat that rise between the envelope, does not receive any heat source with more than 66 degrees, and if I use the incomming radiation in UV and IR then I would need a higher gradiant to expell that energy.

If I have time, I will think about this to see if I found a solution. I hope not being fighting against thermodynamics.

1/3 the surface area of a sphere with a radius of 365 m (a balloon capable of lifting 100 kt, at 50 km height with ~0.5 kg of lifting force) is 1.7 km^2, with 2 cm thick aerogel that is 34500 m^3, aerogel weighs 1 kg per m^3 so that is 34.5 tons of gel, about the weight of 172 people. Actually that not much weight compare to the lifting force, but how you plan to fold and send something that is 34500 m^3 to Venus is beyond me.

Heh, a sphere with 365 mts of radius??? lol, what picture are you seeing?? we are talking of my egg envelope here. It has 230 mts tall and 100 mts wide.

If we estimate a surfuce area of 25000, we will got 450kg of aerogel.

Your common sense made you think 34500 m^3 of aerogel would weight less then a single person, over 2 order of magnitude wrong, so no thank you, I'm going to stick to testing every idea rather then trusting a guess.

In my first estimation I was thinking in 1 cm until the blue area. So giving this, my mental estimation of 1 person weight was not so far, dont you?

No I was not speaking of infrared light. I was speaking of optical light: we need to let in some optical light for plant growth, those plants will convert almost all that light into heat, that heat must be pumped out.

Try to admit one mistake some day..

I said:

First we need to have a reflective IR-UV layer in the whole envelope to counter the wavelenght heat due to Sun light and cloud reflective light.

And you said:

Great, no plant growth for food.

I understand the laws of thermaldynamics. Your city needs to spend energy to keep cool, your circulation system will do nothing to change that fact, it may honestly make it worse by circulating air and increase convective heat exchange. Considering the amount of air and the surface area your dealing with, you will have to spend mega to gigawatts of energy to keep your city cool.

These kind of complex thermodinamics calculations are out of our reach. Unless you know some free software to do this.

It will be better if we just focus in the general thermodynamics principles.

Your not understand what I'm saying, or thermodynamics, you most spend energy to pump heat from a lower temperature area to a higher temperature area, no matter the mechanism, no matter some apparent average temperature.

I can transform almost all heat inside the envelope into another type of energy, there is no thermodynamic law which prohibit that.

But well, my design is still not good enoght, and maybe can not work. I dont know. You can have your smile for now But I know many technologies that can help here, I just need to think how to combine them.

How? Can you put a price tag on m^3 of gas? We can make gas at Venus, we have to take to Venus all the mass of balloon, insulators, heat pumps, radiators. Lets me compare, I'll make a city at 57 km, 100 kt, that would be ten breathable air balloons 235 m wide, and 20 more hydrogen balloons the same width, Each balloon would weigh 17 tons, totaling 520 tons, that is about 0.5% of the total mass of the structure, of which none of that is in the form of AC system, or insulators or radiators or power plant for said AC system. Seems reasonable to me. If we drop to 50 km the balloons drop in size to 176 m in width, and total balloon mass is 292 tons, that is a weight savings of 228 tons, or about .25% the total mass of the structure. So to drop down in altitude we gain 0.25% in structural mass, less then a percent, then we have to add the mass of insulator, (20 tons, aerogel 2 cm, 1 kg/m^3 insulating just the habitat balloons) the mass of an AC system, lets assume .1 kw/kg for it all and a very optimistic 2 MW needed, that is 20 tons, and then a powerplant for that lets go with a nice 100W/kg (four times that of terrestrial wind-turbines) and that is 200 tons, total is 240 tons and look at that with very optimistic assumptions we make up the weight advantage and then some in insulator, cooling system and powerplant for cooling system.

But you see your numbers? you have 20 hidrogen ballons of 235 m wide!

You know that hidrogen is not so cheap in venus.

First, insulators are very cheap, you can make aerogel from carbon dioxide (just that), mmm where we can find carbon dioxide in venus??? XD

IR and UV reflective layers also very cheap and light.

Then we need to find a good method to manage the heat "I still working on that".

But after all, in case the temperatures are not cool enoght at 50km, we still can rise the altitude like you said. But you need to accept that like I prove, there is a solid case to deal with heat instead low pressure in air production, that mass ratio keeps growing.

Before deal with those huge numbers I will try anything, maybe raise a hidrogen ballon with a light tube to aspirate all cold air from higher altitudes and use it like colling system (which I think it would not work due to the pressure difference). But well, rise in altitude, we already have that solution. whats more?

What evidence?

The fact that we have a little less radiation flux at that height than earth surface, also you are watching in one direction, so you only need to count the flux that is comming in that direction. You have also sunrises and sunsets, with that thick atmosphere they are a lot darker than here.

Not as long as it would take to make a colony on venus, we are talking about 22nd century at least right? And yes if we have such robots it does bring into question the whole idea of sending talking monkeys into space.

If we are talking of that year, then the temperature is not such an issue. We can convert all extra heat into electricity... which will help to pump more heat outside.

Doesn't sound very habitable, heck with "appropriate clothing" work in the vaccum of space at zero gravity is not so bad either, at least one wrong move won't send you falling straight into a literal hell.

At least you will have a quick death.. A push into the emptly space does not sound so nice either.

[NASAFanboy]

Cloud cities on Venus are an interesting concept.

Although I do believe they will likely grow slower than a lunar or Martian colony (Every part of the colony has to be hoisted on the balloon in the upper atmosphere in an risky operation, and there is an natural cultural stigma against colonizing Venus; almsot everyone I know is completely against it), but I am not against it.

Anyhow, I have an idea with an timeframe for an cloud city on Venus.

Here goes my plan.

2046: NASA launches the first components of SkyHab, the first module of an Venusian base onboard an SLS Block II. SkyHab is wrapped around in an fairing shaped like a glider, and is capable of both powered and free flight. Late in the year, SkyHab aerobrakes around Venus and enters its upper atmosphere. Using its gliding capabilities to stall the rapid descent, SkyHab inflates an massive helium balloon. After inflating the balloon, the fairing is cast away, and the base begins operations. Here's a basic idea of what I am envisioning.

Sorry about my bad paint skills.

2047: An second glider is launched into Venusian Orbit. This glider is like SkyHab, but the onboard laboratory module has been removed for an ascent stage. NASA launches a crew on an Hohmann transfer to Venus onboard an Mars Transfer Vehicle. The crew rendezvouses with the glider, which then repeats the ascent profile of SkyHab. Unlike the SkyHab glider, however, the crewed vehicle operates using a series of electrical propellers allowing it long-range exploration over the Venusian atmosphere. The crew flight deck, or whatever you call that piece of an spacecraft where they sit, is equipped with the ascent stage which will function both to return them, or to quickly evacuate them out of the Venusian atmosphere should something bad happen (i.e Ballon failure, .etc). The crew won't leave the Flight Deck, their main job is to serve as a base for teleoperations for probes on the surface.

You get the main idea of it, right?

Venus is a planet, and it exists.

If we ever wish to conquer the stars, it's going to be a hurdle we will have to overcome, no matter the cost.

[Dodgey]

I think you are underestimating how much a balloon of that size will change its shape. A typical balloon gains its strength from the difference in pressure, a pretty decent pressure difference, and the temperature is still 66° Celsius. Go up to approx 55km and the temperature is much closer to 30, higher still and the temperature drops even more so. Once you pass the 60km mark The temperature "stabilizes" at around 250k (-23°C). Now you must admit that that is a rather drastic change In temperature for the altitude gained. If you just float a bit higher than what you are suggesting than you can utilise a more passive temperature control system. Just change your altitude to control temperature.

[Dodgey]

Fanboy. That's a cool idea I just have a couple of questions.

1. Is the second skyhab (love the name) meant to meet up with the first at Venus?

2. Are those wings on the right of your first picture?

[RuBisCO]

Sharp question. In principle, yes this will meaning that I need to cold also all city process. But then I realize that I have a bigger problem in my design.

I can not heat the air to 100C or more, so I can not have a higher average temperature than outside.

The heat that rise between the envelope, does not receive any heat source with more than 66 degrees, and if I use the incomming radiation in UV and IR then I would need a higher gradiant to expell that energy.

If I have time, I will think about this to see if I found a solution. I hope not being fighting against thermodynamics.

The solution is the fly higher and have passive temperature control.

Heh, a sphere with 365 mts of radius??? lol, what picture are you seeing?? we are talking of my egg envelope here. It has 230 mts tall and 100 mts wide.

Sphere simply to make the calculations easier.

If we estimate a surfuce area of 25000, we will got 450kg of aerogel.

Anything other then a sphere will have greater surface area per volume not less, your surface area is order of magnitude to small. Again for a ballon capable of lifting a “City†we are talking about kilometers^2 surface areas and thus dozens of metric tons of aerogel, with volumes that are impractical to ship to venus.

Try to admit one mistake some day..

I said:

First we need to have a reflective IR-UV layer in the whole envelope to counter the wavelenght heat due to Sun light and cloud reflective light.

And you said:

Great, no plant growth for food.

and I said that the heat produced from optical light alone will be devastating for your scheme. So again you have massive energy inputs, you need to pump out all the heat.

These kind of complex thermodinamics calculations are out of our reach. Unless you know some free software to do this.

It will be better if we just focus in the general thermodynamics principles.

I can transform almost all heat inside the envelope into another type of energy, there is no thermodynamic law which prohibit that.

yes there is, its called Carnot efficiency, and its very easy to calculate, for a 50-66°C temperature difference your maximum theoretical efficiency of getting back energy will be 17-18%, that means 83%-82% of your heat will remain as heat. And that is assuming a impossibly perfect heat engine, your scheme will more certainly be far less efficient. This means you can only gather back a fraction of the energy you need to cool your city.

But well, my design is still not good enoght, and maybe can not work. I dont know. You can have your smile for now But I know many technologies that can help here, I just need to think how to combine them.

Yeah the technological solution is the fly higher, its a very simple, easy and achievable solution.

But you see your numbers? you have 20 hidrogen ballons of 235 m wide!

You know that hidrogen is not so cheap in venus.

No its very cheap, we can make it easily from the sulfuric acid of the clouds. With a simple electro-reduction cell we can convert H2SO4 to H2O and SO3 and then H2O to hydrogen and oxygen (we could even do it all as one step). It would in fact be energetically less costly then making O2 for CO2 (well actually 2CO2->O2+2CO would require less energy, CO2->O2+C(solid) would be more energy expensive, but the CO is relatively useless and best dumped), so to make ever m^3 of breathable oxygen we have 2 m^3 of hydrogen “waste†might as well use it considering it is the best lifting gas there is.

First, insulators are very cheap, you can make aerogel from carbon dioxide (just that), mmm where we can find carbon dioxide in venus??? XD

No it would require more energy to make aerogel then to make O2 and H2 from sulfuric acid, making solid carbon is not an efficient process, then you need to add in the cost of making it into an aerogel, worse carbon aerogel is very flammable and you have this with an oxygenated atmosphere on one side, not good. Then you need to consider the machines need to make sheets of it and stitch it into fabric.

IR and UV reflective layers also very cheap and light.

Then we need to find a good method to manage the heat "I still working on that".

Well I already have the solution: fly higher. Think of it this way, you want to go outside right, would it not be better to go outside to cool air at 10°C not 55°C? Would it not be nicer to go outside to a white sky and not a yellow or red sky?

But after all, in case the temperatures are not cool enough at 50km, we still can rise the altitude like you said. But you need to accept that like I prove, there is a solid case to deal with heat instead low pressure in air production, that mass ratio keeps growing.

And as my cacluations show the mass ratio is tiny, the difference for a 100 kt city would be 0.25% that is the weight of the balloons nearly double to take up a pultry 0.5% of the total cities mass. The weight of the internal gas is not counted as we don't need to bring that to Venus, nor do we need to bring the mass of a cooling system, which would negate the advantage of flying lower.

Before deal with those huge numbers I will try anything, maybe raise a hidrogen ballon with a light tube to aspirate all cold air from higher altitudes and use it like colling system (which I think it would not work due to the pressure difference). But well, rise in altitude, we already have that solution. whats more?

Altitude control means temperature control (As Dodgey pointed out) it provides a very elegant and simple solution to controlling temperature. As long as we can maintain an altitude where the outside temperature is a few degrees lower then the inside temperature we don't need to worry about a cooling system or schemes. During the day the passive temperature controlled balloon on versus can gain lift by absorbing some IR and optical energy from the ambient light, and at “night†the habitat air would cool and the balloon would lose a little altitude until the temperatures and lift equalized. No power is needed, engineered right the balloon would always maintain habitable temperatures without the need of any work (electrical or mechanical)

The fact that we have a little less radiation flux at that height than earth surface, also you are watching in one direction, so you only need to count the flux that is comming in that direction. You have also sunrises and sunsets, with that thick atmosphere they are a lot darker than here.

How does this translate into fluffy clouds being visible verse a white/yellow/orange/red abyss of haze? Or was this about currents being navigable?, how is this evidence for either?

If we are talking of that year, then the temperature is not such an issue. We can convert all extra heat into electricity... which will help to pump more heat outside.

Again Carnot efficiency means we can only gain back a faction of the heat energy as any kind of useful work, far more energy will have to be spent just pumping out the heat, and getting an energy back will only increase heat transferring not reduce it!

At least you will have a quick death.. A push into the empty space does not sound so nice either.

In a spacesuit you would have hours for someone to get you, heck with a propulsion pack the chances of being stranded afloat in space are very low. In the other case you have a constant force pulling you down at ~90% earth gravity into a real hell.

[NASAFanboy]

Fanboy. That's a cool idea I just have a couple of questions.

1. Is the second skyhab (love the name) meant to meet up with the first at Venus?

2. Are those wings on the right of your first picture?

Yes, and yes.

Also, I'm trying to envision an emergency escape system for EVA suits to be worn by astronauts working on Venus. Perhaps some sort of jetpack or something?

[Dodgey]

Yes, and yes.

Also, I'm trying to envision an emergency escape system for EVA suits to be worn by astronauts working on Venus. Perhaps some sort of jetpack or something?

Okay. Ignoring what happens after you EVA and fall (crushing pressures ect) perhaps a personal wing with engines attached could allow you to fly to the secondary balloon and await rescue, or even a backpack inflatable balloon. Obviously you need some means of rescue but that's another issue. I don't think a jetpack would be practical. It wouldn't have the thrust or delta v, think about the mmu's of today.

[Dispatcher]

I'm for tethering to the outside of the structure. If the structure goes down, that's just not a good day.

[NGTOne]

Tethering would probably work best, likely with some form of redundancy (in case one fails).

[Dodgey]

As I understood it the escape system was in-case the ship did go down.

[Idobox]

What about a simple parachute? The idea being to give you enough time to be rescued.

If you have access to a material that is both light, bendable, and photovoltaic (graphene is supposed to be able to do that), you would even have plenty of power for a small propeller, making it a very light powered paraglider.

[NASAFanboy]

What about a simple parachute? The idea being to give you enough time to be rescued.

If you have access to a material that is both light, bendable, and photovoltaic (graphene is supposed to be able to do that), you would even have plenty of power for a small propeller, making it a very light powered paraglider.

Or we could have the crew working with small helicopters as an EVA pod of some sort. Or, instead, use robots to do all the dirty work while they remain in the habitat, ready to evacuate at an moments notice.

I'm thinking about attaching engines underneath the hab that would burn to keep the vessel upright should the balloon suffer an massive rupture so the crew could run to Ascent vehicle and get out of there.

[RuBisCO]

Well these ideas sound fun as heck, remember that just a few kilometers drops you will reach uninhabitable temperatures. If you have a parachute that reduces your fall speed to 2.5 m/s and you have 5 kilometers untill you boil to death, then you have 2500 seconds, or 33 minutes to get picked up before you die of heat exhustion. I guess somekind of drone could fly down and pick you up. I think the simplist solution is to always have at least one line tieing you to the ballon: mountain climbs don't usually bring parashutes, so if you slip and fall now your just dangling from the ballon and if strong enough you could pull your self back up, maybe a crank could help you.

[AngelLestat]

Something similar to this it may look a Venus Launch Plataform.

It will rise to 65km, launch. Then it compress the hidrogen so would down.

The rocket would carry 5T to 10T of payload to Low Venus Orbit in 2 Stages, each stage detach with tank emptly, and giving the low density of each stage, would fall and float at 40km height. The launch plataform down and recover each part, then goes back to 52km where it waits until the next launch, over equator line.

Inside each stage tank, can be few liters of amoniac, with the heat evaporates and expand, this is to stand the pressure at 40km.

Anyhow, I have an idea with an timeframe for an cloud city on Venus.

Here goes my plan.

Well we have our first outpost (or skyhab).

Sounds good.

It will be safer if the first skyhab, produce hidrogen and oxygen, so when the next manned mission arrives, they have ready their ticket to go back (in case anything happens) mars direct style.

I think you are underestimating how much a balloon of that size will change its shape. A typical balloon gains its strength from the difference in pressure, a pretty decent pressure difference, and the temperature is still 66° Celsius. Go up to approx 55km and the temperature is much closer to 30, higher still and the temperature drops even more so. Once you pass the 60km mark The temperature "stabilizes" at around 250k (-23°C). Now you must admit that that is a rather drastic change In temperature for the altitude gained. If you just float a bit higher than what you are suggesting than you can utilise a more passive temperature control system. Just change your altitude to control temperature.

I am not, what is the problem with deformations? These insulators triangle tables are not fixed or attached to any place, no even between them, they just support their own weight and form the structure thanks to gravity.

They are outside of the structure between the 2 layer envelope and another (no friction) fabric that cover the structure.

Like we have equal pressure, there is no much pressure from the 2 layer envelope against the fabric which cover the structure.

The solution is the fly higher and have passive temperature control.

This is not a solution... if we have the problem of the need for big volumes to lift a payload at great heights, you can not call a solutions "not do nothing" (we already have that).

A solution would be found a way to reduce the volume or cost require to lift a same amount of payload.

So aproachs would be get down and deal with heat, or try to combine different gases to gain extra lift for the same cost, or heat the inside gases to gain more lift, or use the winds speeds to gain lift, or many others.

Sphere simply to make the calculations easier.

So? but my question was about a smaller volume.

If you said that it takes you 10kw get m3 of hidrogen, I can not tell you, "not you are wrong, if you want convert all the hidrogen in venus it would cost you X"

yes there is, its called Carnot efficiency, and its very easy to calculate, for a 50-66°C temperature difference your maximum theoretical efficiency of getting back energy will be 17-18%, that means 83%-82% of your heat will remain as heat. And that is assuming a impossibly perfect heat engine, your scheme will more certainly be far less efficient. This means you can only gather back a fraction of the energy you need to cool your city.

But I can generate work outside, and then introduce that work inside just using a conductor. My stratification approach tries to equally the average heat from inside to outside. But I guess the problems looks equal to forget about all the area that is average temperature, and then deal only with the refrigeration that small area with the internal heat generated.

No its very cheap, we can make it easily from the sulfuric acid of the clouds. With a simple electro-reduction cell we can convert H2SO4 to H2O and SO3 and then H2O to hydrogen and oxygen (we could even do it all as one step). It would in fact be energetically less costly then making O2 for CO2 (well actually 2CO2->O2+2CO would require less energy, CO2->O2+C(solid) would be more energy expensive, but the CO is relatively useless and best dumped), so to make ever m^3 of breathable oxygen we have 2 m^3 of hydrogen “waste†might as well use it considering it is the best lifting gas there is.

The same than temperature, we still dont know for sure how easy would be gather sulfuric acid. If you said that it will be cheap, then I can said that the temperature at 50km is 0C degree so there is not problem. We dont know.

No it would require more energy to make aerogel then to make O2 and H2 from sulfuric acid, making solid carbon is not an efficient process, then you need to add in the cost of making it into an aerogel, worse carbon aerogel is very flammable and you have this with an oxygenated atmosphere on one side, not good. Then you need to consider the machines need to make sheets of it and stitch it into fabric.

I never said carbon aerogel (otherwise, there is not oxygen in venus, so there is not much problem being flamable) I said Co2.

Co2 is the main ingredient for aerogels and that is not all, it needs to be in supercritical state at 53 bar minimun.

All venus surfuce has co2 in supercritical state at 90 bar. You just need "silica", that is the second more common components in the surfuce. produce aerogels Is almost free

Remember when I told you that those conditions in venus surface may be a game change in production cost for some products.

Well I already have the solution: fly higher. Think of it this way, you want to go outside right, would it not be better to go outside to cool air at 10°C not 55°C? Would it not be nicer to go outside to a white sky and not a yellow or red sky?

Of course, but the extra amount of gas that you need to produce is still a problem.

And technology advance is thanks to people who find ways to solve problems.

And as my cacluations show the mass ratio is tiny, the difference for a 100 kt city would be 0.25% that is the weight of the balloons nearly double to take up a pultry 0.5% of the total cities mass. The weight of the internal gas is not counted as we don't need to bring that to Venus, nor do we need to bring the mass of a cooling system, which would negate the advantage of flying lower.

I dont understand. You need to take the volume difference between deal with 1 bar or X bar.

How does this translate into fluffy clouds being visible verse a white/yellow/orange/red abyss of haze? Or was this about currents being navigable?, how is this evidence for either?

You are still confuse with venus graphics clouds.

Inside of venus clouds you have a lot of visibility, becouse clouds are not so dense. But this does not means that far clouds does not look fluffy. In fact they would look equal fluffy at distance.

You never thoght a fog or a cloud at earth which looks so fluffy and closed, but when you are inside, you can see hundreds of meters, even other clouds in the sky?

Edited March 15, 2014 by AngelLestat

[RuBisCO]

This is not a solution... if we have the problem of the need for big volumes to lift a payload at great heights, you can not call a solutions "not do nothing" (we already have that).

A solution would be found a way to reduce the volume or cost require to lift a same amount of payload.

So aproachs would be get down and deal with heat, or try to combine different gases to gain extra lift for the same cost, or heat the inside gases to gain more lift, or use the winds speeds to gain lift, or many others.

If reducing the volume adds MORE cost in technological solutions then higher volume IS THE SOLUTION! The cost of lifting the payloads does not just include gas and balloon skin mass but also your schemes for active cooling, for balloon construction, etc, if those schemes are more expensive then simply flying higher and achieving passive temperature control then they are not viable solution and just flying higher is the best solution. There is no reason we should not fly higher other then increase volume and gas required, which are easily solvable problems, there are many reasons we should not fly lower though.

So? but my question was about a smaller volume.

If you said that it takes you 10kw get m3 of hidrogen, I can not tell you, "not you are wrong, if you want convert all the hidrogen in venus it would cost you X"

Why would you want to covert all the hydrogen in Venus? The energy costs of keeping a city cool, building insulator and cooling systems is going to be more than just making more lifting gas.

But I can generate work outside, and then introduce that work inside just using a conductor. My stratification approach tries to equally the average heat from inside to outside. But I guess the problems looks equal to forget about all the area that is average temperature, and then deal only with the refrigeration that small area with the internal heat generated.

My point has been just refrigerating the city its self will require a lot of energy, that energy can't be gained back by any scheme in any significant amount and doing so adds only more mass. The heat difference of the city can't be used to provide energy, it must require energy, large amounts of energy by the laws of thermodynamics. Your city will be receiving significant amounts of heat via light (if its to grow plants) heat from industry, heat from conduction, convection and radiative heating from inside and outside the balloon skin, and no scheme is going to reduce this significantly without requiring a lot more mass and even violating thermodynamics. The technological solution you seek is to fly higher and achieve passive temperature control.

The same than temperature, we still dont know for sure how easy would be gather sulfuric acid. If you said that it will be cheap, then I can said that the temperature at 50km is 0C degree so there is not problem. We dont know.

You have been arguing that we should fly at an attitude that needs active cooling, I've been arguing we need to fly at an altitude that needs only passive cooling (to be more exact needs only passive heating) what ever the altitude may be, the lower the better, in fact if the detailed charts are wrong at at 50 km it is 0ºC that only makes my argument stronger for we need even less lifting gas and balloon capacity to maintain passive cooling/heating altitude.

I never said carbon aerogel (otherwise, there is not oxygen in venus, so there is not much problem being flamable) I said Co2.

Co2 is the main ingredient for aerogels and that is not all, it needs to be in supercritical state at 53 bar minimun.

All venus surfuce has co2 in supercritical state at 90 bar. You just need "silica", that is the second more common components in the surfuce. produce aerogels Is almost free

Remember when I told you that those conditions in venus surface may be a game change in production cost for some products.

So if we build balloons on the surface, we need to already have an industry on the surface for building balloons, probably highly or completely automated... why send people?

What I'm proposing is we don't start with a surface infrastructure, we “land†the balloons first long before we build them at venus, and we build them at altitude forgoing the need to build balloon material that can survive being created and constructed at 500ºC and 92 atms of CO2.

Of course, but the extra amount of gas that you need to produce is still a problem.

And technology advance is thanks to people who find ways to solve problems.

Its not as much of a problem as active heat pumps. If you fly higher the problem is solved, 'technologically' by gas production. There no reason to do it the hard way when the easier way is already technologically available and cheaper and better.

I dont understand. You need to take the volume difference between deal with 1 bar or X bar.

The volume difference is irrelevant: gas is cheap and can be made at Venus, but balloon skin, insulators, heat pumps, power plants can't and must be flown to Venus.

You need to consider how to construct your cloud city, first a set of balloons are sent to Venus that only need enough gas to float themselves and a small power plant, electrolysis/atmosphere extraction kit for extracting oxygen, if we assume 51 tons of balloons plus 49 tons of the aforementioned critical starting cargo then we need to lift only 100 tons initially, even though we have balloon capacity to lift 33 times more (assuming 100 g/m^2, 57 km altitude). What this means it needs only "land" with 4.6 tons of hydrogen gas (or ~10 tons of helium) in order to float at 57 km. As the balloons fill more mass can be added via heavier then air cargo ships that fall via paraglider into the grappling line. The initial lifting capacity is 100 tons, but when completely filled the final lifting capacity of 51 tons of balloons at 100g/m^2 and 1/3 filled with breathable air, would be 3.3 kt. The paragliders from each cargo ship could potentially even be reprocessed into more balloons, but again we did not bring gas for them, no gas at all in that case, but instead we make all the lifting gas at Venus.

If we go for 50 km or an altitude where we need active cooling we would reduced the amount of hydrogen needed initially in half, but that only a few percents the total mass so we gain little, and yet we need to add the mass of a cooling system and power plant for that cooling system. So in conclusion the mass of the gas or volume of the balloon is not counted because we don't need to land with it, only a small fraction of it, the rest can be generated at Venus easily, yet the mass of a cooling system must be counted because we can't generated it at venus.

You could argue that we could with an established infrastructure on Venus build balloon skin, insulators, cooling system and power-plant initially, but this is a chicken and egg problem, for we need all that already to have the infrastructure to build all that. Unless of course we can build all that on the surface of Venus robotically, but if we do that it begs the question of why have humans on Venus (or in its clouds) to begin with.

You are still confuse with venus graphics clouds.

Inside of venus clouds you have a lot of visibility, becouse clouds are not so dense. But this does not means that far clouds does not look fluffy. In fact they would look equal fluffy at distance.

You never thoght a fog or a cloud at earth which looks so fluffy and closed, but when you are inside, you can see hundreds of meters, even other clouds in the sky?

But Verena and Pioneers probes showed it it be mostly haze, not clouds per-say, the particle sizes are too small throughout to produce clouds as we know them, fluffy and with different form. I've been in fog and you can't see "other clouds" inside fog, all you see is things further way getting foggier until they disappear in blankness, the view can be eerie. Of course a Venusian cloud city would have nothing else outside to look at so it would be surrounded by blankness. To get to a "cloud" layers where A) the clouds appear white and not yellow or orange or red and where differentiation can be seen and even C) blue sky's above, would require floating HIGHER than 50 km, even higher then 60 km, as close to the top of the upper cloud layers as possible. The altitude your proposing would be very dense fog/haze and red shifted with all the bluer spectrum light scattered by the higher layers making for an orange or even red sky, highly unpleasant sight to most people other than satanist(?)

[AngelLestat]

I wanna share a picture that I find about venus floating cities:

Why would you want to covert all the hydrogen in Venus? The energy costs of keeping a city cool, building insulator and cooling systems is going to be more than just making more lifting gas.

I am starting to think that is pointless to discuss with you. Or you dont understand the sentences, or you change the subject, but you will do anything to not said that you are wrong.

That is a big defect, becouse is an impediment to learn.

My point has been just refrigerating the city its self will require a lot of energy, that energy can't be gained back by any scheme in any significant amount and doing so adds only more mass. The heat difference of the city can't be used to provide energy, it must require energy, large amounts of energy by the laws of thermodynamics. Your city will be receiving significant amounts of heat via light (if its to grow plants) heat from industry, heat from conduction, convection and radiative heating from inside and outside the balloon skin, and no scheme is going to reduce this significantly without requiring a lot more mass and even violating thermodynamics. The technological solution you seek is to fly higher and achieve passive temperature control.

you can include a heat pump, or an absortion heat transfer process in the design of the city, so forget heavy machines.

If the city is very well planned from start, you can play with its big surfaces and volumes.

Controlling things like evaporation (extraction of heat), or venturi effects (also collling), with known physsics, You can make a passive heat pump that it would be big enoght like the city it self. Expending few materials. There are so many ways to extract energy, or how to use that energy that enters the city in your advantage.

You have been arguing that we should fly at an attitude that needs active cooling, I've been arguing we need to fly at an altitude that needs only passive cooling (to be more exact needs only passive heating) what ever the altitude may be, the lower the better, in fact if the detailed charts are wrong at at 50 km it is 0ºC that only makes my argument stronger for we need even less lifting gas and balloon capacity to maintain passive cooling/heating altitude.

I would disagree if not be by the fact that below 50 km the conditions of winds, pressure, or to harvesting water or acid are not ideal like at 50km.

So if we build balloons on the surface, we need to already have an industry on the surface for building balloons, probably highly or completely automated... why send people?

First, we dont wanna build ballons on the surface, only the insulators.

Send people? to where? to the surface or to venus?

You need people in the clouds to control all the operations in the surface or in the clouds it self.

What I'm proposing is we don't start with a surface infrastructure, we “land†the balloons first long before we build them at venus, and we build them at altitude forgoing the need to build balloon material that can survive being created and constructed at 500ºC and 92 atms of CO2.

Of course we dont start at the surface, like I said, first outpost are a higher altitude, get down in altitude becomes convenient if we are talking of big volumes. Its easier to deal with high temperatures with big volumes. Of course you dont go from 20C outposts to 66C cities over the night.. You start with 24C, 30C, the outpost become bigger and bigger. Until you have a city at 37C, then of course that continue.

And from my calculate, the volume over surface ratio continue growing with no stop at bigger scales. You reach a point when you want to make 2 cities with the same volume of air.

The volume difference is irrelevant: gas is cheap and can be made at Venus, but balloon skin, insulators, heat pumps, power plants can't and must be flown to Venus.

Also the envelope. THe ratio increase and you reach a point where you can not look to other side.

You need to consider how to construct your cloud city, first a set of balloons are sent to Venus that only need enough gas to float themselves and a small power plant, electrolysis/atmosphere extraction kit for extracting oxygen, if we assume 51 tons of balloons plus 49 tons of the aforementioned critical starting cargo then we need to lift only 100 tons initially, even though we have balloon capacity to lift 33 times more (assuming 100 g/m^2, 57 km altitude).

That is your problem, you are stuck in the first venus missions. Of course that if we still dont have infrastructure at venus it will be CRAZY try to make a 500mts radius city.

What this means it needs only "land" with 4.6 tons of hydrogen gas (or ~10 tons of helium) in order to float at 57 km. As the balloons fill more mass can be added via heavier then air cargo ships that fall via paraglider into the grappling line. The initial lifting capacity is 100 tons, but when completely filled the final lifting capacity of 51 tons of balloons at 100g/m^2 and 1/3 filled with breathable air, would be 3.3 kt. The paragliders from each cargo ship could potentially even be reprocessed into more balloons, but again we did not bring gas for them, no gas at all in that case, but instead we make all the lifting gas at Venus.

It reach a point where any big city would expell more oxygen that it use just using plants. But that does not mean that it has not value. Becouse if you reach that state, you need hundreds of different floating buildings to keep growing.

If we go for 50 km or an altitude where we need active cooling we would reduced the amount of hydrogen needed initially in half, but that only a few percents the total mass so we gain little, and yet we need to add the mass of a cooling system and power plant for that cooling system. So in conclusion the mass of the gas or volume of the balloon is not counted because we don't need to land with it, only a small fraction of it, the rest can be generated at Venus easily, yet the mass of a cooling system must be counted because we can't generated it at venus.

as you wish, I like to think and solve problems, so I find more interesting the heat approach.

But Verena and Pioneers probes showed it it be mostly haze, not clouds per-say, the particle sizes are too small throughout to produce clouds as we know them, fluffy and with different form. I've been in fog and you can't see "other clouds" inside fog, all you see is things further way getting foggier until they disappear in blankness, the view can be eerie.

I read Venus 1 book, Venus 2 book, and many other papers or studies. I never see any comments about measuments done by pionners of venera according to te things that you want to claim.

It works like I explain in the last post. If you are inside a cloud, you almost not notice, but you would see other clouds like solid at distance.

If you see satellites pictures of venus, its very obvious that there are places with more or less clouds.

[Rakaydos]

Lestat, what exactly is the problem with situating a colony at a thermally stable altitude- I'm unclear of your argument.

Most of what I've been seeing is Rubis suggesting minor revisions of Landis's plans, and you insisting that he is wrong in every particlar where he contradicts what you have read.

If it is easier to maintain a city at a thermaly stable altitude, why build a city at at any other altitude? If it isnt, why is it easier to build something and actively cool it, than build it at altitude and use the power for other things?

[RuBisCO]

I wanna share a picture that I find about venus floating cities:

artist interpretation. You refuse to admit that at the altitude your flying all your going to see is redish haze.

I am starting to think that is pointless to discuss with you. Or you dont understand the sentences, or you change the subject, but you will do anything to not said that you are wrong.

That is a big defect, becouse is an impediment to learn.

I'll admit I'm wrong when I'm wrong, but is it not possible your the one being stubborn about this, that you refuse to see the detriments floating at an altitude that requires active cooling?

you can include a heat pump, or an absortion heat transfer process in the design of the city, so forget heavy machines.

If the city is very well planned from start, you can play with its big surfaces and volumes.

Controlling things like evaporation (extraction of heat), or venturi effects (also collling), with known physsics, You can make a passive heat pump that it would be big enoght like the city it self. Expending few materials. There are so many ways to extract energy, or how to use that energy that enters the city in your advantage.

You can't make a passive heat pump that would violate physics. Certainly you can make ways to extracted energy, but cooling the city will always require energy, a lot of energy, and mass.

I would disagree if not be by the fact that below 50 km the conditions of winds, pressure, or to harvesting water or acid are not ideal like at 50km.

Explain how. Aside for a complete lack of evidence present for 'how', I see no reason that a balloon at 57 km can't also be connected to harvesting equipment at 50 km or any other altitude for that matter. You your self suggest so much in generating power by taping into the different velocities of the cloud layers.

First, we dont wanna build ballons on the surface, only the insulators.

Send people? to where? to the surface or to venus?

You need people in the clouds to control all the operations in the surface or in the clouds it self.

Exactly! And so we need to already have a colony started before we have the infrastructure to build a colony completely out of Venusian materials.

Of course we dont start at the surface, like I said, first outpost are a higher altitude, get down in altitude becomes convenient if we are talking of big volumes. Its easier to deal with high temperatures with big volumes.

No, no its not, this is your stubbornness, not mine and I agree it is pointless to argue with you about it anymore.

Of course you dont go from 20C outposts to 66C cities over the night.. You start with 24C, 30C, the outpost become bigger and bigger. Until you have a city at 37C, then of course that continue.

And from my calculate, the volume over surface ratio continue growing with no stop at bigger scales. You reach a point when you want to make 2 cities with the same volume of air.

Why? Why is it so necessary to conserve volume, even going so far as to replace it with heat? Why can't they simply build bigger volumes?

Also the envelope. THe ratio increase and you reach a point where you can not look to other side.

That is your problem, you are stuck in the first venus missions. Of course that if we still dont have infrastructure at venus it will be CRAZY try to make a 500mts radius city.

100 kt in 30x230 m balloons sounds pretty big to me, so no I don't think I'm stuck in a first mission mindset.

It reach a point where any big city would expell more oxygen that it use just using plants. But that does not mean that it has not value. Becouse if you reach that state, you need hundreds of different floating buildings to keep growing.

So?

as you wish, I like to think and solve problems, so I find more interesting the heat approach.

Well then might I recommend finding a way to live on the sun?

I read Venus 1 book, Venus 2 book, and many other papers or studies. I never see any comments about measuments done by pionners of venera according to te things that you want to claim.

It works like I explain in the last post. If you are inside a cloud, you almost not notice, but you would see other clouds like solid at distance.

Venus Revealed by David Harry Grinspoon.

If you see satellites pictures of venus, its very obvious that there are places with more or less clouds.

Yeah in the UPPER CLOUD layer, you want to live in the LOWER CLOUD layer

[Dodgey]

Ok, almost midnight here I will comment more later, what the hell does the Venturi effect have to do with this? And you keep asserting that you can just include a heat pump, I don't think that you have a sense of scale with this.

[RuBisCO]

Ok, almost midnight here I will comment more later, what the hell does the Venturi effect have to do with this? And you keep asserting that you can just include a heat pump, I don't think that you have a sense of scale with this.

Well I think you mean Angel, but I provided her with scale, showing that with a pure conduction model over a single layer of the ballon there will be GIGAWATTS of heat coming through, that even with aerogel just over the layers touching the city there will still be multiple megawatts of heat and then untold more megawatts from radiative and convective heating. Angel beleives that somehow somekind of scheme inside the habitat ballon can make up for the many megawatts of energy needed to cool the city and mass of hundreds of tons of heat pumps, there is no such thing, it would violate phyics, it would bring back less energy than carnot efficency would dictate which is 16-17%. All this stubernly refused for an ideal of floating at 50 km exact, for some reason. Why? why not 40 km with a good view of the sizziling surface and clouds above, and even more lift? Why not several ballons over ranging altitude, highest at passive heating temperature for the habitate, lower ones for industry that can operate at temps between 30-200°C, power can be generated from wind diffrentials (or heat differntials, although I would guess turbines would be lighter) Why she is hell bent on putting one singular ballon right on top of the redish haze at 50 km, I don't know.

Edited March 18, 2014 by RuBisCO

[Legendary Emu]

2cool2readalldahcomments

I think I know how to deal with the part where you are not on solid ground; Bring a bunch of guys that love star wars.

Also you could probably just stick really big balloons on really big sticks that go deeper into the atmosphere in a hexagon formation so that the city is stable and have another hexabloon formation that rises above the city to add stability.

[AngelLestat]

Sorry for delay, But I am too busy lately with my work.

Lestat, what exactly is the problem with situating a colony at a thermally stable altitude- I'm unclear of your argument.

Most of what I've been seeing is Rubis suggesting minor revisions of Landis's plans, and you insisting that he is wrong in every particlar where he contradicts what you have read.

If it is easier to maintain a city at a thermaly stable altitude, why build a city at at any other altitude? If it isnt, why is it easier to build something and actively cool it, than build it at altitude and use the power for other things?

The problem is that you lift half of the total payload for the same lifting gas volume. In other words, you get "half" city for almost the same cost. Remember than even at 50km, you only lift half kilogram for each m3 of air.

Of course is not easy to deal with the heat problem, but the true is that nobody try it to solve this before.. so we dont know all the possible solutions that can be waiting to be discover.

Also this is not a Rubisco idea. Is mentioned for the same Geoffrey Landis in the video that I post in the Terraforming topic, he said that probably we wanna be at a height where we can have a passive heat control.

But he dint talk much about that. THere is a big difference if we talk about a small outpost than a big city.

If you wanna deal with the heat you need to spend mostly in insulation on the envelope surface of course. But if we measure how the cost taking into account the evelope surface with the volume of gas that you would use. It give you a ratio of:

For a small outpost:

33-1

Small city:

330-1

Big City:

3300-1

Now you see? that is how the cost of gas volume grows in comparison with the envelope surface cost. Lets said that for a small outpost and a small city you find that is still cheaper the high altitude approach, but you will get a point "for sure" where is not.

What are the key elements for insulation?

-IR and UV reflective layers (super thin and cheap) / Or you can have a graphene composite layer tuned to convert into electricity those wavelenghts.

-aerogel (super effective, very cheap to produce in venus, super light)

-All the lights that plants does not absorb, you can have another graphene composite layer to transform in electricity the visible wavelenghts.

-A good design where your city and envelope shape would work like a huge heat pump.

-With a stratification approach you reduce in a 75% the amount of remaining heat to cool out. Also with this you dont lose lift power due to a low temperature insight.

And you dont need to go straight ahead from 55 km to 50km (in case the high temperature chart is correct) from one pasive cooling system to the other.

You can start reducing 1km at a time depending how big your city would be).

But the question here is not why I am against the high altitude aprooach (which I am not). Is why all you are against me when I am just trying to be creative here..

If we are here just to talk about things that we can copy and paste from other places, then what is the point???

There is a huge difference trying to discover something new when you are dealing with a problem that almost nobody deal before. it's not like trying to find a cancer cure, where millons of people try all years, this is a new problem and enviroment, the idea was recent spread. So there is a great chance to find solutions that never did before.

For example I have the idea of sky surfing in venus (using different altitude winds) to maintain a latitude (different from equator) against the meridional winds "2m/s to 6m/s", also how to harvester energy at night. "you would not find any solution to those problems in internet"

The stratification idea I still not sure if it would work, but well, is a different approach.

So again.. what is wrong in trying to search better solutions?

I'll admit I'm wrong when I'm wrong

I can make a list, you want? several times I prove you wrong and you never admit it. Not a good trait if you ask me.

Certainly you can make ways to extracted energy, but cooling the city will always require energy, a lot of energy, and mass.

Not mass, at least not in a substantially way.

Explain how. Aside for a complete lack of evidence present for 'how', I see no reason that a balloon at 57 km can't also be connected to harvesting equipment at 50 km or any other altitude for that matter. You your self suggest so much in generating power by taping into the different velocities of the cloud layers.

You see?? 50km is the perfect spot to gain energy from the high deltaV wind difference. Not only that, you can get high winds, low winds or both at the same time.

Also you are in the best zone to harvester sulfure acid (your most precious element in venus), in that place dodplets are bigger than at higher altitudes and you get more of them.

Plus more lift.

So? any word against "complete lack of evidence" ??

Exactly! And so we need to already have a colony started before we have the infrastructure to build a colony completely out of Venusian materials.

of course, so?? like in any place where you go.

100 kt in 30x230 m balloons sounds pretty big to me, so no I don't think I'm stuck in a first mission mindset.

30x230??? that is a surface data. you need to tell me the volume dimensions. 100kt?? 100000 Tons you said?

Well then might I recommend finding a way to live on the sun?

In close orbit? Easy, you just need to reflect the light and thats it.

Venus Revealed by David Harry Grinspoon.

what do you learn from that? can you quoted something interesting?

Ok, almost midnight here I will comment more later, what the hell does the Venturi effect have to do with this? And you keep asserting that you can just include a heat pump, I don't think that you have a sense of scale with this.

Well, seeing that Rubisco did not help in answer your question, you need to take into account that if you expand a gas, the temperature of the gas lower. For that reason when you use any spray, you notice that is very cold.

Venturi effect produce high velocity and low pressure, if you insulate all the path, less the part where the gas expand again, that part would absorb heat.

2cool2readalldahcomments

I think I know how to deal with the part where you are not on solid ground; Bring a bunch of guys that love star wars.

Also you could probably just stick really big balloons on really big sticks that go deeper into the atmosphere in a hexagon formation so that the city is stable and have another hexabloon formation that rises above the city to add stability.

Yeah, I was thinking more in a toroidal shape, but the weight and cost that you spend in the structure 2km or 3km to support the city, it may be similar or worst than just float higher.

---------------------------------

I read a preview of the Sultan of the clouds from Geoffrey landis, in that novel he talks about the venus cloud cities, he mention diamond aerogel (but also like a way to produce very lights fornitudes) and cities that are at very low height, but the preview is limited, so I can not see the way that geoffrey landis describe to deal with hot temperatures.

Heres is the preview (seems a very good story, he won some awards with that):

https://www.asimovs.com/2010_09/exc_story1.shtml

----------------------------------

Here there is a new design that I am doing of a cloud city. "is not finish"

I guess i am short in lifting volume. For this I would need a material 5 times more lighter than to day fiber carbon structures.

I post it, becouse I dont know if I would be able to finish with all the late work that I have now.

------------------------------------

This is how to move between different latitudes.

Height does not matter, you move with the wind. So your apparent wind it will be close to zero.

What it matters is your speed difference against different altitude winds. Those are your winds.

If you take 50km your zero potential value, at 48 km you would have a wind that blows at 15m/s in contrary direction against your movements (from surface), at 52 km you have 15m/s in your direction.

But like kites use the wing principle, the force that you get (if your kites are parallel to the wind speed) is normal.

You can harvester energy with the push force that the kite does, and then winding the rode to release it again.

------------------------------------------------

Sorry if my english was very bad in this last reply, I dint check the traductor.

Edited March 21, 2014 by AngelLestat

[Rakaydos]

The problem is that you lift half of the total payload for the same lifting gas volume. In other words, you get "half" city for almost the same cost. Remember than even at 50km, you only lift half kilogram for each m3 of air.

Of course is not easy to deal with the heat problem, but the true is that nobody try it to solve this before.. so we dont know all the possible solutions that can be waiting to be discover.

Also this is not a Rubisco idea. Is mentioned for the same Geoffrey Landis in the video that I post in the Terraforming topic, he said that probably we wanna be at a height where we can have a passive heat control.

But he dint talk much about that. THere is a big difference if we talk about a small outpost than a big city.

So, even though the guy who came up with the idea reconizes the thermal problem we keep pointing out to you, you insist on trying to defend an altitude that forces you to fight a losing battle against the laws of thermodynamics.

THAT is why everyone is ganging up on you. Because what you want goes against thermodynamics.

"If you think Einstein was wrong, I say, "tell me more". But if you think Thermodynamics was wrong, you are."

[kahlzun]

But the question here is not why I am against the high altitude aprooach (which I am not). Is why all you are against me when I am just trying to be creative here..

I believe that everyone appreciates your creative thought processes, and that you are trying to find a solution to a difficult problem.

What seems to be the crux of the argument is the concept that staying at one altitude is in some way better than, or in fact even competing with, each other.

Yes, staying at a height where passive cooling will work will simplify construction, but would require larger volume and thus bigger balloons.

Yes, lower balloons will be hotter, but smaller, and will be very difficult to keep cool.

Both approaches have benefits and drawbacks. Lets see if we can 'crunch' these numbers down a bit..

RuBisCo:

What material were you looking to have the balloon made out of, RuBisCo? How much more would just the balloon needed at the 55km height weigh, compared to the size needed for the 50km height? Lets look at both 'current' materials, and semi-theoretical 'future' materials (graphene and nanotubes or whatever)

AngelLestat:

Perhaps if you were able to explain the processes behind the heat/energy transfer Angel? You have shown that the lower balloon is highly insulated, how much heat transfer (and thus potential, maximum, electrical energy) will you get from your estimated 100-66 degree transfer at the top of the balloon? Also, how did you decide on those figures? Obviously the heat in the balloon would rise, and stratify, but to what extent?

What form of AC are you planning to use to cool the lower areas? Standard refrigerative? How much cooling can be provided can be calculated from the above 'potential maximum' energy transfer, if we know the efficiency of the cooling system: and therefore the area of the city we could cool to the 20 degrees you had on the diagram.

Edited March 21, 2014 by kahlzun

[RuBisCO]

RuBisCo:

What material were you looking to have the balloon made out of, RuBisCo? How much more would just the balloon needed at the 55km height weigh, compared to the size needed for the 50km height? Lets look at both 'current' materials, and semi-theoretical 'future' materials (graphene and nanotubes or whatever)

I believe I've stated this repeatedly now. At 100 g/m^2 would be about 500 tons for 30 spherical balloons 230 m wide (volume of 6.76 million m^3 per balloon), these being 20 filled with hydrogen made from H2SO4 in the clouds and the other 10 filled with breathable air consisting of 56% Oxygen and 43% Nitrogen at 0.37 bar made from H2SO4 and nitrogen pumped straight from Venus's atmosphere. Total lift capacity is 100 kt at 57 km altitude (about the weight of an aircraft carrier.) this being the estimated altitude were the outside air will be 10°C and thus 10°C bellow room temperature. The balloons weigh about 1/200 or 0.5% the total weight, future materials could of course reduce the balloon mass but as you can see that mass is already negligible even using a grossly overestimated 100 g/m^2. There are a variety of existing plastics that could be used to provide that level of performance, be resistant to sulfuric acid and be transparent. Heck we don't even need transparency for the hydrogen balloons. I would guess PVF could do the job. yes that right: enhanced beach ball plastic! In fact a "beach ball" skin thickness of 0.18 mm (standard for beach balls, which are between 0.15-0.3 mm) made out of PVF with a density of 1.78 g/ml would weight 101.1 g/m^2

This is all calculated via spreadsheet if you want a copy.

Edited March 21, 2014 by RuBisCO