Cloud cities

[visiontranstech]

Cloud city was an outpost and tibanna gas mining colony on the planet Bespin named as such because is was popularly surrounded by gaint cloud.

[Winter Man]

Anyone know what the insolation is at ~50km? The clouds are thick but it's that much closer to the sun.

[RuBisCO]

Anyone know what the insolation is at ~50km? The clouds are thick but it's that much closer to the sun.

I really recommend the book "Venus Revealed" by David Harry Grinspoon. 50 km puts us right in the middle of the clouds, even 60 km is just barely in the upper cloud layers. The clouds usually reach their thickest at ~50 km at least from the readings of the Venera and Pioneer Venus Probes. There some good to that, first off it reduces Venus's very bright sunlight (more then twice our solar flux), it also make solar panel aiming unnecessary for we could aim the panels straight down and still get power off the panels like we are on earth aiming straight at the sun! The probes also detected transients clearings here and there between cloud layers, so it is not like floating in the clouds would be boring scenery, now and then you would enter a clearing and be surrounded by extremely bright white fluff, it would be very romantic, aside for the whole 'acid melting off your face' factor.

Anyways there is alot still unknown about venus's clouds, we know only that sulfuic acid is a major component but we also know there other things in there, exactly what is still a mystery. We have a unknown UV absorber, we have Venera fantastic chlorine readings (only probes to directly capture cloud particles and try to decifer their composition), heck there could be life in those clouds, feeding off UV via an exotic photosythetic pathway, the point is the nucleus if the cloud particles is mystery.

There also mysteries about venus surface, for example all venus's highlands are coated in something radar reflective that literally sure as hell is not snow (because even on the mountain tops conditions are as horrify as hell)

All of these mysteries should be answered, especially ones in the clouds, before manned missions that float up there. Here a good reason why: http://www.wired.com/wiredscience/2013/04/vega-venus-rain/

Edited March 7, 2014 by RuBisCO

[AngelLestat]

Yes but what is the cost of maintaining a -55 K temperature difference?

-55? ... why I need to reduce the temperature -55 degres? Or maybe that is not the question, what is the ambient temperature that you want inside the city? Also, what is the chart temperature that you are looking at?

Heck with surface area of a balloon no less! Heat is transferring physically from the outside air to the balloon skin to the inside air, you need to add insulated layers to prevent this. All the extra weight in insulation and power plant and cooling system may make it worth it be a little higher! You can't radiate heat away either as the air around is emitting more IR radiation!

First, we can not talk until we clear the first question, becouse it seems that you have very different parameters than mine.

In your 60km case, yes, we would need insultation to not feel cold inside the city according to some charts.

But lets imagine that we want to have a low altitude. So we have to deal with extra heat.

First, there is not need to get insultation, the venus atmosphere has no much water, so the calorific power of co2 molecules is not so high, you just need to have an IR reflective layer (that is very thin), the common layer made to day for windows reflect the 90% of the IR, (graphene composites promise a lot more and it can be variable and tune it).

Also the heat of the city can escape, becouse the emitted IR has a long wave which differs from the one that you reflect. You can find a contraty behavior with a normal windows and sun, sun IR can pass, but the IR emited by the materials inside the room can not go out.

Besides, even that the surface envelope it would be big, the volume of air inside the envelope is much bigger. Adding the fact that air is a good insulator and you have 48hr of night to release the heat.

But this is not all you can do. You can encourage a stratification of the air inside the habitat. Hot air rise, cold air down, of course this is not simple, the low part of the envelope (city) needs to be insulated from external temperatures, and all city process which produce the bigger levels of heat needs to be channeled at the top of the envelope with middle points exist depending the temperature.

Like you dont have air flows or winds inside the envelope, it would remains pretty layered. So there is not need to withstand high temperatures from the first sun day, also moments before the night, the heat would rise your altitude helping you to cool it at night. Then the process starts again.

If still is the temperature level is not liked by some, they can cool their rooms, there is not need to cool all the city air.

As for making O2, that easy enough, a carbonate fuel cell can make O2 out of CO2 (actually it makes O2 on one side and CO on the other) the carbon monoxide we can dump or use in a *separate* balloon as lifting as gas, as good as nitrogen in lifting force. Nitrogen would need to be separated from venus atmosphere, a multiple stage CO2 scrubber could remove all the CO2 and nitrogen would be all that is left, plus trace gases, or we could go with good old fashion Liquefaction, but that may be more energy intensive.

Yeah, I hear that the CO can be more usefull than the CO2. About your previous calcs, yes, if you try to keep cool all the envelope your lifting power decrease and you would be wasting a lot of energy. So for that reason, all methods needs to be as passive like it can be.

Cloud city was an outpost and tibanna gas mining colony on the planet Bespin named as such because is was popularly surrounded by gaint cloud.

Yeah, that is Landon Carisiam city if I remember well. The first time that I see that in the movie, I thought that was an unrealistic idea

Anyone know what the insolation is at ~50km? The clouds are thick but it's that much closer to the sun.

If you dont wanna buy and read all the book that Rubisco suggest you,

You can check this post where you can find the graph that you are looking for.

http://forum.kerbalspaceprogram.com/threads/69572-Venus-terraforming-fact-checking-Chemistry-edition?p=970361&viewfull=1#post970361

aside for the whole 'acid melting off your face' factor.

Yes, you always need to be so drastic, but you know that if that happens it would take a long time with micro doplets.

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

So? anyone? how you do imagine the different habitats and floating outpost that a colony would need at venus? How you would manage it to launch a rocket from that height and recover it?

[RuBisCO]

-55? ... why I need to reduce the temperature -55 degres? Or maybe that is not the question, what is the ambient temperature that you want inside the city? Also, what is the chart temperature that you are looking at?

This chart you posted it says at 50 km that the temp is 350 K, that is 76.85°C or 170.33°F.

In your 60km case, yes, we would need insulation to not feel cold inside the city according to some charts.

Again I'm talking about 58-57 km, try to keep up. And again room temp is a few degrees above ambient we can maintain temp passively by having a lower albedo, which solar panels and plants will incur. So we want the surrounding air to be COLDER by like 5-20 K. We would need no insulation. Thermal energy from the sun or from the clouds themselves will be absorbed to keep the habitat warmer than the ambient air.

First, there is not need to get insultation, the venus atmosphere has no much water, so the calorific power of co2 molecules is not so high, you just need to have an IR reflective layer (that is very thin), the common layer made to day for windows reflect the 90% of the IR, (graphene composites promise a lot more and it can be variable and tune it).

Lets calculate heat conduction shalt we. Now we won't include radiative heating and convection, convection most certainly though would be a factor with a body the size of a Zepplin moving around in the winds of Venus's upper atmosphere

CO2 has a thermal conductivity of 0.0146 W/(m*K), lets say the balloon is a sphere and is 80 m wide (that would lift 100 tons at that altitude) it has a surface area of 20,126 m^2 lets assume the balloon is 0.1 mm thick and has a thermal conductivity equal to CO2 (less then a 1/12 PVC plastic, or a really good conductivity insulated material, it makes the calculation easier) the temperature difference is 55 K then the balloon is losing 1.6 GW per hour! And that not including convection!

Also the heat of the city can escape, becouse the emitted IR has a long wave which differs from the one that you reflect. You can find a contraty behavior with a normal windows and sun, sun IR can pass, but the IR emited by the materials inside the room can not go out.

Again we are talking about conduction with the air alone, not radiative heating, even if you could reflect all the IR radiation, ALL OF IT, the surface area with the air is so great that the heat conducted directly by thermal contact with the air is phenomenal!

Besides, even that the surface envelope it would be big, the volume of air inside the envelope is much bigger. Adding the fact that air is a good insulator and you have 48hr of night to release the heat.

How are you going to release heat if the air around you is so dam hot?

Yeah, I hear that the CO can be more usefull than the CO2. About your previous calcs, yes, if you try to keep cool all the envelope your lifting power decrease and you would be wasting a lot of energy. So for that reason, all methods needs to be as passive like it can be.

It can only be passive if your outside air is a little colder then the inside air. It a matter of logic here you can't be colder then outside air because of THERMAL CONTACT with it, the only way to be colder is a heat pump, there is no passive way to be colder than ambient! There absolutely no passive radiative way to do it or that would break thermal dynamics! You will have heat coming it, lot of it from thermal contact alone, you MUST have a heat pump to pump it out.

If the outside is colder though that a different story: now you can passively use the IR heat of the sun or the planet its self to heat your habitat, thermal dynamics are in your favor.

Yes, you always need to be so drastic, but you know that if that happens it would take a long time with micro doplets.

No one is going to want to go outside over there for any amount of time without protection, regardless if their face will melt off or not.

So? anyone? how you do imagine the different habitats and floating outpost that a colony would need at venus? How you would manage it to launch a rocket from that height and recover it?

I would say a lot of hydrogen made from the sulfuric acid would be very helpful, the reaction would be 2 H2SO4 → 2 H2 + O2 + 2 SO3. The energy required is very low, less then 1/3 what is required to water lysis. The SO3 would be dumped and the O2 would be breathing air and the hydrogen would be pumped into another balloon. At 57 km hydrogen has a lifting force of 660 g/m^3, nearly twice your air at 50 km. So this means for every m^3 of oxygen there will be ~2 m^3 of hydrogen in a separate purely lifting balloon. Of coursed that oxygen is cut with nitrogen so the ratio would be closer to 1:1 More so we can recycled oxygen with plants, hydrogen we would keep losing, so we would have to start dumping oxygen made to make up loss hydrogen.

Anyways I would figure a cloud city would be made of many balloons only some of them would be filled with breathable air for habitation, the rest would be hydrogen or even a few backup pure oxygen and breathing air balloons. I would imagine a structure somewhat like a zeppelin, long cylinder with floor space at the bottom, attach above would be many more balloons filled with hydrogen, back up air, oxygen, during altitude changes from day to night air would be pumped in/out the back-ups to keep the pressure in the habitat 'zeppelin' stable. Of course this zeppelin does not need motors, assuming venus's winds do not move it about it latitude much.

As for rocket launches back to earth... fat chance!

Edited March 7, 2014 by RuBisCO

[Rakaydos]

Hmm... instead of using Nitrogen, crack the sulfiric acid into oxygen and hydrogen, fuse the hydrogen into helium for power, and use helium and oxygen as breathing gasses.

[Red Iron Crown]

Gonna be tough to get enough helium that way. The mass of material actually fused in a fusion reactor is much smaller than one would expect intuitively. Plus, we'd need a functional fusion reactor, which is still a ways off as I understand it.

[Idobox]

As for rocket launches back to earth... fat chance!

I have tried to find the deltaV to get to orbit, but my google-fu is too weak.

Given the similar size and mass, I assume it would be close to Earth. We can probably assume something along 10 to 12km/s to reach an orbit higher than the atmosphere.

That being said, if you start at 50km, you save about 1km/s. Given the high density of the atmosphere, and the lack of solid launchpad, a spaceplane sounds like the best solution. Because of the lack of reactive species in the atmosphere, you would have to carry both oxidizer and fuel. An air augmented rocket, or nuclear thermal sound like the best options.

[RuBisCO]

The fusion option is completely unnecessary, it would produce very little helium, it would likely weigh ALOT!, hydrogen is already a better lifting gas and power is all plentiful in the clouds of Venus as solar power. Again in the clouds of Venus light levels during the day will generally be so high that you could face the panels any direction and get peak earth levels of sunlight. As long as they have enough battery/fuel cell power, to make it through the super-rotary night of 72 hours tops they are golden.

I have tried to find the deltaV to get to orbit, but my google-fu is too weak.

Given the similar size and mass, I assume it would be close to Earth. We can probably assume something along 10 to 12km/s to reach an orbit higher than the atmosphere.

That being said, if you start at 50km, you save about 1km/s. Given the high density of the atmosphere, and the lack of solid launchpad, a spaceplane sounds like the best solution. Because of the lack of reactive species in the atmosphere, you would have to carry both oxidizer and fuel. An air augmented rocket, or nuclear thermal sound like the best options.

Well yes of course lunching from height is way better then from the surface of venus, cooling the fuel is not as 'problematic', you reduce the amount of air you need to cut through, and your already at good height, but you still have like 7-8 km/s of delta-V to go! By the way ever used hooligans balloon mod to lift a rocket off of Eve and lunch it at altitude, it is fun as heck. Nuclear thermal would need to run off of CO2, which is a poor ISP propellant and also highly oxidizing and coke forming, it would be very technically challenging. It would make for a great rocket on mars though, you can land, pump up the fuel tanks with rarefied martian air and fly back to orbit, on Venus it may even be possible to make it self-compressing at least at lower altitude, a kind of nuclear jet engine, yes it most defiantly would need wings, but if it is reusable it would also need to have a thrust to weight ratio above 1 and be able to hoover to dock with the colony.

[AngelLestat]

This chart you posted it says at 50 km that the temp is 350 K, that is 76.85°C or 170.33°F.

What is wrong with all the other charts?

Most charts goes from 0 celcius at 50km, to 55celcius at 50km.

If you pick the one that said 55celcius at 50 km it means that you have 37 celcius at 52 km.

Of course this is one of the reasons why is so imperative to kept sending proves to venus, there is still a lot of things that we dont know and many other things that we still not sure.

Besides, understand Venus secrets is the holy grial to improve all climatological models on earth, also understand a little more about our possible fate with the greanhouse effect.

Again I'm talking about 58-57 km, try to keep up. And again room temp is a few degrees above ambient we can maintain temp passively by having a lower albedo, which solar panels and plants will incur. So we want the surrounding air to be COLDER by like 5-20 K. We would need no insulation. Thermal energy from the sun or from the clouds themselves will be absorbed to keep the habitat warmer than the ambient air.

In my opinion from all sources and things that I read, the most probably is that you would achieve that temperature difference at 55km. But even with that, I still believe that the extra cost of the air that you need to produce it would not be cost effective. But if you have an small outpost, then I would be agree.

CO2 has a thermal conductivity of 0.0146 W/(m*K), lets say the balloon is a sphere and is 80 m wide (that would lift 100 tons at that altitude) it has a surface area of 20,126 m^2 lets assume the balloon is 0.1 mm thick and has a thermal conductivity equal to CO2 (less then a 1/12 PVC plastic, or a really good conductivity insulated material, it makes the calculation easier) the temperature difference is 55 K then the balloon is losing 1.6 GW per hour! And that not including convection!

I only have practice with Radiation heat transfer calculations. But I was reading a bit, It seems that convection is the only way (if we discard radiation due to reflective coated) to transfer heat from a gas to solid.

And you need to take into account that the apparent wind speed that you got, is close to zero.

I dont understand how heat transfer really works from a gas to a solid. But I will read more tomorrow.

How are you going to release heat if the air around you is so dam hot?

Good point , I thought that I had this issue solve. But I forget that if I have a IR reflective coated to certain wave lenght, it means that I can not radiate heat in the same wave lenght.

But is not necesary if we get a good stratification. To get a good stratification we need to talk in big scales. Not a 100 Tons outpost. We need to talk about an envelope with 150mts or 200mts tall.

In this case, we can have a delta T difference of 60 or 100 degrees between the city and the top of the envelope "is a aproximation number based based in the delta T that we can achieve with 1,5mts of water coloum, of course the air density is a lot lower than water, but also the water thermal conductivity is higher"

Giving this you just need to cool the city area, but you would have extra lift due to an average higher temperature, until you find a thermal equilibrium.

You can use the thermal gradient to produce energy.

It can only be passive if your outside air is a little colder then the inside air. It a matter of logic here you can't be colder then outside air because of THERMAL CONTACT with it, the only way to be colder is a heat pump, there is no passive way to be colder than ambient! There absolutely no passive radiative way to do it or that would break thermal dynamics! You will have heat coming it, lot of it from thermal contact alone, you MUST have a heat pump to pump it out.

Like I explain above, I can reach a thermal equilibrium without violating any law. I recieve an amount of heat, and I will radiate the same amount of heat.

Also there is other ways to acomplish this without an average higher temperature using high tech, and other basic techniques.

For example we can play with the black body emmision coeficients to the envelope, or add extra layers with a gas between. We can use metamaterials, we already acomplish in laboratory one way heat transfer using a triagle nano shape. Also called heat diode.

But I dont like add technology so recent in the discussions which still we know so little.

I would say a lot of hydrogen made from the sulfuric acid would be very helpful, the reaction would be 2 H2SO4 → 2 H2 + O2 + 2 SO3. The energy required is very low, less then 1/3 what is required to water lysis. The SO3 would be dumped and the O2 would be breathing air and the hydrogen would be pumped into another balloon. At 57 km hydrogen has a lifting force of 660 g/m^3, nearly twice your air at 50 km.

Good to know. But i would like to add that hidrogen would have a lift power of 1,5kg/m3 at 50km.

So this means for every m^3 of oxygen there will be ~2 m^3 of hydrogen in a separate purely lifting balloon. Of coursed that oxygen is cut with nitrogen so the ratio would be closer to 1:1 More so we can recycled oxygen with plants, hydrogen we would keep losing, so we would have to start dumping oxygen made to make up loss hydrogen.

With the help of plants a city can produce extra oxygen and expel it to the atmosphere, we would not lose water, becouse this one would remain in the habitat.

Anyways I would figure a cloud city would be made of many balloons only some of them would be filled with breathable air for habitation, the rest would be hydrogen or even a few backup pure oxygen and breathing air balloons. I would imagine a structure somewhat like a zeppelin, long cylinder with floor space at the bottom, attach above would be many more balloons filled with hydrogen, back up air, oxygen, during altitude changes from day to night air would be pumped in/out the back-ups to keep the pressure in the habitat 'zeppelin' stable. Of course this zeppelin does not need motors, assuming venus's winds do not move it about it latitude much.

Some control is always welcome. Electric proppeled does not weight much. ANd you have plenty of energy.

I have tried to find the deltaV to get to orbit, but my google-fu is too weak.

Given the similar size and mass, I assume it would be close to Earth. We can probably assume something along 10 to 12km/s to reach an orbit higher than the atmosphere.

That being said, if you start at 50km, you save about 1km/s. Given the high density of the atmosphere, and the lack of solid launchpad, a spaceplane sounds like the best solution. Because of the lack of reactive species in the atmosphere, you would have to carry both oxidizer and fuel. An air augmented rocket, or nuclear thermal sound like the best options.

Hi idolox, from the surfuce your delta v would be close to 20 or 24km/s, At surfuce it would be like if you would be in a fluid that is as 1/3 or 1/5 the water density.

But there is not much complications to reach orbit from 50km. From there you need to calculate that gravity as Venus diameter are lower, so this imply a good reduction of delta v against earth.

We can launch a rocket from a floating plataform from 60km or 65km, the rocket once deploy the payload at orbit fall agains, and the emply tank with engine and rocket structure would have a low density, enoght to float at 40km of height (4kg/m3) with little help maybe after reentry, You can have a bit amount of liquid amoniac inside the rocket to help against presssures. With the heat of the atmosphere at 45km, the amoniac evaporates and counter outside pressure. Then you can send the plataform (with variable buyancy) to recover the rocket.

As long as they have enough battery/fuel cell power, to make it through the super-rotary night of 72 hours tops they are golden.

You can get energy from the wind very effective using the different wind speeds from 47km layer to the 51km layer without add complexity to your city.

Edited March 9, 2014 by AngelLestat

[Dispatcher]

... Of course this is one of the reasons why is so imperative to kept sending proves to venus, there is still a lot of things that we dont know and many other things that we still not sure. Besides, understand Venus secrets is the holy grial to improve all climatological models on earth, also understand a little more about our possible fate with the greanhouse effect. ...

I agree that we need to send more probes to Venus in order to continue learning more about it. There is what I consider to be "the elephant in the room" that I seldom, if ever, read in science literature on the subject of a greenhouse effect in connection with our sister planet. Its the fact that Venus' day is longer than its year. In general terms, its a lot like Earth in its structure, including its core, or so it would seem as Earth and Venus are of similar terrestrial size, density and mass. If its axial rotation had not been altered by the impact of a massive object long ago (suggested in its extremely slow retrograde rotation), its rotation would drive the generation of an electromagnetic field similar to Earth's. I think that any lack of thermal convection in the core does not preclude its presence in a former epoch. Rotation and an active EM field in turn would help shield it from the sun's radiation and drive its weather and instill tectonic systems. This would in turn allow for the absorption of CO2 from the air (and reduce surface pressure), and would have allowed the planet to retain much more (or all) of its water. In short, Venus would be a warm but not hostile environment for us to study; at least not in comparison with its current situation. So, when trying to understand Earth in comparison to Venus, regarding greenhouse gases, we need to remember that in the context of the length of each world's day.

[RuBisCO]

What is wrong with all the other charts?

Most charts goes from 0 celcius at 50km, to 55celcius at 50km.

If you pick the one that said 55celcius at 50 km it means that you have 37 celcius at 52 km.

It is best to start off with the worse values not hope the best ones are true. And again 37°C would still require a heat pump as most people don't like living in that kind of heat and the habitat will invariably be hotter.

Of course this is one of the reasons why is so imperative to kept sending proves to venus, there is still a lot of things that we dont know and many other things that we still not sure.

Besides, understand Venus secrets is the holy grial to improve all climatological models on earth, also understand a little more about our possible fate with the greanhouse effect.

No contention there.

In my opinion from all sources and things that I read, the most probably is that you would achieve that temperature difference at 55km. But even with that, I still believe that the extra cost of the air that you need to produce it would not be cost effective. But if you have an small outpost, then I would be agree.

What ever, all that matters is the habitat has to be warmer then the surroundings, not colder, by enough to allow passive cooling.

I only have practice with Radiation heat transfer calculations. But I was reading a bit, It seems that convection is the only way (if we discard radiation due to reflective coated) to transfer heat from a gas to solid.

And you need to take into account that the apparent wind speed that you got, is close to zero.

No conduction is what is occurring, it just without convection the layers of air will insulate each other, if we assume a layer of air several meters thick and not 0.1 mm heat conduction drops by orders of magnitude, this of course is impossible as any heat gradients will induce some level of convection allowing different layers to air to conduct as one. With bodies the size of zeppelins convection along it skin is assured. The height difference within the balloon it self will create currents that move air around transferring heat from low to high, the same will occur on the outside skin. As for winds, we know nothing of wind dynamics at those altitudes, for all we know there are none... or there are crosswinds blasting around like a hurricane. In short attempting to insulate something of that size against a hotter outside is going to weigh so much in insulation, heat pumps and power source to to negate the lifting advantage.

I dont understand how heat transfer really works from a gas to a solid. But I will read more tomorrow.

The same as how heat transfers from any atom to any other atom: atoms touch or hit a each other transferring energy (conduction), atoms give of EM radiation that are absorbed by other atoms (radiative), but because we have a fluid we have an added mechanism in which heat is motion and heat can transfer (via conduction) in groups of atoms to a surface rather then just random individual interactions.

But is not necesary if we get a good stratification. To get a good stratification we need to talk in big scales. Not a 100 Tons outpost. We need to talk about an envelope with 150mts or 200mts tall.

In this case, we can have a delta T difference of 60 or 100 degrees between the city and the top of the envelope

How? Don't we need heights of kilometers to get that difference?

You can use the thermal gradient to produce energy.

How much energy? Thermal towers on earth need to be a kilometer tall and have many kilometers of base heating in order to get up 100 MW, with the distance your talking about I would think only a few hundred kilowatts at best with the added noise of having all these fan generators in the habitat. Worse if your achieving this because the habitat is cooler then your only making back a small amount of energy that you have to put in to maintain coolness.

Like I explain above, I can reach a thermal equilibrium without violating any law. I recieve an amount of heat, and I will radiate the same amount of heat.

Thermal equilibrium means being at the the SAME temperature as the surroundings, that means living at 55°C! It would violate the laws of physics to maintain a lower temperature without a heat pump that requires workable energy.

Also there is other ways to acomplish this without an average higher temperature using high tech, and other basic techniques.

For example we can play with the black body emmision coeficients to the envelope, or add extra layers with a gas between. We can use metamaterials, we already acomplish in laboratory one way heat transfer using a triagle nano shape. Also called heat diode.

Again you can't violate physics, even "heat diodes" require electrical energy in order to pump heat in one direction.

Good to know. But i would like to add that hidrogen would have a lift power of 1,5kg/m3 at 50km.

And again to live at that altitude will require all the extra weight of insulation, heat pumps and power plants. What is more expensive: more gas volume or magical hyper-insulators, heat pumps and powerplants?

With the help of plants a city can produce extra oxygen and expel it to the atmosphere, we would not lose water, becouse this one would remain in the habitat.

We can make water form H2SO4 as well so that not really a big concern.

Some control is always welcome. Electric proppeled does not weight much. ANd you have plenty of energy.

Sure why not, but where are they going? It is for attitude control, is it for changing latitude or is it for actually holding position because the amount of "control" needed for each increases exponentially.

Hi idolox, from the surfuce your delta v would be close to 20 or 24km/s, At surfuce it would be like if you would be in a fluid that is as 1/3 or 1/5 the water density.

But there is not much complications to reach orbit from 50km. From there you need to calculate that gravity as Venus diameter are lower, so this imply a good reduction of delta v against earth.

The reduction is minor, Venus's gravity is 90% earths so the reduction in delta v is going to be ~10% that over earth.

We can launch a rocket from a floating plataform from 60km or 65km, the rocket once deploy the payload at orbit fall agains, and the emply tank with engine and rocket structure would have a low density, enoght to float at 40km of height (4kg/m3) with little help maybe after reentry, You can have a bit amount of liquid amoniac inside the rocket to help against presssures. With the heat of the atmosphere at 45km, the amoniac evaporates and counter outside pressure. Then you can send the plataform (with variable buyancy) to recover the rocket.

That not a bad idea now all you need is ammonia factory floating +50 km above Venus and high thrust to weight nuclear thermal rockets in a reusable space-plane-o-zeppelin.

You can get energy from the wind very effective using the different wind speeds from 47km layer to the 51km layer without add complexity to your city.

Aside for having to deal with the torsion and strain to the city, oh about winds, once you do that your city is now going to be moving against winds, lots and lots of convection.

I agree that we need to send more probes to Venus in order to continue learning more about it. There is what I consider to be "the elephant in the room" that I seldom, if ever, read in science literature on the subject of a greenhouse effect in connection with our sister planet. Its the fact that Venus' day is longer than its year. In general terms, its a lot like Earth in its structure, including its core, or so it would seem as Earth and Venus are of similar terrestrial size, density and mass. If its axial rotation had not been altered by the impact of a massive object long ago (suggested in its extremely slow retrograde rotation), its rotation would drive the generation of an electromagnetic field similar to Earth's. I think that any lack of thermal convection in the core does not preclude its presence in a former epoch. Rotation and an active EM field in turn would help shield it from the sun's radiation and drive its weather and instill tectonic systems. This would in turn allow for the absorption of CO2 from the air (and reduce surface pressure), and would have allowed the planet to retain much more (or all) of its water. In short, Venus would be a warm but not hostile environment for us to study; at least not in comparison with its current situation. So, when trying to understand Earth in comparison to Venus, regarding greenhouse gases, we need to remember that in the context of the length of each world's day.

Actually it was earth that got it rotation from a world colliding impact (that made the moon) not the other way around, where venus got its rotation is unknown. What is theorized for Venus is that it did not get that impact, solar winds stripped off all its hydrogen from its water, without water its geosphere lacked the "lubricant" to from tectonic activity. But all this is frankly supposition based on what very little we do know about Venus. The very first space probes we should send should be aerobots, just a few days spent in the clouds with a GC-MS and some other instruments for determining what the clouds are really made of, surface to core of the particles, would really go a long way. Longer term operation may be possible in the clouds in fact this discussion has brought up ideas for how to sustain not manned but also unmanned outposts in the clouds. A little solar power hydrogen ballooned aerobot with a small electrolysis kit could remain operation until something punctures it balloon such it can't make up the losses with electrolysis hydrogen (lightning perhaps, there is some evidence for it on venus)

Edited March 9, 2014 by RuBisCO

[Dispatcher]

... Actually it was earth that got it rotation from a world colliding impact (that made the moon) not the other way around, where venus got its rotation is unknown. What is theorized for Venus is that it did not get that impact, solar winds stripped off all its hydrogen from its water, without water its geosphere lacked the "lubricant" to from tectonic activity. But all this is frankly supposition based on what very little we do know about Venus. ...

Actually, both Earth and Mars were struck by large objects. However, their axial spins (very similar periods, BTW), and that of Mercury, are prograde. What are the odds that both "got" their spin from those impacts, and in the same orientation? While impacts probably affected the spins, the odds reflect that these would have existed without the impacts. The mass from which the sun and its planets formed had its own rotation. Venus is the only terrestrial body with a retrograde rotation. You indicate that Venus' source of rotational direction is unknown; true in terms of certain data, however the fact of the slow retrograde rotation supports the possibility of an impact, which I think is the likely cause and thus probable.

We do agree that more data is needed and thus more probes.

[AngelLestat]

Rotation and an active EM field in turn would help shield it from the sun's radiation and drive its weather and instill tectonic systems.

Scientists has doubts about the rotation speed being the only problem to lack of a magnetic field (not even a little!).

Some believe that the core is not solid due to the high internal heat (by radioactive elements).

What ever, all that matters is the habitat has to be warmer then the surroundings, not colder, by enough to allow passive cooling.

It does not matter what is the outside temperature or the inside temperature, the only that matters is that you expell the same amount of heat you receive and produce.

With bodies the size of zeppelins convection along it skin is assured. The height difference within the balloon it self will create currents that move air around transferring heat from low to high, the same will occur on the outside skin. As for winds, we know nothing of wind dynamics at those altitudes,

I was just pointing in case you was using a formule which take into account the wind speed.

Even that you are traveling at the same wind speed, of course you would have always air flow moving around. But I guess they would be less than 0,5m/s.

The same as how heat transfers from any atom to any other atom: atoms touch or hit a each other transferring energy (conduction), atoms give of EM radiation that are absorbed by other atoms (radiative), but because we have a fluid we have an added mechanism in which heat is motion and heat can transfer (via conduction) in groups of atoms to a surface rather then just random individual interactions.

I dont know.. In that case you need to have into account the Heat capacity of the gas, that is very small.

How? Don't we need heights of kilometers to get that difference?

I can only talk using common sense and some previous experiences in widespread rooms with AC or heating sources.

Becouse there is not a practical use or need for this concept yet.

But I can give you sources of this same concept but with water instead air.

For example Solar thermal collectors needs always exchange temperature with cold water to improve the efficiency. Also helps a lot to heat a small part of the boiler and not the full boiler to start use hot water. So distribute the heat in layers is very effective in this case.

This is a case study:

http://task32.iea-shc.org/data/sites/1/publications/task32-d2.pdf

This is one of the products for sale

http://energiaesole.eu/index2.php?lang=en&pag=sole_gas

Heres mention the normal case difference between top and bottom in this tanks 80C of dt. http://en.wikipedia.org/wiki/Hot_water_storage_tank

How much energy? Thermal towers on earth need to be a kilometer tall and have many kilometers of base heating in order to get up 100 MW

Ehh? where do you get those numbers? Why 1km??

Thermal equilibrium means being at the the SAME temperature as the surroundings, that means living at 55°C! It would violate the laws of physics to maintain a lower temperature without a heat pump that requires workable energy.

You almost not need to inject energy to keep cold your surface city. It would work like this:

Lets imagine a egg-shape envelope with 2 layers (not extra materials need it), instead had 1 layer with X thick to support the city weight, you divide that layer thick into 2.

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.

You set a good insultaion in the bottom, and a bad insultation on top. For this you need a low emissivity layer (for IR in the 66C wavelenght) at bottom and a high emissivity layer at 70C-100C variable from half to top.

Also an extra conductive insulator at city base (but the same air between the 2 layer envelope works like a good insulator.)

(better configurations of emissivity and reflective coeficients between layers are for sure possible, but I let that to someone with better thermodinamic undestandings)

The key of this system is to extract air from the height that you most think convenient and drop it (with its temperature increase it) to the height that has a similar temperature (never mix temperatures).

So you dont have vertical wind flows, and air is a very bad heat conductor. So you only need an small AC (becouse you would have always some energy loses) to cold the city, and that´s all.

You find your thermal equilibrium between outside and inside, no thermodinamic laws is violated.

You can use the extreme heat at the top to get energy, for example heat water to cook or other process.

Or a rankine cycle and produce electricity.

Also you dont lose lifting power with this method.

Again you can't violate physics, even "heat diodes" require electrical energy in order to pump heat in one direction.

No they dont. If you have a heat engine which converts a heat difference directly into electric power you are not violating any law. And that would be a heat diode.

Or a heat pipe.

Also, you will find this interesting:

http://www.hngn.com/articles/23141/20140128/controlling-heat-flow-new-technology-could-allow-thermal-management-in-computers-buildings-and-even-clothing.htm

Sure why not, but where are they going? It is for attitude control, is it for changing latitude or is it for actually holding position because the amount of "control" needed for each increases exponentially.

Is not for altitude control, is for latitude control in case you needed to receive materials from the surface.

The reduction is minor, Venus's gravity is 90% earths so the reduction in delta v is going to be ~10% that over earth.

But you forget that the diameter is also smaller. Why you need very low speed to enter in Kerbin low orbit if the gravity is the same?

The same for saturn, it has similar gravity than earth, but its orbit speed its very fast.

Aside for having to deal with the torsion and strain to the city, oh about winds, once you do that your city is now going to be moving against winds, lots and lots of convection.

The thermal equilibrium is the same, like you see in the graph. If I gain heat faster, you also lost it faster on the top.

But dont get me wrong, I would like to be at a height where someone can go outside with propper cloth and not feel so much hot.

how to sustain not manned but also unmanned outposts in the clouds. A little solar power hydrogen ballooned aerobot with a small electrolysis kit could remain operation until something punctures it balloon such it can't make up the losses with electrolysis hydrogen (lightning perhaps, there is some evidence for it on venus)

If you find something that punctures it, that would be a hell of discovery. I imagine scientist discussing and imaging what could cause that. Life at venus clouds is not totally discard it by scientist.

Edited March 10, 2014 by AngelLestat

[RuBisCO]

It does not matter what is the outside temperature or the inside temperature, the only that matters is that you expell the same amount of heat you receive and produce.

No heat differentials matter, if not it would be possible violate thermodynamics. As such if the outside is hot your going to have heat coming in and your going to have to spend energy just to pump heat out. So that expelling heat received and produced is going to be very expensive energetically.

I was just pointing in case you was using a formule which take into account the wind speed.

Even that you are traveling at the same wind speed, of course you would have always air flow moving around. But I guess they would be less than 0,5m/s.

That is just a guess, for all we know winds on venus are not consistant and there is much up and down drafting, the vega aerobots showed this to be the case. Worse would be traveling droping a line several kilometers down to generate energy on different wind layers, this would put drag on the whole habitat causing it to experience apparent wind.

I dont know.. In that case you need to have into account the Heat capacity of the gas, that is very small.

But we are talking about a surface area of thousands if not millions of m^2, low heat capacity and heat conductance of CO2 gas are completely made up for by that. Also we have not considered the possibility of sulfuric acid condensation on the surface what what they will do, beside add weight it would also likely add to heat transfer.

I can only talk using common sense and some previous experiences in widespread rooms with AC or heating sources.

Becouse there is not a practical use or need for this concept yet.

But I can give you sources of this same concept but with water instead air.

For example Solar thermal collectors needs always exchange temperature with cold water to improve the efficiency. Also helps a lot to heat a small part of the boiler and not the full boiler to start use hot water. So distribute the heat in layers is very effective in this case.

This is a case study:

http://task32.iea-shc.org/data/sites/1/publications/task32-d2.pdf

This is one of the products for sale

http://energiaesole.eu/index2.php?lang=en&pag=sole_gas

Heres mention the normal case difference between top and bottom in this tanks 80C of dt. http://en.wikipedia.org/wiki/Hot_water_storage_tank

Ehh? where do you get those numbers? Why 1km??

That water not gas, for the case of gas you need height deferential of hundreds of meters.

http://es.wikipedia.org/wiki/Torre_solar

“La máxima potencia eléctrica que puede desarrollar el diseño es de hasta 200 MW. La chimenea solar propuesta inicialmente debía medir 1 kilómetro de alto, y la base 7 kilómetros de diámetro, con una superficie de 38 km². La chimenea solar extraería así cerca del 0.5% de la energía solar (1 de kW/m²) que fuese irradiada en el área cubierta.â€Â

You almost not need to inject energy to keep cold your surface city. It would work like this:

Lets imagine a egg-shape envelope with 2 layers (not extra materials need it), instead had 1 layer with X thick to support the city weight, you divide that layer thick into 2.

http://s20.postimg.org/610gz5hj1/layered_heat_city_envelope.jpg

You guaranteedly by the laws of thermaldynamics must, MUST spend more energy cooling your city then you would get back from this scheme.

You need to bring all that extra weight of insulators, of heat pumps, of radiators to the outside, of power plants to power it to venus... or we could just float higher for 2-3 times the gas (made from venus) and NOT have to carry all those extras. Which costs more: gas or insulated balloons, heat pumps, radiators, and power plants? I would guess gas is the cheaper option, single layer balloon surface can be cheap and light, even transparent or translucent for plant growth, the weight savings in NOT having to lift AC, radiators, power plants, may make up for the higher altitude.

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.

Great, no plant growth for food.

Also an extra conductive insulator at city base (but the same air between the 2 layer envelope works like a good insulator.)

(better configurations of emissivity and reflective coeficients between layers are for sure possible, but I let that to someone with better thermodinamic undestandings)

The key of this system is to extract air from the height that you most think convenient and drop it (with its temperature increase it) to the height that has a similar temperature (never mix temperatures).

So you dont have vertical wind flows, and air is a very bad heat conductor. So you only need an small AC (becouse you would have always some energy loses) to cold the city, and that´s all.

Oh sure your just exchanged AC for insulators, lots of insulators, and again low heat conductivity of are is completely made up for and then some by the incredible surface areas your working with as I showed. Your going to need many, heavy insulating layers, your going to need AC, your going to need power plants and your going to need radiators.

You find your thermal equilibrium between outside and inside, no thermodinamic laws is violated.

You can use the extreme heat at the top to get energy, for example heat water to cook or other process.

Or a rankine cycle and produce electricity.

You must spend more energy cooling your city then your get back as electricity, or else thermodynamics are violated.

No they dont. If you have a heat engine which converts a heat difference directly into electric power you are not violating any law. And that would be a heat diode.

Or a heat pipe.

Your violating thermaldynamics if your get more energy back then you put in, to maintain a temperature difference, you must MUST spend energy, not receive energy. So to cool the city will by the laws to thermodynamics cost more energy then you can get back by any scheme.

Also, you will find this interesting:

http://www.hngn.com/articles/23141/20140128/controlling-heat-flow-new-technology-could-allow-thermal-management-in-computers-buildings-and-even-clothing.htm

So? This system spends energy, and costs weights and money, any system will spend energy, and weight and cost money.

Is not for altitude control, is for latitude control in case you needed to receive materials from the surface.

http://1.bp.blogspot.com/-v7O23tj8Zsc/TWGRmC_jU8I/AAAAAAAAAv8/cLZ3rm8z-Jk/s1600/VCM+drift.bmp

Well that going to add weight too, lots of it, just to move a structure of this size as several kmh is going to be costly.

But you forget that the diameter is also smaller. Why you need very low speed to enter in Kerbin low orbit if the gravity is the same?

The same for saturn, it has similar gravity than earth, but its orbit speed its very fast.

Kerbin... I was talking about Venus, Venus has nearly the same diameter as earth.

The thermal equilibrium is the same, like you see in the graph. If I gain heat faster, you also lost it faster on the top.

But dont get me wrong, I would like to be at a height where someone can go outside with propper cloth and not feel so much hot.

Again thermal equilibrium would push for everything being the same temperatures as the surroundings, maintaining a temperature other then the surroundings costs energy, maintaining a cooler temperature will require insulators, heat pumps, power plants, maintaining a higher temperature will require only a lower albedo nothing more, no insulators, not heat pumps not power plants for those heat pumps, no radiators.

As for this romantics notion of going “outsideâ€Â, to do what exactly, look over a rails at a sky of completely white bright blankness? A venus city would spend most of its time floating a haze of completely white blankness (inexpresividad blanco) if their lucky maybe there are openings in the haze now to a small clearing in the clouds, but it likely not even fluffy clouds would ever by visible, just endless whiteness. It would be a completely dreary existence suited for a penal colony with no escape but to fall into hell.

If you find something that punctures it, that would be a hell of discovery. I imagine scientist discussing and imaging what could cause that. Life at venus clouds is not totally discard it by scientist.

Well over times the balloon skin is going to degrade from UV light, from sulfuric acid, from what ever other chemical corrosion there is, from lightning perhaps, still inconclusive if that exist on Venus, I was not meaning wildlife would perforate it.

Edited March 10, 2014 by RuBisCO

[AngelLestat]

That is just a guess, for all we know winds on venus are not consistant and there is much up and down drafting, the vega aerobots showed this to be the case. Worse would be traveling droping a line several kilometers down to generate energy on different wind layers, this would put drag on the whole habitat causing it to experience apparent wind.

I know about the Vega ballons case, it was just a change of altitude that dint last much and it was the only measure between all ballons missions.

Again, I said less than 0,5m/s (like average). But it will not matter in this discussion.

That water not gas, for the case of gas you need height deferential of hundreds of meters.

who tell you that?? where do you get that info?

http://eeasolar.com/blog/wp-content/uploads/2014/01/Infarot_9.jpg

http://www.thermalimageuk.com/userimages/hot%20air%20balloon%20thermal%20image%20(4).jpg

And that is just the envelope temperature, the air inside the ballon goes from 40 to 100C in few meters. Besides the burner every time that fire it mix the air, so is not a good example for a stratification experiment.

Like you saw in the water experiment you can have 50 degress in difference (or more) in just 10cm. So I was being very conservative with my values.

For sure you can have more than 3 times that delta T in 200 mts.

All this without take the fact that water has a lot thermal conductivity than air. But here what matter most, is convective. And hot fluids always rise.

http://es.wikipedia.org/wiki/Torre_solar

I know very well all eco-friendly technologies, that is what I would do (analizing) for living in shorted.

But it has nothing to do with the thing that we are talking about. Why are you mention this???

You guaranteedly by the laws of thermaldynamics must, MUST spend more energy cooling your city then you would get back from this scheme.

You're not understanding...

You need to bring all that extra weight of insulators, of heat pumps, of radiators to the outside, of power plants to power it to venus... or we could just float higher for 2-3 times the gas (made from venus) and NOT have to carry all those extras. Which costs more: gas or insulated balloons, heat pumps, radiators, and power plants? I would guess gas is the cheaper option, single layer balloon surface can be cheap and light, even transparent or translucent for plant growth, the weight savings in NOT having to lift AC, radiators, power plants, may make up for the higher altitude.

Extra weight of insulators?? heh.. The main characteristic of any good insulator is "light", if they are not light, they are not good insulators.

One of the best is Aerogels.

Heat pumps? Power plants? Radiators? You need to put some effort to understand what I am saying before try to search a flaw.

The AC it does not need to be so big, is just to compensate some heat mix that would start to happens in weaks or months, becouse there is no perfect process. So is only to reinforce the stratification.

And it would took energy from outside of course. Winds, solar panels, or heat difference between the top envelope and the outside, etc.

Great, no plant growth for food.

??? Plants does not need UV to growth. In fact they are better without UV. They use just visible light.

You must spend more energy cooling your city then your get back as electricity, or else thermodynamics are violated.

Is all in the graphic... Is not so difficult to understand...

I'll make it simple for you, forget for one second about all the insulation and the different IR layers, AC, etc.

Now you have two environments, "outside" and the "city envelope". All the radiation and heat by convection and conductivity equals temperatures. Now imagine that you are in a small room in this city, you just cold down the room. To do this you need to counter all energy that the city is receiving?? No.

Why? becouse it only matters the heat received and expelled by the system, they need to be equal or temperature rise, or down (there is not violating in this process); but when we talk about equal temperatures between enviroments we are talking of average temperature!, you can have many different temperatures inside the envelope and you would not violate any law meanwhile your average temperature is the same that outside.

Now you can have a lot of insulators and reflect almost all heat, you just receive 1kw of heat in the whole envelope, if you manage to radiate the same 1kw of energy to outside, you have equilibrium. Doing this you can have any temperature you want. Or maybe you expend extra energy extracted from outside, and you keep cooling the inside until you reach almost 0 absolute. (you are not violating any law).

So returning to the stratification idea. Here if your average temperature inside is equal to outside, you would exchange the same energy that you receive. But you can take advantage that hot air rise and cold air downs. Encouraging this process with vent methods and some insulating in the right places, you can have an area where your temperatrue is low and another area where the tempearature is higher to compensate.

Is clear enoght?

Well that going to add weight too, lots of it, just to move a structure of this size as several kmh is going to be costly.

You know how many times you said in this mail the words: weight, cost, lots, violating; between others? Try to be more positive, problems are easy to solve

Using the same "parachute" that I mention to produce drag, then energy from the parachute and proppelers. Is the thing that you need to maintain latitude in conjunction with rudder, without expend electricity (also if you are in the equator you dont need it).

How? In the same way that kite surfing.

Kerbin... I was talking about Venus, Venus has nearly the same diameter as earth.

No, I said that venus low orbit is easier to reach due to 0,9 g and venus diameter, and you said that only is a 10% of reduction due to gravity.

Now I said again, is not only for gravity, is also for diamenter, and you have a 0,9 of earth diamenter.

Both parameters matter in equal proportions.

If we have an hypothetical planet of 3 meters of diamenter with a surfuce gravity of 9,8m/s2, then we can enter in orbit with just a jump.

As for this romantics notion of going “outsideâ€Â, to do what exactly, look over a rails at a sky of completely white bright blankness? A venus city would spend most of its time floating a haze of completely white blankness (inexpresividad blanco) if their lucky maybe there are openings in the haze now to a small clearing in the clouds, but it likely not even fluffy clouds would ever by visible, just endless whiteness. It would be a completely dreary existence suited for a penal colony with no escape but to fall into hell.

You need to go outside to assemble things, maintenance, fly to other cities, go to work to other stations, it can be a scientific station, or the rocket launcher station... or maybe just becouse you wanna go out and fly over there.

Completely white blankness??? You are almost in the bottom of the clouds. I would said that days are almost as shiny like a sunny day at earth.

http://www.astro.uni-bonn.de/~dfischer/venus/

http://www.cyberphysics.co.uk/topics/radioact/Radio/EMSpectrumcolor.jpg

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

I found a good link about pros and cons for Cloud Cities in Venus. Is very complete.

http://www.science20.com/robert_inventor/will_we_build_colonies_float_over_venus_buckminster_fullers_cloud_nine-127573

It has good information with quality links.

Here explain a possible transportation model for venus.

http://www.clowder.net/hop/railroad/Venus.html

Edited March 11, 2014 by AngelLestat

[RuBisCO]

I know about the Vega ballons case, it was just a change of altitude that dint last much and it was the only measure between all ballons missions.

Again, I said less than 0,5m/s (like average). But it will not matter in this discussion.

And again that purely a guess.

who tell you that?? where do you get that info?

I've provided a link and quote, what more do you want?

Like you saw in the water experiment you can have 50 degress in difference (or more) in just 10cm. So I was being very conservative with my values.

For sure you can have more than 3 times that delta T in 200 mts.

And how much energy is required to maintain the stratification? A hot air balloon burns a lot a fuel for example. I'm really baffled at how you plan to produce this hot air, the ballon must be insulated to maintain a cool city, the air that would flow up would be warmer then the city but not hotter then the outside air, if you let in heat to heat that air then via convection its going to add heat your city, your going to need to pump out more heat. The energy costs are going to be great.

I know very well all eco-friendly technologies, that is what I would do (analizing) for living in shorted.

But it has nothing to do with the thing that we are talking about. Why are you mention this???

You want to know how much energy you and pull back out of a heat gradient in a column of air, that how much.

You're not understanding...

No I’m not, I don't see how you can claim the costs of maintaining your city at a cool temperature are going to be light.

Extra weight of insulators?? heh.. The main characteristic of any good insulator is "light", if they are not light, they are not good insulators.

Balloon fabric is pretty dam light, adding more layers to it is going to make it not as light, it is extra weight.

Heat pumps? Power plants? Radiators? You need to put some effort to understand what I am saying before try to search a flaw.

The AC it does not need to be so big, is just to compensate some heat mix that would start to happens in weaks or months

Weeks or months? Where are you coming up with that? The AC has to fight the heat of the city, it has fight heating for convection inside the balloon, it has to fight heating from outside!

??? Plants does not need UV to growth. In fact they are better without UV. They use just visible light.

I never said UV, where are you getting UV?

Is all in the graphic... Is not so difficult to understand...

The graphic does not make physical sense.

I'll make it simple for you, forget for one second about all the insulation and the different IR layers, AC, etc.

Now you have two environments, "outside" and the "city envelope". All the radiation and heat by convection and conductivity equals temperatures. Now imagine that you are in a small room in this city, you just cold down the room. To do this you need to counter all energy that the city is receiving?? No.

Why? becouse it only matters the heat received and expelled by the system, they need to be equal or temperature rise, or down (there is not violating in this process); but when we talk about equal temperatures between enviroments we are talking of average temperature!, you can have many different temperatures inside the envelope and you would not violate any law meanwhile your average temperature is the same that outside.

No this makes no sense, energy must be spent to maintain any temperature difference anywhere, averages does negate that. I'll make it simple for you: you must cool the city, to do that you need to add weight and complexity in insulators, heat pumps, radiators and power plants, there is no way around this, period.

Now you can have a lot of insulators and reflect almost all heat, you just receive 1kw of heat in the whole envelope,

1 kW, that is impossible, you have envelope that is has a surface area of kilometers holding out a temperature difference of 55 K, there no way could have only 1 kW of heat entering! I've shown through conduction alone the heat entering would be astronomical, you would need THICK insulation to hold that back or worse a vaccum-dewar.

if you manage to radiate the same 1kw of energy to outside, you have equilibrium.

Impossible! That would violate physics, you must PUMP out all heat that enters, you can't radiate it back out because the radiation you let in will be greater.

Doing this you can have any temperature you want. Or maybe you expend extra energy extracted from outside, and you keep cooling the inside until you reach almost 0 absolute. (you are not violating any law).

Again to maintain any temperature below ambient will cost energy, let alone absolute zero.

So returning to the stratification idea. Here if your average temperature inside is equal to outside, you would exchange the same energy that you receive.

No you would not. You need to add the cost of energy from heat pumps, and the heat from that energy. Surrounding your self with air that the same temperature as the outside does not magically make those energy costs disappear, now you need to keep cool from the air you surround your self from.

But you can take advantage that hot air rise and cold air downs. Encouraging this process with vent methods and some insulating in the right places, you can have an area where your temperature is low and another area where the temperature is higher to compensate.

Is clear enoght?

yes, it clear where the flaw your logic is: average temperatures does not allow you to violate thermaldynamics: to maintain any temperate difference anywhere requires energy.

You know how many times you said in this mail the words: weight, cost, lots, violating; between others? Try to be more positive, problems are easy to solve

yes it can be easily solved: float higher! All those problems disappear if we do that, but your obsessed with floating lower for some reason. Again I point out more gas costs a lot less then all the complexity your adding.

Using the same "parachute" that I mention to produce drag, then energy from the parachute and proppelers. Is the thing that you need to maintain latitude in conjunction with rudder, without expend electricity (also if you are in the equator you dont need it).

How? In the same way that kite surfing.

Assuming Venus’s air currents are navigable.

No, I said that venus low orbit is easier to reach due to 0,9 g and venus diameter, and you said that only is a 10% of reduction due to gravity.

Now I said again, is not only for gravity, is also for diamenter, and you have a 0,9 of earth diamenter.

Both parameters matter in equal proportions.

If we have an hypothetical planet of 3 meters of diamenter with a surfuce gravity of 9,8m/s2, then we can enter in orbit with just a jump.

And I say again that does not add up to much savings. Venus at a diameter 95% that of earths, and a gravity 91% that of Earths, if we assume equal proportions then that means an orbital velocity 86% that of Earths or 7-8 km/s!

You need to go outside to assemble things, maintenance, fly to other cities, go to work to other stations, it can be a scientific station, or the rocket launcher station... or maybe just becouse you wanna go out and fly over there.

A) you could have robots do that.

going outside at 55ºC into acid mist is not going to be something people want to do for fun.

C) if you want to fly we could build habitats in lunar lava caves or asteroids and you can strap on wings and fly. Frankly hang on to a balloon in the middle of complete blank whiteness does not sound very fun.

Completely white blankness??? You are almost in the bottom of the clouds. I would said that days are almost as shiny like a sunny day at earth.

yes complete white blankness, yes very bright, complete white blankness, no you would not see the surface, in fact as your get lower in the clouds whiteness would give way to yellow, followed by red and then you would see the surface below, at the altitude you describe the sky might in fact have a **** color or perhaps an unappetizing orange, perhaps darker below then above. Seeing fluffy white clouds and blue sky is unlikely.

[AngelLestat]

You have no idea what are you talking about. You need to read about thermodynamics. Try to find someone else to read this and see if is agree with you.

I've provided a link and quote, what more do you want?

In your head the sun tower is equal to this?? it works in the atmosphere! No stratification there. You have strong winds, vertical winds, heat rising from the heated surfuce, etc. In fact temperature decrease over altitude here. So if you use this example to point that you can not have a good delta T stratification, then is the most silly thing that I read from you.

And how much energy is required to maintain the stratification? A hot air balloon burns a lot a fuel for example. I'm really baffled at how you plan to produce this hot air, the ballon must be insulated to maintain a cool city, the air that would flow up would be warmer then the city but not hotter then the outside air, if you let in heat to heat that air then via convection its going to add heat your city, your going to need to pump out more heat. The energy costs are going to be great.

Again! a hot air ballon has nothing to do with a stratification method. Besides the ballon it does not spend energy to maintain the stratification, is something that is produced naturally!!! In fact for a ballon would be better if they dont have a hard stratification inside, becouse the max operating temperature to work with nylon is 100 C. So they want to have 100 C in the whole ballon, not just in the top part. In building design or other cases, people try to fight against stratification becouse is something that comes naturally.

You need to see the graph again becouse you are not understanding. The heat rise by the sides and carry extra heat that enters between the 2 envelope layers (there is no mix). Well, I would not bother to explain a picture, is all there, if you dont understand with that image, then you never will.

You want to know how much energy you and pull back out of a heat gradient in a column of air, that how much.

Where I mention to took energy of the gradient I was saying from the top layer 100C to the external atmosphere 66C.

If I use the internal gradient then I am just dissolving that gradient. But if I do I would have more power that this tower in just 200 mts, but the process woult not be the same.

No I’m not, I don't see how you can claim the costs of maintaining your city at a cool temperature are going to be light.

Becouse you only need to take into account the human heat, some other other city heat sources and a "very low" conductive heat comming from the layer above (and remember that convection heat transfer is working for you here), but all the main source heats of the city would be funnel to the air current that is between the 2 envelopes. That would carry up heat, reinforcing stratification.

Balloon fabric is pretty dam light, adding more layers to it is going to make it not as light, it is extra weight.

So aerogel is heavy now??? Come on, I want you to calculate how much weight you adding with 1cm or 2cm aerogel layer to insulate 1/3 of the envelope. I would tell you, that weight less than a person.

Weeks or months? Where are you coming up with that? The AC has to fight the heat of the city, it has fight heating for convection inside the balloon, it has to fight heating from outside!

With common sense, you need to use it some day. I dont understand what are you talking about. I already told you what heat sources the AC needs to couter.

I never said UV, where are you getting UV?

So then you are saying infrared... Plants live with visible light, some plants use thermal radiation just to know when to bloom. That is it. You can use an infrared light only 1 day over year to achieve that.

No this makes no sense, energy must be spent to maintain any temperature difference anywhere, averages does negate that. I'll make it simple for you: you must cool the city, to do that you need to add weight and complexity in insulators, heat pumps, radiators and power plants, there is no way around this, period.

So, you are saying that hot air does not rise?? Is that what are you saying?? So I need to use energy to make the hot air rise??

Lessen to you...

1 kW, that is impossible, you have envelope that is has a surface area of kilometers holding out a temperature difference of 55 K, there no way could have only 1 kW of heat entering! I've shown through conduction alone the heat entering would be astronomical, you would need THICK insulation to hold that back or worse a vaccum-dewar.

You dont understand the difference between theorical examples and real? That was just to allow you understand the laws of thermodynamics... hard work!

Impossible! That would violate physics, you must PUMP out all heat that enters, you can't radiate it back out because the radiation you let in will be greater.

more no sense. Read about how solar thermal collectors made of vaccum tubes with heat pipe techonology works. Then tell me if is possible or not to transfer energy to an high temperature enviroment than yours.

yes, it clear where the flaw your logic is: average temperatures does not allow you to violate thermaldynamics: to maintain any temperate difference anywhere requires energy.

Is not, becouse stratification is the base state of equilibrium of any fluid. In any case, you need to spend energy to break that equilibrium. Or what? a boat needs to spend energy to float??

yes it can be easily solved: float higher! All those problems disappear if we do that, but your obsessed with floating lower for some reason. Again I point out more gas costs a lot less then all the complexity your adding.

Yes, that is another possibility, and I support this just becouse you can go outside. But I am not so convinced about the cost.

Lets make numbers, a small outpost vs a city to see what method is most cost effective in each case.

Adjust numbers to make easy calculations.

Envelope mass: 100g/m2

Air mass: 1kg/m3

Diameter: 20mts

Surfuce: 1250 m2

Volume: 4190 m3

Air mass: 4190 kg

Envelope mass: 125kg

Mass ratio: 33-1

Diameter: 200meters

Surfuce: 125000 m2

Volume: 4190000 m3

Air mass: 4190 Tons

Envelope mass: 12 Tons

Mass ratio: 330-1

How you can see, it reach a point where its more cost efficient spend more in insulation mass than in m3 of air.

Assuming Venus’s air currents are navigable.

Until now almost all evidence that we have points that they are. We need to know more. But there is not reason to be negative yet.

A thick atmosphere regulates the heat differences more smoothly than a thin atmosphere. So only knowing that we can said that it will be more easy than float in our atmosphere.

And I say again that does not add up to much savings. Venus at a diameter 95% that of earths, and a gravity 91% that of Earths, if we assume equal proportions then that means an orbital velocity 86% that of Earths or 7-8 km/s!

86 is less than 90. Each km/s counts.

A) you could have robots do that.

going outside at 55ºC into acid mist is not going to be something people want to do for fun.

C) if you want to fly we could build habitats in lunar lava caves or asteroids and you can strap on wings and fly. Frankly hang on to a balloon in the middle of complete blank whiteness does not sound very fun.

A) In my opinion it will take a long time to robots become so agile and dinamic like an human. Also, you would have humans anyway, why produce a robot when you can do the same job with people.

with appropriate clothing there is nothing to be worry, a lot of jobs here at earth are a lot worst.

C) that is your opinion about the sky, I never hear that from nobody else. Evidence points the contrary.

yes complete white blankness, yes very bright, complete white blankness, no you would not see the surface, in fact as your get lower in the clouds whiteness would give way to yellow, followed by red and then you would see the surface below, at the altitude you describe the sky might in fact have a **** color or perhaps an unappetizing orange, perhaps darker below then above. Seeing fluffy white clouds and blue sky is unlikely.

The doctor of the link that I sent you disagree with you with the view at that height. Maybe the next probe would take a picture so you can see.

Besides, I was talking about bright, not colors..

Edited March 11, 2014 by AngelLestat

[Vanamonde]

Guys, we already had to close one thread like this because the arguments were turning nasty. We'd rather not have to do it again. Do not resort to insults, no matter how strongly you feel about the subject, and remember to talk about the subject and not each other, or we will have to lock this thread as well.

[sal_vager]

I second Vanamondes message here, the Science labs are not for bickering, argument or personal attacks, questioning others intelligence or ability to learn does not belong on these forums.

Many of you are happy to help other players when they ask in the Gameplay Questions section, I ask that you apply that attitude here as well.

[Dodgey]

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.

[AngelLestat]

Ok dodgey I would answer you later. However the area that we need to insulate is just 1/3 of the envelope, the bottom part.

First I want quote some words of Dr. Robert Walker about this topic and how these kind of discusions helps and contribute with science.

Is what its call Science 2.0

So, Venus cloud colonies have had nothing like the attention given to colonizing Mars. But there are a fair number of people now discussing it in forums on-line.

It is a great example I think of Science 2.0 in action. In Science 1.0 then the science is done via peer reviewed publications - the researchers may discuss it before hand of course -- but the final result is a publication in a peer reviewed journal - and that is when others start to cite your results and refer to them and so on.

In Science 2.0 then much of the working out of ideas happen collaboratively over the web in forums and discussions and so on. You will get still peer reviewed papers, they have their place and are important, but are not the only way the research is done.

This also helps to make it a way of doing science that permits collaboration with amateurs as well, who often come up with innovative ideas that no-one else thought of - and sharing of ideas at an early stage - and making mistakes also. You no longer have the idea that everything has to be totally worked out and polished before you share your ideas with others.

So, we have to be aware of this when discussing topics such as Venus cloud colonies. There may well be hidden issues that we don't notice or don't give enough prominence to in our thinking. The best solution, mentioned on the show, is to surround yourself with people who are cleverer than yourself, who can correct your errors. But not to assume that they will always get things right just because they know so much, as we see from the NASA experience that clever people also are prone to magical thinking.

When done well, then the science 2.0 approach can help us to avoid magical thinking. But if it turns into a flame war with the various participants sticking to their views, and not listening to each other, it can foster magical thinking. So far at least, discussions on Venus cloud colonies don't seem to have got polarized, in the way that sometimes happens. So long as participants listen to each other, and do our best to ground the ideas in the harsh engineering realities whenever we can - perhaps we can avoid the traps of magical thinking.

What I want to said, is that we have something good here, of course there is a behavior that I need to correct the same as Rubisco, we need to read more to not end in a flame war like the doctor explain. After all, where there is not more to talk, the tread would die alone.

[RuBisCO]

You have no idea what are you talking about. You need to read about thermodynamics. Try to find someone else to read this and see if is agree with you.

By all means get a second opinion!

In your head the sun tower is equal to this?? it works in the atmosphere! No stratification there. You have strong winds, vertical winds, heat rising from the heated surfuce, etc. In fact temperature decrease over altitude here.

The principle is the same inside the cloud city your describe, only inverted, but it most certainly at those sizes will be internal convection and winds.

So if you use this example to point that you can not have a good delta T stratification, then is the most silly thing that I read from you.

I'm not sure we are arguing about the same thing, I'm not speaking of temperature difference, I'm speaking of how much power (energy) you can get out of such a system.

Again! a hot air ballon has nothing to do with a stratification method. Besides the ballon it does not spend energy to maintain the stratification, is something that is produced naturally!!!

How? The city magically stays cool? Sure the hot air will rise, but that not the problem, the problem is how do you expect to keep the city cool with the outside so hot and with hot air circulating all around it?

In fact for a ballon would be better if they dont have a hard stratification inside, becouse the max operating temperature to work with nylon is 100 C.

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?

You need to see the graph again becouse you are not understanding nothing. The heat rise by the sides carry extra heat that enters between the 2 envelope layers (there is no mix). Well, I would not bother to explain a picture, is all there, if you dont understand with that image, then you never will.

Your not understanding what I'm saying, how much more will having said layers and vents and heat pumps, etc, etc cost? Is it really worth it not to simply fly higher and not need any of that?

Becouse you only need to take into account the human heat, and some process heats with a "very low" conductive heat comming from the layer above (and remember that convection heat transfer is working for you here), almost all process heat you would funnel to the air current that is between the 2 envelopes. That would carry up heat reinforcing stratification.

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

So aerogel is heavy now??? Come on, I want you to calculate how much weight you adding with 1cm or 2cm aerogel layer to insulate 1/3 of the envelope. I would tell you, that weight less than a person.

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.

With common sense, you need to use it some day. I dont understand what are you talking about. I already told you what heat sources the AC needs to couter.

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.

So then you are saying infrared... Plants live with visible light, some plants use thermal radiation just to know when to bloom. That is it. You can use an infrared light only 1 day over year to achieve that.

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.

So, you are saying that hot air does not rise?? Is that what are you saying?? So I need to use energy to make the hot air rise??

No I'm not saying such a thing, I'm saying you need to spend energy to keep the city cool.

You dont understand the difference between theorical examples and real? That was just to allow you understand the laws of thermodynamics... hard work!

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.

more no sense. Read about how solar thermal collectors made of vaccum tubes with heat pipe techonology works. Then tell me if is possible or not to transfer energy to an high temperature enviroment than yours.

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.

Is not, becouse stratification is the base state of equilibrium of any fluid. In any case, you need to spend energy to break that equilibrium. Or what? a boat needs to spend energy to float??

No the equilibrium state would be no gradient and no heat difference, stratification is a result of temperatures being out of equilibrium.

Yes, that is another possibility, and I support this just becouse you can go outside. But I am not so convinced about the cost.

Lets make numbers, a small outpost vs a city to see what method is most cost effective in each case.

Adjust numbers to make easy calculations.

Envelope mass: 100g/m2

Air mass: 1kg/m3

Diameter: 20mts

Surfuce: 1250 m2

Volume: 4190 m3

Air mass: 4190 kg

Envelope mass: 125kg

Mass ratio: 33-1

Diameter: 200meters

Surfuce: 125000 m2

Volume: 4190000 m3

Air mass: 4190 Tons

Envelope mass: 12 Tons

Mass ratio: 330-1

How you can see, it reach a point where its more cost efficient spend more in insulation mass than in m3 of air.

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.

Until now almost all evidence that we have points that they are. We need to know more. But there is not reason to be negative yet.

A thick atmosphere regulates the heat differences more smoothly than a thin atmosphere. So only knowing that we can said that it will be more easy than float in our atmosphere.

What evidence?

86 is less than 90. Each km/s counts.

Nitpicking, heck we have yet to talk about altitude, what is the minium orbital altitude of venus? I would bet with its atmosphere that altitude is much higher than earth, and thus the orbital energy is higher. ~90% may in fact be a underestimate.

A) In my opinion it will take a long time to robots become so agile and dinamic like an human. Also, you would have humans anyway, why produce a robot when you can do the same job with people.

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.

with appropriate clothing there is nothing to be worry, a lot of jobs here at earth are a lot worst.

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.

C) that is your opinion about the sky, I never hear that from nobody else. Evidence points the contrary.

What evidence? The venara and pioneer probes clearly show alot of haze, show a shifting into the red the deeper into the cloud layers.

The doctor of the link that I sent you disagree with you with the view at that height. Maybe the next probe would take a picture so you can see.

Besides, I was talking about bright, not colors..

That just an artist interpretation, of course he's not going to paint a city afloat in white blankness or worse in yellow or red haze.

[sal_vager]

The Science labs are not for bickering, argument or personal attacks, questioning others intelligence or ability to learn does not belong on these forums.

RuBisCo, again I have to ask that people watch their conduct here, it is confrontational and unwarranted.

[RuBisCO]

Well I apologies I don't mean to be confrontational, I am mearly disagree with tiny part of AngelLestat premise, the nominal altitude of his "cloud city", if Angel' wants to say I don't understand her scheme or thermaldynamics, we can leave it at that then, clearly on this point not further discussion can be made.