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I think a Titan City, once you got there, would be easier to build, than a city on Mars. After all on Titan you can inflate giant domes by pressurizing the interior slightly more that the exterior so the dome can hold its shape. The fabric of the dome would be a sort of bubble wrap, I would suggest helium bubbles would make the best insulator, because helium would remain a gas even at Titan's low temperature. I would suggest that part of Titan consists of dirt and rock, we can fill the interior with dirt and rock to sit on top of the helium bubble wrap, heat the interior to some pleasant temperature with either a fission or a fusion reactor. If we assume a city that is 8 miles in radius or 12.8 km in radius, assuming we illuminate it with 1380 watts per meter squared. We have 514718540.36 square meters of land and we'll need to generate 710,312 megawatts to illuminate the interior to Earth daylight levels.
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I'm not sure why you have suddenly put a big city on Titan! Presumably we will land a few people there first and they will figure out how to keep themselves and their equipment from being damaged by the cold. That will cost billions and many years to figure out, all by itself.
I have thought about Titan colonies a bit and I think you are best off melting big underground caverns, for two reasons:
1. A lot of plastics will dissolve in methane/ethane rain.
2. Underground is a far more benign environment. For all we know, there may occasionally be very powerful winds on the surface. You don't want your dome blown away. The ice crust, also, will provide insulation; you'll need less "bubble wrap." If you melt a soaring cavern--let's say 100 meters high--and the crust of Titan is 1% meteorite (carbonaceous chondrite and stony meteorite, mostly), then melting the cavern will generate a meter of proto-soil. Add to that roasted tholin (rather like the tierra nigra of the Amazon basin) and you have your soil. You will need in insulation layer under it and insulation all the way around your bubble of Earth, but I think that's easier to do underground.
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Titan's mean surface temperature is about -170 C. The atmosphere is thick and cloudy and the diurnal cycle is long, so I would expect the wind speeds to generally be low except for near the methane/ethane lakes. -170 C is about 190 C below a comfortable room temperature.
Yakutsk, Russia has temperatures that regularly fall to -40 C at night during the winter. This is about 60 C below a comfortable room temperature. Yakutsk is the coldest city in the world, and is actually significantly colder than McMurdo in Antarctica.
My point in mentioning all this is that Titan is about 3 times colder than the coldest city on Earth at night in the dead of winter. Comparatively, the difference in atmospheric pressure (I would expect colonies to operate at ambient pressure, actually) and composition is virtually meaningless. An airlock wouldn't even be strictly necessary for people to enter and exit if the temperature were higher, as long as they entered and left quickly.
The ideal location for a colony would be somewhere with generally low winds, for example in the lee of a mountain or right on the equator, where trade winds in each direction tend to cancel each other out. The equator is also good for space-launch.
Because of the low gravity, convection currents won't be much of a problem. For this reason, and to prevent the ices below from ever melting, the city will be lifted several meters above the ground on pylons. For heat retention, the city will probably be cylindrical, or made from a collection of connected spheres. The inside will probably be lit electrically and have lots of green space. Think something like the LowLine. Windows to the outside won't be very valuable but will be very costly, as low light levels make the surface of Titan look quite bleak compared to Earth.
The city should take advantage of the low gravity by being an extremely 3-dimensional space.
As a side note, it would be absolutely nuts to light the inside of anything at anywhere near 1400 W/m^2. Even at high noon in the middle of a desert on Earth with the Sun directly overhead you don't get more than about 1000 W/m^2. Of this, about 55% falls in the visible spectrum. My room (about 10 square meters) is lit quite well by 4 13-watt fluorescent bulbs. A typical fluorescent bulb is about 25% efficient, so that means that my room is lit by about 1.3 W/m^2 of visible light. I know that seems low, but the human eye is actually very adaptable to low light levels. As a basic sanity check, it's plenty light in New York, even in mid-winter, as long as the Sun is out. New York is at 42 degrees North Latitude, so at mid-winter the Sun is just 25 degrees above the horizon at high noon. This means that (ignoring atmospheric effects) a horizontal surface receives about 575 W/m^2 of any kind of light. Given only 55% of this is visible, that's more like 315 W/m^2. If atmospheric effects subtract an additional 30%, we're looking at a bit over 200 W/m^2. I think it would be desirable to simulate varied environments with different coloring schemes, different construction materials and amounts of foliage, and different light levels.
-Josh
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There is a lot to learn about the surface and subsurface conditions of Titan. What is the surface composition, and will it melt from beneath our feet from the construction process and heat of habitation? What materials are readily available?
Further architectural questions are raised by the .15g. To what degree does that need to be overcome to enable sustained human life and its supporting agriculture? And how would you do it?
Assuming those issues are settled, the basic architecture need not vary a great deal from anyplace else. Depending on the restrictions that the extreme temperatures place on the design, you can have a large, flat, circular concrete or concrete analog slab is placed on the surface, or you lift the entire thing on pylons and have a bowl shaped "basement". On top, geodesic glass dome is built on it, with the interior heated and pressured with a shirt sleeve atmosphere. A dome provides the best defense from winds, and the latter produces an ellipsoid, with twice the volume to work with. The overall structure can span multiple kilometers, with hundreds of meters of "airspace" to play with.
Within the top half, a lower profile inflatable canvas dome is inflated, and the interior is spray coated with an insulating urethane foam. Within that, a layer of reinforced shotcrete is applied to both the interior and exterior of the dome, producing an all but impervious air tight structure that is equally capable of supporting activities on its outer surface. This surface, and the dome above it, constitutes a controlled greenhouse, where a park can be placed. There is no real purpose in using it for agriculture, so it will mainly be a recreational space. It must be assumed that the glass dome will be punctured from time to time, and since agriculture space will have to be all controlled anyway, it might as well be under the concrete.
Within the concrete dome, you can build anything you want in it safety. I suspect you will want to have some sort augmented gravity centrifuge torus system. Entire modular neighborhoods can be built within these tori, which in turn, can be stacked into high rise structures, providing augmented gravity for home, office, and agricultural space. Other endeavors that benefit from the local gravity with have it. Those not satisfied with the ultra high definition camera views of the natural surface can go topside and frolic in the greenhouse park, relativity certain that if something happened to it, they could get below in time.
Last edited by Excelsior (2016-01-18 21:56:30)
The Former Commodore
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I think colonisation of Titan raises some big challenges that you wouldn’t face on Mars, but in the long term maybe some opportunities as well.
On the plus side, the high atmospheric pressure makes it relatively easy to create large volumes with breathable atmosphere, provided you can heat them. The low temperature also allows the use of ice as a structural material without danger of melting. The presence of large pools of liquid methane on the surface and a dense cold atmosphere also provides an excellent heat sink. It should be possible to build extremely efficient, compact and economical nuclear reactors, and you would certainly need them. It should also be possible to build huge volumetric habitats without having to worry much about keeping them cool, as evaporative cooling at 90K provides a heat sink par excellence. Dumping heat could ultimately be a size limiting problem on Mars. Aerodynamic flight would be easy compared to Mars and would probably be the main means of travel. Space radiation is not an issue, but keeping heat fluxes manageable may require adopting similarly restrictive solutions.
Many of the same things would make living on Titan extremely difficult.
The air density on Titan at 90K and 1.5bar would be something like 10 times greater than on Earth. And the temperature difference between your body and the air would be 2.5 greater than that in Antarctica. You also have methane drizzle to add evaporative cooling to the mix. Collectively that means that a solid object at human body temperature would lose heat at a rate 30 times greater than Antarctica (although lighter wind speeds may help a little). EVA would be extremely difficult. Suits would need to be aerogel lined and may need an RTG to protect the user from hypothermia.
Natural sunlight would not be useful for agriculture – you would need to provide artificial light. But a normal greenhouse would lose too much heat anyway. Habitats would need thick walls or would need to be lined with insulation to keep heat losses manageable.
Finding silicates and metals might be difficult on a world where the surface crust is dominated by water ice. Ice would serve many of the functions that masonry does on Earth.
Fire might be less of a problem than on Mars or Earth. With an atmospheric pressure of 1.5bar and an oxygen partial pressure of 0.2bar, it would be very difficult for fire to propagate.
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One of the cool things about Titan is that you can build a space elevator pretty easily by suspending it from Titan's L1 point with Saturn. I calculate an effective breaking length in constant 1 g of about 330 km (Can supply my code), which is well within the limits of something like Carbon Fiber. I don't know what will be bringing people to the Saturn system in the first place, but easy transportation between worlds is a good reason to stick around.
-Josh
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One of the cool things about Titan is that you can build a space elevator pretty easily by suspending it from Titan's L1 point with Saturn. I calculate an effective breaking length in constant 1 g of about 330 km (Can supply my code), which is well within the limits of something like Carbon Fiber. I don't know what will be bringing people to the Saturn system in the first place, but easy transportation between worlds is a good reason to stick around.
That would solve the material problems.
The Former Commodore
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Sure, but what then does Saturn have that other places don't?
I was thinking of importing materials to the surface from easier to manage sources in the Saturnian system. Titan's atmosphere might make it safer to inhabit than the other surfaces there, but construction materials from the smaller moons will be readily available long before we find them on Titan.
Overall, floating habitats in the atmospheres of the outer gas giants themselves may be more viable than the "cryomoons".
The Former Commodore
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Something like this? -
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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JoshNH4H wrote:Sure, but what then does Saturn have that other places don't?
I was thinking of importing materials to the surface from easier to manage sources in the Saturnian system. Titan's atmosphere might make it safer to inhabit than the other surfaces there, but construction materials from the smaller moons will be readily available long before we find them on Titan.
Overall, floating habitats in the atmospheres of the outer gas giants themselves may be more viable than the "cryomoons".
I would imagine that even if stony solids are on the scarce side that they'll be easier to find on the surface of Titan - perhaps near cryovolcanoes, much as certain ores on Earth are often volcanic in nature - than to import from elsewhere in the system. I assume that stony materials would have to be obtained from the dusty ice in the rings, or something like that, and then imported to Titan.
It's much easier to do thermal insulation than it is to float a city in an atmosphere composed primarily of Hydrogen and Helium to begin with. Especially given that Saturn's atmosphere is still quite cold. Assuming a temperature of 200 K and a composition that is 25% Helium to 75% Hydrogen, it would be necessary to have 34 cubic meters of pure Hydrogen gas per kilo of weight to be lifted. Let's say an average-sized person in a spacesuit masses 100 kilos; He or she would need 3,400 cubic meters of gas to lift that weight. This corresponds to a sphere 18 m (59 ft) in diameter, and of course I'm neglecting the mass of the balloon itself, which at this scale is quite significant. Lifting a 1-tonne car would require a balloon with a diameter of about 40 m (again assuming the balloon itself is massless). The point being that a city would require some truly incredibly massive balloons.
-Josh
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I think colonisation of Titan raises some big challenges that you wouldn’t face on Mars, but in the long term maybe some opportunities as well.
On the plus side, the high atmospheric pressure makes it relatively easy to create large volumes with breathable atmosphere, provided you can heat them. The low temperature also allows the use of ice as a structural material without danger of melting. The presence of large pools of liquid methane on the surface and a dense cold atmosphere also provides an excellent heat sink. It should be possible to build extremely efficient, compact and economical nuclear reactors, and you would certainly need them. It should also be possible to build huge volumetric habitats without having to worry much about keeping them cool, as evaporative cooling at 90K provides a heat sink par excellence. Dumping heat could ultimately be a size limiting problem on Mars. Aerodynamic flight would be easy compared to Mars and would probably be the main means of travel. Space radiation is not an issue, but keeping heat fluxes manageable may require adopting similarly restrictive solutions.
Many of the same things would make living on Titan extremely difficult.
The air density on Titan at 90K and 1.5bar would be something like 10 times greater than on Earth. And the temperature difference between your body and the air would be 2.5 greater than that in Antarctica. You also have methane drizzle to add evaporative cooling to the mix. Collectively that means that a solid object at human body temperature would lose heat at a rate 30 times greater than Antarctica (although lighter wind speeds may help a little). EVA would be extremely difficult. Suits would need to be aerogel lined and may need an RTG to protect the user from hypothermia.
Natural sunlight would not be useful for agriculture – you would need to provide artificial light. But a normal greenhouse would lose too much heat anyway. Habitats would need thick walls or would need to be lined with insulation to keep heat losses manageable.
Finding silicates and metals might be difficult on a world where the surface crust is dominated by water ice. Ice would serve many of the functions that masonry does on Earth.
Fire might be less of a problem than on Mars or Earth. With an atmospheric pressure of 1.5bar and an oxygen partial pressure of 0.2bar, it would be very difficult for fire to propagate.
Liquid oxygen could exist as a stable substance on Titan, could that be used as a fuel? Arthur C Clarke suggested that it could be in his novel Imperial Earth. Now the question is, are their enough flammable's in Titan's atmosphere, such as methane vapor for instance? I think air travel would be a excellent way to get around on Titan, thus you could have a jet engine fueled by liquid oxygen, mixing in native flammables in the atmosphere to provide propulsion.
On the inside of the dome, at 0.15g you could jump from the 6th or 7th floor of a building and land on your feet, and walk away with no injuries. I think with an atmosphere inside greater that 1.5 bar (to support the weight of the dome, the terminal velocity would be lower. There might have to be some regulations about people jumping from the roofs of buildings to land on the streets below, the temptation might prove too great for some juveniles.
I think you could have a double paned window, glass on one side, ice on the other, and a light gas such as hydrogen or helium in between. I think water ice would make a great substitute for glass in many cases.
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Excelsior wrote:JoshNH4H wrote:Sure, but what then does Saturn have that other places don't?
I was thinking of importing materials to the surface from easier to manage sources in the Saturnian system. Titan's atmosphere might make it safer to inhabit than the other surfaces there, but construction materials from the smaller moons will be readily available long before we find them on Titan.
Overall, floating habitats in the atmospheres of the outer gas giants themselves may be more viable than the "cryomoons".
I would imagine that even if stony solids are on the scarce side that they'll be easier to find on the surface of Titan - perhaps near cryovolcanoes, much as certain ores on Earth are often volcanic in nature - than to import from elsewhere in the system. I assume that stony materials would have to be obtained from the dusty ice in the rings, or something like that, and then imported to Titan.
On the positive side, Titan has an active geology similar to Earth, its surface is not very ancient, it has mountains, and that means some geologic process has created those mountains, and with that, its possible to have stony ores, much as we have ores for metals on Earth. One would mine for veins of stone between layers of ice, that stone, when crushed could be made into soil, one could also make concrete and other building materials inside the dome, and if that's not enough, it is much easier to get into space from Titan due to its low escape velocity. Maybe an oxygen ramjet could accomplish this by burning flammables in the atmosphere using an on board supply of stored liquid oxygen.
It's much easier to do thermal insulation than it is to float a city in an atmosphere composed primarily of Hydrogen and Helium to begin with. Especially given that Saturn's atmosphere is still quite cold. Assuming a temperature of 200 K and a composition that is 25% Helium to 75% Hydrogen, it would be necessary to have 34 cubic meters of pure Hydrogen gas per kilo of weight to be lifted. Let's say an average-sized person in a spacesuit masses 100 kilos; He or she would need 3,400 cubic meters of gas to lift that weight. This corresponds to a sphere 18 m (59 ft) in diameter, and of course I'm neglecting the mass of the balloon itself, which at this scale is quite significant. Lifting a 1-tonne car would require a balloon with a diameter of about 40 m (again assuming the balloon itself is massless). The point being that a city would require some truly incredibly massive balloons.
Since Saturn's atmosphere is made up of hydrogen, any hydrogen balloon would have to be heated to maintain a density less that the surrounding atmosphere to generate lift. Saturn also lacks for building materials within its atmosphere.
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One of the cool things about Titan is that you can build a space elevator pretty easily by suspending it from Titan's L1 point with Saturn. I calculate an effective breaking length in constant 1 g of about 330 km (Can supply my code), which is well within the limits of something like Carbon Fiber. I don't know what will be bringing people to the Saturn system in the first place, but easy transportation between worlds is a good reason to stick around.
The simplest reason is that Titan is a place to live, it has all the elements that Earth does to support life, all you need is a constant energy input, I think many of the hydrogen compounds can contain deuterium, which can be fused in a fusion reactor, the methane and ethane in the atmosphere could fuel a fusion reactor, the output of the fusion reactor could go towards the manufacture of liquid oxygen, which would be a more portable "fuel" source for vehicles, such as oxygen jets and ramjets. Oxygen powered heaters would also be pretty handy where one doesn't have the space for a full fledged fusion reactor.
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One can live on Titan, but there's no shortage of places to live in Space. Or, for that matter, on Earth. People generally live where there is some economic reason for them to live, and often this is tied - at least somewhat - to resources. Why should I move to Titan when there's plenty of room on the Moon, for example?
-Josh
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One can live on Titan, but there's no shortage of places to live in Space. Or, for that matter, on Earth. People generally live where there is some economic reason for them to live, and often this is tied - at least somewhat - to resources. Why should I move to Titan when there's plenty of room on the Moon, for example?
How about, what is the economic reason for us living on Earth?
There is no economic reason for us to live on Earth, we just are here! We make do with the resources we find on Earth. The truth is every element we can find on Earth can also be found on Titan. We can create environments on Titan, that are very Earthlike except for gravity, unlike say the Moon, we are not limited by material on Titan, there are plenty of volatiles here, just not heat or light, but we can generate that. It is hard to project what the economy would be like, by the time we are ready to inhabit Titan, but we can create breathable and livable space on Titan with the right sort of technology.
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"We're here now" actually is a pretty decent economic argument for staying here. Over the course of history we've sunk quadrillions of dollars into creating assets that would be quite expensive to move. Because of the presently high cost of getting anywhere from Earth, even if there were a second Earth elsewhere in the solar system the investment required for an equivalent asset (a home, let's say) would be higher. Therefore there would be no reason to build such a home unless it were somehow more valuable than one on Earth. Given that there is not a second Earth there is also the continuous, higher cost of supporting human life in a less friendly environment.
-Josh
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What percentage of a Saturn V rocket's mass do you suppose is converted into energy in order to transport astronauts toward the Moon? It is not even 1%! If you added up the masses of all the spent stages and all the fuel reaction products it is almost the same as the initial stack sitting on the launch pad, that only goes to show that we use very inefficient means of getting into space, and that there is much room for improvement in this technology.
That being said, I've been thinking of what would be required to build a similar 8 mile radius city on the Ocean Surface, and at the South Pole.
For an Ocean colony, eschewing natural islands, I would say you would create an artificial island, by building a dome underwater and inflating it with higher pressure water until it rises above the ocean surface, then you bury it under rock and dirt to make an artificial island, keeping it sealed so it doesn't sink.
For an Antarctic colony at the South Pole, you melt a hole in the glacier and pump out all the water till either you reach the bedrock or you make a deep enough crater in the ice for the construction of the city. You then dome the hole and pressurize, heat and illuminate what's inside, and you can build your city within.
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Dragonfly tunnel visions
https://www.spacedaily.com/reports/Drag … s_999.html
With its dense atmosphere and low gravity, Saturn's moon Titan is a great place to fly.
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For Mars_B4_Moon re #20
Thanks for finding and posting the link to the report on development and testing of Dragonfly!
And thanks for bringing back this topic, created by Tom Kalbus.
"With Dragonfly, we're turning science fiction into exploration fact," Hibbard said. "The mission is coming together piece by piece, and we're excited for every next step toward sending this revolutionary rotorcraft across the skies and surface of Titan."
At launch time, we might want to set up a topic just for Dragonfly, but for now, this is as good a place as any for news about the mission.
(th)
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