How to build a flying city

[searchingfortruth]

To live in a flying city would be truly amazing, but how would we make it fly, power it, and control it?

[Tres Juicy]

more importantly - why would we try?

[searchingfortruth]

Over population, platforms to launch spacecraft, weather stations, observatories, etc.

[Tres Juicy]

Something as big as a city would fall apart if you lifted it off the ground

[CaptainPanic]

Current technology to live high in the sky is called a skyscraper. The highest is over 800 m tall.

 

If you really want to float, I would propose to use zeppelin/airship technology. At least you're not constantly spending energy to stay up, because that is done by buoyancy. Anything else is ridiculously impractical. Still, becoming airborne is not gonna solve any of the problems you mention.

 

Overpopulation

If you want to solve "overpopulation", becoming airborne solves nothing unless you get into orbit. If you want to create housing by thinking upwards, regular apartment buildings do the job quite well. If you want to create more land to grow food, you might as well build a bridge (still stationary). With both a flying thing or a bridge, someone will be in your shadow.

 

Launch spacecraft

Altitude is not the bottleneck for launching spacecraft. It's velocity.

Launching from high up in the sky will save a spacecraft a miniscule amount of fuel - so little that it's totally not worth it.

The reason that some companies and NASA want to launch from an airplane is that they give it some initial velocity. Those 900 km/h make a difference. But I wouldn't want to live in a city with flies at 900 km/hm because it would make it quite impractical to go outside for some fresh air.

 

Weather stations and observatories

Why bring the whole city up with them? Why not build dedicated weather stations and observatories without the city? Coincidentally, that is exactly what is done already. Weather balloons report what's going on high up in the atmosphere, and Hubble/Kepler, as well as many observatories on mountains use the thinner atmosphere or complete lack of atmosphere to get a good picture.

 

Making a city fly is pointless. Sorry that I do not share you enthusiasm about it.

[Tres Juicy]

 

But I wouldn't want to live in a city with flies at 900 km/hm because it would make it quite impractical to go outside for some fresh air.

 

 

 

[InigoMontoya]

Granted, it's not something I've studied extensively but....

 

My understanding is that the advantage of current generation airborne space launch platforms has less to do with the 900 km/hr velocity boost and more to do with the ability to hit *ANY* orbit at *ANY* time. IE, "infinite" launch windows and minimal course corrections to hit an orbit.

[searchingfortruth]

Over Population

You can keep building up until you reach eye level with God, but eventually you will have to expand horizontally. Our over population will eventually lead to over exhaustion of our resources, which will lead to dramatic rationing of food, water, and air. If we had self sustaining cities in orbit we wouldn't have to worry about it. We would just build more cities and send them on their way.

 

Launching Spacecraft

You honestly can't tell me it would not be easier and cheaper to launch from an orbiting city than from the ground. On average it costs $450 Million per mission to launch from the ground. http://science.ksc.nasa.gov/pao/faq/faqanswers.htm

 

Weather Stations and Observatories

Weather stations and observatories in orbiting cities most likely would be common place. Not only would they be beneficial while in orbit, but once they left orbit to go to Io, mars, etc. they would be a necessity in studying other worlds and their surroundings.

 

Space Mining

Space mining is something we are going to have to do, the Earth just doesn't have enough resources to sustain us forever. Space mining would be ridiculously costly if every time we mined something we had to send it back to Earth to process just to send it back into space. If we had refineries and factories in space near the mining, long term costs would be a lot less.

 

 

Flying cities could be the first step to long term colonization of space. If we could build cities in orbit and they could sustain themselves for long periods of time then colonization of other places would be easier to comprehend and manage. For instance, Mars is a very nasty place with all of its dust storms. http://science.nasa.gov/science-news/science-at-nasa/2001/ast16jul_1/ Storms that would make exploration and colonization a real hassle, but if explorers and colonists were safely tucked into orbit storms wouldn't be a bother to them.

 

[Phi for All]

To live in a flying city would be truly amazing, but how would we make it fly, power it, and control it?

To start off, I would suggest mass-production of a standardized space module that could house a group unit, and be combined with other modules as needs increase. Get as many independent group units up in orbit as is cost-effective. The modules would allow groups to salvage old satellite debris to pay for expansion, and fix current satellites at a cheaper rate.

 

As they clear space debris, they can keep hooking up more modules until they are city-sized. I see this as a good, sustainable model for operation until the modular platforms are big enough to handle more serious lifting and flights to the asteroid belts.

 

 

 

 

If you're talking about a city that flies around in the atmosphere, I think it would always take too much power and offer only mobility. It's appealing for land-based tourism if you can plan on having a whole other city stop by for festival, but how does that benefit the Flying City folks? You could probably milk some invitations to all the major cities for a while, they throw you a party, you bring your city to theirs. Your city could technically deliver any goods it manufactured, but it couldn't be cost-effective.

[searchingfortruth]

Lol. A city that flew in the clouds would be amazing, but I am talking about orbital cities that could be used as bases and maybe even colonies throughout the solar system.

To start off, I would suggest mass-production of a standardized space module that could house a group unit, and be combined with other modules as needs increase. Get as many independent group units up in orbit as is cost-effective. The modules would allow groups to salvage old satellite debris to pay for expansion, and fix current satellites at a cheaper rate.

 

As they clear space debris, they can keep hooking up more modules until they are city-sized. I see this as a good, sustainable model for operation until the modular platforms are big enough to handle more serious lifting and flights to the asteroid belts.

 

 

 

 

If you're talking about a city that flies around in the atmosphere, I think it would always take too much power and offer only mobility. It's appealing for land-based tourism if you can plan on having a whole other city stop by for festival, but how does that benefit the Flying City folks? You could probably milk some invitations to all the major cities for a while, they throw you a party, you bring your city to theirs. Your city could technically deliver any goods it manufactured, but it couldn't be cost-effective.

[InigoMontoya]

Over Population

You can keep building up until you reach eye level with God, but eventually you will have to expand horizontally. Our over population will eventually lead to over exhaustion of our resources, which will lead to dramatic rationing of food, water, and air. If we had self sustaining cities in orbit we wouldn't have to worry about it. We would just build more cities and send them on their way.

And you're fooling yourself if you think space is the answer to over population.

 

Global population increase is roughly 1% per year. There are 7,000,000,000 people on Earth. That means that to simply maintain our current population we would have to launch 191,000 people PER DAY into space.

 

Every day.

 

Not gonna happen.

 

Space may be the answer to a lot of problems, but that ain't one of them.

 

Launching Spacecraft

You honestly can't tell me it would not be easier and cheaper to launch from an orbiting city than from the ground. On average it costs $450 Million per mission to launch from the ground. http://science.ksc.nasa.gov/pao/faq/faqanswers.htm

Yes, yes, I can. You're forgetting a little something called logistics. It's all well and good to say that you're going to launch a rocket from your orbiting city and that this would be cheap but you're forgetting that you first had to get that rocket to the city. Whether you build that rocket on the ground and launch it to the city or you get all the raw materials to the city and build the rocket there is largely irrelevant... You still have to get the mass to the city in the first place and that has never been a cheap/easy proposition nor are there any realistic proposals to make it cheap/easy in the future.

 

Weather Stations and Observatories

Weather stations and observatories in orbiting cities most likely would be common place. Not only would they be beneficial while in orbit, but once they left orbit to go to Io, mars, etc. they would be a necessity in studying other worlds and their surroundings.

You say that like we don't already have such. We do.

 

Space Mining

Space mining is something we are going to have to do, the Earth just doesn't have enough resources to sustain us forever. Space mining would be ridiculously costly if every time we mined something we had to send it back to Earth to process just to send it back into space. If we had refineries and factories in space near the mining, long term costs would be a lot less.

Space mining will be ridiculously costly. Period. I'll grant the exception for (say) a mine on Mars with intended usage for the mined materials being the Mars colony next door. But once you start talking about moving the mined materials from one orbit to another you're talking about ridiculously expensive.

 

Flying cities could be the first step to long term colonization of space. If we could build cities in orbit and they could sustain themselves for long periods of time then colonization of other places would be easier to comprehend and manage. For instance, Mars is a very nasty place with all of its dust storms. http://science.nasa.gov/science-news/science-at-nasa/2001/ast16jul_1/ Storms that would make exploration and colonization a real hassle, but if explorers and colonists were safely tucked into orbit storms wouldn't be a bother to them.

Tell ya what... As a dry run, build a self-sustained city in Antarctica. Or maybe 500 feet under water at the bottom of the ocean. Either of those tasks will be ridiculously easy compared to any orbiting platform. And yet....

Edited January 20, 2012 by InigoMontoya

[michel123456]

There is a wrong idea of what a city is.

In order to live, a city like Paris (about 10 million inhabitants) has an impact radius of more than hundred kilometers. Each day, thousand of tons of material are pumped into the city: it is energy from power plants outside, food for the 30 millions meals to be prepared every day, water and a lot of other stuff coming from ports, airports, by train, by highways. Similarly there is a huge movement in the reverse direction, waste, industrial production, etc. from the city to the outside. The idea of creating a bunch of buildings and putting people inside to work and live litteraly cutted off from the rest of the world, is a pure dream.

[Axioms]

A city that can fly. Fun.

 

It would probably be cheaper to build 5000 skyscrapers over 500m high which would be easier to manage. Lets go with our imaginations here though. You would need to define an area that you want to lift into the air. Let us go with 5km^2 + how ever much foundation we need. When that is decided how would you get supplies up to the city when it is in flight? Will everyone in the city have a job? Or will it be for the wealthy only? Setting social and economic problems aside, how will the city be lifted into the air? If it doesnt crumble, I dont think it would be structually sound, what amount of energy would be required to keep it there? So many little factors that just seem to make the idea far to impractical.

 

I liked the city in orbit idea. That could be constructed in space. Still economic and job problems there? Who would live there and how do they get supplies?

 

Note:

I would think that the start of the second paragraph is still much cheaper than anything else to deal with the over population.

[InigoMontoya]

I would think that the start of the second paragraph is still much cheaper than anything else to deal with the over population.

Nah... Over population is self correcting and very cheap to correct.

 

It's called "famine."

[Axioms]

Nah... Over population is self correcting and very cheap to correct.

 

It's called "famine."

 

Yes, and we have war and disease.

 

Edit: Sorry I was thinking in terms of accommodation though.

Edited January 20, 2012 by Axioms

[InigoMontoya]

Yeah, but war is expensive.

 

Disease is cheap though.

[Moontanman]

Here is what you need to make cities fly....

 

http://en.wikipedia.org/wiki/Spindizzy

[Axioms]

Here is what you need to make cities fly....

 

 

If we could do that then yes maybe. It would still depend on how much it would cost to keep generating it.

 

Yeah, but war is expensive.

 

Disease is cheap though.

 

Somebody always profits from war. Disease can get expensive if it is in a country that cares for its people and has enough funds to do so. Famine and disease usually go together though. All much cheaper than building a load of buildings.

[searchingfortruth]

1. Some day we will have the technology to send MILLIONS of people into space daily. That is what this topic is about the future not the now.

 

2. When we have the technology to build a city that can travel our solar system and sustain itself why would we have to send a rocket to it? A true self sustaining city would have the ability to make its own rockets (why in the future we are still using rockets I don't know.) Most cities have FACTORIES and they will be able to make their own Rockets.

 

3. As too already having weather stations and observatories, I know we have them, BUT we don't have them orbiting EVERY planet and moon. So unless our future space travelers only want to go to the places we have already seen we will need more.

 

4. The definition of a "Space" mine; Is a mine IN space. If we have city ships IN space why would we need to send anything back to Earth unless they needed something? All they would have to do is orbit a asteroid they are mining and send the materials to the city ship.

 

5. You want proof that a self sustained civilization is possible? Look around. All of humanity is a part of a self sustained civilization in space. That is unless you know of some outside source that has been sending us things?

 

The purpose of this topic was to see what people thought about our future space exploration, and how we would be doing it. For some reason it seems you believe that I was planning on building one in my backyard tomorrow. Again this topic was about our future not our present.

And you're fooling yourself if you think space is the answer to over population.

 

Global population increase is roughly 1% per year. There are 7,000,000,000 people on Earth. That means that to simply maintain our current population we would have to launch 191,000 people PER DAY into space.

 

Every day.

 

Not gonna happen.

 

Space may be the answer to a lot of problems, but that ain't one of them.

 

 

Yes, yes, I can. You're forgetting a little something called logistics. It's all well and good to say that you're going to launch a rocket from your orbiting city and that this would be cheap but you're forgetting that you first had to get that rocket to the city. Whether you build that rocket on the ground and launch it to the city or you get all the raw materials to the city and build the rocket there is largely irrelevant... You still have to get the mass to the city in the first place and that has never been a cheap/easy proposition nor are there any realistic proposals to make it cheap/easy in the future.

 

 

You say that like we don't already have such. We do.

 

 

Space mining will be ridiculously costly. Period. I'll grant the exception for (say) a mine on Mars with intended usage for the mined materials being the Mars colony next door. But once you start talking about moving the mined materials from one orbit to another you're talking about ridiculously expensive.

 

 

Tell ya what... As a dry run, build a self-sustained city in Antarctica. Or maybe 500 feet under water at the bottom of the ocean. Either of those tasks will be ridiculously easy compared to any orbiting platform. And yet....

[Moontanman]

Mining is space would be costly to set up but not necessarily costly to do once set up, but moving stuff around in slow orbits would easy, if the "stuff mined" was used in space then it would fantastically less expensive than bringing it to earth orbit from the surface of the earth. There is really not much point in bringing stuff back to earth due to costs but transporting say pig iron to the surface would be relatively easy to do compared to bringing materials to orbit from the earth or any other deep gravity well, at some point mining will become much more expensive than it is now on the earth, at this point these colonies become potentially cost effective but not before.

 

Transporting excess population from the earth is not going to work, we reproduce far faster than any conceivable method of doing so.

 

Freely orbiting colonies once established could be moved around the solar system quite easily as long as speed isn't required. Places like the Lagrange points of Jupiter have enough material to build lots of stuff as long as it contains lots of carbon. orbiting colonies will be made of primarily of carbon fibers or nano tubes not metals.

 

Orbiting colonies is the next step IMHO, not colonizing Mars or any other planet. Artificial gravity made by rotation torus shaped colonies will be possibly the preferred method, possibly moving these things by magnetic sails. But the Earth is not going to benefit from population wise from this but raw materials and manufactured goods could conceivably be transported to the earth by using atmospheric braking, if there are valuable goods that can only be made in orbit I can see some sort of trade merging but real trade would be between colonies.

 

Mars does have the advantage of allowing a space elevator to be built much easier than on the earth, if i remember correctly Kevlar is strong enough to make a space elevator on Mars...

Edited January 21, 2012 by Moontanman

[InigoMontoya]

1. Some day we will have the technology to send MILLIONS of people into space daily. That is what this topic is about the future not the now.

Some day we will have the technology to colonize the Sun! See how easy that is to say? Now, do you honestly believe that it will EVER be possible? From my perspective, asserting that we will ever have the tech to send millions of people into space daily is equally believable. You're not even talking science fiction, you're talking pure fantasy.

 

2. When we have the technology to build a city that can travel our solar system and sustain itself why would we have to send a rocket to it? A true self sustaining city would have the ability to make its own rockets (why in the future we are still using rockets I don't know.) Most cities have FACTORIES and they will be able to make their own Rockets.

Re-read my post. See where I said, "or you get all the raw materials to the city and build the rocket there?" Yeah, I'm conceding that perhaps you'll want to build the rockets in the city. But it doesn't make any difference, you can't make that rocket out of vacuum. You have to make it out of *something*. That means that you have to get the RAW MATERIALS to your city. Raw materials are hard to come by in space, ya know? Sure there's the odd asteroid, but they aren't exactly known for their diversity. And how do you propose to move that city without a steady supply of reaction mass? In other words... DeltaVelocity = ExhaustVelocity * ln (MassRatio). Please explain the technology you plan to use to invalidate that equation.

 

3. As too already having weather stations and observatories, I know we have them, BUT we don't have them orbiting EVERY planet and moon. So unless our future space travelers only want to go to the places we have already seen we will need more.

Trivial compared to the other issues in this post.

 

4. The definition of a "Space" mine; Is a mine IN space. If we have city ships IN space why would we need to send anything back to Earth unless they needed something? All they would have to do is orbit a asteroid they are mining and send the materials to the city ship.

I never said you would have to send them back to Earth. I said you would have to change orbits. Like it or not, moving from one asteroid to your city requires enormous amounts of energy (ie, you have to change orbits). That right there makes the process "ridiculously expensive." In other words, you're back to that DeltaVelocity equation.

 

5. You want proof that a self sustained civilization is possible? Look around. All of humanity is a part of a self sustained civilization in space. That is unless you know of some outside source that has been sending us things?

Sure. And all it takes is a space ship that weighs in at 10^22 kg and was gifted to us. Find a way to replicate that cheaply.

 

The purpose of this topic was to see what people thought about our future space exploration, and how we would be doing it. For some reason it seems you believe that I was planning on building one in my backyard tomorrow. Again this topic was about our future not our present.

I'm not assuming building in your backyard tomorrow. I am, however, assuming that we more or less have the Laws of Physics down. Now, if you're saying we get to throw out those laws then I propose that this isn't a topic on the future but rather a topic on creative writing.

Edited January 21, 2012 by InigoMontoya

[searchingfortruth]

Well so far Phi For All is the only one on topic here. The topic is supposed to be "How To Make A Flying City" and nobody is discussing this. So here are some questions. What propulsion system would we use? What type of design? How would we make it? What would we use to make it? How would we power it?

[Moontanman]

Well so far Phi For All is the only one on topic here. The topic is supposed to be "How To Make A Flying City" and nobody is discussing this. So here are some questions. What propulsion system would we use? What type of design? How would we make it? What would we use to make it? How would we power it?

 

 

If you mean a city that flies through the air then there is only one way, a giant hot air balloon, I've seen some studies, some place, about it, it's feasible, given a power source but of course the devil is in the details, there is no appropriate power source available at this time...

[michel123456]

Some day we will have the technology to colonize the Sun! (...)

 

Yes, at night of course.

[CaptainPanic]

To live in a flying city would be truly amazing, but how would we make it fly, power it, and control it?

1. Some day we will have the technology to send MILLIONS of people into space daily. That is what this topic is about the future not the now.

Well so far Phi For All is the only one on topic here. The topic is supposed to be "How To Make A Flying City" and nobody is discussing this. So here are some questions. What propulsion system would we use? What type of design? How would we make it? What would we use to make it? How would we power it?

You're confusing me with what you want. In the 1st post, you give the impression you want to talk about realistic and practical things. Things we can build right now if we had enough money and motivation.

 

But in another post (#19), you talk about future tech that we might develop some day.

 

The difference between "practical, right now", and "future tech, some day", is that right now we have limited energy, and some day, we might have almost infinite energy. And that makes a huge difference when you talk about getting stuff into orbit!

 

If you want to get a lot of stuff into orbit, you need a LOT of energy. Low Earch Orbit is about 7.8 km/s, so the kinetic energy for 1 kg is about 30 MJ/kg (excluding all practical issues - in current rocket technology you need to spend a lot more energy).

 

So, what's the topic of the thread? Practical orbital city with real technology (but unlimited financial means)? Or future technology, bound only by the laws of physics (in other words: sci-fi)?