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Details of a hovercraft city.


mitch1224

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I am making a game, and one of the things involved is the city of Atlantis. As Atlantis is overused, I decided to make it different. So, in the game, Atlantis is a hovercraft city that flies around the Mediterranean. How much energy would it take for a modern-type city of about 3 mi diameter to fly about 50 feet above the sea level? Using, say, a Hydrogen power plant.

 

Assuming it is made of an incredibly light material and is about 100 feet tall.

 

Also, if it sank, how much water would it displace?

I need to know that so I can remap the Mediterranean sea for an area with much less water.

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I am making a game, and one of the things involved is the city of Atlantis. As Atlantis is overused, I decided to make it different. So, in the game, Atlantis is a hovercraft city that flies around the Mediterranean. How much energy would it take for a modern-type city of about 3 mi diameter to fly about 50 feet above the sea level? Using, say, a Hydrogen power plant.

 

Assuming it is made of an incredibly light material and is about 100 feet tall.

 

As a first approximation I would just extrapolate an existing hovercraft to a giant size:

Existing hovercraft

Length: 29.3m long

Width: 15m beam

Weight: 70 tonne all up weight

Power: Lift engines - 2 x air-cooled, turbo charged, MTU 12V2000-R1237K37 diesels - each producing 675kW + Propulsion engines - 2 x air-cooled, turbo charged, MTU 16V2000-R1637K37 diesels producing 899kW

 

So, 3 mile (4.8 km) diameter is a surface of 18,000,000 m3 of surface, which is approximately 41,000 times as large. So:

 

City-size hovercraft

Diameter: 3 miles (4.8 km)

Displacement 3 million tons

Power: 129 GW (GigaWatt)

 

The power consumption should benefit from the large scale though, so without any calculation, I would just divide that by 10. Power: 13 GW.

Since that's a lot more than the city will use for all other things (like lights, heating), you can just take that as the total power requirement.

 

Also, if it sank, how much water would it displace?

I need to know that so I can remap the Mediterranean sea for an area with much less water.

It will displace its own volume.

I would assume that the average density of the construction materials is 2000 kg/m3, so the displacement of water is half that of the weight of the hovercity: 1.5 million tons of water.

 

 

Of course, this is all not much better than a wild guess... You can make a million assumptions to move the answers in any direction you like, so if you're not happy with it, feel free to change it. :)

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As a first approximation I would just extrapolate an existing hovercraft to a giant size:

Existing hovercraft

Length: 29.3m long

Width: 15m beam

Weight: 70 tonne all up weight

Power: Lift engines - 2 x air-cooled, turbo charged, MTU 12V2000-R1237K37 diesels - each producing 675kW + Propulsion engines - 2 x air-cooled, turbo charged, MTU 16V2000-R1637K37 diesels producing 899kW

 

So, 3 mile (4.8 km) diameter is a surface of 18,000,000 m3 of surface, which is approximately 41,000 times as large. So:

 

City-size hovercraft

Diameter: 3 miles (4.8 km)

Displacement 3 million tons

Power: 129 GW (GigaWatt)

 

The power consumption should benefit from the large scale though, so without any calculation, I would just divide that by 10. Power: 13 GW.

Since that's a lot more than the city will use for all other things (like lights, heating), you can just take that as the total power requirement.

 

 

It will displace its own volume.

I would assume that the average density of the construction materials is 2000 kg/m3, so the displacement of water is half that of the weight of the hovercity: 1.5 million tons of water.

 

 

Of course, this is all not much better than a wild guess... You can make a million assumptions to move the answers in any direction you like, so if you're not happy with it, feel free to change it. :)

 

Thanks. Would it be more plausible for it to be antigravity or a hovercraft (assuming antigravity/null gravity was known to the city's inhabitants)? Also, how much would that change the look of the Mediterranean?

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If by changing the looks of the Mediterranean sea you mean the rise in sea level due to the city sinking the answer is "not at all". A million tons of water is 1 mm height of water over a 100 km times 100 km square - the Mediterranean sea is much larger than such a square (and connected to the Atlantic, of course).

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If by changing the looks of the Mediterranean sea you mean the rise in sea level due to the city sinking the answer is "not at all". A million tons of water is 1 mm height of water over a 100 km times 100 km square - the Mediterranean sea is much larger than such a square (and connected to the Atlantic, of course).

 

Woah. Ok, thanks.

 

Where would it be most likely to be destroyed/buried? Im thinking Nile River Delta, but im not sure 6000 years there could bury it. Any ideas?

Could possibly be on land if no options in sea. Also think of any historic events that happened there that couldve buried it more. It sank in 3500 BCE, game world.

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Thanks. Would it be more plausible for it to be antigravity or a hovercraft (assuming antigravity/null gravity was known to the city's inhabitants)? Also, how much would that change the look of the Mediterranean?

In my world, the words "plausible" and "antigravity" do not occur in the same sentence a lot.

 

But if antigravity/null gravity was known (whatever antigravity/null gravity may be), then I assume they would use it. Also, in your fantasy it wouldn't even have to cost any energy. Then the total power need would be about 1 GW for all other applications (a regular modern town of about 200,000 people, including some industry and transport, would use that much energy), unless all other applications are also from the realm of fantasies, in which case the number is quite different.

 

A town of 3 miles diameter is just a speck in the mediterranean.

Where would it be most likely to be destroyed/buried? Im thinking Nile River Delta, but im not sure 6000 years there could bury it. Any ideas?

Could possibly be on land if no options in sea. Also think of any historic events that happened there that couldve buried it more. It sank in 3500 BCE, game world.

If it is normal technology, then it would probably be buried. 6000 years is definitely enough to bury something, and the Nile delta is quite capable of (1) letting something sink into the mud and (2) depositing more sediments on top of it.

 

But if it has antigravity/null gravity, wouldn't it be more likely that it just took off into space, away from Earth? Wouldn't antigravity engines crash upwards instead of downward? I'm asking you, since you know more about antigravity than me (since it doesn't exist, except in your game / story).

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As a first approximation I would just extrapolate an existing hovercraft to a giant size:

Existing hovercraft

Length: 29.3m long

Width: 15m beam

Weight: 70 tonne all up weight

Power: Lift engines - 2 x air-cooled, turbo charged, MTU 12V2000-R1237K37 diesels - each producing 675kW + Propulsion engines - 2 x air-cooled, turbo charged, MTU 16V2000-R1637K37 diesels producing 899kW

 

So, 3 mile (4.8 km) diameter is a surface of 18,000,000 m3 of surface, which is approximately 41,000 times as large. So:

 

City-size hovercraft

Diameter: 3 miles (4.8 km)

Displacement 3 million tons

Power: 129 GW (GigaWatt)

 

The power consumption should benefit from the large scale though, so without any calculation, I would just divide that by 10. Power: 13 GW.

Since that's a lot more than the city will use for all other things (like lights, heating), you can just take that as the total power requirement.

 

 

It will displace its own volume.

I would assume that the average density of the construction materials is 2000 kg/m3, so the displacement of water is half that of the weight of the hovercity: 1.5 million tons of water.

 

 

Of course, this is all not much better than a wild guess... You can make a million assumptions to move the answers in any direction you like, so if you're not happy with it, feel free to change it. :)

Would you rather have 1 hovercraft city, or over 100 time machines? Edited by ydoaPs
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In my world, the words "plausible" and "antigravity" do not occur in the same sentence a lot.

 

But if antigravity/null gravity was known (whatever antigravity/null gravity may be), then I assume they would use it. Also, in your fantasy it wouldn't even have to cost any energy. Then the total power need would be about 1 GW for all other applications (a regular modern town of about 200,000 people, including some industry and transport, would use that much energy), unless all other applications are also from the realm of fantasies, in which case the number is quite different.

 

A town of 3 miles diameter is just a speck in the mediterranean.

 

If it is normal technology, then it would probably be buried. 6000 years is definitely enough to bury something, and the Nile delta is quite capable of (1) letting something sink into the mud and (2) depositing more sediments on top of it.

 

But if it has antigravity/null gravity, wouldn't it be more likely that it just took off into space, away from Earth? Wouldn't antigravity engines crash upwards instead of downward? I'm asking you, since you know more about antigravity than me (since it doesn't exist, except in your game / story).

 

Its not actually fantasy so much as science fiction spanning from the stone age to the far future. Also, it would have to require some power, as thats the reason itd crash. Would hydrogen power be good enough to power a city like that?

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Its not actually fantasy so much as science fiction spanning from the stone age to the far future. Also, it would have to require some power, as thats the reason itd crash. Would hydrogen power be good enough to power a city like that?

What do you even mean by "would hydrogen power be good enough?"

 

You're already throwing known physics right out the window with the anti-gravity thing. If you want to declare trained frogs rubbing sticks together as your energy source, why not? It's no less realistic. Now, it might not have the "cool factor" of "hydrogen power" (whatever that means) but it's no further beyond reality than your basic principal. As such, if you want it to be hydrogen powered... Make it so!

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What do you even mean by "would hydrogen power be good enough?"

 

You're already throwing known physics right out the window with the anti-gravity thing. If you want to declare trained frogs rubbing sticks together as your energy source, why not? It's no less realistic. Now, it might not have the "cool factor" of "hydrogen power" (whatever that means) but it's no further beyond reality than your basic principal. As such, if you want it to be hydrogen powered... Make it so!

 

Im trying to get as much scientific basis as possible for no real reason whatsoever. Im like that, so... ya.

And hydrogen power is, if im correct, harvesting the energy made creating water.

 

 

Love your name, by the way.

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Im trying to get as much scientific basis as possible for no real reason whatsoever. Im like that, so... ya.

And hydrogen power is, if im correct, harvesting the energy made creating water.

OK, so you want to burn hydrogen in an O2 environment.

 

Where are you getting the hydrogen from? And why hydrogen rather than any number of other similar fuel sources?

Edited by InigoMontoya
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OK, so you want to burn hydrogen in an O2 environment.

 

Where are you getting the hydrogen from? And why hydrogen rather than any number of other similar fuel sources?

 

Well, considering it is a highly advanced civilizations flying over the Mediterranean, it shouldnt be too hard to get water... After water is gained via some sort of man-made tornado underneath the city, it could be put through electrolysis.

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Well, considering it is a highly advanced civilizations flying over the Mediterranean, it shouldnt be too hard to get water... After water is gained via some sort of man-made tornado underneath the city, it could be put through electrolysis.

 

BZZZZ!!!!!

 

If you want to keep things as realistic as possible, you need to scrap the perpetual motion machine. You can't take water, split it into O2+H2, burn the H2, and get a net energy gain. It violates the 2nd Law of Thermodynamics.

 

Let me put it this way: You say you're going to get your hydrogen via electrolysis. OK, great. Where are you getting your electricity? From burning Hydrogen? You've got yourself an endless loop here and such loops simply don't work.

 

So.... Where are you getting your electricity from (and don't say "burning hydrogen)? 'Cause THAT is your power source. Your best bet is nuclear. Since this is such an advanced civilization, go for broke and claim fusion.

Edited by InigoMontoya
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BZZZZ!!!!!

 

If you want to keep things as realistic as possible, you need to scrap the perpetual motion machine. You can't take water, split it into O2+H2, burn the H2, and get a net energy gain. It violates the 2nd Law of Thermodynamics.

 

Let me put it this way: You say you're going to get your hydrogen via electrolysis. OK, great. Where are you getting your electricity? From burning Hydrogen? You've got yourself an endless loop here and such loops simply don't work.

 

So.... Where are you getting your electricity from (and don't say "burning hydrogen)? 'Cause THAT is your power source. Your best bet is nuclear. Since this is such an advanced civilization, go for broke and claim fusion.

 

 

Advanced civilization... cold fusion?

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No need to claim cold fusion. That one gets chuckles from many in the scientific community. Meanwhile, plain ol' fusion (ie, utilizing HOT stuff) has never been done in a sustained, controlled manner by our civilization. Thus, any civilization that has a fusion power plant of ANY kind is significantly more advanced than we are.

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No need to claim cold fusion. That one gets chuckles from many in the scientific community. Meanwhile, plain ol' fusion (ie, utilizing HOT stuff) has never been done in a sustained, controlled manner by our civilization. Thus, any civilization that has a fusion power plant of ANY kind is significantly more advanced than we are.

 

Okay, that would work. How would the city obtain it's water needs? As it is a modern-like city, it would have skyscrapers with rooftop gardens, and the center half mile is a massive compact farm, so food isnt an issue, but water would be heavy to store in large quantities. It is a moving city, so it would likely A: be loud, and therefore B: land at night. Thats a likely way to obtain water, but it would displace tons of water around it as well. Would a 50 foot wall be enough to stop the displaced water from rushing in?

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Yes, but flying over an ocean and it gets a bit trickier. Especially when its flying at a max speed of 35 MPH.

Here's a picture of how a bloody AIRPLANE can take water while FLYING. And that doesn't even have "hydrogen power" :)

 

It's funny how keeping the city flying is not a problem, but taking the water is a problem. I would say it's the other way around. Taking water is easy. Keeping skyscrapers flying is difficult. To say the least.

 

[edit] forgot the link

Edited by CaptainPanic
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Here's a picture of how a bloody AIRPLANE can take water while FLYING. And that doesn't even have "hydrogen power" :)

 

It's funny how keeping the city flying is not a problem, but taking the water is a problem. I would say it's the other way around. Taking water is easy. Keeping skyscrapers flying is difficult. To say the least.

 

[edit] forgot the link

 

I know. Science Fiction, though, so... And i scrapped hydrogen power.

 

35 mph is nothing. Stick a tube down. Suck up water (assuming you're a hover craft and are close to the water).<br style="font-size: 13px; line-height: 16px; background-color: rgb(248, 250, 252); "><br style="font-size: 13px; line-height: 16px; background-color: rgb(248, 250, 252); ">Do you have ANY training in ANY science at all?

 

 

I am a freshman in high school. Compared to people in my grade, I'm very good at science. Training, as in college classes, no. Mandatory classes is all I have.

 

I'm not saying I know tons of science. Not physics, at least. I'm just trying to make a game with friends so I can get a job out of college as a game designer, and get college funds.

You have been very helpful, so thank you.

 

 

And maybe 50, 100 feet in the air.

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OK. HS student. My apologies. I'll cut you a bit more slack.

 

Pulling up the water even 100 feet up is no big deal. You attach a water pump to the end of a hose. You drag the hose in the water. The pump pushes the water up to your platform.

 

I appreciated your honesty. Its no problem. But thank you, regardless.

 

And wasnt sure, so thank you.

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Pulling up the water even 100 feet up is no big deal. You attach a water pump to the end of a hose. You drag the hose in the water. The pump pushes the water up to your platform.

Good point: you want to place the pump near the water level, not at the upper end of the hose. You can push water up quite high, but you can only suck it up for about 10 meters.

 

And sorry to carry on about the water... it's a minor detail, but I think it's interesting.

 

I was thinking that probably you don't need a pump at all: your hovercity will hover on a bed of compressed air (the pressure below the city will be higher than the atmospheric pressure, which is the reason it can float.

 

Assume that your city weighs 20 ton/m2 ground surface (you said you have skyscrapers, so that's not so much?), then your city will exert a pressure of, well, 20 ton/m2, or about 2 bar pressure. So, if you put a pipe through the road surface down into the water, the water would come up 20 meters (all by itself, due to the higher pressure below the city). 20 meters equals about 60 ft, so that might be enough.

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