Details of a hovercraft city.

[mitch1224]

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.

 

So a pump would not be needed? And how much would that air push down the water?

[CaptainPanic]

So a pump would not be needed? And how much would that air push down the water?

Good question... I guess that the hovercity would push the water down by an equal amount. If you have 3 bar of total (absolute) pressure under your city, then logically, it would displace water like a boat would. So, under the city it should push the water level down by 20 meters. But it wouldn't move the seabed so it would lift itself up. Still, something to keep in mind when near some shallow rocky shores.

 

When I have some more time, I will look to find out how much the water is pushed down by a regular hovercraft. It should be a measureable amount.

[mitch1224]

Good question... I guess that the hovercity would push the water down by an equal amount. If you have 3 bar of total (absolute) pressure under your city, then logically, it would displace water like a boat would. So, under the city it should push the water level down by 20 meters. But it wouldn't move the seabed so it would lift itself up. Still, something to keep in mind when near some shallow rocky shores.

 

When I have some more time, I will look to find out how much the water is pushed down by a regular hovercraft. It should be a measureable amount.

 

Great, thank you. If it would be 80 meters in the air from original sea level and pushed it down 20 more, then thatd get you the 100 feet of clearance. There would still need to be a way to control output, definitely, as the first time you see the city is when its in Egypt. How would it be boarded? Boats obviously couldnt go under very well, and a 100 meter rope climb would be insanely impossible. A sort of ferry-like VTOLs could do it, but then if they get near the air wall thatd mess up or crash them. Any input?

[mitch1224]

Good question... I guess that the hovercity would push the water down by an equal amount. If you have 3 bar of total (absolute) pressure under your city, then logically, it would displace water like a boat would. So, under the city it should push the water level down by 20 meters. But it wouldn't move the seabed so it would lift itself up. Still, something to keep in mind when near some shallow rocky shores.

 

When I have some more time, I will look to find out how much the water is pushed down by a regular hovercraft. It should be a measureable amount.

 

Great, thank you. If it would be 80 meters in the air from original sea level and pushed it down 20 more, then thatd get you the 100 feet of clearance. There would still need to be a way to control output, definitely, as the first time you see the city is when its in Egypt. How would it be boarded? Boats obviously couldnt go under very well, and a 100 meter rope climb would be insanely impossible. A sort of ferry-like VTOLs could do it, but then if they get near the air wall thatd mess up or crash them. Any input?

[Realitycheck]

A set of stairs, like an airplane.

[mitch1224]

A set of stairs, like an airplane.

 

This is something that would very rarely if ever land. A hundred meter staircase would not be an ideal solution.

[CaptainPanic]

This is something that would very rarely if ever land. A hundred meter staircase would not be an ideal solution.

Then make it an elevator, or escalator. An escalator can stick out from the side. And with your sci-fi technology, you can easily imagine that it extends a few hundred meters away.

 

Your problem is not how you are gonna get people to climb up to the city. It's what they do when they're waiting for that escalator. Your hover city will be creating hurricane winds away from the city. Not the ideal place to chill out and wait.

 

I guess I would want to be dropped off by helicopter.

[mitch1224]

Then make it an elevator, or escalator. An escalator can stick out from the side. And with your sci-fi technology, you can easily imagine that it extends a few hundred meters away.

 

Your problem is not how you are gonna get people to climb up to the city. It's what they do when they're waiting for that escalator. Your hover city will be creating hurricane winds away from the city. Not the ideal place to chill out and wait.

 

I guess I would want to be dropped off by helicopter.

 

Agreed. VTOL sounds better, though, from a random and nonscientific standpoint. It also sounds more Science Fiction-y (any way to better phrase that?) than helicopter, even though both technologies exist now. For that matter, a helicopter essentially is a VTOL.

 

It would have to be very small to be able to land on, say, a boat, and would have to be very powerful at the same time to be able to not be affected by the wind. For something that will be in a danger area such as that, there would be either many unskilled pilots and many deaths or very few pilots and next to no deaths. Second option would be more obvious for an advanced civilization, especially one that would learn to maximize its population in living on a 3 mile wide floating island.