Tower of Babel - Modern technology to reach Heaven ?

John Creighton · 2004-05-16 12:31:24

Just curious what is finite element analysis? Anyway if optimization is the goal we need some sort of cost function to minimize. Once we have a cost functions various algorithms could be tried such as gradient decent, conjugate gradient, quasi Newton, genetic algorithms, etc.

John Creighton · 2004-05-16 12:36:13

I think to design a foam metal structure you would start from the top and figure out how much compressible load each layer must be able to withstand, and what kind of a moment it must be able to resist, due to wind loads. Each cell would of course be designed to deal with the shear loads. Anyway, you proceed in this fashion making each layer as light as possible to meat all the design criteria until you get to the bottom. If you find the base is too big you make a smaller tower or reduce the amount of weight the tower must be able to support.

John Creighton · 2004-05-16 12:43:23

I am not sure how the anchored air ship thing works. If the air ship is supported by a cable and above the height of a hurricane there will still be prevailing winds up their. The higher up the airship, the greater the winds. Unless the cable is in extreme tension this means that the cable will not go straight up. The more the cable deviates from straight up the more it will weigh per height and the more wind load will be on the cable. Consequently, it is not clear to if the anchored airship is superior to the foam metal tower. However, the two concepts can borrow from each other. If you look at a radio tower it is supported by three cables to help deal with wind loads.

MarsDog · 2004-05-18 13:28:32

I was searching for metal foam properties, and most is proprietary empirical, theoretical models are not well developed.
-
I have not figure out how relatively few balloons can support 20 people on a plywood sheet. Somehow the pressures within the balloons get distributed below the popping pressure. (The volunteers were told to move gently)

John Creighton · 2004-05-19 09:35:20

If you can find the properties of the foam and you know the properties of the metal you should be able to deduce the properties of the foam metal. Since the metal is thin the compressive strength will come mostly from the foam. Since the foam will probably have negligible tensile strength, the tensile strength will probably come mostly from the metal. The tensile strength could be greatly improved if instead of just using sheet metal on the outside of the foarm, nanotubes were mixed into some kind of metal matrix. You already know the compressive strength of the foam .To get a rough idea of how the stuff works the only other number we really need is the modulus of elasticity and the density of the foam. By the way, do you want to try to design such a structure? What height should we try first? 2km? Anyway for starters and ignoring any bending and wind loads on the structure we could look at how wide the base would need to be if it was just made out of foam. I’m sure it could be made higher if parts were hollow but we need to start somewhere.

GCNRevenger · 2004-05-19 16:52:13

Unfortunatly you can't mix metal and molecular nanotubes easily... I don't know of any way you can do it without destroying the nanotubes or making them adhere well to the metal phase.

The higher up you go, the lower the air pressure, so the wind doesn't have as much push.

John Creighton · 2004-05-20 08:51:17

Unfortunatly you can't mix metal and molecular nanotubes easily... I don't know of any way you can do it without destroying the nanotubes or making them adhere well to the metal phase.

What if you had two rough sheets of metal and pressed them together with glue and a web of nanotubes in between?
Or maybe the nanotube web could be coated in something before it is pressed between the two sheets of metal. Other options include using Kevlar to augment the tensile strength or perhaps weaving nanotube fibers with glass fibers and metal fibers.

SBird · 2004-05-20 11:20:53

Some sort of electrodeposition mught be usable for putting metal down on a nanotube mat. Of course, the whole adhesion problem rears its ugly head up still but at least it should be possible to combine the two phases.

John Creighton · 2004-05-21 22:37:54

Has anyone ever tried to visualize a space elevator?. I drive towards it and I see this massive line that seems to stretch from the ground, go through the crowds and disappear into the sky. I keep coming closer and the line gets wider and wider, eventually, I start to see what looks to be like trains going straight up into the sky. I get closer and the trains begin to look bigger and bigger. The tower becomes all I see in front of me and the trains begin to look, like giant cargo ships moving straight up to the sky. These ships are filled which cargo fed by many trains like a freighter, and they return numerous packages as well. Each ship is loaded by 20 trains each on its own track. Sometimes one giant train comes and it uses all of the tracks. I step into the freighter, and It begins to rise. I feel my weight begin to increase as the freighter starts, to ascend. I look out the window and the, people shrink, then the cars, then the trees, I eventually loose sight of the rail way track, I pierce through the clouds, end the detail in the clouds becomes finer in finer until I see around them. I see that the earth begins to look curved, and I rise higher and higher. We stop at the first stop which is twice low earth orbit. Ships like to start up a little high so they can use some of the free fall to get to orbital velocity. We continue higher and higher and I notice, I weigh next to nothing. Eventually I am weightless. I look We are at the next major stop. The elevator starts up again and eventually the floor becomes the ceiling. When we arrive at the top, I board a ship. I notice that when it departs it starts to drift away before the engines are even fired. I think about the scale. There is more metal in this elevator then a city. If it falls apart pieces will be flung into space or float around the world before they hit the ground. When did technology become so large, that man became so small?

MarsDog · 2006-04-03 16:01:14

http://www.lpi.usra.edu/meetings/lpsc2001/pdf/2067.pdf

Using very cold ice, perhaps cooled with liquid nitrogen, would have advantage of low dessity, with mantle rock 3/ice 0.92 = 3.26 ratio. Floating, one volume below rock and 2.26 above. 100 km to space and 44 km below mantle rock.

Additionally, lowering ocean levels would increase Earth's land area.

GCNRevenger · 2006-04-04 07:04:05

Except that you need to reach 36,000km for a stable orbit...

And build a tower out of ICE? I can't think of a much dumber idea.

What are you talking about, lowering the Earth's oceans?

MarsDog · 2006-04-04 16:08:26

Idea is to build a large ice ramp along the equator,
starting at Pacific Ocean sea level, slowly rising to 100 km.
Evacuated tube with linear motor for propulsion.

Ice is considerably stronger when cooled, maybe 10 times at 150 Kelvin.
Ice ships were almost used in the second world war

http://www.google.com/search?client=ope … 8&oe=utf-8

As a bonus, if you build a big enough ramp,
lower ocean levels, and New Orleans is saved !
Billions for dykes or ice ramp to space ?

GCNRevenger · 2006-04-04 19:38:13

*groans*

Giant ramp to the sky... evacuated tunnel 100's km long... maglev track up to Mach-20... still only able to send up one at a time... massive destruction from a "derailing."

Then there is the ungodly amount of energy needed to make this ramp of ice, and to keep it from melting. How many trees would have to be cut down to make a "wedge" of ice 100's of kilometers long and 100km high? Answer: all of them

And it still wouldn't even support its own weight, the pressure would make the foundation deform and squish like a marshmellow being run over by a tank.

MarsDog · 2006-04-04 20:48:34

Giant ramp to the sky... evacuated tunnel 100's km long... maglev track up to Mach-20... still only able to send up one at a time... massive destruction from a "derailing."

Evacuated tube on top of the ramp. Should be safer than normal maglev because all in straight line. Think of it as a giant sized particle accelerator.

The orbital velocity at 100 km is 7.85 km/sec
At 4G acceleration:
V^2=2*4*9.8*d d = (7850^2)/(8*9.8 ) = 786 km
time = sqrt(d/(2*9.8 )) = sqrt(d/(2*4*9.8 )) = 100 seconds
Cargo can stand higher G and be accelerated to Earth escape of 11.2 km/sec.

Then there is the ungodly amount of energy needed to make this ramp of ice, and to keep it from melting. How many trees would have to be cut down to make a "wedge" of ice 100's of kilometers long and 100km high? Answer: all of them

Ok, will calculate energy needed in a day or 2. Several miles up, water freezes by itself, so just need to lift it and cool it further to 150º K. Insulate with a meter of styrafoam - will calculate guessed heat loss. Wood chips were used to make the ice ships less brittle, might be an alternative to burning sawdust, hide it inside the ice and gain Kyoto CO2 credits.

And it still wouldn't even support its own weight, the pressure would make the foundation deform and squish like a marshmellow being run over by a tank.

In the North, permafrost supports. Heavy trucks cross lakes on floating ice roads.
http://www.mvp-wc.usace.army.mil/ice/ice_load.html

From: http://www.nationalgeographic.org/seala … eek_3.html
" The catch is that because frozen sea ice has roughly the strength and resistance of a block of concrete"

Considerably better than regular concrete (20 MPa) is 150º Kelvin ice (60 MPa).
http://www.geokhi.ru/~planetology/these … ov_b_a.pdf

"The most common use of high-strength concrete is for construction of high-rise buildings. At 969 ft (295 m), Chicago's 311 South Wacker Drive uses concrete with compressive strengths up to 12,000 psi (41 MPa) and is the tallest concrete building in the United States."

Ice is still brittle near freezing point,
as evidenced by giant cliffs when a glacier breaks up into the ocean.
http://images.google.com/imgres?imgurl= … 26sa%3DN

GCNRevenger · 2006-04-05 11:47:33

Lunacy

A mountain range of ice 800m long, 100km high, and probobly at least 100km wide? You are out of your mind, thats bigger then most of the equitorial countries that could host the thing.

No material made by man could build such a structure, it would collapse from its own weight. This thing will be 100,000m/340,000ft high!

MarsDog · 2006-04-05 15:02:43

A mountain range of ice 800m long, 100km high, and probobly at least 100km wide?

For simplicity assume equilateral triangle, rising from sea level.
2/sqrt(3) * 100 = 115 km base at sea level.

Appoximate form for ice fields is a parabola. Very shallow near melting.
How low temperature for what size base ?
Trying to find out.

You are out of your mind,
thats bigger then most of the equitorial countries that could host the thing.

Countries in drought could use an ice mountain ramp range, even if well insulated.
Think of the precipitation and rivers that would flow from it.
Space tourism, downhill skiing ? put on your spacesuit first.
Only 8 meter drop in sea levels, so New Orleans would need smaller dykes.
If you built 12 of these then Earth would gain extra 4% land area.

No material made by man could build such a structure, it would collapse from its own weight. This thing will be 100,000m/340,000ft high!

"The best graphite epoxies I know of (Amoco 'Thornel' type T40 carbon fiber + type
1962 epoxy) have a compressive strength of 250,000 psi and a density of
0.06 lb/cubic inch. Thus their scale height is 4.16 million inches (106 km)"
For 1 billion dollars 111 mile high tower is given:
http://yarchive.net/space/exotic/tower_launch.html
http://campus.murraystate.edu/academic/ … carthy.pdf

==============================

see for scale height equation and explanation:
(bottom area is 2.718 times area of top for the scale height)
http://en.wikibooks.org/wiki/Space_Tran … /Methods/1
Amoco T300/ERL1906: 1930 MPa / (1827 kg/m^3 x 9.80665 m/s^2) = 107,793 meters
steel: 125 MPa / (7800 kg/m^3 x 9.80665 m/s^2) = 1,635 meters
Ice: 20 MPa / ( 920 kg/m^3 x 9.80665 m/s^2) = 2,218 meters

So scale height for Ice is comparable to steel
Advantage of ice is that it floats, while steel sinks towards Earth's center.

==============================

Looks like 2 ways to build ramp to space:

(1) use very high strength materials for slender 20:1 base/height structure
(2) Giant low slope ice ramp

John Creighton · 2006-04-08 02:07:22

"ice ice baby"

Rxke · 2006-04-08 03:40:17

Okay Einsteins: how about a figure of how much ENERGY it will take to:

1) freeze such an amount of water;
2) keep it frozen.

Oh, and how are you supposed to keep the BASE solid? at that kind of (weight-induced) pressures?
Hint: liquid H2O is more compact than Solid H20...

Talk about a dead in the water kind of idea...

GCNRevenger · 2006-04-08 07:17:44

Yep. Also note how MarsDog said that ice would flow slowly under pressure, but he ignores this problem completly? If you build a tower out of ice, reguardless if the ice can support the weight or not without outright fracturing, it will squish like a marshmellow in a frying pan.

Concrete doesn't do this, which is why we make sky scrapers out of it.

MarsDog · 2006-04-08 08:09:17

1) freeze such an amount of water;
2) keep it frozen.

water latent heat of fusion = 334 (kJ/kg)
Heat capacity (solid 0 °C) = 2.06 kJ/(kg·K)
Water freezes at higher elevations, but need energy to lift it there.

Insulate top with styrafoam/aereogel combination ?
Bottom, just absorb the geothermal, as Antarctic ice does.

Will plug in numbers later.

Oh, and how are you supposed to keep the BASE solid? at that kind of (weight-induced) pressures?
Hint: liquid H2O is more compact than Solid H20...

"The minimum temperature that liquid water can exist without ever freezing is -21.985°C at 209.9 MPa; at higher pressures water freezes to ice-three, ice-five, ice-six or ice-seven at increasing temperatures"
taken from: http://www.lsbu.ac.uk/water/explan2.html#Pmelt

Talk about a dead in the water kind of idea...

Greenland is melting. Hide the extra water where ?
Solar energy is greater in the tropics, easier to do than cool Greenland.

===================================

If you build a tower out of ice, reguardless if the ice can support the weight or not without outright fracturing, it will squish like a marshmellow in a frying pan.

Function of temperature; the question is over what time frame ?
Bedrock creeps over geologic time.
Trying to learn the answer.

GCNRevenger · 2006-04-08 08:33:08

Ice is a solid because of hydrogen bonding between molecules, while rock is a solid because of ionic (or sometimes covalent) bonding. Hydrogen bonds are relativly weak, and Ice would creep over much shorter time scales.

But anyway, this idea is sheer lunacy, to build a mountain range 100km+ high and 800km long right at the equator would surely take more energy then the Earth has to offer for the project. I won't even bother to address this idea any more, its insane.

MarsDog · 2006-04-08 19:11:35

Ice is a solid because of hydrogen bonding between molecules, while rock is a solid because of ionic (or sometimes covalent) bonding. Hydrogen bonds are relativly weak, and Ice would creep over much shorter time scales.

The properties of high pressure, low temperature ice are not well known.

100 km is around 10,000 atmospheres; for 2,000 atmospheres:
"These new results show that the viscosity of a deep icy mantle is much lower than we previously thought," said William Durham, a geophysicist in Livermore's Energy and Environment Directorate."
http://www.sciencemag.org/cgi/data/311/5765/1267/DC1/1

Viscosity = (shear strain rate)(Stress)
http://www.uwsp.edu/geo/faculty/heffera … nrate.html

Base might approach 10^12 Pa or 1 TPa
Not quite metallic water: "The calculated pressure of metallization 1.76 TPa"

The recent data might prove you right. Will have to plot and see.
But extrapolating this way is just guessing.

But anyway, this idea is sheer lunacy, to build a mountain range 100km+ high and 800km long right at the equator would surely take more energy then the Earth has to offer for the project. I won't even bother to address this idea any more, its insane.

Volume of water possibly same as Greenland glaciers.
Will calculate the number for solar days or years for the area covered.

====================

Calculate parabola from here:
http://epsc.wustl.edu/~epsc353/lectures/flow_03_p1.pdf

John Creighton · 2006-04-08 21:06:35

You realize a lower viscosity works against you as viscosity is the tendency to resist flow.

MarsDog · 2006-04-08 21:23:22

Ice is a solid because of hydrogen bonding between molecules, while rock is a solid because of ionic (or sometimes covalent) bonding. Hydrogen bonds are relativly weak, and Ice would creep over much shorter time scales.

Strength of hydrogen bond increases with pressure, according to expert opinions.

You realize a lower viscosity works against you as viscosity is the tendency to resist flow

True, can guess at strain rate.
10^-15 would be considered a solid = 30 million years.

Extrapolating one graph gives around 50° K for that figure.
Have not found any measured data for low temperatures at 1 TPa.

However such high pressure exists only at the bottom center,
reducing strength requirements.

Worst case is angle of repose, 1.5 to 1 slope giving 300 km base.
Will calculate energy to freeze, cool the ice, and keep it cold after.

http://www.geocities.com/marscatdog/

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#26 2004-05-16 12:31:24

Re: Tower of Babel - Modern technology to reach Heaven ?

#27 2004-05-16 12:36:13

Re: Tower of Babel - Modern technology to reach Heaven ?

#28 2004-05-16 12:43:23

Re: Tower of Babel - Modern technology to reach Heaven ?

#29 2004-05-18 13:28:32

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#30 2004-05-19 09:35:20

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#31 2004-05-19 16:52:13

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#32 2004-05-20 08:51:17

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#33 2004-05-20 11:20:53

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#34 2004-05-21 22:37:54

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#35 2006-04-03 16:01:14

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#36 2006-04-04 07:04:05

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#37 2006-04-04 16:08:26

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#38 2006-04-04 19:38:13

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#39 2006-04-04 20:48:34

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#40 2006-04-05 11:47:33

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#41 2006-04-05 15:02:43

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#42 2006-04-08 02:07:22

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#43 2006-04-08 03:40:17

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#44 2006-04-08 07:17:44

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#45 2006-04-08 08:09:17

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#46 2006-04-08 08:33:08

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#47 2006-04-08 19:11:35

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#48 2006-04-08 21:06:35

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