If you wanted to build such a thing, I think the way to go would be:
Build the dome on the bottom of the ocean covering the Titanic. You’d have to seal the whole dome, including the bottom, which would mean tunneling under the ship and laying steel or whatever, and then sealing the whole dome.
Pump out the water slowly, reinforcing the wreck and coating it with preservatives or whatever as you expose it.
3a. Use submersibles with airlocks to get people down to it, keeping them at ambient pressure the whole time.
or,
3b. Before you drain the dome, you start building your shaft to the surface. Once you get the thing to the top, you just start pumping the water out of the top until you get down to the wreck. Then pump out the dome as before.
In reality, of course this is all horribly impractical. I don’t think you could keep the wreck from becoming nothing but a lump of rust and twisted steel once you pumped the water out, and the forces involved would be absolutely immense.
The problem of getting people up and down is trivial. Rather than hanging elevators from cables, I think you’d just attach them to a track on the wall with sprockets and let them crawl their way up and down. You could even have an inner spiral staircase with the elevators on the outside, so that if an elevator failed you could just open the doors and walk out into the stairwell.
I’m thinking that Q.E.D is mistaken about air pressure/bends issues not being a problem. With an additional 2.5 miles of air you’d end up with something like 2 atomspheres of pressure. It isn’t just the pressure that gives you the bends but the amount of time you spend breathing under the pressure. You can get the bends (if some vaguely remembered readings count as a cite) 10 feet down, if you stay there long enough. Since we’d be looking at 5 miles of elevator rides and a nice stay at the bottom to make the $150,000. entrance fee worthwhile it would be several hours. I’m guessing you’d bend rather nicely.
So are we talking about a structure that can keep the interior at 1 atmosphere? I don’t think we’re anywhere close to even think about doing it.
The closest thing we have is a dam. Most dams just use lots and lots of mass (concrete) to withstand pressure, but there are “thin arch” dams which use steel reinforcements and other techniques to minimize the wall thickness. Morrow Point Dam is one example - it’s 468 ft deep and it’s 52 ft thick at the bottom. (Cf: Yellowtail Dam, a thick-arch construction, 525 ft deep and 147 ft thick.)
Water pressure is proportional to depth, so at the Titanic wreck (12,400 ft or so) the pressure is about 30 times higher. I’m not sure how the thickness vs. strength scales for such structures, but if strength is proportional to square of thickness you will need a 300 ft thick dome. And that’s not even considering the effects of curvature and size. The Titanic would never fit in the Morrow Point Dam anyway so it would have to be larger, and correspondingly stronger. There’s also the problem of constructing the proper foundation; dams are usually built to transfer pressure to the adjacent rock face, but I doubt you’d find a good strong foundation on the bottom of the sea.
And what’s the point of leaving the ship on the bottom of the sea if you’re going to disturb it by constructing this monstrous dome and pumping the air out? It’s so much easier to raise it and put it in a climate-controlled dome on land. Either that, or build a fleet of submarines for tours.
scr4, the interior doesn’t have to be at 1 atm of pressure, it could be any pressure (this being a hypothetical situation) that allows humans to live. 1 atm would be nice, of course, but even if it were at the edge of what humans could survive that would be acceptable.
And I’m not sure, but I think that a dome is stronger than an arch, so it might not have to be as thick as you’re saying. Of course, IANAE, so I could be completely wrong about this.
If the shaft is connected to the surface then the pressure equals that of the water surface (1 atm). Extreme pressure is exerted on the outside of the shaft, not the inside. Though I doubt a 2 mile steel shaft will resist the pressure of all that water. Maybe if a fancy lattice structure is added to the shaft.
The bends is usually the result of strong concentrations of gas dissolving into bloodstream from your lungs. This only happens under pressures greater than 1. When a diver ascends rapidly, the nitrogen and other gases are trapped in the body and are no longer dissolvable. This is very painful and i think can lead to ameurysms. The is what i remember from my scuba certification courses.
So the bends is also not a problem. Proper Ventilation would be.
Heck no. Our atmosphere is a lot thicker than 2.5 miles. This works out to 13,200 feet. Per Babinet’s formula, this works out to an additional 13.8 inches of mercury, or about .48 atmospheres. This is roughly equivalent of a dive to about 15 feet, which is above the minimum bends depth.
I’m still thinking not, Q. E. D. . It’s true the atmosphere is much thicker than 2.5 miles but as you go up you lose atmosphere fairly quickly. At the top of Everest, for example, air pressure is about half of sea level. The top 10 miles or so add almost nothing.
As you go down you gain pressure faster.
And again it’s pressure and time under pressure that give you the bends. A 5,000 foot dive taking 1 minute while probably killing you for any number of non-bends related reasons would be unlikely to give you the bends. This being based on some WAGs, barely remembered readings, and other suspect sources that may or may not apply.
I also realize arguing science with you is fighting a very steep uphill battle. So please don’t hurt me.
Bear in mind too that as you go farther down, it gets warmer. The air is therefore less dense than it would be if the temperature were constant right to the top of the atmosphere. I didn’t take this into account in my calculations, so I was actually overestimating the pressure at the bottom of our shaft. In researching this thread, I found several references to a hotel in Florida or someplace that lets divers stay overnight at a depth of 15 feet. There are no ill efffects from this. I also found several articles which quote the minimum bends depth to be 18 feet, which is well above the pressure level in our shaft.
The Denver TV weathermen used to say that, all other things being equal, you lose 4° F for every 1000 feet of altitude gain. Would that hold true in the opposite?
I think it would be more complicated than that. Since this is a museum and tourist attraction, we’ll want to have climate-controlled conditions. Also the water in the North Atlkantic is damned cold and gets colder the deeper you go. So, we’ll need some pretty beefy heaters to keep the chill out.
The ‘lapse rate’ is the temperate differential in the atmosphere as you gain altitude, and it’s about 4.4 degrees F. for every thousand feet. All else being equal, of course - the air temperate 2000 ft above Lima Peru is likely to be much warmer than the air temp at sea level at the north pole.
Heating the air through increased pressure will not be a problem at all. In fact, you’re going to need some big freakin’ heaters to keep people comfortable down there - the ambient temperate in the ocean around those parts is just above freezing, and very soon the walls will be at ambient and the whole structure will act like a big refrigerator.
The bends also won’t be a problem. As has been mentioned, at that depth you’re not even a 2 atmospheres of pressure. And it’s going to take you a long time to get to the top anyway.
So, how did the workers in the casions of the Brooklyn Bridge get the bends? Was the air pumped in under pressure? Or was it snorkled? They were only at 40 - 80 ft deep. And yet several of them suffered the bends, including the builder, Roebling.
Seems to me that keeping the shaft open to the surface will be vital for the health of the visitors. What type of structure could survive the extremes that that hollow tube would encounter?
If I’m not mistaken, isn’t that area also a very dangerous one-the Titanic is buried sixty feet into the mud, I think, and there are earthquakes around that area. (It’s still not known how much damage was down to the wreckage during the 1929 earthquakes at the Grand Banks).
Robert Ballard (the man who found the wreckage) DID speak of a possible museum at the wreck of the Britannic, Titanic’s sister ship, only with cameras mounted down on the wreckage, so that one could see the ship from the surface. I don’t know how feasible that would be.
The air in the caisson is kept at high pressure to keep the water out. The pressure has to be equal to or greater than the pressure of the water at depth, in fact. So, it was as if the workers were working 40 - 80 feet underwater.
I wondered when you were going to weigh in on this. As for Ballard, he’s talked about doing that with a number of wrecks, but IIRC, he’s dropped the idea shortly afterwards because each time he finds a wreck, other folks immediately flock to the area and begin mucking about.
So what IS a reasonable pressure to use, anybody? I’m guessing it’s more a matter of keeping the decompression time reasonable. (I’m having a surprisingly hard time googling for the maximum survivable depth because I don’t understand the various diving-related jargon)
“The bends” happen when nitrogen, which is dissolved in the blood at high pressure, turns into bubbles at lower pressure. If there’s not nitrogen, you won’t get the bends. Not that I remember, but I believe there are some gasses that don’t exhibit that behavior, so we just use a mix of those with oxy, pressure up the underwater dome so it doesn’t implode, and we’re off to the races.
Of course, that’s what they do in the deep-diving mini-subs, and those things are only a few dozen feet in size. A dome like we’re talking will be…more difficult.