# InigoMontoya

Senior Members

394

1. ## Traveling at the speed of light

First you have to FIND a wormhole. To my knowledge, those too exist in theory only. And even if there is one, how would you know what's on the other side? There isn't much point in traveling through one if you don't know where it goes. Statistically speaking, it's more likely to dump you into space that's midway between two galaxies than it is to dump you right next to some habitable planet. Talk about a ticket to nowhere! Put it this way: At this point in our history, high speed travel through space isn't even science fiction. It's science fantasy.
2. ## Traveling at the speed of light

Did I really just see you ask how long you think it will be before we develop a substitute for what are already imaginary particles? Alex, I'll put my money down for "10 years after the Sun goes nova."
3. ## Perpetual Motion

Gravity.... If Mr. Costa's invention is everything he says it is, please explain why he has this wheel just randomly turning (where even the video points out it is influenced by wind and such) rather than generating energy? I mean, the guy does all the work to build a 5 story machine but he can't be bothered to hook up even a pissant 5 kW generator to it? Or are you saying that Big Oil has bought up every generator for 500 miles in any direction so that it's impossible for Mr. Costa to install one?
4. ## Perpetual Motion

When you're done building it... and you demonstrate that it works... Don't call us, call the Nobel Committee, because if you pull off that little stunt you WILL be winning a Nobel Prize. Pardon me if I don't hold my breath.
5. ## Traveling at the speed of light

I'm going to go out on a limb and say, "Never."
6. ## Perpetual Motion

I'll take the liberty to edit the original post and condense it down to the very most significant parts... ....And that's all we need, Broti. Perpetual motion generators are not possible. It doesn't matter what they look like or how they're supposed to work. The moment somebody starts talking about a perpetual motion machine as anything other than a thought experiment, they're showing their lack of physics education. That last part isn't an insult, mind you. It's simply a statement of fact. UNLESS, of course, they're trying to sell you something. Then they can take it as an insult.

Which may not be an issue as long as the O2 is reintroduced at a suitably low rate. More to the point, your operation could look something like this.... 1) Fire breaks out. 2) People toss in grenades, knocking the flames down if even for a few minutes gaining precious time until.... 3) The Fire Department arrives to fight a fire that is MUCH smaller than it would have been had the fire gone unchecked. And that step 3 could become.... 3a) Fire Department tosses in a few grenades knocking down the flames while they're running hoses and such. 3b) Fire Department kicks in the door, sprays some water around to cool the place off, and the fire is defeated quickly with little or no risk to personnel.

9. ## underwatter city

Which really isn't a big deal. As I mentioned in the other thread, you could just have an elevator that goes to the surface. Beyond that, it's not much more difficult than supplying Catalina Island (population 4,000ish) and nobody gives that one so much as a second thought. A blender, a pump, and a pipe. Easy. And your elevator superstructure could just as easily include some large air handling equipment. Do it right and have two elevators separated by 100 meters or so and you could do intake on one side and exhaust on the other. Fresh air aplenty. And this one is why I respond... As one who grew up in a remote town with a population of 14k... We just accepted that if we got hurt too badly, we were going to die. You don't *HAVE* to have a highly sophisticated hospital. You just have to accept that the level of injury/illness that results in death is a bit lower than if you live next door to a trauma center. An incinerator. Easy. Another easy one. Just treat it like any submarine or warship today. Lots o' water tight doors that aren't simply left open for the heck of it. No more or less than any other city. The city I live in has a lot of metal buildings, but I'm not aware of any steel mills around here.... And why would the isolation have to be permanent? The same kinds of things that happens to small towns today if there's a natural disaster that disrupts the supply chain. Don't get me wrong, I don't see an underwater city as feasible, but the reasons are primarily associated with cost. The technical challenges absolutely are solvable as evidenced by the existence of the modern nuclear submarine. In the simplest case, you could just build 500 subs and park them on the bottom right next to each other. Now put in some "tunnels" to get from one sub to another... Voila, underwater city!
10. ## underwatter city

As another data point, I just looked up the recently famous Costa Concordia (cruise ship for those that haven't been watching the news in recent months). Crew + Passengers is a bit under 5,000. Cost to manufacture was $570M. One thing to keep in mind though is that as a cruise ship, it doesn't have working spaces for most of those people. They're passengers just kickin' it. For a city, you need room for industry as well. I figure you'll need to (at least) double the volume per person to give everyone a place for their job (whatever it may be). You'll also need to be about 60% more people to make your 8,000. Assuming similar costs per person.... You're talking about just shy of$2B. So using two different starting points, you're talking about somewhere between $2B and$25B. It should, however, be noted that the $2B number is certainly low as it does not account for any "special" construction as would be required to make an underwater city. A carrier has lots of specialized construction to make it a warship so I (lacking better data) just figured you could have a 1 for 1 conversion between "money spent to make her a warship" and "money spent to make her submarine." But the cruise ship has no such obvious fudge factor to account for increased construction complexity and the like. Thus, I would see the$2B as a basement. No way in hell are you making it for less.
11. ## underwatter city

That's the ONLY way I see it being feasible. Even then, I see it as prohibitively expensive (I stand by the $25B number for your city build on the surface and floated to the final site). A Nimitz class carrier costs about$4.5B and you're talking something that is on the order of 5X larger AND has to withstand being 400' under water for extensive periods of time (keep in mind, carriers get pulled out of the water periodically for maintenance thereby allowing anti-corrosion repairs and such that aren't likely to be available to a permanent city... You'll have to use 'better' tech up front and that co$t$.).
12. ## underwatter city

Out of curiousity... Exactly how much background do you have in marine systems and/or the engineering of LARGE systems? 'Cause for you to say it's all so very simple, you're either a genius or naive on a scale that boggles the imagination. Ever watch somebody align a large fixture for welding? It can take *days* to get everything set up right before you can weld something BIG. And now you want to do it remotely, while fighting ocean currents, and in an environment where simply measuring things to make sure you have the aligned correctly is non-trivial? And if you screw any of it up, people are likely to die at some point in the future? And you think this will be easy?
13. ## underwatter city

Dream on. A submersible capable of doing any sort of heavy construction is not going to be cheap, easy, or simple. Look at the money that goes into remote submersibles now and all they generally do is take pictures.
14. ## underwatter city

Well, consider that an aircraft carrier has a crew that's just under 6,000. So you're talking about 25% larger than an aircraft carrier to live in absolutely deplorable conditions. Want population densities that aren't best described as inhumane, then you're going to want at least 4-5 times that size. So... Call it 4.5 * 1.25 = 5.6X the size of a Nimitz class aircraft carrier. While you wouldn't have fancy weapons, you would have all sorts of fancy construction requirements so lacking better data, I'll guess that the cost per person would be comparable... So for about $25B you could build your city. *IF* you were building your city in a shipyard and then sinking it. If, on the other hand, you have visions of building it on site? I'd bet you're talking$100B.
15. ## underwatter city

Not enough data. How self sufficient must the city be? Can they bring in food from an outside source? Electricity? What are the logistical ground rules? How many people are required? Clearly nobody calls a modern nuclear submarine an underwater city so you're obviously looking at more than the hundred or so that crew a boomer, but how many? And what is their motivation for living there? Are we talking about an underwater mining colony where life sucks, but people endure because pay is awesome or are we talking about a resort where life is amazing and people pay great sums to be there? Aside: My own "mine colony" comment made me realize that such a "city" might make an EXCELLENT prison. Don't bother trying to tunnel out, boys....
16. ## subs without nuclear.

Thunder storms make transportation difficult at airports today. Blizzards make driving impossible. In the history of man there has never been a transportation system that wasn't at the mercy of Mother Nature. Why does this one have to be any different? And yet, somehow James Cameron managed to go 7 miles down without a nuclear reactor. Baring a reactor, you'll have to do the majority of your traveling on the surface. But so what? As Mr. Cameron proved, it's NOT a big deal. WWII proved the utility of a submarine that spends the majority of it's time on or very near the surface. There really is no reason to stay deep. I mean, you act like it's a big deal to go up/down a whopping 400 feet when you're also talking about traveling 200 *miles*. Airplanes go up/down more than that on shorter trips and they don't even have the advantage of simple ballast tanks. In other words... You're fishing for some sort of Buck Rogers type answer that will sound all cool and such. I get that. The problem is that you're trying to come up with a $50 solution to a$5 problem.
17. ## subs without nuclear.

Why would it be any more difficult than riding an elevator? We have skyscrapers that are a LOT taller than the 400' maximum depth for your planned cities. We have submarines that are longer than 400' as well. Conceptually, start with a submarine. Hollow it out. Stand it on end. Put an elevator in it. Have a door at the top that goes to some sort of dock for boats. Have a door at the bottom that goes to your city. Voila, you can travel from the surface to your city without getting wet in nothing more than a couple minutes.... Just like you can get to the 40th floor of any modern skyscraper in a couple of minutes. So your glorified elevator is the first thing you build. Build it like a ship. Float it to your desired location. Sink one end of it so it stands upright. Done. There are many, many problems associated with having a city under water. Transportation is not one of them. In fact, it's trivial.
18. ## subs without nuclear.

Why do you have to travel underwater? Just because your city is underwater doesn't mean you can't base your transportation system on the surface. I mean, last time I checked I live on land but think nothing of flying through the air to get to another location. Why couldn't your transportation system merely include a glorified elevator that gets you too/from the surface whereupon you take a plain ol' boat to [other location]?
19. ## Bearings for home-built gyroscope?

You don't say what your intended application is but... An air bearing might be fun to build.
20. ## Air Gear (aka: electrical powered inline skates)

If you pull this off, let the Nobel Prize folks know, because you'll be sure to win the prize in Physics. You can't use an electric motor to drive any sort of generator to recharge the batteries that you're using to drive the motor. In the vernacular, that's a "perpetual motion" machine. In geek speak, it's a violation of the 2nd Law of Thermodynamics.
21. ## How Would You Brand a Planet

I'd say "Screw the Prime Directive," and seed it with life.... A cluster bomb chock full of micro organisms known for being able to survive in all sorts of odd environments. Then I'd sit back and watch O2 levels.
22. ## Boiler Pressure

Not without knowing your power source, thermal transfer coefficients, surface area, and other details. With a small oriface you could (in theory) generate an arbitarily small amount of steam or you could boil the whole damned lot in a second. Tweak one variable and everything changes.
23. ## Boiler Pressure

Not enough information to answer your questions. At 800 F you should be above the critical temperature for water so you'll have dry steam regardless of pressure. You can have pretty much whatever pressure you want. However, that's somewhat meaningless without knowing other details. How much energy are you putting into the system? Is it to be throttleable? What is your desired mass flow of steam? Not enough information to answer your questions. At 800 F you should be above the critical temperature for water so you'll have dry steam regardless of pressure. You can have pretty much whatever pressure you want. However, that's somewhat meaningless without knowing other details. How much energy are you putting into the system? Is it to be throttleable? What is your desired mass flow of steam? Not enough information to answer your questions. At 800 F you should be above the critical temperature for water so you'll have dry steam regardless of pressure. You can have pretty much whatever pressure you want. However, that's somewhat meaningless without knowing other details. How much energy are you putting into the system? Is it to be throttleable? What is your desired mass flow of steam?
24. ## The Aerodynamic Centre

Who ever said it doesn't? Thought experiment: 90 degree angle of attack.
25. ## Stainless Steel Spring

On the control valves I have experience with, not even the diaphragm comes in contact with the fluid. As for what I would use... Honestly, I've not designed a control valve (I just use 'em) so I'm not going to be able to name an alloy. I'd just use whatever material gave you the spring constant you're looking for at the lowest cost. Heck, you should be able to buy off the shelf springs! I'm just asking because your requirements don't seem to make sense to me.
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