Posted: 6/12/2004 7:21:52 PM EDT
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If airships can stay aloft becuase theyre lighter then air, and a hydrogen ship can be larger then a helium ship becuase helium has twice the mass of Hydrogen... Would a ship with chambers filled with vaccum float via the same concept? If Helium weighs X * 2, Hydrogen Weighs X * 1, wouldnt vaccum weigh X * 0 ? And thus reduce the ships weight the most? |
Yes, however, there is a problem with greating a ship with a vacuum. The sidewalls for the ship would need to be very strong, and that means heavy. Also what if you get a small hole? On a He or H ship you would not get much leakage, and what you did louse can be trimmed out inflight by adding more He or H. Creating vacuums is difficult and probably could not be done on a aircraft due to weight restrictions. Good idea though! In regards to your physics, it is a question of density[mass or weight/volume]. Think of it in terms of a sailing ship, the space inside the ship can be considered a "vacuum" to the water. Even though it is full of air/cargo/stupid people/etc... The ship can only hold up as much weight as the water it displaces, soo, if there is an airship that displaces a given amount of air then that weight of air is the Maximum Gross Weight(weight of Everything) that the airship can lift. |
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If you had a perfect envelope to contain the vacuum, that is, one that's light enough and can resist implosion, it would most certainly work. A cubic meter of vaccum weighs NOTHING, while a cubic meter of ANY gas has SOME weight to it. Vacuum has ZERO density. People think of the gas in the balloon as applying an upward force, but this is wrong. What actually happens is that a lighter than air balloon is forced upward by the gases underneath the balloon. There IS no upward force applied by the gas in the balloon. It's the force of gases outside it pushing the balloon UPWARDS ad they go down past it. CJ |
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Thank you, so it seems like the real issue would be finding a material thats sturdy and light. See this just reinforces my belief that the only REAL advances in science are in materials science. Its easy enough to think up something, its finding materials to do it with thats the trick. |
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Actually I just graduated with a degree in tech business managment. I was just curious and I always have strange ideas like this. I don't think I'd ever actually try and do any of them... Although they did teach me in management school to find out the impossible... then ask an engineer to do it. |
Your teachers are the reason I quit bein smart and just started paintin guns. Serious. Some "out of box" ideas have merit, others, well, can be written off at a glance. However, when the manager insists you try, it kinda makes it not worthwhile to wake up. 
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I am in Engineering school Mechanical Specialty, and DILBERT IS A DOCUMENTARY! |
What he said. small exception Areospace Engineering |
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I have determined that Dilbert accurately depicts the business side of engineering with uncanny precision. And he's never far off the mark when it comes to the engineering side of it, either. The primary problem as pointed out by others is the envelope for the lifting volume. In a helium or hydrogen (or for that matter, hot air) lighter-than-air craft, some of the structural rigidity is provided by internal pressure. If you were to use a vacuum, the surface would be pressed on by atmospheric pressure with nothing inside to resist. All of the structural strength would have to come from the structure itself. Air at sea level has a pressure of about 15psi. Calculate the total force on a cylinder 100' long and 40' in diameter... Which is left as an exercise for the student.  And understand, the mass of the craft cannot be more than the mass of the displaced air, so calculate the mass of air at standard temperature and pressure for a cylinder of that same volume. Which is also left as an exercise for the student. 
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Dilbert is the epitome of employee vs. worthless manager, in all fields. Mostly directed at the IT industry, but can be applied most anywhere. The whole "he is a boss because he is too stupid and/or lazy to work" thing... |
Actually, Hydrogen has ¼ the mass of Helium. However, in the form that hydrogen takes, as a diatomic molecule, then it has twice the mass of helium. So diatomic hydrogen has ½ the weight per mole as compared to helium, but per atom the relationship is ¼. God I’m a picky bastard. Correction: Sorry,as others have pointed out, I transposed the mass (or weight) of Diatomic hydrogen and helium. It should read that helium has twice the mass of diatomic hydrgen and not the other way around. so... Hydrogen: 1 AMU Diatomic Hydrogen (H2): 2 AMU Helium: 4 AMU so... Hydrogen has 1/4 the mass of helium Diatomic Hydrogen has 1/2 the mass of helium |
 And to further clarify to Katana: Helium has an atomic mass of 4, not 2 (2 protons, 2 neutrons) Hydrogen has an atomic mass of 1 (1 proton, no neutrons) {Deuterium has an atomic mass of 2; one proton, one neutron, and Tritium has an atomic mass of 3; one proton, two neutrons.} |
Technically, you could say it's manufacturing. For example, we've known how to make steel since around the 1500s or so. But only within 100 years or so did we learn how to mass-produce steel in the quantities needed to make bridges and skyscrapers. We can make lots of fancy materials right now, the hard part is being able to mass-produce them and shape them the way we want. There's also manufacturing tolerances. What really makes the difference between an AR15 and a muzzle-loading musket is being able to hold tight manufacturing tolerances for complex shapes. |
Actually, since we're being picky bastards, Killbot has it right. All other things being equal, twice the weight => twice the mass, and 1H_2 does have about half the mass/mole of 4He.
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Ah, my bad; I thought the correction was mass->weight. |
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Let’s increase the picky level – actually all the stuff we have said is WRONG. The neutron is heaver that a proton, and since the hydrogen atom one proton, it will be LESS than ¼ the mass of a helium atom (which is two protons and the heaver two neutrons). Proton Mass: 1.6726 X 10^-27 Kg Neutron Mass: 1.6749 X 10^-27 Kg I believe this is a new low for ar15.com We are now nitpicking a 2.3 millionth, millionth, millionth, millionth of a kilogram! |
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Oh, and I made a boo boo on the mass and weight. I should have said mass, and NOT weight to be more accurate. I always use weight, since it has more of a practical everyday use, so its more of a force of habit and not a blatant ignorance. Mass refers to the mass of a core, where each nucleon is given a mass if 1 amu, whereas weight is the averaged naturally occurring isotopic masses. In the case of hydrogen, it has two naturally occurring isotopes, which are hydrogen (1 proton and 1 electron) and deuterium (1 proton, 1 neutron and 1 electron), which slightly changes the numbers (1 amu for atomic mass vs. 1.0079 g/mol for atomic weight). Oh, and hydrogen has the isotope of tritium (1 proton, 2 neutrons, and 1 electron), but its artificial and thus not included in the count of atomic weight – as far as I know. In the case of Helium, there is an isotope called helium 3, (FYI - I did a paper on it once and it has the potential to produce massive amount of energy and is a reason possibly for going to the moon to collect it). The atomic mass for Helium is 4 amu’s and the atomic weight is 4.0026 g/mol The difference is minor (1 vs. 1.0079 and 4 vs. 4.0026), but in the spirit of accuracy, I’ll say that I was wrong - don't beat me. |