60,000 Miles up: Space elevator by 2035:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Sep 27, 2014.

  1. orcot Valued Senior Member

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    odd thing happend with quotes
     
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  3. paddoboy Valued Senior Member

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    Probably, but only by really insignificant amounts. Plus of course Earth's orbit is already slowing, due to lunar tidal gravitational effects, so much so, that a day on Earth will be equal to a lunar month, in about 3 billion years.
    We also take momentum from the planets with our space probes when we use "gravity assists".
     
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  5. billvon Valued Senior Member

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    No arguments there! It would be fantastically difficult.

    You still have a huge amount of mass. You'd get weathering from UV, icing from storms and damage from lighting, so you'd need a mechanism to repair it. Enough damaged ballonlets and down it comes. I also haven't seen how you're going to hoist that three million pound rocket up an inflatable structure. (Or even a million pounds, or even 100,000 which is a small rocket indeed.)

    That seems like a different approach, but one with a lot of promise. You could use the railgun approach from Earth and not have to deal with any sort of inflatable ultra-tall tower.
     
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  7. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    I envision the tower to be a bit more rigid. We already have half-mile-high sky-scrapers; and half-mile high towers. By having some rigidity (titanium-steel), but with lifting balloons along the length, the total overall weight would be reduced significantly. Gotta keep the balloons filled with helium, but very doable. This would make for a very strong, tall tower, capped with a launch platform/restaurant.

    And making the moon as the first stop, followed by a rail-launch to Mars, one could send a constant supply of goods and an occasional astronaut crew. We've already discussed one-way mission. It should probably be feasibe to do rail-launch on Mars, too, since the atmosphere is only 1% of Earth's. Launch to Phobos or Deimos; then rail-launch again back to Earth at much higher speed.
     
  8. Russ_Watters Not a Trump supporter... Valued Senior Member

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    26% for the 10% of the time it matters -- the rest of the time a normal rocket isn't in the atmosphere anyway.
    And if a billion of your friends come with you, it might pay for part of the project!
     
  9. Russ_Watters Not a Trump supporter... Valued Senior Member

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    That's a variant on a popular perpetual motion hoax: No, forces that only act internal to a system cannot alter its external motion. It'll wobble about its common center of gravity, but that center of gravity will just continue orbiting the sun normally.
     
  10. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Google tells me the Willis Tower has a mass of 220,000 tons. Why don't you calculate how much volume of ballons you'd need to make a dent in that weight.
     
  11. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member

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    Well, that's what I meant - wouldn't it introduce a wobble effect that would compound? Sort of like a washing machine with the load off-balance?
     
  12. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Sure, but what's a few inches of wobble versus the few thousand miles of wobble caused by the moon?
     
  13. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    "A 100-foot-diameter balloon can lift 33,000 pounds! Here is how you can figure out the lifting capacity of the helium in a spherical helium balloon" http://science.howstuffworks.com/helium2.htm

    That's at sea level, 16+ tons = 33,000 pounds of lift. Say the average lift is about 5 tons (less lift at higher elevation). So, along the 30,000 feet of length (6 miles), that would require about 40,000 balloons (100 X 100 X 100) to reduce such a weight to zero. One tied every foot. That would be a lot of bulk stretching outward about 1,000+ feet away from the central shaft (make the balloons roughly 1,000 X1,000 X 1 to rough-estimate the amount). Certainly do-able, if the tower is broad (wide) enough in diameter. But just cutting the weight in half would help. And I suspect that it doesn't have to be anywhere near as heavy as the Willis Tower (http://www.willistower.com/ ) which is designed to support heavy weight at each floor, with lots of office space, etc.

    So yes, I believe it could be engineered to support itself to a height of six miles, with helium structures surrounding it to lessen the load. I'll let you do the more precise calculations. I'll take the Helium-supply contract.
     
  14. billvon Valued Senior Member

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    I don't think the math works out there. If the tower has a small cross-section it doesn't have much volume for helium. If it has a large cross-section it has huge wind forces to deal with. So you need more steel, which means more helium for lift, which means a larger cross-section . . .

    Also keep in mind that above about a mile those balloons just aren't going to do much of anything - their lift goes down exponentially as you get higher. As an example - At 50,000 feet you get about .12 kg/m3 of lift from helium. A Falcon-9 weighs 500,000kg - so you will need 4 million cubic meters of helium just to compensate for the weight of the rocket, not even the structure or gasbag. That's a cube 160 meters on a side. You will need a massive, massive tower to resist the torque on that sort of structure - and they are not light.

    That makes little sense. It is far easier (takes less fuel) to get from low Earth orbit to the surface of Mars than it does to get to the surface of the Moon. It would be like going from New York to Boston by way of Indiana.
     
  15. orcot Valued Senior Member

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    would it be so odd?

    the empire state building generates abouth 85 million$ alone from people visiting it's obersvation deck (generating 40.1% and 40.5% of it's revenue) and they charge "only" 19$ Say you raise it to a 100$ (this would still be cheaper then a helicopter ride) and manage to attract more visitors, who knows.

    Also being able to launch from it makes you cheaper then your competitors generating more launches in general
    launching the weight of a rocket isn't easy but remember 90% of that weight is fuel that can be piped up sepperatly.

    I'm also not really supporting this.
    What I'm saying that this structure could more realisticly be build then a space elevator and even if we could build a space elevator we should attach it to this to avoid weathering the cable.

    I believe the ideal transport to space (ignoring the far fetched like wormholes, teleportation, etc) are:
    for earth: (single stage) spaceplane, Earth's main export will be people and food(meat) and trivia complex hardware) mayor hardware will still need rockets tough

    for Luna: get's mass drivers to send resources back up but needs rockets to send people back up But I actually believe no large groups will ever live on the moon most work will be done using teleoperating (drones) from earth with a delay time of only 3 seconds and earths inability to send bulk mass cheaply Luna will end up becoming Earths 8th continent. And most people visiting it will probably stay on earth and rent a avatar( humanoid drone). In the end we also end up with space planes or launch from a tower on top of Olympus 21 km avoce the average surface with 0.12% (earths) atmospheric pressure

    Mars depends on how we use it, will it be a second home with enviromental laws that exclude most mining or a Industrial hub? I'm guessing we will see a mix we still need actual rockets but mars only has 1% Earths atmosphere and at the top of Olympus it's only a fraction of that? I think we have a semi rail gun speeding up it's flanks (or pavonis because it's near the equator) and launching from this moving vehicle

    Asteroids get space elevators either tethered to the ground or attached to a moving train (reducing the length of the cable).

    Objects like Ceres and Vesta (in the asteroid belt) never get colonized but get mined from orbit.

    Venus needs to get to much work, so it's one way drones for now.

    Mercurius get's a mass driver for helium and energy related exports
     
  16. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Technically, yes.

    But you can stockpile material on the moon. Then, once everything is together, rail-gun it at much higher speed than you could from a rocket alone. In other words, you don't have to carry your fuel with you with the rail gun. You can get speeds far higher than from a rocket, simply by making a long rail-gun. And not having to carry your fuel, as in a rocket, means you are only accelerating the goods (astronauts, landing vehicle, food, etc.) and not the goods + fuel.

    Why don't you do some preliminary calculations, using a steady rail-gun acceleration at a human-tolerable 5 g for 5 miles. See what speed you get.
     
  17. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Good points. It won't be easy. I actually believe, though, that it is not as hard as you imagine. There are two primary forces in designing a tower - tension and compression. In steel-reinforced concrete, the compression is handled by the concrete, and the tension is handled by the steel. But that is not optimum methodology, but conventional methodology. Optimal, the tension could be handled by thin nano-tube fiber cables, lightweight, but very high tensile strength; and likewise, the compression load could be handled by light-weight materials such as epoxy. Thus, make struts with expoxied fibers, surrounding an oblong helium balloon. Use this as the structural component. Be careful it doesn't float away from you.
     
  18. billvon Valued Senior Member

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    You can stockpile material in orbit too - and it takes MUCH less fuel to get it there.
    But again, by just using the fuel you would have used to land the material on the Moon you could be on your way to Mars much, much faster.
    No, but you need energy. That's not free. So then you have to lift tons of nuclear reactors, solar panels or fuel cells to the Moon.
    About 900 meters per second - far less than escape velocity from the Moon. So your ship would crash back to the Moon after a short flight.

    I don't get this "let's go to the Moon and stop there before we go to Mars!" thing. It doesn't make any sense. (Unless you just want to go to the Moon. In that case, just go to the Moon.)
     
  19. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    solar panels are very light weight. so are nuclear reactors. that's why they were used for soviet satellites. storing up energy, then releasing it via a rail-gun is a far superior method. See next note as to why.
     
  20. billvon Valued Senior Member

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    The BES-5 reactor generated 2 kilowatts of power. The more advanced Topaz-II generated 5 kilowatts and lasts about 3 years. It weighs 2400 pounds.

    How many Topaz-II reactors would you need to power your railgun? (And if you intend to store power in batteries - how many batteries would you need and how much would they weigh?)
     
  21. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Moon escape velocity is 2,380 m/s https://answers.yahoo.com/question/index?qid=20080307000549AAJOozU

    So accelerate for a longer distance or higher g. Assuming your calculation is correct.
     
  22. billvon Valued Senior Member

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    Right.

    Or, instead of launching all those reactors, linear accelerators, solar panels, fuel tanks, landing pads etc to the Moon, just launch fuel to Earth orbit - and leave from there.

    Or, if you want to go to the Moon, leave from Earth orbit and return there. You could get from Earth orbit to the Moon and back with something slightly larger than the original LEM in two launches. The first launch, a Falcon Heavy, takes the lunar landing, ascent and return vehicle. The second launch, also a Falcon Heavy, takes a Dragon and a departure stage. They rendezvous, use the departure stage to break Earth orbit, then land. They do their thing, take off in the ascent stage, rendezvous with the Dragon they left in Earth orbit, and re-enter. You even get to reuse six first stages and the Dragon.
     
  23. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    the problem with using propellant that you take with you is that you don't end up going fast enough top make the trip to mars in a comfortable time.

    while it might take a much longer rail launch (say, 50 miles at 7 g), you can get quite the speed, I believe. This would have to take into account the curvature of the moon, and might take some engineering, but it should be too bad.
     

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