Vanilla 1.1.9 is a product of Lussumo. More Information: Documentation, Community Support.

  1.  
    Still beggars the imagination. One hundred billion, just for trains.
  2.  
  3.  
    I understand the optimal refuelling problem, now. Well, mostly.
  4.  
    I had an idea. It's probably crap. But I will write about it anyway. It's either that, or figure out the bills I need to pay.

    Space cable! Hyperloop! Put them together and what do you have? Hyperspaceloopcablehyperthingie. Bad name. Anyway..I was wondering how it might work to descend from orbit in an evacuated tube. There'd be no terminal velocity, so you'd end up going really fast at the bottom. Assuming you kill 100% of the orbital velocity and drop vertically from the ISS height, which is about 400 Km up. Local gee isn't too different there, so to 1st order it's constant acceleration, and terminal velocity is about 2.8 Km/s (6300 mph). Problem is that the tube can't be constructed - for the same reason that the space elevator cannot be constructed down to the ground; it will fall apart under its own weight because we don't have suitable material strong enough.

    Well, I said it might be crap.

    Footnote: The space elevator can be build with Kevlar today down to a certain height above ground. This height can be reached with stacked space cables. These also use only Kevlar. Therefore we can climb into space right now with current materials.
    •  
      CommentAuthoralsetalokin
    • CommentTimeAug 18th 2013 edited
     
    Posted By: Andrew PalfreymanI understand the optimal refuelling problem, now. Well, mostly.


    So do I. War is bad for fuel economy, especially if it's in a different hemisphere. Stay at home, it wastes much less fuel. You could simply purchase the Malvinas from Argentina for half the cost of the Falklands war, probably.
  5.  
    I'm captivated by the beauty of the mathematics of the problem. But you knew that.
    •  
      CommentAuthormaryyugo
    • CommentTimeAug 18th 2013
     
    •  
      CommentAuthoralsetalokin
    • CommentTimeAug 18th 2013 edited
     
    Posted By: Andrew PalfreymanI'm captivated by the beauty of the mathematics of the problem. But you knew that.

    And you laughed when I asked the chicken-and-a-half question. OK, then, what about the jeweler's chain problem then?

    Here is one version of the problem:

    A lady had four pieces of gold chain. Each piece contained three links.
    She took the four pieces to a jeweler and asked him to join them together to make a bracelet,
    where all of the links were linked together.

    “I’ll have to charge you a dollar for each link I cut apart and weld together again,” the jeweler said.
    “Since I have to cut and weld four links, the job will cost you four dollars.”

    “Oh no it won’t,” said the lady (who was very good at puzzles).
    It is possible to beat that price.

    How?
  6.  
    Posted By: maryyugoSomething for Al:https://www.youtube.com/user/TheGulfstreamGirl

    Very nice indeed.
    •  
      CommentAuthormaryyugo
    • CommentTimeAug 18th 2013
     
    Posted By: alsetalokinVery nice indeed.
    Well videographed too.
  7.  
    Hand on the throttles all the way down the approach.

    Pilots doing the same might have saved the Asiana and UPS flights.
    •  
      CommentAuthorAngus
    • CommentTimeAug 18th 2013
     
    Posted By: Andrew PalfreymanI had an idea. It's probably crap. But I will write about it anyway. It's either that, or figure out the bills I need to pay.

    Space cable! Hyperloop! Put them together and what do you have? Hyperspaceloopcablehyperthingie. Bad name. Anyway..I was wondering how it might work to descend from orbit in an evacuated tube. There'd be no terminal velocity, so you'd end up goingreallyfast at the bottom. Assuming you kill 100% of the orbital velocity and drop vertically from the ISS height, which is about 400 Km up. Local gee isn't too different there, so to 1st order it's constant acceleration, and terminal velocity is about 2.8 Km/s (6300 mph). Problem is that the tube can't be constructed - for the same reason that the space elevator cannot be constructed down to the ground; it will fall apart under its own weight because we don't have suitable material strong enough.

    Well, I said it might be crap.

    Footnote: The space elevator can be build with Kevlar today down to a certain height above ground. This height can be reached with stacked space cables. These also use only Kevlar. Therefore we can climb into space right now with current materials.


    Nope. How are you going to match the orbital velocity at 400 km height to the surface speed of the earth by means of a solid tube? If it sticks up rigidly from the earth the top will be going neither at the orbital velocity nor at the ground speed. You will have lateral forces all the way down.

    Anyway, assuming you could build a tube to hold the pressure at the bottom, what holds the top up?
    •  
      CommentAuthorAngus
    • CommentTimeAug 18th 2013 edited
     
    You can join all four together with the first weld, and complete a loop on all of them with the second. That way you have a bracelet of two parallel strands linked at their ends . Good if you have a small wrist.
    •  
      CommentAuthoraber0der
    • CommentTimeAug 18th 2013 edited
     
    Posted By: alsetalokin
    How?



    000 000 000 000
    000 000 000 0 0 0
    0000000 000 0 0
    00000000000 0
    )00000000000(
  8.  
    Posted By: alsetalokinAnd you laughed when I asked the chicken-and-a-half question
    Wot?
  9.  
    Posted By: AngusYou can join all four together with the first weld, and complete a loop on all of them with the second. That way you have a bracelet of two parallel strands linked at their ends . Good if you have a small wrist.
    Or twice as big around with 3 welds, by splitting up the last step
  10.  
    Posted By: AngusAnyway, assuming you could build a tube to hold the pressure at the bottom, what holds the top up?
    The whole thing is silly. I don't know what it's for, even.
  11.  
    Posted By: aber0der
    Posted By: alsetalokin
    How?



    000 000 000 000
    000 000 000 0 0 0
    0000000 000 0 0
    00000000000 0
    )00000000000(

    A+
    •  
      CommentAuthorTrim
    • CommentTimeAug 19th 2013 edited
     
    ITP

    I see Andrew has already seen it.


    Is the Hyperloop transport system a mere pipe dream?

    http://www.itproportal.com/2013/08/15/is-the-hyperloop-transport-system-a-mere-pipe-dream/
    • CommentAuthorLakes
    • CommentTimeAug 19th 2013
     
    Pipe Dream! harrrr! :)