Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A huge Slingshot

  1. May 15, 2006 #1
    If you use the most suitable elastic material known today (in terms of elastic properties, the way it's applied and the manufacture of it), how huge (at least theoreticaly speaking) should sligshot be in order to be able to fire a projectile (a steel ball of any diameter you find suitable) so it exits the Earth's gravitic pull (end-up in space)?

    (now I imagine two tall buildings and some rubber hoses between them streached to the ground pointing upward...)
  2. jcsd
  3. May 15, 2006 #2


    User Avatar
    Science Advisor

    Until thinkers any velocity that could launch an object into a stable orbit. Not because there's no way to give sufficient thrust, but because of the angle involved. If you simply launch an object on a bolus to trajectory upward from the ground, that object's orbit will be an ellipse which passes through the same point from which was launched, and at the same angle. This would mean that your project that would have to come up through the ground.
  4. May 17, 2006 #3
    You watched the Mythbusters "Border Slingshot" episode, didn't you.
  5. May 17, 2006 #4
    Yes, a while ago. What does it have to do with slingshoting an object into orbit?
  6. May 17, 2006 #5
    Heh, this is interesting:

    ...I just wanted to know the THEORETICAL numbers for the good-old slingshot (i.e. how big and how elastic must it be to "take care" of the atmosphere-friction, gravity, type of material for the ball and all other parameters (also concerning geometrical aspect you've pointed-out)) that's all...
    Last edited: May 17, 2006
  7. May 19, 2006 #6


    User Avatar
    Science Advisor

    The whole point of my post was to show that there are no solutions come even theoretical ones, to that one aspect of the problem. You are quite right in seeing the other problems (of atmospheric friction, gravity, and the mass of the object being launched) as a simple question of numbers. These are all questions of how much force must be generated. However, no amount of additional force solves the geometry problem.

    Now, I'm off to look up some data on the elasticity of various materials, to see if I can find out what it would take to overcome the solvable parts of the problem.
  8. May 19, 2006 #7
    How about a series of nested slingshots, so that the payload of the first slingshot is itself a slingshot that only fires its projectile after it has reached a certain velocity? Upper stage slingshots could be tilted slightly to the direction of motion to solve the geometry problem.

    Otherwise, since the projectile can never travel faster than the elastic material, and I doubt that could even go supersonic, a single stage slingshot could never orbit anything.

    Sure, chemical rockets would be far more efficient, but a nested slingshot system would look cool, in a geeky Rube Goldberg kind of way.
  9. May 21, 2006 #8


    User Avatar
    Science Advisor

    i just have a question. how many degrees must the ball be shot to gain maximum lenght at ground level. like: if you shoot it 80 degrees it will go high, but not long. if you shoot it 10 degrees it will go fast forward a little while before it hitthe ground not so far away. what is the best degrees to shoot it?
  10. May 21, 2006 #9
    "Nesting" is possible, and is certainly used in accelerator designs. I once wondered whether it would be possible to launch a 1-ounce weight into orbit using some elaborate nesting technique with " a slingshot"

    I found that the accelerative potential is doubled while the force is reduced in HALF on each "nesting" stage. There are other designs, but the "doubling" is most useful in analysis.

    Anyway, through gross calculations, I found that in order to accelerate a 1-ounce projectile to 17,500 mph would require the initial stage of the "slingshot" to have a mass-volume equal to that of a very large home.

    Expensive, impratical, and could you imagine the internal heat generated! Likely, the primary stage(the size of a house) would severely disintegrate from internal heat during contraction.
  11. May 22, 2006 #10


    User Avatar

    NICE!! Even better, we could put a nuke in-between each of the nested slingshots, so expanding gas could propel the nested slingshots. :eek: Okay, maybe taking the far-fetchedness a bit too far. :blushing: o:)
  12. May 22, 2006 #11


    User Avatar
    Science Advisor

    Exactly 45o should give you your best results. This devides your thrust exactly "50-50" between gaining altitude and moving downrange.
  13. May 22, 2006 #12


    User Avatar
    Staff Emeritus
    Science Advisor

    The nukes are a lot more practical than the sling-shots :-). See for instance "project Orion".


    is one web reference among many.

    Of course, this would not be a very enviromentally friendly way to launch objects from the Earths' surface. But it's probably technically more feasible than a slingshot.
  14. May 23, 2006 #13
    Last edited: May 23, 2006
  15. May 23, 2006 #14
    Unfortunately, this page was marred by a vandal (a disadvantage to Wikipedia being completly open.)

    Action of the trebuchet.
    "Parag Vyas is actually the highlander, and in fact invented the trebuchet in the medieval era. Initially the projectiles used in the trebuchet were poopy popsicles, intended to confuse and disenfranchise an opposing army or fortress."

    - Bob Clark
  16. May 23, 2006 #15
    Why didn't you remove it? (I have done it now, don't worry; incidentally this is one of the advantages of Wikipedia being completely open).
  17. May 29, 2006 #16
    Principle of action and reaction (what would go further, a ball (forward) or a slingshot (backwards))?

    Why "geeky"? It's obvious that Rube Goldberg's "inventions" are just jokes and nothng more...
  18. May 29, 2006 #17
    My first thought exactly, but what about movement of the Earth?
    Heh... :smile:
  19. May 29, 2006 #18
    ...But it doesn't matter in space (you launch such space vehicle (or its parts) classicaly, and than employ the nuclear propilsion when in space).

    I think that it's the only realistic way to move around in the Space. (a huge amount of energy is stored in a relatively small package; excelent (and - it's the only type of fuel avaliable (simpliest achievable at least) in non-organic world))

    ...Is there another way at all? (having in mind that when you exit the solar system there's no energy from the Sun - you freeze like... nothing)

  20. Jun 27, 2006 #19
    It's easy to imagine an object with an aerodynamic shape which would sufficiently curve the trajectory. It would just take more energy.

    Another solution would be to fire it hard enough to swing it around the moon :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook