Back and forward orbit [around gravitating objects]

  1. As I figure [and have consulted with some physicists], there no reason why this would not work: object orbiting a planet in one direction, then, half way trough, hits something that propels it in the other direction [at orbital speed, of course], orbits the planet the other way around and hits something that propels it in the other direction again and then the cycle continues back and forward, keeping the object in orbit, but not in a full orbit, but, in this case, just orbiting, essentially, one side of the planet.

    Now, that (if) this works, there should be no reason why it has to be the whole half of a planet - it can be any distance at the orbits circumference. Even 100 meters. Right?

    Now the most interesting part.
    If we put this object a, say, evacuated tube with magnetic system to propel the object back and forward, provided that we deal with power issued and losing-orbit-while-accelerated problem[*] and more power to counter the "dead-weight" of the whole system[**] (magnetic fields actually would push the tube/ system of the object and stay on top of it) - would it [the tube/ system] just levitate relatively stationary somewhere around the path of what would be an orbit?

    [*] could this be dealt with just making the system a disk, "donut" or something like that while cutting down power consumption at the same time?

    [**] if the system is at high orbit where friction is no a problem and the whole system is separated in part, there would be, essentially, 3 parts - the object and two [maybe even one is enough] part that actually orbits the planet in opposite direction waiting to bounce at the object and there would be no "dead weight" . In a .. flying saucer scenario it is a bit more complicated as forces on the system accelerating the object somewhat cancels out (although there would be a time delay.. ).
  2. jcsd
  3. SteamKing

    SteamKing 10,942
    Staff Emeritus
    Science Advisor
    Homework Helper

    Your scenario may be possible, but all of this bouncing back and forth will probably greatly reduce the lifetime of such a planet.
  4. Drakkith

    Staff: Mentor

    Your scenario is...confusing. You want to bounce an object back and forth at orbital speeds. Well, for starters whatever your object is "bouncing" off of will need to stay in a stable orbit using thrusters or something since they will be transferring momentum to/from the object. And I don't really follow the "levitate stationary to the path of what would be an orbit" part.
  5. In the text I actually mentioned that it one way to picture the scenario is to use just three or two objects in orbit, that bounce off each other, synced so that each covers just part of the planet, same part all the time.
    Or use the united system where the object hits inside of a tube (or something ) and the tube stays relatively stationary because .. newton. - as the tube is accelerated opposite direction of the object, almost immediately, the object hits other end of the tube and is accelerated in the other direction.. again and again..
  6. Drakkith

    Staff: Mentor

    You MUST have something that will add energy to the object that is "bouncing" to counteract losses from each collision. This is in addition to having thrusters for stationkeeping of the other parts. If your object is moving at orbital velocity, as in stable orbit velocity, then in order for it to bounce off another object in it's path, that object must have something keeping it in orbit since it cannot be moving. (Otherwise how could your object hit it in the first place)
  7. Yes, I said that in the original text as well - energy will be introduced from whatever power source (dead weight of the system).
    No idea what are you talking about in the second part of your response.
    Did you read first post?

    In the "flying saucer" scenario thrusters would not be necessary as the dead weight of the system would hold against the object being accelerated.Energy is pumped in the orbiting object as required and the object is only pushed from the SIDES of the tube/ system (if it would not be a closed tube, each end would just fly of and make the other, simpler, scenario, where two or three parts orbit around a planet and hit each other periodically[***]) (at least in my theory, but you have not disproved it, yet, as it seems you did not get my point in the first place)
    [***]In the simpler version where object just orbits around and, in half way, hits another object (yes, yes - they have their power packs to keep the speeds sufficient), that is orbiting in the opposite direction ..
  8. Drakkith

    Staff: Mentor

    What does the "dead weight of the system" have to do with anything?

    Yes and it's very confusing. It may help to break your idea down further and describe what you're talking about on each step.

    I have no idea what your "flying saucer" scenario even means.

    Your "tube" would need to be traveling at orbital speed. If it is, how can you also have an object traveling at orbit speed inside it that's going to bounce around? If both the tube and the object are at orbital speed the object will never hit the end of the tube. If the tube is short enough and you don't care about maintaining the velocity of the object then you can ignore this however. Then you're just bouncing something around inside a tube. The problem is that you seem to want to keep your object at orbital velocity in both directions.

    You're saying like a giant ping pong paddle hitting an object in orbit? You realize that things in orbit travel at thousands of miles per hour right? Your object and whatever it hits is going to be obliterated.
  9. You say my tube would have to be flying at orbital speeds and how could the object inside travel at the same speed, yet, bounce around inside.. my answer to that:
    Look at it this way - the tube system at the beginning is spawned somewhere above the planet. In the same instant the object is accelerated and moves, say, to the right and the tube moves to the left with the object still inside. Depending on how long is the tube, for some time the object will be in orbit and the tube will be in orbit until collision within. At that point, the object is accelerated ( and compensated for losses) and the same happens as with the first acceleration, just in the opposite direction. Again both would be in orbit.
  10. You are missing the point.
    First, it is a thought experiment. [And what about the disk set-up I mentioned? It is under " [*] "
    second, the object can be anything with mass, even gas .. plasma.. charged particles - it is irrelevant.

    Dead weight of the system is anything that does not produce lift. It just sits there and is not directly levitating the whole thing (though it provides the power, acceleration)
  11. Drakkith

    Staff: Mentor

    After the first collision your object is now traveling the other direction at orbital velocity, but your tube has lost speed and would start to fall into a slightly different orbit depending on how much more massive it was compared to your object. It most definitely won't be heading the other direction though.

    A thought experiment still needs to make sense. You can't hand wave consequences away and expect to get a reasonable answer. And I can't make heads or tails of your first post and this disk shaped system. What exactly is shaped this way? At least label your components in some fashion so it's easier to understand.

    There will be no levitation here, I don't know where you got that idea from. There is also no lift produced, as your device is not flying through the atmosphere.
  12. Why? If the masses are consistend and whatever propels the object (and the tube, in that case) (like a magnetic field) provides the energy to sustain orbital speeds for both objects?

    The object, in stead of bouncing back and forward, would be a disk rotating. Or, to get a clearer picture, the same object in a string, rotating around the other end of the string, parallel to the ground (as parallel as it gets, because the ground is not flat and nor is the gravitational field - that is pretty much the whole idea behind all this. The secret to flying is to miss the ground. Objects in orbit really do that, im just trying to take it to the next level.). In this case other objects in orbit to bounce in would not be required at all.

    It does not have to be in atmosphere. Its more like a figure of speech. Not lift as in atmosphere, but.. pressure from the orbit .. something like that. I guess there is no term for that, I dont know. Sorry for the confusion.
    Last edited: Jan 20, 2013
  13. Trying to understand the point you're making - are you suggesting a levitating mechanism using magnetic fields?
  14. Drakkith

    Staff: Mentor

    Propels it? It's in orbit, nothing's propelling it. If you want to put a magnetic field around it then you're gonna have to have another object up in orbit to generate the field.

    The same object "in a string"? What? I'm sorry but I can't understand what this is supposed to look like at all. But I don't think it's really that important right now so I suggest we ignore it and not get bogged down on it.

    What were you thinking this pressure did?
  15. The tube has a magnetic field and propels/ pushes against the object. Hell, it can be a physical kick in the butt if the materials are ridiculously strong enough. (though, there should still be a magnetic field inside the tube to prevent the object impacting tubes sides and losing energy... if it is not superfluid that is being bounced in there. )
  16. Are you serious? : [​IMG]
  17. No. Just moving in orbit. Here, I will add a simple drawing:


    And here is the same picture with the tube around. The blue represents magnetic fields. As you can see, no magnetic field is pushing from beneath - just from the sides bouncing the object and from above holding the tube itself against the object being bounced [at orbital velocities]. :

    Last edited: Jan 20, 2013
  18. Drakkith

    Staff: Mentor

    Ok. And like I said, after the first collision, impact, whatever, your tube has now lost energy and is now falling into a different orbit. If the tube is small enough this will be negligible and the 2nd bounce will counteract it, so both the tube and the object inside simply stay in orbit around the Earth. What is the underlying point of all this? What are you trying to accomplish?
  19. .. that the tube-object system, as a whole, is not orbiting and is relatively stationary. 5 meters over your house, for example. All energy losses will be dealt with a power source..
    System can be made even more complicated [and better] with several layers vacuum tubes .. like an engine, really. It would be an engine.
  20. Ah! That's enlightening. Can you draw the forces on the "object" and the "tube", possibly in two separate figures (to avoid confusion)?
  21. Drakkith

    Staff: Mentor

    No, absolutely not. First, as I explained already, your tube is not going to be accelerated in the opposite direction enough to counteract it's greater mass. It will just end up slowing down and falling from orbit after the first collision until the 2nd collision accelerates back up again. The system as a whole would just stay in a normal orbit. Not stay stationary above the Earth.

    Second, you cannot accelerate anything instantly, which means it takes time for you to reverse the direction of the bouncing object, during which time your device will fall from orbit.

    Third, unless you are throwing miniscule amounts of matter around you're just going to annihilate your entire device when the object hits the tube.
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?