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

I Orbits -- radial verses perpendicular orbits & energy

  1. Jul 17, 2017 #1


    User Avatar
    Gold Member

    Does anyone know where I can find information about how to calculate how much extra energy is required of a space ship to try to thrust perpendicular (or at some angle) to the orbital plane verses flying completely/only in the orbital plane when moving outwards in our solar system? If the space ship does thrust perpendicular to the orbital solar system plane, will the sun's gravity try to bring the ship back into the orbital plane?
  2. jcsd
  3. Jul 17, 2017 #2
    No, gravity is symmetrical in all directions. The only reason that it would be easier to travel along the orbital plane is because your launch point is also traveling along that plane so you already have some momentum. It's the same reason that all launches happen as close to the equator as possible and always go in the same direction that the earth is rotating.

    Once in orbit, you should not require any fuel no matter how you are oriented in regards to the solar system.

    The planets are all in a plane because they formed from a spinning blob of dust that formed the sun 4.6 billion years ago. The self-interaction of that gas cloud and spinning motion of it formed it into a disk. Much further out, objects orbit in all lots of different obits. The Oort cloud is theoretically spherical.
  4. Jul 17, 2017 #3


    User Avatar
    Gold Member

    Oh, I see. Just a check on my logic: Thus, if there was a satellite or comet orbiting at an oblique angle with respect to the orbital plane for some reason and no space gas, the satellite or comet should then stay in that orbit. Is this correct?
  5. Jul 17, 2017 #4
    For all practical purposes: yes. Once in orbit, it will stay there. There are some known comets that have orbits like that.

    If it's in the solar system, the gravity of Jupiter (and the rest of the planets to a less degree) will pull anything towards the plane of the planets, but it'd have to be out there for millions of years to be noticeable.
  6. Jul 17, 2017 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If by "orbital plane" you mean the Sun's equatorial plane, Then you should be made aware of the fact that none of the planets actually orbit exactly in that plane. Mercury orbits closest to this plane. The ecliptic, or the Earth's orbital plane, is tilted by some 7.25 degree to the Sun's equatorial plane. Relative to the ecliptic the other planets have inclinations that vary from 0.77 to 3.39 degrees (Pluto's orbit is at 17.15 degrees to the ecliptic.) The main body of the asteroid belt includes objects with as much as 30 degree inclinations.
  7. Jul 17, 2017 #6


    User Avatar
    Gold Member

    Okay, I got it. Thanks for your help everyone. I'm good to go now.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted