I think i finally get it,, maybe

[Lheim]

OP, sorry - the question is a little fuzzily phrased.

Okay, noobed up:

Planets (and little space ships orbiting planets) don't act like above. Objects further out move WAY slower and take way longer to make a complete orbit.

Just a quick reference: Earth is one AU from the sun, and takes one year to orbit it, with an orbital velocity of 29.8 km/s. Pluto is 40 AU out, and it's orbit takes 248 years, with an orbital velocity of 4.6 km/s.

Edited June 22, 2014 by Lheim

[peadar1987]

OP here,, can someone not noob it up for me??,, just want the basics,,, yet it seems like I opened a huge can of worms. ughh. I see all these people back and forth with each other on who's right and who's wrong. None of it answers me question. I would like to know the answer to my OP but I think its best to close this thread as I have seen too much head butting over it. ANY MOD PLEASE CLOSE THIS AT THE REQUEST OF THE OP. thank you.

I only wanted to learn, not cause conflict. Thank you all that posted. I read and somewhat learned in me limited way (why I asked for simple terms). TY again. but I cannot see a thread going on causing this much conflict. goodnight.

Hopefully in before the lock.

So immagine you're spinning something around on the end of a piece of string. The faster you spin it, the more it pulls outwards.

This is basically how orbits work. You have the gravity of the earth pulling inwards, and the speed of the satellite pulling outwards. If you want to overcome gravity, and get into a stable orbit, all you have to do is go fast enough so that your "pulling outwards force" is the same as the gravitational force.

Gravity is weaker the further away from the earth you are, so you don't need to go as fast to cancel it out.

If you go faster than this speed, the "pulling outwards force" is stronger than gravity, so your spacecraft will be able to pull away from the earth a little bit. However, this will make it slow down, reducing the "pulling outwards force", and letting gravity pull you in until your speed climbs again. This is why you get elliptical ("egg shaped") orbits.

Edit: Additional, extra credit info.

The force from gravity is proportional to the mass of the object you're orbiting, and the mass of your spacecraft (this makes sense, bigger objects have more gravity, and pull towards each other more strongly).

However, the acceleration of an object is the force divided by the mass, so the same force will have less of an effect on a heavier object.

These two effects cancel each other out, so no matter how heavy your satellite, it will always accelerate at the same rate (unless you also try to cancel out the gravitational force some other way, like moving really fast, using a rocket, or having air resistance). If it's a really heavy satellite, it will generate a lot of force, but it is heavy, so that force will do less. If it is a light satellite, it will generate less force, but that doesn't matter, because that little bit of force can give a lot more acceleration to a light satellite.

Edited June 22, 2014 by peadar1987

[GoSlash27]

Think of it in terms of those coin funnels your parents used to let you play with when you were little.

http://www.youtube.com/watch?v=B39ep3419ro

The gravitational force is lower with distance, which is represented by the slope of the funnel; nearly flat out at the edges and nearly vertical close in.

A coin travels very slowly when in a circular orbit far from the center, both in terms of angular velocity and vector velocity. It has very little kinetic energy but a lot of potential energy. It's reversed when the coin is in close to the center. Very high kinetic energy, but nearly depleted potential energy.

So indeed, a ship in a high orbit *does* have less velocity than a ship in low orbit. It's moving more slowly. But if you were to force it down to a periapsis matching the orbit of the "faster" ship in low orbit, you would find that the ship in high orbit would whiz right by the one in low orbit before returning to it's apoapsis because it has more energy.

Best,

-Slashy

[kidolvski]

v=(G*m_body)/r

G= 6,67*10^-11

r= the radius of the orbit

m= the mass of the body you're orbiting

v= speed in ms^-1

v_4r/v_r=((G*m_body)/r)/((G*m_body)/r)

Let's say G*m_body=1

v_4r/v_r=(1/4r)/(1/r)

v_4r/v_r=r/4r

Dividing this term by r gives:

v_4r/v_r=1/4

v_4r/v_r=1/2

So if the radius of the orbit is multiplied by 4, the orbital velocity is multiplied by 2.

[kidolvski]

If you go faster than this speed, the "pulling outwards force" is stronger than gravity, so your spacecraft will be able to pull away from the earth a little bit. However, this will make it slow down, reducing the "pulling outwards force", and letting gravity pull you in until your speed climbs again. This is why you get elliptical ("egg shaped") orbits.

There is no such thing as an outward pulling force in real life, as far as I know. Orbital velocity is a vector, it makes you move following the tangent on the point on the orbit where you are. The centripetal force, gravity in this case, "bends" that speed vector. It basicly makes sure you don't fly in a straight line, it "pulls you around the corner" like the rope attached to a ball you're swinging in circles makes sure it doesn't fly away in a straight line.

[Vanamonde]

Closed, by OP's request.