Why does an orbit increase in altitude with more velocity?

[Evanitis]

13 hours ago, Fez said:

I understand the concept, unfortunately I can't seem to visualize it in my head, which is really frustrating

Don't worry about it. It's... not complicated, but really doesn't feel 'right' for the common sense. Fortunately, you already have the perfect tool what will eventually make you understand what's happening: KSP. It helps more than any explanation we can give. Let me quote mr. Munroe:

[mikegarrison]

15 minutes ago, Fez said:

I think I got it, as you increase horizontal speed, the craft goes forward horizontally a little bit more, while falling down at the same rate, so the trajectory begins to flatten, and you climb. Then, as you slow down, your horizontal speed decreases and you're still falling at the same rate, so the trajectory curves more towards the thing you're orbiting. Does that make sense? BTW, thanks for all your patience guys, I appreciate it

That is a physical way to imagine it, yes.

[Kerbart]

6 minutes ago, mikegarrison said:

Sorry, this is actually mostly wrong. The pull of gravity does get *very slightly* weaker, but not so much that it makes any difference. It's all because you are converting speed energy (1/2*V^2) into height energy (g*H). "g" is actually staying almost the same. It's "H" that is changing.

Not sure what V^2 stands for. Do you mean v²?

[mikegarrison]

1 minute ago, Kerbart said:

Not sure what V^2 stands for. Do you mean v²?

Same thing. It's old skool for writing equations without superscript fonts.

[Camacha]

14 minutes ago, mikegarrison said:

Not really. Speed goes up where you add the energy, just like you would expect. But when you trade it for height at the other side of the orbit, it goes down because height is being traded for the square of speed.

The confusing part is when you are dealing with two circular orbits at different heights. One has more energy than the other, but also slower speeds.

I mean, I get it, but it is a bit counter intuitive.

[Fez]

Well actually, I suppose both orbits have the same energy, since the higher one is slower, so it has lower kinetic energy, but more potential energy

Correct me if I'm wrong

[Evanitis]

Just now, Camacha said:

The confusing part is when you are dealing with two circular orbits at different heights. One has more energy than the other, but also slower speeds.

I mean, I get it, but it is a bit counter intuitive.

Dunno, that's the part where my common sense is satisfied. The higher enregy orbit is longer, so it takes more time to... go 'round it. I'm pretty sure that's not exactly how it works, but 'seems' logical.

[0111narwhalz]

That sounds about right. I think you're getting the hang of it.

[mikegarrison]

2 minutes ago, Fez said:

Well actually, I suppose both orbits have the same energy, since the higher one is slower, so it has lower kinetic energy, but more potential energy

Correct me if I'm wrong

Nope. The higher (and slower) one has more energy. There are physical ways to visualize this, but the simplest way to verify it is that to get from the lower orbit to the higher orbit you need two burns, both of them adding energy (prograde).

[Camacha]

4 minutes ago, Evanitis said:

Dunno, that's the part where my common sense is satisfied. The higher enregy orbit is longer, so it takes more time to... go 'round it. I'm pretty sure that's not exactly how it works, but 'seems' logical.

Yes, it is longer. The problem is that it is also slower. Not just slower to go around once, but the speed is actually lower.

[Fez]

So the higher orbit has more total energy? I thought that since its higher and slower, it has less kinetic energy, but more potential energy

[mikegarrison]

8 minutes ago, Fez said:

So the higher orbit has more total energy? I thought that since its higher and slower, it has less kinetic energy, but more potential energy

Those are all true. It has less kinetic energy, more potential energy, and more total energy (assuming the same mass).

[Fez]

That's weird, where did the extra energy come from then?

[Camacha]

28 minutes ago, Fez said:

That's weird, where did the extra energy come from then?

From the prograde burn.

[Fez]

Hey quick question, would you guys agree with this websites explanation of orbits: http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-causes-an-orbit.html

Or this one: http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-orbit-58.html

They both say orbits are caused by gravity pullling the craft in, but momentum "pushing" it out, becuase it wants to go in a straight line

Edited January 26, 2016 by Fez

[Camacha]

56 minutes ago, Fez said:

Hey quick question, would you guys agree with this websites explanation of orbits: http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-causes-an-orbit.html

Or this one: http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-orbit-58.html

They both say orbits are caused by gravity pullling the craft in, but momentum "pushing" it out, becuase it wants to go in a straight line

I took a quick look, but it seems to be how it works.

[Fez]

Also, I just thought, why does the craft necessarily have to trade kinetic energy for potential energy?

[GeneralVeers]

Occam says something about simplicity.

When you throw a brick straight up, why does it take longer to come back down if you throw it with higher velocity? Same thing. A spacecraft is, for all intents and purposes, a very expensive brick that got thrown upwards really hard.

[mikegarrison]

9 minutes ago, Fez said:

Also, I just thought, why does the craft necessarily have to trade kinetic energy for potential energy?

Because energy is conserved. If you want to know why energy is conserved, you need to worry about 17-dimensional strings or Higgs bosuns or some crazy things like that.

[Fez]

Wouldn't energy be conserved if, when you add kinetic energy, it just stays in a circular, faster orbit?  Why does it have to climb?

[mikegarrison]

1 minute ago, Fez said:

Wouldn't energy be conserved if, when you add kinetic energy, it just stays in a circular, faster orbit?  Why does it have to climb?

What would keep it there if it's moving faster?

[Fez]

You mean in the circular orbit? gravity

[mikegarrison]

1 minute ago, Fez said:

You mean in the circular orbit? gravity

Why does it take an orbital velocity of 2000ish m/s to orbit Kerbin at 100km but it only takes about 200 m/s to orbit Minmus at 100km?

[Fez]

It has something to do with the fact that there's less gravitational pull, but i'm not sure specifically.  If anything, the answer to that question is what i'm looking for

[mikegarrison]

Just now, Fez said:

It has something to do with the fact that there's less gravitational pull, but i'm not sure specifically.  If anything, the answer to that question is what i'm looking for

Yes, there is less gravity. So for the same speed, you bend less. So your orbit goes higher.

Now turn that around and ask if you have the same gravity but more speed, so you bend less, then what would you expect to happen?