Help out a total n00b =)

[xclusiv8]

I\'ve been enjoying KSP for a couple of days now and i must say it is tickling my brain in places i didn\'t know i had up there I\'ve been practising my orbits but there is one thing i cannot master. If one is in orbit around the equator and another is perpendicular to it. How do i change the orbit of one of the ships so that i can make a rendezvous between them in the same orbit?

This is my current orbit. //Thank you!

[The_Duck]

This is called a 'plane change.' Each orbit defines a plane. You pass through the intersection of these two planes twice an orbit. When you pass through the intersection, thrust perpendicular to the plane of your own orbit (i.e., thrust parallel to the surface and perpendicular to your velocity) and your orbital plane will start to rotate. Watch the map view while you do this and you\'ll figure it out.

Note that it takes a very large amount of fuel to rotate the plane of your orbit by a large angle.

[Xivios]

What you are asking for is quite probably the most fuel-intensive manuever you can possibly do around a single orbiting body. Seriously, I think going to the Mün and back might require less fuel than a full 90 degree plane change.

But the quick and dirty of it is to burn at a right angle to you current orbit, example, if you are in a perfectly eastward orbit, you\'d burn north or sourth, and in a perfect polar orbit, east or west. This is called your orbit 'normal' and 'anti-normal', the normal being on the left of prograde and the anti-normal to the right. Exactly what normal you burn towards depends on which way you want to move the orbit, and this is made worse in that, as the orbit moves during the burn, so does the position of the normals, but we have exactly 0 normal markers on the navball (why Harv doesn\'t add them, I do not know), so once you start the burn, you\'re guessing until you re-check with the prograde or retrograde markers, which are the green circle and green X\'d out circle respectively on the navball, and move 90 degrees from that.

Now as to what will happen when you burn is pretty easy to visualize, as long as the orbit is roughly circular. Imagine the orbit as a ring, which isn\'t so hard because the map view displays it as such already.

Now imagine that ring is mounted to an axle, such that the axle passes through the center of the ring like a pair of opposing spokes on a wheel.

One end of the axle passes through your ship. The other end passes through the point on the exact opposite side of the ship.

Now up and down are kind of relative terms in space but visualize that one side of the ring is 'up' and the other side 'down'. And remember that all this time your ship is in orbit, the direction it is orbiting in is 'prograde' and the direction opposite its movement is 'retrograde' and so the imaginary spoke/axle is rotating like a wheel.

If you burn on the normal, the orbit will tilt on the axle such that the half the orbit that you are heading towards will move 'up' and the other half will move 'down'. And vice verse on the anti-normal.

For low and therefore fast orbits, it might be more fuel-efficient to burn into a very elliptical orbit, do the plane change at the apoapsis, where orbital velocity is low, and then burn back into a circular orbit at the desired altitude. The same concepts apply, but are a little harder to visualize, and you must place your apoapsis at the correct spot for the desired plane.

[togfox]

Welcome to the boards.

[Zephram Kerman]

so once you start the burn, you\'re guessing until you re-check with the prograde or retrograde markers

It\'s worth emphasizing that the normal moves during a plane change. Remember to keep following the normal throughout the maneuver. Otherwise, you end up with other vectors and an ellipse. Remember, everything you do affects something else.

Another method of plane change:

1) Cancel out all velocity vectors (land, or crash).

2) Build a new rocket and launch it on the correct heading.

[Zephram Kerman]

Oh yeah, don\'t forget McJeb!

So, if you\'re on the green line headed south, is that a burn along your 'orbit normal' vector?

If it is, that means you can use MechJeb to keep yourself aligned properly.

[Ydoow]

I\'ve tried it. It requires so much energy I couldn\'t even tell I was making an impact. I ended up making my orbit highly elliptical before realizing what was going on.

Having a highly elliptical orbit makes plan changes easy though

[Zephram Kerman]

I happened to be in this situation today. So got an image, just in case it helps someone visualize. In this case, I want to rendezvous with the launcher from my previous mission. So first I need to match planes, by burning south in a few minutes at the intersection. Once that\'s done, I can worry about lowering the orbit to catch up with the thing, and then raising it again once we\'re close.

[xclusiv8]

Thank you all for the warm welcoming =)

I\'ll try it all out when i come home today.

Edit: Just to be sure, i burn in between the highest point and the lowest point? I\'ll be going for an elliptical orbit to save fuel as some of you suggested and then burn in between those two points. Well that\'s my plan. It remains to be seen how it ends =)

[Ydoow]

Thank you all for the warm welcoming =)

I\'ll try it all out when i come home today.

Edit: Just to be sure, i burn in between the highest point and the lowest point? I\'ll be going for an elliptical orbit to save fuel as some of you suggested and then burn in between those two points. Well that\'s my plan. It remains to be seen how it ends =)

It probably won\'t end well lol

That\'s the kerbal way after all, all that matters is you learn a bit from each attempt.

Plane changes still kinda hurt my mind, but I like to think of a ring floating in space and imagining where I\'d have to press down to make it move

[MFToast]

I found VincentMcConnell\'s guide on plane changes very useful,

http://kerbalspaceprogram.com/forum/index.php?topic=9089.0

As well as his guide on orbital rendezvous,

http://kerbalspaceprogram.com/forum/index.php?topic=9060.0

They both explain the mechanics of it pretty well. Good luck!

[Thiel]

Having a higher orbit makes the manoeuvre much less fuel intensive. That\'s why it\'s easier to do it with an elliptical orbit. In many cases it\'s more fuel efficient to raise the orbit, perform the plane change and then lower the orbit back down again.

[Xivios]

Thank you all for the warm welcoming =)

I\'ll try it all out when i come home today.

Edit: Just to be sure, i burn in between the highest point and the lowest point? I\'ll be going for an elliptical orbit to save fuel as some of you suggested and then burn in between those two points. Well that\'s my plan. It remains to be seen how it ends =)

No, you don\'t. OK, you want to line up one orbit with another, put them both on the same plane right? There will be two points where the orbits cross. The altitude will be different, but they will cross. In fact the MunLander1 in you picture is pretty close to that point right now. That\'s a node. You want to burn at the node. To make it fuel efficient, make the node the apopsis of the elliptical orbit. Which means you\'ll want to burn prograde at the opposite node, which will move the periapsis to that node - where your ship currently is - and move the apoapsis to the opposite node. Then you\'ll want to burn at the correct normal at the first node - which is now your apoapsis. So, burn prograde at one node to create your elliptical orbit, burn normal/antinormal at the other node, which will be your apoapsis,to accomplish the plane change, then burn retrograde at the other node - the periapsis - to circularize the orbit again. At least that\'s the theory.