Basic orbit plane correction?

[Daid]

I\'ve only found out about Kerbal and it\'s amazing space program a few days ago. And I only found out that the 0.13.2 free download is actually the demo yesterday, so now I have the full 0.15 version it all it\'s glory

But I\'m having some difficulty, I can get a rocket into space. And I managed to crash into the Mun yesterday, leaving my 2nd stage in orbit of the moon (yes, my universe is filling itself with junk already). However I\'m having troubles getting my rocket from the planet into the orbit I want. When I lift off my rocket is almost impossible to steer and the orbit plane I end up with is a bit random. I\'ve managed to get orbits that are at a 90deg offset compared to the Mun orbit.

So I\'m wondering 2 things:

* How would I improve my initial orbit plane?

* What kind of burn do you need at which time to change your orbit plane?

[rasheed]

Wait until you cross the equator then burn east. Also when your trying to go east burn at 90 heading.

[Endeavour]

Well the only way to improve the initial orbit you get is to practice a bit and try to keep flying at 90 degrees. Once in orbit, plane changes are pretty confusing.

To change your plane, burn somewhere out of the line that prograde and retrograde make around the circle. If you go at 90 degrees, you will notice that the plane moves up or down in from of you. So just wait until the time is right, and burn away. Then you\'ll probably have to fix your orbit.

[Vanamonde]

almost impossible to steer

All you need to get a tidy orbit is to keep your nose pointed at 90 (east) on the navball, so maybe steering is the problem rather than navigation? What kinds of fins, gimballed engines, and SAS are you using?

[Daid]

All you need to get a tidy orbit is to keep your nose pointed at 90 (east) on the navball, so maybe steering is the problem rather than navigation? What kinds of fins, gimballed engines, and SAS are you using?

My MK3 (which actually made it to the moon). Has in the first stage, 8 engines with 3 tanks each. 2 tanks with 1 engine in the 2nd stage. And 1 tank with 1 engine in the last stage. And the only thing keeping it stable is an A-SAS.

I just put 8 SAS units on top of my first stage, and then I can keep it stable. But it remains a heavy beast.

[Vanamonde]

I\'ve never been clear whether multiple SAS modules actually do anything more than one does by itself, but it is my understanding that they need to work through fins, canards, RCS, and/or gimballed engines to really have much affect. So if you use some of those steering devices, you might not need all the weight of those additional SAS units.

[Bluejayek]

Vana: As far as I know multiple SAS units do nothing, as do multiple ASAS units. You are better off with a single ASAS and a few RCS thrusters then all that SAS weight. Try replacing all the SAS\'s with rcs tanks, and sprinkle some symetrized RCS thrusters around the craft and see how you do.

Also, if you hit caps lock, you go into \'precision mode\' where each time you hit a flight control (left right etc.) you move only a little bit at first, making it easier to steer, especially tiny craft.

[ToadDude]

Vana: As far as I know multiple SAS units do nothing, as do multiple ASAS units. You are better off with a single ASAS and a few RCS thrusters then all that SAS weight. Try replacing all the SAS\'s with rcs tanks, and sprinkle some symetrized RCS thrusters around the craft and see how you do.

Also, if you hit caps lock, you go into \'precision mode\' where each time you hit a flight control (left right etc.) you move only a little bit at first, making it easier to steer, especially tiny craft.

Actually, the SAS\'s effect is stacked, so if you use more it will be more effective. The ASAS, however, doesn\'t stack.

[Daid]

Actually, the SAS\'s effect is stacked, so if you use more it will be more effective. The ASAS, however, doesn\'t stack.

Indeed, this is explained in the tutorial

My initial orbit plane is much more stable now. Now to seek (or build) a plugin that gives me some more data without giving me an auto pilot. (Apoapsis and periapasis on normal view would be useful)

[rkman]

Now to seek (or build) a plugin that gives me some more data without giving me an auto pilot. (Apoapsis and periapasis on normal view would be useful)

I\'d suggest to use Mechjeb, and just not use its autopilot functions but only 'orbital information' and 'surface information'.

In reply to the rest if this thread:

Even a large rocket does not need many SAS or RCS, if it\'s a good stable design. During ascent a few gimbal engines are more effective to keep the craft on course, because those engines also provide thrust which SAS and RCS do not.

Most of my large rockets have ony one or two SAS, no RCS, sometimes a few winglets on the 1st stage. Always a few gimbal engines (to many gimbal makes the rocket unstable).

For small and medium size rockets the commandpod\'s build-in SAS is usually enough to keep the rocket stable, so it only needs an ASAS (or Mechjeb plugin).

For attitude control in space while no enigines are burning, SAS and RCS are the only way.

Although 'moar' is a very Kerbal approach to rocketry, less is sometimes better.

[Daid]

I actually managed to get 2 ships withing 1.5km of each other, stable. All manually, with only some extra information shown (Ap,Ep of myself, and the ship I\'m trying to get in line with). And no RCS, and only and ASAS. And my ships just passed each other at 300m. Fun stuff.

Would be cool to have some type of refueling station available...

[wildkittyv1]

Pardon the long post, but I try to do a bit of explaining and go into a few details you didn\'t ask for, but which I think will be quite helpful.

There\'s pretty much 4 places you need to burn your rockets when you get into orbit in order to give yourself -whatever- orbit you want. I\'ve been spending more time just floating around and working with the gyroscope/artificial horizon and have come across some pretty effective/efficient ways to manipulate my path. These might not be the best ways, but they work. I\'m no pro at the game, but I can reliably get ships to do what I want them to and have just picked the game back up yesterday afternoon after putting it down for a week or so to come back with a fresh mind, so I\'ll explain how I\'d want it explained to me. The first thing you need to know are some things about the gyroscope and what all the directions mean.

The spinning blue and orange ball represents where the nose of your ship is pointed in relation to the body whose gravity you are currently affected by/which body you\'re orbiting. If you\'ve ever been affected by ('encountered') the Mun and watched the ship as soon as it hits the encounter point, you will see the gyroscope snap to the new body of gravity as you get caught by the Mun.

----------

Blue is sky/space - 'Out' - pointing away from the planet; this is why you are pointed directly 'up' at the middle of the blue on the launchpad

Orange is ground - 'In' - pointing directly at the bottom of the navball has your nose aimed at the ground of the body\'s gravity

Any easy way to test out the directions listed below is to take a nice and light rocket, something easy, get it about 50k up and just muck about with the ball until you\'re comfortable reading it and do not have to refer to the 'normal' screen (not the orbital map) to be sure you are oriented correctly.

----------

0 Degrees - 'North'

90 Degrees - 'East'

180 Degrees - 'South'

270 Degrees - 'West'

This was the weirdest bit for me to understand when I tried to figure out the gyroscope. If you want to think of the plane being a circle, then 0/360 Degree is 'North', and I use quotes because it\'s difficult to really call any direction North in space. Arbitrarily, though, that\'s where 'Up' is, whereas pointing at the center of the blue half of the ball would be 'Out' and the center of orange would be 'In'.

So with that out of the way, here\'s how you\'re going to orient your ship.

----------

When you launch, you\'re pointing Out. Your main goal is to shoot as straight out as possible without veering, and you accomplish this with ASAS, SAS, control/stabilization fins, symmetry, struts, and other sorts of stability-increasing parts. I\'m going to assume you can get your ship to launch straight. We\'re going to ignore trying to optimize fuel with when you begin your turn and just concentrate on the kinds of turns you can make. Generally, when trying to either achieve orbit around Kerbin or another body, people point their ships East (90) or West (270), both directions have their pros and cons, but that doesn\'t matter for this. You want to generally continue flying 'Out' until you are happy with your Kerbin Apoapsis on the orbital map. If your orbital pattern is skewed at this point (achieving distance), it doesn\'t matter much since we\'re going to flatten our orbit a bit later.

Once you get about halfway to the Kerbin Apoapsis (it should still be a sharp ellipse that will bring you back to Kerbin at this point), you need to figure out if you\'re going to be pointing North or South to flatten out your orbit. If your plath has you coming back in the northern hemisphere, then you need to adjust it southward; if it\'s bringing you south, then northward. You simply point in the opposite direction. Now, you\'re not going to be able to get it perfectly 'flat' here, but your goal is to get as flat as possible without wasting fuel.

Once you\'re relatively flat, continue on to the apoapsis as you normally would before making your orbital burn. If you want to orbit WITH the direction of Kerbin\'s rotation (counter-clockwise looking at Kerbin\'s north pole), you are going to burn East, or at 90 degrees; if you want to orbit against it (clockwise looking at the north pole), burn West at 270 degrees.

Perform your orbital burn until your desired orbital distances are achieved.

Now, your orbit can be off 'flatness' by even 45 degrees and you\'re still in decent shape, and here\'s where the fine-tuning will come into play and understanding the gyroscope.

What you want to do is look at the orbital map and zoom out so you can see all of the Mun\'s orbit at once and line up both sides so they form a flat line. On the orbital map screen, this is the easiest/best/only way you can create an artificial flat plane, and is what you are going to be using to know when you make your adjustments. Your goal with the first 'North/South' adjustment is to get as close to flat as possible to make this easiest and less costly in fuel.

When you have the Mun\'s orbit lined up as a single line, you are looking for the point where your path crosses the artificial flat plane you created, even if you\'re not going out that far - it\'s simply a guide. The point where these two lines cross is where you\'re going to be adjusting your orbit\'s 'flatness', and the further from Kerbin you are, the less gravity there is, so less fuel will be consumed while adjusting. Why are you using this point? Well, when you cross that intersection you are 'on' the flat orbital plane, so it\'s a pretty good time to adjust.

Regardless of the direction you\'re traveling, the mechanics are the same. If your orbit is skewed and bringing you 'North' for this trip between your apoapsis/periapsis, then you want to aim your ship 'South' when you cross the horizon and burn. You will see the plane begin to flatten out if you\'re doing this on your orbital map (hence why it\'s important to be able to read the gyroscope and know what you\'re looking at). The point of intersection with the flat plane will slightly change, but you can bring it about 75% of the way to flat without wasting much fuel. Fast-forward time again and cross the plane, then continue to re-flatten. It might seem as though it\'s costing more fuel to flatten out, and at that point it might be better to wait until you\'re on the opposite side of the body you\'re orbiting to flatten the rest out.

You\'ll have to play with and learn for yourself the optimal points to flatten out, as this is just a general point and guide of what to do that works for me concerning both mechanics and fuel efficiency. When your orbital path has you skewed going 'North', you just do the opposite and burn 'South'/180 degrees).

When it comes to controlling orbital height, you\'re mostly relying on East/West directions. You want to burn with the direction you intend on traveling (we\'ll say East/90 for this) at the apoapsis to increase the orbital height/position of the periapsis, and you want to burn 'against' (270 in this example) it to decrease the periapsis. The easiest way to get a circular orbit is to burn from launch to the desired height and cut your engines until you get there unless you\'re fixing your 'flatness'. Once you get to the apoapsis, burn with your direction of travel until the periapsis matches (or is close to) the apoapsis\'s altitude. Same concept applies to increasing the apoapsis: burn with your direction while at the periapsis to increase it, burn against your direction to decrease it.

After half an orbit around Kerbin, you should be pretty 'flat', have a circular orbit (or an elliptical one if you\'re slingshotting), and be on target to your first encounter. If it takes you more than one periapsis encounter to gain the orbit you desire, then keep practicing and hammer down reading the gyroscope and how to adjust your orbit.

Sorry for the long post, but I wanted to explain things fully.

Hope it helps!

[Daid]

@wildkittyv1: Awesome. That should be in the 'beginners guide on orbiting'. Mind if I put it on the wiki? http://kspwiki.nexisonline.net/wiki/Tutorials

The first tutorial there directly goes into the math. Which is fine at some point, but a bit bad for a beginner.

[wildkittyv1]

@wildkittyv1: Awesome. That should be in the 'beginners guide on orbiting'. Mind if I put it on the wiki? http://kspwiki.nexisonline.net/wiki/Tutorials

The first tutorial there directly goes into the math. Which is fine at some point, but a bit bad for a beginner.

Well, I don\'t mind if it helps others, but if anything was going to go into the wiki I would prefer to clean it up with some editing, as I just kind of hammered it out quickly when I initially wrote it. Some images or illustrations to go along with it would be a good thing and pretty easy to do, I think. I\'m sure there\'s better ways to orbit and with less fuel, but the way I described is pretty efficient and just about any ship you build can at least get into orbit around the Mun using that so long as it can escape the atmosphere with about a whole liquid fuel tank left. I tried to be as simple as I could, but it\'s still a bit convoluted. Do what you want with it, but if people want me to clean it up or add some images I could throw something together, I guess.