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How do I transfer to the new orbit established by the maneuver?


MetricKerbalist
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Hi KSP colleagues,

I have tried and tried to understand this, and  I have watched one YouTube after the next.  But I cannot figure this out.

I am in Kerbin's orbit.  I set up a maneuver that creates a new orbit.  But I cannot transfer my orbiting spacecraft onto the new orbit.  My spacecraft keeps bypassing the new orbit.

Could someone please tell me how I get onto the new orbit.

Thank you for your consideration.

Stanley

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I’m not sure that I fully understand your question, but I’ll give it a shot.

Setting up a maneuver node lets you plan what the effects of a burn will be.   However, you still need to manually complete the actual burn.   You do this by firing your engines when the ship reaches the maneuver node you set up, making sure it’s pointed the correct direction

For example, you are in low Kerbin orbit (~100km).   (Just kidding, I mean ~100 km..)  You plan a maneuver to reach Mun, so let’s say it calls for a prograde burn of about 850 m/s.   When your ship reaches the maneuver node, you point your ship prograde, and burn.   Eventually your actual path will very nearly match the projected path from the maneuver node.

Note that the burn times calculated in a maneuver node assume all energy will be expended at a single point in time, which is of course not possible.   The maneuver node assumes a burn duration of zero seconds, but in reality it may take you 10, 100, or 1,000 seconds, depending on your thrust to weight ratio.   So many players bracket their burns to have roughly half the burn occur before the maneuver node, and the rest (other half) occur after passing the node.

I apologize if I misunderstood your question.

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My last explanation didn’t make sense, even to me.   
 

Maneuver nodes are only a prediction of where your ship would go, if you performed the burn when you reach the node.  Until you actually perform the burn, your ship will continue on it’s original path.

Again, apologies if I am misunderstanding your question.

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Hi 18Watt,

Thank you for your reply.

So, first, using SAS, should I click on the Prograde button or the Maneuver button?

Second, I just set up a new maneuver.  Along the yellow arc on the right side of the Navball, it says 98.4 m/s and it also says "Burn Time: 2 s."  So what does that say to do?

Thank you.

Stanley

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Hi 18Watt,

It just doesn't work.  I am in low-Kerbin orbit.  I set a maneuver node using the prograde hand, thereby creating a rather elliptical orbit whose apoapsis extends much farther than does the original orbit.  I use SAS and I keep the ship pointed prograde.  I burn the fuel.  But the ship just follows the blue line.  I cannot get it to follow the dotted brown line that was created when I set up the maneuver.

Stanley

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You can either point the nose at the maneuver marker manually or use the maneuver SAS setting to do it for you. 

Then watch the timer. It will automatically count down to the moment of the ideal burn. But since an ideal burn is instantaneous whereas a real burn takes time, the timer will also helpfully split the actual burn half before and half after the ideal time, which is the next best thing. 98.4 is how many meters/second it will require to achieve the projected path, and 2 seconds how long to burn to achieve that. 

You will have to watch while the burn takes place and manually stop it when the burn has done what you want it to do. The instruments and icons are only informational. They do not perform the burn for you but only tell you what burn to make. 

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Hi Vanamonde,

Thank you for your help also.

OK.  Maybe now -- maybe -- I am getting it.  I am using SAS, and I keep pressing on the SAS button.  The spacecraft keeps jumping out of maneuver mode, and I have to constantly press and press again the maneuver button.

Moreover, how long do I have to keep burning fuel?  I am running out of fuel if I keep burning.  When do I know that the spacecraft has gotten onto the desired path?

Believe me, I really appreciate the help that you experienced KSP experts provide

Stanley

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Hi KSP colleagues (and especially at this time 18Watt and Vanamonde),

Good! I think that I now understand.

You have to actively set a maneuver burn and then stay with it until you see that the desired path has been attained.

I was thinking that the spacecraft would just automatically pick up the desired path.

You have been tremendously helpful.

I appreciate it very much.

Stanley

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23 minutes ago, MetricKerbalist said:

You have to actively set a maneuver burn and then stay with it until you see that the desired path has been attained.

Yes.

You are getting it.   Trust me, you are not the first person to bumble through orbital maneuvers.   Thanks to KSP, you are not even the millionth.   Some of it is not necessarily counter-intuitive, but is not always intuitive either.   I assure you, you will figure it out much sooner than you suspect.   
 

I would suggest not (initially) obsessing over being 100% precise in matching your actual path to the path your Maneuver Node calculated.   Get as close as you can, keeping in mind that you can correct any minor errors later- usually called a mid-course correction burn.

KSP has placed a very massive moon (Mun) orbiting Kerbin, much like our own real life system.   I suggest initially trying to intercept Mun’s SOI (Sphere Of Influence), because it is a relatively easy target to shoot for.   You have a very wide margin of error to reach Mun.   Once you have figured out KSP orbital maneuvers, you move on to smaller targets, which require more insight on your part to reach.  
 

Minmus is difficult, but not because it is slightly off-axis.   It is more difficult to reach because it’s SOI is much smaller, and requires more accuracy to successfully intercept.   Don’t expect extreme accuracy initially, that will come with practice.
 

Unfortunately, starting with Maneuver Nodes may be slightly counter-productive.   (You should still use them though).   I say that because by using them you tend to not see the immediate effects of orbital burns.   If you burn pro+grade or retro-grade, you intuitively know your orbit will either get smaller or bigger.   But what about burning Normal/Anti-Normal, or Radial-In/Radial-Out?   Adding those components shouldn’t affect your AP or PE, but it does.   
 

Maneuver nodes are an extremely useful tool to help you plan burns, burns that you may or may not actually make when you reach them.   Eventually using maneuver nodes will be essential for you to plan burns to reach other planets.   But initially you want to also think about what those planned burns are doing to your path.   
 

One of the most difficult maneuvers (for me anyway..) is Rendezvous and Docking with another craft.   Don’t start with that.  Start with observing the effects of burning Pro/Retro, Normal/Anti-Normal, and Radial-In/Radial-Out. Playing with maneuver nodes can help you visualize the effects, without actually burning any precious fuel.   If you want to actually change your path, then you do need to burn some fuel, but the Maneuver Nodes let you see the effects before you actually burn (or waste) fuel.

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Here’s another useful tip for figuring out orbital maneuvers- CHEAT!   I’m absolutely serious, find the cheat menu, and activate ‘Unlimited Fuel’ or whatever it is called.

Why?   Because spending a thousand hours never reaching your intended orbit doesn’t really teach you anything.   Turn on infinite fuel, and burn whatever it takes to achieve your desired orbit, or intercept a moon or craft.  Once you achieve the orbit or rendezvous you wanted, try it again, but see if you can do it more efficiently.  An hour or two buzzing around in a ship with unlimited fuel will give you a lot of insight on how to do orbital maneuvers.

Good luck, we’re all counting on you!

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Hi 18Watt (and everyone else),

Thank you again for your great help.  I could not have figured this out without the contribution by you and by Vanamonde.

I will keep practicing using the unlimited-fuel cheat.

I have to be away from KSP for a few hours.  Once I get back, I will work on trying to achieve an orbit around Mun.  That is my next goal.

Thanks again.  You have been tremendous.

Stanley

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13 hours ago, MetricKerbalist said:

I am in Kerbin's orbit.  I set up a maneuver that creates a new orbit.  But I cannot transfer my orbiting spacecraft onto the new orbit.  My spacecraft keeps bypassing the new orbit.

Could someone please tell me how I get onto the new orbit.

9 hours ago, MetricKerbalist said:

But the ship just follows the blue line.  I cannot get it to follow the dotted brown line that was created when I set up the maneuver.

I detect an issue, not necessarily with piloting, but rather with reading the map.  That's a skill all in itself.

The first thing to know about the map is that it is not like a static map of anything on Earth.  In space, everything is moving relative to everything else, so what you see in map view is a combination of a snapshot of where things are right now combined with predictive plots that are an attempt to give an idea of how those things are moving.  (Though I will note that by convention, the sun is considered motionless in order to provide a reference point.)

In terms of plotting manoeuvres, the first thing to know is that your rocket's current, immediate trajectory is always going to be the solid blue line.  If that path should go into a new sphere of influence (that's where a body other than Kerbin is the strongest local source of gravity, as in close approach to the Mun, for example), then it will turn solid brown at the point where it crosses into the new sphere of influence.  There are other colour changes for additional interactions later on.

The second thing to know is that when you plan a manoeuvre, the map view will generate a dotted line that will show your predicted path if and only if you execute the plotted manoeuvre.  Think of a manoeuvre node as something more akin to an itinerary than an automatic program.  You can plan to get off the train at a particular station, but unless you actually get up and leave the train at the right time, it won't happen on its own.

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38 minutes ago, Zhetaan said:

If that path should go into a new sphere of influence (that's where a body other than Kerbin is the strongest local source of gravity, as in close approach to the Mun, for example), then it will turn solid brown at the point where it crosses into the new sphere of influence.

Hi Zhetaan,

The information about the solid brown line is very instructive.

Thank you.

Stanley

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