Difference between revisions of "Maneuver node"

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| [[File:Maneuver.svg|thumb|107px|Maneuver marker on navball]]
 
| [[File:Maneuver.svg|thumb|107px|Maneuver marker on navball]]
 
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A maneuver node is a planned velocity change along an orbit. Multiple maneuver nodes can be added which will effect the following maneuver nodes. After adding a node it shows the velocity change needed to reach the next new orbit. It doesn't show a combination of all maneuver nodes, so after using a maneuver node it needs to be deleted manually and the system can showing the following maneuver node if any.
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A maneuver node is a planned velocity change along an orbit. Multiple maneuver nodes can be added which will affect the following maneuver nodes. After adding a node, it shows the velocity change needed to reach the next new orbit. If multiple maneuver nodes have been planned, only the first one will be displayed on the navball - once it has been completed, it should be deleted so that the next one becomes visible.
  
 
== Adding a Maneuver Node ==
 
== Adding a Maneuver Node ==
 
[[File:ManeuverNodes.PNG|thumb|Two maneuver nodes with one in edit mode]]
 
[[File:ManeuverNodes.PNG|thumb|Two maneuver nodes with one in edit mode]]
Click on the vessel's orbital line and a popup will give the option to add a new maneuver node. Once created, selecting and right-clicking the node gives the option to delete it. Selecting a node which the vessel has already passed, brings up the delete interface immediately.
+
Click on the vessel's orbital line and a popup will give the option to add a new maneuver node. Once created, selecting and right-clicking the node gives the option to delete it. If the maneuver node has been passed, selecting it immediately puts it in "delete" mode.
  
 
Hovering over a node displays the time of arrival and the [[w:Delta-v|Delta-V]] needed to perform the maneuver.
 
Hovering over a node displays the time of arrival and the [[w:Delta-v|Delta-V]] needed to perform the maneuver.
  
 
== Directions ==
 
== Directions ==
Because movements in space or air are three dimensional there are three basic axes to burn. For each axis there are two opposite directions. So any movement could be described with a combination of up to three separate directions.
+
Because there are three dimensions of movement in space (or air), there are three basic axes on which to burn, with two directions per axis; thus, all maneuvers can be described as a combination of movement in three separate directions.
  
 
=== Prograde and retrograde ===
 
=== Prograde and retrograde ===
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| [[File:Retrograde.svg|32px|Retrograde]]
 
| [[File:Retrograde.svg|32px|Retrograde]]
 
|}
 
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These vectors are directly changing the speed of the craft. Burning prograde will burning to the craft's velocity vector and raising the altitude of the orbit on the other side. They are colored green like the pro- and retrograde vectors on the [[navball]]. This is the most efficient way to change the orbital shape, so whenever possible these vectors should be used.
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These vectors directly change the speed of the craft. Burning prograde will increase velocity, raising the altitude of the orbit on the other side, while burning retrograde will decrease velocity and reduce the orbit altitude. Both of these vectors are directly visible on the [[navball]].
 +
 
 +
This is the most efficient way to change the orbital shape, so whenever possible these vectors should be used.
  
 
=== Normal and anti-normal ===
 
=== Normal and anti-normal ===
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| [[File:Anti-normal.svg|32px|Anti-normal]]
 
| [[File:Anti-normal.svg|32px|Anti-normal]]
 
|}
 
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The normal vectors are orthogonal to the orbital plane. Any burning normal or anti-normal will change the orbital inclination. On the navball it is between the pro- and retrograde marker on the equator line.
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The normal vectors are orthogonal to the orbital plane. Burning normal or anti-normal will change the orbital inclination. On the navball, the normal and anti-normal vectors are located on the equator line directly between the prograde and retrograde markers.
  
In most cases these vectors are needed to match the orbital inclination to another celestial body or craft. When the orbit crosses the other object's orbit burning normal or anti-normal is most efficient. To match the orbital inclination a normal burn is needed at the ascending node. At the descending node an anti-normal burn will move the inclination closer to the target's inclination.
+
These vectors are generally used to match the orbital inclination of another celestial body or craft, and the optimal time to do this is when the current craft's orbit intersects the orbital plane of the target. To match the orbital inclination, either perform a normal burn at the ascending node or an anti-normal burn at the descending node - when the correct magnitude is reached, the relative inclination at the selected node will reach 0° and the nodes will start to move rapidly toward each other's positions.
  
 
=== Radial in and radial out ===
 
=== Radial in and radial out ===
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| [[File:Radial-out.svg|32px|Radial out]]
 
| [[File:Radial-out.svg|32px|Radial out]]
 
|}
 
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The radial in vector is pointing to the orbited body while the radial out points away from the orbited body. When burning radially the orbit will rotate around the craft. At the beginning of the ascent from the launch pad the craft is burning in the same direction as radially out.
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The radial-in vector points directly toward the orbited body (center of the brown hemisphere on the navball), while the radial-out vector points directly away from it (center of the blue hemisphere). Performing a radial burn will rotate the orbit around the craft. Radial burns are the least efficient way of adjusting one's path - it is much more effective to use prograde and retrograde burns.
  
 +
During ascent from the launch pad, your craft is effectively burning radially outward.
  
 
== Using ==
 
== Using ==
There are six symbols on the newly created node. Each symbol can be clicked on (while holding) and then pulled or pushed to change the desired orbit. Pushing a symbol is equivalent to pulling the symbol on the opposite side. Pushing or pulling further increases the speed the orbit is changed.
+
Upon selecting a maneuver node, six symbols will appear, each corresponding to the vectors above. Each symbol can be clicked and dragged to adjust the amount of velocity change desired on each axis. Pulling a symbol away from the center of the node increases the speed change along the selected axis, and pushing a symbol toward the center of the node is equivalent to pulling the symbol on the opposite side. The further the symbol is pushed or pulled, the more rapidly the adjustment will be made.
  
After adding a maneuver node there are three values shown next to the naval:
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After adding a maneuver node, three new values will appear next to the [[navball]]:
# Velocity change needed in meters per second
+
# Velocity change required, in meters per second
# Time to maneuver node or time since the craft passed the maneuver node
 
 
# Estimated burn time
 
# Estimated burn time
 +
# Time to maneuver node (or time since the node was passed)
  
Because a maneuver node assumes a instantaneous velocity change a perfect burn is in many cases impossible, as longer burns are required. To get the best results it is recommended to burn a half of the time exactly before the actual change and the other half directly afterwards.
+
Because a maneuver node assumes an instantaneous velocity change, a perfect burn is impossible; to get the best results, it is recommended to burn half of the time before the node and the other half directly afterwards.
 
 
With maneuver nodes it is possible to reach a specific orbit, without checking the orbital map continually. When performing an [[aerobraking]] a previously placed maneuver node is showing the needed deceleration and will automatically updating the needed velocity change while decelerating in the atmosphere. If the aerobraking is outside the wanted deceleration this allows performing correcting maneuvers.
 
  
 +
Maneuver nodes can be used to reach a specific orbit without needing to continuously monitor the orbital map. When performing an [[aerobraking]] maneuver, the current maneuver node will automatically update the needed velocity change as the craft's velocity decreases; this can be used to perform manual corrections if the aerobraking turns out to be insufficient or excessive.
  
 
=== Prograde ===
 
=== Prograde ===
This is the direction of your velocity (velocity=speed+direction) and is symbolized by a yellow circle with three little wings at a 90 degree angle from each other.
+
This is the direction of your velocity (velocity=speed+direction) and is symbolized by a yellow circle with three little wings at 90 degree angles from each other, exactly the same as it appears on the navball.
  
Burning in this direction will increase your apoapsis or periapsis depending on where you are in your orbit. Think of it as increasing what your height above the ground will be on the opposite side of your orbit. This has other applications but this should help you get the gist of it.
+
Burning in this direction will increase your apoapsis or periapsis, depending on where you are in your orbit. Think of it as increasing what your height above the ground will be on the opposite side of your orbit. This has other applications but this should help you get the gist of it.
  
 
[[File:ManeuverNodePrograde.PNG|250px|thumbnail|none|Increasing the apoapsis.]]
 
[[File:ManeuverNodePrograde.PNG|250px|thumbnail|none|Increasing the apoapsis.]]
 
  
 
=== Retrograde ===
 
=== Retrograde ===
This is the opposite direction of your velocity and is symbolized by a yellow circle with a cross in it as well as three wings at a 120 degree angle from each other.
+
This is the opposite direction of your velocity and is symbolized by a yellow circle with a cross in it as well as three wings at a 120 degree angle from each other, exactly the same as it appears on the navball.
  
Burning in this direction will decrease your apoapsis or periapsis depending on where you are in your orbit. Think of it as decreasing what your height above the ground will be on the opposite side of your orbit.
+
Burning in this direction will decrease your apoapsis or periapsis, depending on where you are in your orbit. Think of it as decreasing what your height above the ground will be on the opposite side of your orbit.
  
 
[[File:ManeuverNodeRetrograde.PNG|250px|thumbnail|none|Decreasing the apoapsis.]]
 
[[File:ManeuverNodeRetrograde.PNG|250px|thumbnail|none|Decreasing the apoapsis.]]
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=== Normal ===
 
=== Normal ===
This direction is both perpendicular (i.e. forming a 90 degree angle) to the orbital plane ( the plane formed by one complete orbit along a particular orbital path or line) and perpendicular to the orbited body's radial direction or parallel to the surface (i.e. in the same direction as). It is symbolized by the pink triangle with a dot in the center.
+
This direction is both perpendicular (i.e. forming a 90 degree angle) to the orbital plane (the plane formed by one complete orbit along a particular orbital path or line) and perpendicular to the orbited body's radial direction or parallel to the surface (i.e. in the same direction as). It is symbolized by a pink triangle with a dot in the center.
  
This direction has two major uses. Primarily this maneuver is used to change the orbital plane by rotating it in the counter clock-wise direction (viewed from the side) around the point at which the burn takes place.
+
This direction has two major uses. Primarily, this maneuver is used to change the orbital plane by rotating it in the counter clock-wise direction (viewed from the side) around the point at which the burn takes place. The secondary use is to rendezvous with an orbiting object (ship, moon or planet); this is done by burning in this direction at the ascending node (i.e. the point at which your orbit intersects with the orbital plane of your target and begins passing beneath it)
The secondary use is to rendezvous with an orbiting object (ship, moon or planet). This is done by burning in this direction at the ascending node (i.e. the point at which the orbiting body's orbit you wish to rendezvous with crosses the orbit of your ship and the orbit of the orbiting body will be above the orbit of your ship beyond this point in the direction of travel.) This is the descending node from the orbiting body's perspective.
 
  
 
[[File:ManeuverNodeOrbitNormal.PNG|250px|thumbnail|none|Tilting the orbital plane counter-clockwise.]]
 
[[File:ManeuverNodeOrbitNormal.PNG|250px|thumbnail|none|Tilting the orbital plane counter-clockwise.]]
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=== Anti-normal ===
 
=== Anti-normal ===
This direction is both perpendicular to the orbital plane and perpendicular to the orbited body's radial direction or parallel to the surface. It is also 180 degrees from Orbit Normal or in the opposite direction. It is symbolized by the pink triangle with little wings on two of the sides.
+
This direction is both perpendicular to the orbital plane and perpendicular to the orbited body's radial direction or parallel to the surface. It is also 180 degrees from Orbit Normal or in the opposite direction. It is symbolized by a pink triangle with little wings on each side.
  
This direction has two major uses. Primarily, changes to orbital plane of the orbit by rotating in the clock-wise direction the orbit around the point at which the burn takes place. The secondary use is to rendezvous with an orbiting object (ship, moon, or planet); this is done by burring in this direction at the descending node (descending node= the point at which the orbiting body’s orbit you wish to rendezvous with crosses the orbit of your ship and the orbit of the orbiting body will be below the orbit of your ship beyond this point in the direction of travel.) By the way this is the ascending node from the orbiting body's perspective.
+
This direction has two major uses. Primarily, this is used to make changes to the orbital plane by rotating in the clock-wise direction around the point at which the burn takes place. The secondary use is to rendezvous with an orbiting object (ship, moon, or planet); this is done by burring in this direction at the descending node (i.e. the point at which your orbit intersects with the orbital plane of your target and begins passing above it).
  
 
[[File:ManeuverNodeOrbitAntiNormal.PNG|250px|thumbnail|none|Tilting the orbital plane clockwise.]]
 
[[File:ManeuverNodeOrbitAntiNormal.PNG|250px|thumbnail|none|Tilting the orbital plane clockwise.]]
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This direction points in the direction of the orbited body, i.e. it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with what looks like a four leaf clover in it (actually 4 inward wings).
 
This direction points in the direction of the orbited body, i.e. it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with what looks like a four leaf clover in it (actually 4 inward wings).
  
This direction is used to rotate the orbit about the point of burn without changing the orbital plane. (Think spinning a hula hoop with a stick.) This direction will rotate the orbit counter clock-wise with a maximum change in angle of less than 90 degrees. (The orbit will pass through the center of mass of the orbited body at maximum change of angle. The ship would traverse a slow spiral in towards the center of mass of the orbited body.)
+
This direction is used to rotate the orbit about the point of burn without changing the orbital plane (think spinning a hula hoop with a stick). This direction will rotate the orbit counter-clockwise with a maximum change in angle of less than 90 degrees; beyond this point, the orbit would pass through the center of mass of the orbited body, and the ship would traverse a slow spiral in towards the center of mass of the orbited body.
  
 
This is primarily used in rendezvous to line up two irregular orbits.
 
This is primarily used in rendezvous to line up two irregular orbits.
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This direction points away from of the orbited body; also, it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with a dot in the center and four wings at 90 degrees from each other.
 
This direction points away from of the orbited body; also, it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with a dot in the center and four wings at 90 degrees from each other.
  
This direction is used to rotate the orbit about the point of burn without changing the orbital plane. This direction will rotate the orbit clock-wise with a maximum change in angle of less than 90 degrees. (The maximum angle can never approach 90 degrees unless you perfectly cancel all horizontal momentum. This not possible in real life however it is possible in Kerbal Space Program. Normally the ship would traverse a slow spiral away from the center of mass of the orbited body.)
+
This direction is used to rotate the orbit about the point of burn without changing the orbital plane. This direction will rotate the orbit clockwise with a maximum change in angle of less than 90 degrees; beyond this point, all horizontal momentum would be cancelled (this not possible in real life, but it is possible in Kerbal Space Program; normally, the ship would traverse a slow spiral away from the center of mass of the orbited body).
  
 
This is primarily used in rendezvous to line up two irregular orbits.
 
This is primarily used in rendezvous to line up two irregular orbits.
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== Burning ==
 
== Burning ==
[[File:ManeuverNodesNavBall.PNG|200px|thumbnail|right|The nav ball at the bottom shows the blue marker the vessel has to be oriented to to perform the desired maneuver during the burn.]]
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[[File:ManeuverNodesNavBall.PNG|200px|thumbnail|right|The nav ball at the bottom shows the blue marker the vessel has to be oriented to perform the desired maneuver during the burn.]]
To perform the desired maneuver, you have to initiate a burn at the time indicated. This is true for short burns. For long burns you want to get approximately ½ of your burn done before you actually hit the node.
 
  
If you are using SAS you can line up your nave ball indicator and the blue burn direction indicator as soon as you are done setting up the maneuver node (see screenshot).
+
To perform the desired maneuver, you have to initiate a burn at the time indicated. For long burns, you will want to perform approximately one half of your burn done before you actually hit the node (and the remainder afterwards).
  
The reason the marker moves as you approach the end of the burn is because you did not have your burn perfectly lined up with the center of the marker. This can be ignored since it is usually a small error rather than a large one.
+
If you are using SAS, you can line up your navball indicator with the blue burn direction indicator as soon as you are done setting up the maneuver node (see screenshot) - once the maneuver has been defined, the burn direction will not change, regardless of your craft's position.
  
Stop burning (key "x") once the change in velocity is close to approaching zero. After zero is reached the blue marker becomes meaningless and you can then delete the node marker since by this point you should be past it. This is even more important if you have set up multiple maneuver nodes since it will not go to the next nodal maneuver until the passed one is deleted.
+
As you complete your burn, the marker may begin to move away from your current heading; this is merely because you were not perfectly lined up. This can generally be ignored, since it is usually a small error rather than a large one.
  
 +
Once the desired velocity change approaches zero, reduce your throttle so as to avoid overshooting; once it reaches zero (or reaches a sufficiently small value), stop burning (press "x"). Once the maneuver is completed, the blue marker becomes meaningless, so you should delete the node. This is especially important if you have set up multiple maneuver nodes, since the next node will not show up until you delete the current one.
  
 
[[Category:Control]]
 
[[Category:Control]]

Revision as of 04:43, 6 May 2013

Maneuver node in orbital view
Maneuver marker on navball

A maneuver node is a planned velocity change along an orbit. Multiple maneuver nodes can be added which will affect the following maneuver nodes. After adding a node, it shows the velocity change needed to reach the next new orbit. If multiple maneuver nodes have been planned, only the first one will be displayed on the navball - once it has been completed, it should be deleted so that the next one becomes visible.

Adding a Maneuver Node

Two maneuver nodes with one in edit mode

Click on the vessel's orbital line and a popup will give the option to add a new maneuver node. Once created, selecting and right-clicking the node gives the option to delete it. If the maneuver node has been passed, selecting it immediately puts it in "delete" mode.

Hovering over a node displays the time of arrival and the Delta-V needed to perform the maneuver.

Directions

Because there are three dimensions of movement in space (or air), there are three basic axes on which to burn, with two directions per axis; thus, all maneuvers can be described as a combination of movement in three separate directions.

Prograde and retrograde

Prograde Retrograde

These vectors directly change the speed of the craft. Burning prograde will increase velocity, raising the altitude of the orbit on the other side, while burning retrograde will decrease velocity and reduce the orbit altitude. Both of these vectors are directly visible on the navball.

This is the most efficient way to change the orbital shape, so whenever possible these vectors should be used.

Normal and anti-normal

Normal Anti-normal

The normal vectors are orthogonal to the orbital plane. Burning normal or anti-normal will change the orbital inclination. On the navball, the normal and anti-normal vectors are located on the equator line directly between the prograde and retrograde markers.

These vectors are generally used to match the orbital inclination of another celestial body or craft, and the optimal time to do this is when the current craft's orbit intersects the orbital plane of the target. To match the orbital inclination, either perform a normal burn at the ascending node or an anti-normal burn at the descending node - when the correct magnitude is reached, the relative inclination at the selected node will reach 0° and the nodes will start to move rapidly toward each other's positions.

Radial in and radial out

Radial in Radial out

The radial-in vector points directly toward the orbited body (center of the brown hemisphere on the navball), while the radial-out vector points directly away from it (center of the blue hemisphere). Performing a radial burn will rotate the orbit around the craft. Radial burns are the least efficient way of adjusting one's path - it is much more effective to use prograde and retrograde burns.

During ascent from the launch pad, your craft is effectively burning radially outward.

Using

Upon selecting a maneuver node, six symbols will appear, each corresponding to the vectors above. Each symbol can be clicked and dragged to adjust the amount of velocity change desired on each axis. Pulling a symbol away from the center of the node increases the speed change along the selected axis, and pushing a symbol toward the center of the node is equivalent to pulling the symbol on the opposite side. The further the symbol is pushed or pulled, the more rapidly the adjustment will be made.

After adding a maneuver node, three new values will appear next to the navball:

  1. Velocity change required, in meters per second
  2. Estimated burn time
  3. Time to maneuver node (or time since the node was passed)

Because a maneuver node assumes an instantaneous velocity change, a perfect burn is impossible; to get the best results, it is recommended to burn half of the time before the node and the other half directly afterwards.

Maneuver nodes can be used to reach a specific orbit without needing to continuously monitor the orbital map. When performing an aerobraking maneuver, the current maneuver node will automatically update the needed velocity change as the craft's velocity decreases; this can be used to perform manual corrections if the aerobraking turns out to be insufficient or excessive.

Prograde

This is the direction of your velocity (velocity=speed+direction) and is symbolized by a yellow circle with three little wings at 90 degree angles from each other, exactly the same as it appears on the navball.

Burning in this direction will increase your apoapsis or periapsis, depending on where you are in your orbit. Think of it as increasing what your height above the ground will be on the opposite side of your orbit. This has other applications but this should help you get the gist of it.

Increasing the apoapsis.

Retrograde

This is the opposite direction of your velocity and is symbolized by a yellow circle with a cross in it as well as three wings at a 120 degree angle from each other, exactly the same as it appears on the navball.

Burning in this direction will decrease your apoapsis or periapsis, depending on where you are in your orbit. Think of it as decreasing what your height above the ground will be on the opposite side of your orbit.

Decreasing the apoapsis.


Normal

This direction is both perpendicular (i.e. forming a 90 degree angle) to the orbital plane (the plane formed by one complete orbit along a particular orbital path or line) and perpendicular to the orbited body's radial direction or parallel to the surface (i.e. in the same direction as). It is symbolized by a pink triangle with a dot in the center.

This direction has two major uses. Primarily, this maneuver is used to change the orbital plane by rotating it in the counter clock-wise direction (viewed from the side) around the point at which the burn takes place. The secondary use is to rendezvous with an orbiting object (ship, moon or planet); this is done by burning in this direction at the ascending node (i.e. the point at which your orbit intersects with the orbital plane of your target and begins passing beneath it)

Tilting the orbital plane counter-clockwise.


Anti-normal

This direction is both perpendicular to the orbital plane and perpendicular to the orbited body's radial direction or parallel to the surface. It is also 180 degrees from Orbit Normal or in the opposite direction. It is symbolized by a pink triangle with little wings on each side.

This direction has two major uses. Primarily, this is used to make changes to the orbital plane by rotating in the clock-wise direction around the point at which the burn takes place. The secondary use is to rendezvous with an orbiting object (ship, moon, or planet); this is done by burring in this direction at the descending node (i.e. the point at which your orbit intersects with the orbital plane of your target and begins passing above it).

Tilting the orbital plane clockwise.


Radial in

This direction points in the direction of the orbited body, i.e. it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with what looks like a four leaf clover in it (actually 4 inward wings).

This direction is used to rotate the orbit about the point of burn without changing the orbital plane (think spinning a hula hoop with a stick). This direction will rotate the orbit counter-clockwise with a maximum change in angle of less than 90 degrees; beyond this point, the orbit would pass through the center of mass of the orbited body, and the ship would traverse a slow spiral in towards the center of mass of the orbited body.

This is primarily used in rendezvous to line up two irregular orbits.

Rotating the orbital plane counter-clockwise.


Radial out

This direction points away from of the orbited body; also, it is perpendicular to the surface of the orbited body. It is also perpendicular to the direction of travel and Orbit Normal. It is symbolized by a blue circle with a dot in the center and four wings at 90 degrees from each other.

This direction is used to rotate the orbit about the point of burn without changing the orbital plane. This direction will rotate the orbit clockwise with a maximum change in angle of less than 90 degrees; beyond this point, all horizontal momentum would be cancelled (this not possible in real life, but it is possible in Kerbal Space Program; normally, the ship would traverse a slow spiral away from the center of mass of the orbited body).

This is primarily used in rendezvous to line up two irregular orbits.

Rotating the orbital plane clockwise.

Burning

The nav ball at the bottom shows the blue marker the vessel has to be oriented to perform the desired maneuver during the burn.

To perform the desired maneuver, you have to initiate a burn at the time indicated. For long burns, you will want to perform approximately one half of your burn done before you actually hit the node (and the remainder afterwards).

If you are using SAS, you can line up your navball indicator with the blue burn direction indicator as soon as you are done setting up the maneuver node (see screenshot) - once the maneuver has been defined, the burn direction will not change, regardless of your craft's position.

As you complete your burn, the marker may begin to move away from your current heading; this is merely because you were not perfectly lined up. This can generally be ignored, since it is usually a small error rather than a large one.

Once the desired velocity change approaches zero, reduce your throttle so as to avoid overshooting; once it reaches zero (or reaches a sufficiently small value), stop burning (press "x"). Once the maneuver is completed, the blue marker becomes meaningless, so you should delete the node. This is especially important if you have set up multiple maneuver nodes, since the next node will not show up until you delete the current one.