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 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.
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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 next to the [[navball]]. If multiple maneuver nodes have been planned, only the velocity change needed for the first node will be displayed on the navball - once that node has been completed it should be deleted so that the next velocity change becomes visible.
  
== Adding a Maneuver Node ==
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In [[career mode]], maneuver nodes are unavailable at first. Using them requires upgrading both the [[Tracking Station]] and [[Mission Control]].
 +
<span id="Adding a Maneuver Node"></span>
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== 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. If the maneuver node has been passed, selecting it immediately puts it in "delete" 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 [[w:Delta-v|Delta-V]] needed to perform the maneuver.
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Hovering over a node displays the time of arrival and the [[w:Delta-v|delta v]] needed to perform the maneuver.
 +
 
 +
After the node is created, it can also be dragged along the orbital path at any time. This is very useful when planning an orbital rendezvous and the placement was a bit off.  When the view is focused on the maneuver node, dragging it can be difficult to control. It's much easier when moving a maneuver node to place a temporary node nearby and focus the view on that one while dragging.
  
 
== Directions ==
 
== 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.
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 +
<gallery widths=64px heights=64px>
 +
File:Prograde.svg|Prograde
 +
File:Retrograde.svg|Retrograde
 +
File:Normal.svg|Normal
 +
File:Anti-normal.svg|Anti-normal
 +
File:Radial-in.svg|Radial (in)
 +
File:Radial-out.svg| Anti-radial (out)
 +
</gallery>
 +
 
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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. All six of these directions are marked on the [[navball]], using the symbols above.
 +
 
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The relationship between these three orbital vectors - prograde, radial and normal - is defined by the right hand rule. If you hold the first three fingers of your right hand at right angles to each other in the most natural way, the index finger points forwards representing prograde, the middle finger points towards the orbital focus representing the radial, and the thumb points "upwards" represents the normal. For a prograde equatorial orbit around Kerbin (following Kerbin's rotation, i.e. eastward), normal will be north, prograde will be east, and radial will be down.
  
 
=== Prograde and retrograde ===
 
=== Prograde and retrograde ===
{| style="float: right;"
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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 on the other side. To raise a craft from a lower orbit into a higher orbit using a [[Hohmann transfer orbit|Hohmann transfer]] two prograde burns are executed; while lowering an orbit two retrograde burns are used.
| [[File:Prograde.svg|32px|Prograde]]
 
| [[File:Retrograde.svg|32px|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.
+
This is the most efficient way to change the orbital shape (specifically the most common case, raising or lowering apsides) so whenever possible these vectors should be used. When the craft is powerful enough it is possible to switch the orbital inclination by 180° when burning retrograde to cancel out all orbital velocity and then build it back up, which is faster and more efficient than using the normal vectors.
  
 
=== Normal and anti-normal ===
 
=== Normal and anti-normal ===
{| style="float: right;"
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The normal vectors are perpendicular 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.
| [[File:Normal.svg|32px|Normal]]
 
| [[File:Anti-normal.svg|32px|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.
+
These vectors are generally used to match the orbital inclination of another celestial body or craft, and the only time this is possible is when the current craft's orbit intersects the orbital plane of the target - at the ascending and descending nodes. To match the orbital inclination, either perform an anti-normal burn at the ascending node or a normal burn at the descending node. When the relative inclination at the nodes will reach 0° and they will start to move rapidly toward each other's positions.
  
=== Radial in and radial out ===
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<span id="Radial in and radial out"></span>
{| style="float: right;"
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=== Radial and anti-radial ===
| [[File:Radial-in.svg|32px|Radial in]]
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These vectors are parallel to the orbital plane, and perpendicular to the prograde vector. The radial (or radial-in) vector points inside the orbit, towards the focus of the orbit, while the anti-radial (or radial-out) vector points outside the orbit, away from the body. Performing a radial burn will rotate the orbit around the craft like spinning a hula hoop with a stick. Radial burns are usually not an efficient way of adjusting one's path - it is generally more effective to use prograde and retrograde burns. The maximum change in angle is always less than 90°; 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 orbited body.
| [[File:Radial-out.svg|32px|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.
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=== Effects on orbit ===
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<gallery widths=200px heights=117px>
 +
File:ManeuverNodePrograde.PNG|Increasing the opposite point's height of the orbit using a prograde burn.
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File:ManeuverNodeRetrograde.PNG|Decreasing the opposite point's height of the orbit using a retrograde burn.
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</gallery>
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<gallery widths=200px heights=117px>
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File:ManeuverNodeOrbitNormal.PNG|Tilting the orbital plane counter-clockwise using a normal burn.
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File:ManeuverNodeOrbitAntiNormal.PNG|Tilting the orbital plane clockwise using an anti-normal burn.
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</gallery>
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<gallery widths=200px heights=117px>
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File:ManeuverNodeRadialIn.PNG|Rotating the orbital plane corresponding with the orbiting direction using a radial-in burn.
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File:ManeuverNodeRadialOut.PNG|Rotating the orbital plane opposite with the orbiting direction using a radial-out burn.
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</gallery>
  
 
== Using ==
 
== 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.
+
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. Adjustments to an axis can be made also by hovering over one of its nodes and scrolling the mouse wheel.
  
After adding a maneuver node, three new values will appear next to the [[navball]]:
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After adding a maneuver node three new values will appear next to the [[navball]]:
 
# Velocity change required, in meters per second
 
# Velocity change required, in meters per second
 
# Estimated burn time
 
# Estimated burn time
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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.
 
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.
+
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.
 
 
 
[[File:ManeuverNodePrograde.PNG|250px|thumbnail|none|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.
 
 
 
[[File:ManeuverNodeRetrograde.PNG|250px|thumbnail|none|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)
 
 
 
[[File:ManeuverNodeOrbitNormal.PNG|250px|thumbnail|none|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).
 
 
 
[[File:ManeuverNodeOrbitAntiNormal.PNG|250px|thumbnail|none|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.
 
 
 
[[File:ManeuverNodeRadialIn.PNG|250px|thumbnail|none|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).
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[[File:TwoBlue.jpg|thumbnail|left|The Orbit Buttons]]
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==== Orbit buttons ====
  
This is primarily used in rendezvous to line up two irregular orbits.
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In {{version|0.23.5}} two small buttons were added when right-clicking a maneuver node. These buttons move the maneuver between future passes of the orbit without changing its position relative to the parent body, allowing maneuvers to be planned much further ahead of time. The right '''+''' button will move the maneuver to the next subsequent orbit, and the left '''-''' button will move it to the previous one.
  
[[File:ManeuverNodeRadialOut.PNG|250px|thumbnail|none|Rotating the orbital plane clockwise.]]
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{{clear|left}}
  
 
== 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 perform the desired maneuver during the burn.]]
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[[File:ManeuverNodesNavBall.PNG|thumb|The nav ball at the bottom shows the blue marker the vessel must be oriented to in order 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).
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For best results the burn should be initiated roughly half of the duration of the burn before the indicated burn time. For instance, if the burn duration is 20 seconds the burn should be started around t- 10 seconds.
  
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.
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[[SAS]] can help line up the level indicator with the blue burn direction indicator as soon as maneuver node is set up - once the maneuver has been defined, the burn direction will not change regardless of the craft's position. [[Pilot]]s of [[Experience#Levels|experience level]] 3 stars or higher enable the maneuver marker [[direction selector]] option when [[S.A.S.]] is enabled. This can automatically establish and maintain the vessel orientation throughout a maneuver burn. The more expensive, higher research level [[Probe]] cores can also do this.
  
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.
+
On completion of the burn the marker may begin to move away from the current heading; this is merely because it was not perfectly lined up. This can generally be ignored since it is usually a small error rather than a large one. The craft can be rotated to refine the burn direction and reduce such heading errors during long burns since they will be much more apparent, although care should be taken not to over-correct. If the craft is over-correcting with the smallest burn, it may be best to wait to make a small correction burn later, when the orbit will be less sensitive to applications of thrust. Alternatively engines with lower thrust, like [[RCS]] engines or engines with adjusted thrust level tweakable, could be used.
  
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.
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Once the desired velocity change approaches zero the throttle should be reduced to avoid overshooting; once it reaches zero (or reaches a sufficiently small value) the burn should be stopped (press {{key press|X}}). Once the maneuver is completed the node should be deleted to clear the blue directional marker. This is especially important if multiple maneuver nodes are set up since the next node values will not show up until the last one is deleted.
  
 
[[Category:Control]]
 
[[Category:Control]]

Latest revision as of 14:58, 24 October 2018

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 next to the navball. If multiple maneuver nodes have been planned, only the velocity change needed for the first node will be displayed on the navball - once that node has been completed it should be deleted so that the next velocity change becomes visible.

In career mode, maneuver nodes are unavailable at first. Using them requires upgrading both the Tracking Station and Mission Control.

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.

After the node is created, it can also be dragged along the orbital path at any time. This is very useful when planning an orbital rendezvous and the placement was a bit off. When the view is focused on the maneuver node, dragging it can be difficult to control. It's much easier when moving a maneuver node to place a temporary node nearby and focus the view on that one while dragging.

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. All six of these directions are marked on the navball, using the symbols above.

The relationship between these three orbital vectors - prograde, radial and normal - is defined by the right hand rule. If you hold the first three fingers of your right hand at right angles to each other in the most natural way, the index finger points forwards representing prograde, the middle finger points towards the orbital focus representing the radial, and the thumb points "upwards" represents the normal. For a prograde equatorial orbit around Kerbin (following Kerbin's rotation, i.e. eastward), normal will be north, prograde will be east, and radial will be down.

Prograde and 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 on the other side. To raise a craft from a lower orbit into a higher orbit using a Hohmann transfer two prograde burns are executed; while lowering an orbit two retrograde burns are used.

This is the most efficient way to change the orbital shape (specifically the most common case, raising or lowering apsides) so whenever possible these vectors should be used. When the craft is powerful enough it is possible to switch the orbital inclination by 180° when burning retrograde to cancel out all orbital velocity and then build it back up, which is faster and more efficient than using the normal vectors.

Normal and anti-normal

The normal vectors are perpendicular 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 only time this is possible is when the current craft's orbit intersects the orbital plane of the target - at the ascending and descending nodes. To match the orbital inclination, either perform an anti-normal burn at the ascending node or a normal burn at the descending node. When the relative inclination at the nodes will reach 0° and they will start to move rapidly toward each other's positions.

Radial and anti-radial

These vectors are parallel to the orbital plane, and perpendicular to the prograde vector. The radial (or radial-in) vector points inside the orbit, towards the focus of the orbit, while the anti-radial (or radial-out) vector points outside the orbit, away from the body. Performing a radial burn will rotate the orbit around the craft like spinning a hula hoop with a stick. Radial burns are usually not an efficient way of adjusting one's path - it is generally more effective to use prograde and retrograde burns. The maximum change in angle is always less than 90°; 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 orbited body.

Effects on orbit

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. Adjustments to an axis can be made also by hovering over one of its nodes and scrolling the mouse wheel.

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.

The Orbit Buttons

Orbit buttons

In version 0.23.5 two small buttons were added when right-clicking a maneuver node. These buttons move the maneuver between future passes of the orbit without changing its position relative to the parent body, allowing maneuvers to be planned much further ahead of time. The right + button will move the maneuver to the next subsequent orbit, and the left - button will move it to the previous one.

Burning

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

For best results the burn should be initiated roughly half of the duration of the burn before the indicated burn time. For instance, if the burn duration is 20 seconds the burn should be started around t- 10 seconds.

SAS can help line up the level indicator with the blue burn direction indicator as soon as maneuver node is set up - once the maneuver has been defined, the burn direction will not change regardless of the craft's position. Pilots of experience level 3 stars or higher enable the maneuver marker direction selector option when S.A.S. is enabled. This can automatically establish and maintain the vessel orientation throughout a maneuver burn. The more expensive, higher research level Probe cores can also do this.

On completion of the burn the marker may begin to move away from the current heading; this is merely because it was not perfectly lined up. This can generally be ignored since it is usually a small error rather than a large one. The craft can be rotated to refine the burn direction and reduce such heading errors during long burns since they will be much more apparent, although care should be taken not to over-correct. If the craft is over-correcting with the smallest burn, it may be best to wait to make a small correction burn later, when the orbit will be less sensitive to applications of thrust. Alternatively engines with lower thrust, like RCS engines or engines with adjusted thrust level tweakable, could be used.

Once the desired velocity change approaches zero the throttle should be reduced to avoid overshooting; once it reaches zero (or reaches a sufficiently small value) the burn should be stopped (press X). Once the maneuver is completed the node should be deleted to clear the blue directional marker. This is especially important if multiple maneuver nodes are set up since the next node values will not show up until the last one is deleted.