Difference between revisions of "Maneuver node"

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Maneuver node in orbital view

Maneuver marker on navball

A maneuver node is a planed 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.

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.

Prograde and retrograde

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.

Normal and anti-normal

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 equatorline.

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.

Radial in and radial out

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.

Using

After adding a maneuver node there are three values shown next to the navball:

1. Velocity change needed in meters per second
2. Time to maneuver node or time since the craft passed the maneuver node
3. Estimated burn time

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.

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.