This mode exists to solve a problem familiar to anyone who's ever tried to get an Apollo command module back from the moon. How do I go from an existing lunar orbit into an efficient Earth transit? This mode helps to plan a solution to that problem.
Most of the rest of the time, it is better to use Eject mode and start from the surface. Even when in orbit, you may be able to find an efficient way of working with the Eject mode, and that is usually better. But, if all else fails, the Orbit Eject mode may be what you need if you're in orbit around a planet or moon.
How do I access the Orbit eject function?
You need to use the FN (Shift-F) key to switch TransX to the orbit eject
function.You also need to set MAJ and MIN correctly. MIN will be the object
you're orbiting, and MAJ will be the body that MIN orbits. Set MAJ first, as
setting MAJ resets MIN.
You may set a target if you want to. If you want to fly to the central body (eg Moon to Earth) do not set a target at all, and the MFD will give you information relevant to flying to the central body instead.
Minor view. This shows your existing orbit around the Minor body, and any hypothetical orbit you create using variables.
Major view. This shows the minor body's orbit, any hypothetical orbit you generate using variables, and your actual orbit if you have escape velocity from the Minor body.
The third view shows both a small target, and a small rendition of the minor view. This is intended to help with complex skewed burns. The target shows the correct direction to point in to do both the skew and the prograde manoevres. It (unfortunately) doesn't help you aim in the outward direction as yet.
There is another set of variables which apply specifically to this mode.
Projection. This adjusts the angle from which you see the orbit in the minor view. The choices are Ecliptic, Craft, Hypothetical, or Minor plane (the plane in which the minor body orbits the major one)
View orbits. You can either view them all, or concentrate purely on the hypothetical one.
Base Orbit. This is a snapshot of your current orbit. Press ++, or reset the MFD to take another snapshot.
Prograde deltaV- the addition to your velocity in a prograde direction in your orbit around the minor body.
Ch. plane deltaV - This adds a sideways component to your velocity change, thus carrying out a plane change at the time of ejection. I would suggest leaving this at zero unless absolutely necessary, as it is difficult to fly this type of burn. The small target in the third view helps you to aim your ship in the right direction for this type of burn. If you leave this variable at zero you can use the standard orbiter prograde autopilot instead.
Eject date - The date when the burn will take place. Adjust this to change the time of the burn. This has the effect of rotating your planned orbit around the minor planet.
Projection. There are two choices, ecliptic, or craft plane.
Intercept with. Hypothetical or craft. Default is hypothetical. This is used in the case that you are attempting to go to another planet or moon rather than fly to the central body.
View orbits. Your choices are All, Target or Craft.
Usually the best method is to set some prograde velocity until you reach escape velocity of the minor body, and a bit more. Then adjust both the Prograde velocity and the eject date to refine a good course for your flight, switching back and forth between the views until you're happy. Below are two screenshots I took using AMSO in Orbiter version 190402, showing an orbit created by adjusting both these variables. This particular AMSO scenario has a lunar orbir almost coplanar with the Earth/Moon system, so it produces a nice result.
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Some orbits just don't produce a nice result whatever you do. In such circumstances, it's often best to just do the best you can without using too much fuel, and aim to sort it out once you get out of that body's SOI.
When you cross the border of the SOI, you will be switched into the Cruise function, which also contains information helping you to target the central body if you wish.
Next: Tutorial home
Orbiter Mars - (C) Duncan Sharpe 2003