Synchronizing orbits

When the two orbital planes are aligned, REDSHIFT will perform a orbit synchronization to get the vessel and the target (the ISS in our case) to the same point at the same time.

Since the ISS is behind us (in orbital movement), REDSHIFT will increase revolution time for the vessel. This will allow the ISS to catch up and meet us at the calculated point.

The synchronization is performed at periapsis. This is the point where increasing revolution time is least expensive (in terms of fuel). So the first step is to wait for periapsis to perform the main engine burn.

At periapsis the main engine is turned prograde and fired until the vessel and the ISS meet at the calculated position at the same time. If the time difference dt between vessel and ISS is below a given limit (5 seconds), the main engine cuts-off.

When the sync burn is done, all is left for the processor is to wait for capture. This can take a while (depending on the TimeLimit you specify), but luckily you know how to accelerate time...

When you are closing on the ISS on the final orbit, watch for the distance value labeled [d=...]. If this value reaches "0", you are locked-in for approach. If you miss the ISS (d never becomes zero), the process will terminate after the calculated time. This might leave you up to 300 km behind (or in front) of the ISS, but the Approach procesor is capable of handling such large distances (at the expense of fuel, of course).

Process definition

<Step>
  <Label>Synchronizing orbits</Label>
  <Processor type="SyncOrbit">
    <Var name="Reference"> ISS </Var>
    <Var name="TimeLimit"> 24:00:00 </Var>
    <Var name="TurnTime"> 45 </Var>
    <Var name="Thrust"> 100 </Var>
    <Var name="CaptureDist"> 100k </Var>
    <Var name="FinalDist"> 50k </Var>
  </Processor>
</Step>

Reference defines the target orbit we will sync with.

TimeLimit let you specify, within with time limit you want to reach the reference object (written as hour:min:sec, min:sec or secs). The default setting is 6:00:00). The longer the time limit the smoother (and less fuel-consuming) the interception orbit is.

TurnTime specifies the longest time (in seconds) that the ship will need to turn to a specified direction. Defaults to 30 seconds.

Thrust specifies the thrust level used for the synchronization burn..

CaptureDist defines the distance from the specified completion distance (see below) when the procedure "locks on" to capture mode.

FinalDist specifies the condition when capture (and synchronizing) is considered complete. Defined in terms of distance (in meter) from the dock.