## The Ascent to orbit

When the launch has reached its final altitude, the Ascent processor takes over to bring the vessel into a stable orbit. Since we are launching to ISS (as defined in the definition file), the Ascent processor will try to minimize relative inclination to the target orbit during the ascent phase.

It does so by following the launch heading until the relative inclination reaches a minimum. The ascent then heads towards the velocity vector which leaves inclination and LAN unchanged.

The Ascent processor shows a profile of the six most important flight parameters during ascent: Pitch ("P" green), vertical velocity ("Vz" brown), velocity ("V" darkbrown), Altitude ("A" blue), Thruster level ("Th" magenta) and aerodynamic stress (unlabeled red).

### Process definition

    <Step>
      <Label>Ascend to orbit</Label>
      <Processor type="Profile">
        <Var name="H">       2k  10k  20k  60k  100k  150k  200k  260k </Var>
        <Var name="Pitch">   70   75   70   60    50    40    20     0 </Var>
        <Var name="Thrust"> 100  100  100  100   100   100   100   100 </Var>
        <Var name="AlignWith"> ISS </Var>
        <Var name="LockVz"> yes </Var>
        <Var name="MaxG"> 3.0 </Var>
        <Var name="CompleteAt"> PeD = 6.525M </Var>
      </Processor>
    </Step>

The Ascent profile processor currently only handles altitude-based profiles (no time- or rule-based profiles in this version). An altitude-based profile maps a current altitude into target values for pitch and thruster level. It may take some experiments (and thus experience) to design your own profile. I recommend you fly the ship by hand to orbit and write down your pitch and thruster levels at different altitudes and use that to create a new Ascent profile.

AlignWith should reference the vessel (resp. space station) you want to meet in orbit. This allows the Ascent processor to minimize relative inclination between our own and the reference orbit.

MaxG defines the maximal acceleration allowed during ascent (in G). This setting overrides any thruster level defined if necessary.

LockVz allows to override any defined pitch value at the end of the ascent. Activated when the vertical velocity becomes zero; while active the pitch is calculated to keep the vertical velocity close to zero. This option makes orbit injection (and profile definition) much easier and simpler.

CompleteAt defines the condition when the Ascent to orbit is considered complete. In this tutorial we stop, when the periapsis is about 150km above ground (which makes up a save orbit. (The apoapsis distance depends on the Ascent profile; in our case it should be a bit higher than periapsis)