Create copy of Gravship scenario (feel free to disable pursuing mechanoids if you want) and save it.
Go to %userprofile%\appdata\locallow\Ludeon Studios\RimWorld by Ludeon Studios\Scenarios in explorer and open your saved scenario file with prefered text editor (eg. VScode).
Find part that looks like this:
            <li Class="ScenPart_ForcedMap">
                <def>ForcedMap</def>
                <mapGenerator>OrbitalRelay</mapGenerator>
 Orbit