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