Planet Partners are only allowed to release space worthy ships after reaching certain criteria put in place by MA.
Hence why Arkadia was able to release the Firebird.
If Rocktropia is ever able to reach these numbers, they too will be able to release a limited number of small personal UL warp ships for 50k ped, similar to the Equus and Firebird.
The UFO (L) will never be able to go into space.