VSL (variable speed of light) cosmologists have theorised that Cosmic strings could be used as FTL highways for information. This is based on the theory that the speed of light was infinite at the birth of the universe and as inflation began, topological defects called Cosmic strings formed which still exist in our time and these strings contain compressed space-time where the speed of light is the same as the early universe, theoretically infinite or at least much higher than it is in our time.
This FTL theory is not part of my question as it speaks for itself and whether a worldbuilder wants to have a variable speed of light in their story. But this theory lead me to wonder about below speed of light form of travel using the gravitation field of a Cosmic string.
I am wondering if a ship could travel along a string in a spiralling motion using the gravitational pull of the string to propel it along. If we use the principles of gravitational assists from celestial bodies and possibly Penrose process for blackholes, if the cosmic string is likely to only pull a ship in a funnel shape spiral towards the string singularity then dumping some mass towards the string to propel out, although this method seems complicated and depended on the ship carrying mass to dump.
Preferably they could ride in a constant spiral without complications but what is the likely result if a ship tried this method and what would be needed for the ship to ride along it using the gravitational force of the string? If it is even possible.