Alternately I wonder if you could exploit these for propulsion or gravity assist somehow? A lot of the "interstellar travel is almost impossible" calculations r

Alternately I wonder if you could exploit these for propulsion or gravity assist somehow? A lot of the "interstellar travel is almost impossible" calculations rely on interstellar space modeled as an absolute void and thus requiring you to carry all fuel and all propellant. Of course these calculations also tend not to consider staging, just like the "reaching the moon is impossible" calculations prior to Apollo.