I'm interested in the viability of the following scheme for (relatively) fast space commerce within the Solar System:
- have a fleet of space stations essentially built around a long linear accelerator.
- Stations don't have heavy-duty engines, but do have attitude engines able to (slightly) modify orbit.
- have ground stations on airless moons with similar (or longer) linear accelerators.
- send goods to stations by means of ground-based accelerators; station based accelerator is used to brake cargo.
- send goods to ground bases using station linear accelerator to kill speed of cargo (essentially eject it backward).
- both events, if done properly, will increase space station speed.
- use gravitational slingshot to modify space station trajectory towards next destination.
- use attitude controls to carefully trim transfer orbit to use next slingshot "right".
This way "reaction mass" is the cargo and space station will increase speed up to a maximum given by maximum speed attainable by ground station accelerators:
- in a first time uploading would give more speed to station because cargo "bullets" would be faster than S.S. and thus it has to slow them down gaining speed.
- at later time S.S. would be actually faster than cargo bullets, so it will slow down accelerating them to match its speed.
- downloading always will increase S.S. impulse.
- at a certain speed the two effects will be equivalent and S.S. won't gain more speed.
- max speed depends on $\Delta v$ available in the various linear accelerating "cannons".
- gravity well deflections must be carefully computed to give the S.S. the right orbital change to send it on the right path to meet next destination.
- Small bodies (w.g.: asteroids) that don't have enough mass to significantly deflect orbit should rely on "passing by" S.S. directed to other sizable bodies (up/down-load process might be from a (relatively) long distance.
How much is such a system viable with not-too-far future technology (at least permanent space bases should be available).