Getting massive objects moving seems to be one of the biggest
challenges that we face with exploration of the solar system. With
manned missions, the paraphernalia that processes the environment to
make it habitable contributes quite a bit of extra mass to a vehicle.

My Bright Idea:

Get the reusable mass of a spacecraft moving and keep it moving
between two or more destinations.

For example, a vehicle that travels between Earth and Mars could be as
massive as desired, continually travelling between the two planets.
The consumables for the vehicle, such as fuel for a NEXIS-style
engine, as well as transferred cargo, such as passengers and freight
would be accelerated to dock with the vehicle during its next pass.

The engines would keep the ship on course as the geometry of the
course between Earth and Mars changes. Highly efficient and low
thrusting engines, such as NEXIS engines, should be able to handle
such a task. When the orbital dynamics work out such that the vehicle
is going to have to follow a path that will take it back to its
starting point without having reached an interesting destination, the
vehicle can be abandoned, and subsequently recovered when it next
returns.

The basic idea here is to get the most massive parts of a spacecraft
moving once, and then kept moving, while the 'disposable', lighter
parts of the missions - the crew, cargo and fuel - are added at the
source and removed at the destination.

I'm thinking BIG here. Big enough that the biological needs of the
crews are self-contained and self-sustaining. With enough shielding
to avoid having to worry about significant radiation exposure.
Whatever we want, because the whole thing is going to be accelerated
one time, and then kept moving with clever swings past source and
destination with fine-tuning of paths accomplished with efficient,
low-impulse engines.

Is this notion fundmentally flawed in some way?

My biggest assumptions a

1. Transit systems (power plant, engines, shielding, life-support,
various electronics) is the largest portion of the vehicle mass.

2. Human consumables can be preserved in the vehicle through recovery
and recycling.

2. A vehicle can be continuously looped between destinations in the
solar system that are both interesting and practical to reach.
Perhaps not always the same two destinations for a given vehicle. I
assume that the transit time between Earth and Mars (for example) will
be excessive during certain periods.

3. Engines such as NEXIS can be used to tweak orbital trajectories
where simple passes of massive bodies (planets, moons, etc) cannot do
the whole job.

Yes, I'm handwaving tons of other things, but I'm wondering if, in the
most coarse view, whether this is a 'good idea'.

JB