If a truly fuel-less launch mechanism existed, don't you think we'd be using it right now?
Even air-breathing engines require fuel to heat and expand the air for thrust.
Option 1:
Your spacecraft deploys a space elevator down onto the planet. This'll probably require some preparation time. If your spacecraft has some manufacturing capability, it may harvest materials in asteroids and such to construct the cable and counter-balancing mass at +geostationary altitude (which could probably just be a raw, unprocessed asteroid tethered to the cable).
The spacecraft may aerobrake in the atmosphere if it is capable of doing so, but would need to ride the space elevator for perhaps a day or so to reach orbital altitude + velocity again.
For a fuel-less ride, the space elevator could have a matrix of solar panels at GEO for solar energy.
Option 2:
Your spacecraft deploys a rotating sky hook. Sky hooks are a type of momentum exchange tether. They are similar to space elevators but require much less cable & mass to build. They also require a large counter-balancing mass to exchange momentum with which, like the space elevator, could also be a captured asteroid. 199
Your spacecraft must simply be able to reach a target altitude & speed well below orbital and the tether carries you the rest of the way (no simple feat, but any competent spaceplane could make the rendezvous). If you don't care about the sky hook's orbit eventually decaying (possibly leaving you stranded if you can't reach it in time), you don't have to build any thrusters into it for orbital corrections (although there are a number of electrodynamic tethers that use the geomagnetics of planets for orbital corrections).
This is IMO the best option. The cable can be coiled-up and reused for later planetary excursions, and all one needs to do is find a large enough counter-mass (such as an asteroid) and to place the thing into the correct orbit.
Option 3:
You leave your spacecraft in orbit and take a hypersonic airship down to the planet. This is JPAerospace's Airship-to-Orbit proposal for space launch & return missions. A mile-long, solar-powered hydrogen airship slowly decelerates to suborbital speeds over the course of a couple days, coming to rest several miles above sea level. (The airship is delicate due to mass constraints and must remain floating in the upper stratosphere to avoid high barometric pressures and weather conditions.) Smaller balloons/airships or heavier-than-air vehicles could then deploy from the orbital airship's cargo bay to peruse the planet at will.
To return to space, the orbital airship gradually builds up orbital speed & altitude over 2-3 days using solar-powered ion engines, rendezvousing with the main spacecraft. 199