This Jim Martin sketch was identified in an issue of Star Trek magazine as an early design for a possible Voyager.
If I remember correctly, there were rumors that a "Ambassador-style Oberth had been designed but not built for Pegasus. So, could this design be for a new Pegasus rather than for Voyager?
No, this was definitely a Jim Martin sketch for Voyager. Richard James, our production designer, had artists other than myself contribute designs for the exterior of the ship and this was one of them. As far as the Pegasus was concerned, yes, there were a few sketches of a ship done, but to make it easy on the VFX folks it was supposed to be a kitbash of sorts from either a Nebula or an Ambassador (I don't have the sketches handy, so I can't recall exactly). For whatever reason, probably time/money, the Oberth miniature or a copy served as the Pegasus. As far as the Tsiolkovsky was concerned (mentioned earlier), I still don't believe that there was to be another new ship model designed, but that's only from my perspective in the art department.