What happened with this one? Looked like a promising project.
Still working on this one, just extremely slowly. Just revised a lot of the details in the systems design because some decisions made operating this spacecraft harder than it was necessary. For example, I decided to make the cargo bay on the spacecraft only for EVA tools and spare parts - operating close to a space station with a hot reactor is pretty much impossible without harming the people in the space station, unless you are really restrictive on the maneuvering. So, cargo transport should better be primarily by pushing cargo containers - more focus on the tug aspect.
Another research problem is finding a way to squeeze the maximum amount of burn-time out of the Uranium. Right now, it condenses pretty much to the following equation: More maximum thrust to weight (on hydrogen alone) = more DV. I can't get more heat energy out of 100% enriched Uranium per kg of fuel rod, so the only option to scale things for longer life-time is to make the powerplant larger. I still hope to be wrong, but 40% enriched and a small light reactor size results in: Only one flight to the moon and back and you already need refueling. I hope to find a sweet spot somewhere at three round-trips.
