High dV rockets without Nuke/Ion and limited tech ideas

[WanderingKid]

For anyone curious, I've scrubbed the intent of the mission, though the conversation and exercise has been fun.  To pull off the mission I was building this for, which was to get to Duna and back safely before the normal Hohmann transfer window, the dV requirements are in the 15-18k range at a minimum.  It's 7-9k just to get a severely early arrival (<120 days), another 2-3k (minimum) braking in Duna SOI for a vector inversion via gravity (so you're not flying off into interstellar space), and from there it just gets awkward.  Returning to Kerbin in a timely manner is actually the hardest part of the pinball game, and can cost you a fortune.  That's a seriously awkward contract to perform.

[Ohm is Futile]

I've tried going for bad transfer timing missions with the 140T limit before and trust me it is a frustrating endeavor. Best dV values are achieved, as mentioned previously, with higher Isp engines and a higher mass fraction of fuel, but that leads to low TWR issues and a loss of efficiency in the maneuvers (and consequently, loss of dV). Even without the 140T limit, it's going to be annoying.

Best bet is probably asparagus staging, or just giving in and waiting for a better transfer window... or refueling locally by bringing mining equipment.