Interstellar Relativistic Rocket Calculator

This first calcuator tells you how long it would take to get to interstelalr destinations with certain ammounts of Delta-v. It is based on the 100 year proposed journey of the Nauvoo from the Expanse using fictional Epstein fusion drives. Which would require 72,000 km/s of Delta-v to arrive within 100 years. How you get that much Delta-v is up to you. The math on this is a little sketchy because it's simplifying some things, and because I'm not a rocket scientist and used Claude Sonnet to write most of this. Let me know if you find any mistakes. Canon specs from here and here.

However, I want to make a tool to solve a different question. And, as usual, the difficult part was figuring out the right questions to ask. The question I want to answer is this:

"How efficient does a rocket engine need to be to travel interstellar distances in a reasonable amount of time?"

I think the best metric to answer that question—agnostic of propulsion technology—is the fuel conversion rate. There's various factors that go into how efficient fusion drives are at producing energy: Power Efficiency, Q-Factor, Thrust-to-Power ratio. But those are all specific to fusion as a technology. I want to answer how efficient does a rocket need to be at converting matter and energy to momentum. Specific Impulse, how much thrust is generated per unit of propellant mass flow rate, is another likely metric to use, but I think fuel conversion rate is more fundamental. But I'm not a rocket scientist, and I haven't been able to find any reputable sources yet. If you have suggestions, please let me know.

This is close. It is based on this script by Nathaniel Effen.