Vesper Astro
I'm slowly working on a spacecraft design webapp: https://vesperastro.com. Think PCPartPicker for spacecraft. You can build out and trade hardware in the master equipment list and immediately visualize how any changes impact mass, power, propellant, and link margins, or break power or data interface compatibility. You can also play around with orbit and operating modes to optimize things like orbit average power. I'm hoping it can be useful in rapidly iterating early stage spacecraft designs and weighing system-level trade studies across CONOPS and hardware. Its still very much a work in progress so I'm always open to feedback.