I'm working on designing various rockets, for research purposes.
I want to get a feel for the actual math and engineering that goes into designing these vehicles from the ground up.
So far I've been able to mathematically design a suborbital rocket that should in theory reach the edge of space.
However I kind of came up with the design process in a way that seems entirely backwards.
I started with an engine design, since the most detailed documentation I could find was about engines and thrust generation. I was able to design a liquid bi propellant 250lbf engine(most documentation is old nasa work which was done in lbs) then I built the rocket up around that, knowing that I wanted an initial TWR of 1.7 I knew the rocket could weigh around 147lbs when full, and since I wanted a Delta V of 1.5km/s and the engine had an ISP of 300 that the empty rocket had to weigh 88lbs.
This method is perfectly fine for a high power rocket experiment or demonstration. But it seems backwards for practical use.
rockets usually carry a payload, I'm wondering what a better process would be if I started knowing the payload mass. And worked down the rocket similar to the way rockets are built in KSP.
Lets say I start knowing my payload mass and where I wanted it in space. For instance 5kg to LEO
LEO delta V is about 10km/s by my understanding. And for simplicity the rocket will be two stages.
So how would I work from the payload mass down the rocket instead of from the engine up the rocket?
