RP-1

In this vein, I highly recommend the RP-1 mod set for KSP1, which introduces (among other things) ullage and engine start failures, launching from a realistic Earth. Really gave me a huge appreciation for the difficulty of achieving orbit. https://github.com/KSP-RO/RP-0

Two recommendations for KSP1 mods, if you want progression from the base game and to learn a ton about real spacefaring history: RP-1: Realistic progression career using the real solar system, real part configurations, etc. Actually a mod pack of about 80 different mods including the Realism Overhaul base pack. Start in 1951 and build your space program. Newly updated for v1.12 (the last KSP1 minor version) and has an express install option now. Forum Page: https://forum.kerbalspaceprogram.com/index.php?/topic/190040... Wiki: https://github.com/KSP-RO/RP-0/wiki Principia: N-body orbital mechanics. Actively developed, works with the stock solar system & Real Solar System. A truly stunning achievement. https://github.com/mockingbirdnest/Principia

And then, eventually, you'll have done everything in the game... And then you'll install RSS+RP-0 [0] and struggle to get back into orbit again. The mods add a ton of depth beyond what the base game can provide. For those curious, RSS stands for Real Solar System - replacing the Kerbol system with ours. This is a large difficulty ramp, since things in our solar system are far larger than those in Kerbol, so even with the same surface gravities delta v requirements end up much higher. (For instance, ~2.7km/s is enough to hit orbit on Kerbin if flown properly, while 9.5km/s is more common on Earth) To partially compensate for this you have RP-0, a modpack that (among other things) replaces all the engines, fuels, tanks and other parts with their real life counterparts, making the higher delta v requirements actually achievable. (And also ad