Refined Kerbin delta-v Launch 1500 m/s Up, 3000 m/s Gravity Turn

[AuoroP]

Cross posted to r/KerbalSpaceProgram.

If you like to budget your designs on delta-v there are two outstanding questions about the delta-v you need to launch from Kerbin: how much deltaV for primary ascent and how much for a gravity turn.

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For the TLDR folks, the answer is in the title: a stage delta-v of 1500 m/s gets you moving straight up at terminal velocity and your fuel runs out around 12 km. The accepted answer for a Kerbin launch requires 4500 m/s so the gravity turn will require 3000 m/s = 4500 m/s - 1500 m/s.

So if you're still around you'll probably be interested in specifics about the methodology. Obviously, this is pretty easy. Design a single stage ship with just enough fuel to get it past the 12km lower atmospheres bar.

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Recipe: 6x OX-STAT solar panels (top and bottom) above a Stayputnik pod. Below that we add 3x Z-200 battery rings. Below that a TR-18A decoupler. Below that a FL-T100 fuel tank with Lv-909 engine. The atmosphere Isp for the LV-909 is 300 s. Then add another 6x Z-100 batteries. The total mass is 1.28 and the dry mass is 0.78. The stage delta-v is 1450 m/s.

I happened to conduct this research before I saw Scott Manley's adjustment video for gravity turn tutorials and learned that my target of waiting for barometric pressure to drop to 10% at 11.7 km for starting a gravity turn is too late. I did more testing and discovered that 1200 m/s gets you up to 8 km and it is possible to complete a lazy (did not move prograde fast enough) gravity turn into a circular 75 km orbit with only 3100 m/s in the second stage. 3000 m/s is enough to put you mostly in orbit and yet keep your second stage from turning into space junk.