Im pretty sure i figured out your mistake since I got a v1 of 278m/s and a v2 of 242m/s first off your μ is wrong according to the wiki the gravitational parameter of Kerbin is 3.5316000*10^12 m^3/s^2 which will throw things off second and im not sure if this will really cause too much error but i also added the radius of Kerbin which is 600,000m to r1 and r2 so they are r1 = 700,000m and r2 = 1,200,000m I also kept everything in terms of meters instead of converting to km then back to meters