I was wondering how verifiable is the escape velocity equation. V=SQRT(2GM/r) How accurately has this equation been verified? It does not take into account dark matter. (Related ramblings) The escape velocity from the earth’s surface is about 11.2 km/s But there is also air resistance. How much extra velocity (above 11.2 km/s) is required to escape Earth’s gravity? I am not after a specific value, I would just like to know if the energy requirement increase is significant or not. How much leeway in terms of fuel does NASA give when firing rockets into space?