declare function CalculateCircularizationDV{
	parameter ap is 0, sma is 0.
	local mu is body:mu.
	if ap = 0 {
		set ap to apoapsis.
	}
	if sma = 0 {
		set sma to orbit:semimajoraxis.
	}

	local apR is ap + body:radius.
	local circVel is sqrt(mu / apR).
	local apVel is sqrt(mu * ((2 / apR) - (1 / sma))).
	return circVel - apVel.
}