Rocket equasions

///Spend fuel and accelerate in direction
private void Thrust(Vector3 dir, float draw, float seconds) {
	o.Normalize();
	float change = GetVelocityFromBurn(this, draw * seconds);
	DrawFuelFromTanks();
	velocity += change*dir;
}

///Determine the number of seconds in order to reach velocity (assuming no friction)
public static float CalculateBurnTimeToReachVelocity(Spaceship ship, float vel, float draw) {
	float totThrust = ship.GetTotalThrust(); //total thrust in kilonewtons
	float totMass = ship.GetTotalMass(); //mass in kilograms
	float dryMass = ship.GetDryMass();
	float toBurn = totMass / (Mathf.Exp(vel / (totThrust*10)));
	if(totMass-dryMass <= 0) return -1;
	float t = (totMass - toBurn) / draw;
	return t;
}

///Determine the resulting velocity from a given burn time
public static float GetVelocityFromBurn(Spaceship ship, float draw) {
	float totMass = ship.GetTotalMass();
	float dryMass = totMass - draw;
	float totThrust = ship.GetTotalThrust();
	return totThrust * 10 * Math.Log((float)totMass / dryMass);
}

///Calculate total available delta-v
public float TotalDeltaV() {
	float totMass = GetTotalMass();
	float dryMass = GetDryMass();
	float totThrust = GetTotalThrust();
	return totThrust * 10 * Math.Log((float)totMass / dryMass);
}