The ion engine was for emergency situations, if the interplanetary drive ceased to function; the ion engine would get me some where one way or another. Facts: The interplanetary drive had actually ran out of fuel before I managed to get into a proper orbit and so decided to go for a head on trajectory with eve, yet was still successful due to deploying the parachute a bit too early in hope that the heat shield was big enough to protect it as it trailed behind the probe.