> There are things we can't do yet, such as orbital insertions, with ion engines. We can do orbital insertions - if we approach a planet or asteroid with parab

> There are things we can't do yet, such as orbital insertions, with ion engines. We can do orbital insertions - if we approach a planet or asteroid with parabolic speed, we need only small change to get to an elliptic orbit, and that orbit can be later shaped as we need. What we can't do is a launch or landing with bodies with sufficient gravity - like Moon or Vesta. There we don't have time to accelerate.