It is gratifying to see ion engines coming of age. The concept has been around seemingly forever. Of course it illustrates how much work is involved to go from vaporware concepts to something real and practical. I'd say more than a few material advances, and a whole lot engineering have finally payed off.

I was just reminiscing back 40 or so years for myself. I remember that ion, fission, and fusion engines were all part of the mix. I never dreamed that it would take 40 years to advance beyond the specific impulse of chemical rockets. And of course we still haven't figured out a better way to get beyond the earth's gravity well.

I sure hope I am still around when there is the inevitable leap forward that will change the game. I don't know if it will be a space elevator, pneumatic launch, external laser assisted, or what. But I have faith we'll figure something out.