Over at the NASA web site there is a wonderful picture of a very sad event – Atlantis being moved to the pad for the last launch ever of a space shuttle. I call this event sad rather than bittersweet only because there is no replacement vehicle. I can’t deny that the shuttle needs to be retired; it has served honorably, for far longer than anybody had a right to expect. It really should have been taken out of service twenty years ago. But twenty years ago, NASA didn’t have anything to use in its place. Sadly, they still don’t.