^ "So far I've come across no technical reason that the probe could not have been designed around RTG power from the start."
If I recall, the Chernobyl and Challenger disasters were still fairly fresh in the public's mind and "Nuke=Bad" was still the mindset. What if this here now nooculier stuff blew up on the launch pad or in the atmosphere and contaminated all of Gaia with that there polonutonium 295 stuff, hey? What about that?
May have been a factor in the decision, given the tenor of the times.
I was really disappointed that this turned out the way it did, but we've had failures before. I am amazed that we could plunk something down on a comet (like the Deep Impact project) in the first place.
All I can say is what my Pop used to say when something went cattywumpus: "Well, you can't lose 'em all."
Terry
REF:
http://www.cnn.com/2005/TECH/space/07/04/deep.impact/index.html?_s=pm:tech