Re: I haz a disappoint
"You have to counter out (most of) the Earth's orbital speed around the sun,"
Once out of the earth's gravity well you can (as you rightly said) use ion drive.
Size of the probe isn't that important. The heavier it is, the longer the ion drive needs to run, that's all (assuming you don't run out of reaction mass)
The good thing about heading sunwards is that you can be sure of your supply of photons. Solar panels rapidly lose effectiveness when you go on the other direction.