Hi Guys,
There are issues with Tantalums. From my perspective (and I could be very WRONG!!!!) Lyle, and Chuck Green are AMSAT's corporate knowledge on space-suitable components. We should make no changes without consulting them, and possibly Jan King as well. Lou McFadin may have some useful insight, also.
Don't look for consensus on this topic. Like most subjects, you can find "experts" to support any position you want to take.
We've used a lot of Tantalums with good success. My choice is to use Tantalum rather than Electrolytic whenever possible. But I lay out PCBs and populate them, hence my bias. I don't normally have to make the circuit work.
The position taken by Karl Meinzer is that you should never use Tantalums. The argument I have heard to support this is that the failure mode of a Tantalum is a short. Of course, depending on the circuit, if the capacitor fails, it might not make much difference what the failure mode is. But for many circuits, if the capacitor fails, the circuit will probably keep working if the capacitor does not short. I have read that this is no longer a problem for modern parts (newer than about 10 years) because it is no longer the failure mode. I do have one recent experience with this when I put a part in backward which resulted in the predictable explosion. The failure mode... shorted.
Note that the filter capacitors on the CAN-Do! are not Tantalum (except one). This is because of Karl's rule. He did allow the one when we severally de-rated the voltage rating.
Electrolytic capacitors have their own problems. The biggest is their tendency to dry out, especially in a vacuum. We address this by sealing the open end of the can. Yes, this creates the potential for an even bigger bang, but we haven't seen this yet. Epoxy has been used. I also use the conformal coating for this purpose as appropriate. You are not likely to use conformal coating on an RF circuit because of the bad things it's dialectic constant will likely do to your carefully tuned circuits.
My advice is to choose the technology that best suits your needs. They both work and we have a lot of success with both of them when we take precautions as described above.
Chuck