In TNG and DS9, we often see the use of shuttles and runabouts. What is the deciding factor of which one to use? How come we only see one use of a runabout in TNG? Is it only about the crew size on board? Yet shuttles have been shown to carry quite a number of people too? Is it speed?


Question: Can hybrid Vulcan/Humans procreate, or are they like mules?
Answer: In the Star Trek novel "Yesterday's Son", Spock discovers that he fathered a son with Zarabeth when he was stranded in the past in the 'All our yesterdays' episode. So a male hybrid produced by a Vulcan male / Human female can be fertile with humans.

http://en.memory-alpha.org/wiki/Yesterday%27s_Son