Everyone has a different risk point, though. If I told you that 2 out of every 100 planes crashed, most of you wouldn't fly. Yet those are pretty much the historical odds of a space shuttle crash. History is filled with people who didn't really know those odds (the early shuttle crews), and those who did - but didn't flinch (the later crews).
For the shuttle pilots, the worst case scenario was pretty clear, and the odds pretty poor, at least compared to commercial aviation. So why would they fly? Simple - a clear visualization of the best case scenario. Even not knowing the real odds, like the early shuttle pilots, or the first explorers, is no impediment if the upside is a clear and compelling vision, like a view of the Big Blue Marble you and I will never see.
When the best case scenario is a vivid manifestation, I think we humans will accept all kinds of risk, even the risk of not knowing the risk. It's the opposite scenario that is more troublesome. Let's stipulate that you know the odds (they aren't good) and you know the worst that can happen (a crater). Would you take the risk if you didn't have a clear vision of the upside?
The real risk is this: if you wait to get on that plane, you might miss the flight of your life. But it's a different kind of risk - not the risk of a negative outcome, but the risk of missing a positive outcome, which frames the problem in a completely different way
If you had no clear picture of what the destination looked like, would you get on that plane?
How much would you need to know?
I don't have the answer to this.