Hume- pool ball Dotto

Hume says before you have an observation you can't rule out any conceivable outcomes. While that is reasonable I began to wonder the opposite and how people begin to venture into the unknown. I still do not understand how NASA knew that they could launch a rocketship not only off the ground, but also miles into the sky, through the atmosphere, through space, land on the moon, launch from the moon, fly though space again, fly back through the atmosphere, glide down to earth, and finally land. There were so many variables and one single miscalculation, or wrong estimate could have resulted in failure. How could NASA know that space wasn't so highly pressurized that it would crush the ship like a tin can? How did they know that their suits would hold up to the direct sunlight, temperature, and pressure? and most astoundingly, how did they know that their ship could not only land on the moon, but take off back to earth as well, especially when you consider the lack of oxygen in space which is needed for the combustion of an engine? Somehow NASA scientists were able to rule out these factors before they ever had any real-world data and experiments under their belts.

If Hume was correct, in that our knowledge is a posteriori, then how could astronauts know any of the necessary data for space travel, when there was no prior explorations in the 1960s for them to refer to? Perhaps this is a cingular example, but it may hold some deeper meaning.