Reading the personal accounts of astronauts does not reveal much in the way of "adventure" as that idea has been generally understood. On the contrary, the historical and personal record reveals that astronauts are highly trained technicians whose primary motivation is not to "boldly go where no one has gone before," but rather to do *exactly what is necessary* and above all *not to mess up the hardware.*
Astronauts are not like Lewis and Clark. Astronauts are the tiny peak of a vast human pyramid of earth-bound technicians and mission micro-managers. They are kept on a very tight (*necessarily* tight) electronic leash by Ground Control. And they are separated from the environments they explore by a thick chrysalis of space-suits and space vehicles. They don't tackle the challenges of alien environments, hand-to-hand -- instead, they mostly tackle the challenges of their own complex and expensive life-support machinery.
The years of manned space-flight have provided us with the interesting discovery that life in free-fall is not very good for people. People in free-fall lose calcium from their bones -- about half a percent of it per month. Having calcium leach out of one's bones is the same grim phenomenon that causes osteoporosis in the elderly -- "dowager's hump." It makes one's bones brittle. No one knows quite how bad this syndrome can get, since no one has been in orbit much longer than a year; but after a year, the loss of calcium shows no particular sign of slowing down. The human heart shrinks in free-fall, along with a general loss of muscle tone and muscle mass. This loss of muscle, over a period of months in orbit, causes astronauts and cosmonauts to feel generally run-down and feeble.