Fun story, but yes, awfully illogical science. 

To WHERE are the three astronauts hoping to escape? If they are on an alien planet, it's likely that outside their prison, the atmosphere (and perhaps even gravity) are nothing like on earth. They'd most likely die if they did escape.

Even if they survived, HOW did they plan to return to earth?

And WHAT did the aliens expect to learn from observing the captured astronauts that they couldn't learn simply by observing billions of Earthlings back on Earth?