Plague in Space is an achievement . It talks about Gill Bates believing that an asteroid with alien DNA can cure the disease. So, in order to find this asteroid, he sends some men that are considered healthy to space to find the cure. However, the men will all have already been infected, and they will all have died in space, making the mission an absolute failure.
How to get this achievement?
For strategies and tips, please see Strategy guide/Plague in Space.