Laika

I just found out about Laika from a comment on a 9gag post. She was a stray dog from the Soviet that became the first animal to orbit the Earth as well as the first to die in an orbit. :(

Before the launch, one of the scientists took Laika home to play with his children. In a book chronicling the story of Soviet space medicine, Dr. Vladimir Yazdovsky wrote, "I wanted to do something nice for her: She had so little time left to live."

Laika likely died within hours after launch from overheating, possibly caused by a failure of the central R-7 sustainer to separate from the payload... After approximately five to seven hours into the flight, no further signs of life were received from the spacecraft.

Sputnik 2 was not designed to be retrievable, and Laika had always been intended to die. 

Seriously, what happened to the dog was completely unacceptable. I don't know if it is justifiable to compare this to animal testing, but I feel that all lives are equal. If you don't know whether it is safe to send a human into space, then don't, for goodness's sake. Just stay on Earth. Why send a poor dog out there? I can only imagine how frightened and confused the dog must have been, being trapped in the small spacecraft and heating up with no means of escape. Damn.

From Wikipedia (http://en.wikipedia.org/wiki/Laika)