Answer:
Do you mean why animals are better to send to space than humans? Animals do not comprehend what is going on so they are not worried or scared to die in space. They also do not have the same level of IQ as humans so humans are worth more if you saw it from that point of view. I know this can be debated however.
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Ok I see you posted a comment saying "Robots"
Robots will not die if there is an explosion because AI does not have a mind of it's own.