Why is it less expensive to send robots into space than man?

because they no need food cloth and shelter .They easily live on the space without air or any other problem.

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Because robots don't need air, food, water, reading material, music, clean clothing,

or toilets. Also, since the PR is so important to the space program, it's not so

important to make provisions to bring the robot back, and it's not so serious if the

robot fails and dies during the mission. All of these facts combine to make the

payload at launch considerably lighter.