[Mark Sheridan]

I thought the Spirit and Opportunity robots had exact copies on earth for NASA to test with (one could call it practice) before having Spirit and Opportunity try it for real. Someone correct me if I am wrong. With aerospace, one cannot afford to make mistakes. You have to test before to be sure (often many times before).

Practically, I think all industries have some sort of equivalent of the practice robot. If an engineer receives a customer complaint or wants to improve the product, he or she should have a copy of that product to replicate the complaint or identify a potential improvement.