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Communications of the ACM


Virtual Duplicates

engine illustration next to a shadowy engine illustration

Credit: Chesky

Back in 1970 during the seventh crewed mission of the Apollo space program (the third intended to land on the Moon), the three astronauts aboard Apollo 13 were calmly going about their duties when an explosion in an oxygen tank rocked the spacecraft, spilling precious air into space and damaging the main engine. Personnel in Mission Control suddenly had to devise a plan to get the crew home, and to do that they had to understand what condition the damaged ship was in and the materials available for repairs, and then test what the astronauts might be able to accomplish.

To figure it out, they turned to the flight simulators used to plan and rehearse the mission. They updated the simulators with current information about the physical state of Apollo 13 and tried various scenarios, eventually coming up with the plan that safely returned the astronauts to Earth. This was, some argue, the first use of a digital twin, a model that simulated the state of a physical system with real-time data and made predictions about its performance under varied conditions.


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