Physical Twins, Digital Twins, and the Apollo Myth

As I have been reviewing Digital Twin (“DT”) articles over the last few months, there are no lack of articles that claim to track back the Digital Twin to NASA and the Apollo program. Googling “Digital Twin and “Apollo” results in 60,000+ results. There is actually a strong connection between NASA and the Digital Twin. While I introduced the Digital Twin model first in automotive industry settings, I was a consultant to NASA for many years. Modeling and simulating spacecraft was instrumental in thinking about the Digital Twin and its entailments. 

The NASA colleague that I worked with, John Vickers, did take the inelegant names I had at the time for the DT concept and coined the actual “Digital Twin” name[1]. He also introduced the Digital Twin within NASA in his 2010 roadmap. I authored a paper with my NASA colleagues for a 2010 Defense Manufacturing Conference (DMC) that was based on the Digital Twin concept. The version of the Digital Twin model that I developed during my NASA time and that is commonly seen today contains rocket related images. 

However, as amazing as the Apollo launches were, there really wasn't much Digital Twin or even digital in those efforts. The Apollo 13 voyage is generally the focus of articles tying Apollo to the Digital Twin. While the bringing back Apollo 13 safely to earth might be the most amazing malfunction recovery story ever, it had little to do with the Digital Twin. 

I have had the privilege of meeting Commander James Lovell and hearing first-hand the amazing story of two astronauts sitting on what was basically a couch in the Apollo capsule, lining up the earth’s meridian vertically and horizontally so that they didn't burn up or bounce off into space at re-entry. The success of Apollo 13 had to do with the intelligence, coolness, and bravery of the astronauts and little, if anything, to do with “digital”.

The “twins” involved in this heroic saga were the physical twins of the spacecraft. The plan to recover functionality and get Apollo 13 home safely was also a critical effort by very talented NASA engineers. Their proposal of work arounds and recovery were validated with physical simulators. The simulators were physical counterparts to the actual Apollo spacecraft. There were some digital aspects to them in that they were running primitive computers with the same programs as the actual spacecraft itself. However, these physical space capsules clearly weren’t Digital Twins.

Physical twins, even if primitive, rudimentary, and abstract, have been used in human endeavors for all of human existence. Prehistoric man undoubtedly sketched in the dirt with a stick a representation of the herd of mastodon, the cliff that they needed to be driven over, and the positions of his fellow hunters. While military sand tables date from the 1800s, equivalents date back to ancient Greece military use and most likely before.

Architecture has used physical twins from earliest times all over the world. Physical twin artifacts have been discovered dating from at least 6,000 BC. Physical twin model making was prevalent in ancient Greece. The making of physical twin models to represent the actual physical buildings existed throughout the world in all cultures.

The physical twin models were even dynamic and not simply static. Watch any movie about 20th century war. It will generally feature a table with a geographical map that people will move around representations of military and naval forces. As dispatches come in, people move these representations into different geographical positions so that commanders can assess and plan their next strategic and tactical moves.

But it wasn’t simply scale models that were physical twins. Full scale physical mockups have been created and used. Full scale physical twins have been used in military preparation as long as military engagements have existed. The D-Day preparation included exercises on Scotland beaches that were the physical “twin” of Normandy Beach.

For equipment and vehicles, physical twins were used primarily in development. However, physical twins were also used to resolve issues with operational equipment and vehicles. Airplane manufacturers used physical twins to recreate and troubleshoot reported problems with their airplanes in the 1930s. When problems were reported with automobiles, it was standard operating procedure for the engineer working on the problem to find an identically configured automobile to try and recreate the problem.

As we developed electronics, we could make these physical twins dynamic on their own. The company I worked for in the 70s, Lear Siegler Corporation, had an F-16 flight simulator in its Grand Rapids Instrument Division. It was physical, not digital. There have been dynamic physical twins of nuclear reactor control rooms for training and emergency exercises for over 50 years.

Physical twins have been in existence throughout humanity’s history. Physical twins have been abstracted in such representations as dirt sketches and sand tables. Physical twins have been realistic scale models such as buildings and even cities. Full scale physical twins have been used to prepare for military battles. Physical twins have existed dynamically as in the F-16 simulator and the Apollo space capsule.

As we developed digital technologies, it was inevitable that we would move the concept of using replications or twins into the digital realm. Trading off bits for atoms to substitute information for wasted physical resources as bits get cheaper and atoms get more expensive makes great economical and efficiency sense. This information is developed from Digital Twin modeling and simulation in the three types of Digital Twins. Those three types are the Digital Twin Prototype (DTP), Digital Twin Instance (DTI), and Digital Twin Aggregate (DTA).

The development of the Digital Twin does have a strong connection to NASA as described above. However, the claim that the Digital Twin originates in the Apollo program is unfounded. It is an attractive myth, but it is a myth, nonetheless.

#digitaltwin

[1] The model started off without a name and was the “Underlying Premise for PLM.” I initially named it the “Mirrored Spaces Model”, then the “Information Mirroring Model”, and even “virtual doppelganger” before finally adopting the name that John Vickers coined for it, Digital Twin.