When the aircraft carrier USS Nimitz takes to sea, it carries more than a half-million files with diagrams of the propulsion, electrical and other systems critical to operation. Because this is the 21st century, these are not unwieldy paper scrolls of engineering drawings, but digital files on the ship's computers. The shift to digital technology, which enables Navy engineers anywhere in the world to access the diagrams, makes maintenance and repair more efficient. In theory. Several years ago, the Navy noticed a problem when older files were opened on newer versions of computer-aided design (CAD) software.So even if you keep the files successfully for years, will they still mean the same as they did originally?
"We would open up these drawings and be like, 'Wow, this doesn't look exactly like the drawing did before,'" says Brad Cumming, head of the aircraft carrier planning yard division at Norfolk Navy Shipyard.
The changes were subtle — a dotted line instead of dashes or minor dimension changes — but significant enough to worry the Navy's engineers. Even the tiniest discrepancy might be mission critical on a ship powered by two nuclear reactors and carrying up to 85 aircraft.
Imagine that history is re-written not because people decide to change the facts, but because details are lost as files become unreadable or file contents change when the software "reads" the file differently.
Technorati tag: digital preservation