Modernizing the armed forces is a slow, costly, and risky process. From a certain point of view, we are not surprised to learn that Germany still uses eight-inch floppy disks, but at some point new technologies must be evaluated, and that is exactly what the cruiser USS Yorktown did in September 1997. As part of the Smart Ship program, the Yorktown served as a test bed for a new digital control system… that ended up dividing by zero, and was left stranded off the coast of Virginia for nearly three hours.
The cruiser USS Yorktown (CG-48), a Ticonderoga-class ship, entered service on July 4, 1984. Available information indicates it was specially designed to take full advantage of the Aegis combat system, which combines computers and radars for weapon guidance and tracking. The Yorktown had some high-profile interventions, including the interception of the Achille Lauro (hijacked by terrorists in October 1985) and several operations in Libya.
With a crew of 33 officers and more than 300 sailors, the Yorktown operated within expected parameters and received multiple decorations. However, in October 1995, the NRAC (Naval Research Advisory Committee) published a study recommending exploring different strategies to reduce crews and, by extension, operating costs. Two months later, the Smart Ship Program Office was created with the aim of incorporating new technology to reduce the number of crew members without sacrificing combat performance or capability. The cruiser chosen… was the USS Yorktown.
USS Yorktown and a three-hour divide-by-zero
Bishr Tabbaa explains on his blog that a year later, in December 1996, the Yorktown received the first functional prototype of the Smart Ship system. Built by Litton Industries, it consisted of a LAN of 27 dual-Pentium Pro 200 MHz terminals connected via fiber optics to a server. All Smart Ship machines used Windows NT 4.0, a relatively young operating system at the time (the Workstation version had debuted in August, and the Server one in September).
Projected savings were about 2.8 million dollars annually (considering a reduction of 44 crew members and multiple redundant manual operations). The Yorktown successfully completed a five-month mission in the Caribbean and several exercises alongside the USS George Washington. However, on September 21, it was conducting exercises off Cape Charles, Virginia, when a crew member detected a discrepancy in a fuel valve.
The valve was physically closed, but the SMCS (Standard Machinery Control System) module of the Smart Ship system said it was open. The technician decided to initiate a digital recalibration of the valve, entering the value 0 in one of its properties with the help of the Remote Database Manager, or RDM. The problem was that RDM tried to initiate a division operation on that new value, effectively dividing by zero. The RDM module hung… as did all other systems that depended on it. The domino effect reached propulsion, and the poor Yorktown was left floating, inert.
In 2 hours and 45 minutes, the Yorktown's crew managed to restart the entire system and return to their base in Norfolk. Tabbaa's blog also explains later incidents, contradictions, and other false details such as the Yorktown needing to be towed. This was denied by the ship's own captain, Richard Rushton, who added that it "was not the first time" the RDM hung due to incorrect parameters. Other sources pointed to Windows NT 4.0 as responsible for the failure, but once again, Captain Rushton denied that the operating system had caused problems.
The Yorktown continued its tests, returned to active service in September 1999, and was retired in December 2004.
(Editor's note: Bishr Tabbaa published other similar failures in his book "Bugs: A Short History of Computer System Failure").
Access the full article: Click here
