0 7 4 0 7 4 5 9 / 0 3 / $ 1 7 . 0 0 © 2 0 0 3 I E E E After initial salvage attempts, the ship was largely forgotten until Anders Franzen located it in 1956.1 In 1961, 333 years after it sank, the Vasa was raised; it was so well preserved that it could float after the gun portals were sealed and water and mud were pumped from it. The sheltered harbor had protected the ship from storms, and the Baltic Sea’s low salinity prevented worms from infesting and destroying the wooden vessel. Today it is housed in the Vasa Museum (www.vasamuseet.se), near the site where it foundered.2 Figures 1 and 2 show the restored ship and a recreation of its sinking. Researchers have extensively analyzed the Vasa and examined historical records concerning its construction. It sank, of course, because it was unstable. The reasons it was unstable, and launched when known to be unstable, are numerous and varied. Although we may never know the exact details surrounding the Vasa, this article depicts our “most probable scenario” based on the extensive and remarkably well-preserved documents of the time, evidence collected during visits to the Vasa Museum, information from the referenced Web sites, and publications by those who have investigated the circumstances of the Vasa’s sinking. The problems encountered are as relevant to our modernday attempts to build large, complex software systems as they were to the 17th-century art and craft of building warships.