Using a rubber raft made of 55 raincoats, three Alcatraz inmates broke out of the maximum security federal penitentiary before the morning bed check on June 12, 1962. Whether they survived and floated to nearby Angel Island during the night, or if they were swept out of San Francisco Bay and into the vast Pacific is still a mystery. According to a new computer simulation of the bay, the escape may have been a success—but only if they left during a narrow window of time around midnight. The findings [pdf] were presented at the American Geophysical Union fall meeting in San Francisco this week.
The three bank robbers spent about six months preparing for their escape—loosening air vents, making life vests and periscopes in a secret workshop, and routing their getaway. On that foggy June night, they left dummy heads fashioned from plaster and hair in their beds before shimmying their way to the shore of The Rock. (Original FBI records and photos can be viewed here and here.)
A Dutch team of researchers were developing a model to study the impact of sea-level rise in the bay when they realized the 3Di hydraulic model could also help visualize the famous prison break—which has previously been dramatized by Clint Eastwood and recreated on MythBusters. They reconstructed the bay’s hydrodynamic conditions, combined that with decades-old tidal records, and then used particles to simulate the movement of the raft.
In particular, they looked at two scenarios: a worst-case scenario with no paddling (or where paddling was ineffective) and a best-case scenario where they paddled northward at the speed of 25 centimeters per second. “We didn’t know exactly when the inmates launched their boats, or their precise starting point, and so we decided to release 50 ‘boats’ every 30 minutes between 2000 and 0400 from a range of possible escape spots at Alcatraz to see where they would end up,” Fedor Baart of Deltares says in a news release. Check out the animation of the simulation (a screenshot is below).
“If the prisoners had left before 2300, they would have had absolutely no chance of surviving,” Baart says. And if they entered the water in the very early morning hours, they would have been pushed back into the Bay and depending on the way they were paddling, they would have been sent northwards towards Berkeley and the mouth of the Sacramento River or pushed south towards Oakland, past Treasure Island. "In both cases they would have spent so much time in the water, they probably would have died of hypothermia,” Rolf Hut from Delft University of Technology tells BBC. “Or they would have been picked up by the police because sunrise was at 0600.”
However, if the escapees launched their raft just before 2300 up until around midnight—and they paddled northward—they could have made it to Horseshoe Bay in Marin County at the northern end of the Golden Gate Bridge. The model predicts that any debris would then float in the direction of Angel Island, which is where a homemade paddle and some personal belongings were discovered by FBI at the time.
Images: Maciej Bledowski (top), siggyf (middle)