Still surprising to me. I also read up on the BOPs a bit--very interesting. I would have expected a last ditch line of defense consisting of some sort of powe

Still surprising to me. I also read up on the BOPs a bit--very interesting. I would have expected a last ditch line of defense consisting of some sort of powerful spring-loaded ram with a maybe an explosive and/or mechanical trigger, so that if everything goes wrong, you can hook up a sub and yank something to clamp the stem, even with no hydraulic lines connected. Not that the annular BOP isn't a clever design, using the well pressure against itself to clamp down tight.