A friend of mine (through DECUS symposia) who work(ed?) at Sandia National labs told me about what they did with them... There would be a pdp-11 down the hole with the device, connected via Ethernet to another pdp-11 with core, topside in a van. When the device was set off, the signals from the now-very-fried-11 would race the fireball up the hole where the data would be stored in core. (The speed of the advancing fireball could be somewhat determined by using TDR on the ethernet cable :-) When the shockwave hit the van, it would go bouncing across the desert until it came to rest. If was able to, it would continue recording information. If not, they came along at a later time and pulled the core plane and installed it in another machine where they would try to read it.