Thought. Could ultrasound show the insides of the door?
Tricky. Most of the sound would be reflected by the first inside surface. You have to preserve energy with a continuous sound wave, energy and momentum with a shockwave. and there is no good way of matching the impedance of metal to air. Fill the safe with any of the low temperature metal alloys such as Woods Metal, and you might get somewhere. But that’s a lot of stuff to carry about.
What about xray backscatter? Or neutron backscatter (probably not as it’d work poorly on ferrous alloys)?
The locks in the document safes at a certain MoD establishment I used to work for had a lead addition to the lock, with deep concentric circles. Apparently this was in case someone asked you to lock up a radioactive source for them, then they taped film to the outside of the lock. I don’t know if anyone had ever done that, but this was supposed to make it very hard. Neutron sources might pick up on the grease in the lock, as they are crankily sensitive to low-Z materials, and an edge coated in grease might show up well. But you would probably have to have the neutron source inside the safe to get a sharp resolution.
If we get strong enough xray source, could we shine through the whole safe and the wall it is mounted on? How strong source would be needed?
The devil is again in the detail. The nice thing about sticking the radioactive source inside the safe is that it minimised the scatter. If you have a big burst of X-rays and you are trying to see through 100 g / cm2, then you are likely to get as much signal back from backscatter from the walls of the building as you will get from X-rays getting through the safe itself. You can correct for this to some extent. The most penetrating radiation you are likely to find would be Cobalt 60 at about 1.2 MeV. Lower energies do not penetrate so well, while higher energies have losses due to electron-positron pair production.
Time-of-flight acoustic tomography might work. But these locks are mostly circular elements on a shaft. You could detect a notch in the circle, but it would be much harder to say which way it was pointing. However, you can move your sound source either side of the shaft, which may give some resolution.
No, I didn’t. There was other stuff in the safe in the film, and most of that was reduced to slag (see other note about thermic lances) but the object was in gold, and so would still be of value if a bit fused. In the MythBusters version, the safe was mostly empty. Good programme, though.
“We haven’t even come close to opening the door and already the loot, including my prize scepter, is already mostly destroyed.”
In the film the sceptre is only worth anything as the sceptre itself, not as a chunk of gold. If that was the case they’d just hand him some much-easier-to-procure melted gold of the correct weight and call it a day.
What is on the back side of the safe? Another wall, a room, outside wall, John Malkovich’s brain?
Myself, I would try to open it to see if it is serviceable.
I think it would be fun to go online and try each “Safe Cracking Method” listed and film your results.
But as someone who is a Locksport hobbyist, sometimes I buy padlocks at the flea market without keys or combinations and the lock is just no good and broken.