Here are web sites useful for IED.
Different people have different ways to design; here's one that worked: Wright Brothers Engineering Method (4:45).
Engineering Disasters and Learning from Failure might be interesting.
Castle Bravo . Eensy teensy physics error resulted in 15MT thermonuclear blast instead of 6MT.
It's important to get the details right - 3
Stupid little details can kill people (luckily not in these stories...).