Cosmo. Don't worry, I downloaded your line of small dashes ok. As you say, quite often one thread leads to another. e.g. Stuart has often already done the extra bit when he does his bit on ships for suddenly there's a whole new bit about the reason & history, just as interesting; sometimes more so. Very interesting article about fuses. Don't forget explosions, being mechanical, are not in fact as we think of them, "instantaneous", just VERY rapid burning. We're talking thousandths of a second, which is very short. eg, the V2 has gone 1m in 11/4 thousandths of a second, whereas WW1 shell travels 1m in 2 thousandths of a second from the start of the burning process. Designing such a thing- where do you start? Must be done by trial & error methinks.