I will offer you a simple design (thought) process for weapon making from real life experience:
1. A certain enemy port city receives and sends hundreds of ships every month. These ships carry materials that our enemy needs to survive and make war against us.
2. We want to interrupt this flow of material.
3. There is a narrow passage between the port city docks and the ocean through which all ships must pass.
4. We decide to try to sink one or more ships in the narrow passage, thereby blocking all incoming/outgoing ship traffic.
5. We have submarines we could deploy into the passage, but no suitable weapon. A pressure-sensitive mine, if placed in that path of the ships, could sink a large ship blocking all large ship traffic.
6. Our defense department describes the exact weapon performance specification desired (for instance, the weapon would not detonate unless a very large ship passed overhead) and solicits bids from known weapons makers to design and construct the weapon.
7. A demonstration/test program allows each company to demonstrate their weapon’s performance. One company “wins” the competition and receives a contract to supply some number of weapons.
8. Upon delivery to the Navy a submarine carries the weapons secretly to the passage and plants them strategically on the ocean floor.
9. The next large ship entering the passage detonates the mine and sinks, blocking the passage.