Drop Bomb

Refuel 1: put 1 cards from your scrapyard on the bottom of your hold, in the order you choose. With fewer than 1 there, you can't pay it. It keeps your hold from running out; the cards aren't salvaged, so they don't count for the Sapper engine (802.8). Besides the steam, you exhaust one of your Dirigibles that isn't dispatched when you deploy it. It stays exhausted until your next stoke phase. A crew that came on board this turn can pay it too (306.5).

Choose a base on board, either player's, or a battle with crew in it, when you deploy it. A base takes 3 damage, which stays; a base left with no hull is destroyed at once. In a battle, every crew there as this resolves takes 3, yours too, plating first; those left with no hull are destroyed. In a watch no crew is dispatched, so only a base can be chosen (705.7h).