A real one from sailing ship days. Was small, barrel about half a meter long and massing, with wooden carriage, only kilos fifteen. A "signal gun" its papers said. Reeked of ancient history, pirates, men "walking plank." A pretty thing but I asked Prof why? If we ever managed to leave, price to lift that mass to Luna would hurt—I was resigned to abandoning a p-suit with years more wear in it—abandon everything but two left arms and a pair of shorts, If pressed, might give up social arm. If very pressed, would skip shorts.