THE LONG, thin pulsejet engine comes to life with a thunderous racket, prompting everyone in the garage to take a step back. The missile is called the Trembita, after the Ukrainian alpine horn. It isn’t hard to understand why. “We might miss our target,” says Serhiy Biryukov, who heads the missile’s ragtag crew of volunteer engineers, “but we’ll fly the thing so low above Russian trenches they will shit themselves.”