It can sound crazy, but these rockets use birch planks to ignite these engines. Exactly 32 planks for 32 nozzles.
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No, they are not used as firewood. Ignition system uses 32 termite charges inside nozzles atop of 32 wooden planks. After ignition wood burns immidiately. If something goes wrong termite burns through wood and falls out. Very simple and reliable, as whole rocket.
But, probably, it's the only rocket in the world which has wooden parts in ignition system.