In the tv series Chernobyl they show the helicopters putting sand and boron over the core of the reactor, but it was pretty dangerous. Just was wondering, why didn't they build something like a catapult to fling over the sand and boron? The guy said they needed 5000 tons of it. Is building a catapult hard, or is it just hard to build quickly that could do the job properly? The helicopter scene said it was 30 hours after the explosion.