The rocket engine is actually decades old. The engines were built many years ago, then stored under a tarp in a Russian facility somewhere. They were supposed t

The rocket engine is actually decades old. The engines were built many years ago, then stored under a tarp in a Russian facility somewhere. They were supposed to be dismantled, but some Party official risked his neck by sparing them the destruction, hiding them in some forgotten facility - however, the flip side to that was that the engines were stored in probably not the best conditions. Orbital used them because they were the cheap option.