 These blades caused the rockets to become very unstable towards the end of their flight, causing the blades to spin around like flying scythes, cutting down all in their path.Congreve began in 1804 by buying the best rockets on the London market, but found that their greatest range was only 600 yards.After spending "‘several hundred pounds’" of his own money on experiments, he was able to make a rocket that would travel 1,500 yards.