How is the impactor propelled after separation?
The impactor, as the flyby spacecraft, is propelled by the expulsion of nitrogen, hydrogen and ammonia gases created during the decomposition of the liquid propellant hydrazine, N2H4: 2 N2H4 —> H2 + N2 + 2 NH3 Hydrazine is used because of its very fast reaction rate, allowing for the quick generation of gas.