Industrial synthesis of hydrazine
The Kirk-Othmer Encyclopedia of Chemical Technology reports that: "About 60% is made by the [Bayer] hypochlorite–ketazine process, 25% by the peroxide–ketazine route, and the remainder by the Raschig and urea processes." Here is a link to the original article, if you can access it (e.g. at a university library): Hydrazine and Its Derivatives, by Eugene F. Rothgery. The data cited dates back to 2004, so it may have changed somewhat, but probably not too much.

Consider this also: the above makes hydrazine hydrate. Propellant-grade hydrazine must be anhydrous, so there is an extra step in which water is removed from the hydrate, typically by azeotropic distillation with aniline.