A Critical History of Electric Propulsion: The First 50 Years (1906-1956)

Abstract

A = beam cross-sectional area a = vehicle acceleration i ≡ p/V = current per unit vehicle mass j = current density Mv = vehicle mass m ̇ = propellant mass flow rate P = input electric power p ≡ P/Mv = input electric power per unit vehicle mass T = thrust uex = rocket exhaust velocity V = voltage η = thrust efficiency W HEN writing history, it is tempting to identify thematic pe-riods in the often continuous stream of events under review and label them as “eras, ” or to point to certain achievements and call them “milestones. ” Keeping in mind that such demarcations and des-ignations inevitably entail some arbitrariness, we shall not resist this temptation. Indeed, the history of electric propulsion (EP), which now spans almost a full century, particularly lends itself to a subdi-vision that epitomizes the progress of the field from its start as the dream realm of a few visionaries, to its transformation into the con-cern of large corporations. We shall therefore idealize the continuous history of the field as a series of five essentially consecutive eras: