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A Critical History of Electric Propulsion Part II: 1957-1979

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Abstract

The launch of Sputnik in 1957 catalyzed a decisive shift in electric propulsion (EP) from a largely theoretical pursuit to an engineering discipline with flight demonstrations and the beginnings of routine application. Between 1957 and 1979—what we term the Era of Diversification and Development—Western programs (here considered globally but exclud- ing the Soviet Union) broadened the portfolio of EP concepts, advanced the engineering of gridded ion engines, matured electrothermal devices (resistojets, arcjets), and flew the first electromagnetic pulsed plasma thrusters (PPTs). Landmark demonstrations such as SERT I (1964) and SERT II (1970) established space operation and long-duration feasibil- ity of ion propulsion, while early satellite uses of PPTs (LES–6, 1968) and resistojets (Vela, 1965) proved EP’s utility for attitude control and stationkeeping. In the 1970s, targeted in-orbit experiments (e.g., ATS–6) and environmental control tests (SCATHA/SPIBS) re- solved key integration issues (neutralization, charging, contamination), and Solar Electric Propulsion (SEP/SEPS) studies matured multi-kilowatt stages even as budget realities de- ferred flight. In parallel, UK (T-line culminating in T5) and German (RIT-10) programs produced flight-like ion engines, giving Europe complementary capabilities. Synthesizing these threads, we argue that a portfolio of technologies coevolved as mission pull favored “sedentary” roles first, power availability bounded ambition, and incremental engineering solutions made EP behave like a reliable spacecraft subsystem.