The thruster for the Sert-II test consisted of two electron bombardment engines using mercury propellant. The thruster anode diameter was 15 cm, and a hollow cathode neutralizer was used. Beam power supply voltage was 3000 V, and the power per thruster was 0.85 kW, producing 28 mN thrust at a specific impulse of 4200 seconds. About 15 kg of propellant was carried. The longest ground test prior to launch was 6742 hours, and in space one engine operated for 2011 hours until a grid short occurred. The second operated for 3781 hours before the neutralizer tank was depleted.