Ion-thruster for Space Propulsion is Smallest ever space engine. Measuring only ten centimeters across and emitting a faint blue glow as it runs, the Field Emission Electric Propulsion (FEEP) engine produces an average thrust equivalent to the force of a single falling hair. But despite its low power, FEEP's thrust range and controllability are far superior to more forceful thrusters, holding the key to future success of an ambitious ESA science mission. "Most propulsion systems are employed to get a vehicle from A to B," explains Davide Nicolini of ESA's Scientific Projects Department, in charge of the FEEP project. "But with FEEP the aim is to maintain a spacecraft in a fixed position, compensating for even the tiniest forces perturbing it to an accuracy that no other engine design can match."
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