since one engine cannot do a roll maneuver (although the later GEM 46 had thrust vectoring nozzle, only three were equipped with this feature and only ignited a brief moment during the ascent). The Space Shuttle had six vernier engines or thrusters in its "Vernier Reaction Control System" (VRCS). The VRCS could also deliver a gentle steady thrust. This was regularly used to boost the International Space Station while docked: for example during STS-130 commander George Zamka and pilot Terry Virts fired Endeavour's VRCS for a duration of 33 minutes to attain an orbit between . See also Space propulsion Cold gas thruster Vernier throttle References Spacecraft components Spacecraft attitude control