re drag free satellites in article raee b s access digex net prb access digex com pat writes in article apr kelvin jpl nasa gov baalke kelvin jpl nasa gov ron baalke writes in answer to a question from hawking chahine described a proposed drag free satellite but confirmed that at this point it s only a concept so what s a drag free satellite coated with wd triad the first drag free satellite was designed and built by the johns hopkins applied physics laboratory and launched sept the satellite was in three sections separated by two booms the central section housed the discos disturbance compensation system which consisted of a proof mass of special non magnetic alloy housed within a spherical cavity the proof mass flew a true gravitational orbit free from drag and radiation pressure teflon microthrusters kept the body of the satellite centered around the proof mass thereby flying the entire satellite drag free triad was one of the apl designed navy navigation satellites the nd generation operational navigation satellites flying today nova use a single axis version of discos triad was also the sixth apl satellite to be powered by an rtg apl flew the first nuclear power supply in space in further info on triad discos etc can be found in spacecraft design innovations in the apl space department johns hopkins apl technical digest vol no eric hoffman
