LRO Propulsion System Testing

Abstract

The Lunar Reconnaissance Orbiter (LRO) is a robotic exploration observatory launched on June 18, 2009. The LRO spacecraft contains a monopropellant propulsion system with twelve thrusters, two propellant tanks, a composite overwrapped pressurant tank, and fluid control hardware to regulate the propellant supply to the thrusters. This paper provides a detailed discussion of the testing process that verified the functionality of the system. Sections in this paper walk through the various component tests performed at the propulsion system level, including pressure transducer calibration, valve leakage tests, pressure regulator performance tests, and thruster gas flow impedance tests. Test descriptions provide test rationale, method and equipment, and approximate duration. This paper also includes descriptions of special propulsion tests, including heater verification testing, propulsion module vibration testing, and propulsion testing performed during the observatory-level thermal vacuum testing. This paper concludes with an explanation of the major lessons learned during functional testing, including intricacies associated with a system that includes diaphragm tanks and pressure regulator testing difficulties associated with a large downstream volume. NomenclatureACS = attitude control system AN = Army-Navy Ar = argon ATK = Alliant Techsystems COPV = composite overwrapped pressure vessel EMI = electromagnetic interference FP = flow panel GHe = gaseous helium GN2 = gaseous nitrogen GSE = ground support equipment GSFC = Goddard Space Flight Center K = thousand LRO = Lunar Reconnaissance Orbiter MEOP = maximum expected operating pressure NASA = National Aeronautics and Space Administration NSI = NASA standard initiator PGSE = pressure ground support equipment psi = pounds per square inch (gauge) RV = relief valve S/C = spacecraft SCCH = standard cubic centimeters per hour SCCS = standard cubic centimeters per second 2 Flight Component Designators AT = attitude control system thruster GFDP = gas fill and drain valve -pyrovalve GFDR = gas fill and drain valve -regulator GFDT = gas fill and drain valve -tank HGF = high-pressure gas filter HLF = hydrazine low-pressure filter -top tank HPD = high-pressure transducer HPLV = high-pressure latch valve HPR = high-pressure regulator LBLF = hydrazine low-pressure filter -bottom tank LFDB = liquid fill and drain valve -bottom tank LFDT = liquid fill and drain valve -top tank LPD = low-pressure transducer MLV = manifold latch valve NT = insertion thruster PV = pyrovalve TLV = tank latch valve