![](\"http:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2018\/08\/water_hammer_test_bench\/17663210-1-eng-GB\/Water_Hammer_Test_Bench_small.jpg\")
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\nPart of ESA\u2019s Propulsion Laboratory, this Water Hammer Test Bench simulates the vital moment early in a satellite\u2019s life when propellant is first pumped through its propulsion system.\n<\/p>\n
\n\u201cPropulsion is a core subsystem, essential to the operation of the spacecraft,\u201d explains ESA propulsion engineer Andreas Gernoth. \u201cIf other systems fail, impacting the spacecraft control \u2013 from solar array deployment to the reaction wheels that adjust satellite attitude \u2013 then the propulsion system has to go on working.\n<\/p>\n
\n\u201cSo it is essential that the propulsion system comes on line as soon as possible after launch, sometimes even before a data link is established. The resulting \u2018priming\u2019 action is what we reproduce here.\u201d\n<\/p>\n
\nTo help minimise the risk of leakage, propellant stays stored within a satellite\u2019s propellant tank while on the ground. It is only released into the propellant lines once the satellite reaches space. But this abrupt surge of propellant can cause high pressure peaks, similar to the terrestrial \u2018water hammer\u2019 that can cause knocking in water pipes as taps are turned on or off.\n<\/p>\n
\nIn space, these peaks have the potential to damage thruster valves at the end of the lines, leading to propellant leaks. In the case of highly reactive hydrazine propellant, too high a pressure peak could even trigger an explosion.\n<\/p>\n
\nAndreas adds: \u201cThese priming and water hammer peaks needs to be characterised precisely: the pressure sensors used within the Test Bench need to operate on a timescale of milliseconds, thousandths of a second. \n<\/p>\n
\n\u201cThe propulsion systems for all space missions go through this kind of validation, with most of the work done using software-based numerical simulation \u2013 through a program called EcosimPro. This facility is used to validate the results, using water rather than actual propellants for safety purposes.\u201d\n<\/p>\n
\nESA\u2019s Propulsion Lab<\/a> is based at its ESTEC technical centre in Noordwijk, the Netherlands, testing methods of controlling the motion of satellites in space, with a particular focus on electric propulsion.\n<\/p>\n \nCome visit ESTEC on Sunday 7 October; register to join our annual ESA Open Day<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" \nPart of ESA’s Propulsion Laboratory, this Water Hammer Test Bench simulates the vital moment early in a satellite’s life when propellant is first pumped through its propulsion system.\n<\/p>\n \n“Propulsion is a core subsystem, essential to the operation of the spacecraft,” explains ESA propulsion engineer Andreas Gernoth. “If other systems fail, impacting the spacecraft control – from solar array deployment to the reaction wheels that adjust satellite attitude – then the propulsion system has to go on working.\n<\/p>\n \n“So it is essential that the propulsion system comes on line as soon as possible after launch, sometimes even before a data link is established. The resulting ‘priming’ action is what we reproduce here.”\n<\/p>\n \nTo help minimise the risk of leakage, propellant stays stored within a satellite’s propellant tank while on the ground. It is only released into the propellant lines once the satellite reaches space. But this abrupt surge of propellant can cause high pressure peaks, similar to the terrestrial ‘water hammer’ that can cause knocking in water pipes as taps are turned on or off.\n<\/p>\n \nIn space, these peaks have the potential to damage thruster valves at the end of the lines, leading to propellant leaks. In the case of highly reactive hydrazine propellant, too high a pressure peak could even trigger an explosion.\n<\/p>\n \nAndreas adds: “These priming and water hammer peaks needs to be characterised precisely: the pressure sensors used within the Test Bench need to operate on a timescale of milliseconds, thousandths of a second. \n<\/p>\n \n“The propulsion systems for all space missions go through this kind of validation, with most of the work done using software-based numerical simulation – through a program called EcosimPro. This facility is used to validate the results, using water rather than actual propellants for safety purposes.”\n<\/p>\n<\/p>\n