Experiment Results and post-flight Analysis of the ISS Student Experiment PAPELL

Kurzfassung

Pump Application using Pulsed Electromagnets for Liquid reLocation (PAPELL) was a fast-paced student experiment conducted on the International Space Station (ISS). The 1.5 U flight hardware was integrated internally in an experiment rack of the educational company DreamUp and was executed for over 60 days in total during a half-year stay on the ISS. A multidisciplinary team of more than 30 students of the University of Stuttgart has developed PAPELL within less than a year to flight readiness status. The students have organised themselves within the Small Satellite Student Society of the University of Stuttgart (KSat e.V.) and were supported by the Institute of Space Systems. The technology demonstration experiment aimed to show that a mechanic-free actuation method can be proven by utilising a magnetisable liquid, a ferrofluid, and localised magnetic fields. Such a mechanic-free device is likely to be highly reliable and to have long lifetime. The absence of mechanical moving parts corresponds to minimal wear and tear and generation of vibrations. Lessened qualification requirements reduce development time and overall costs. The PAPELL experiment demonstrated successfully that ferrofluid manipulation by the utilisation of localised magnetic fields generated by electromagnets is possible in a repeatable and reliable way in the microgravity environment of the ISS. The functions of a digital microfluidic circuit, i.e. droplet generation, movement, splitting and merging have been shown during the operation phase. These results allow for a wide variety of application developments based on different transportation modes observed when operating PAPELL. The experiment has been equipped with a sensor suite to ascertain the secondary effects of the experiment. The produced data shows promising results, as disadvantageous effects are minimal. Further, it can be determined that ferrofluid actuation in microgravity requires less power compared to Earth-based tests, while viscosity, surface tension and magnetic field shape effects become significant. Sensor data and analysis of ferrofluid dynamic influenced by magnetic fields in a micro-gravity environment and corresponding behaviour in a ground test environment yields critical information for modelling the corresponding physics and informing future designs. As PAPELL was returned to Earth after mission conclusion, subsequent hardware analysis is conducted for in-depth assessment and respective reproduction experiments are planned.