DropCoal is an ESA-funded project whose prime contractor is RISE, which is in charge of manufacturing the hardware device, capable of performing coalescence experiments in microgravity. The experiments will be hosted in the Columbus module of the International Space Station by integrating the device into the ICE Cubes facility. DropCoal will therefore be the Experiment Cube #17 on board the station, helping an international science team to better understand key aspects of fluid dynamics and to push further the technologies in this field.

2 water droplets in direct contact
Coalescence of 2 water droplets

The DropCoal hardware is a compact novel design, based on results of previous experimental trials performed by the Science Team in the lab and as part of drop tower runs. 

Purpose of the experiment

  • Understanding the collisions of drops (for modelling fuel combustion, icing phenomena on flight systems etc.);
  • Determine the dynamics and mixing during the droplet coalescence process;
  • Characterization of the coalescence and mixing phenomenon of two different liquid drops under microgravity conditions;
  • Observing the deformation of the surfaces, caused by the dynamics of the gas or vapour flow in the gap.

The Experiment Cube contains a mechanism made up of several interconnected and automated subsystems, capable of performing coalescence experiments with drops of different liquids. Depending on the information that scientists request, a command is sent from the ground station to the Cube through the ICF interface so the scientists can perform different types of experiments, being allowed to modify the size of the drops, the speed of coalescence and the types of liquid with which the experiment is done.

The device is designed to meet a stringent set of requirements imposed both by ESA and ICF and by NASA, considering that the payload will end up operating on board the ISS. The safety and product assurance aspects are important in the framework of system engineering that takes place during the project, considering that the experiment requires to be handled by astronauts for its integration within the interface provided by the ICE Cubes facility.