DropCoal

To examine different needle geometries and outer coatings related to the formation of the most stable drops, a microgravity experiment was conducted during the DropCoal project by the Science Team. This series of exciting experiments took place during the 79th ESA Parabolic Flight Campaign (PFC) in October 2022 at Novespace, a subsidiary of the French Space Agency (CNES, Centre National d’Études Spatiales) in Bordeaux-Mérignac, France. The campaign was funded by the European Space Agency (ESA) and the German Aerospace Center (DLR), with experiments carried out onboard the Airbus A310 ZERO-G aircraft.

Experiment Overview

The experimental campaign aimed to test components and setups for two related microgravity research projects, ESA DropCoal and DLR interDropCoal, which study the coalescence and mixing of binary droplets in microgravity. Both projects focus on understanding the approach and the contact between two droplets with high precision regarding both time and spatial resolution. While complementary, they differ in their experimental environments and specific objectives.

DLR interDropCoal is designed for parabolic flight testing to investigate the initial moments of droplet coalescence. The project focuses on short-term microgravity and aims to validate the primary components and procedures of the experimental setup needed for the next phase, which includes a second parabolic flight campaign.

The ESA DropCoal experiment is designed to study droplet coalescence in a controlled environment on the International Space Station (ISS). The microgravity conditions aboard the ISS allow for extended observation of droplet mixing after coalescence, providing unique insights unattainable on Earth. As part of the current campaign, researchers are testing various needle designs to optimize the creation, stabilization, and removal of droplets during the experiment, ensuring the setup's reliability and effectiveness.

The goal of this parabolic flight campaign is to test and validate the experimental designs, needle prototypes, and functionality of all major components in microgravity conditions. This will support the readiness of both projects for their next phases: another parabolic flight for DLR's interDropCoal project and an ISS mission for ESA's DropCoal project.

The ESA Parabolic Flight Campaign provided several advantages, including the ability to conduct multiple microgravity phases on each flight day, with several flights throughout the two-week duration. Researchers were directly involved in their experiments during breaks between the parabolic flights.

In the first week, we mounted, adjusted, and tested the experimental setup in the Novespace warehouse and on board the airplane. During the second week, we had three days of flights, with each day featuring 31 parabolas. Each parabola included two hypergravity phases lasting about 20 seconds each, reaching 1.8 g, followed by a microgravity phase of approximately 22 seconds.

Meet the DROPCOAL 79th ESA Parabolic Flight Campaign Team

• INFLPR - Laser Department - Laser Spectroscopy and Optics Group (SOL):
  • Prof. Mihail Lucian Pascu
  • Dr. Mihai Boni
  • Dr. Ionut-Relu Andrei
  • Marian Cojocaru
• TUD - Institute for Fluid Mechanics and Aerodynamics:
  • Prof. Dr.-Ing. Jeanette Hussong
  • Apl. Prof. Ilia Roisman
  • M.Sc. Benedikt Schmidt
  • M.Sc. Simon Burgis
  • M.Sc. Kilian Köbschall
  • Timm Geelhaar

We acknowledge the invaluable contributions of Assoc. Prof. Dr. Ing. Dumitru Cristian Tranca, from the Politehnica University of Bucharest, Faculty of Automatic Control and Computer Science in the automation of the system used in the ESA Dropcoal experiments made in this parabolic flight campaign.