Zero-Gravity Graphene

By Siân Fogden

In a successful collaboration between the Graphene Flagship and the European Space Agency (ESA), experiments testing graphene for two different space-related applications have shown promising results. Based on these results, the Graphene Flagship is continuing to develop graphene devices for use in space.

Loop Heat Pipes

After initial experiments performed in zero-gravity conditions to investigate if graphene’s thermal properties could improve the performance of loop heat pipes, (the thermal managementsystems used in aerospace and satellite applications), research continues to move forward within the Graphene Flagship.

“Graphene has many opportunities for applications. One of them, recognised early on, is space technology. The Graphene Flagship, with the leading contribution of aerospace industry partner Leonardo, has demonstrated the viability of graphene for thermal management in space. The plan during Core 2 is to progress it further for tests to be then conducted on a space­craft,” said Andrea Ferrari, science and technology officer of the Graphene Flagship and chair of its Management Panel.

The researchers are now moving from proof of concept to a true to scale working device using the graphene coated wick. The wick is the main element in the loop heat pipes where heat is transferred from a hot object into a fluid, which cools the system.

“We were very pleased to find that the measurements we took during the parabolic flight campaigns demonstrated that graphene has a positive effect on the evaporation rate through the wicks. Since then we have been performing further experi­ments to understand the reasons for this improvement whilst also working on scaling up the graphene coatings to industrial-­wicks, like the ones on satellites and spacecraft,” said
Meganne Christian, a researcher at the National Research Council of Italy (CNR) and part of the loop heat pipe team.

“This is a great example of how the Flagship is working: bringing together three academic partners and one big industrial partner with a clearly defined goal for an application,” said Vincenzo Palermo, vice-director of the Graphene Flagship.

“For a company like Leonardo, innovation is vital: we put great expectations in the industrialisation of graphene-based products. Thanks to the Flagship the introduction into market can be significantly accelerated, as for the loop heat pipe,” says Marco Molina, chief technical officer of space activities at Leonardo.

The graphene wicks were tested in a collaboration between the Microgravity Research Centre, Université libre de Bruxelles, Belgium; the Cambridge Graphene Centre, University of Cambridge, UK; the Institute for Organic Synthesis and Photoreactivity and the Institute for Microelectronics and Micro­systems, both at the National Research Council of Italy (CNR) and industry partner Leonardo Spa, Italy, a global leader in aerospace, operating in space systems and high-tech instrument manufacturing and in the management of launch and in-orbit services and satellite services. To test the graphene-­coated wicks in microgravity conditions, the researchers took part in 6 parabolic flights in November and December 2017 which were operated by ESA in partnership with Novespace.

Solar Sails

Testing graphene space-propulsion potential, a team of PhD students from Delft Technical University (TU Delft), The Netherlands participated in ESA’s Drop Your Thesis! campaign, which offers students the chance to perform an experiment in microgravity at the ZARM Drop Tower in Bremen, Germany. To create microgravity conditions, down to one millionth of the Earth’s gravitational force, a capsule containing the experiment is catapulted up and down the 146 metre tower, leading to 9.3 seconds of weightlessness. The TU Delft Space Institute, The Netherlands, also provided support to the GrapheneX project.

The team—named GrapheneX—designed and built an experi­ment to test graphene for use in solar sails, usinggraphene mem­branes provided by Graphene Flagship partner Graphenea. The idea was to test how these would behave under radiation pressure from lasers. In total, the experiment ran five times over 13-17 November 2017.

“Our experiment is like a complex ‘clockwork’ where every component has to go off seamlessly at the right time,” said Rocco Gaudenzi, a member of the GrapheneX team, “it does not often happen that you have to build up such a clockwork from scratch, and you can only test it during the launch itself.”

The team worked hard to make the experiment successful. “Despite the initial technical difficulties, we managed to quickly figure out what was going on, fix the issues and get back on track. We are very happy with the results. We observed laser-­induced motion of a graphene light sail, and most importantly we had a great experience!” said Davide Stefani, GrapheneX team member.

Santiago J. Cartamil-Bueno, GrapheneX team leader, indicated that both the experience and the results were valuable to the team. “The most important lesson is that something will always happen, and you need to be ready to adapt or to change,” he said. “I think at the end of the day, it is about the experience; you just need to create new challenges and learn from them, and be ready to grab more experience and go to the next level.”

Though the GrapheneX experiment is now finished, the team is planning further tests as part of a new and ambitious research project, to continue exploring the influence of radiation pressure on graphene light sails.