12-03, 10:40–11:00 (Europe/Luxembourg), Banquet Room
In order to send solar sails beyond the outer solar system, significant improvements regarding the sail velocity must be achieved. To improve the velocity, the total spacecraft mass needs to be reduced. A first step is to implement aerographite (density of 0.18 kg m^-3), a new type of sail material, proposed by Heller in 2020. The next step would be to improve the deployment system. Until now, conventional motor driven metal booms unfold the sails. By removing the booms and motors, the velocity improves. Without the stabilizing booms the sail collapses under the photon pressure in the close vicinity of the sun (preceding simulations). Yet, a low solar orbit is necessary for maximum sail performance. Therefore, an alternative stabilizing strategy is required. First, the sail will not have a conventional two-dimensional shape, but rather a three-dimensional rotational body shape. This gives the sail a self-stabilizing geometry under the influence of solar radiation and wind. The shapes can be e.g. semi-spheres, cone-like, funnel- or horn-like. These shapes are to be tested initially in a smaller scale in a vacuum, whilst being irradiated by a solar simulator and being exposed to a neutral plasma stream to simulate the solar wind. Secondly, alternative deployment mechanisms are required to unfold the sail and stabilize it. So far, we investigate the use of shape memory alloys (SMA), embedded in the sail material, as well as the integration of unipolar electrets to use the Coulomb forces between them for unfolding. The SMA can be activated either passively by solar radiation or actively by Joule-heating. We test multiple methods to embed the SMA, e.g. weaving the SMA into the material. Furthermore, by using infrared radiation heating under vacuum conditions, the passive deployment can be tested. The active deployment can be tested by applying a voltage to the SMA. The electrets are produced by shielding free charges on a metal core with a dielectric sheath against the environment. This process is validated by measuring the surface potential of the electret. Future strategies will include the investigation of the interaction between the aerographite and the space environment.
Julius Karlapp studied mechanical and aerospace engineering at the Dresden University of Technology (TUD) in Germany, graduating in 2023. As research associate, he currently pursues his doctoral degree at the chair of space systems at TUD. His research focuses on solar sail propulsion.
Prof. Dr. Martin Tajmar studied physics, space studies as well as electrical engineering and graduated with a PhD in 1999 from the Vienna University of Technology in Austria. After research stays at NASA JPL and ESA-ESTEC, he joined the Austrian Institute of Technology from 2000-2010 where he was head of the business unit space propulsion & advanced concepts. After being appointed as associate professor at KAIST, he moved to TU Dresden in Germany as full professor and head of the chair of space systems in 2012, where he was later appointed as the director of the institute of aerospace engineering. Besides the developments of his group, which includes small satellites and activities on liquid-fueled rocket engines using aerospike nozzles, his main research focus is on the development of novel electric propulsion systems and really advanced concepts for future space flight.