Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds

Ablative materials are required to protect a space vehicle from the extreme temperatures encountered during the most demanding (hyperbolic) atmospheric entry velocities, either for probes launched toward other celestial bodies, or coming back to Earth from deep space missions. To that effect, the resin-impregnated carbon ablator (RICA) is a high-temperature carbon/phenolic ablative thermal protection system (TPS) material designed to use modern and commercially viable components in its manufacture. Heritage carbon/phenolic ablators intended for this use rely on materials that are no longer in production (i.e., Galileo, Pioneer Venus); hence the development of alternatives such as RICA is necessary for future NASA planetary entry and Earth re-entry missions. RICA s capabilities were initially measured in air for Earth re-entry applications, where it was exposed to a heat flux of 14 MW/sq m for 22 seconds. Methane tests were also carried out for potential application in Saturn s moon Titan, with a nominal heat flux of 1.4 MW/sq m for up to 478 seconds. Three slightly different material formulations were manufactured and subsequently tested at the Plasma Wind Tunnel of the University of Stuttgart in Germany (PWK1) in the summer and fall of 2010. The TPS integrity was well preserved in most cases, and results show great promise

Independent Promotion of Young Talents in Satellite Development on the Full-Scale Satellite Mission SOURCE

The SOURCE mission is the first student satellite developed at the University of Stuttgart. This unique opportunity for undergraduate and graduate students is made possible by the cooperation between the Institute of Space Systems (IRS) and the Small Satellite Student Society (KSat e.V.

Update on DLR's OSIRIS program and first results of OSIRISv1 on Flying Laptop

Optical satellite links have gained increasing attention throughout the last years. Especially for the application of optical satellite downlinks. Within the OSIRIS program, DLR's Institute of Communications and Navigation develops optical terminals and systems which are optimized for small satellites. After the successful qualification and launch of two precursor terminals, DLR currently develops OSIRISv3, a 3rd generation OSIRIS terminal with up to 10 Gbps downlink rate, and OSIRIS4Cubesat, a miniaturized version optimized for Cubesat Applications. The University of Stuttgart's Institute of Space Systems develops small satellites, which are used to demonstrate novel technologies in the Space domain. Together, DLR and University of Stuttgart integrated the first OSIRIS generation onboard the Flying Laptop satellite, which was launched in July 2017 and has been successfully operated since. This paper will give an overview about DLR's OSIRIS program. Furthermore, it will show first results of OSIRISv1 on Flying Laptop. Therefore, the Flying Laptop satellite and OSIRISv1 will be explained. Preliminary results from the validation campaign, where optical downlinks have been demonstrated, will be given. © 2019 SPIE. Downloading of the abstract is permitted for personal use only

A small satellite with a dual-frequency heterodyne spectrometer for the detection of atomic oxygen in the atmosphere of Earth

A first step towards realization, a small satellite study for OSAS (Oxygen Spectrometer for Atmospheric Science) has been performed based on Concurrent Engineering methods

Entwicklung eines additiv gefertigten Schutzes gegen hochenergetische Strahlung für Satellitenelektroniken (Bachelorarbeit)

Das Deutsche Zentrum für Luft- und Raumfahrt e.V. (DLR) forscht im Rahmen des Projekts „Integrated Research Platform for Affordable Satellites“ (IRAS) an neuen Bauweisen und Prozessen zur Beschleunigung und Kostenminderung im Bereich des Satellitenbaus. Zwei ausschlaggebende Sektoren zur Kostenreduktion sind die Gewichtsreduktion und die Optimierung des Fertigungsablaufs. Unter dieser Zielsetzung wird in der vorliegenden Arbeit ein additiv gefertigter Strahlungsschutz gegen Weltraumstrahlung entwickelt. Der Strahlungsschutz ist als Teil einer Technologiedemonstration als Nutzlast bei einer LEO-Mission vorgesehen. Vor der Auslegung des Strahlungsschutzes wird dafür eine Literaturrecherche durchgeführt, um ein ideales Konzept zu entwickeln. Unter Berücksichtigung der Rahmenbedingungen von Trägersatellit und seitens des Projekts selbst, wird als erster Schritt der Auslegung die Strahlungsbelastung während der gesamten Missionsdauer auf den Strahlenschutz bestimmt. Nach der Bestimmung dieser Werte wird im Anschluss die benötigte Aluminiumdicke errechnet, die den kommerziellen Sensor im Technologiedemonstrator schützen soll. Es folgt eine Umrechnung der Aluminiumdicke in die Dicke für eine Schirmung aus den additiv fertigbaren Materialien. Nach der Bestimmung der endgültigen Schirmungsdicke folgt eine Geometrieauswahl. Durch dieses Vorgehen wird die benötigte Dicke auf die bestmögliche Geometrie angewendet. Da der Strahlungsschutz in den Wabenkern des Technologiedemonstrators integriert werden soll, werden im Anschluss kleinere Anpassungen an der Schirmungsgeometrie vorgenommen. Der finale Strahlungsschutz besteht aus drei Schichten. Zwei Low-Z-Schichten aus PEEK mit Kohlenstoffkurzfasern werden von einer High-Z-Schicht aus PEEK mit Wolframpartikeln getrennt. Der Strahlungsschutz ist aufgrund der Materialwahl und des identischen Fertigungsverfahrens in die Wabenkernfertigung integrierbar. Im Rahmen dieser Arbeit kann ist die Konzeptionierung und Auslegung des additiv gefertigten Strahlungsschutz ganzheitlich vollzogen werden. Die theoretische Umsetzung des Konzepts zeigt das Potential eines additiv gefertigten Strahlungsschutzes nicht nur in der Funktionsintegration, sondern auch beim konventionellen Satellitenbau auf

Untersuchung des Einflusses der Prozesstemperaturen beim 3D-Druck (FFF) auf die Materialeigenschaften von PEEK (Bachelorarbeit)

Mit dem Ziel eine Infrastruktur für Satellitenkonstellationen aufzubauen, werden im Projekt IRAS (Integrated Research Platform for Affordable Satellites) Entwicklungsmethoden für kostengünstige Satellitenstrukturen untersucht. Das DLR Institut für Bauweisen- und Strukturtechnologie in Stuttgart befasst sich dabei mit neuen Produktionstechnologien und insbesondere der additiven Fertigung. Diese Arbeit beschäftigt sich im Rahmen des Projekts IRAS mit der Untersuchung des Einflusses der Prozesstemperaturen beim 3D-Druck (Fused-Filament-Fabrication) von PEEK auf dessen Materialeigenschaften. PEEK ist ein Hochleistungsthermoplast mit sehr guten mechanischen Eigenschaften sowie chemischer Beständigkeit, der für Raumfahrtanwendungen geeignet ist. Mit unterschiedlichen Prozesstemperaturen (Düsen-, Bauraum- und Plattentemperatur) werden Proben gedruckt und diese auf ihre Materialeigenschaften untersucht. Die ausgewählten Düsentemperaturen liegen dabei im Bereich 426 °C - 450 °C und die Bauraum- und Plattentemperaturen im Bereich 150 °C - 260 °C und 160 °C - 270 °C. Besonders interessant sind die Auswirkungen auf Steifigkeit, Festigkeit, Kristallinität und Schichtverbund. Diese werden mithilfe von Zugversuch, thermischer Analyse und Lichtmikroskopie bestimmt. Zusätzlich gibt es Vorversuche, mit denen Druckertemperaturen und die Kennwerte des Filaments bestimmt werden. Die Auswertung führt zu unterschiedlichen Materialkennwerten (Steifigkeit und Festigkeit) abhängig von der Prozesstemperatur. Innerhalb des getesteten Temperaturbereichs steigen die Materialkennwerte bei Erhöhung der Prozesstemperaturen, sodass die höchsten Werte bei hohen Platten-, Bauraum- und Düsentemperaturen erzielt werden

MECHANICAL CHARACTERISATION OF IN-SITU BONDING BETWEEN PEEK FILAMENTS AND LAMINATES IN THE FFF PROCESS

Fused filament fabrication (FFF) of high-temperature, aerospace-grade thermoplastics like PEEK has made significant progress in recent years and has become an established process for 3D-printing of complex parts. However, possibilities of adding long or continuous fibres are still limited and the introduced thermal stresses limit the maximum part dimensions. To overcome these limitations, this work investigates the potential of bonding FFF printed parts in-situ onto continuous fibre reinforced laminates. This process allows the combination of the complexity of 3D-printing with large scale manufacturing processes for high-performance structures. The investigation is divided in two steps. Firstly, the effect of process temperatures on the inter-layer bonding of printed PEEK is investigated. On this basis, the optimal process parameters for the bonding of printed PEEK onto PEEK laminates are analysed. The results show a strong correlation between the process temperatures and the inter-layer bonding as well as the bonding between filament and laminates. The process influences shown form the basis for future hybrid component and process designs

Additive manufacturing of radiation shielding for small satellites

An increasing demand on reliability in the automotive industry, driven by the development of autonomous driving, has led to a high availability of inexpensive electronics with high potential for space applications. Several of these applications have already been proposed within the NewSpace trend. However, the high-radiation environment inherent to space operations lies outside the automotive hardware development scope and is therefore often the show-stopper for using such electronics for space applications. This work examines the possibility of designing and manufacturing weight- and cost-efficient radiation shielding using additive manufacturing. A printable shielding material, composed of tungsten powder embedded in the high-performance thermoplastic polyether-ether-ketone (PEEK), was developed and used to design a multi-material, multifunctional sandwich structure for local shielding of a representative automotive MEMS sensor. Radiation simulation was used to find the most efficient geometry and distribution of the shielding material. Additionally, the simulation has shown the required amount of shielding material to keep the total ionising dose below the previously tested limits of the sensor. The local shielding realised by additive manufacturing allows a minimal use of tungsten and thereby weight benefits compared to traditional shielding in aluminium boxes. The design will be demonstrated on the University of Stuttgart CubeSat mission, SOURCE, by comparing a shielded and unshielded area of the sandwich. The demonstrated shielding concept can easily be transferred to other hardware and missions and can thereby reduce both weight and cost of future spacecrafts

Topology Optimization of a Star Tracker Camera Bracket

Topology optimization is a powerful tool in lightweight design and has become increasingly popular with recent advances in additive manufacturing (AM). In the space industry, optimized and 3D-printed structures have the potential to meet the increasing demand for cost-efficient, flexible design and manufacturing strategies driven by large satellite constellations. In this paper a case study for re-designing a satellite structure is presented, identifying and exploring challenges and opportunities throughout the entire process chain. The reference part for this study is a star tracker camera bracket from the academic satellite Flying Laptop from the University of Stuttgart, currently operating in orbit. The original part was manufactured using standard machining processes and is used for functional as well as the cost reference of the AM optimization and manufacturing approach. The first step of the investigation is a characterization of AlSi10Mg manufactured by Laser Powder Bed Fusion (LPBF), focusing on the demands for topology optimization and associated cost-intensive post processing. Mechanical and metallographic properties for different sample geometries, orientations and heat treatments have been analyzed. This data provides the input for the material model in the optimization process as well as the optimization constraints. Following this step, the mesh-based optimization result is converted to a CAD geometry to assess manufacturability. For validation and cost assessment, the bracket is printed three times in one build-job using a Trumpf TruPrint 3000. Printed brackets are assessed for their natural frequency, the dominant design constraint, as well as the geometrical distortion and compared to the analysis results. Finally, design and manufacturing costs of the single part and of a small series of 99 parts is calculated to evaluate economic potential of the optimized and printed design. For the reference part presented in this study, the optimized design is 30 % lighter than the original and exhibits a 43 % higher first natural frequency. Additionally, a considerable scaling effect on the manufacturing costs is shown, keeping additive manufacturing competitive compared to small series machining production