Design and Test of a Student Hybrid Rocket Engine with an External Carbon Fiber Composite Structure

The development of hybrid rockets offers excellent opportunities for the practical education of students at universities due to the high safety and relatively low complexity of the rocket propulsion system. During the German educational program Studentische Experimental-Raketen (STERN), students of the Technische Universität Braunschweig obtain the possibility to design and launch a sounding rocket with a hybrid engine. The design of the engine HYDRA 4X (HYbridDemonstrations-RaketenAntrieb) is presented, and the results of the first engine tests are discussed. The results for measured regression rates are compared to the results from the literature. Furthermore, the impact of the lightweight casing material carbon fiber-reinforced plastic (CFRP) on the hybrid engine mass and flight apogee altitude is examined for rockets with different total impulse classes (10 to 50 kNs). It is shown that the benefit of a lightweight casing material on engine mass decreases with an increasing total impulse. However, a higher gain on apogee altitude, especially for bigger rockets with a comparable high total impulse, is shown

Addressing the effects of background plasma and wake formation on nanosatellites with electric propulsion using a 3D Particle In Cell code

3D-PIC (Particle In Cell) simulations were performed to emulate the dynamics and collection of plasma particles onto the surface of the UWE-IV, a satellite of miniaturized dimensions (CubeSat) launched in 2018. We review the electrostatic potential, currents collected and plasma disturbances of the CubeSat and characterize them by numerical simulation over Low Earth Orbits (LEO), in two general cases: as a passive satellite and with active thrusters without regard of neutralization units. During one orbital period the passive CubeSat drives an isotropic impingement of plasma electrons, that (because their higher mobility regarding ions) govern a negative surface potential. However, by the time-evolution of the charge sheath, we relate that potential barriers may be forming around the satellite that can reduce the collection of electrons over spacecraft surfaces. When thrusters are fired, spacecraft becomes more negatively charged than for a passive satellite, and their potential energy Esc is about hundreds of times larger than the ambient ion flowing energies, Ei. In this case, ion density maps of ambient oxygen (O+), show particles fill in the ion void (wake) zone due to bare electrostatic attraction by a (growing) negative satellite potential. The experiment was repeated in different orbit altitudes with varying plasma densities, showing that in space zones with greater concentration of plasma ions, the satellite potential is less negative, ultimately linked to this near-wake ion-focusing collection. Thus, we conclude that if thrusters operate in LEO altitudes, where the relatively higher plasma concentrations are (equatorial orbits of 300–500 km), large negative potentials can be avoided due to the natural rule of ambient ion dynamics. This study can be important for operations of future miniaturized satellites using this type of thruster technologie

Ground verification of the feasibility of telepresent on-orbit servicing

In an ideal case telepresence achieves a state in which a human operator can no longer differentiate between an interaction with a real environment and a technical mediated one. This state is called transparent telepresence. The applicability of telepresence to on-orbit servicing (OOS), i.e., an unmanned servicing operation in space, teleoperated from ground in real time, is verified in this paper. For this purpose, a communication test environment was set up on the ground, which involved the Institute of Astronautics (LRT) ground station in Garching, Germany, and the European Space Agency (ESA) ground station in Redu, Belgium. Both were connected via the geostationary ESA data relay satellite ARTEMIS. Utilizing the data relay satellite, a teleoperation was accomplished in which the human operator as well as the (space) teleoperator was located on the ground. The feasibility of telepresent OOS was evaluated, using an OOS test bed at the Institute of Mechatronics and Robotics at the German Aerospace Center (DLR). The manipulation task was representative for OOS and supported real-time feedback from the haptic-visual workspace. The tests showed that complex manipulation tasks can be fulfilled by utilizing geostationary data relay satellites. For verifying the feasibility of telepresent OOS, different evaluation methods were used. The properties of the space link were measured and related to subjective perceptions of participants, who had to fulfill manipulation tasks. An evaluation of the transparency of the system, including the data relay satellite, was accomplished as well

Determining the influence on orbit prediction based on uncertainties in atmospheric models

Orbit prediction and knowing its uncertainties is a key part in planning collision avoidance maneuvers or conducting re-entry estimations. For high accuracy forecasts numerical propagators are used. These propagators use force models to estimate the perturbing elements that affect a satellite's orbit. Especially on low Earth orbits (LEO) with decreasing perigee altitude the atmosphere becomes the dominating perturbing force. The available atmospheric models are complex in nature and react very sensitive to their input data. As with any model the atmospheric models also feature uncertainties. Because they heavily depend on the solar and geomagnetic activity, further uncertainty is introduced due to insufficient forecast capabilities of the solar and geomagnetic activity. The uncertainties introduced to the orbit prediction due to the atmospheric model's input parameters are investigated. The approach is to analyze the trajectory of different satellites, which are on different altitudes and inclinations. Using a numerical propagator a baseline is established applying observed solar and geomagnetic activity data of the past and estimate the satellites' orbit. Different types of solar and geomagnetic activity forecasts are used as implemented in the Orbital Spacecraft Active Removal (OSCAR) software, a tool of ESA's Debris Risk Assessment and Mitigation Analysis (DRAMA) software suite. The orbit prediction is repeated with the different solar and geomagnetic forecasts. The uncertainties of the orbit prediction as a result of the comparison to the baseline are shown

Concept and Feasibility Evaluation of Distributed Sensor-Based Measurement Systems Using Formation Flying Multicopters

Unmanned aerial vehicles (UAVs) have been used for increasing research applications in atmospheric measurements. However, most current solutions for these applications are based on a single UAV with limited payload capacity. In order to address the limitations of the single UAV-based approach, this paper proposes a new concept of measurements using tandem flying multicopters as a distributed sensor platform. Key challenges of the proposed concept are identified including the relative position estimation and control in wind-perturbed outdoor environment and the precise alignment of payloads. In the proposed concept, sliding mode control is chosen as the relative position controller and a gimbal stabilization system is introduced to achieve fine payload alignment. The characterization of the position estimation sensors (including global navigation satellite system and real-time kinematics) and flight controller is carried out using different UAVs (a DJI Matrice M600 Pro Hexacopter and Tarot X4 frame based Quadcopter) under different wind levels. Based on the experimental data, the performance of the sliding mode controller and the performance of the gimbal stabilization system are evaluated in a hardware-in-the-loop simulation environment (called ELISSA). Preliminary achievable control accuracies of the relative position and attitude of subsystems in the proposed concept are estimated based on experimental result

Modeling degraded performance metrics of optical amplifiers under radiation

Gain, noise figure (NF), and output power are considered the common performance metrics of an optical fiber amplifier. With an increasing interest of space industry in developing technologies for satellite-ground and intersatellite communication in the optical band, the EDFA (erbium doped fiber amplifier) is needed as power amplifier in space to compensate attenuation and insertion losses between the building blocks of the architecture. There is very little research on modeling the degradation mechanisms of typical commercial fibers, specifically on the NF and output power metrics, that requires knownledge of the insertion losses at the entrance of the fiber for both the pump and the signal wavelengths λp and λs. In this brief report we propose that the noise figure and output power trends can be extrapolated from a semi-empirical model for the insertion losses proved at high and low dose rates at two different temperatures. The results show reasonable trends that a common offthe shelf EDFA can present in co-propagating configuration on the NF and output power under several doses at low and high rates. The radiation losses using non-hardened fiber show sustainable attenuation levels in dB that can possibly allow employing this off-the shelf fibers in CubeSats or small satellites without the need of special radiation insulation. It is further supported with theoretical data that the temperature factor can affect more the EDFA degradation in space than the radiation itself, imposing limits on the temperature control of commercial satellites using this photonics

Fully Modular Robotic Arm Architecture Utilizing Novel Multifunctional Space Interface

The current paradigm in space robotics is the design of specialized robotic manipulators to meet the requirements for a specific mission profile. This research aims to develop a novel concept of a modular robotic arm for multi-purpose and multi-mission use. The overall approach is based on a manipulator formed by serial connection of identical modules. Each module contains one rotational joint. The joints, rotation axis is tilted under an angle of 45° to the normal axis, which requires less stowage space compared to a traditional joint configuration. A manipulator can be reconfigured in orbit by adding or removing modules and end effectors, therefore modifying the degrees of freedom (DoF) as well as the workspace. Redundancies are introduced, since defect modules may be removed or replaced. This paper outlines the overall concept of modularization of a robotic arm. The development and mechanical design of a terrestrial demonstrator based on the multifunctional interface iSSI (intelligent Space System Interface) is presented, which is intended for OOS and OOA activities. Furthermore, a variant of the modular robotic system with 24 DoF is presented, which can be stowed in a Cubesat-sized environment. It can operate in spaces with limited accessibility and is dedicated for tasks like inspection and delicate repairs. Finally, an outlook to further research potential and future use cases for the modular robotic system is given.BMWi, 50RP1960A, Verbundvorhaben HOMER: Hoch-redundante modulare Robotersysteme zum flexiblen Einsatz in der Raumfahrt und der Automotive-Serienfertigung; Teilvorhaben Kinematik und RedundanzBMWi, 50RP1960B, Verbundvorhaben: HOMER - Hoch-redundante modulare Robotersysteme zum flexiblen Einsatz in der Raumfahrt und der Automotive-Serienfertigung; Teilvorhaben: modulare Robotikstrukture

Small-volume potentiometric titrations: EPR investigations of Fe-S cluster N2 in mitochondrial complex

EPR-based potentiometric titrations are a well-established method for determining the reduction potentials of cofactors in large and complex proteins with at least one EPR-active state. However, such titrations require large amounts of protein. Here, we report a new method that requires an order of magnitude less protein than previously described methods, and that provides EPR samples suitable for measurements at both X- and Q-band microwave frequencies. We demonstrate our method by determining the reduction potential of the terminal [4Fe-4S] cluster (N2) in the intramolecular electron-transfer relay in mammalian respiratory complex I. The value determined by our method, Em7 = − 158 mV, is precise, reproducible, and consistent with previously reported values. Our small-volume potentiometric titration method will facilitate detailed investigations of EPR-active centres in non-abundant and refractory proteins that can only be prepared in small quantities

Survey of the Current Activities in the Field of Modeling the Space Debris Environment at TU Braunschweig

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model MASTER. In addition to updating the historical population, the future evolution of the space debris environment is also being investigated. The competencies developed within these activities are used to address current problems with regard to the possibility of an increasing number of catastrophic collisions. Related research areas include, for example, research in the field of orbit determination and the simulation of sensor systems for the acquisition and cataloging of orbital objects. In particular, the ability to provide simulated measurement data for object populations in almost all size ranges is an important prerequisite for these investigations. Some selected results on the distribution of space debris on Earth orbit are presented in terms of spatial density. Furthermore, specific fragmentation events will be discussed

THE H2020 PROJECT REDSHIFT: OVERVIEW, FIRST RESULTS AND PERSPECTIVES

The ReDSHIFT (Revolutionary Design of Spacecraft through Holistic Integration of Future Technologies) project has been approved by the European Community in the framework of the H2020 Protec 2015 call, focused on passive means to reduce the impact of Space Debris by prevention, mitigation and protection. In ReDSHIFT these goals will be achieved through a holistic approach that considers, from the outset, opposing and challenging constraints for the space environment preservation, the spacecraft survivability in the harsh space environment and the safety of humans on ground. The main innovative aspects of the project concern a synergy between theoretical and experimental aspects, such as: long term simulations, astrodynamics, passive de-orbiting devices, 3D printing, design for demise, hypervelocity impact testing, legal and normative issues. The paper presents a quick overview of the first ReDSHIFT results in an effort to highlight the holistic approach of the project covering different aspects of the space debris mitigation field. De- tailed reports on the results of the single Work Packages can be found in other papers in this same volume