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This paper analyses the synergy between two innovative technologies: green propellants and electric pump feeding, for a 500 N engine thrust range. The novel approach is then compared to the legacy configuration, i.e., an MMH/NTO pressure fed system. First, a discussion of the benefits and challenges of the different technologies is presented. Subsequently, the proposed configuration relying on green propellants and e-pumps is investigated. After selecting hydrogen peroxide as the baseline oxidiser, a comparative analysis of different fuel candidates is conducted, leading to the selection of propane as fuel. Furthermore, the second part of the paper weights the novel configuration against the standard one and confronts their propulsive performance and mass budget. Results show that the implementation of electric pump feeding can leverage the performance of the selected green propellant outpacing the conventional solution.

Here, we present a novel torsion balance with a torsional spring that can reach a resolution in the nano-Newton range while allowing for a total experimental weight of 2 kg. The balance uses an off-the-shelf electromagnetic actuator, which was calibrated. The oscillation of the balance is damped using an adaptable eddy-current brake to fine-tune the damping factor. Experiments and electronics are controlled and powered through four coaxial liquid contacts. The balance is shown to be highly linear between 0.01 and 300 μN. After an automated post-processing, the noise of a measurement was 1.0 nN, and an applied force of 10 nN had a calculated error of 11.9%.

Trapping ions, such as deuterium and tritium, inside a potential well to generate neutrons is a well-established technology through electric and magnetic fields via the inertial electrostatic confinement fusion (IECF) and the tokamak, respectively. In the IECF, the straightforward configuration is a concentric cathode connected to a negative bias, surrounded by a grounded anode that serves as a vacuum vessel. Theoretically, neutrons are generated inside the vessel through fusion between ions that are accelerated by applying several tens kV voltage and tens mA current. Many parameters affect the plasma conditions and fusion in the system, hence the neutron production rate (NPR). This study investigates the cathode transparency and the number of apertures effect on NPR. For this end, eleven cathodes were fabricated from stainless steel in three different groups with different transparency and number of apertures. NPRs were investigated as a function of the cathode transparency and number of apertures at low power operating mode ∼1 kW. Experimental results revealed that higher NPR was produced from lower grid transparency and vice versa; this behavior was explained through beam–surface fusion with grid surface. In addition, a higher NPR was generated from the grid with many apertures; this was attributed to the effect of the deuterium ionization improvement by the number of ionizing electrons through the grid channels.

Additive Manufacturing (AM) processes offer geometrical freedom to design complex shaped parts that cannot be manufactured with conventional processes. This leads to new applications including aerospace propulsion systems where the Ni-superalloy based material has to withstand high operating temperatures. In this contribution, the influence of heat treatment and surface conditioning of the additively manufactured Inconel 718 substrates on the thermocycling performance of suspension sprayed YSZ coatings was investigated. The different surface conditions included as-built, sandblasted and milled substrate surfaces with and without heat treatment. YSZ coatings were applied using suspension plasma spraying (SPS) with commercial available suspensions. Thermal cycling tests (FCT) at 1100°C, 1300 °C, and 1500 °C were applied to coating systems until failure occurred. The microstructures of the samples were characterized before and after thermal cycling. The performance of the coatings was mainly influenced by the coating morphology and FCT test conditions and less by the state of the AM substrates. Columnar-like YSZ SPS sprayed coatings on AM Inconel 718 substrates seemed to be a promising candidate for rocket engine applications.

LUNANOVA KICK STAGE STUDY: AN OVERVIEW OF THE SYSTEM PROPULSION TRADEOFFS Livia Ordonez Valles (ArianeGroup) Arturs Jasjukevics (ArianeGroup) Marco Wolf (ArianeGroup) Jean-Noel Caruana (ESA) Stephane Dussy (ESA) In the last years, the boom of commercial space has shaken the space sector and plunged it into a new era. These new times come along not only with a whole new portfolio of missions and services but also with a new range of capabilities and logistics required to enable them. Moreover, space exploration is also facing new challenges every day, with some of the most exciting missions ahead. Space logistics and Lunar exploration are undoubtedly the next stop of this hectic journey. ArianeGroup, willing to embrace this new vision, is already working to serve these missions by enhancing the future European launcher capabilities. Under ESA Future Launcher Preparatory Programme (FLPP), several studies are being developed, and among them, the LunaNova kick stage is the one that this paper will take care of. Kick stages are in charge of providing last mile orbit delivery to one or multiple payloads. Apart from these general to-orbit services, LunaNova shall target to offer a whole set of novel in-orbit services such as communications relay or active debris removal. The system design shall rely on innovative technologies to lower production and operational costs while improving competitiveness and commercial appeal. Storable green propellants, new tank configurations and innovative pressurisation systems have already been identified as improved alternatives to the conventional approach. Under this perspective, this paper will firstly provide an overview of the system specifications. Then, it will focus on the performed tradeoffs related to the propulsion system, i.e. pressurisation system and propellant selection. A cost-oriented approach was applied together with specific key performance parameters for each tradeoff. In the case of electric pump feeding, an estimate of the different masses of the pressurisation system was carried out for the pressure fed and electric pump-fed options. From the propellant selection point of view, hydrogen peroxide was set as the baseline oxidiser, and different analyses were carried out to assess the impact of key factors such as density and mixture ratio. Finally, a comprehensive view of the challenges and opportunities that the implementation of these identified technologies can bring to the European space ecosystem will also be provided.

The calcium aluminate electride [Ca24Al28O64]4+(e−)4 (C12A7:e−) is chemically and thermally stable in ambient atmosphere, offers strong electron donating capabilities and exhibits an intrinsic work function of 2.4 eV. Thus, it is an attractive material for electron emitter and low work function applications. For an implementation in negative hydrogen ion sources, where the electride could serve as a converter surface for the H− production, compatibility with moderate vacuum conditions and exposure to low pressure low temperature hydrogen plasmas must be ensured. Hence, the stability and work function performance of a polycrystalline C12A7:e− sample are investigated under ion source relevant vacuum (∼10−6 mbar) and plasma conditions (electron temperature ∼2 eV, electron density ∼1016m−3). The work function is measured via the photoelectric effect, showing that long-term hydrogen plasma exposure results in a steady-state surface work function of 2.75±0.10 eV. Since the electride is very sensitive to surface contaminations, an increase of the surface work function occurs as soon as the plasma is switched off. Vacuum heat treatment of the degraded C12A7:e− surface after plasma activation leads to a work function minimum of 2.9 eV for temperatures in the range of 670-770 K. Exceeding a temperature of ∼770 K leads to an increase of the C12A7:e− surface work function. The sample is stable during long-term hydrogen plasma exposure (up to 10 h total plasma-on time tested) and no plasma-induced erosion is observed.

This works presents a system level analysis of a Deorbit Kit (DK) based on electrodynamic tether technology. The analysis is focused on two relevant scenarios for deorbiting space debris: (i) Earth Observation (EO) satellites with mass in the range of 700 kg -1000 kg and initial orbital altitude of 800 km and 98° inclination, and (ii) Mega Constellation (MC) spacecraft in the order of 200 kg and initial orbit at 1200 km of altitude and 90° of inclination. The scenarios have been selected considering the orbits that are already suffering from the space debris problem or will suffer in the next future. The DK implements a bare electrodynamic tether for capturing electrons passively from the ambient plasma while three different methods are considered for emitting the electrons back to the plasma to reach a steady electrical current on the tether. The three studied options to close the electrical circuit are: (a) a hollow cathode, which has a high technological maturity but needs expellant and a little of power, (b) a thermionic emitter, which does not involve expellant but needs power, and (c) a Low Work-function Tether (LWT) that does not need neither expellant nor power because it has a segment coated with a special material that emits electrons passively through the thermionic and photoelectric effects. In order to provide a fully autonomous operation even in case of critical failure of the mother spacecraft, the DK includes a deployment mechanism, a telemetry and telecommand system, a complete Attitude Determination and Control System with attitude sensors (GNSS, sun sensors, magnetometer) and actuators (magneto torquers), solar panels and batteries. Upon activation, the DK autonomously de-tumbles the satellite, deploys a tether and carries out the satellite's de-orbiting. The study presents DK architectures, mass budgets and simulation results for the two scenarios. It is shown that a complete DK with mass below 6% the mass of the host spacecraft can deorbit EO and MC satellites in about 1.5 years and 10 years, respectively. The importance of the development of the LWT concept to enhance the simplicity and reduce the mass, power and volume budget is highlighted. This work was supported by the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No.828902 (E.T.PACK project). GSA work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357.

Vacuum polarization by electric fields is a well established fact. Assuming that anti-matter has negative gravitational properties, the fluctating electric dipoles from the quantum vacuum may also have gravitational dipolar properties. A model is developed that describes how electric fields could gravitationally polarize the vacuum causing gravitational screening or anti-screening effects. This leads to a violation of the Weak Equivalence Principle or a general mass change most notabily for elementary particles, such as the electron or positron, below but close to measured boundaries. Also a gravitational vacuum torque is predicted to act on a charged capacitor perpendicular to a gravitational field. The predictions could be verified by future laboratory experiments that could contribute on our understanding of the gravitational properties of anti-matter.

The current-dependent beam divergence at a distance of 50 μm from an indium-liquid metal ion source is derived from experimental data obtained by measuring the beam spread with a 3D Plasma diagnostic system at a distance of 10 cm from the needle tip. The observed relationship between emission current and beam divergence in vicinity of the emitting needle is used to design a focusing electrode for a field-emission electric propulsion thruster operating at currents up to 150 μA. Another application involves focused ion beam columns which may choose to forego a beam-limiting aperture, such as LMIS-based rapid machining tools with large beam currents.

Introduction and Concept Thermoacoustic travelling-wave engines combine a simple design with high efficiency and relatively low operating temperatures which makes them a promising alternative to conventional heat engines. Starting from the one-wavelength loop design proposed by Ceperley in 1979 [1] and set up from Yazaki in 1998 [2], a breakthrough in power and efficiency has been made with the TASHE from Backhaus and Swift in 1999 [3]. They introduced a more complex acoustic network, including a quarter-wavelength resonator, inertance tube, and compliance. This layout sets optimal travelling-wave phasing and impedance in the regenerator, resulting in great thermal to acoustic conversion efficiency. However, a rather large amount of acoustic power is lost in the resonator. Another option to influence phasing and impedance in the regenerator is by means of an acoustic matching stub and an increase of the cross-sectional area of the regenerator section [4], [5]. At TU Dresden, numerical simulations have shown that position and length of the stub are essential parameters for achieving high performance. They are also greatly influenced by the position of the acoustic load. Therefore, an experimental apparatus is designed to validate the simulation data.

Results from SMART-1 plasma measurements indicate that the spacecraft is, in general, floating 10 to 30 V negative with respect to the ambient plasma and that the floating potential varies with the orientation of the solar array with respect to the direction of the thrust. It is shown in this paper that a wake created behind the solar panel by the plasma generated in the plume by charge exchange and expanding toward the spacecraft may explain such a potential variation

We previously reported anomalous fiber-optic gyroscope signals observed above rotating rings at temperatures close to liquid helium. Our results suggested that the liquid helium itself may be the source of our observed phenomenon. We constructed a new cryostat experiment that allows rotating a large quantity of liquid helium together with a superconducting niobium tube. The facility is built in such a way that our gyroscope can be placed directly in the center of rotation along the axis; however, the cryostat is built around the gyroscope to allow measuring without interference of helium liquid or gas. An anomalous signal was found of similar value compared to our previous measurements with a changed sign. As this measurement was done at a different location (center position) with respect to our old setup (top position), first hints for a possible field distribution of this phenomenon can be made. However, due to lower angular velocities used in this new setup so far, our measurement resolution was close to three times the resolution of our gyroscope and hence our data represent work in progress., To appear in the SPESIF-2010 conference proceedings published by AIP

The search for frame dragging around massive rotating objects such as the Earth is an important test for general relativity and is actively pursued with the LAGEOS and Gravity Probe‐B satellites. Within the classical framework, frame dragging is independent of the state (normal or coherent) of the test mass. This was recently challenged by proposing that a large frame‐dragging field could be responsible for a reported anomaly of the Cooper‐pair mass found in Niobium superconductors. In 2003, a test program was initiated at the Austrian Research Centers to investigate this conjecture using sensitive accelerometers and fiber optic gyroscopes in the close vicinity of fast spinning rings at cryogenic temperatures. This paper will discuss the measurements recently obtained with the fiber optic gyroscopes. They show, that the angular velocity applied to the superconductor can indeed be seen on the sensors below a critical temperature. The signal amplitude is about 8 orders of magnitude below the values applied ...

In 1990, James F. Woodward, professor of physics at the California State University, provided a set of equations showing that it should be possible, via Mach's Principle, to change transiently the mass of a body. The major practical embodiment of these equations is a new kind of propellantless propulsion which could be directly applied to space exploration. The main goal of the experimental campaign here reported is to provide an independent test for the validity of this propulsion concept and compare it with previous experimental claims. We performed the study using a very sensitive thrust balance developed for field emission thrusters. Two devices developed and tested by Woodward have been characterized with our equipment. The results obtained to date do not seem to be in full agreement with the findings claimed by Woodward and collaborators. Nevertheless, the importance of such a discovery is sufficient to recommend going on with experimentation in order to reach a complete understanding of the phenomenon.

The generation of thrust using corona discharges inside a sealed Faraday-cage box is investigated. A high-voltage power supply is connected to a box via strings which allow the box to move like a pendulum. The thrust is derived from its angular position using a laser displacement meter. A 5-dimensional relativistic Maxwell theory, which couples the electromagnetic and gravitational field and predicts the generation of thrust in such a configuration, is reviewed and discussed. Only oscillations during the corona discharge but no linear thrust as predicted was observed within the detectability of the instrumentation. A brief history of similar research which resulted in the claim of a force (Biefeld-Brown effect) is evaluated and discussed. The obtained results suggest that corona wind effects were misinterpreted as a connection between gravity and electromagnetism. If such an effect exists in the presented configuration, it must be below the detection threshold of the used instrumentation.

A plasma model for Field-Emission-Electric-Propulsion (FEEP) emitters has been developed. This model is utilized in a three-dimensional full particle numerical simulation to predict the potential, ion, and neutral densities outside the spacecraft which are compared with available experimental data from laboratory vacuum chambers. A background plasma due to collisions of the fast ion beam with the neutral gas inside the chamber is added and the resulting current into the accelerator is compared. Both comparisons show a very good agreement. The background plasma with densities comparable to the ion beam density neutralizes the FEEP ion space charge very effectively. Monte-Carlo collisions between the FEEP ion and neutral beams are performed to investigate charge-exchange ions which are responsible for backflow contamination. A 3-D spatial distribution of the backflow current to the spacecraft surface is presented. The backflow is mainly concentrated on the area of the FEEP accelerator.