269 research outputs found
Performance Evaluation of a Novel Inductive Atmosphere-Breathing EP System
Challenging space mission scenarios include those in low altitude orbits, where the atmosphere creates significant drag to the S/C and forces their orbit to an early decay. An atmosphere-breathing electric propulsion system (ABEP) ingests the residual atmosphere through an intake and uses it as propellant for an electric thruster that compensates the drag. Theoretically applicable to any planet with atmosphere, the system might allow to orbit for an unlimited period without carrying propellant on-board. IRS has several decades of heritage on the development of inductively heated plasma generators (IPG). Such devices are electrodeless, therefore issues of potential electrode erosion are eliminated. This paper deals with the complete refurbishment of a facility that was previously used for RIT testing, for the use of IPG6-S, a small scale IPG with an input power up to 3.5 kW. This facility allows more reliable test conditions. First operational and performance tests of IPG6-S have been performed. IPG6-S serves as test bed for the development of an inductive plasma thruster (IPT) for ABEP application. A newly designed water-cooled de Laval nozzle has been built and applied to IPG6-S. The nozzle is modular, it has the possibility of having various configurations so to assess its performance in terms of plasma acceleration and thrust production. Within this paper plasma plume energy has been measured by means of a cavity calorimeter and correlated to current, power, and pressure in the injector head.Peer ReviewedPostprint (published version
Influence of Specific Energy Inhomogeneity on the CO2 Splitting Performance in a High-Power Plasma Jet
Plasma-based CO2 conversion is a promising pathway towards greenhouse gas
recycling. In the corresponding research field, various types of plasma
reactors are applied for carbon dioxide dissociation. So far, spatial
inhomogeneities of the specific energy (SEI) distribution in plasma generators,
e.g., induced by non-uniform heating or an inhomogeneous mass distribution, are
not the focus of the investigations. In this work, the spatial inhomogeneity of
mass-specific enthalpy in the plasma jet of the inductive plasma generator IPG4
at the Institute of Space Systems (IRS) is examined. For this, the mean
mass-specific enthalpy as well as the radial distribution of the local enthalpy
are measured using plasma probes. Moreover, the influence of the determined
specific enthalpy inhomogeneity on the CO2 splitting performance is quantified.
It is shown that an inhomogeneous radial distribution of the specific energy
can significantly lower the carbon dioxide conversion, compared to a
homogeneous case. With regards to IPG4, the performance reduction is 16 %.Comment: 30 pages, 12 figure
Satellite design optimization for differential lift and drag applications
Utilizing differential atmospheric forces in the Very Low Earth Orbits (VLEO)
regime for the control of the relative motion within a satellite formation is a
promising option as any thrusting device has tremendous effects on the mission
capacity due to the limited weight and size restrictions of small satellites.
One possible approach to increase the available control forces is to reduce the
mass of the respective satellites as well as to increase the available surface
area. However, satellites of these characteristics suffer from rapid orbital
decay and consequently have a reduced service lifetime. Therefore, achieving
higher control forces is in contradiction to achieving a minimum orbital decay
of the satellites, which currently represents one of the biggest challenges in
the VLEO regime. In this work, the geometry of a given reference satellite, a
3UCubeSat, is optimized under the consideration of different surface material
properties for differential lift and drag control applications while
simultaneously ensuring a sustained VLEO operation. Notably, not only the
consideration of sustainability but also the optimization with regard to
differential lift is new in literature. It was shown that the advantageous
geometries strongly depend on the type of gas-surface interaction and thus, two
different final designs, one for each extreme type, are presented. In both
cases, improvements in all relevant parameters could be achieved solely via
geometry adaptions
An analysis tool for collision avoidance manoeuvres using aerodynamic drag
Aerodynamic collision avoidance manoeuvres provide an opportunity for
satellites in Low Earth Orbits to reduce the risk during close encounters. With
rising numbers of satellites and objects in orbit, satellites experience close
encounters more frequently. Especially those satellites without thrusting
capabilities face the problem of not being able to performimpulsive evasive
manoeuvres. For satellites in Low Earth Orbits, though, perturbing forces due
to aerodynamic drag may be used to influence their trajectories, thus offering
a possibility to avoid collisions. This work introduces a tool for the analysis
of aerodynamic collision avoidance manoeuvres. Current space-weather data are
employed to estimate the density the satellite encounters. Achievable in-track
separation distances following a variation of the ballistic coefficient through
a change in attitude are then derived by evaluating an analytical equation from
literature. Considering additional constraints for the attitude, e.g., charging
phases, and uncertainties in the used parameters, the influence of a manoeuvre
on the conjunction geometry and the collision probability is examined. The
university satellite Flying Laptop of the University of Stuttgart is used as an
exemplary satellite for analysis, which show the general effectiveness of
evasive manoeuvres employing aerodynamic drag. First manoeuvring strategies can
be deducted and the influence of parameter uncertainties is assessed.Comment: 18 pages, 13 figure
Acute pancreatitis caused by impaction of hydatid membranes in the papilla of Vater: a case report
Acute pancreatitis is a rare complication of hydatidosis and the successful use of endoscopic sphincterotomy associated with extraction of hydatid membranes has been rarely reported. We describe a young man who developed acute pancreatitis after rupture of an echinococcus cyst, located at the left hepatic lobe, into the biliary tract. The cause of pancreatitis was confirmed by endoscopic retrograde cholangiopancreatography, which revealed the presence of a daughter cyst impacted in the major papilla. After sphincterotomy and removal of hydatid membranes from the biliary tract, the patient presented rapid resolution of pancreatitis and made an uneventful recovery
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