Radiation and Scattering of EM Waves in Large Plasmas Around Objects in Hypersonic Flight

Hypersonic flight regime is conventionally defined for Mach larger than 5; in these conditions, the flying object becomes enveloped in a plasma. This plasma is densest in thin surface layers, but in typical situations of interest it impacts electromagnetic wave propagation in an electrically large volume. We address this problem with a hybrid approach. We employ Equivalence Theorem to separate the inhomogeneous plasma region from the surrounding free space via an equivalent (Huygens) surface, and the Eikonal approximation to Maxwell equations in the large inhomogeneous region for obtaining equivalent currents on the separating surface. Then, we obtain the scattered field via (exact) free space radiation of these surface equivalent currents. The method is extensively tested against reference results and then applied to a real-life re-entry vehicle with full 3D plasma computed via Computational Fluid Dynamic (CFD) simulations. We address both scattering (RCS) from the entire vehicle and radiation from the on-board antennas. From our results, significant radio link path losses can be associated with plasma spatial variations (gradients) and collisional losses, to an extent that matches well the usually perceived blackout in crossing layers in cutoff. Furthermore, we find good agreement with existing literature concerning significant alterations of the radar response (RCS) due to the plasma envelope

Radiation and Scattering of EM Waves in Large Plasmas Around Objects in Hypersonic Flight

Hypersonic flight regime is conventionally defined for Mach> 5; in these conditions, the flying object becomes enveloped in a plasma. This plasma is densest in thin surface layers, but in typical situations of interest it impacts electromagnetic wave propagation in an electrically large volume. We address this problem with a hybrid approach. We employ Equivalence Theorem to separate the inhomogeneous plasma region from the surrounding free space via an equivalent (Huygens) surface, and the Eikonal approximation to Maxwell equations in the large inhomogeneous region for obtaining equivalent currents on the separating surface. Then, we obtain the scattered field via (exact) free space radiation of these surface equivalent currents. The method is extensively tested against reference results and then applied to a real-life re-entry vehicle with full 3D plasma computed via Computational Fluid Dynamic (CFD) simulations. We address both scattering (RCS) from the entire vehicle and radiation from the on-board antennas. From our results, significant radio link path losses can be associated with plasma spatial variations (gradients) and collisional losses, to an extent that matches well the usually perceived blackout in crossing layers in cutoff. Furthermore, we find good agreement with existing literature concerning significant alterations of the radar response (RCS) due to the plasma envelope

System design study of a VLEO satellite platform using the IRS RF helicon-based plasma thruster

To achieve a feasible lifetime of several years, most satellites are deployed in orbits higher than 400 km. Drag of residual atmosphere causes a slow orbit decay, resulting in the deorbit of the spacecraft. However, e.g. optical instruments or communication devices would significantly benefit from lower altitudes in the range of 150–250 km. A solution to achieve this could be the application of atmosphere-breathing electric propulsion (ABEP), where the residual atmosphere is used to generate continuous thrust that compensates the drag.Within the EU-funded DISCOVERER project, the Institute of Space Systems (IRS) developed an electrode-less RF Helicon-based Plasma Thruster (IPT) suitable for such applications. Ignition and preliminary discharge characterizations of the IPT have been carried out at IRS facilities, using argon, nitrogen and oxygen. To further characterize the plasma plume, a torsional pendulum has been designed to determine the (local) momentum flux in the plasma jet, as well as a three-axis magnetic B-dot probe to carry out time-varying magnetic field measurements. Various intake designs were investigated, opening the possibility to conduct studies on potential satellite platforms within the frame of the ESA-funded project RAM-CLEP.A design study for an Earth Observation and Telecommunication satellite operating at 150–250 km with an extended mission lifetime is currently being carried out. The first system assessment focused on the comparison of different spacecraft configurations (“slender body” and “flat body”) and intake designs (specular or diffuse) with regard to overall drag and ABEP performance requirements.In this contribution, the design approaches for the current thruster and the diagnostic methods are depicted. Moreover, the current status of the system assessment is presented. Upcoming experimental studies of the ABEP system e.g. within the ESA-project RAM-CLEP and additional activities planned on system assessment are outlined.<br/

Challenges for the Heatshield Development of Sample Return Missions - An Overview on European Sample Return Studies and Requirements

This presentation was part of the session : Sample Return ChallengesSixth International Planetary Probe WorkshopThe atmospheric entry of the Earth return capsule of sample return mission is one of the most critical phases of sample return missions. The Earth return from extraterrestrial bodies (e.g. Mars, comets or asteroids) involves a hyperbolic entry with entry velocities of typically above 12 km/s, resulting in peak heat fluxes in the order of 10 MW/m(2) and heat loads up to 200 MJ/m(2). While during a classical re-entry from Earth-orbit the heat flux is basically limited to convective fluxes, additionally radiative fluxes become increasingly important at entry velocities above 12 km/s. In addition, since the Earth return capsule is subject to a "double" delta-V (to the object and back to Earth), the return capsule and its heatshield have to conform to a very stringent mass budget. Further, surface recession due to ablation and abrasion effects needs to remain limited in order to guarantee the aerodynamic stability. This requires the availability of a highly efficient light-weight ablator material. In a dedicated study a screening of existing European ablators was performed to assess their suitability. Unfortunately, it turned out that none of the materials, which were developed in front of very different requirements, is suitable to sustain the very high heat fluxes while coping with the mass requirement. Dedicated development is therefore initiated to tailor materials towards the stringent requirements. Another important aspect is the availability of plasma facilities for the qualification of the materials. Such high enthalpy facility needs to be able to reproduce the extreme heat fluxes at representative dynamic pressure levels and simulating the high radiation level. Additionally it would be beneficial to assess the dynamic stability of the entry capsule using free flight ballistic tests. The paper will provide an overview on the main challenges involved in the development of the heatshield for the Earth re-entry capsule of sample return missions, resulting from different ESA studies to Mars and asteroids. This will include system aspects, the choice of the TPS material and its qualification, flight path stability and reliability. Preliminary technology roadmaps will also be presented

Seksualiteit bespreken in de klas, hoe doe je dat?: Praktische tips voor docenten

Docenten kunnen een belangrijke rol spelen bij de gezonde relationele en seksuele ontwikkeling van leerlingen. Aandacht voor dit onderwerp in de klas kan in specifieke themalessen, maar nog belangrijker is om aandacht te besteden aan relationele en seksuele ontwikkeling binnen het reguliere lesprogramma, als het thema ter sprake komt in de klas. Geroezemoes van leerlingen over seks of actualiteiten in het nieuws, kunnen een aanknopingspunten zijn om in gesprek te gaan met leerlingen. Deze factsheet geeft een overzicht van de belangrijkste tips voor docenten, gebaseerd op het rapport 'Seksualiteit bespreken in de klas, hoe doe je dat?

Continuing Challenges in Physico-Chemical Modelling for Hypersonic CFD

The rapid and significant advances in computational power both in terms of hardware and software in recent years and the resurgence in 1980's of interest in future concepts for hypersonic transportation systems have identified CFD as an important and indispensable tool for R & D in the field. To take advantage of this valuable tool for reliable simulations and predictions one must pay careful attention to the quality and validity of the modelling inputs that go into the development of the CFD codes while striving to improve their numerical accuracy and algorithmic efficiency. Whereas the CFD has made significant progress in speed and scope for numerical analysis of the larger and more complex PDE systems needed for treating relevant hypersonic flows, the earlier state-of-the art conventional physico-chemical models and input data have shown the need for further improvements. Some of the 'rate-limiting' steps in achieving predictive capability via CFD are related to inadequacies in the physico-chemical models and associated data used in describing the multi-species high-temperature chemically reacting gas flows occurring in and around hypersonic vehicles. Some of these continuing modelling challenges are briefly reviewed here with typical examples from current literatur