Novel heat flux controlled surface cooling for hypersonic flight

Abstract This paper presents a new method in theory and experiment to adjust the transpiration cooling based on the actual measured heat flux. This is particularly useful in extreme heating environments, e.g. atmospheric entry flight or combustion chamber applications. In such environments, usually cooling is set constant based on the vehicle design, yet a mass efficient and performant cooling is sought after. We present a method with real-time surface heat flux determination of the transpiration cooled wall and an automatic adjustment of the cooling. The heat flux is determined based on a system identification process. The heat flux measurement itself is derived non-intrusively from the measurement of pressure inside the plenum, i.e. the region between mass flow controller and porous wall. The particular advantage of this system is that the heat shield material is not weakened by any sensor system and its performance is optimized with respect to cooling needed at a certain heating level. Another new feature of the pressure heat flux transformation is the attenuation of a destabilizing positive feedback loop, where the transpiration cooling controller’s output (i.e. mass flow rate) strongly influences its input (i.e. plenum pressure). We describe the identification of the model parameters for the heat flux determination, which are found and verified by a calibration approach. The controlled cooling was demonstrated in a hot air plasma flow with a reference heat flux of up to 1.4 MW/m $$^2$$ 2 . The results show the performance and verify the applicability in a real flight environment

An open carbon–phenolic ablator for scientific exploration

Abstract Space exploration missions rely on ablative heat shields for the thermal protection of spacecraft during atmospheric entry flights. While dedicated research is needed for future missions, the scientific community has limited access to ablative materials typically used in aerospace. In this paper, we report the development of the HEFDiG Ablation-Research Laboratory Experiment Material (HARLEM), a carbon–phenolic ablator designed to supply the need for ablative materials in laboratory experiments. HARLEM is manufactured using polyacrylonitrile-based carbon fiber preforms and a simplified processing route for phenolic impregnation. We characterized the thermal protection performance of HARLEM in arcjet experiments conducted in the plasma wind tunnel PWK1 of the Institute of Space Systems at the University of Stuttgart. We assessed the performance of the new material by measuring surface recession rate and temperature using photogrammetry and thermography setups during the experiments, respectively. Our results show that HARLEM’s thermal protection performance is comparable to legacy carbon–phenolic ablators that have been validated in different arcjet facilities or in-flight, as demonstrated by calculations of the effective heat of ablation and scanning electron microscopy of as-produced samples. In-house manufacturing of carbon–phenolic ablators enables the addition of embedded diagnostics to ablators, allowing for the acquisition of data on internal pressure and more sophisticated pyrolysis analysis techniques

Aperçu du projet MetSpec - météores artificiels en test au sol

International audienceWe provide an overview of the MetSpec project, which aims to connect meteorite ablation laboratory experiments with meteor spectral observations in the atmosphere aiming at the development of a methodology to identify incoming planetary material distribution into the Earth’s atmosphere. We have selected 28 meteorites of different types to represent known planetary material compositions coming from asteroids, Vesta, Mars and the Moon. Some samples have been tested twice which resulted in overall 31 experiments. Three distinct test campaigns were realized in 2020, 2021 and 2022 with the High Enthalpy Flow Diagnostics Group in the Plasma Wind Tunnel PWK1 where they have developed a unique testing scenario. During the last and most elaborated campaign, 16 cameras observed the artificial meteors in the laboratory. Besides videos and online live streaming, instruments included several spectrometers, and optical and imaging instruments covering UV, visible and IR spectral range. This special collection in Icarus collects the resulting output from the different instruments and results. This overview article provides an introduction and summarizes the main findings of the experimental campaigns.Nous présentons une vue d'ensemble du projet MetSpec, qui vise à relier les expériences d'ablation de météorites en laboratoire aux observations spectrales de météorites dans l'atmosphère, dans le but de développer une méthodologie permettant d'identifier la distribution des matériaux planétaires entrants dans l'atmosphère terrestre. Nous avons sélectionné 28 météorites de différents types pour représenter les compositions connues de matériaux planétaires provenant d'astéroïdes, de Vesta, de Mars et de la Lune. Certains échantillons ont été testés deux fois, ce qui a donné lieu à 31 expériences au total. Trois campagnes d'essais distinctes ont été réalisées en 2020, 2021 et 2022 avec le High Enthalpy Flow Diagnostics Group dans la soufflerie à plasma PWK1, où ils ont développé un scénario d'essai unique. Au cours de la dernière campagne, la plus élaborée, 16 caméras ont observé les météores artificiels dans le laboratoire. Outre les vidéos et la diffusion en direct, les instruments comprenaient plusieurs spectromètres et des instruments optiques et d'imagerie couvrant les gammes spectrales de l'UV, du visible et de l'IR. Cette collection spéciale d'Icarus rassemble les résultats obtenus par les différents instruments. Cet article présente une introduction et résume les principaux résultats des campagnes expérimentales