VUV to IR Emission Spectroscopy and Interferometry Diagnostics for the European Shock Tube for High-Enthalpy Research.

The European Shock Tube for High-Enthalpy Research is a new state-of-the-art facility, tailored for the reproduction of spacecraft planetary entries in support of future European exploration missions, developed by an international consortium led by Instituto de Plasmas e Fusão Nuclear and funded by the European Space Agency. Deployed state-of-the-art diagnostics include vacuum-ultraviolet to ultraviolet, visible, and mid-infrared optical spectroscopy setups, and a microwave interferometry setup. This work examines the specifications and requirements for high-speed flow measurements, and discusses the design choices for the main diagnostics. The spectroscopy setup covers a spectral window between 120 and 5000 nm, and the microwave interferometer can measure electron densities up to 1.5 × 1020 electrons/m3. The main design drivers and technological choices derived from the requirements are discussed in detail herein.

Earth-viewing satellite perspectives on the Chelyabinsk meteor event.

Large meteors (or superbolides [Ceplecha Z, et al. (1999) Meteoroids 1998:37-54]), although rare in recorded history, give sobering testimony to civilization's inherent vulnerability. A not-so-subtle reminder came on the morning of February 15, 2013, when a large meteoroid hurtled into the Earth's atmosphere, forming a superbolide near the city of Chelyabinsnk, Russia, ∼1,500 km east of Moscow, Russia [Ivanova MA, et al. (2013) Abstracts of the 76th Annual Meeting of the Meteoritical Society, 5366]. The object exploded in the stratosphere, and the ensuing shock wave blasted the city of Chelyabinsk, damaging structures and injuring hundreds. Details of trajectory are important for determining its specific source, the likelihood of future events, and potential mitigation measures. Earth-viewing environmental satellites can assist in these assessments. Here we examine satellite observations of the Chelyabinsk superbolide debris trail, collected within minutes of its entry. Estimates of trajectory are derived from differential views of the significantly parallax-displaced [e.g., Hasler AF (1981) Bull Am Meteor Soc 52:194-212] debris trail. The 282.7 ± 2.3° azimuth of trajectory, 18.5 ± 3.8° slope to the horizontal, and 17.7 ± 0.5 km/s velocity derived from these satellites agree well with parameters inferred from the wealth of surface-based photographs and amateur videos. More importantly, the results demonstrate the general ability of Earth-viewing satellites to provide valuable insight on trajectory reconstruction in the more likely scenario of sparse or nonexistent surface observations.

A Fast Thermal 1D Model to Study Aerospace Material Response Behaviors in Uncontrolled Atmospheric Entries.

A preliminary thermal 1D numerical model for studying the demise behavior of stainless steel 316L, silicon carbide (SiC) and carbon fiber reinforced polymer (CFRP) during uncontrolled atmospheric entry is proposed. Test case modeling results are compared to experimental data obtained in the framework of ESA Clean Space initiative: material samples were exposed to different heat flux conditions using the Plasma Wind Tunnel (PWT) facilities at the Institute of Space Systems (IRS) of the University of Stuttgart. This numerical model approximates the heating history of the selected materials by simulating their thermal response and temperature profiles, which have trends similar to the experimental curves that are found. Moreover, when high heat flux conditions are considered, the model simulates the materials' mass loss due to the ablation process: at the end of the simulation, the difference between the experimental and the modeled results is about 17% for CFRP and 35% for stainless steel. To reduce the model's uncertainties, the following analysis suggests the need to consider the influence of adequate material thermophysical properties and the physical-chemical processes that affect the samples' temperature profile and mass loss.