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Description
ESTHER is a new state-of-the-art combustion driven shock tube developed for supporting future ESA planetary exploration missions. The facility has underwent a long development cycle which came to its term in 2019, with the completion of assembly operations and the moving to the qualification and testing phases. Key requirements for this facility, as required by ESA include performance, cleanliness, repeatability, and high-turnaround time. These are all enforced through the innovative design of the facility, tailored during its long-winded development time.
The ESTHER shock-tube assembly is composed of a 47l combustion chamber driver (1.6m length, 200mm diameter) filled to an initial pressure up to 100bar with He/H2/O2 gas mixtures, and ignited using a Nd:Yag laser to a final pressure of 600bar, being the first laser-ignited facility of its kind in the world.
An intermediary compression tube of 130mm diameter is connected to the combustion chamber through a diaphragm designed to burst at a predetermined pressure. The compression/acceleration tube is filled with He gas at pressures of about 0.01–1bar.
The compression tube is in turn connected to the shock-tube test section (80mm diameter) through a second diaphragm designed to burst at a predetermined pressure. The shock-tube is filled with a test gas at pressures of about 0.1mbar, representative of the altitudes where planetary entries occur. The shock-wave propagates in this section at velocities that may exceed 12km/s in air, or 18km/s for lighter H2/He gases.
Pressure sensor stations are located at different stages of the shock-tube, detecting the rise of pressure in the wake of the shock-wave. This allows for developing a triggering system initiating high-speed (10–100MHz rated), time-dependent spectroscopic measurements at the test-section windows (25mm diameter) of the radiation emitted and absorbed in the wake of the shockwave.
A 1,000L dump tank recovers all the gases flowing in the wake of the shock-wave. The H2O liquid phase is drained off, while the remaining contaminated He mixture is evacuated by the pumping system, after which the shock-tube can be opened for cleaning operations and the replacement of the diaphragms.
The facility has a set of state-of-the art spectroscopic instrumentation ranging from the VUV to the IR regions, funded by two companion contracts from ESA, allowing for the facility to provide unparalleled data for the radiation of atmospheric entry flows, allowing improved knowledge of the physical-chemical processes of atmospheric entry, and furthering the understanding of atmospheric entry science and technology.
