Aerospace America year in review article for Thermophysics covering the COMARS data from ExoMars, meteor testing in arcj ets and potential energy surface calculations

Brandis, Aaron M.

Chaudhry, Ross

NASA Technical Reports Server

Contact: Aaron Brandis: aaron.m.brandis@nasa.gov   650 604 0888 
 
 [headline] Validating advanced thermophysics models 
 
BY AARON BRANDIS, ROSS CHAUDHRY 
 
In 2017, the thermophysics community obtained aerothermal flight data at Mars, improved the 
ability to use fundamental chemistry data in design tools, and investigated meteor entry in high 
enthalpy experimental facilities. 
 
Researchers from the European Space Agency’s ExoMars mission presented flight data from the 
Schiaparelli module’s entry into the Martian atmosphere at the International Planetary Probe 
Workshop held in The Hague, Netherlands, June 2017. The data obtained during Schiaparelli’s 
descent will be invaluable for validating models used to design thermal protection systems for 
future Mars missions. Reliable flight data is essential for the optimization of heat shield design, 
which in general is carried out with relatively high safety margins. High margins compensate for 
the large uncertainties associated with simulation tools when used to predict aerothermal loads 
on a spacecraft. In particular, radiative heating is created by hot carbon-dioxide molecules in the 
flow around the back-shell. This radiative heating mechanism has not been included in most 
previous Mars mission designs. Therefore, DLR, the German Aerospace Center, developed the 
Combined Aerothermal and Radiation Sensor package, called COMARS+, to measure the 
aerothermal and radiative loads at different back-shell positions on Schiaparelli. COMARS+ 
consisted of three combined aerothermal sensors, one broadband radiometer sensor and an 
electronic box. Due to the failed landing of Schiaparelli it was not possible to retrieve the 
complete data package. However, communications between the Schiaparelli module and the 
orbiter during entry allowed data to be transmitted at ten trajectory points. Ongoing post flight 
analysis, including tests in the arc jet facility L2K at DLR Cologne, provide unique data for 
future Martian missions. 
 
Computational chemists at the University of Minnesota in July and October published potential 
energy surfaces, or PESs, for O2 + O2 and O2 + O interactions relevant to conditions 
representative of hypersonic speeds. PESs are high-quality fits of the atomic forces that exist 
during molecular collisions and are used to investigate the dynamics of a dissociating gas, which 
are often in thermal non-equilibrium. These investigations lead to an improved understanding of 
reaction rates implemented in computational fluid dynamic simulations. Researchers in 
aerospace departments at the University of Illinois at Urbana-Champaign and the University of 
Minnesota use PESs with two different methods to predict non-equilibrium internal energy 
distributions. In a collaboration presented at AIAA’s 2017 Aviation/Thermophysics conference, 
these two methods were demonstrated to be consistent for the case of nitrogen dissociation. PESs 
are now available for many important reactions relevant to Earth entry, and by correctly 
modeling non-equilibrium and its effect on chemical kinetics, this work is expected to lower 
uncertainty margins and enable novel vehicle design. 
 
Thermophysics research groups this year leveraged high-enthalpy experimental facilities 
traditionally used for testing spacecraft thermal protection system materials to study the complex 
phenomena of a meteor entering Earth’s atmosphere. Researchers in Japan studied synthetic 
https://ntrs.nasa.gov/search.jsp?R=20180001526 2019-08-30T12:24:59+00:00Z
meteorites in an arc heated wind tunnel in preparation for a planned artificial meteor shower at 
the 2020 Olympic games. Groups in Europe, at the von Karman Institute and the University of 
Stuttgart, utilized plasma wind tunnel facilities, including the Plasmatron and PWK1 
respectively, to study emission spectra from meteorite samples. At NASA Ames Research 
Center, meteoroid ablation was studied in detail in the Interaction Heating Facility in July 2017 
to aid in developing models for asteroid threat assessment. The data from all of these 
experiments are being used to advance state-of-the-art numerical modeling of meteor entries. 
 
By obtaining aerothermal heating flight data at Mars, understanding how to efficiently use 
elaborate quantum chemistry data in production design tools, and investigating the physics of 
meteor entry in high enthalpy ground tests, the ability to validate complex thermophysics models 
is greatly improved. 
 
Contributors: Ali Guelhan and Eric Stern 
 
 
The aerothermal and broadband radiometer sensors on COMARS+ were installed on the 
Schiaparelli spacecraft’s back cover to measure the aerothermal and radiative loads at different 
backshell positions. 
 


Validating Advanced Thermophysics Models

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