Aerothermodynamics
Aerothermodynamics is the study of flows at high Mach number (typically greater than 5), where significant chemical and thermodynamic phenomena appear due to the extremely high energy owned by the flow. This kind of flows are typically encountered by Earth re-entry vehicles, like the Space Shuttle, or for landing on other planets with atmosphere. Typical examples of the interested phenomena are molecular dissociation, thermo-chemical non-equilibrium, ionization, radiation, electro-magnetic driven phenomena, etc. The effects on the vehicles usually include:
- material effects: due to the very high temperatures that can be reached on some parts of the vehicle (up to 2000 K) and/or particular reactions that can be enhanced, for example by catalysis on the vehicle surface, the material and/or structural performance is strongly degraded;
- aerodynamic effects: due to the complex patterns of shock-wave/boundary-layer interaction, the vehicle drag or the forces applied on/by its control surfaces can be very different from what expected;
- electro-magnetic effects: due to ionization, communication problems (i.e. black-out) can happen. Also, useful net effects can be obtained by expoiting the weakly ionized plasma that is naturally created around the vehicle.
It is impossible to re-create a perfect flow similitude in ground-test facilities without replicating in full scale all of the involved parameters. Experimental characterization on ground is limited by the capability to provide a certain total enthalpy (i.e., heating) and the available test duration. Alta's High-Enthalpy Arc-heated Tunnel (HEAT) provides accurate modeling in a scaled configuration at limited cost per run and is complemented by the Laser Induced Fluorescence (LIF) diagnostic system.
Current activities in aerothermodynamics at Alta include:
- CAST (Configurazioni Aerotermodinamiche avanzate per Space Transportation): funded by ASI, CAST is a 4-year programme aimed at realizing an advanced design tool for entry vehicles and launchers. Alta coordinates all of the experimental acitivities. Four experiments will be carried out within the HEAT and LIF facilities.
- EXPERT (Development and Qualification of in Flight Test Measurement Techniques): currently in phase C/D, EXPERT is a programme funded by the European Space Agency for the flight of a ballistic capsule equipped by several diagnostics systems in order to obtain accurate in-flight aerothermodynamic data. Alta is the responsible of payload 12 on the vehicle, for the measure of base pressure, temperature and heat flux.
ATLLAS (Aerodynamic and Thermal Load Interactions with Lightweight Advanced Materials for High Speed Flight): funded by the European Commission, ATLLAS is aimed at the design of two future supersonic commercial vehicles, at Mach 3 and Mach 6 cruise speed respectively. Alta is in charge of the experimental characterization of the laminar-turbulent transition region for the two vehicles in different configurations using accurate ultra-fast temperature and heat flux measurement.