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A. del Val et al.
the crewed space program to send human beings to Mars and bring them home
safely. Space agencies are also facing technological problems when dealing with
residues of space flight. More than 30,000 space debris constitute today threats for
space systems in orbit, such as the International Space Station and active satellites
for observation and communication, as well as for humankind when debris, not fully
destroyed during re-entry, impact the Earth. Facing these problems requires in-depth
knowledge of the systems and phenomena involved.
Orbital velocities were predicted by Newton in the seventeenth century when
conceiving the equations for motion under gravitational forces. These equations
imply the existence of a velocity threshold above which an object could fly forever
(ideally). Low Earth Orbits (LEO) are the most common among satellites and space
stations with an average orbital velocity of 7 km/s. Traveling beyond the orbit of our
planet means more energy, interplanetary velocities are of the order of 11 km/s. All
this amount of kinetic and potential energy, dictated by orbital mechanics, will be
dissipated when a space vehicle enters dense planetary atmospheres. The bulk of this
energy is exchanged during the entry phase by converting the kinetic energy of the
vehicle into thermal energy in the surrounding atmosphere through the formation
of a strong bow-shock ahead of the vehicle. In general, about 90% of the energy
dissipated to the atmosphere is carried away from the vehicle through convection
and radiation, leaving about 10% to be absorbed back into the vehicle as thermal
energy. A Thermal Protection System (TPS) is used to mitigate this heat load and
ensure that the temperature limits of critical components on board are not exceeded
during the entry phase.
The aerothermal environment surrounding a vehicle during atmospheric entry is
extremely complex. As such, prediction of the heating rate which is experienced
by the thermal protection system remains an imperfect art, leading to very large
safety margins for the vehicle design. Failing to correctly predict the heat loads
and associated material response of the TPS during the design phase can lead to
catastrophic mission failure.
To address this problem, experimental facilities capable of generating high-speed
and plasma flows are developed to study different aspects of atmospheric entry
flows, together with physico-chemical models used to describe the state of the
flow at a given time and conditions. Numerical methods as well are constantly
improved to obtain approximate solutions of this complex system. The delicate
interplay of experiments, models, and numerical methods represents the main source
of knowledge about the system and its coupling mechanisms among the different
physical phenomena present.
Uncertainties on the margin definition are present at every step of the design
chain posing a high need for uncertainty quantification methods to analyze our
results, validate our models and give us the way for improvement and research to be
done.
A. del Val et al.
the crewed space program to send human beings to Mars and bring them home
safely. Space agencies are also facing technological problems when dealing with
residues of space flight. More than 30,000 space debris constitute today threats for
space systems in orbit, such as the International Space Station and active satellites
for observation and communication, as well as for humankind when debris, not fully
destroyed during re-entry, impact the Earth. Facing these problems requires in-depth
knowledge of the systems and phenomena involved.
Orbital velocities were predicted by Newton in the seventeenth century when
conceiving the equations for motion under gravitational forces. These equations
imply the existence of a velocity threshold above which an object could fly forever
(ideally). Low Earth Orbits (LEO) are the most common among satellites and space
stations with an average orbital velocity of 7 km/s. Traveling beyond the orbit of our
planet means more energy, interplanetary velocities are of the order of 11 km/s. All
this amount of kinetic and potential energy, dictated by orbital mechanics, will be
dissipated when a space vehicle enters dense planetary atmospheres. The bulk of this
energy is exchanged during the entry phase by converting the kinetic energy of the
vehicle into thermal energy in the surrounding atmosphere through the formation
of a strong bow-shock ahead of the vehicle. In general, about 90% of the energy
dissipated to the atmosphere is carried away from the vehicle through convection
and radiation, leaving about 10% to be absorbed back into the vehicle as thermal
energy. A Thermal Protection System (TPS) is used to mitigate this heat load and
ensure that the temperature limits of critical components on board are not exceeded
during the entry phase.
The aerothermal environment surrounding a vehicle during atmospheric entry is
extremely complex. As such, prediction of the heating rate which is experienced
by the thermal protection system remains an imperfect art, leading to very large
safety margins for the vehicle design. Failing to correctly predict the heat loads
and associated material response of the TPS during the design phase can lead to
catastrophic mission failure.
To address this problem, experimental facilities capable of generating high-speed
and plasma flows are developed to study different aspects of atmospheric entry
flows, together with physico-chemical models used to describe the state of the
flow at a given time and conditions. Numerical methods as well are constantly
improved to obtain approximate solutions of this complex system. The delicate
interplay of experiments, models, and numerical methods represents the main source
of knowledge about the system and its coupling mechanisms among the different
physical phenomena present.
Uncertainties on the margin definition are present at every step of the design
chain posing a high need for uncertainty quantification methods to analyze our
results, validate our models and give us the way for improvement and research to be
done.