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\DOI{10.5802/crmeca.229}
\datereceived{2023-10-04}
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%\makeatletter
%\def\TITREspecial{\relax}
%\def\cdr@specialtitle@english{Physical Science in Microgravity within the Thematic Group Fundamental and Applied Microgravity}
%\def\cdr@specialtitle@french{Sciences physiques en microgravit\'e au sein du GDR Micropesanteur Fondamentale et Appliqu\'ee}
%\makeatother

\title{Foreword}

%\author{\firstname{Olga} \lastname{Budenkova}\IsCorresp}
%\address{France}
%\email[O. Budenkova]{olga.budenkova@simap.grenoble-inp.fr}

\author{\firstname{Catherine} \lastname{Colin}\CDRorcid{0000-0001-9985-9488}}
\address{IMFT, All\'ee Camille Soula, 31400 Toulouse, France}

\author{\firstname{Guillaume} \lastname{Legros}\CDRorcid{0000-0003-4245-8258}}
\address{CNRS-ICARE / Univ. Orl\'eans, 1C Avenue de la Recherche Scientifique, 45071~Orl\'eans Cedex 2, France}

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\xsection{}

As the editors of this special issue, we are delighted to introduce a
selection of recent achievements associated with the French
Research Network (\textit{Groupement de Recherche}) on Fundamental and
Applied Microgravity (GdR CNES/CNRS 2799). Last year marked the 30th
anniversary of this group, making it the longest-standing GdR
accredited by the \textit{Centre National de la Recherche
Scientifique} (CNRS). To open the 4th decade of our group,
the \textit{Comptes-Rendus M\'{e}canique de l'Acad\'{e}mie des
Sciences} offered the invigorating opportunity of this special issue.

Over the past 30 years, a dedicated French aircraft has played a
crucial role in evaluating theoretical and numerical investigations
through experimental work conducted during parabolic flights to
simulate microgravity conditions. From the initial \textit{Caravelle}
in the 90's to the current \textit{Airbus A310}, three airplanes were
specifically equipped to be full-time dedicated to parabolic flights.
As highlighted in the first paper of this special issue, these
facilities located on the French ground show---among others---the
unfailing support of the French Space Agency (\textit{CNES}) which we
celebrate here.

Many processes are affected by gravity, and our understanding may be
blurred by some gravitational effects. As an appealing illustration,
the cover page displays a sequence of frames captured by a fast camera
imaging the onset of an instability that propagates over the initially
smooth sheet of an expanding premixed spherical flame. For sure, the
directional feature of buoyancy makes it a serious trigger leading to
the onset. So what if this trigger vanishes? Throughout a wide range of
fields related to mechanics, the present issue compiles recent advances
that pave the way to further understanding of fundamental processes,
such as phase change or complex flows in the absence of gravity.

In the coming decade, space exploration that is clearly ambitioned by
the major space agencies today also pushes new perspectives into our
group. For this reason, our community now contributes at an
international level to projects aiming at spacecraft safety or life
sustainability. Papers related to fire safety or plant growth
illustrate here these contributions.

Beyond these crucial issues, we also intend to celebrate a human
adventure that a few generations of scientists strongly committed to.
With this respect, we are deeply grateful to Christophe Delaroche, who
retired one year ago after years serving as the Head of
the Physical Sciences in microgravity Department at CNES. We also
express a moved homage to our colleague Professor~Pierre~Haldenwang who
passed away two years ago after serving two terms as president of our
group. We are convinced that Pierre's inspiring
spirit will continue to guide our work for a long time. At the very
least, the birth of our brand new website echoes this will:


\vspace*{1pc}

\hspace*{6.5cm}
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\url{https://gdr-mfa.fr/}

\vspace*{12pt}

Catherine Colin

Director of French Research Network on\newline\hspace*{1pc} Fundamental and Applied Microgravity

France

\textemail{colin@imft.fr}

\vspace*{12pt}

Guillaume Legros

Deputy director of French Research Network on\newline\hspace*{1pc} Fundamental and Applied Microgravity

France

\textemail{guillaume.legros@cnrs-orleans.fr}

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