  High angular resolution images obtained with a hypertelescope can strongly
constrain the radiative-hydrodynamics simulations of red supergiant (RSG)
stars, in terms of intensity contrast, granulation size and temporal variations
of the convective motions that are visible on their surface. The
characterization of the convective pattern in RSGs is crucial to solve the
mass-loss mechanism which contributes heavily to the chemical enrichment of the
Galaxy. We show here how the astrophysical objectives and the array
configuration are highly dependent to design a hypertelescope. For a given
field of view and a given resolution, there is a trade-off between the array
geometry and the number of required telescopes to optimize either the (u,v)
coverage (to recover the intensity distribution) or the dynamic range (to
recover the intensity contrast). To obtain direct snapshot images of Betelgeuse
with a hypertelescope, a regular and uniform layout of telescopes is the best
array configuration to recover the intensity contrast and the distribution of
both large and small granulation cells, but it requires a huge number of
telescopes (several hundreds or thousands). An annular configuration allows a
reasonable number of telescopes (lower than one hundred) to recover the spatial
structures but it provides a low-contrast image. Concerning the design of a
pupil densifier to combine all the beams, the photometric fluctuations are not
critical Delta photometry < 50%) contrary to the residual piston requirements
(OPD <lambda/8) which requires the development of an efficient cophasing system
to fully exploit the imaging capability of a hypertelecope.
