Abstract: The invention relates to an aerostat of the double balloon type intended to travel in an autonomous and reversible manner between the ground of a planet having an atmosphere and a predetermined ceiling altitude. This aerostat is of the type comprising a first closed carrier balloon (1) for containing a gas lighter than the gas present in the atmosphere, and a solar hot air balloon (3) comprising a permanent opening (6) permitting its filling by the gas present in the atmosphere. According to the invention the solar hot air balloon is provided at its upper extremity with an opening defined by an annular border, and means for sealingly securing this annular border to the peripheral wall of the carrier balloon (1), such that said carrier balloon extends partially into the interior of the envelope of the hot air balloon (3).

Abstract: A paint for use on surfaces subject to lightning strikes includes a film-forming binder and a pigment, the pigment comprising at least one alkali metal salt or alkaline earth metal salt with a low first ionization potential, of a mono- or polyfunctional organic acid, carbonic acid or a polymer having an acidic group, the pigment being present in an amount sufficient to render the paint ionizable under the action of a strong electric current.