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Hi Philippe Ricco,I have some original plans from Arsenal and Nord-Aviation of projects for Mach 3 and Mach 4. All are planned to use turbo-ramjet engines, based on experience acquired with the Griffon, such as the ones attached. I have provided some of these plans to Jean-Christophe Carbonel to include in his book about French Secret Projects.
The article in Latest issue of le Fana magazine shows some of these projects as part of its overview.