4. Conclusion

The ramjet is the most efficient engine for supersonic flight in the atmosphere, but it must be accelerated to a minimum speed (around Mach 2 for current applications).

Combustion is subsonic in a ramjet flying up to around Mach 6; beyond that, it has to operate with supersonic combustion (demonstrated up to Mach 10 with hydrogen, we could probably go up to Mach 12, or even higher).

While the principle of this engine is simple, its technological mastery is the prerogative of a few nations, and a few organizations (in France, MBDA and ONERA with their partners). Design methodology, physical and chemical phenomena and various technical solutions are summarized in this article. Vehicle integration is important, and becomes increasingly crucial as speed increases.

While current operational applications include medium-...