Venus Aerospace has made the most efficient rocket engines ever flown. They will go from runway to mach 9 hypersonic speed. The Venus Aerospace Stargazer M4 is designed to reach a top speed of Mach 9, which is approximately 6,900 mph. While its cruise speed is planned to be around Mach 4-5, the engine combination ...

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Link :
https://www.nextbigfuture.com/2025/10/most-efficient-rocket-engine-ever-flown-will-enable-affordable-mach-9-hypersonic-speed.html