Off topic and I can’t provide a link to verify but I heard once that it is essentially impossible for a submarine vehicle to achieve mach 1
“... I heard once that it is essentially impossible for a submarine vehicle to achieve mach 1”
The speed of sound in a fluid (water and air are both fluids) is never constant but varies with temperature changes and other factors, including fluid density. US Navy won’t release vessel performance capabilities and limitations, but m_r probably heard right.
The speed of sound in water is much faster (some 4500 ft/sec) than in air (typical value on a typical day is 1040 ft/sec).
There is almost no practical value to traveling quicker than Mach 1.0 in aerial flight, compared to the power required and the structural strength needed. Only military aircraft were built to do it for many decades, and even then they could spend only a few minutes at such speeds, before exhausting their fuel. And almost none of them were able to “break Mach” (as military aviation jargon puts it) in level flight at low altitudes where the air is warmer and more dense; they had to climb many miles to do it.