I had no idea either so I asked, apparently it's about 0.85 Mach: https://www.wolframalpha.com/input/?i=speed+of+sound+at+100+km https://www.wolframalpha.com/i

I had no idea either so I asked, apparently it's about 0.85 Mach: https://www.wolframalpha.com/input/?i=speed+of+sound+at+100+km https://www.wolframalpha.com/input/?i=speed+of+sound+at+100+...