Faster than a speeding bullet

The hypersonic test flight of the X-43A, NASA’s scramjet test plane, had special significance for our family. My dad was working on the program that produced the engine while he was in research at NASA. His part was subtle but important: how do you figure out if your engine is running hot (or cold, or just how it’s running at all), when normal operating temperature is so hot that most probes would melt?

Cool stuff…

Incidentally, the title of this post is correct. Mach 7 = 7,815 feet per second. According to this article, the fastest projectile (not propelled by railgun) tops out at about 6,000 fps.