(Image credit: NASA/JPL-Caltech) NASA confirmed in a blog post that it had successfully tested two Mars-bound rotor systems, achieving never-before-seen rotational speeds. In the tests, which took place under simulated Mars conditions at the historic 25-Foot Space Simulator at NASA’s Jet Propulsion Laboratory (JPL), the rotor systems — one two-bladed and one three-bladed — reached rotor tip speeds of up to Mach 0.98 before additional headwinds pushed the blades to Mach 1.08, surpassing the Martian speed of sound for the first time. The rotors reached up to 3,750 rpm. For comparison, that is roughly 10 times faster than the rotor speeds of many modern helicopters. These extreme speeds are necessary to generate enough lift in Mars’ ultra-thin atmosphere, which is only about 1% as dense as Earth’s. The planet's atmosphere also lowers the speed of sound to roughly 537 mph (864 km/h), compared to about 767 mph (1,235 km/h) at Earth’s sea level.…