NASA's headline for the story is cause for pause. On the JPL's Mars exploration web page, they say, "NASA Uses Two Worlds to Test Future Mars Helicopter Designs." Just a bit on the provocative side.
Provocative but burying the lede a little. I don't need to point out that the Ingenuity helicopter has been a rousing success; originally intended to test some concepts and make five test flights, the helicopter has flown 66 times and is ready for more. That has led to extending the concepts to other missions and Next Generation helicopters, which leads to redesigning parts and systems of a deep space helicopter. That, in turn, requires testing new design approaches and the one they talk about the most in this JPL post is enlarging the helicopters' rotors.
For the first time in history, two planets have been home to testing future aircraft designs. On this world, a new rotor that could be used with next-generation Mars helicopters was recently tested at NASA’s Jet Propulsion Laboratory in Southern California, spinning at near-supersonic speeds (0.95 Mach). Meanwhile, the agency’s Ingenuity Mars Helicopter has achieved new altitude and airspeed records on the Red Planet in the name of experimental flight testing.
"Our next-generation Mars helicopter testing has literally had the best of both worlds," said Teddy Tzanetos, Ingenuity’s project manager and manager for the Mars Sample Recovery Helicopters. "Here on Earth, you have all the instrumentation and hands-on immediacy you could hope for while testing new aircraft components. On Mars, you have the real off-world conditions you could never truly re-create here on Earth." That includes a whisper-thin atmosphere and significantly less gravity than on Earth.
I'll embed the short (1:12) video they have on their web site, but it's probably best just to look at it with the video stopped. Unsurprisingly, when the rotors are spinning, the blades aren't visible, so you'll get the clearest view of the twin rotors with the video stopped at either the beginning or the end, right around the 1:00 minute mark.
Testing Next-Generation Mars Helicopter Rotors: A dual rotor system for the next generation of Mars helicopters is tested in the 25-Foot Space Simulator at NASA's Jet Propulsion Laboratory on Sept.15. Longer and stronger than those used on the Ingenuity Mars Helicopter, the carbon-fiber blades reached near-supersonic speeds during testing. Credits: NASA/JPL-Caltech.
The blades being tested in the video are 1.3 meters in diameter, nearly 51 inches. That's just about four inches larger than Ingenuity's rotors with greater strength and a different design. NASA thinks these blades could enable bigger, more capable Mars helicopters. The challenge is that as the blade tips approach supersonic speeds, vibration-causing turbulence can quickly get out of hand.
"We spun our blades up to 3,500 rpm, which is 750 revolutions per minute faster than the Ingenuity blades have gone," said Tyler Del Sesto, Sample Recovery Helicopter deputy test conductor at JPL. "These more efficient blades are now more than a hypothetical exercise. They are ready to fly."
At around the same time, and about 100 million miles (161 million kilometers) away, Ingenuity was being commanded to try things the Mars Helicopter team never imagined they would get to do.
During the past nine months, JPL controllers have doubled Ingenuity's max airspeed and altitude, increased their rate of vertical and horizontal acceleration, and even learned to land slower. The helicopter was designed to touch down on the surface at a relatively quick 2.2 mph. That was so its onboard sensors could easily confirm touchdown and shut down the rotors before it could bounce back up. A helicopter that lands more slowly could be designed with lighter landing gear. So three flights (57-59) tested landing at 25% slower speeds with no difficulties.
The chamber the rotors have been tested in is about as famous as a thermal/vacuum test chamber can be, having tested such probes as the Surveyor lunar landers in the 1960s, Voyager and Cassini. While it can approach the vacuum of deep space, it can't reduce gravity to test things like the landings. That's where it's valuable to be able to test some things with Ingenuity out on the "the Fourth Rock from the sun."