Engineers at NASA’s Jet Propulsion Lab make a breakthrough in rotor technology

NASA喷气推进实验室的工程师在旋翼技术上取得突破

A little more than three years since NASA’s Ingenuity helicopter ended its pioneering mission at Mars, engineers at the Jet Propulsion Laboratory in California are designing next-generation Martian rotorcraft to carry heavier payloads longer distances through the planet’s low-density atmosphere. 在NASA“机智号”（Ingenuity）直升机结束其火星开创性任务三年多后，位于加州的喷气推进实验室（JPL）的工程师们正在设计下一代火星旋翼机，旨在通过火星的低密度大气层运载更重的载荷，飞行更远的距离。

Ingenuity was a resounding success, becoming the first airborne platform to explore another world. The dual-bladed helicopter made 72 flights, overachieving NASA’s original goal of five flights over 30 days, after delivery to Mars by the Perseverance rover. “机智号”取得了巨大成功，成为第一个探索另一个世界的机载平台。这架双叶片直升机在由“毅力号”火星车送抵火星后，完成了72次飞行，远超NASA最初设定的在30天内飞行5次的目标。

By the time the mission ended with a crash-landing in January 2024, Ingenuity had shown scientists a new way to explore other worlds, using air to travel longer distances and reach locations inaccessible to ground vehicles. 当该任务于2024年1月以坠落着陆告终时，“机智号”已经向科学家展示了一种探索其他世界的新方法：利用空气进行长距离飞行，并到达地面车辆无法抵达的地点。

NASA plans to send three more helicopters to Mars on the SkyFall mission, which could launch as soon as late 2028. SkyFall is set to ride to the red planet aboard a nuclear-powered spacecraft named Space Reactor-1, or SR-1, one of the tech demo initiatives announced earlier this year by NASA Administrator Jared Isaacman. NASA计划在“天坠”（SkyFall）任务中再向火星派遣三架直升机，该任务最早可能于2028年底发射。“天坠”任务计划搭乘名为“空间反应堆-1”（SR-1）的核动力航天器前往火星，这是NASA局长贾里德·艾萨克曼（Jared Isaacman）今年早些时候宣布的技术演示项目之一。

Ingenuity‘s main body was not much larger than a tissue box, with a mass of just 4 pounds (1.8 kilograms) and counter-rotating rotors that spanned about 4 feet (1.2 meters). The SkyFall helicopters will be larger and heavier, and they will use a novel maneuver to land themselves on the Martian surface after entering the atmosphere cocooned inside a heat shield. This will require innovations in the helicopter’s design. “机智号”的主体大小与纸巾盒相差无几，质量仅为4磅（1.8公斤），其反向旋转的旋翼跨度约为4英尺（1.2米）。“天坠”直升机将更大、更重，它们在被隔热罩包裹进入大气层后，将采用一种新颖的机动方式在火星表面着陆。这将需要直升机设计上的创新。

Breaking a barrier

突破壁垒

Engineers at JPL and a private company named AeroVironment, the same partners that developed Ingenuity, recently made a breakthrough in the lab to nudge the SkyFall mission closer to reality. The tests involved the new, larger rotor blades that will convey the next-gen helicopters through the rarefied Martian atmosphere, just 1 percent the density of air at sea level on Earth. JPL的工程师与曾共同开发“机智号”的私营公司AeroVironment的合作伙伴们，最近在实验室取得了一项突破，使“天坠”任务向现实迈进了一步。这些测试涉及新型、更大的旋翼叶片，它们将驱动下一代直升机穿过稀薄的火星大气层——其密度仅为地球海平面空气密度的1%。

Because of this thin atmosphere, helicopters flying on Mars must spin their rotors faster than on Earth to generate lift, and heavier vehicles need more lift than lighter ones. The rotors on the SkyFall helicopters will also be larger than those on Ingenuity, which spun its blades at 2,700 rpm, already 10 times faster than passenger helicopters on Earth. 由于大气稀薄，在火星上飞行的直升机必须比在地球上更快地旋转旋翼以产生升力，且较重的飞行器比轻型飞行器需要更大的升力。“天坠”直升机的旋翼也将比“机智号”更大，后者的叶片转速为每分钟2700转，这已经是地球上客用直升机转速的10倍。

But engineers were careful to design Ingenuity not to spin its carbon-fiber rotors faster than the speed of sound out of concern that exceeding Mach 1 (roughly 540 mph on Mars) might cause the blades to shatter. 但工程师们在设计“机智号”时非常谨慎，使其碳纤维旋翼的转速不超过音速，因为担心超过1马赫（在火星上约为每小时540英里）可能会导致叶片破碎。

“If Chuck Yeager were here, he’d tell you things can get squirrely around Mach 1,” said Jaakko Karras, the rotor test lead at JPL, in a NASA press release. “With that in mind, we planned Ingenuity’s flights to keep the rotor blade tips at Mach 0.7 with no wind so that if we encountered a Martian headwind while in flight, the rotor tips wouldn’t go supersonic. But we want more performance from our next-gen Mars aircraft. We needed to know that our rotors could go faster safely.” “如果查克·耶格尔（Chuck Yeager）在这里，他会告诉你，在1马赫左右时情况会变得难以控制，”JPL旋翼测试负责人贾科·卡拉斯（Jaakko Karras）在NASA的新闻稿中表示。“考虑到这一点，我们规划‘机智号’飞行时，将无风状态下的旋翼叶尖速度保持在0.7马赫，这样即使在飞行中遇到火星逆风，叶尖也不会进入超音速。但我们希望下一代火星飞行器能有更好的性能。我们需要知道我们的旋翼能否安全地以更高速度运行。”

Recent testing at JPL pushed rotors past the speed of sound without damaging them, NASA announced Thursday. The rotor tips reached a top speed of Mach 1.08 in a test chamber simulating Mars’ atmosphere. NASA周四宣布，JPL最近的测试将旋翼推向了超音速，且未造成损坏。在模拟火星大气的测试舱中，旋翼叶尖达到了1.08马赫的最高速度。

Engineers didn’t know for sure what would happen to the rotors, so they lined part of the chamber with sheet metal to shield it from damage if the blades broke apart during the supersonic experiment, according to NASA. 据NASA称，工程师们并不确定旋翼会发生什么，因此他们在测试舱的部分区域衬上了金属板，以防叶片在超音速实验中破碎时造成损坏。

“From a control room a few yards away from the chamber, the team watched displays showing data and a view inside the chamber as the rpm climbed as high as 3,750,” NASA said. “At that rate, the tips were traveling at Mach 0.98. Then the engineers activated a fan inside the chamber that pelted the rotors with headwinds. After each run, they increased in wind velocity for the next run.” “在距离测试舱几码远的控制室里，团队观察着显示数据和舱内景象的屏幕，转速最高攀升至3750转/分，”NASA表示。“在该转速下，叶尖速度达到了0.98马赫。随后，工程师启动了舱内的风扇，向旋翼吹送逆风。在每次运行后，他们都会增加下一次运行的风速。”

The first series of tests used a three-bladed rotor design that could be flown on missions after SkyFall. A second test campaign used the actual two-bladed design that will fly on SkyFall. These blades are slightly longer, so they reached the same supersonic speed at a lower rpm. The faster spin resulted in a 30 percent boost in lift capability. 第一系列测试使用了三叶片旋翼设计，该设计可能用于“天坠”之后的任务。第二轮测试活动使用了“天坠”任务实际将采用的双叶片设计。这些叶片稍长，因此在较低转速下即可达到相同的超音速。更快的旋转带来了30%的升力提升。

The team pushed rotor tip speeds to Mach 1.08, boosting the Mars vehicle’s lift capability by 30 percent. This breakthrough allows future missions to support heavier scientific payloads, including advanced sensors and larger batteries for extended flight. 团队将旋翼叶尖速度推至1.08马赫，使火星飞行器的升力能力提升了30%。这一突破使未来的任务能够支持更重的科学载荷，包括先进的传感器和用于延长飞行时间的更大电池。

“We thought we’d be lucky to hit Mach 1.05, and we reached Mach 1.08 on our last runs. We’re still digging into the data, and there may be even more thrust on the table. These next-gen helicopters are going to be amazing,” said Shannah Withrow-Maser, an aerodynamicist from NASA’s Ames Research Center. “我们原以为能达到1.05马赫就很幸运了，但在最后几次运行中我们达到了1.08马赫。我们仍在深入分析数据，可能还有更大的推力潜力。这些下一代直升机将会非常惊人，”NASA艾姆斯研究中心的空气动力学家莎娜·威瑟罗-梅瑟（Shannah Withrow-Maser）表示。

At the same time that engineers are preparing to send more helicopters to Mars, NASA is working on a more massive rotorcraft named Dragonfly destined for Saturn’s moon Titan. Dragonfly will weigh nearly a ton, but flying on more distant Titan poses fewer challenges than on Mars because its atmosphere is thicker than Earth’s. 在工程师们准备向火星派遣更多直升机的同时，NASA正在研发一种名为“蜻蜓号”（Dragonfly）的更大型旋翼机，目标是土星的卫星土卫六（泰坦）。“蜻蜓号”重量将近一吨，但在更遥远的土卫六上飞行所面临的挑战比火星要小，因为那里的大气比地球更稠密。

The only payloads on the Ingenuity helicopter were two cameras: a black-and-white imager for navigation and a higher-resolution color camera. Its longest flight in 2022 covered less than a half-mile and lasted 161 seconds. The aircraft had to land and recharge its batteries using solar arrays, and it used the nearby Perseverance rover as a base station to communicate with ground. “机智号”直升机上唯一的载荷是两台摄像机：一台用于导航的黑白成像仪和一台更高分辨率的彩色摄像机。它在2022年的最长飞行距离不到半英里，持续时间为161秒。该飞行器必须着陆并利用太阳能电池阵列为电池充电，并使用附近的“毅力号”火星车作为基站与地面通信。