NASA Readies 1.8-Kg Ingenuity Drone for First Powered Flight on Mars

Veritasium

To overcome an atmosphere only 1% as dense as Earth's, the autonomous rotorcraft relies on 2,900-RPM carbon blades and diverts two-thirds of its battery power purely to survive freezing Martian nights.

AI-assisted summary of Mars Helicopter (before it went to Mars) — original source. Check the original for full context.

Source published: 2019-08-10

Key ideas

NASA's Jet Propulsion Laboratory designed the Ingenuity helicopter to achieve the first powered, controlled flight on another planet, operating in an atmospheric density roughly 1% of Earth's. (0:00)
To produce sufficient lift in ultra-thin air, Ingenuity's coaxial rotors spin at 2,300 to 2,900 RPM with tip speeds capped at Mach 0.7, supported by an ultra-lightweight vehicle mass under 1.8 kilograms. (1:36)
Surviving Martian nights of -80°C to -100°C requires roughly two-thirds of the drone's 35–40 Wh battery capacity solely for internal heating, leaving only one-third for a maximum 90-second flight. (8:55)
Due to a 20-minute round-trip communications latency, Ingenuity must navigate entirely autonomously using high-frequency sensor fusion and automated cyclic and collective pitch adjustments. (5:53)

Detailed notes

## Background This video was published on YouTube by Veritasium on August 10, 2019. The show notes explain that host Derek Muller visited NASA's Jet Propulsion Laboratory to inspect the Mars helicopter, Ingenuity, just before it was mounted onto the Mars 2020 rover to attempt the first powered flight on another planet.

## TL;DR Facing an atmosphere with only 1% of Earth's density, JPL engineers designed Ingenuity as an ultra-lightweight 1.8-kilogram drone with counter-rotating coaxial blades spinning up to 2,900 RPM. To survive, two-thirds of its modest battery capacity is dedicated simply to heating internal electronics against brutal Martian nighttime temperatures, utilizing trapped Martian carbon dioxide rather than heavy aerogel for insulation. Because the 20-minute communication lag with Earth makes manual steering impossible, the craft relies on high-frequency autonomous closed-loop sensor processing. Slated to deploy via a pyrotechnic Frangibolt release under the rover's belly, the technology demonstration aims to validate aerial flight dynamics and pave the way for larger planetary aerial scouts.

## Atmosphere & style The presentation carries an infectious sense of awe and nerdy reverence, underscored by the host's genuine disbelief at standing mere feet away from actual extraterrestrial flight hardware. The JPL engineers speak with quiet pride, blending dry technical mastery with humorous acknowledgments of their hyper-strict weight constraints and dreams of mutual rover-helicopter selfies. Visually and aurally, the pacing balances crisp cleanroom close-ups with the roaring whine of testing chambers, evoking both the fragile delicacy of the hardware and the immense mechanical ambition of taking flight on another world.

## Bulletin - [00:00](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=0s) NASA's Jet Propulsion Laboratory designed the Ingenuity helicopter to achieve the first powered, controlled flight on another planet, operating in an atmospheric density roughly 1% of Earth's. - [01:36](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=96s) To produce sufficient lift in ultra-thin air, Ingenuity's coaxial rotors spin at 2,300 to 2,900 RPM with tip speeds capped at Mach 0.7, supported by an ultra-lightweight vehicle mass under 1.8 kilograms. - [08:55](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=535s) Surviving Martian nights of -80°C to -100°C requires roughly two-thirds of the drone's 35–40 Wh battery capacity solely for internal heating, leaving only one-third for a maximum 90-second flight. - [05:53](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=353s) Due to a 20-minute round-trip communications latency, Ingenuity must navigate entirely autonomously using high-frequency sensor fusion and automated cyclic and collective pitch adjustments.

## Key takeaways - [00:00](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=0s) Ingenuity is engineered to achieve the first powered, controlled aerodynamic flight on another planet as part of the Mars 2020 mission. - [00:00](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=0s) Mars's surface atmospheric density is roughly 1% of Earth's, presenting an aerodynamic challenge equivalent to flying an aircraft at 100,000 feet on Earth. - [01:36](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=96s) Ingenuity's counter-rotating blades spin between 2,300 and 2,900 RPM—roughly five times faster than terrestrial helicopters—with tip speeds capped at Mach 0.7 to avoid shockwaves. - [01:36](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=96s) To meet strict weight constraints, the total craft weighs less than 1.8 kg, using carbon fiber and foam blades that weigh only 35 grams each. - [04:06](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=246s) Engineers tested flight performance on Earth by combining the low-pressure 25-Foot Space Simulator with an active fishing-line gravity offload system that simulated Mars's 38% gravity. - [05:53](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=353s) A 20-minute round-trip radio delay and sluggish aerodynamic response make real-time manual piloting impossible, requiring fully autonomous closed-loop flight control executing hundreds of times per second. - [08:55](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=535s) Testing with an array of 960 computer cooling fans demonstrated that the vehicle can maintain stability in crosswinds of up to 11 meters per second. - [08:55](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=535s) The 35–40 Wh battery requires a full sol to recharge via solar panels, providing enough energy for at most one 90-second flight outing per day. - [10:18](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=618s) Roughly 67% of onboard battery power is spent on internal heaters to survive nighttime temperatures of -80°C to -100°C, leaving roughly 33% for flight motors. - [10:18](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=618s) To save mass, the fuselage foregoes solid aerogel insulation and instead traps ambient Martian CO2 gas within internal structural gaps to insulate the electronics. - [11:45](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=705s) The aircraft is stowed sideways underneath the rover, built to endure >80 G vibrational launch loads and 9 G deceleration before release via an expanding Frangibolt. - [13:13](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=793s) The optimal flight window is around 11:00 AM local solar time, balancing morning solar battery recharging against late-afternoon drops in air density and thermal wind gusts. - [14:18](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=858s) Ingenuity is purely a technology demonstration intended to gather engineering flight data to pave the way for future planetary scout drones capable of accessing cliffs, craters, and polar ice caps.

## Detailed walkthrough ### [00:00](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=0s) Meeting the Mars Helicopter at JPL

At the NASA Jet Propulsion Laboratory in Pasadena, the host gets an up-close look at the actual flight hardware built for the Mars 2020 mission: the Mars helicopter, Ingenuity. As the team introduces the vehicle in the cleanroom environment, the host reacts with disbelief that the hardware standing directly in front of him is the exact craft destined to take off and land on Martian soil. One of the JPL engineers remarks with quiet pride, “This will be the first powered flight in another planet.”

While balloon flight occurred earlier—notably in 1985 when the Soviet Union's Vega missions successfully floated two helium balloons for over 46 hours across 54 kilometers of altitude in Venus's dense, 90-atmosphere environment—achieving powered aerodynamic lift on Mars poses the inverse problem. Mars has an extraordinarily tenuous atmosphere, measuring roughly 1% of the density found at Earth's surface. Flying in the Martian air is the aerodynamic equivalent of piloting a rotorcraft on Earth at 100,000 feet, far surpassing Earth's helicopter ceiling of roughly 40,000 feet and even exceeding the highest recorded airplane altitude of 85,000 feet.

- Surface atmospheric density on Mars is equivalent to Earth's air at roughly 100,000 feet. - A cubic meter of air at room temperature on Earth weighs roughly 1 kilogram; the same volume on Mars holds only 15 to 18 grams of gas. - The helicopter is scheduled to accompany the Mars 2020 rover mission.

---

[01:36](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=96s) The Aerodynamics of Thin Air: Blade Speeds and Weight Budgets

Because Mars offers so few air molecules per cubic meter, the rotors must push an enormous volume of air downward to generate enough upward force. The direct engineering answer is raw rotor speed. Ingenuity’s blades spin between 2,300 and 2,900 RPM—roughly five times faster than standard terrestrial helicopters, which spin at around 500 RPM. However, the engineers cannot simply crank the motors indefinitely. If the blade tips breach the speed of sound, shockwaves, transonic flow complications, and unstable aerodynamics quickly follow. Consequently, the team capped blade tip velocity at a conservative Mach 0.7 (70% the speed of sound).

Lower Martian surface gravity—roughly 38% of Earth's—helps offset the atmospheric deficit, but the weight budget was fiercely contested throughout the development program. As one of the lead engineers explains, “Keeping the mass of this vehicle contained during the entire design process has been the major challenge.” The entire vehicle was constrained to under 1.8 kilograms (less than four pounds), roughly the mass of a modern laptop. The individual rotor blades feature a foam core wrapped in a carbon fiber layup, weighing just 35 grams each—equivalent to the weight of six US quarter coins. Two 35-gram blades bear the burden of lifting the entire 1,800-gram chassis while spinning up to 40 times per second, all for a planned flight duration of up to 90 seconds.

```mermaid flowchart TD accTitle: Aerodynamic Challenges and Engineering Solutions for Mars Flight accDescr: Flowchart illustrating how Martian atmospheric constraints dictate rotor blade design, vehicle mass limits, and flight configuration.

subgraph AtmosphericConstraints["Martian Conditions"] A["Low Atmospheric Density (~1% of Earth)"] B["Lower Gravity (~38% of Earth)"] end

subgraph RotorDesign["Rotor Architecture"] C["High Rotor Speeds (2,300–2,900 RPM)"] D["Mach 0.7 Tip Limit (Avoid transonic shockwaves)"] E["Coaxial Counter-Rotating Blades (Stacked compact footprint)"] end

subgraph MassBudget["Strict Mass Budget"] F["Total Craft: <1.8 kg (Laptop weight)"] G["Blades: 35 g each (Foam core + carbon fiber)"] end

A --> C C --> D A --> E B --> F F --> G ```

Rather than a quadcopter arrangement, the team adopted a coaxial, counter-rotating twin-rotor architecture. A quadcopter's wide blade span would make the craft impossible to mount underneath the rover belly. Stacking the rotors vertically also delivers an aerodynamic advantage: the upper rotor pulls and concentrates the flow, feeding a denser, more compact air stream into the lower rotor, allowing the bottom blade to operate more efficiently than if the two rotors were placed side by side.

---

[04:06](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=246s) Simulating Mars on Earth: The 25-Foot Chamber and Gravity Offload

Testing a Mars rotorcraft inside normal Earth ambient conditions is impossible. If the helicopter spun up at standard sea-level pressure, the dense air would act “like trying to swim in a thick soup,” overloading the motors and creating extreme acoustic noise before the rotors could ever reach their Martian flight RPM. To solve the atmospheric side of the equation, the team moved testing into JPL’s 25-Foot Space Simulator, an immense vacuum chamber capable of pumping down to Martian atmospheric pressures.

Replicating Martian gravity posed an entirely separate hurdle. Earth's gravity would pin the 1.8-kilogram craft to the ground, so the engineers built a specialized gravity offload system designed to pull upward continuously, leaving the helicopter feeling only 38% of its terrestrial weight. The offload mechanism used a brushed DC motor, a reaction torque sensor, and a pulley system mounted several stories in the air, connected directly to the top of the craft via actual commercial fishing line. Because the system needed precise feedback without unwanted elasticity, the team tested numerous lines across different suppliers to dial in the ideal spring constant. When spinning inside the low-pressure chamber under offload, the high-speed rotors produced an unexpected, loud, droning sound akin to an aggressive buzz. As one engineer noted after running the system: “When gravity offload systems working and the chamber was pumped down, the helicopter thought it was on Mars. It felt like it was on Mars.”

---

[05:53](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=353s) Steering Mechanics and Autonomous Closed-Loop Control

Ingenuity steers using traditional rotorcraft pitch principles: collective and cyclic control. Collective control adjusts blade pitch uniformly across an entire 360-degree rotation to increase or decrease the overall angle of attack, regulating vertical lift and altitude. Cyclic control varies blade pitch cyclically at specific positions around the rotation arc. Modulating the pitch creates an asymmetric aerodynamic torque across the rotor disk. Factoring in the rotor head stiffness and gyroscopic lag, this torque causes the helicopter to pitch or roll. Once the craft tilts stably, a component of its total thrust vector points horizontally, causing the craft to translate laterally across the Martian terrain.

```mermaid flowchart LR accTitle: Autonomous Flight Control Architecture accDescr: A closed-loop control diagram showing how sensor inputs are processed onboard at high frequency to drive blade cyclic and collective actuators.

subgraph SensorSuite["Onboard Sensors"] S1["Downward-Facing Camera"] S2["Gyroscopes & Accelerometers"] S3["Altimeter & Inclinometer"] end

subgraph OnboardComputing["State Estimation & Algorithm"] SE["State Estimator (Hundreds of Hz)"] CL["Closed-Loop Control Algorithm"] end

subgraph BladeActuation["Aerodynamic Output"] BC["Cyclic Pitch (Roll/Pitch/Translation)"] BP["Collective Pitch (Altitude/Lift)"] end

S1 --> SE S2 --> SE S3 --> SE SE --> CL CL --> BC CL --> BP BC -.->|"Motion & Visual Feedback"| SensorSuite BP -.->|"Motion & Visual Feedback"| SensorSuite ```

Piloting the craft manually via a real-time joystick is an impossibility. Even disregarding communication latencies, test pilots attempting to hand-fly the craft found it unmanageable due to sluggish aerodynamic response times: “If you were sitting right there on Mars and you were trying to joystick it, what is it like? And it's almost unflyable.” Factoring in the 20-minute round-trip radio delay between Earth and Mars, mission controllers cannot provide live steering inputs. Flight commands must be uplinked beforehand as automated sequences.

Once commanded to take off, Ingenuity navigates entirely autonomously: - An onboard sensor suite blends inputs from gyroscopes, accelerometers, a downward-pointing navigation camera, an altimeter, and an inclinometer. - Real-time state estimation updates hundreds of times per second (hundreds of Hertz) against surface terrain. - The closed-loop control system takes state deviations and continuously computes corrective commands to the swashplate actuators. - Although finished test flight footage appears glassy and motionless during hovers, the internal control loops and swashplates are oscillating at high speeds beneath the surface to maintain equilibrium.

---

[08:55](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=535s) Wind Handling, Battery Capacity, and Surviving the Martian Freeze

When dealing with Martian weather, the atmospheric reality differs sharply from science fiction depictions of violent sandstorms. Because the air density is only 1% of Earth's, atmospheric dynamic pressure is extremely low, meaning incoming air carries very little physical force against the vehicle's body. To confirm how the drone would hold up in crosswinds, JPL engineers constructed a dedicated, open-cross-section wind tunnel inside the 25-foot space chamber, built out of an array of 960 computer cooling fans that roared like a miniature jet engine. The fan wall verified that the rotorcraft could handle winds up to 11 meters per second without tumbling.

Ingenuity’s power subsystem is tightly constrained: - Total battery capacity is modest, between 35 and 40 watt-hours—equivalent to roughly three standard smartphone batteries. - Recharging the custom lithium-ion cells via the mast-mounted solar panel takes an entire Martian day (sol). - In theoretical performance terms, the turnaround cycle supports at most one 90-second flight outing per day. - Only roughly one third of the craft’s stored battery capacity goes toward motor power for flight. - The remaining two thirds of stored energy must be diverted to internal heaters to protect delicate electronics and batteries through brutal Martian nights, when temperatures regularly plunge between -80°C and -100°C.

[10:18](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=618s) Thermal Architecture and CO₂ Insulation

Surviving the brutal nighttime temperatures on Mars dictates nearly the entire energy budget of the helicopter. The craft’s battery cells are kept grouped together in the center of the fuselage cube and surrounded by the electronics circuit boards so that the warmth radiates outward and keeps the boards operational. Maintaining survivable temperatures is so demanding that roughly two-thirds of the total stored electrical energy is devoted purely to keeping components warm and conditioning them for operation, leaving only a single third of the battery reserve available for powered flight.

```mermaid flowchart TD accTitle: Ingenuity Power Distribution and Structure accDescr: Diagram illustrating the energy allocation between heating and flight, and the concentric physical layout of the fuselage. subgraph PowerAllocation["Energy Budget"] direction TB P1["2/3 of Battery Energy: Thermal Conditioning & Survival"] P2["1/3 of Battery Energy: 90-Second Powered Flight"] end subgraph FuselageLayout["Fuselage Cross-Section"] direction TB F1["Core: Battery Ring"] F2["Mid-Layer: Electronics Boards"] F3["Insulation Gap: Martian CO2 Gas"] F4["Outer Layer: Fuselage Shell"] F1 --> F2 --> F3 --> F4 end ```

The physical stack of the vehicle features a solar panel and an antenna mounted at the very top, followed by the counter-rotating rotor system, and finally the cubic fuselage slung underneath. Because the helicopter was observed on its final day before being integrated onto the rover, its fuselage shell was briefly off. Inside, a deliberate air gap separates the central battery core from the circuit boards. Once the outer fuselage shell is sealed, it traps ambient Martian carbon dioxide gas inside. Rather than using specialized solid insulators, the vehicle relies directly on this captured CO₂ pocket to insulate the internal electronics from the external freeze. Aerogel was initially evaluated during early planning, but it was abandoned because meeting the mission's strict mass margins ruled out any unnecessary grams. As the engineer quipped when weight was identified as the reason for dropping aerogel:

> “Yep, there you go. Welcome to our team.”

- **Energy breakdown**: Approximately 67% of onboard power is consumed by heating systems; only ~33% is reserved for rotor flight. - **Structural stack**: Solar panel and antenna on top, dual rotor assembly in the middle, and the cubic electronics fuselage below. - **Thermal insulation**: Ambient Martian carbon dioxide ($CO_2$) gas fills the dead space inside the fuselage shell, closing the thermal model without the weight penalty of aerogel.

---

[11:45](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=705s) Launch Loads, Staging, and the Frangibolt Drop

Before confronting the Martian atmosphere, the helicopter must endure the mechanical violence of leaving Earth and entering deep space. The hardware is fundamentally an aircraft packaged as a spacecraft: it has to withstand severe rocket vibrational launch loads that easily exceed 80 Gs, survive seven months of interplanetary cruise exposure to deep-space radiation, and endure 9 Gs of deceleration during entry into the Martian atmosphere.

The craft makes the journey bolted sideways underneath the rover's belly pan. Once on Mars, deploying the helicopter to the surface requires a choreographed sequence of pyrotechnic actuations to swing the craft right-side up, lock its landing gear, and hang it just above the dirt. To release the craft without mechanical latching mechanisms that could jam, the rover utilizes a Frangibolt:

> “Basically it's materials you know undergoes a phase transition which suddenly increases the, the stress in the metal part of the thing and makes the bolt break.”

After the bolt fractures and drops the craft to the ground, the rover rolls forward approximately 100 meters to establish a safe operating perimeter. A two-hour internal countdown timer on the helicopter then elapses, waking the craft up to listen for RF radio signals from the base station antenna mounted on the rover before executing any further commands.

- **Extreme G-forces**: Designed to survive >80 G vibrational launch loads and 9 Gs during atmospheric entry. - **Stowage location**: Tucked sideways under the belly of the Mars 2020 rover. - **Pyrotechnic release**: A Frangibolt uses internal material phase changes to intentionally fracture the retaining bolt on command. - **Wake-up sequence**: A 2-hour autonomous internal timer ticks down on the ground before the helicopter switches on its radio receiver to listen for rover transmissions.

---

[13:13](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=793s) The 11:00 AM Flight Window and the Mutual Selfie

Once communications are established, the rover’s base station can transmit the final “fly now” command. The team established that the sweet spot for flight occurs around 11:00 AM local solar time on Mars. Taking off earlier in the morning is impossible because the heating systems have spent the long night draining the cells, leaving the battery charge too low to spin the rotors without risking a sudden brownout that would crash the aircraft. Mid-morning allows sunlight to hit the solar array, recharge the battery, and naturally warm the airframe, reducing internal heater power requirements.

Conversely, waiting until late afternoon presents distinct aerodynamic hazards: as daytime heating peaks, the already thin Martian air drops even further in density, while surface thermal winds pick up significantly. A mid-morning launch balances battery replenishment with atmospheric stability. As the team joked about the visual objectives of that historic maiden hop, capturing each other with their respective onboard cameras seemed almost mandatory:

> “First flight will probably be a mutual selfie, you would think.. This is after all the selfie age.”

While initial flights are planned conservatively for 11:00 AM, the engineering team intends to push into afternoon flight profiles and more demanding exploration runs once the initial operational envelope is proven.

- **Target flight time**: ~11:00 AM local Martian time. - **Brownout avoidance**: Mid-morning provides enough solar charging to bring battery state of charge above the threshold required for high-draw flight maneuvers. - **Aerodynamic balance**: Avoids the late-afternoon hazards of reduced atmospheric density and high surface wind gusts.

---

[14:18](https://www.youtube.com/watch?v=GhsZUZmJvaM&t=858s) Technological Demonstration and the Future of Planetary Flight

Ingenuity was constructed strictly as a technology demonstration. While equipped with color cameras capable of taking aerial photos and video, its mission does not revolve around gathering direct scientific samples or conducting mineralogy. The overarching objective is to gather real-world flight dynamics and engineering telemetry from another world to guide the development of future generations of extraterrestrial aircraft:

> “The real emphasis here is to try to get back all the engineering data so that it can inform that future design.”

Future iterations could expand into 30-kilogram rotorcraft carrying dedicated 2-kilogram sensor and instrument payloads. Such vehicles could serve as scouts pathfinding navigable terrain ahead of ground rovers, operate as high-speed couriers retrieving cache tubes to bring back to a central lander, or act as standalone explorers. Aerial mobility opens access to dramatic geographic features that are entirely inaccessible to wheeled platforms or human boots, such as vertical cliff faces, steep crater rims, and polar ice caps. By proving controlled aerodynamic lift on Mars, aerial vehicles promise to bridge the operational gap between wide-angle orbital surveillance and slow-moving surface rovers.

- **Primary objective**: Prove powered, controlled atmospheric flight on another planet and harvest engineering data. - **Future vehicle scale**: Conceptual designs envision ~30 kg platforms carrying ~2 kg dedicated science payloads. - **Potential applications**: - Long-range scouting for rover route planning. - Sample-return ferrying between field sites and central ascent landers. - Accessing extreme vertical and polar terrain (cliff faces, polar ice caps). - **Core advantage**: Fills the operational gap by traveling far faster than wheeled rovers while offering vastly higher resolution imagery than orbital spacecraft.

## Mentioned Ingenuity, NASA Jet Propulsion Laboratory, Mars 2020, Vega program, Frangibolt

## Video description The Mars Helicopter, Ingenuity aims to make the first powered flight on another planet when it takes off on Mars. It has now landed and safely checked in with the rover. It should detach and fly within the first 30-60 days of the mission. I learned a lot getting to visit the drone right before it was mounted on the rover at NASA Jet Propulsion Laboratory in Pasadena.

How do you fly in 1% of Earth's atmosphere: Have large rotors (they are 1.2m in diameter) and spin them very fast, around 2500 RPM (5x the speed of a helicopter on Earth).

Plus the aircraft has to be light: The Mars helicopter weighs in at 1.8kg or around the same as a laptop. Every piece had to be stripped down for weight. Instead of using aerogel for insulation, the craft makes use of CO2 gaps between components. Even aerogel was too heavy!

One of the major challenges is surviving the Martian night: Temperatures plunge to -80C to -100C so two thirds of the craft's power is actually used to keep its electronics warm. Only one third is used for flying. The estimated flight time is 90 seconds.

The craft can't be driven remotely, it will have to fly autonomously, using its own sensor suite to determine how to fly. The round trip 20 minute delay with Earth means steering the craft from mission control would be impossible.

Huge Thanks to Patreon Supporters: Philipp Volgger, Chris Vargas, Ron Neal, Alfred Wallace, Colin Bellmore, Michael Krugman, James Knight, Donal Botkin, Sam Lutfi, Mohammed Al Sahaf, Kevin Beavers, Chuck Lauer Vose, Bryan Baker, James Wong, kkm, Manuel Zürcher, Tige Thorman, Jasper Xin, Leah Howard, Daniel Milum, Mathias Göransson, Stan Presolski, Lyvann Ferrusca, Arjun Chakroborty, June Kang, Listen Money Matters, Pindex, Joar Wandborg, DALE HORNE, Parker Linn, Roberto Rezende

Jonny Hyman was a legend in editing, animation, filming, and sound design for this video.

[Source](https://www.youtube.com/watch?v=GhsZUZmJvaM)

中文简报

NASA准备让1.8公斤机智号无人机进行火星首次动力飞行为克服密度仅为地球1%的大气层，这架自主旋翼机依靠转速达2900 RPM的碳纤维叶片，并将其三分之二的电池电量纯粹用于度过严寒的火星之夜。面对密度仅为地球1%的大气层，喷气推进实验室（JPL）工程师将机智号设计为仅重1.8公斤的超轻型无人机，其反转共轴双桨转速最高可达2900 RPM。为了生存，其有限电池容量的三分之二仅用于加热内部电子设备以抵御残酷的火星夜间低温，且利用被封存的火星二氧化碳而非沉重的气凝胶进行绝热。由于与地球之间存在20分钟的通信延迟导致无法进行人工操控，该机依靠高频自主闭环传感器处理。该技术验证机计划通过火星车底部的火工Frangibolt装置释放部署，旨在验证空中飞行飞行动力学，并为更大规模的行星空中侦察器铺平道路。 NASA喷气推进实验室设计了机智号直升机，以在大气密度仅约为地球1%的环境下，实现人类在另一个星球上的首次受控动力飞行。 (0:00) 为了在极薄空气中产生足够升力，机智号的共轴旋翼转速为2300至2900 RPM，桨尖速度限制在0.7马赫以内，并依靠小于1.8公斤的超轻机身质量提供支持。 (1:36) 要在-80°C至-100°C的火星夜晚生存，需要将无人机35–40 Wh电池容量的大约三分之二仅用于内部加热，只留下三分之一用于最长90秒的飞行。 (8:55) 由于存在20分钟的双向通信延迟，机智号必须利用高频传感器融合以及全自动的周期变距和总距调节实现完全自主导航。 (5:53)

Original transcript

[0:00] I'm at the Jet Propulsion Laboratory in Pasadena, [0:04] and I'm here to see the first drone that's gonna fly on another planet. [0:08] It's the Mars helicopter. Come on! [0:11] - So this is our baby. [0:14] - No way! [0:15] - Yeah. [0:16] - That thing right there is the actual machine that is going to take off and land on Mars. [0:22] It's going with the Mars 2020 mission. That is the Mars helicopter. [0:26] - This will be the first powered flight in another planet. [0:30] - How awesome is that? [0:31] Now it's necessary to say first powered flight, [0:34] because in 1985, the Soviet Vega missions deployed two helium balloons on Venus. [0:39] They transmitted data for over forty six hours while floating at an altitude of 54 kilometers in Venus's dense atmosphere, [0:46] which at the surface has a pressure of over 90 Earth atmospheres. [0:51] In contrast, Mars has very little atmosphere, only around 1% of Earth's. [0:56] - Flying this kind of helicopter is equivalent to flying a similar helicopter on Earth at a hundred thousand feet. [1:05] So you don't know, you don't hear about many helicopters at a hundred thousand. [1:09] I think forty thousand feet is probably the record. [1:11] - I checked. Forty thousand feet is the record altitude reached by helicopters on Earth. [1:16] 85,000 feet is the highest a plane has ever flown. [1:19] On Mars, the air is even thinner than that. [1:23] - Right. In terms of density is 1% of what you have in this room. [1:26] So in this room, a cubic meter of air is about a kilogram. [1:30] - Yeah - The same cubic meter on Mars will be about 15 grams to 18 grams. [1:35] So that much [1:36] - So you have to push a lot of air down. [1:38] - Yes. You gotta get a lot of air flowing. [1:40] And so the obvious trick, if you will, is to spin the blades faster. [1:45] - It can spin between 2300 rpm and 2900 rpm. [1:49] - That is fast. [1:50] - That is fast. Yes. [1:51] - Here I'm trying to work out exactly how fast that is. [1:55] So I looked it up, and on Earth helicopters typically spin their rotors at around 500 rpm. [2:01] So the Mars helicopter will have to spin its blades five times faster. [2:05] - But there are some limits you know, you really don't want to get the tips of the blades breaking the speed of sound, [2:11] - cause then you have shockwaves and all sorts of [2:13] - and you get all kinds of funky aerodynamics and you know the transonic flows and things like that, so you don't want to go there. [2:18] So we, in our designs, keep the tip Mach numbers down to below about 0.7. [2:23] - So 70% the speed sound. [2:25] - Yeah. It was very conservative. [2:26] - One advantage of flying on Mars is that gravity is only 38% of what it is on Earth. [2:32] Even so, making the craft lightweight was essential. [2:35] - Keeping the mass of this vehicle contained during the entire design process has been the major challenge. [2:40] - Every single part had to be considered. [2:44] The entire vehicle is less than 1.8 kilograms [2:46] - Woah! [2:47] - So, less than four pounds [2:48] - That's about the same as this laptop. [2:51] - The blades are a foam core with carbon fiber layup. Each of them is about 35 grams. [2:57] - Wow. [2:58] - Yes, it's quite light. Yes. [3:01] - 35 grams is the mass of six quarters. [3:04] Think about that: two 35 gram blades lifting an 1800 gram helicopter by spinning 40 times per second in just 1% of Earth's atmosphere. [3:15] How long can it fly for? [3:18] - It's designed to fly up to 90 seconds. [3:20] - A minute and a half of flight. [3:22] - Yes. [3:22] - To me that sounds like forever, [3:24] when you're talking about another planet, flying autonomously by itself [3:28] in 1/100 earth atmosphere, I mean, come on! [3:30] Like, that's a long time! [3:32] - That is. Yeah. [3:33] - One of the questions I had was, why didn't they use a quadcopter design? [3:37] Well, because on Mars, the blades have to be so long that the whole craft would barely fit on the rover. [3:43] Two counter-rotating propellers provide the simplest design. [3:47] They also generate lift more efficiently when stacked on top of each other. [3:52] - The bottom rotor sees the sort of the more compactified flow. [3:58] The top one pulls it, the bottom one sees sort of a more concentrated flow. [4:02] So the bottom rotor actually can do better than if they were separated apart. [4:06] - But how do you test a helicopter designed for conditions on Mars on Earth? [4:10] What would happen if you just took your Mars helicopter and you tried to take off on Earth? [4:16] - It would just make a lot of noise. [4:17] - Really? [4:18] - And it probably wouldn't get the full head speed either... [4:20] - because of how much atmosphere we've got. [4:22] - Exactly, it's like trying to swim in a thick soup. [4:23] We have a really amazing chamber here on lab called the 25-foot space simulator. [4:28] And in that chamber you could simulate any kind of atmosphere you want. [4:31] You can go to Martian pressures, you can stay at Earth pressures, whatever you want. [4:34] But that only took care of half of the problem, that was the aerodynamics aspect of it. [4:38] There's the other part which is the gravity. [4:40] We needed a way to fake Mars' gravity here on Earth, [4:43] and the best way that we could figure out to do that was a gravity offload. [4:46] - Gravity offload just means pulling up on the helicopter, [4:50] so it only has to support about 38% of its weight just like it will have to do on Mars. [4:55] - And effectively it was a high-tech fishing reel, [4:57] so taking a brushed DC motor, a reaction torque sensor, and a pulley, [5:01] mounting that a couple stories in the air [5:03] and then attaching a fishing string to the top of the helicopter [5:06] that would tug the necessary force required to offload the differences in gravity. [5:10] - An actual fishing line? [5:12] - Yeah, real fishing line. [5:13] - But isn't that stretchy, [5:14] like don't you want something that's perfectly rigid so as soon as you apply the torque it gets applied to the craft? [5:18] - Right right, and we did a lot of testing with different vendors to find out which fishing line had the best spring constant for us. [5:24] - What does the helicopter sound like? [5:26] I imagined that in 1% of Earth's atmosphere, the helicopter would be pretty quiet. [5:32] - Yeah you're still at 1%, but it's still, real loud. [5:35] - Really? [5:35] - Yeah we have audio recordings of it too. [5:37] But it's it's, I would characterize it more like a 'baaaaaaaaah', something like that. [5:43] (baaaaaaah) [5:46] When gravity offload systems working and the chamber was pumped down, the helicopter thought it was on Mars. [5:51] It felt like it was on Mars. [5:53] - How do you actually steer this thing around and drive it? [5:57] - So the way helicopters work is they have something called collective and cyclic. [6:03] So what collectives do is they change the pitch on the blades uniformly. [6:06] So throughout the entire revolution you will move the collective, [6:09] the blades will change, you can change your angle of attack, you'll get more lift [6:13] so that's basically what you would provides you height control, [6:16] Right? You pitch more you go up, pitch less you come down. [6:20] But then, there's something called a cyclic on helicopters, [6:23] which basically what it does is it modulates the pitch as it goes around, [6:29] so it can pitch it a little bit more here, less here, so it kind of like modulates. [6:34] So what that does is it provides an asymmetric torque, right? [6:37] When you're pitched up there you get that additional torque. [6:40] Now you get it, depending upon the stiffness the system you actually get it with that a gyroscopic lag that can happen afterwards. [6:46] So once you get an asymmetric torque, the vehicle wants to start pitching or rolling. Right? [6:54] So once it pitches and rolls, [6:56] you're doing it stably. [6:58] You are now pointed in a direction and your thrust vector now has a component that's horizontal in the direction that you pitched. Right? [7:05] So then you start translating in that direction. [7:07] - I've heard that initially someone tried to fly it with a joystick? [7:12] - Yes. - Was it an early prototype? [7:13] - If you were sitting right there on Mars and you were trying to joystick it, what is it like? [7:16] And it's almost unflyable. [7:19] And the reason for that it's the aerodynamics of when you want to command a roll to the left [7:24] because you see yourself starting to move to the right and you start commanding a roll to the left. [7:28] There's a delay aspect. [7:30] So that that delay effect makes it very very difficult for a human to try and pilot it. [7:34] - You can't fly this from Earth... [7:37] - because of the twenty-minute kind of time delay, so you have to really send sequences. [7:42] - So essentially you're gonna push a button, [7:45] and like 20 minutes later it'll take off and do its thing and then you will find out. [7:49] - The way this flies autonomously, [7:51] it has onboard gyros, onboard accelerometers and onboard camera, an altimeter and an inclinometer; [8:00] and so using that sensor suite, [8:02] real-time measurement, you know against terrain and of course the gyros and the accelerometers sensing onboard [8:10] the real-time estimation of the state of the vehicle is made continuously again at hundreds of Hertz [8:19] and then that's fed into the closed-loop control algorithm, [8:23] that takes the estimated state [8:25] and then generates the correction that's needed at the blade level, [8:30] and then the blades are continuously being controlled. [8:33] So when you see video tapes of our "successful flights", right! [8:38] And the vehicle looks dead calm, it's coming up, and hovering, and going laterally, coming back; [8:45] you know the machines are working very very fast and very very hard it just looks very calm, but yes [8:51] so the the blades are being continuously controlled. [8:53] - That is amazing. [8:55] How will it handle a gentle breeze? [8:57] - A lot of the movies depict - Dust storms? [9:01] - The big dust storms as being very aggressive on Mars. [9:03] The truth of the matter is that with 1% Earth's atmosphere, there is very little matter actually hitting you. [9:10] - I mean, you're using that to lift yourself. [9:12] - Exactly, so there's enough to lift, right? [9:15] But we also need to spend at 2200 rpms to be in the ballpark of lifting ourselves. [9:18] - We built our own wind tunnel that we put inside this 25 foot chamber. [9:22] How many fans was it, Teddy? [9:23] 960 computer fans. [9:25] So, but it does sound like a like a jet engine taking off. [9:28] So we built a fan wall array, it's called an open cross-section wind tunnel, where you don't need the walls, [9:34] just the fact of having an array of fans we are very confident of being able to go at 11 meters per second, [9:39] in this vehicle. [9:41] if I had known that somewhere along the way I'd be building a wind tunnel to do this, [9:45] I would have probably not taken the job on, right? [9:48] - How long does it take to recharge? [9:49] We recharge the whole day. [9:51] So, the whole day at Mars. [9:53] - Right. But does that mean that you could do one flight a day kind of thing? In theory? [9:57] - In theory, yes, by design it can. [10:00] - What is the size of the battery? [10:02] - Between 35 and 40 watt hours total. [10:05] - That's equivalent to just three smartphone batteries. [10:09] And get this -- most of that energy isn't even used for flying. [10:13] - It has to survive temperatures as low as about minus 80 to minus hundred degrees C at night. [10:18] So we keep the batteries warm and we surround the batteries with our electronics board so the electronic boards also stay warm. [10:25] We take approximately two-thirds of energy just keeping things warm and warming things up to operate. [10:30] Only one-third of the energy is available for flight. [10:32] - Do you have insulation on there to keep it warm? [10:35] - Yes. When you look at that helicopter, right, you have the solar panel on top with antenna, [10:40] and then next is the rotor system, [10:42] and then bottom what you see this cube, is what we call the fuselage, [10:46] you are seeing it now actually uncovered [10:48] because you're seeing the last day of final. We're recovering for delivery to be integrated onto the rover. [10:54] okay so usually you won't be seeing that. [10:56] So the center of the cube is the ring of batteries, okay. [11:00] There is space between the battery and the circuit boards that you are seeing. [11:04] And then there will be a shell that we put on called the fuselage shell, [11:09] and that will close like CO2, the gas, around. [11:14] And so the enclosure itself we're using the CO2 gas as the insulation material [11:20] - Oh wow! No aerogel? [11:22] - No aerogel. We did it consider it. It was in the game, [11:25] it was in the consideration in the beginning, [11:28] and it turns out that just the CO2 as insulator itself was sufficient for us to close our thermal model. [11:37] - Right. [11:38] - And so guess why we wouldn't want to use aerogel if we have a choice. [11:42] - Weight. [11:43] - Yep, there you go. Welcome to our team [11:45] - Now before the helicopter can experience the frigid conditions on Mars, [11:49] first it has to get there. [11:51] And that's a reminder that not only is this an aircraft, it's also a spacecraft. [11:55] - It has to survive launch. [11:57] It has to survive launch loads which, you know, easily exceed about 80G [12:02] You know, because of the vibration. Vibrational loads are 80G. [12:05] - Yeah. Then it has to survive the seven-month trip, complete with radiation. [12:10] And finally after pulling nine Gs on entry into the Martian atmosphere the helicopter needs to be deployed. [12:17] This is gonna be on the rover, before you take off, does the rover like pick you up and put you down somewhere? [12:22] - We're gonna be stowed underneath the rover on the belly pan on our side. [12:26] And there's gonna be several several sequences of firings of explosive devices [12:32] to actually rotate us right side up and then drop us on the surface. [12:35] - For example the very last thing the rover does is it's got us by this bolt, it's holding us about this high, [12:40] and then it goes has to drop us, right? [12:42] - Yeah. [12:43] - So how do you undo a bolt on, on a spacecraft? [12:46] - You blow it up. [12:46] - You blow it up. Basically it's materials you know undergoes a phase transition [12:51] which suddenly increases the, the stress in the metal part of the thing [12:55] and makes the bolt break. It's called a frangibolt. [12:58] - Then once we're on the surface, the rover drives over us, [13:01] it gets about 100 meters away, [13:03] and then we have about a two-hour counter internally, [13:07] where we'll wake up after 2 hours, wait to hear some RF transmissions, [13:11] and if we do get that link with the rover then great. [13:13] - Our base station on the rover would issue the fly now command. [13:17] First flight will probably be a mutual selfie, you would think.. [13:21] This is after all the selfie age. [13:24] - I like that as the goal of the first flight. [13:26] - Yes it is. In fact, it is good to know the best time to fly this [13:29] is at 11 o'clock in the morning local time on Mars. [13:32] and that the reason for that is, we would have come out of the night, [13:35] where we would have spent a lot of battery power trying to you know stay warm. [13:40] By 11 o'clock, the state of the charge would have gotten to the point where you could fly [13:44] without risking a brownout on the battery and then, you know, dropping the whole craft to the ground. [13:49] Also 11 o'clock is where the Sun would have warmed up things, [13:53] so we don't quite have to heat up as much. [13:56] And also it's not late afternoon where because of the warmth, the density has begun to drop, [14:02] okay, and the winds have begun to pick up. [14:04] Now, what we will investigate is after we get the first couple of flights under our belt, [14:09] I'm sure we will try to fly in the afternoon and you know do more exploratory things. [14:13] But the most conservative thing we can do [14:16] is to sort of pick a mid-morning flight. [14:18] - So what is the purpose of this mission? [14:21] The Mars helicopter is first and foremost a technology demonstration [14:25] to prove that we can fly on another planet. [14:29] The helicopter can take color photos and videos, but its purpose is not to make scientific discoveries. [14:35] Instead it is to help engineers figure out how to design and build aircraft for future missions. [14:41] - You can imagine something that's about 30 kilograms carrying you know a 2 kilogram science payload, doing exploration, [14:47] acting like a scout, like a small vehicle, like this, scouting ahead for some future rover; [14:53] or it could be a gadget that goes and picks up some kind of samples and brings it back to a central lander for more sophisticated analysis; [15:01] or it could be a completely standalone craft, and maybe more than one [15:05] that are exploring places where humans and rovers can't get to easily: [15:11] polar ice caps, you know [15:13] sides of cliffs and so forth. [15:15] So the real emphasis here is to try to get back all the engineering data so that it can inform that future design. [15:21] - Flying on other planets will provide a new dimension in space exploration. [15:25] An aircraft is faster and capable of covering more ground than a rover [15:30] and it can provide higher resolution imagery than an orbiting spacecraft. [15:35] So maybe one day, aircrafts will be the companions of future rovers or even astronauts exploring other worlds.