Mars Helicopter successfully completed its second flight | Hacker News Reader

Mars Helicopter successfully completed its second flight

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375 pointsSami_Lehtinen143 comments

If you're curious, a press release from yesterday had more details:

"This time around, we plan to trying climbing to 16 feet (5 meters) in this flight test. Then, after the helicopter hovers briefly, it will go into a slight tilt and move sideways for 7 feet (2 meters). Then Ingenuity will come to a stop, hover in place, and make turns to point its color camera in different directions before heading back to the center of the airfield to land."

via https://mars.nasa.gov/technology/helicopter/status/294/were-...

Kind of funny that a particular patch of the martian expanse has now been dedicated as an 'airfield'.

It even has an ICAO airport code, JZRO.

"The letters I and X are not currently used as the first letter of any ICAO identifier, and the letter J is only used in a ceremonial ICAO identifier granted to Jezero Crater on the planet Mars, JZRO."

Did they just set a precedent for J as the Mars prefix?

Yep. Nothing more permanent then temporary and all that - when Mars needs another airfield area, someone's going to Google for guidance, see that J and go "well, let's be consistent..."

Hope they add it to Microsoft Flight Simulator 2020

we now have airfields on different planets!

In all the downward-facing images from Ingenuity, I find it surprising that the rotor blades have a lighter shadow than the rest of the helicopter. I asked about this on Twitter and was told the sensor for each pixel isn't fully shielded from light. The fast-moving rotor blades allow for latent light to enter into the sensor during the image scan, causing the rotor blade itself to appear slightly lighter. [1]

[1]: https://twitter.com/sdamico/status/1384205372668350465

> it’s identical to the Google Project Tango SLAM camera module

That's fascinating, I would've guessed it had a special radiation-hardened camera like the processor.

It’s using an off the shelf Snspdragon CPU. The whole helicopter is made with COTS parts.

This paper discusses the design of the helicopter.

https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

Thanks! Fascinating hints at the complexities of working around radiation hazards:

>MCU processor units operate redundantly, receiving and processing identical sensor data to perform the flight-control functions necessary to keep the vehicle flying in the air. At any given time, one of the MCU is active with the other waiting to be hot-swapped in case of a fault.

>Each subsystem has a current monitor to detect possible latch-up current and can be power cycled to clear a SEL. In addition, current limiting is added to prevent a destructive SEL event and most devices are switched off when not in use to minimize their exposure to SEL. For the critical FPGA which is always on for the duration of the mission, the radiation tolerant ProASIC3 is chosen with the military temperature grade (-55 C to 125 C) and -1 speed grade to mitigate the degradation in the propagation delay caused by the total dose radiation.

I'm always amazed by the crazy crap people deal with in space, and how much protection the Earth affords us. Extreme temperatures, radiation, small bits of material traveling fast enough to go through structural metals like a knife; it's a thrill a second.

This is an important and highly under-appreciated point. We humans evolved under some very particular environmental conditions, ones which are radically different from space in almost every conceivable way.

When people talk about colonizing Mars, I ask them to do the following thought experiment: imagine you are going to move to the Atacama desert. You have to live there for the rest of your life. You get to take one standard twenty-foot shipping container with you. You can pack that container however you like, but you have to live inside the container along with whatever stuff you pack it with for nine months before you can go out for the first time.

Figuring out how to make that work is about 100 times easier than colonizing Mars.

Heres what I'm thinking. Since we have money, we test test test to make sure things work. Then each developed nation usa, Russia, china, India, Japan, UAE, Canada, ESA etc with a space program launches 1 a day for a total of 30 days. That would allow 30 shipping containers to arrive within days of each other. The first few are redundant life support/escape/return, the next few allow you to start building, the last few allow you to grow. In the meantime we are building and launching as fast as we can. you have to think ahead by 9 months and have everything planned out as best as you can with redundancy. So scaling, teamwork, redundancy and thinking ahead. Also money, lots of money.

Good sequence for a movie, but most likely we will pack a bunch of starships fill of supplies and land them, leaving two available for emergency return, the other N will shuttle more supplies to Mars. We can test the landing and relaunch as many times as necessary using automated systems. By the time humans land they can checkin at the front desk.

I think a base on one of the Mars moons would be nice. You can build a radiation shield and have a nice place to store your stuff. Maybe some fuel could be extracted from the regolith.

Well, that solution is also perfectly applicable if we were to colonize a desert, or Antarctica, or the ocean floor. Still, all of those are easier than colonizing Mars even if we throw unprecedented amounts of resources at the problem.

I think that's a poor example.

First off, doing such a moving experiment with only your own funds is a lot harder than if you had billions to millions of dollars to do it.

Secondly, people won't be trapped inside on Mars and will make regular, if not daily trips outside on EVAs (we may need a new acronym as there's no "Vehicle" here.)

Thirdly, a lot of hardware will be outside the "container" including the power generation from nuclear power or solar energy. (Likely nuclear powered sterling engines that have already been demonstrated in subscale versions.) (This contributes to the difference in funds point on my first point.)

Fourth, even though you didn't mention it, I'll add it here to preempt a counter argument. The radiation risks are overstated. Radiation on Mars is at least half that of being in space because you have radiation from one half of the "sky" blocked by the planet itself. Also while the radiation levels are certainly elevated, they're likely not going to kill you. Any long term colonies are going to be mostly underground anyway. (Or more likely simply buried by shoveling dirt on top.)

> doing such a moving experiment with only your own funds

I didn't say that you had to do it with your own funds. But how exactly do you think that extra money would help? Getting to the Altacama desert is not difficult or expensive. That's the reason that the fact that no one has bothered to even attempt it is so damning.

> people won't be trapped inside on Mars

I didn't say they would be. In fact, I specifically said that you would only have to spend nine months (the travel time to Mars) inside the container. After that you can go out as much as you like. You don't even have to wear a space suit.

> a lot of hardware will be outside the "container" including the power generation from nuclear power or solar energy

That's why I gave you a full 20-foot container. But fine, take three containers, which is about what will fit in a Falcon Heavy. Or six. It doesn't really matter. The point is, take some number of containers that you think is a plausible payload for a Mars colony -- and nothing else.

> The radiation risks are overstated

I never claimed otherwise. There are a zillion other things that will get you before the radiation does.

> Radiation on Mars is at least half that of being in space because you have radiation from one half of the "sky" blocked by the planet itself

You have to get there, which exposes you to a lot of radiation. And then you have to live there which exposes you to a lot more, no matter if it is "half" that you would get if Mars was a one-faced world WRT the sun.

Also, how are you going to get these diggers, their fuel, their support systems, etc, etc, to Mars that will excavate holes (lovely to live in) or cover things (ditto)? Why would anyone want to live like that, or worse, condemn their children to do so?

I used (in the 1960/70s) to believe in the colonisation of space. But now not at all - it is simply too difficult. And that's the answer to the Fermi Paradox.

If you at least sleep underground (1-2m), it keeps the total lifetime radiation dose manageable.

For most of the machinery, you would bring the tricky to manufacture bits (tight tolerance mechanical, electronics, non-basic chemicals) with you, and build the bulk structural parts on site. Even for something like a 10,000kg machine tool, only about ~500-2000kgs of materials need to be sent (see granite+epoxy CNC machines[0]). Other machines, such as diggers, they would have to be electric powered. This is not too difficult as most heavy machines are diesel->hydraulic, with electric->hydraulic conversion not too hard (run-time will suffer though).

If you wanted to start a colony, its easy if you can get 10,000 people to go as everyone doesn't have to wear a dozen different hats to keep things going. With current in-use launch tech, its unlikely that enough people can afford to go (or can get a loan to do so). If launch costs get down to ~$500k/ton to Mars, then it would be possible. The biggest issue at first would likely be getting enough electrical power from solar to refine metals and chemicals as that takes a lot of electricity and the likely first sources or raw materials will be sub-optimal as you would be prioritizing ease of access over efficiency.

[0]: https://www.cnccookbook.com/epoxy-granite-cnc-machine-fill/

> Why would anyone want to live like that

Think about not being under control of any government of Earth. This is literally a new world, for you to shape. For some people it's worth all the downsides, and more.

Not under control of any government on earth? It's not 2200 yet. Your entire colony will be dependent on earth for the rest of your lifetime. If we had evidence of nitrogen in martian soil and we had already sent machines that increase atmospheric pressure on the planet then you might be justified in thinking that it's just a matter of time. As it is right now you would have to live in an earth sponsored underground shelter and die in there. By defying earth you would just die sooner.

Instead, you'll have the pleasure of living under what amounts to a ubiquitous-surveillance dictatorship.

What, you think surviving under those conditions will work like a Heinlein novel?

What makes you think Mars would be like that more than Earth? Mars colonists can simply turn the cameras off when they want.

Your sponsors can also just stop supporting you when they want. An uprising on Mars can be struck down by waiting for everyone on mars to die.

Indeed! Instead, you’d get to live under a much smaller, less experienced, and more resource-starved government —- possibly a corporatocracy. Yay!

Control needs a basis from which to operate. I doubt there will be much of one on Mars initially. It would most likely be a direct democracy just because of the reality on the ground.

holes (lovely to live in)

People build hobbit houses and earthships and the like all the time.

https://en.wikipedia.org/wiki/Coober_Pedy

I think the digging aspect is being worked on. I don't think starting the Boring Co. was a random idea. Although the machines don't run on methane. Yet.

Don’t forget vacuum welding

https://en.m.wikipedia.org/wiki/Cold_welding

https://en.m.wikipedia.org/wiki/Vacuum_cementing

The first time it happened it must have been puzzling

My son is an engineer for a company that makes autonomous fork lifts. One month he was at a client at an aluminium smelter with the machines moving hot metal ingots around; the next month he was at a client that had the machines moving pallets of food product food around a warehouse-sized freezer.

Oh, I meant on the rover. From googling, it seems the helicopter's design lifetime is too short for radiation damage to matter, and the cameras actually on the rover are rad-hardened to some degree.

Generally cameras are reasonably rad-hard because the pixel size dictates a lot of the wiring size (and puts a lower bound on the process size). 3.5um pixels don't play well with 5nm features. Bigger features are generally more resistant to radiation fun.

Rad hard cameras intended for long term operation use CCDs with the drivers and ADCs off chip, implemented in a hardened process.

Then shouldn't the circle swept by the blades look slightly darker than the surround?

Apparently the sweep circle is there but nearly indistinguishable from the ground.

So the blades being lighter is a kind of motion blur?

But instead of the typical envelope for exposure, it's got a long and low tail?

For perspective, its not as easy as you would think. The air is extremely thin. Flying near the surface on Mars is like flying @ 100,000 ft. on Earth.

https://marsed.asu.edu/mep/atmosphere

from the website:

Relative to Earth, the air on Mars is extremely thin. Standard sea-level air pressure on Earth is 1,013 millibars. On Mars the surface pressure varies through the year, but it averages 6 to 7 millibars. That's less than one percent of sea level pressure here. To experience that pressure on Earth, you would need to go to an altitude of about 45 kilometers (28 miles). (Yes, you'll need a space suit to walk around on Mars.) The Martian surface pressure also varies due to elevation. For example, the lowest place on Mars lies in the Hellas impact basin, 7.2 km (4.4 mi) below "sea level." The pressure there averages about 14 millibars. But on top of Olympus Mons, 22 km (14 mi) high, the pressure is only 0.7 millibar.

A great video explaining how the helicopter works (and why it is indeed a feat of _ingenuity_).

https://www.youtube.com/watch?v=GhsZUZmJvaM

It was a nice trick how they simulated Mars gravity.

Thankfully gravity is also lower.

I was thinking a crash might be less damaging, but just looked up the gravity at 3.721 m/s². That would hurt.

Given the blades are spinning at not too far off from the local speed of sound, the blades would explode if they hit the ground I imagine, similar to helicoptor crashes on Earth.

Wow! I just looked up the difference in pressure and found that the "air" pressure on the surface of Mars is 155 times less that of Earth (1013.25 mbar on Earth, 6.518 mbar on Mars).

Yeah, that was really not expected and only found via space probes. That's why you see gliders for landing in many of the early Mars mission concepts but not in the newer ones.

Actually the atmosphere is too thin for full gliding or parashute landing but too thick to ignore it like we can on the Moon.

Still twice the Moons gravity with no atmospheric breaking at all would also suck I guess.

Basically means you need a lot more delta v too slow down. Which means burning a lot more fuel to first get below escape velocity (5km/s) and then slow down all the way to zero. Escape velocity for Earth is 11km/s. ISS flies at about 7.6 km/s. A typical Mars approach and landing starts at about 20km/s. Most of that is Atmospheric braking. So yes, that would suck.

From what I remember of playing around with X-Plane's Mars atmosphere model, you can glide, but at very high speeds (for most planes close to the speed of sound), you can barely turn, and it's horribly easy to stall.

Doesn't paint a good future for large scale aeronautics on Mars - even if you somehow can sustain those speeds in an atmosphere where you cant burn stuff for propulsion, landing the thing, somehow, at the destination would be very hard - possibly harder than landing the F-104 Starfighter!;-)

That speed likely rules out any normal landing gear or runways, possibly with the exception of a maglev catcher cradle.

Most likely the "aircraft" would need some sort of a robust long duration vertical landing capability, likely rocket based.

No wonder you don't see any aircraft on Mars in The Expanse series - only hyperloop like pods on flimsy rails making use of both the low pressure and low gravity or full on spaceships or orbital shuttles.

Yeah, the only real possibilities for landing on a runway are insanely long runways (dozens of miles!) or high-speed arrestor cables, like souped-up versions of those used on carriers. And even then, the super-wide maneuvering radius means flaring without stalling is practically impossible - you'd need to clear a long area in front of the runway so you can basically come in almost flat.

We need to "inflate" the atmosphere. That means digging up nitrogen deep in the soil.

If anyone was a stupid as me in thinking "wow that's not that high up!" the "death zone" for humans is 26k feet, where if exposed long enough we will die[1]

[1] https://en.wikipedia.org/wiki/Death_zone

Space starts at the Kármán line at 330,000 feet, the ISS flies at about 1,300,000 ft (100km and 400km respectively).

even 14k feet feels seriously noticeable and unsettling.

Another point of reference, 10,000 feet is the limit in aircraft. If pressurization is lost above that altitude, oxygen masks will drop and the pilots will make a quick dive to below 10,000 feet.

OTOH, La Paz, the/one capital of Bolivia, is at 11,942 feet.

https://the18.com/en/soccer-news/most-intimidating-soccer-st...

That tells you a lot about what can happen with slow adaptation / getting used to it as opposed to catastrophic fast change of the environment.

It's kinda true for climate change as well - just over much longer stretches of time.

The local native population does have genetic mutations adapting them to the altitude, as do of course Tibetans.

I've even heard anecdotes that they feel uncomfortable at sea level.

I'm pretty good up to around 10,000 feet these days due to where I live, but I felt like it took a few years.

Yes, and that altitude is right at the limit that helicopters on earth can achieve.

but the gravity is less, so it surely isn't that bad?

38% of Earth's. Still difficult as the atmosphere is too thin.

It's endearing to think of a rover having a companion helper.

I know the whole thing is impressive. But it's really hard for me to get past the awesomeness of rocket crane landing a rover on another planet. That stuff is crazy awesome.

I can't wait until we have the technical skills to land more autonomous bots to build landing pads/human liveable structures

that never dawned on me, you know it could be a way to start producing fuel for a return trip home too.

"never dawned on me" sounds like a great name for a SpaceX drone ship.

I think the autonomous drones are a key component to Musk's colony plans.

So far NASA has been doing plenty on Mars, and Musk has done zero. He does love to talk and blow things up.

This is not a rivalry, this is collaboration. NASA has different goals and SpaceX has different goals, but where they can, they're working together. Without NASA's contracts SpaceX wouldn't be where it's right now.

NASA can't remember the difference between feet and meters, and they are notorious for delay delay delay. They are also famous for blowing up some shit too. Sadly, they have even lost humans on multiple occassions. They are not perfect.

Musk has a rocket that can be reused multiple times, and can deliver to the ISS. NASA can't do any of that.

NASA has been around for 70 years, yet still no people on Mars. Just cute little robots that they hired others to build for them. Short Musk all you want, but he's the only one that I think will actually attempt doing things on mars than taking pictures and soil samples.

This is irrelevant, the ultimate objective on mars is finding nitrogen in the soil and releasing it into the atmosphere. If this is possible then it's the first thing you should do, perhaps hundreds of years before the first human steps on mars, if this is impossible, then going to mars was a bad idea in the first place.

What is NASA hoping to learn from this drone that they couldn't get from the rover? Is the point just to test if this type of flight is possible on Mars, or is the rover collecting some extra observations?

As other have said, it's a tech demo. Partly just to show we can do powered flight on other celestial bodies, part of it is to test how well the off-the-shelf parts in Ingenuity work in that environment. Rotorcraft require more computing power than is available from typical rad-hardened processors. Ingenuity is using a Snapdragon mobile phone chip, will be interesting to see how long it survives up there.

NASA have plans to use rotorcraft in many future missions, including the Dragonfly which will fly around Titan[0]. Launches in 2027.

[0] https://www.nasa.gov/press-release/nasas-dragonfly-will-fly-...

>Rotorcraft require more computing power than is available from typical rad-hardened processors.

Ingenuity uses a three-level control system for avionics[0] - the Linux part that runs on the Snapdragon 801 is at the top tier and does more the mission computer functions like navigation, computer-vision, telemetry, command processing and interfacing to the radio.

The middle tier is a dual-path redundant microcontroller system based on the TMS570 architecture. This is an automotive-grade part qualified for safety-critical usage. This an ARM Cortex R5 design, so not exactly a speed demon.

The bottom tier is a radiation tolerant, mil-spec FPGA (Microsemi ProASIC 3L) that actually runs the control loops at up to 500Hz, handles communication with the IMU, motor control interfaces etc; this part is actually supposed to be functionally identical to the space-qualified version.

The "Linux running on a smartphone processor" aspect gets a lot of play but the stack as a whole uses a lot more traditional high-integrity design approaches. Most of the heavy-lifting of "fly the rotorcraft" is done away from the Snapdragon, and I'm not sure where the idea that "rotorcraft need a lot of CPU power" comes from.

[0] https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

>Rotorcraft require more computing power than is available from typical rad-hardened processors.

the CPU on a fairly advanced quad, hex or octocopter on earth can be a STM32F7 or STM32H7 family microcontroller, which is not very powerful in terms of raw computing power. That's more than fast enough (in an earth environment) to pull in sensor input at a high Hz refresh rate from dual IMUs, barometer, GPS, and control up to eight motor ESCs, along with running the UARTs for communication to a remote control link, and additional spi, i2c or UARTs to do things like run camera gimbals.

https://docs.px4.io/master/en/flight_controller/cubepilot_cu...

Yeah, I think the biggest factor preventing such a simple design from working well on Mars would be the (current) lack of anything equivalent to GPS.

In order to navigate safely, especially during takeoff and landing, you need a reasonable idea of your absolute velocity relative to the ground. You can't get that from an IMU (except over very short timescales) because of integration errors. A barometer would work for the vertical axis, but getting the horizontal component is a lot trickier. GPS solves this nicely, especially since velocity can be derived from relative measurements, which are much more accurate than absolute ones.

It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide.

>It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide.

I believe that for Ingenuity they are actually doing this in software; but at this point, you can just buy off-the-shelf an optical flow odometry ASIC with a built-in camera and lens system that draws <5mA, fits in a 4x5mm footprint and gives you delta-X and delta-Y.

e.g. https://www.pixart.com/products-detail/108/PAA3905E1-Q

Kinda mind-blowing.

Is that kind of like optical mouse sensor?

Yes it is! Obviously it's a slightly harder problem if you don't know the distance from the surface and you can't provide your own illumination.

That's one of those missions I'm actually really hoping I live to see: a whole sequence of launches putting a GPS constellation into orbit around Mars.

At the relatively low heights ingenuity is flying at, a single point LIDAR rangefinder aimed straight down would also be well suited to maintaining a certain altitude.

In addition to the (very valid!) tech demo aspects of this, there's also the huge public interest/public relations aspect. I've seen more articles and comments on Ingenuity than on any other part of this Mars mission. (Personally, I'm excited for the MOXIE instrument[1] - tech that's all but mandatory before human missions)

[1] https://mars.nasa.gov/news/8926/nasas-perseverance-mars-rove...

> Quadcopters require more computing power than is available from typical rad-hardened processors.

Ingenuity isn't a quadcopter though, it has two blades that counter-rotate around the same axis.

> two blades that counter-rotate around the same axis

Which would make it a coaxial helicopter.

https://en.wikipedia.org/wiki/Coaxial_rotors

It's pretty funny to me that the processor on Ingenuity handily outperforms the one on Perseverance by several orders of magnitude.

That's the point of the demo. If Ingenuity's processor survives, then NASA can consider these more advanced processors. If it doesn't, then that means continued use of lesser capable but rad hardened processors will still need to be used. OR, it could mean a re-evaluation of mission lengths. if more science can be done using a more capable processor that is known to have a limited lifespan, then that will have to be evaluated against the benefits of longer missions with less processing requirements

They still have a sample size of 1...

Surely a better test would be to get 1000 mobile phone processors and put them in a radiation chamber on earth and see how many fail? It would be far cheaper and be better science.

But then we'd have no helicopter on mars right now

I reckon it might actually be cheaper to put together a smallsat with 1000 processors on it and stick it in low earth orbit. Building a chamber and finding all the radiation sources you'd need to accomplish such a thing surely is no small task...

Maybe we don't know the composition of the radiation on Mars precisely enough?

i've never thought about, but i don't recall any of the other probes/rovers reporting back on things like UVA/UVB or anything else like that. However, with no atmosphere or the Martian equivalent to Van Allen belts, wouldn't it be safe to assume that whatever streams out of the sun is reaching the surface? it would be a matter of intensity on the surface vs what type would it not?

Flying drones can open yet more places for exploration in the future - even with the new active precision landing feature introduces with Perserverance the landing elipse still needs to be relatively flat ground with limited ammount of obstacles.

If we want to see and explore deep valleys or high mountains before some future the first setlers go there with gopros and do a Twich stream then flying drones are a good option.

>Launches in 2027.

Hopes/Scheduled to launch in 2027 seems more accurate. Even when the rocket is fueled and on the pad, it can still get scrubbed.

The NASA site contains a lot of info about Ingenuity: https://mars.nasa.gov/technology/helicopter/ , especially this fact sheet (PDF): https://mars.nasa.gov/files/mars2020/MarsHelicopterIngenuity...

"Its performance during these experimental test flights will help inform decisions relating to considering small helicopters for future Mars missions, where they could perform in a support role as robotic scouts, surveying terrain from above, or as full standalone science craft carrying instrument payloads. Taking to the air would give scientists a new perspective on a region’s geology and even allow them to peer into areas that are too steep or slippery to send a rover. In the distant future, they might even help astronauts explore Mars"

This one's a technology demo.

Future ones might be able to peek over a rock/ridge for planning purposes or access an inaccessible cliff or small crater that's dangerous to rove into.

Is the data collected by MRO not useful for this as well? Sure, the resolution would be increased, so I guess that would have some benefits.

I tend to think of the rover and drone like one of those strategy games where you have to send out scouts to "discover" where to send the rest of the troops, and then plan out how many "moves" to do it in. But then I remember we have the MRO that has pretty much scouted the entire planet. It just takes us a lot of "moves" to get our troops there.

MRO has a max resolvable resolution of 1 meter - incredibly useful for planning, but not enough to keep a rover safe from harm, let alone do all possible science.

The max resolution from a low-altitude helicopter is probably two-three orders of magnitude more detailed

The rover itself also has high resolution cameras, so it should be able to detect things hazardous/interesting. The drone might be useful to know if it is worth climbing over a dune or whatever, but I still think MRO data would be useful for mission control to plot routes. So maybe the drone+rover would be much more capable as an autonomous pair requiring less input from mission control?

It's main task is as a technology demonstration, after it's time or power budget is expended the rover will continue with it's scientific mission.

A flight envelope.

https://en.wikipedia.org/wiki/Flight_envelope

It’s technology demonstration. It’s not really used for science, other than learning how to fly there.

They get flight data back. E.g. how late at Mars day it can fly (morning is better), how fast batteries wear out and so on.

Where are the shadows in the upper and lower right corners of the hover image coming from?

I guess they're not shadows. They're the tips of the helicopter's legs

Edit: in case it isn't clear, this a photo of the helicopter's shadow on the surface, taken by a down-facing camera in the underside of the helicopter. It has a sort of fisheye lens, so there's some distortion at edges

Looks like the landing legs of the helicopter? Difficult to say from just this image though.

These aren’t shadows but the helicopter’s legs.

Obviously, these are from the trusses in the studio. Must be.

Yeah, they had to choose the correct lens though. If too wide of a lens is used, you can still see the set with the moon lander from the 60s.

Your response gave me a chuckle.

How do you control attitude with just two contra-rotating rotors? I've Googled, but can't find an answer.

Extra points for why NASA chose this mode, and terrestrial drones don't?

This video

https://www.youtube.com/watch?v=GhsZUZmJvaM

explains it: they can change the attack angle of rotor blades for different positions, which produces a torque, though you have to compensate for the gyroscopic effect, which lags behind.

Humans cannot fly this, but computers can.

The video also explains why the chose two contra-rotating rotors instead of a quad-copter design.

There is a little more information in this hackaday article [1]. Both propellers have swashplates like a helicopter which allows them to control the pitch of each rotor.

[1] https://hackaday.com/2020/09/02/an-up-close-look-at-the-firs...

I know it's 21st century, but my mind is still blown when I see video from the surface of another planet.

what a time to be alive.

I had pong as a kid. I know we dared mighty things back then too. But this is so much fun.

You wouldn't want to be the one who crashes this

The communication delay between earth and mars in 9 minutes at the lowest, 42 minutes when the planets are far apart. If something is crashing the helicopter then it's a software bug.

As someone who writes software, the fact that it must be a bug is scant consolation when it crashes. It just means that you have no hope to prevent it by reflex, you had to fix it by thinking intentionally and carefully a long time ago when you wrote the software.

As someone who has written robot software, it's not as bad as you might think.

You do a LOT of testing before hand, and you do system checks before committing to something. I was always more worried about sensor failures that my software doesn't pick up on.

Then again none of my robots ever cost $80 million dollars and has landed on Mars...

I have written robot software...curious what context you were in.

I've been doing industrial automation with commercial robot arms, where testing is mostly functional and there's very few system checks. You're basically jogging the robot with the teach pendant, recording points, and reading digital IO. There are minimal system checks, simulation is mostly to make sure the cell CAD layout is reachable and less to verify that things are working correctly. Version control is completely offline, there's not even an "undo" feature to revert a touched up point unless you underwent a tedious and slow backup procedure.

That said, like you, none of my robots cost more than 6 figures, and they're all permanently anchored to terrestrial steel and concrete...

I wouldn't want to be the one (software developer) who (wrote the buggy software that) crashes this.

In the last flight when they'll try to reach over 2k feet they expect the heli to crash. So the one operating (well, not in real time as already pointed) it at that time wants, or better phrasing is expects, to crash it.

It's not like someone is controlling it live, I'm sure there are multiple people reviewing the commands.

I am paranoid probably, but I am worried that the helicopter might crash on to the car.

Could the drone also be used as a means to dedust the rover if it was using solar panels?

The Perseverance rover is using a plutonium-powered radioisotope thermoeletric generator (RTG) this time that I think is rated to provide something like 100 watts for something like 15 years.

For the solar panels on the Ingenuity helicopter, it's my understanding that the flights do already help keep them clean.

Ingenuity is highly experimental, but even for a future Mars helicopter I doubt they would risk flying it in close proximity to the rover.

> using a plutonium-powered radioisotope thermoeletric generator (RTG) this time that I think is rated to provide something like 100 watts for something like 15 years.

Or provide enough heat to keep a stranded botanist warm for a brief cross country drive.

Just a note on this: you can’t “increase” the power output of these things. Basically you can imagine these power sources as a “heat pack” that lasts a very long time. So, while you can “store” the energy, and release it later... you can not “use it faster”.

As it produces 100W of electricity, the RTG also produces way more energy as heat. According to Wikipedia, the efficiency of an RTG is usually around 3% to 7%, so you get kilowatts of heat.

https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...

So, it's same order of magnitude to my electric space-heater, if it was stuck to "on". I trust Andy Weir's calculations on whether it is about right to keep a botanist warm on Mars.

Couldn't you use something like a Stirling engine to create more electricity from the excess heat? You might have to have an external radiator to create a heat gradient with a closed loop of liquid but it certainly seems possible.

Yes, you could, and you could do better with more moving parts and more stages, but they're optimizing for reliability not for power.

In theory, the best you could do is (T_hot - T_cold) / T_hot, or (430 - 210) / 430 ~= 50% , using some approximate values for fin root temperature and Martian climate. To exceed 10% of the theoretical optimum with something that contains no moving parts is pretty impressive, IMO.

Couldn't they use the heat to to drive the wheels directly, maybe they could go to more of a hybrid drive? Just seems like such a waste to produce that much heat for 15 years.

I'm not sure how heat would turn wheels directly. You need to convert the heat into either mechanical or electrical energy somehow. Any such system involves tradeoffs in efficiency (in terms of useful energy captured) against weight and reliability.

Specifically you wind up needing grease/oil more moving parts. The failure rates of reaction wheels on orbital craft speak well to the relative difficulty of keeping moving parts moving in space-environments without ongoing maintenance.

AFAIK NASA is already experimenting with Stirling engines + Plutonium for future missions. It’s called ASRG https://en.m.wikipedia.org/wiki/Advanced_Stirling_radioisoto...

well, unless you bring a number of the inner contents of several such packs into very close proximity, at which point the reaction is going to be very much accelerated.

Warranty probably not valid if you get anywhere near criticality ;-)

Wrong isotope. The Pu238 used in RTGs is not fissile (does not undergo a chain reaction) - it decays by alpha decay. The fissile isotope used in weapons is Pu239.

Just don't recreate the Demon Core... they're both plutonium, right?

I can't imagine the risk of flying in close proximity would be worth it. If you crash into the rover you could jam up the wheels or a piece of scientific equipment.

We know from Spirit and Opportunity that dust on the panels isn't much of a concern; wind seems to clear them regularly.

A large constraint on Spirit and Opportunity was keeping the panels clear, that's why they lasted so long.

From what I remember, during martian winter they had to take the grade and the prevailing wind direction into account to keep the dust and fines off.

Currently the InSight lander is going into hibernation because the solar panels haven't really gotten cleaned in 3 years: https://www.cnet.com/news/nasa-mars-insight-lander-limits-op...

It's already been three years? Feels like a few months ago. Wow.

Still can't believe we've got proof of Marsquakes - that alone turned the consensus on planetary geology upside down.

The dust is electrostatically charged, and the atmosphere is extremely thin. It probably wouldn't help.

I imagine a tuned laser could ablate the dust, but that's a very expensive way to recover a solar panel!

Needs more flashing bulbs; martian raptors are shy and will not be lured easily.

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