6 ms·
We will use more helicopters instead of rovers for new missions ? Or larger crafts would be much harder or riskier to use ? Or maybe have a helicopter that ca
by simion314 3y ago
We will use more helicopters instead of rovers for new missions ?
Or larger crafts would be much harder or riskier to use ?
Or maybe have a helicopter that can move the rover with the equipment to different locations.
- wyldfire 3y agoThe existing helicopter is extremely small and light, IIRC. less than one kg. So it definitely won't be picking up a 900kg rover, even if you tried to scale it up somehow. The atmosphere is just too thin to support anything but a minimal payload. But yeah having more helicopters might be feasible - for surveying the surface.
- mmbop 3y agoIs there a problem of scaling this up to say a 20kg payload? I’m not an aeronautical engineer, so I guess what I’m asking is if there is some problem scaling up flying machines in an extremely thin atmosphere?
- deleted 3y ago[deleted]
- nortlov 3y agoIn a thin atmosphere, lifting a heavier payload needs bigger rotors or increased RPM, which increases power demands and structural stress. The challenge is to keep the vehicle light enough to fly while also making it sturdy enough to carry the payload and survive environments.
- mmbop 3y agoOk - this makes sense to me. Also taken into account the context that anything going to space needs to be light at this point in time. Hopefully we don’t have that restriction forever :)
- D13Fd 3y agoWhy can’t “more rotors” be another solution?
- swells34 3y agoThis is what I'm thinking too. A number of posts above talked about physical limits based on speed of sound and rotor length. Cool, so add two rotors, or four.
- nortlov 3y agoFor sure, that’s another way to decompose “bigger rotors”. It would probably be appropriate to dive into a conversation about Ingenuity’s design goals, requirements, and the trades performed to end up with what they got.
- Robotbeat 3y agoIt scales up to 20kg, yes.
- wongarsu 3y agoOne issue might be rotor span. Ingenuity has pretty big rotors to counter the thin atmosphere (about 4 feet top-to-tip). On earth rotor sizes are limited by the speed at the wing-tip. Once you make the rotor too long the tips start approaching supersonic speeds, giving you all kinds of weird mach effects. To make matters worse, the speed of sound is about 30% lower on Mars compared to near earth's surface.
- jessriedel 3y agoYea good point. Apparently the blade tip speed on Ingenuity is Mach 0.6-0.7!
- skovati 3y agoInteresting note about this: the speed of sound on Mars is only ~70% of that on Earth, due to less atmospheric density. Might change your Mach numbers!
- Metacelsus 3y agoIt's not due to less density, but rather a different gas composition (CO2 vs. N2+O2).
- algas 3y agoLet's run the numbers! The speed of sound in an ideal (calorically perfect) gas is given by a = sqrt( gamma * R * T ) where gamma is the ratio of specific heats (thermodynamic property of a gas, which may vary with temperature), R is the individual gas constant, and T the temperature of the fluid. All of these are going to be different on Mars versus on Earth: Earth: R = R_atm = 287 J / (kg * K) gamma = 1.44 T = 293 K (taking room temperature as an average temperature) Mars: R = R_CO2 = 188 J / (kg * K) gamma = 1.37 T = 210 K (from a quick google, about -60 deg C) If the Martian and Earth atmospheres were at the same temperature, then the speed of sound on Mars would be 80% that of the speed of sound on Earth. Given the temperature difference, the speeds of sound are a_mars = 232 m/s a_earth = 347 m/s So yes, much of the difference is due to the composition: the Martian atmosphere has a higher atomic weight, which leads to a lower individual gas constant, and decreases the speed of sound. However, a substantial amount of the difference is simply due to the different temperatures on the surfaces of the two planets.
- jessriedel 3y agoI don't know the answer to your question, but for context here are the weights of Mars rovers: Sojourner (1997): 11 kg Spirit & Opportunity (2004): 185 kg Curiosity (2011): 899 kg Perseverance (2020): 1,025 kg
- mmbop 3y agoI know these are much larger - I’m just really curious about the dynamics of scaling up rotorcraft & why it is problematic. ie - do rotor physics become impracticality large or fast at some point for materials science, or is it purely a space problem for rocket launches.
- jessriedel 3y agoOh for sure, it's a great question.
- IamTC 3y agoI have led efforts building Chinook style tandem rotors with 2 sets of blades from a size like the Trex 800, powered by a 2 stroke engine, as well as 40kg max takeoff quad-planes with both electric quadrotor and 2 stroke engine (for forward motion). But because I was the main lead and pushing the pace so fast, I wished I did it with a more rigorous aero-engineering to it. I started both projects with barely any experience developing aircraft. Thinking about your question, here are my 2 cents: The biggest thing I stugged with is how the vibrations and the accompanying harmonics on the sytem as the rotors spin up and down. I could see it on the logs as the rotors spin through certain Hz, there's would spikes in virbational ampiltudes at predictable frequencies. As the blades get bigger the forces (probably) goes up. Sometimes, these frequecies (especially the lower ones) are at the range where its very hard to find the right materials to damp it out of the control and sensing electronics. Ingenuity probably deals with a virbration range that well into the hundreds/thousand of Hz and I do remember that renge is not a difficult range to damp out, vis a vis the low tens of hertz. Also, the harmonics is related to ground resonance. I had built my tandem with "skids" that are rigidly attached to the rest of the frame. When the system made contact with the ground on just one skid, that one skid becomes a pivot, the vibration has no where to go and I witnessed first hand, first time, what ground resonance can do to mechanical systems. I can never forget seeing M4 through to M8 hex holt beads being sheared clean off after the resonance event. Only later did I find out that in full scale systems, they have dampeners between the main body and the skids of the aircraft. See https://m.youtube.com/watch?v=IIC-oBzLYhQ https://m.youtube.com/watch?v=IIC-oBzLYhQ ; Staying in flight is not as hard. But getting the ssytem to land and spin down proerly was big pain without understanding ground resonance and its effect on mechanical design. When I saw the little puny legs of Ingenuity, this experience of mine came into mind and I was glad they had legs like to damp out vibrations as it came down to land. Then there is the relation between the mechanical vibration regimes of the system, the polilng rates of the foundational flight sensors and the freqency of the main flight stability and movement control loop itself. With bigger systems, the cables (for signal and power) could run longer too (becoming long long antennas), which means you can run into problems with noise of various origins. If I'd do it again, something like CAN bus would probably be something I look at seriously. Bigger systems also draws more power, and that can have an impact on how much management is needed for noise. Bigger power draw usually also means heavy power store & delivery system, which affects CG management, when then means you can't move things around to management noise. At some point, I felt like I was doing dancing a multi-factorial show. I wished I could be clearer. Perhaps someone more qualified can chime in.
- jvanderbot 3y agoHere's a paper that describes what the next gen could/should be. The lead author is the head of Mars heli, IIRC. https://ieeexplore.ieee.org/abstract/document/9843501 https://ieeexplore.ieee.org/abstract/document/9843501 In short: 30kg heli, 5kg payloads. Other designs by collaborators are closer to 20kg. It's probably possible to transport a few of these on the existing lander technology, which would be awesome. The scholar.google.com keywords you want are "Mars Science Helicopter" and a good touchpoint author is T. Tzanetos or S. Withrow-Maser Ames and JPL were still collaborating on this when I worked there.
- Firaxus 3y agoI was surprised to learn that it’s actually a fair bit heavier. I was lucky enough to get to attend a talk by the head of the Ingenuity program, and he mentioned how the mass ballooned a bit to something under 5 pounds. (Listed as 4 pounds on this official fact sheet) https://mars.nasa.gov/files/mars2020/MarsHelicopterIngenuity_FactSheet.pdf https://mars.nasa.gov/files/mars2020/MarsHelicopterIngenuity...
- surfpel 3y agoThat's the goal, yes. Depending on the destination, naturally. Here's what's planned for Titan: https://en.wikipedia.org/wiki/Dragonfly_(spacecraft) https://en.wikipedia.org/wiki/Dragonfly_(spacecraft)
- jvanderbot 3y agoWas going to post this. Titan is such a wonderful place for a nuclear powered helicopter. Much better than rover/submarines/floaters, IMHO. A balloon would also have been excellent, but the extra mobility from helis is going to be amazing.
- wongarsu 3y agoIngenuity was just a technology demonstrator. I think it demonstrated the technology splendidly, so we are likely to see more helicopters on Mars in the future. Not sure if Nasa has said yet which roles they see for future Mars helicopters. The initial idea behind Ingenuity was to use them as scouting vehicles for rovers. Of course rovers improved a lot too, with better autonomous driving. But with a Mars rover driving about 100 meters/yards per day scouting helicopters are still useful. Maybe we will also see Helicopters carrying more instruments themselves. But I imagine in the beginning that's mostly better imaging instruments. Weight is still an issue for flying things, no matter the planet. But maybe we will see some future missions that instead of a car-sized rover and one tiny helicopter have a fleet of helicopters with a small support-rover for exploring wider areas.
- jessriedel 3y agoI think the current plan is that helicopters will be very light with minimal instrumentation and will be used mostly to scout ahead for rovers. The rovers will be much heavier and include many instruments. (Of course, all of NASA's long-term plans for Mars would be completely disrupted if Starship lowers the cost-per-kg of delivering equipment by two orders of magnitude, which arguably is likely.)
- kibwen 3y agoMaking it more economical to escape Earth's gravity well isn't going to alter the physics of the Martian atmosphere or the relative utility of copters vs rovers for Martian exploration. Which is to say, even if you stationed humans on Mars, they'd still be exploring remotely via copter/rover pairs, just no longer with a human-to-robot latency measured in tens of minutes.
- wongarsu 3y agoHowever we might be willing to drive a lot more agressively if we know we can get a mechanic out to a stuck rover. Similarly, cheaper delivery might make a large number of smaller more disposable vehicles more appealing for many missions, just like what happened to satellites in the last decade.
- jessriedel 3y agoIf you increase the mass and/or number of vehicles by 100x, a bajillion things will change.
- jvanderbot 3y agoA heli that can move a rover is basically worse than a heli that has rover instruments and a few wheels. You have extra weight and parts and complexity for hitching and carrying that you can just avoid by giving a small rover flying ability. Even the combo is probably too much complexity. A heli with good imagers, spectrometers, and the ability to cart soil samples would be fantastic.
- jvanderbot 3y agoSurfacing a comment: Here's a paper that describes what the next gen could/should be. The lead author is the head of Mars heli, IIRC. https://ieeexplore.ieee.org/abstract/document/9843501 https://ieeexplore.ieee.org/abstract/document/9843501 In short, future designs target ~30kg heli, 5kg payloads. Other designs by collaborators are closer to 20kg. It's probably possible to transport a few of these on the existing lander technology, which would be awesome. The scholar.google.com keywords you want are "Mars Science Helicopter" and a good touchpoint author is T. Tzanetos or S. Withrow-Maser
- two_in_one 3y ago> Other designs by collaborators are closer to 20kg. It's probably possible to transport a few of these on the existing lander technology, which would be awesome. Actually it could be like 50 of them. Plus some ground robots to put together solar farm. And wooh... we get the first extra terrestrial permanent base
- jvanderbot 3y agoWell size is the limiting factor for fliers, since they like to have broad surfaces with low weight. But I think you're referring to some, ahem, untested possible landing vehicles ... in which case, yeah, you have a lot of robots. For the solar farm assembly case, It's actually a lot easier to have a teleoperated robot doing the work, a few astronauts in orbit doing the operation / construction. In the case of building things, you want as much space / weight landed to be the thing being built, not the builders, per se.
- Keysh 3y agoNon-paywalled article about the concept, including renderings of the hexacopter design: https://spectrum.ieee.org/the-next-mars-helicopter https://spectrum.ieee.org/the-next-mars-helicopter
- deadbabe 3y agoWhy not some helium balloon type craft that could float along with low power for longer periods of times? Could cover vast distances? Descend into fertile plains looking for samples?
- Jabbles 3y agoHelium's lifting capability is proportional to the density of the atmosphere, which is very low on Mars.
- bloopernova 3y agoIs it viable to use vacuum instead of helium?
- nilsherzig 3y agoWouldn't you need something with some amount of pressure to stop the "shell" you plan to float from collapsing?
- anticensor 3y agoWhat if we use hydrogen, which is halfway between helium and vacuum?
- deadbabe 3y agoHydrogen it is.
- M95D 3y agoHydrogen leaks.
- somenameforme 3y agoMinimizing moving parts, so much as possible, when dealing with hardware tens of millions of miles away, let alone with a 13 minute delay in 1-way messaging, is generally smart. And Mars' atmosphere is so thin that these rovers will never be moving any meaningful payload, so their only real use case is as a scouting type system. But they also add very little value there given the existence of orbiting satellites. Even the Mars Recon Orbiter (from 2005) captures images in the < 1m resolution range. IMO NASA wanted to try to deal with the sort of 'oh boy... another rover' fatigue and saw the drone as a way to spice things up with some passable science arguments behind it, and a relatively minimal cost. Further supporting this is that the helicopter wasn't an initial part of the plan - it was strapped on at the 'last minute', speaking in government time. In any case, I would comfortably wager against us seeing more drones in future missions, at least to Mars.
- analog31 3y agoIn the shorter term, I see the helicopter as making the rover more capable, by finding routes and destinations of interest. And the rover makes the helicopter more capable by providing a recharging station. So they're both at their best when working as a system. Maybe a rover can support multiple choppers.
- p1mrx 3y ago> the rover makes the helicopter more capable by providing a recharging station Does it? I thought the helicopter was just solar powered.
- analog31 3y agoThat's cool. Thinking about it, there must be a tradeoff. The rover could support more massive batteries, but then "docking" between the two machines would have to be utterly reliable.
- dotnet00 3y agoIIRC as a result of Ingenuity's success, one of the proposals for the Mars sample return mission architecture involved several helicopters to retrieve Perseverance's sample canisters (it drops them as it goes along, so that there's no worry about how to get the samples out of the rover in the future). I should add though that the prospects of the parasites in Congress properly funding such a complex mission seem pretty low for now.