In the video they tout the X-57 as a contribution to the “urban air mobility market”, arguing that small aircraft can decrease commute times and avoid congestion. This seems very backwards to me. Cars are already very inefficient in their use of space, since they require large amounts of space around them when they are moving at speed. I expect this issue to be significantly worse for aircraft, with the speed they are moving at, the safety distances needed to avoid crashes, and the volume of air they are disturbing around them. While they can potentially make use of the vertical dimension for more space, they still have to move through the surface layer for take-off and landing and will want to stay close to the ground for short trips. And they potentially add a lot of noise to an already noisy urban environment.
I’m all for ambitious research projects pushing the boundaries of electric flight, and there’s probably reasonable use cases for planes like the X-57. But a sustainable urban transport future looks much more like buses and bicycles rather than small electric aircraft.
You are ignoring the fact that cars have to navigate what is basically a set a of 1 dimensional corridors on a 2 dimensional plane. Airplanes don't have these limitations and can fly point to point at their choice of altitude.
Currently most of the congestion in aviation is around airports which are necessarily optimized for large jets. With a small airplane, you can fly to a much larger variety of airports, around ~50K world wide and it's relatively straightforward to build even more of them as needed.
Noise is a function of propeller size, rotation speed, and engine noise. Simply put, lots of small propellers rotating at faster speeds driven by electrical engines are a lot less noisy than larger props driven by combustion engines. The physics around this are complex and involve things like the speed of sound of the tips of the propeller (you break that limit at lower rpm for larger props), the mass and thickness of the propeller, vortices, etc. Basically, all of that improves with smaller props.
Compared to a loud helicopter, an electrical plane at the same altitude could be a lot less noisy to the point where in a busy city you'd hear one but not the other above the ambient noise.
I'm guessing that the break-even point on space efficiency is somewhere close to the point where you invent Blade Runner-style levitating cars that require zero extra space for take off and landing, and can move arbitrarily slowly, or even come to a complete stop, without falling out of the sky.
Without that, I doubt that that adding some room for vertical stacking would offset the amount of additional lateral space they end up needing.
And I believe that effect would be intensified by the the amount of vertical stacking you can reasonably do being constrained by how far a vehicle needs to move laterally in order to gain or shed a given amount of altitude, and the distance of the trip being made. For a traditional fixed-wing aircraft operating over "urban commute" distances, that constraint would be downright tyrannical. For Blade Runner style levitating cars, it would be no big deal.
> cars have to navigate what is basically a set a of 1 dimensional corridors on a 2 dimensional plane. Airplanes don't have these limitations and can fly point to point at their choice of altitude.
That's not entirely correct. Planes also have corridors in the sky. Just like roads, there are the highways (with different altitudes for different directions) and slower lanes for smaller aircraft. And airports are basically a confluence of many lanes, which requires a coordination (air traffic controllers).
Depends on what class of airspace you are in and weather you are flying under IFR or with some kind of flight following & flight plan. But even then the air ways can be stacked vertically.
If you are flying vfr and in an airspace where that is allowed, you can pretty much go where you want as long as you stay away from controlled areas. Basically most helicopters fly VFR. The recent accident with Kobe Bryant involved a VFR flying helicopter flying into fog in LA.
True, but to provide reliable commuting you pretty much have to fly IFR, especially in a place like SF Bay or LA. This is because often marine layer clouds don't clear until 10am and people want to be at work long before then.
It may be possible to do a lot more to improve the availability of IFR approaches and routes if we factor in automated systems. It's going to take a lot longer to build more airports, but I can tell you that pretty much every airport manager in the United States will be thrilled to face that problem.
The FAA is trying to eliminate the need for those corridors under the "Free Flight" program, however progress has been slow and it's unclear whether this approach will ever be fully implemented.
>You are ignoring the fact that cars have to navigate what is basically a set a of 1 dimensional corridors on a 2 dimensional plane. Airplanes don't have these limitations and can fly point to point at their choice of altitude.
Absolutely true. However cars are mostly autonomous and airplanes flying through urban airspace are not, with rare exception. The bottleneck will be our air traffic control system, which can not in its semi-automated form scale to the volume required and would not qualify for the usual SV "move fast and break things" treatment, since "breaking things" in this context would be in-air near misses and collisions.
True, this is as much a cultural and legislative problem as it is a technical problem. IMHO, having lots of autonomous capable planes will create a need for having them interact with some form of automated traffic control that does not yet exist.
Building that technically is much less of a challenge than getting it certified, standardized, and integrated in the aviation world.
IMHO this will play out over decades and will be driven by increasing traffic volumes of basically fully or semi autonomous vehicles causing issues with the current system.
But if you think about it, doing things the way we have been doing for the last 70 years with analog radio broadcasts, call signs, people using archaic jargon, chattering about altimeter settings, verbal communication of flight plans, having to monitor multiple radio frequencies, etc. is maybe not optimal in a world where all that info could be exchanged in ms between two autonomously operating systems.
Yup yup - I'm not defending the status quo as much as just commenting it's not built for the future utopia of self-directed or autonomous private aviation. Commercial aviation puts pressure on Congress now to try and marginalize general aviation due in part to system constraints; every private flight that displaces a commercial one is revenue lost as far as they are concerned.
Would appreciate some pointers for that; I'm interested in this space. My understanding is that governmental institutions are moving at a glacial pace here. E.g. ADSb took decades to get deployed (mandatory in lots of places as of the beginning of this year) and is technically less than ideal because of a lot of design by committee stuff interfering.
I'm aware of some automated ATC efforts on smaller fields that would otherwise be uncontrolled.
Have you seen/heard recently built rescue helos in action?
Been very surprised by them. The loudest thing is the whine of their turbine, but not that loud at all. There are many louder cars and motorcycles on the street. I don't know the type anymore, but it was something built by Airbus Industries, based on some Eurocopter platform. Worlds apart from those old Bell UH-1s!
I believe they will be use for the same thing helicopters are used today:
1-Emergencies and organs transplant. No pilot means more carry load in volume and weight.
2.As a status symbol for top of the ladder executives and polititians. They will go from the top of skyscrapers to their mansions just looking down of those that waste their time in car jams.
I see this being useful for short distance travel as well, but not that much in cities, but outside them.
the parent of your comment is referring to the phrase “urban air mobility market”, which the X-57 PR video demonstrates as being small aircraft, a few of which were VTOL craft -- not the X57 itself.
The PR video was basically hinting at the X57 being a technology demonstrator which will showcase techs (like electric propulsion) that the so-called “urban air mobility market” can then take off running with.
> "It's still a plane, it has no VTOL capability. It cannot be used for what helicopters are used today."
This one, yes. But there are many "urban transport" VTOL electric aircraft in development. The idea is to combine the utility of a helicopter with the efficiency of a fixed-wing, while adding the environmental, reliability, and O&M cost benefits of electric.
I believe that, in the coming years and decades, electric VTOL aircraft will replace traditional helicopters for many applications.
Ya, I did a ride along with the highway patrol once. 1 hour of that shift was driving to the far end of our coverage area and waiting for another car. Then blazing down the freeway in the opposite direction at 3am at top speed on what they call a "blood run" (organ in a cooler in the trunk). There are no commercial flights at this time of day and the organ was moving about 5 hours by car. This would have been much safer and faster if it were done by helicopter or small plane, but I guess if the car works then they don't have to use aircraft.
Completely depends on the organ. Kidneys can survive outside the body for 1-2 days, while heart and lungs only survive 4-6 hours and are typically transported via ground or air ambulance, depending on distance.
And at a large Midwest hospital. But with the advent of professional "Hospital Administrators" with a degree and everything, hospitals become a business. Anything they can get for free, they do.
The thing is that cars (and bikes, and to some degree planes) are point-to-point. This decentralized mode of transportation is much more efficient when it comes to satisfy the needs of many commuters. For instance, by bike I save at least half of the time compared to Subway. And I have access to a well-developed subway and I do not need to change.
I agree, though, that planes will never be a replacement for cars or even bikes. That is because the utility per € is much higher for the former. A bike is generally cheap. A car is much more expensive but can carry four or more persons very far in pretty much every weather. A small electric plane is going to be even more expensive (conjecture) but otherwise worse than a car.
Agreed except the fabled concept of the flying car which NASA has been tinkering with for a long time. (Don't know if they still do. Not tinkering with as in actually building it, but thinking about "lanes" in the air, collision avoidance and such.)
I don't see why any electric vehicle can't be part of the sustainable urban transportation future.
There is no one-size-fits-all solution. Would it be better if we built cities around public transport? Generally yes. Does that mean there isn't a place for electric aircraft, electric cars, and smaller personal electric vehicles (bicycles, scooters, segways, hoverboards, skateboards)? Nope. I don't think anyone in this thread thinks that all of our future transportation needs will be satisfied by flight.
And given our current state of global pandemic, I think we can probably agree that even without the pros of other forms of transport, public transit has its own unique downsides.
Right but the comparison is being made against "ground transportation" in the video. Light aircraft are already a component of urban travel (notably helicopters) and merely making them electrically powered isn't going to dramatically increase their utility which again is what the visualization in the video shows.
Making them electric is fairly important for a carbon-neutral/negative future though.
Also even without helicopters being fossil-fuel powered, they have a number of other downsides: not nearly as safe as winged aircraft, louder, harder to fly, etc.
Yes it's a great idea to make electric aircraft for all sorts of reasons. Notably this design (as per the paper linked elsewhere) gets 300% more efficient for just switching to electric motors.
I'm giving context to the discussion from the parent of this thread. The nascent category of aircraft is being heavily marketed as a replacement means of transport for commuters. Which is why people are talking about them in that context.
While I agree about the hope for this being a solution to mass transit in urban areas...
Cars don't merely require "space", they require space that has road on it with tarmac and signs and lights and junctions, and they require it in a limited 2D plane and that is the same 2D plane that we need space for buildings etc.
Planes work in basically any space and require no infrastructure.
There is a metric shit tonne of space for planes right now just waiting for use. The same is never true for cars.
You got it wrong. Airspace over cities is very limited. At some point you get to the height in which long distance flights travel.
Also, all aircraft have a minimum required safe distance between them tht needs to be large due to aerodynamics. This it become physically impsible to increase traffic density beyond a certain, low threshold.
I believe the overall goal of urban+suburban mobility is to increase the number of modalities of transport available. So adding scooters, busses, trains, uber, helicopters, planes, boats, etc.
Cars move in a 2-dimensional space (surface), aircraft move in a 3-dimesional space (without costly highways), so you can utilize space way more efficiently and move more people per square mile.
The safety distances will probably reduce due to automated collision-avoidance systems which may become mandatory in dense flight areas.
Although, I don't know how planes compare to cars in terms of energy utilization efficiency. A car only needs energy to move. A plane needs energy to move and stay above the ground.
Aircraft require significantly more space between them in order to operate safely so I doubt the efficiency is there even taking into account stacking in an extra dimension. They're also pretty weather dependent in comparison to other options so capacity can vary a lot.
If we actually cared about efficiency in urban transport we wouldn't have personal vehicles beyond bikes and small electric vehicles. We'd rather rely on public infrastructure like subways, trams, trains and buses.
Nothing can move more people than a subway, certainly not single person planes that need to land and still consume space when not in use, just like cars.
> Cars move in a 2-dimensional space (surface), aircraft move in a 3-dimesional space (without costly highways), so you can utilize space way more efficiently and move more people per square mile.
You still need to land planes 1 at a time, and that involves a clearing period between landings.
The X-plane program does fundamental research. All military and commercial aircraft have benefited from that research, in the same way WW2 German designs also influenced the world.
X-57 is fundamental research, not an effort to create a final product. The closest program similar to it is the X-29, which investigated forward-swept wings, canards and augmented computer systems to control them. (Nobody wants forward-swept wings because a failure in wingtip rigidity or the computer software destroys the structure.)
As a commercially-rated airplane pilot and informal aerodynamics student, I think the wingtip propellers are questionable, and the retractable inboard propellers sound like a maintenance and operations nightmare.
What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement.
What's misunderstood about wing tip vortices is that regardless of what the loss is, that flow comes from the entire wing producing lift, so is unavoidable. There are already passive techniques like winglets and fences to direct vortices that don't require daily maintenance.
And we know from the Osprey that complex propeller systems fail too often. A dozen propellers means an order of magnitude more inspections, replacements, ground time (AOG), etc.
At $83,000/hour to operate, a V22 Osprey is more expensive than an A380. Also, read the section on "Design Challenges":
Additionally, there is no "urban air mobility market" in the USA, and never will be, due to regulation and insurance requirements. In a showdown between the FAA and Uber, the FAA will always win, and the FAA reserves the perogative to change its mind later, as in drone regulation.
To give you an idea, it was easier to start SpaceX than it would be to get the FAA to allow "urban air mobility." So regulation is the real challenge, not technology.
> What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement.
They're generating lift at low speeds by using the array of small motors, and then optimizing the wing for cruise lift. It's really brilliant. And it'll result in better handling in turbulence too. Frankly I'm stunned at the direction they've gone here, it's really remarkable and is a major shift in approach to aerodynamics that has huge implications across the industry.
> To give you an idea, it was easier to start SpaceX than it would be to get the FAA to allow "urban air mobility." So regulation is the real challenge, not technology.
I though the regulatory hurdles around "urban air" come straight from the need to protect people and property from the dangers of a) falling aircraft (which would become a real concern as the use scales up), and b) excessive noise. And I'd guess c) dust clouds. We'd have to invent propulsion that's much more quiet and doesn't push air around for air taxis to make sense. So this would make the root cause of those regulatory problems be technology problems (or perhaps even physics problems).
Large-scale urban air transport would also have to be entirely autonomous. Drunk/distracted driving is already a major issue and cause of death in the United State. In three dimensions and when failure of control can result in collision with any arbitrary part of any structure, this is obviously a non-starter. So getting the FAA to sign off means not only producing a design that must be, elevator style, mechanically essentially incapable of failure, but also getting them to sign off on an autonomous low-altitude flight system for use in dense airspace.
1) a flying car is going to be treated like operating an airliner if money changes hands to carry passengers. To give you an idea of what that costs, consider that an adequate tourism helicopter is $2 million.
2) otherwise, there's a rule for built-up areas that requires flying 500' over people and structures. That doesn't count for landings on regular airports and EMS helicopters on top of hospitals, but does pretty much everywhere else. Not terribly useful for commuting downtown.
3) the FAA regulates airspace and airports, but municipalities generally say no in urban areas when private citizens ask to operate helicopters off-airport. Steve Jobs found that out when he tried to get permission to use one for personal "urban air mobility" either in Palo Alto or Cupertino.
So to conclude ...
If you wanted agreement from the FAA and municipalities to do the "urban air mobility" thing, you'd need to start with what I wrote and devise a compelling argument that satisfies their concerns. Note that wasn't done with drones, and look at how restrictive the rules are now. It will be far worse if you want to charge money to carry passengers.
Rightfully so - passengers expect to embark, travel and disembark without making the headlines.
And you need a plan for what happens after the first accident that kills a passenger. Because not just one air mobility company, but all companies, will be mercilessly hammered by the FAA. Can you afford to shutdown for a year or two while the NTSB and FAA do their thing?
I'm aware of that, but the comment blamed this on needing to be "treated like operating an airliner". In reality, tourist helicopters are much better (and more expensive) than an R44 principally for reasons other than the FAA's treatment of them. Also, I believe that the Bell 206 is well under $2 million as well.
Re: Osprey, the X-57's electric motors are vastly simpler than the fueled gas turbines + driveshafts in that aircraft. All you do is run wiring down the wings, with the Osprey you're running pressurized, flexible fuel lines into a movable nacelle with enormously complex turbomachinery to do all of the compression + combustion. These things are a pandora's box of fatigue problems from the multimodal vibrations and it takes years to analyze them all.
You also can't compare operating costs of a military vs. civil aircraft. VERY different priorities, military aircraft have dramatically higher requirements due to where they operate (desert sand anyone?) and their mission. EVERYTHING gets inspected, components are designed to be performant like Formula 1 race cars and not necessarily for lowest operating costs. It's like comparing an M1 tank, which gets 0.5 mpg, to a Ford F150.
> What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement.
This is nonsense, there's no rule of the thumb that states any random wing reduces prop thrust by 50%. You must calculate it. It's a very complex unsteady flow field dependent on all of the geometries involved. It will vary on flight condition obviously.
> informal aerodynamics student
I'm sorry but the average pilot's understanding of aerodynamics is very poor. I've seen blatant mistakes in flight manuals. At the least you should know how to explain what Reynolds number and Kutta condition are before diving into these discussions.
Several thousand people die every year from drowning every year in the US[1]. That number could be significantly reduced if swimming pools were banned. Swimming pools provide a lot less utility than cars. Do you think swimming pools should be banned?
I don't have the statistic handy, but horses killed far more riders than cars did, even back then. Horses are far more dangerous than cars. They aren't kitty cats. They're big, strong, and sometimes decide they want to kill the rider.
Surely providing electric general aviation is a good idea, assuming that the economics of electric power compared to fossil fuels in general aviation is worth it on both ecological savings (CO2) and operational.
Electric motors are inherently much simpler than internal combusion, but I don't know how they compare to turbofans.
But it's definitely worth the research and working out design and other aspects is a good thing for research in other aviation areas like drones.
> What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement.
But it's pretty obvious that they don't have a problem with lift during cruise, so why does it matter that you lose some lift? I really doubt they would design the wing that narrow if simulations showed that lift was an issue, and I think these guys know what they're doing, so if you think this is an issue I think you need a stronger argument.
That's the whole point of the small propellers, to gain that lift during take-off and landing, while not producing drag during cruise.
> And we know from the Osprey that complex propeller systems fail too often. A dozen propellers means an order of magnitude more inspections, replacements, ground time (AOG), etc.
But we're already seeing from small electric planes entering the market now that they have much lower maintenance and operational costs. Electric motors are fundamentally more reliable and low-maintenance than other alternatives.
So it can make sense to spend some of those saved costs on increasing the complexity a bit to increase efficiency and redundancy.
I also don't agree that this propeller system is complex or would require an order of magnitude more inspections. As mentioned, electric motors are extremely simple and reliable, and the small propellers have a high degree of redundancy, so you could design the system to allow for failure of one or two motors without affecting operations. The folding mechanism for the propellers looks to be very simple.
A way to think about it could be: ensuring that you have high enough safety margins require a certain amount of complexity. You can either spend that complexity on two engines that require a high degree of internal complexity and maintenance, or you spend the complexity on 10 motors that are extremely simple and are allowed to fail.
I also think the comparison with the V22 Osprey is extremely flawed. The purpose of those complex rotors have an entirely different purpose, and it's certainly not for redundancy or efficiency, and the engines have wildly different properties from electric motors.
> Additionally, there is no "urban air mobility market" in the USA, and never will be, due to regulation and insurance requirements.
It's pretty bold to say "there never will be". But anyway, it's just a vision, something to strive for.
What we do know is that it's very likely that electric planes will lead to higher utilisation of small airports. They're cheaper to operate and more silent, which significantly reduces the barrier to using these kinds of airports. At first we'll just see pretty standard looking electric planes in existing small airports, but as this market grows, I think you'll see both the planes and the airports change to optimise for this new/growing market. No, maybe you won't have a flying car in your garage, but I find it very likely that you can drive/bike/walk to something like a bus/train-station to catch a small 10-20 passenger plane somewhere. And though that would be impossible with the regulations today, the regulations will adapt iteratively, allowing the small airports to move closer and closer to urban centres, with shorter and shorter runways.
Aside from the pictures, the article was a bit lacking in information. According to wikipedia, it only seats 2 people, has a maximum range of only 100 miles, and a maximum flight time of only 1 hour. The batteries weigh 390kg, which sounds like a lot of weight relative to the small size of the plane.
I get that electric flight is new, and it's going to take a long time before anything happens at scale, but given the limitations (and of course the fact you need an airstrip at either end of your journey) I can't help but wonder who is going to actually buy them, and what they would do with them?
The X in X-Planes stands for "eXperimental". The history of them goes back within the US to 1946 and as the list [1] of vehicles shows, these aircraft are intended to test concepts and ideas, not provide a sellable solution to the market.
Whilst most are betting that commercial electric in the air is going to be VTOL - and they do address the low endurance and runway issues you highlight - there are efficiency gains for longer distance in fixed wing designs, and you're going to have to think about electrification of that class of vehicle at some point.
Put another way: we don't use helicopters for all passenger transport for a whole bunch of reasons, EVTOLs don't fix all those reasons, and so if you want to keep fixed wing aircraft around as a concept AND you want to use electric motors, at some point you're going to have to think about experimenting with electric passenger-carrying fixed wing aircraft.
Thus: the X-57.
You might wonder what the purpose of an experimental aircraft in this config is, if the eventual goal is to build airliners that can move lots of people.
Well, the X-1 was no Concorde, but Concorde would not have happened without the X-1. And so it goes...
It's OK then to think of the X-57 to an airliner of the future, as the X-1 was to Concorde. It's a whole set of interesting experiments that will validate some hypotheses, refute others, and we move along another step towards a better future.
Seat count will get higher, endurance will improve, batteries will get lighter, and within 20 years, who knows where we'll be.
I do understand this is experimental, but I just assumed the end goal was to do a licensing deal of some sort with a partner than would sell a commercialised variant.
My assumption (yes, another one ;) was that electrification would require baby-steps towards commercialisation in order to continue to fund the kind of progress you speak of - in the same kind of way we saw with cars, where initially they were expensive, had a very short range, there was very limited infrastructure etc, but they were still an option for a small market segment.
From the article, apparently the purpose of the whole program is to immunize FAA of funky startup planes.
With a NASA prior art as baseline, FAA people could judge what document is required, which part is novel and which one of “chief” is just a functional addict.
In our part of the US, money for bike lanes, buses, and rail comes from states and local jurisdictions, not from federal funds. The portion of money NASA is getting from this does not take away from multi-modal transportation investment at the local level.
sure, but it's a common thread. notice how you see similar comments on articles about electric cars. HN hates to see money spent on improving forms of transportation that are not bikes or public transit.
Does anyone have enough aerospace knowledge to comment on the design? Comments on the article seem skeptical on placement of the propellers, but I have absolutely no expertise here to make any assessment myself.
Apparently the small propellers’ primary function is “to act as a high-lift device [1]” rather than to generate thrust.
They allow the wings to have a higher aspect ratio (i.e., be ‘long and skinny’) for reduced drag. Without them, such a wing would give undesirable low-speed handling characteristics and a higher stall speed.
Also, their speed can be varied independently and quickly by computer to compensate for turbulence and wind gusts.
Looks like quite an interesting design that plays to the strengths of electric motors.
The tip propellers reduce losses due to wing tip vortexes. From memory about half the drag from a wing comes from those. So potentially there is some savings there.
The reason no ones built an conventional aircraft with tip props before is because mechanical limits, put a piston engine at the tip the wing and like a big weight on a spring. And losing an engine would mean real problems flying the aircraft.
Electric motors are simple and have a higher power to weight ratio. So probably workable. And electric aircraft reducing drag is really important because of the low energy density of batteries compared to aviation fuel.
There's no better place to put them if your goal is redundancy with lots of small props. Puller props are generally more efficient because they're not in the wake of the wing, but it's a tradeoff and you can Google as for the pros/cons of push vs. pull props. The larger tip props are really interesting. Larger, slower rotors are more efficient. Putting them far outboard puts them in the least-disturbed flow while knocking out the tip vortices. This is only possible with lightweight electric motors vs. shrouded turbines, otherwise the wing/wing box would be quite heavy to support such a long moment arm.
I have no special knowledge myself, but as I understand it, the little propellers along the wing greatly reduce takeoff and landing speed and distance - they basically produce airspeed without groundspeed. Note - this is based on a video I watched one time, if I got this wrong, please educate me.
That's correct, essentially you can apply Newton's law (F = dp/dt): the propellers over wings can produce a strong downward momentum flux (air flux) that by reaction generates lift (upward force). Without this flux being directly controllable by the wings (or steerable in other ways), you need to rely on the vehicle's airspeed to generate sufficient airflow on the wings to produce lift (so you'd expect greater takeoff speed/distance necessary).
You might wonder also about efficiency. Generally the energy efficiency of an aircraft is dictated by 1) friction losses 2) outgoing airstream velocity. The lower the friction and the slower you can push an air stream the more efficient the aircraft ((2) is because the kinetic energy imparted on the air is quadratic on speed, while the momentum, and force, is only linear in speed). That's why high-bypass turbofans are now the norm (more air at slower speeds). And why you want a large propeller surface of low speed (I expect at very large propellers you get diminishing/negative returns due to additional drag), which can be few large props or many smaller props (which have the previously discussed advantages).
Really recommend watching the short video at the end of the article. It shows them fiddling with a 3d-printed prototype of the folding propeller, and some of the CFD analysis of the prop wake - wing interaction.
Problem in the article with the caption? It says the picture is in 'cruise mode' but when cruising at altitude, the X-57 folds the small electric motors into the wing nacelles and leaves only the two wingtip props active. Did I miss something?
With cars, we've seen a lot of companies going the hybrid route, combining multiple small electric motors with a combustion engine. I'm curious if the same could be done with aviation - perhaps a turboprop or jet engine to get to cruise altitude, then electric engines taking over.
Anyone know if there are any promising hybrid planes on the horizon?
Humans need a basic amount of exercise for health. It is hard for me to understand how someone with a functioning brain would look at traffic congestion and propose this solution, particularly with the codicil, "it's already benefiting taxpayers".
No, technological developments that cannot possibly be used by anyone but the wealthy few, no matter how energy-efficient, are not a sane solution to urban transportation issues.
The solutions are more prosaic:
(1) Reduce population, population density, and the product of population times lifestyle. We have exceeded the carrying capacity of the planet, and our science is telling us that unequivocally with a cacophony of data from coral reefs, the status of the ocean, the loss of insects, and many other sources. We must control our own numbers. There is no technological alternative to that.
(2) Create spaces and routes that foster personal human-powered transportation, such as bicycling. Separate the cars from the people to stop the carnage and remove legitimate safety arguments against bicycling.
(3) Make public transit extensive and free. Stop extracting a pound of flesh from the poorest for every ride that they must take to get to a job that doesn't pay a living wage. The inequity of wealth distribution in our society has passed all limits of sanity. Incentive works great in small "c" capitalism, and we need to make sure that mom and pop outfits and very small businesses have the incentive to innovate and produce, but there is no need for the unlimited capitalism that we have now. Take a few pennies out of the pockets of the uber-rich to pay for transit.
(4) Stop the propaganda, herein represented by NASA's usual BS about how we all benefit from their R&D. Organ transplants my fanny. The only thing this kind of transportation is going to do is to further increase the divide between ordinary people and the ultra-rich who pay no taxes in any case. Taxpayer-funded research into new toys for the CEO. Yay.
We are brainwashed into a profligately wasteful, unnecessary, insanely-self-focused lifestyle. Mass media makes us feel bad so we'll go out and spend all our money on the latest stupid thing that will break in a year or less and we'll throw out. All the while we are striving to fill some artificially-stoked hunger for more: more money, more things, more waste and more destruction.
The X-57 feeds right into that brainwashing. It will be our end.
Its actually pointed at reducing the entry cost of flying. So ultimately not for ultra-rich.
NASA spends peanuts, and part of those peanuts is spent on fostering innovation. When I hear "Lets just feed the poor!" I feel ill. We're not so desperate we can't do right by our people, without tearing down everything else that's good. NASA's budget isn't going to feed the poor for more than 10 minutes.
Propeller-driven aircraft perform best at subsonic speeds (slower than the speed of sound). This is because the blade tips of the propellers approach the speed of sound at faster speeds, and this greatly increases the drag on the propeller blades, among other things. This is why after World War 2 propeller-driven fighter craft fell out of use, since they could not get much faster without major issues.
Modern passenger jets operate in the transonic range (0.7 to 0.8 times the speed of sound). This range is a bit too fast for propellers and pretty much requires jet engines or something similar. Using props for passenger planes would reduce their speed as experienced by passengers today. I believe this is what the author is referring to.
NASA did abandon aviation for space, shelving the X-plane program for about 2 decades, which was a huge loss.
It's great they're back, and have been doing fantastic work in fundamental research that private companies don't get around to: hypersonic vehicles, small-airplane electronics, now electric.
I’m all for ambitious research projects pushing the boundaries of electric flight, and there’s probably reasonable use cases for planes like the X-57. But a sustainable urban transport future looks much more like buses and bicycles rather than small electric aircraft.