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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 i

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": https://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey https://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey 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.

TeMPOraL 7y ago
> 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).
- dodobirdlord 7y ago
  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.
- redis_mlc 7y ago
  The FAA doctrine is "one level of safety." What that means is that: 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?
  - jsight 7y ago
    The Robinson R44 costs ~500k USD.
WalterBright 7y ago
If we had the modern regulatory environment 130 years ago, we'd never have had consumer cars.
- ncmncm 7y ago
  And no 30k-50k car deaths / year. Worth it? Biased?
  - verify_sirrah 7y ago
    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? [1] https://www.cdc.gov/homeandrecreationalsafety/water-safety/waterinjuries-factsheet.html- https://www.cdc.gov/homeandrecreationalsafety/water-safety/w...
  - WalterBright 7y ago
    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.
    - megablast 7y ago
      Sure, but we would have moved to public transport. Trams, buses, trains , subway. Saving millions of people a year, and trillions of dollars.
      - ncmncm 7y ago
        Exactly the point. The necessity for car ownership in the US is a monstrous tax collected and paid to car manufacturers and oil companies.
- dTal 7y ago
  An excellent point. Alas, we didn't, and now we're stuck with an awful 19th century local maximum.
friendlybus 7y ago
Judging a regulatory environment for a market that doesn’t exist yet from research craft seems pre-emptive. We’ve had multi engine turbo props forever, I don’t understand why the osprey is more comparable than a traditional propeller aircraft.
audunw 7y ago
> 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.
sunstone 7y ago
Fluid dynamics can be counter intuitive.
rswail 7y ago
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.
bdamm 7y ago
> 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.
starpilot 7y ago
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.

TeMPOraL 7y ago

> 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).

dodobirdlord 7y ago
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.
redis_mlc 7y ago
The FAA doctrine is "one level of safety." What that means is that: 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?
- jsight 7y ago
  The Robinson R44 costs ~500k USD.

WalterBright 7y ago

If we had the modern regulatory environment 130 years ago, we'd never have had consumer cars.

ncmncm 7y ago
And no 30k-50k car deaths / year. Worth it? Biased?
- verify_sirrah 7y ago
  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? [1] https://www.cdc.gov/homeandrecreationalsafety/water-safety/waterinjuries-factsheet.html- https://www.cdc.gov/homeandrecreationalsafety/water-safety/w...
- WalterBright 7y ago
  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.
  - megablast 7y ago
    Sure, but we would have moved to public transport. Trams, buses, trains , subway. Saving millions of people a year, and trillions of dollars.
    - ncmncm 7y ago
      Exactly the point. The necessity for car ownership in the US is a monstrous tax collected and paid to car manufacturers and oil companies.
dTal 7y ago
An excellent point. Alas, we didn't, and now we're stuck with an awful 19th century local maximum.

friendlybus 7y ago

Judging a regulatory environment for a market that doesn’t exist yet from research craft seems pre-emptive. We’ve had multi engine turbo props forever, I don’t understand why the osprey is more comparable than a traditional propeller aircraft.

audunw 7y ago

> 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.

sunstone 7y ago

Fluid dynamics can be counter intuitive.

rswail 7y ago

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.

bdamm 7y ago

> 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.

starpilot 7y ago

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.