12 ms·

I'm calling bullshit. See my calculations in the other thread. ~1600lbs of batteries to hit their specs with current tech and that's VERY generous. Likely cl

I'm calling bullshit. See my calculations in the other thread. ~1600lbs of batteries to hit their specs with current tech and that's VERY generous. Likely closer to 2k. Lipo capacity going up at 5% a year so 2025 isn't happening unless new battery tech is announced and commercialized in the next 8 years. Also, steering appears to be entirely based on differential thrust. Power loss = uncontrolled descent. Good luck getting that certified...

joshuahaglund 10y ago
I'm not a pilot, but the fan pods are flaps, so I think there's some steering there. Also, it has a full aircraft parachute as a last resort.
- pdelbarba 10y ago
  Air frame parachutes are great at high altitude but under ~500ft (where you're going to have the highest load on your electrical system during landing/takeoff) they do absolutely nothing. As far as the flaps, they are not sufficient for controlled flight. Increasing the angle of one of them increases both lift and drag on that wing so you have at best a dutch roll/adverse yaw and at worst a flat spin.
- Jtsummers 10y ago
  https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch11.pdf https://www.faa.gov/regulations_policies/handbooks_manuals/a... Helicopters, as opposed to this vehicle, have the ability to be controlled even when power is lost. This is a much safer failure mode for personal aircraft then depending on a chute: useless at altitudes high enough to be fatal but low enough to result in a failed chute deployment. Similarly, winged aircraft can glide, where this one cannot, given enough forward velocity. This thing will drop like a rock in an incidence of power failure at low altitude and the operator will have no way to control where it hits the ground (for either their safety or the safety of those on the ground).
aphextron 10y ago
That's why this is so frustrating. It seems like everyone is just missing the point. Flying cars are not a mechanical design problem. We have the tools, engines, designs, etc. all nailed down at this point. Any aerospace engineering grad could design a flying car tomorrow if the energy source existed in such a density that would make it feasible. It is fundamentally an energy problem, not a mechanical one. Maneuvering around that fact, and spending time on problems that aren't solving the core issue of battery technology is a massive waste of resources.
- jacquesm 10y ago
  Yes, and it always has been. From the Moller Sky car to the Lilium here, making the craft is the easy bit (well, apart from the thrust vectoring but with modern computers that's solvable). Getting it to run for more than 2 minutes with a realistic load is the hard part. Those small ducted fans are horribly inefficient by the way, a regular shaped plane with a pusher prop and the wingspan of a glider would have a much better chance achieving the range (but no VTOL). Too good to be true usually isn't true.
- pdelbarba 10y ago
  Thank you, my thoughts exactly. We need to be focusing on high density energy storage. An electricity source with a similar or greater specific energy to gasoline would transform transportation to the point of being unrecognizable within a couple years. It would be as much of a singularity as AI, high temp super conductors or low cost graphene. Just putting electric motors in current generation airframes would cut costs ten-fold.
  - blueprint 10y ago
    Why energy density storage and not wireless power transmission and/or reception?
    - pdelbarba 10y ago
      Sure, it's possible, but it's a much longer way off at the moment. There are all sorts of technical problems that need to be solved in that space for it to be viable. You need to be able to transmit in excess of 100kW through clouds without any dispersal and not set the target on fire. We at least have the groundwork laid for potentially very high capacity batteries (LiAir, LiS, etc).
stcredzero 10y ago
Lipo capacity going up at 5% a year so 2025 isn't happening unless new battery tech is announced and commercialized in the next 8 years. What about a small fuel/turbogenerator drop pod for just the takeoff/climb?
- pdelbarba 10y ago
  Pipistrel was trying to do this (along with a few other companies). At that point, the mechanical complexity is prohibitive along with the insane operating costs. You still need enough batteries to get back on the ground if something fails but you have the added weight of a combustion engine and it's fuel as well. The whole appeal of electric motors is that they are basically solid state. You don't need to change oil or perform a ton of regular maintenance. Just replace bearings every few years if ever and you're good to go. Gas/jet engines need to be overhauled regularly which contributes a large portion of the operating costs. For instance, a Cessna 172R/SP uses a 180 hp I/O-360 engine that needs to be overhauled (completely disassembled) every 4000 hours at a cost of around $20,000. That's $5 an hour just for the engine replacement assuming no excessive wear or metal flakes in the oil are found.
  - stcredzero 10y ago
    you have the added weight of a combustion engine and it's fuel as well Note I said drop pod. The whole appeal of electric motors is that they are basically solid state. I think beamed power has a lot of potential for electric jets. It's sort of magic. You get to ditch the heavy fuel tanks/batteries, and you still get the benefits of low maintenance costs for electric motors.
    - pdelbarba 10y ago
      Even still, you would need to have the thrust to lift it in addition to your regular operating equipment and some way for it to be recovered (more weight, complexity, operating and upfront cost) I'll pass on sitting in the tiny plane with a 100kw laser pointed at it.
Robotbeat 10y ago
Range is helped A LOT by good lift to drag. In fact, range is proportional to lift to drag. A quadcopter cannot get very good range, but add wings, and you all of a sudden can go places. 300km is probably optimistic for this prototype. Wings are pretty short. But with extremely good lift to drag ratio (as seen in gliders, the best of which can get over 70 lift to drag), you could definitely get even 1000km range even with existing battery tech. Range = (ratio of battery mass used for horizontal flight to total mass) * (lift to drag ratio) * (efficiency of propulsion system) * (specific energy of batteries)/(acceleration due to gravity) So, if cruise-batteries are 0.5 of the total mass, lift to drag is 50, propulsion system is 0.75 efficient (75%), battery specific energy is 1MJ/kg (or 10^6 m^2/s^2 in alternate units, about 300Wh/kg, as good as very best lab-scale lithium ion batteries... lithium-sulfur is better), and gravity is 10m/s^2 (rounded), you have a range of: 0.5 * 50 * .75 * 1(MJ/kg)/(10m/s^2) = 0.5 * 50 * .75 * 10^6(m^2/s^2)/(10m/s^2) = 1875km. Of course, 50% useful cruise battery weight is probably optimistic (although not too different from long distance airliners whose take-off mass can be roughly half fuel) and a lot of weight will be needed for the vertical take off and landing motors plus the payload, but it does show you what's possible even with existing battery tech. I tend to think the prototype they showed probably won't get 300km range. Probably need longer wings for that. But their eventual goal is achievable. By the way, for long range, they're not likely using LiPo but lithium ion, perhaps those ubiquitous 18650 cells that Panasonic makes (of Tesla fame). And greater range is possible, especially as lithium-sulfur batteries start becoming more widely available (to speak nothing of lithium air). As far as losing power to an engine, well, there are lots of engines. Also, electric motors and batteries are very simple and can be built to have extremely high reliability. The batteries and propulsion system can be built to be totally distributed, in which case there's really no feasible scenario where power is lost (unless control is lost, in which case you'd be screwed in a conventional airplane or helicopter, too). Additionally, a ballistic parachute can be and is used. I don't think this flight is a breakthrough. A decent team could do the same thing they just did, and lots of people (including at NASA Langley) have been working on the same goal. Teaming a bunch of electric motors capable of tilting is a thing that several groups are pursuing, lots of people have done at smaller scale already, and it's only a matter of time before it's done at a large scale as well.
- pdelbarba 10y ago

joshuahaglund 10y ago

I'm not a pilot, but the fan pods are flaps, so I think there's some steering there. Also, it has a full aircraft parachute as a last resort.

pdelbarba 10y ago
Air frame parachutes are great at high altitude but under ~500ft (where you're going to have the highest load on your electrical system during landing/takeoff) they do absolutely nothing. As far as the flaps, they are not sufficient for controlled flight. Increasing the angle of one of them increases both lift and drag on that wing so you have at best a dutch roll/adverse yaw and at worst a flat spin.
Jtsummers 10y ago
https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch11.pdf https://www.faa.gov/regulations_policies/handbooks_manuals/a... Helicopters, as opposed to this vehicle, have the ability to be controlled even when power is lost. This is a much safer failure mode for personal aircraft then depending on a chute: useless at altitudes high enough to be fatal but low enough to result in a failed chute deployment. Similarly, winged aircraft can glide, where this one cannot, given enough forward velocity. This thing will drop like a rock in an incidence of power failure at low altitude and the operator will have no way to control where it hits the ground (for either their safety or the safety of those on the ground).

aphextron 10y ago

That's why this is so frustrating. It seems like everyone is just missing the point. Flying cars are not a mechanical design problem. We have the tools, engines, designs, etc. all nailed down at this point. Any aerospace engineering grad could design a flying car tomorrow if the energy source existed in such a density that would make it feasible. It is fundamentally an energy problem, not a mechanical one. Maneuvering around that fact, and spending time on problems that aren't solving the core issue of battery technology is a massive waste of resources.

jacquesm 10y ago
Yes, and it always has been. From the Moller Sky car to the Lilium here, making the craft is the easy bit (well, apart from the thrust vectoring but with modern computers that's solvable). Getting it to run for more than 2 minutes with a realistic load is the hard part. Those small ducted fans are horribly inefficient by the way, a regular shaped plane with a pusher prop and the wingspan of a glider would have a much better chance achieving the range (but no VTOL). Too good to be true usually isn't true.
pdelbarba 10y ago
Thank you, my thoughts exactly. We need to be focusing on high density energy storage. An electricity source with a similar or greater specific energy to gasoline would transform transportation to the point of being unrecognizable within a couple years. It would be as much of a singularity as AI, high temp super conductors or low cost graphene. Just putting electric motors in current generation airframes would cut costs ten-fold.
- blueprint 10y ago
  Why energy density storage and not wireless power transmission and/or reception?
  - pdelbarba 10y ago
    Sure, it's possible, but it's a much longer way off at the moment. There are all sorts of technical problems that need to be solved in that space for it to be viable. You need to be able to transmit in excess of 100kW through clouds without any dispersal and not set the target on fire. We at least have the groundwork laid for potentially very high capacity batteries (LiAir, LiS, etc).

stcredzero 10y ago

Lipo capacity going up at 5% a year so 2025 isn't happening unless new battery tech is announced and commercialized in the next 8 years. What about a small fuel/turbogenerator drop pod for just the takeoff/climb?

pdelbarba 10y ago
Pipistrel was trying to do this (along with a few other companies). At that point, the mechanical complexity is prohibitive along with the insane operating costs. You still need enough batteries to get back on the ground if something fails but you have the added weight of a combustion engine and it's fuel as well. The whole appeal of electric motors is that they are basically solid state. You don't need to change oil or perform a ton of regular maintenance. Just replace bearings every few years if ever and you're good to go. Gas/jet engines need to be overhauled regularly which contributes a large portion of the operating costs. For instance, a Cessna 172R/SP uses a 180 hp I/O-360 engine that needs to be overhauled (completely disassembled) every 4000 hours at a cost of around $20,000. That's $5 an hour just for the engine replacement assuming no excessive wear or metal flakes in the oil are found.
- stcredzero 10y ago
  you have the added weight of a combustion engine and it's fuel as well Note I said drop pod. The whole appeal of electric motors is that they are basically solid state. I think beamed power has a lot of potential for electric jets. It's sort of magic. You get to ditch the heavy fuel tanks/batteries, and you still get the benefits of low maintenance costs for electric motors.
  - pdelbarba 10y ago
    Even still, you would need to have the thrust to lift it in addition to your regular operating equipment and some way for it to be recovered (more weight, complexity, operating and upfront cost) I'll pass on sitting in the tiny plane with a 100kw laser pointed at it.

Robotbeat 10y ago

Range is helped A LOT by good lift to drag. In fact, range is proportional to lift to drag. A quadcopter cannot get very good range, but add wings, and you all of a sudden can go places. 300km is probably optimistic for this prototype. Wings are pretty short. But with extremely good lift to drag ratio (as seen in gliders, the best of which can get over 70 lift to drag), you could definitely get even 1000km range even with existing battery tech. Range = (ratio of battery mass used for horizontal flight to total mass) * (lift to drag ratio) * (efficiency of propulsion system) * (specific energy of batteries)/(acceleration due to gravity) So, if cruise-batteries are 0.5 of the total mass, lift to drag is 50, propulsion system is 0.75 efficient (75%), battery specific energy is 1MJ/kg (or 10^6 m^2/s^2 in alternate units, about 300Wh/kg, as good as very best lab-scale lithium ion batteries... lithium-sulfur is better), and gravity is 10m/s^2 (rounded), you have a range of: 0.5 * 50 * .75 * 1(MJ/kg)/(10m/s^2) = 0.5 * 50 * .75 * 10^6(m^2/s^2)/(10m/s^2) = 1875km. Of course, 50% useful cruise battery weight is probably optimistic (although not too different from long distance airliners whose take-off mass can be roughly half fuel) and a lot of weight will be needed for the vertical take off and landing motors plus the payload, but it does show you what's possible even with existing battery tech. I tend to think the prototype they showed probably won't get 300km range. Probably need longer wings for that. But their eventual goal is achievable. By the way, for long range, they're not likely using LiPo but lithium ion, perhaps those ubiquitous 18650 cells that Panasonic makes (of Tesla fame). And greater range is possible, especially as lithium-sulfur batteries start becoming more widely available (to speak nothing of lithium air). As far as losing power to an engine, well, there are lots of engines. Also, electric motors and batteries are very simple and can be built to have extremely high reliability. The batteries and propulsion system can be built to be totally distributed, in which case there's really no feasible scenario where power is lost (unless control is lost, in which case you'd be screwed in a conventional airplane or helicopter, too). Additionally, a ballistic parachute can be and is used. I don't think this flight is a breakthrough. A decent team could do the same thing they just did, and lots of people (including at NASA Langley) have been working on the same goal. Teaming a bunch of electric motors capable of tilting is a thing that several groups are pursuing, lots of people have done at smaller scale already, and it's only a matter of time before it's done at a large scale as well.

pdelbarba 10y ago