Lilium – Electric vertical take-⁠off and landing jet

Re:Lilium – Electric vertical take-⁠off and landing jet by aphextron on Friday April 21, 2017 @04:12PM (#14169028)

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.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by jacquesm on Friday April 21, 2017 @04:17PM (#14169061)

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.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Friday April 21, 2017 @04:19PM (#14169086)

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.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by aphextron on Friday April 21, 2017 @04:29PM (#14169148)

> Just putting electric motors in current generation airframes would cut costs ten-fold.

Absolutely. I didn't mean to disparage the idea of an electric drivetrain for aircraft in general. Check out Pipistrel (https://www.youtube.com/watch?v=WiADDbeFanU) they're doing some incredible things right now. They have a LiPo powered twin seat LSA trainer in production that gets an hour of flight time at 80 knots and 600lb useful load with hotswap batteries. This is the future of trainers IMO.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by markvdb on Friday April 21, 2017 @06:27PM (#14169915)

Please use SI units: 150 km/h speed, 300kg useful load.

Thank you for the Pipistrel link!

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Friday April 21, 2017 @06:36PM (#14169961)

Aviation units/specifications are unfortunately almost always specified in knots and pounds.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by nradov on Friday April 21, 2017 @04:51PM (#14169340)

A liquid-hydrocarbon fueled turbogenerator would appear to meet your criteria. You can use synthetic or biofuels if you're worried about the environmental impact. Of course the aircraft will be more efficient if you omit the generator and mechanically couple the turbine to the props.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Friday April 21, 2017 @05:23PM (#14169535)

I talk about this elsewhere in this section. Pipistrel tried this on the Panthera and the system complexity is enormous. The whole advantage of electric propulsion is it's simplicity. Might as well just use the turbine for lift.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by nradov on Saturday April 22, 2017 @06:01AM (#14171805)

Yes that was exactly my point. Barring major advances in battery technology, if you want to build a powered lift VTOL aircraft safe enough for civilian passengers with useful range and payload then you probably need to use a turbine engine. Batteries just aren't good enough yet.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by blueprint on Friday April 21, 2017 @05:27PM (#14169562)

Why energy density storage and not wireless power transmission and/or reception?

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Friday April 21, 2017 @05:33PM (#14169594)

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).

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by FabHK on Friday April 21, 2017 @11:38PM (#14171001)

I thought a fixed wing or even heli/drone type aircraft for one, two pax could fly with, say, 50 kW?

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by sathackr on Saturday April 22, 2017 @11:17AM (#14172926)

50kw is still an incredible amount of power to transmit wirelessly without cooking the target and anything that may pass between the power transmitter and the target. Go put an egg in your microwave and watch what 1kw does to it.

It would also almost certainly require line of sight and a directional antenna that can track the aircraft. Batteries could be used in the aircraft to at least land safely if there were a loss in power.

But currently we have trouble transmitting 5 watts across the 7mm gap between a wireless charger and a phone. 50kw over a distance of 1-300km is a very long way away.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by FabHK on Saturday April 22, 2017 @12:05PM (#14173140)

Thanks. (Note that I think the wireless transmission idea is entirely fanciful and can safely be discarded for the foreseeable future. Just got hung up on the 100 kW figure...)

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by sathackr on Saturday April 22, 2017 @12:44PM (#14173338)

It may need 100kw during certain phases of flight --take off and landing for a VTOL craft, or just take-off for a standard aircraft. Cruise power is generally far less than take off/hover power.

If the craft were entirely wirelessly powered, then of course the system would have to be able to transfer 100kw. But the link(if even 50kw were ever feasible) could be designed for a lower power level, and the aircraft could draw from an onboard battery bank for extra power during these phases of flight.

Kind of like how hybrid drive vehicles undersize the internal combustion engine and then draw power from the ICE and the electric system during heavy acceleration.

But we still need to find a reasonable way to wirelessly transmit large amounts of power safely and efficiently.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Sunday April 23, 2017 @02:08PM (#14179438)

100kW is the likely cruise power for that aircraft at 300kmph. It's likely many times that for VTOL

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by sathackr on Sunday April 23, 2017 @06:18PM (#14180729)

Very possibly. I'm by no means an aerospace engineer.

A quick google turned up this[1] which has a top speed of 296km/h with a 120hp(89kw) engine, and it's likely a good bit lighter than the Lilium with a full battery load.

[1] http://www.aircraftspruce.com/catalog/kitspages/nexaer.php

edit: added [1]

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by the_jaded_one on Saturday April 29, 2017 @10:40AM (#14226777)

I'm surprised they didn't include an internal combustion engine in it to charge the battery. That's the solution for the terrafugia tf-x. https://www.terrafugia.com/tf-x/

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by stcredzero on Friday April 21, 2017 @04:40PM (#14169261)

Any aerospace engineering grad could design a flying car tomorrow if the energy source existed in such a density that would make it feasible.

Beamed power?

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by andars on Friday April 21, 2017 @04:47PM (#14169313)

Maybe, but unlikely. Lasers need line of sight and would generally be a bad idea at the power levels required (basically a weapon), and microwave power transmission requires large receiving apertures. Current "wireless charging" technologies are pretty much universally near field.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by nradov on Friday April 21, 2017 @04:46PM (#14169308)

Impossible for safety reasons in populated areas. And even ignoring safety issues, the conversion efficiency on beamed power is so low as to make it uneconomical.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by stcredzero on Friday April 21, 2017 @05:09PM (#14169446)

I thought the conversion efficiency for microwaves was 80%.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by nradov on Friday April 21, 2017 @05:40PM (#14169641)

Maybe in a kitchen microwave oven. You're not accounting for transmission path losses and receiver conversion efficiency.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by stcredzero on Friday April 21, 2017 @08:04PM (#14170394)

Actually, I think that's a figure including transmission and receiver conversion efficiency, but it doesn't include path losses. That's still quite impressive, though.

http://spectrum.ieee.org/energywise/green-tech/solar/japan-d...

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by nradov on Friday April 21, 2017 @09:39PM (#14170689)

That's for short range transmission to a fixed receiver. So not really relevant for powering aircraft.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by stcredzero on Saturday April 22, 2017 @10:18PM (#14176085)

Such microwave systems have been proposed for solar power satellites. They have useful ranges up to 100's of miles.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by pdelbarba on Friday April 21, 2017 @05:24PM (#14169547)

How would this work through clouds? The water vapor would in theory block or scatter everything from UV to microwave radiation. Also, I don't want to be near a 1W laser/maser, and if our energy budget is 100kW, you'd need at least a 100,000W laser pointed at your tiny air taxi.

[ Parent | on HN ]

Re:Lilium – Electric vertical take-⁠off and landing jet by jacquesm on Friday April 21, 2017 @06:28PM (#14169923)

That's called target practice.

These guys do it all the time:

https://www.youtube.com/watch?v=JtxwT6PQIw8

[ Parent | on HN ]