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#26 2019-11-11 12:30:19

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

Rounding up the content that was copied in supercaps..
1 quick charging and possible discharge
2 1/3 the mass of a comparible lithium battery
3 flexible cap arrangement to make variable time of use

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#27 2019-11-11 14:45:34

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 703

Re: Autonomous Passenger Carrying Electric Aircraft

Lithium ion batteries have energy density of 1MJ/kg.  Jet fuel has an energy density of 43MJ/kg.  DC electric motors have a peak efficiency of about 80%.  High bypass turbofans have efficiency of about 33%.  So 1kg of jet fuel yields almost 18x as much work energy as 1kg of batteries.  And a jet fuel powered plane gets lighter as it consumes fuel.

Certainly a poor energy source for a flying machine in which range is proportional to energy per unit weight.  Hydrogen or liquefied natural gas would be far more efficient fuels, at least at the point of use.


Interested in space science, engineering and technology.

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#28 2019-11-11 15:36:33

tahanson43206
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Posts: 5,043

Re: Autonomous Passenger Carrying Electric Aircraft

For Calliban re #27

I apologize for bringing into the topic a quote that (apparently) does not use the same units as you have.

However, I'm wondering how supercapacitors compare to lithium ion batteries AND to jet fuel for energy per kg. 

As for the business argument you have introduced .... cost of jet fuel is not the only cost consideration for a transportation company.  Cost of maintenance of complex mechanical systems is a factor, as is the necessity to maintain the infrastructure to supply jet fuel at the airport.

My guess is that a business investor may be interested in looking at destinations where industrial scale power is available, but where jet fuel may not be.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6409971/

Abstract
Present state-of-the-art graphene-based electrodes for supercapacitors remain far from commercial requirements in terms of high energy density. The realization of high energy supercapacitor electrodes remains challenging, because graphene-based electrode materials are synthesized by the chemical modification of graphene. The modified graphene electrodes have lower electrical conductivity than ideal graphene, and limited electrochemically active surface areas due to restacking, which hinders the access of electrolyte ions, resulting in a low energy density. In order to solve the issue of restacking and low electrical conductivity, we introduce thiol-functionalized, nitrogen-doped, reduced graphene oxide scrolls as the electrode materials for an electric double-layer supercapacitor. The fabricated supercapacitor exhibits a very high energy/power density of 206 Wh/kg (59.74 Wh/L)/496 W/kg at a current density of 0.25 A/g, and a high power/energy density of 32 kW/kg (9.8 kW/L)/9.58 Wh/kg at a current density of 50 A/g; it also operates in a voltage range of 0~4 V with excellent cyclic stability of more than 20,000 cycles. By suitably combining the scroll-based electrode and electrolyte material, this study presents a strategy for electrode design for next-generation energy storage devices with high energy density without compromising the power density.

(th)

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#29 2019-11-11 16:00:51

SpaceNut
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From: New Hampshire
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Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

If flights are often and you charge quickly then you are beating the use of batteries. The batteries do not like the temperatures caused internally within them for fast charging. The motors while they lack the effiecency is not the total picture as its the current draw for rpm that matters for flight. Meaning slower rpm for flight gliding (lower current draw) while higher is for quicker motion to destination ramping up the current needed to make it spin faster.

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#30 2019-11-13 17:05:30

SpaceNut
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From: New Hampshire
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Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

A very large repost but relates totally for thie topic:

kbd512 wrote:

tahanson43206,

The most advanced super capacitors in commercial production have energy density (specific energy) in line with Lead-acid batteries.  However, these are still pretty expensive and applications remain limited.  Tesla Motors Corp purchased Maxwell for this technology.  Some dev lab 3D super cap technology has reached energy densities as high as 110Wh/kg, or a little less than half of what a commercial Lithium-ion battery can store.  It's an interesting technology for providing bursts of power for very brief periods of acceleration for motor vehicle applications, but not so interesting for powered flight applications which have high constant power requirements.  Trying to power any type of aircraft with Lead-acid batteries isn't very practical.

Super capacitors are capable of dumping stored energy at rates that would destroy Lithium-ion batteries.  A super capacitor bank is a good way to put less wear and tear on a Lithium-ion battery bank from very high discharge rates (for a battery) associated with very brief periods of acceleration measured in seconds.  The battery only has to recharge the capacitor bank and maintain a comparatively minor constant output level to move the vehicle at highway speeds (10hp to 20hp for most passenger vehicles in the 1t to 3t range).  So long as ranges of hundreds of miles are not required, you can make a battery powered motor vehicle lighter and cheaper because you don't need extra battery capacity just to deal with high discharge rates.  The same concept would apply to combustion engine vehicles.  If a vehicle was powered by a combination of super capacitors and a piston engine powering a generator, then a very low displacement engine combined with a super capacitor bank would be sufficient to accelerate the vehicle acceptably well and run it at highway speeds without requiring additional engine power for acceleration.  A free piston engine with a super capacitor bank would be ideal, I would think.

In powered flight applications that use aerodynamic lift to remain airborne, weight is what matters most, followed rather closely and synergistically by aerodynamics.  In short, weight affects power requirements through aerodynamics.  You have to produce sufficient power to propel the wing and everything attached to it through the air fast enough to produce the "up force" required to keep some specific amount of weight airborne at some specific speed.  The power requirement doesn't linearly increase with increasing speed, either.  That's why you design an aircraft to cruise at some optimum speed, with a given load, to a given distance.

The only way to meaningfully improve performance is to increase power, decrease weight, or improve aerodynamics- dependent upon what you're trying to accomplish.  Most aircraft designers do pay attention to the drag generated by their airframe design and try to minimize it for a particular cruising speed.  It's a balancing act to manage the inverse relationship between induced and parasitic drag to minimize total drag for a design cruise speed.  If you want more speed, then you need more power.  That means you need a bigger and heavier engine that consumes more fuel.  You'll need a heavier airframe attached to that bigger engine and bigger gas tanks carrying more gas.  Whether the "gas" is gasoline, kerosene, diesel, methane, hydrogen, or electrons stored in a battery or capacitor is irrelevant to the design goal of "going faster".  You're going to consume more of "it" to go faster.  Period.  If the fuel is electrons wirelessly transmitted via microwave, that's the only practical way I know of to offload the weight of the "gas" and gas tank.  It's going to be a compromise (prioritization) of some kind.

To actually get some specific mass airborne using aerodynamic lift, you must accelerate the wing (and everything attached to it, obviously) fast enough to fly before you run out of available runway, with performance margin to spare.  As a result, you'll briefly need to generate some multiple of the amount of power minimally required to simply remain airborne in level flight.  There's obviously a limit to this, since aircraft can take off vertically when thrust is greater than weight.  Generating that kind of power leads to very heavy engines with very high fuel consumption.  There's no such thing as a helicopter that's more fuel efficient than a fixed wing aircraft carrying equivalent payload to equivalent distance at equivalent speed, for example.

To overcome drag to fly significantly faster without a dramatic increase in power, it's certainly possible to attach tiny wings that only produce sufficient lift to get airborne at high speeds.  However, that typically results in unmanageable takeoff and landing speeds that would impart very high forces into the airframe from all but the most perfect landings.  That would then mandate a very robust design which requires more structural weight to achieve, which then requires more wing to lift it, which then requires more power to push the craft through the air.

Now that we understand why it is that aircraft power plants must be lightweight and consume energy stores with very high energy densities per unit of weight, let's consider the use of an energy store with half of the performance of current Lithium-ion batteries.  In practice, we're going to drastically reduce payload or range or speed, or likely all three, by using a very low energy density storage technology.  Alternatively, we're going to drastically increase the size and weight of any solution competitive with a gas or kerosene engine, and therefore cost.  The energy density issue is an intractable problem, as it pertains to powered flight.  However, if we're willing to trade speed for total delivered tonnage for a given fuel burn, there are certainly practical alternatives to gas turbines and high fuel burns, principally by using a lifting gas to negate part of the power requirement simply to remain aloft.

Modern transport airships are also designed to use aerodynamic lift to remain airborne.  To aid controllability in flight, these airships are slightly heavier than air.  They use speed to vary the amount of lift generated by the inflatable structure to ascend or descend, just like conventional fixed wing aircraft.  The power requirements are lower per unit of mass since less lift is required and lower speeds are involved.  However, moving weight around at highway speeds (60mph to 120mph) and pushing all of that air out of the way still requires a certain amount of power.  The volume of air being displaced by a large cargo transport will closely resemble that associated with an aircraft carrier, so the power requirement is still non-trivial.  Lockheed-Martin designed a cargo airship to use a type of "inflatable suction cup" (reverse hovercraft technology) to glue the blimp to the ground for cargo loading / offloading, negating the need for any sort of specialized ground equipment for cargo transfer.

There are 3 practical applications I see for this technology:

1. Faster commercial cargo transport with less energy consumption than jet aircraft and therefore cost.  An airship will be significantly faster than ocean-going cargo ships while consuming less fuel to achieve the same range with a given payload than a traditional jet airliner.

No dredged shipping channels or docks equipped with gigantic cargo offload cranes are required, so a simple concrete slab with forklifts and CONEX box cranes is all that's required to offload cargo.  The infrastructure and embodied energy cost, since it takes energy and money to mine ore, smelt steel, machine the steel into complex cargo transfer equipment, transport it to the dock site and maintenance costs for all of that stuff are drastically reduced.

Fewer crew are required to man airships, perhaps just 2 to 4 pilots, no different than other commercial aircraft.  To ferry cargo across the Atlantic, from New York to London, the Airlander 10's 90mph cruising speed would equate to a 38 hour flight.  The Airlander 50's projected to have a faster cruising speed of 120mph, so that's a 29 hour flight.  The more economical alternative is a 6 to 12 day journey by cargo ship.  That may not matter for furniture or raw materials, but it matters greatly for food / medicine / aircraft parts.  A Boeing 747 can complete the same journey in 6 hours, but with a 22,000 gallon fuel burn.  The Airliner 50 would burn around a quarter as much fuel to deliver the same tonnage of cargo the same distance.

2. The "Knarr" concept, which uses a solar panel and regenerative fuel cells, wouldn't "burn" any fuel that couldn't be recycled, so the fuel consumption and thus cost drops to near zero.  It's larger than our largest aircraft carriers, but also carries 1,000t of cargo at roughly the same speed as the Airlander 50.  The Knarr only requires 5,600hp to do that.  It's covered with 63,000m^2 worth of thin film solar panels to generate around 12MW of power at noon.  To put this in perspective, our Osprey tilt rotor aircraft are equipped with a pair of 6,150shp Rolls Royce T406 gas turbines.  The Osprey's maximum vertical takeoff weight is 24t.  So, Knarr's cargo capacity is equivalent to 41 Osprey's loaded with gas and cargo to their maximum vertical takeoff weight.  If it's not obvious, helicopters really suck at energy efficiency when compared to fixed wing aircraft or blimps, though they still have their uses.

A single Knarr could deploy a full strength US Armored Company (M1 Abrams MBT's) per flight.  Two squadrons of Knarr's could deploy a full strength US Armored Division (again, our MBT's, not lighter APC's / IFV's) to Europe in approximately 2 days, and we could skip the railhead and pier side RORO operations entirely, so everything would arrive in theater much faster than rail / shipping operations.

3. Airships could act as sky cranes to deliver cargo that would be impractical to deliver by other methods, such as gigantic wind turbine blades and materials for skyscrapers.  Affordable high capacity vertical lift would be an enabling technology for building all sorts of structures.  Cranes would still have their uses.  However, if we were building mile-high skyscrapers, then it'd be a whole lot easier to lower materials to workers waiting below than it would be to hoist them from the ground using cranes with the mass and support structure required to prevent them from toppling over.  There's going to be some kind of practical limit on everything.

So...  Super caps for airships in the immediate future?  Maybe, maybe not.  Perhaps only for take-off power.  Giant airships for cargo transport?  That'd definitely fulfill an actual "need" use case.  Airships are likely more expensive to operate than ocean going cargo ships, but much faster and a lot less expensive to operate than a jet aircraft.  Airships are the only type of aircraft that could make practical use of solar power, since all other forms of powered flight require far more power in a more compact package.  Over time, the use of solar panels and fuel cells to lower fuel costs could lead to justification for "air mailing" nearly everything but raw materials and fuels, especially since the airship can go just about anywhere big enough for it to take off and land without any specialized support infrastructure.  Time is still money in business, so we're unlikely to see airships providing passenger service.  Luxury cruise liners might be an exception to that rule.  The US military would immediately benefit from airships, given the total tonnage of stuff they have to move half way around the world.  Disaster relief would greatly benefit from high capacity vertical lift and no requirement for functional airfields, and perhaps not even a place to land.

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#31 2019-11-16 06:41:02

tahanson43206
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Registered: 2018-04-27
Posts: 5,043

Re: Autonomous Passenger Carrying Electric Aircraft

For SpaceNut ...

Here's an update for this topic ... the only mismatch is that (at this point) the aircraft in design/development are NOT autonomous.

However, the company seems worth watching because it is backed by a large corporation (apparently) with deep pockets.

https://www.yahoo.com/finance/news/magn … 40816.html

(th)

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#32 2019-11-17 21:35:57

SpaceNut
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Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

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#33 2020-02-21 22:21:03

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

Here is a step in the direction of non polluting BAE_successfully_tests_solar_powered_high_altitude_plane

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#34 2020-06-02 20:16:21

SpaceNut
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From: New Hampshire
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Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

Battery powered plane makes first flight with 750hp electric motor at 100mph and altitude of 2500 ft making a 24 minute loop before landing.

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#35 2020-09-16 18:33:34

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

This fits here as well

tahanson43206 wrote:

Here is a report that could fit into several topics.

It is starting out here because it is an application of fuel cell technology for regional aircraft.

https://currently.att.yahoo.com/finance … 10790.html

kbd512 in particular comes to mind as a member who has been reporting (to the forum) on this technology frequently.

(th)

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#36 2020-09-27 15:47:07

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

As much as we want a flying car how about a drone?

https://www.msn.com/en-us/money/markets … li=BBnbfcL

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#37 2020-09-28 15:23:26

kbd512
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Registered: 2015-01-02
Posts: 4,018

Re: Autonomous Passenger Carrying Electric Aircraft

SpaceNut,

If you have half a million dollars to blow on a personal aerial transport, then you can afford to purchase a real helicopter and obtain a real pilot's license.  The moment these things start falling out of the sky due to software glitches or defective components, we're going to see them regulated by the FAA in the same way that certificated helicopters are regulated because society won't tolerate thousands of vehicles the size and weight of light duty trucks falling out of the sky onto homes and businesses because their owner-operators don't know how to fly or maintain them.  The more you learn, the more you realize that you need to know even more than you already do.  A Robinson R22 costs $250K to $350K brand new and a used machine in good condition costs around $100K.  Why you would ever pay $500K for a machine with a fraction of the R22's range and speed is beyond my comprehension, but fools and their money are easily separated.

Here's a thought, though.  If you want to fly, then spend the $10K to $20K to get a pilot's license and enjoy your expensive hobby.  Buying a private jet doesn't make you a jet pilot, but that's exactly what you'll become if your pilot keels over.  Knowing how to actually inspect / fly / maintain your whirly bird, navigate through weather, communicate with ATC, and deconflict with other traffic is what they teach you in flight school.  You can learn how to fly before or during an in-flight emergency, but simple survival favors the trained and experienced.  I guess I simply don't understand this desire to fly a helicopter, but not actually learn how to fly a helicopter.

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#38 2020-09-28 17:22:06

tahanson43206
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Posts: 5,043

Re: Autonomous Passenger Carrying Electric Aircraft

For kbd512 re #37

First, this post is not questioning the position you've taken .... For someone wanting to fly, I don't see any alternative to the course you've suggested.  It's a lot of work, and it takes time, but the result is a lifelong skill and many hours of heightened alertness as a trained pilot prepares mentally for any emergency that might arise.

That said, I think there is a very specific, and (most likely) lucrative market niche for the kind of vehicle this appears to be ....

Travel from the top of one building in a major global city, to the top of another nearby such building, would be an admirable application of this concept.

Customers for this service would (most likely) have no interest in learning how to fly, any more than an Uber customer wants to learn how to drive a car in an unfamiliar city, or at all in many cases.

The $500,000 investment would be made by a travel service, and if the equipment is kept in service at a level sufficient to pay back the loan and keep up with maintenance services, whatever is left over is a return to the investor.

(th)

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#39 2020-09-28 19:24:15

kbd512
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Re: Autonomous Passenger Carrying Electric Aircraft

tahanson43206,

All aircraft used for commercial purposes must meet FAA regulations for certificated aircraft of whatever type they're classified as, especially those that carry passengers.  If the machine itself is a $500K purchase, then unless there's a night and day difference in maintenance costs, that's what will end up costing the most money.  The greatly reduced fuel bill is fantastic because I have a feeling that the maintenance costs will increase on account of all those extra parts.

Rotor blades / gear boxes / engines have to be inspected and repaired or replaced based upon service hours or on condition.  The vibration is what kills the components.  All vertical lift machines vibrate like mad, even if they use electricity instead of gasoline or kerosene to produce power.  Those who have flown electric have noted that the vibration and noise in the cockpit is nearly identical to a gasoline or kerosene burner.  The exterior noise is far less of an issue with electric, but that's because most aircraft have little to nothing in the way of adequate exhaust mufflers.

In any event, the shorter and stiffer blades should last a bit longer, assuming other factors don't kill them first.  You have "X" number of thousands of hours for each blade or propeller before you have to send it off to a repair station, even if nicks from rocks or whatnot haven't caused you to repair or replace them first.  The cost is in the hours spent by the maintenance personnel and time-consuming inspection procedures, more than the size of the blades.  A good argument could be made for smaller blades being easier to inspect, but that's about it.  Naturally, larger blades take more time to inspect, yet replacing 2 larger blades with 20 smaller ones won't decrease the amount of assembly / disassembly / inspection / maintenance time.  The electric motors will also require inspection, even if no repairs are needed.  The motors are indeed simpler than combustion engines, but not if you have to control 20 of them using computer software.  The structural components of the airframe also require inspection and for some reason the designers of these things have opted to include a lot more of them.

Something tells me that there are significant problems with the basic design if you need a dozen or more motors and rotor blades to assure adequate reliability.  The end result is significantly larger and heavier than a standard two seat helicopter.  Most of these companies could've designed / built / certified conventional electric powered helicopters for the amount of money they've spent on technology development.

If the electric motors / computer control software / general design concept had adequate reliability and durability for commercial use, then you wouldn't need a dozen of them.  You'd simply build one larger electric motor and connect it to a battery contained in a conventional airframe design with improved aerodynamics and reduced structural weight.  Please note that Harbor Air didn't build some wonky system for their new battery powered DHC-3 Sea Otter.  They even have the same propeller installed.  The only difference is that a pair of electric motors provide the power and the batteries are mounted into the wings where the fuel tanks would've been.

Anyway, people have been talking about these autonomous aerial vehicles for decades now, but in the end you need a pilot's license or a pilot onboard with you.  I agree that rooftop to rooftop transport would allow for decongestion of the roads, but so would much smaller electric cars like the Microlino, which will be my next car.  I have no real use for a $50K compact car like a Tesla Model 3.  I need something with 100 miles of range, yet even that is more than I will ever use for anything but a road trip to another city with the whole family.  I drove 25 miles to work, each way, prior to COVID-19.  Some of the longest commutes that my fellow IT people have are around 40 to 50 miles.  Houston virtually requires a lot of driving to get to other places.  The 440V in the garage is more than enough to recharge a Microlino type vehicle overnight.

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#40 2020-09-28 20:35:03

tahanson43206
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Re: Autonomous Passenger Carrying Electric Aircraft

For kbd512 re #39

Thanks for another (of your many) thoughtful and thought provoking posts!

I appreciated (in particular) your in-depth analysis of the maintenance challenges for the drone "taxi" design.

My first impression of the vehicle was that it is the natural result of a team learning a given technology (in this case drones) and seeing how far they could go with it.  The design team would have (if I am right) absolutely NO idea what you are talking about or thinking of.   Drones are NOT made with a single motor, although in another Universe they could have been.

If the company is successful in finding a market, then FAA certification would follow, and (I am hoping) the rigor we expect from the FAA would extend into this technology arena.  It is my understanding the FAA is already attempting to deal with autonomous drones for package delivery, so this vehicle would be similar although (of course) much larger.

I recall from the article that the plan is to eliminate the requirement for a trained pilot on board.  This seems to me to be a natural progression, ** if ** the FAA approves autonomous drones for package delivery.

If you were one of these wealthy persons, and could decide on either a 5 minute flight from the 100th floor of your tower to the 75th floor of your friend's tower, or a two hour excursion by elevator to the first floor, then an automobile ride in choked traffic to the destination tower, then a ride up the elevator, you might choose the flight.

*** Glad to hear about the 440 in the garage !!! That is a status situation up with which the Jones will NOT be keeping, I'd wager!

(th)

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#41 2020-09-29 06:50:28

kbd512
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Posts: 4,018

Re: Autonomous Passenger Carrying Electric Aircraft

tahanson43206,

The types of drones that carry packages have nowhere near the level of testing for reliability that passenger aircraft have.  The testing required for passenger carrying airframes grossly exceeds the amount of testing associated with typical small cargo carrying drones.  Adding new types of failure modes by adding multiple motors and rotor blades doesn't decrease the number of test criteria to prevent or remediate failures doesn't make the design / test / fix process easier, either.  Those tiny rotor blades on the drones provide zero auto-rotation capability.  If the software or the battery fails or the motors fail, then the drone literally falls out of the sky, unlike a conventional fixed wing aircraft or rotary wing aircraft.

If I was at all interested in designing a battery powered rotary wing aircraft, then my design would use a pair of rigid contra rotating blades to reduce the diameter of the blade arc to something no greater than that of a drone, in point of fact significantly smaller than that ridiculous battery powered drone with 18 propeller blades.  The single seat Mosquito XET is powered by a single 95hp Solar T62 gas turbine with a 10 gallon per hour fuel burn rate and carries a maximum of 12 gallons of fuel for 1 hour of operation.  The Mosquito's main rotor diameter is 19.5 feet.  Substitute a pair of contra-rotating blades and then we have a prop diameter comparable to a large turboprop powered aircraft of around 10 feet or so.  It's so small at that point that it can land virtually anywhere.  We'd throw in a pair of stub wings to help unload the rotor blades in forward flight to reduce power requirements and use aerodynamic lift to support the weight of the batteries.  Although we have 4 larger main rotor blades, we have no control tail rotor gearboxes to deal with, so whatever weight the main rotors add to the craft is counter-acted by the symmetric lift they provide.

The Mosquito XET costs $55K for a factory built and test flown model, plus $25K for the T62 gas turbine engine, IIRC.  I actually contacted someone who sells the refurbished T-62 series turbines for APUs (their originally intended function), oil and gas drilling, and light sport aircraft and $25K was his price quote for a model rebuilt with parts for continuous operation at that output level, though that was for the model with the turboprop gearbox.  Altogether, we're looking at a cost of around $80K.  We could knock $10K to $15K off the price if we build it ourselves at the factory using the factory's builder assist program.  The actual kit cost is only around $35K or so, IIRC.

A 70kWh Tesla battery using the new 4680 cells would store 380Wh/kg and 1,350Wh/L (very compact), so we're looking at 405 pounds for the batteries to provide equivalent endurance, not including the cooling plates.  The empty weight of the Mosquito XET is 433 pounds, so that's obviously not practical for a 100% scale design, but we could either reduce endurance and use rooftop charging stations or increase weight.  The Solar T62 is 65 pounds, 12 gallons of JET-A 82 pounds, and the gearboxes for the main and tail rotor probably add another 40 pounds or so, thus our total battery and motor solution probably has to come in around 200 pounds or so.  That gives us a still very useful point-to-point endurance of 30 minutes or so, for no increase in weight.  If it was me, I'd add the weight, though.  Since we're effectively doubling the lift generated, we can bear the weight of a 1 hour battery pack.  The Mosquito's max gross weight is 820 pounds and useful load is 387 pounds.  Our design would have to be somewhat heavier for the same endurance, but not remarkably so.  It's effectively a flying Microlino with a 1 hour endurance, but it doesn't require jet fuel.

Is it feasible and practical to do this with Tesla's new batteries?  Yes, very feasible and also quite practical.  You need a pilot's license, but if you can afford a $75K personal aerial transport vehicle, then you can afford a pilot's license.  Let's do some quick operating cost math.  Let's say you fly to / from work for a total of 1 hour per day and land in your own driveway or parking space.  The fuel cost is $7 per day at $0.10/kWh.  With toll roads / sitting in traffic / gasoline costs, it's no different, cost-wise, than driving to work every day here in Houston.  You gain 365 hours of flight experience per year, so over the course of 4 years you've accumulated sufficient flight hours to take a test to become a commercial pilot entrusted to carry passengers in a larger vehicle.

The big question is maintenance costs of this electric helicopter.  All gas turbine powered helicopters have a dedicated mechanic, even if that person is the owner-operator.  At 50% discharge before recharge, the battery can be made to last 5 to 7 years.  I don't know about the electric motor, but I know that a EMRAX 268 flight-qualified electric motor costs $6K (I'm well aware that this motor can produce a lot more than 100hp, but the continuous output rating is what's required for a helicopter and their smaller motors are incapable of the continuous output required).  It's unreasonable to think that the motor wouldn't require some refurbishment of bearings after 2,000 hours of operation, on account of the vibration induced by the rotor blades.  The rotor blades will inevitably have to be repaired or refurbished every 2,000 hours or so and I don't see any way around that.  The rotor kit for the Mosquito is $7.2K.  So, we're potentially looking at a $7.5K refurbishment bill and that seems reasonable to me (~10% of the cost of the machine).

All owner-operators use a formula for maintenance costs to determine the total cost of aircraft ownership.  In this case, the vehicle in question is actually making money in private use, just like a personal car or truck does, because it's delivering us to and from work and alleviating traffic congestion.  It's a lot more expensive to maintain than a car or truck, but not completely outside the realm of affordability for a well-off middle class professional with a small family and a good job.  Aviation is a pay-to-play game and always has been.  The only way to significantly reduce those costs is through mass manufacture and industrialization of aviation fabrication and maintenance.  Thus far, that's proven impossible to achieve because everyone has their own ideas and few people want to simply take a very solid basic concept and spend the money to turn it into a practical workhorse, only to have other people spend their money tinkering endlessly with something that probably won't ever work, instead of "bellying up to the bar", as GW would say, and plunking their money down for a thoroughly tested and reliable machine with vast quantities of spare parts and widespread service support.  I can definitely see the appeal of a personal point-to-point transport, though.

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#42 2020-09-29 07:26:42

tahanson43206
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Registered: 2018-04-27
Posts: 5,043

Re: Autonomous Passenger Carrying Electric Aircraft

For kbd512 re #41

SearchTerm:CompareDrone Style Vehicle designs

kbd512 ... if you want future readers to find your work using ** your ** search terms, you have the option of adding them.

You have the option of re-reading your piece after you've saved it, and thinking about a word or phrase that captures its essence.

That is what a headline writer tries to do ... I've had my work poorly represented by paid headline writers, so I understand the problem.

In this tolerant site, you don't have to worry much about others misrepresenting your work, and if I miss the point I am happy to go back and edit a search term I've come up with. 

(th)

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#43 2020-09-29 12:35:31

kbd512
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Registered: 2015-01-02
Posts: 4,018

Re: Autonomous Passenger Carrying Electric Aircraft

tahanson43206,

The headline should read: "This is what a practical personal helicopter actual looks like.  Design one of those, but make it cheaper and more reliable using existing electric motors and batteries, instead of blowing mad money on something that will either never fly or never be accepted into service unless you have a sponsor with extraordinarily deep pockets who is willing to lose money on the never-before-achieved promise of personal vertical lift aviation for the masses."

My responses are primarily about what a practical and affordable air transport solution for personal transportation would look like.  It's not dictatorial.  Just as there are an infinite number of possible yet impractical designs, there are an equal number of possible and practical designs.  The basic physics that govern flight and cost are very dictatorial in nature and won't change to become more agreeable to young engineers who refuse to "see the light", so to speak.  New batteries and electronics aren't "game changers".  At best, they're enablers, if used properly.  All I've seen thus far are these fantastically complicated designs that do nothing to improve maintenance costs, to say nothing of the time required to inspect / pre-flight the airframe.  I've never "just jumped in and turned the key" in any aircraft and why anyone would ever believe that you don't have no pre-flight the airframe is beyond my understanding.

I approach design as follows:

Rather than prove how clever you are with elaborate and intricate designs made from unobtanium in specialized factories that don't exist, prove how practical and affordable you can make your brilliant new idea by using as many off-the-shelf components as you can, and make maintenance procedures as painless as is feasible.  Design something that's usable in practical ways.  Every so often, learn to tell people "no, you can't have that, because it's grossly impractical and I'd only be wasting our time and your money if I designed it for you".

There have been billions of dollar spent, squandered in my opinion given the complete lack of production models in widespread use, by people attempting to prove to everyone else how smart they are by concocting these admittedly very clever, but also completely impractical and unaffordable aircraft that are clearly meant to satisfy the neurotic desires of engineers or venture capitalists with more money than common sense, rather than what everyone else has repeatedly asked for but not received- namely, a more practical personal air transport vehicle that reduces transportation headaches instead of creating new ones.

A $500K drone has virtually zero chance of ever paying for itself unless operated every single day for at least several years.  If you charged $10 for a 10 minute flight, you'd need to rack up 50,000 flights to break even on cost.  If you make 10 flights per day, then 13.7 years to break even.  The good news is that with frequent short trips, it'd also take many years to reach overhaul condition.  At $20 per flight, you could feasibly break even before the battery is unacceptably deteriorated / aged, but we still haven't factored in maintenance costs, which dwarf our operating costs and will be a significant portion of the airframe purchase cost, come time for overhaul.  At $30 per flight, it's a safe bet that we could break even in a reasonable amount of time.  I wouldn't pay $30 for a 10 minute trip, but that's just me.

If we were doing 10 minute flights with a sub-$100K machine, then we will start to make money in short order.  For this scheme to work, the operator needs to have a PPL (~$15K) or you need a fully automated country-wide ATC system that does not require human intervention.  Thus far, no such fully automated ATC system exists, which is why you have private pilots with $15K worth of training.  It's only 40 hours to get your driver's license ($1K), 40 hours for PPL for single engine land ($10K), and 40 hours for PPL for single engine rotary wing ($15K).  A good number of people involved in civil aviation commute to work using small homebuilt single engine land aircraft, but expanding the pilot base will take real work, and the number of PPL holders has gone down every single year since the early 1980s, by thousands per year.  That's what you're truly up against.

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#44 2020-09-29 17:28:40

tahanson43206
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Registered: 2018-04-27
Posts: 5,043

Re: Autonomous Passenger Carrying Electric Aircraft

For kbd512 re #43 ....

SearchTerm:Synopsis Helicopter Electric Design Practical

http://newmars.com/forums/viewtopic.php … 37#p172737

(th)

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#45 2020-12-10 20:17:57

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

With a 500-Mile Range, This New Electric Chopper May Be the World’s Most Efficient eVTOL

If it lives up to initial projections, AMSL Aero's recently launched Vertiia could have a top cruise speed of 186 mph and eventual range of 500 miles.

Lead-Vertiia-PXL_20201124_220940597._exported_2167_1606430788877.jpg?w=1000

AMSL and U. of Sydney are also developing a hydrogen fuel-cell version that they expect will refuel faster and extend the range to 500 miles.

The first step, though, will be getting the aircraft certified, a process that can start in earnest now that there’s a prototype. AMSL believes they can have Vertiia in commercial use in 2023.

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#46 2021-02-10 19:43:09

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,242

Re: Autonomous Passenger Carrying Electric Aircraft

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