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First all-electric seaplane takes flight in B.C.

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Re: First all-electric seaplane takes flight in B.C.

#111

Post by catalogia »

darksaints wrote: post #29
aphextron wrote: post #22

Earlier quoted context omitted.

>A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. No, it's not. A propellor creates thrust by slicing the air and creating lift just like a wing, but in a forward direction. A jet engine's fan blades create no thrust in themselves. They provide the compression needed for combustion to occur within the engine, and thrust is created by the expelling of hot exhaust gasses.

No, the exhaust is not the primary thrust generator, unless you're talking about military jets. The fans themselves are creating the majority of the propulsion. Modern high bypass designs have bypass ratios of ~10:1, meaning for every 1 lb thrust generated from the exhaust, 10 lbs comes from the fan. https://en.wikipedia.org/wiki/Bypass_ratio

Note that modern military jets have low bypass ratios, but not zero. They use low-bypass turbofan engines, not turbojets. Even cruise missiles use turbofans rather than turbojets. I think the only place you might see a turbojet flying today is in RC scale aircraft.

Re: First all-electric seaplane takes flight in B.C.

#112

Post by copperx »

semi-extrinsic wrote: post #27

You can do small aircraft like this, no problem. The trouble is you can't scale it up, due to how quickly the power and energy demands go up. This thing is 560 kW and gets a range of 86 nmi; an A320 is around 40 000 kW and has a range of 3 500 nmi, while an A380 is around 80 000 kW and has a range of 8 500 nmi. Going from this DHC-2 to the A380 requires an increase in energy storage by a factor of around 14 000x, whi…

Is this battery limitation how we get flying cars?

Re: First all-electric seaplane takes flight in B.C.

#113

Post by [deleted] »

Gibbon1 wrote: post #84
Gravityloss wrote: post #37

Earlier quoted context omitted.

How would planes would look like if fuel prices increased a few fold? I would assume probably less jets and more turbine aircraft, at least on short trips. Straight wings and slower speeds. Boeing and Airbus might lose some market share. Boeing never had a turboprop, Airbus owns 50% of ATR.

> How would planes would look like if fuel prices increased a few fold? Like High speed rail

[deleted]

Re: First all-electric seaplane takes flight in B.C.

#114

Post by Robotbeat »

semi-extrinsic wrote: post #95
Robotbeat wrote: post #79

Earlier quoted context omitted.

This is not true. It's easier to scale up. You get more efficient. Scaling up an electric motor is not particularly hard. Some of the largest machines in existence are electric. Power is not a challenge for electric. In fact, this electrified seaplane has much more power (560kW) than the original radial piston engine one (336kW), and even more than the turboprop conversion (510kW). A LOT of very confident people on t…

I'm not saying it's impossible to make a 5, 10, 15 seater all-electric work. I'm saying a 100 passenger all-electric will never fly without a revolution in battery tech. You say "just increase mass of the vehicle which is battery". If you read about this airplane you find that since they are using batteries with an appropriate safety rating for aviation, they've used all the space and mass already: "this eBeaver isn’…

They're using an existing certified battery for the prototype, not for operations. It takes time to certify battery chemistries.

And small general aviation aircraft like these usually only have a small portion of their takeoff weight as fuel, maybe 20-25%. But passenger aircraft may have 50% of their takeoff weight be fuel (for instance, 777 on long haul flights). Electric aircraft like Eviation will need to go further (55%). This is something you can do with a cleansheet design like Alice, but can't with a mere conversion designed literally over 70 years with manufacturing and materials from 70 years ago.

And you can apply the same principle of increasing take-off weight fraction for kerosene-powered aircraft as well. The Virgin GlobalFlyer was 82% fuel on takeoff. It flew around the world and then some. Kerosene is much better than it needs to be to enable modern flight.

You're absolutely right about Alice being late, but the design concept is a good example of what is possible. You combine state of the art but existing lithium ion chemistry (which needs some work for aviation certification but IS used on the ground already) with state of the art lift to drag ratio (and perhaps additional innovations, like wingtip propulsion to reduce losses from wingtip vortices) with efficient enough structural mass to enable 55% of the takeoff weight (as well as landing weight, of course) to be battery.

These things multiply together to enable long range.

Re: First all-electric seaplane takes flight in B.C.

#115

Post by munificent »

jjoonathan wrote: post #103
eloff wrote: post #96

Earlier quoted context omitted.

We can accomplish the same by producing the jet fuel using electricity. Realistically this will likely involve methane (natural gas) extracted from the ground and water, but it could one day be carbon neutral using captured carbon. The trick is to use clean energy like nuclear of renewables. There was an article on HN just recently about doing that with portable nuclear generators like those used on ships, this could…

Or biofuel. Plants are good at capturing atmospheric CO2 and the resulting biomass can be turned into fuel using well established technology. If it's nearly suitable for cars I suspect it's even more nearly suitable for aviation on account of the lower volumes and higher margins.

Now I'm just imagining some sort of steampunk wood-burning airplane.

Re: First all-electric seaplane takes flight in B.C.

#116

Post by Robotbeat »

ben_w wrote: post #88
Robotbeat wrote: post #79

Earlier quoted context omitted.

This is not true. It's easier to scale up. You get more efficient. Scaling up an electric motor is not particularly hard. Some of the largest machines in existence are electric. Power is not a challenge for electric. In fact, this electrified seaplane has much more power (560kW) than the original radial piston engine one (336kW), and even more than the turboprop conversion (510kW). A LOT of very confident people on t…

All depends on what you want. You can have “infinite” range with “no” battery — gliders are a thing, you can rise on thermals and turn the potential energy into kinetic to get wherever. But if you want to go as fast as a chemical engine and sustain that for as long as a chemical engine , you either need at least the energy density of a chemical fuel or some way to refuel in-flight. Fuel efficient often means “slow”.…

The longest range conventional chemical aircraft flew around the world without landing. It's not necessary to equal that range for any commercial application. Kerosene is better than it needs to be.

Fuel efficient for aircraft doesn't necessarily mean slow, however (unlike ships). What matters is cruise lift to drag ratio. As long as you can adjust cruise altitude for peak efficiency and as long as all the flow is fully subsonic, then lift to drag ratio is mostly independent of speed (as you can increase altitude where the air is thinner to compensate).

So yeah, electric aircraft might stay at Mach 0.5 or so, but they don't need to be slow. Mach 0.5 is still much faster than any passenger high speed rail service and MUCH faster than car or bus or boat.

Pure electric intercontinental may be feasible for near-term chemistries like lithium-sulfur if you continue to push efficiencies (both structural and aerodynamic). Very long haul, like LA to Tokyo, will need lithium-air technology which is a few decades off.

Re: First all-electric seaplane takes flight in B.C.

#117

Post by fragmede »

0xffff2 wrote: post #107
anongraddebt wrote: post #70

Earlier quoted context omitted.

I agree. But can you explain why this is? For me, it's just a hunch.

It really just comes down to energy density and the fact that batteries weigh just as much when you land as when you takeoff, whereas you burn off most of your fuel over the course of a jet-powered flight. Those two things together mean that as you increase the size of your aircraft, batteries take up a bigger percentage of your available weight budget. It's pretty much a smooth curve, with the breakeven point depend…

Pedantically, the batteries do weigh less when depleted. Not enough to make any sort of difference, but E=MC^2. We're talking micrograms for a battery the size used here. Doesn't invalidate the point that electric airplanes can't work effectively with current lithium-poly battery technology though.

Re: First all-electric seaplane takes flight in B.C.

#118

Post by variaga »

mcsb4 wrote: post #104
manigandham wrote: post #100

Earlier quoted context omitted.

Cars are not airplanes. Electric cars are much heavier but weight isn't a big problem on the road. That's why they work, and they're still catching up to traditional range expectations. With airplanes, you have to lift that weight using the same energy stored within. In that case, energy density is the absolute issue. Nothing else matters. There's no magical solution, a high-school physics class will teach you how to…

> the potential energy requirement to lift up a certain amount of weight, and dividing by energy density and volume of current battery tech does not lead to a working jet any time soon. E=mgh E=(1kg * 9.81m/s^2 * 10.000m) / 3600s = 27.25Wh. Tesla currently is at around 260Wh/kg thus roughly ten times the amount of potential energy needed to get to 10.000m altitude. I'd assume that till 2030 we get to ~500Wh/kg by imp…

>Tesla currently is at around 260Wh/kg thus roughly ten times the amount of potential energy needed to get to 10.000m altitude.

That's the energy - assuming 100% efficient conversion of battery power to altitude - to lift _only_ the battery to altitude (and then immediately fall back down).

Actual engines are nowhere near that efficient and you'll presumably want to lift the rest of the airplane too. Then you have to keep using power to keep the plane aloft and land it safely.

Your hypothetical 2000Wh/kg future batteries still have a specific energy less than 1/5 that of aviation fuel (Jet A = 11950Wh / kg). A 15-seater electric with 1000km range based on those magic (7.5x better than state-of-the-art) batteries would instantly upgrade to a 5000km range if you tore out the batteries and replaced them with a gas tank of equal weight.

Batteries need a ~40x improvement in their specific energy density to make sense as an energy source for aircraft that depend on thrust for lift.

Tragically, physics doesn't care that battery powered planes would be cool.

Re: First all-electric seaplane takes flight in B.C.

#119

Post by bamboozled »

semi-extrinsic wrote: post #27

You can do small aircraft like this, no problem. The trouble is you can't scale it up, due to how quickly the power and energy demands go up. This thing is 560 kW and gets a range of 86 nmi; an A320 is around 40 000 kW and has a range of 3 500 nmi, while an A380 is around 80 000 kW and has a range of 8 500 nmi. Going from this DHC-2 to the A380 requires an increase in energy storage by a factor of around 14 000x, whi…

I’m sure you have your valid reasons for doubting the feasibility of such a plane, yet here we are in 2019 talking over a network which was completely inconceivable at one point in history.

I just read your message as, “Can’t be done yet, will most likely be done somehow in the near future”.

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