161–170 of 272 posts
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You can't really rain burning battery pods down on the landscape, though. What if the plane is over a populated area?
Or a dry forest, or grassland. Burning lithium probably can't be all that good for ponds, rivers or lakes either.
I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.
A battery fire is a scary prospect unless the fire can be effectively contained and the hot gases vented (I don't suppose extinguishing one is likely to be an option.) There has been at least one crash involving fire, though I have not been able to find out if it was a propulsion battery fire. [1] In Eviation's Alice, the failure or shutdown of one of the wingtip's motors would require the shutdown of the other, on a…
Why so few motors? Electric motors have low cost and low maintenance, so I would expect electrical planes to have many of them. Overpowering the motor during the entire take-off would bring a high risk of having it fail too. But overpowering it to overcome the most common obstacles is perfectly viable in an emergency. Anyway, about fires, they are a reasonably easy problem to deal with. Fires on liquid are much more…
I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.
As someone who regularly pilots a piston-single, I'm looking forward to what hybrid or full electric can do for us little guys. The takeoff phase of flight is a high-risk situation in events such as fuel contamination which could prove fatal. Having a small buffer, even a few minutes of battery power to rely on while trying to get back to the field to land the "impossible turn" [1] would make me feel a lot better and…
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> Oh and it would be so quiet. would it? I was under the impression that proppelers were much louder! what is the biggest source of noise in an aircraft/type?
Ah, good ol' Thunderscreech[0]! > The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger". On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away. Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the sp…
As others have noted, electric flights require a major breakthrough in the battery technology. Here are energy density numbers for gasoline, jet fuel, and lithium-ion batteries: Gas and jet fuel specific energy density ~= 45 MJ/kg; Lithium-ion specific energy density Even worse, a jet engine is much better at generating power. A modern high-bypass turbofan engine can generate 10 kW/kg whereas an electric motor is aro…
This is constantly repeated, but it's not true. I work in the field of electric motors for electric aircraft, and the amount of nonsense constantly repeated on the Internet about how electric flight cannot be done without a breakthrough is breathtaking. Electric motors can achieve FAR greater than 1kW/kg. Here's one used sometimes on electric aircraft capable of 10kW/kg, same as a jet engine: https://emrax.com/produc…
...Transpacific (i.e. reaching Asia from North America) wouldn't be too hard as you can hop along Alaska and the Aleutians, but reaching Hawaii is a major challenge. To get to Hawaii from LA takes 3800km (at the edge of what you can do with L/D of ~40-50 and 500Wh/kg batteries). Taking the long way from the Aleutians to Midway cuts that down to 2600km for the minimum hop distance, which is perhaps feasible with a sailplane-like L/D and the next-generation lithium-metal and/or lithium-sulfur batteries (that are already demonstrated at the lab scale).
Lithium-air is the breakthrough in battery tech people want, which will enable much easier transpacific flights at transonic speeds (rather than the ~Mach 0.50 speeds you'd be limited to for the most extreme high performance airfoils), like what people are used to already. Lithium-air would also potentially enable long distance supersonic electric passenger aircraft.
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You could mount batteries on pods that could be released if needed. Additional benefit would be that the pods could be replaced on the ground by fully charged ones for faster turnaround.
You can't really rain burning battery pods down on the landscape, though. What if the plane is over a populated area?
Does weight make a significant difference once the aircraft is at cruising altitude?
As others have noted, electric flights require a major breakthrough in the battery technology. Here are energy density numbers for gasoline, jet fuel, and lithium-ion batteries: Gas and jet fuel specific energy density ~= 45 MJ/kg; Lithium-ion specific energy density Even worse, a jet engine is much better at generating power. A modern high-bypass turbofan engine can generate 10 kW/kg whereas an electric motor is aro…
>In short we need much better batteries and much lighter motors. This is not going to happen anytime soon.
this is exactly what is happening right now in front of our eyes :)