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The age of electric flight is finally upon us

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Re: The age of electric flight is finally upon us

#91

Post by username444 »

NeedMoreTea wrote: post #74
gingabriska wrote: post #70

I wonder if it can be possible to tap into the human body's energy store and use that to make flights over short distance.

Average human at rest puts out about 100w of heat. That's probably not enough to keep the cabin warm let alone power the aircraft. Burning human fat stores seems a mite dystopian. ;) Edit: Human at rest. I imagine Ryanair might be keen on pedals for everyone, but I can't see that being popular with the holidaymakers.

https://www.cascadebiketrainers.com/news/2015/09/01/calculat...

Seems a trained person can do 150-250w

Re: The age of electric flight is finally upon us

#92

Post by mannykannot »

marcosdumay wrote: post #79
mannykannot wrote: post #21

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…

A fire in an airplane is a lot more scary than a loss of power (proportionally more so in a small airplane, where an off-field landing is feasible, and increasingly they have ballistic parachutes), while there is currently a well-known problem of fires (that can't be extinguished) in high-power-density batteries. Gasoline is dangerous, but we have learned how to handle it safely.

Re: The age of electric flight is finally upon us

#93

Post by nradov »

gingabriska wrote: post #70

I wonder if it can be possible to tap into the human body's energy store and use that to make flights over short distance.

A few human powered aircraft have flown but it's just barely possible. Only the strongest athletes can produce enough power.

https://www.fai.org/news/thirty-years-longest-human-powered-...

Re: The age of electric flight is finally upon us

#94

Post by ac29 »

sokoloff wrote: post #90
ac29 wrote: post #66

Earlier quoted context omitted.

No, that's exactly backwards -- jet engines are far less efficient at low speed than at cruise speed. Various numbers I found say 100-300 kg of fuel used taxiing for single aisle planes like 737 [0][1] all the way up to two tons of fuel for large aircraft like 747 at large airports like JFK [0]. This can be extremely relevant for shorter flights: "[taxiing] aircraft fuel burn which is estimated to be as high as 27% o…

The taxi fuel is not primarily used for motivation of the airplane around the airfield, but just from idling the engines. (It's about minutes of ground operation more than miles of ground operation.) Electric drive wheels don't eliminate that unless you don't start the engines until near the hold short line (in which case, you don't have air conditioning or electric power, meaning you end up running the APU [itself a…

Yes, you'd need at least enough battery power to power not just the drive wheels, but the other things that engine power provides for like air conditioning. I wonder how large a pack would actually be required (of course there are huge differences between airports - some of them youre in the air only a few minutes after leaving the gate, some it can be 20-30 minutes).

If it was a large amount of battery, it would be cool if the batteries were in a small autonomous vehicle that disconnected from the plane when it was time to spin up the main engines and returned on its own to be recharged. Seems like a solvable problem.

Re: The age of electric flight is finally upon us

#95

Post by m463 »

marvin wrote: post #20

I fly gliders. Absolutely can't wait until my local club finally decides to get an electric single-seat self-launching glider, preferably with enough endurance to do some additional tens of kilometers after the launch, in order to avoid landing out if the weather dies out. It's a gamechanger with regards to both costs and convenience. No towplane, towplane pilot, no outlandings.

I imagine solar would be a possibility for gliders.

They have high launch energy followed by zero propulsion very high-efficiency gliding afterwards.

Covering the large wing area could with solar cells and allow for range extension or possibly even continuous flight.

Solar panels are mostly structural, but the cells themselves are basically a thin foil.

Re: The age of electric flight is finally upon us

#96

Post by aphextron »

dTal wrote: post #89
aphextron wrote: post #49

Earlier quoted context omitted.

>I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. The whole point of electrifying flight is that it makes small aircraft economical for airlines. The future of inter-city transport will be light aircraft with less than 20 passengers flying out of of small regional airports. Driving to LAX and waiting in security to get on a huge jet and fly for 90 minute…

I dunno... cheap flights exist now . It's the security theater that ruins flying. Why would electric change that?

Flights are cheap because airlines cram hundreds of people into a huge plane. That's the only way jet travel is economical; small jets are incredibly expensive to operate by comparison. The entire need for security arises from the fact that you are being put in a massive plane with hundreds of other people. If you make light aircraft travel economical, you get rid of the need for security as well.

Re: The age of electric flight is finally upon us

#97

Post by opportune »

aphextron wrote: post #68
Yizahi wrote: post #56

Earlier quoted context omitted.

The answer is - railway ;) . I doubt that small craft (any prop type) will ever be so quick overall - they are aircrafts and require all aircraft related checks and control, safety for passengers, safety from passengers etc. And about price I don't know, maybe it will be slightly cheaper than jets. So you'll have slightly cheaper businessjet prices, which are still astronomical.

Rail is an option in less developed countries, or places like Europe and Japan where the easements have existed for centuries. But building a new high-speed rail line in the US is basically a nonstarter at this point. Electrified aviation will be more than 10x cheaper vs turbine based. Practically the entire cost of aviation is in the engine, with its' associated fuel logistics, maintenance requirements, and pilot tr…

No, the longer we wait, the more expensive it will become. The population of the US is increasing and it's almost all going to cities. We should be building rail ASAP to meet the needs of now and the future.

Maybe we need federal legislation to make it less of a hassle to build a new rail line but we should focus on actually solving the problem. I don't see how thousands of 20-person electric airplanes is a scalable solution.

Re: The age of electric flight is finally upon us

#98

Post by tomatocracy »

rootusrootus wrote: post #30
NickM wrote: post #17

Earlier quoted context omitted.

Yeah I have wondered about this option as well. Hydrogen fuel cell cars make very little practical sense for a lot of reasons, but most of those reasons don't seem to apply so much when you're dealing with air travel: - It'll be a long time before fuel cells are cost competitive with gas or electric cars, but for planes the cost of fuel and operation is much more significant than with a car, so the upfront cost for b…

> if a plane crashes there's a good chance everyone dies anyway That's actually not the case. Overall your odds of surviving an accident in a plane are something like 95%. Still above 50% for "serious" incidents. Sure, if the plane drills the ground everyone is going to die, but planes crash somewhat regularly with most/all surviving.

Also one of the most dangerous places to be in a plane, statistically, is on the ground. A surprisingly large proportion of historic fatalities in air accidents have been crashes on the taxiway or runway between two aircraft (eg plane lands on top of another or taxis across a live runway when it shouldn't do).

Re: The age of electric flight is finally upon us

#99

Post by tomatocracy »

marcosdumay wrote: post #88
gambiting wrote: post #39

Earlier quoted context omitted.

1kg of kerosone can be kept in a plastic tank that weighs nothing. 1kg of hydrogen has to be kept in a pressurized, pure-lead 70kg bottle, and even then hydrogen will diffuse through it in just few weeks. So to take 1kg of hydrogen with you you're taking a lot of weight in the tanks too.

> hydrogen will diffuse through it in just few weeks This one is a non-problem. I don't think there is any civilian airport with enough fuel storage for two weeks. (But the tank weight, well that is a problem.)

Very many are supplied by pipelines though to avoid that need.

Re: The age of electric flight is finally upon us

#100

Post by sandworm101 »

mannykannot wrote: post #81
Tade0 wrote: post #29

Earlier quoted context omitted.

Electric motors in their specs usually have an entry specifying a 30s or one minute window during which the motor can operate at around twice the power without damage. In this state the motor cannot maintain temperature, so going beyond that time window will shorten its lifespan or cause damage if continued. Hobbyst EVs often take advantage of this by having a small motor and overloading it when accelerating.

That's probably OK: having to replace a motor would be a small cost compared to that of an off-field forced landing that went badly.

>> off-field forced landing that went badly.

Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away.

https://brsaerospace.com/cessna-faqs/

" Q. How many aircraft saves are credited to a BRS Whole Aircraft Rescue Parachute System? A. As of August 2017, 376."

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