I don't think I fully understand how this would work... what would the electric motor be powering? Propellers? A ducted fan? I remember Elon mentioning "electric jet", but in my Googling of what a jet engine is, it seems that it fundamentally works by combusting fuel, so it doesn't seem like "electric jet" would be the proper wording.
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Electric planes
- Thread starter doug
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I don't think I fully understand how this would work... what would the electric motor be powering? Propellers? A ducted fan? I remember Elon mentioning "electric jet", but in my Googling of what a jet engine is, it seems that it fundamentally works by combusting fuel, so it doesn't seem like "electric jet" would be the proper wording.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Well he did say just a bit later on in that same interview: Just gimbal the electric fan. So I think he's basically just talking about a powerful battery driven fan. The main reason jet planes don't fly higher is that there is not enough O2 in the atmosphere there to combust the jet fuel, no such problem with a battery powered fan. A jet otherwise works well even in vacuum, as we know from space travel. But with spacecraft you carry your own oxidizer (liquid O2, liquid nitrogenoxide or something else).
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
I guess, since then you will be able to have a more directional effect for take-off for example. However this is guesswork on my part.
To achieve supersonic speeds it would have to be shrouded/ducted. Otherwise the fan blades exceed Mach and basically destroy themselves/aircraft with shockwaves.
The shroud would have to slow the incoming air (get larger in diameter after the opening) run the fan to increase speed but still in sub-sonic range, then shrink down the shroud to increase the air speed again this time into supersonic range.
So you would end up with a small 'mouth' a large central cavity and a small outlet. It would look quite weird.
Most commercial jet liners are actually turbofan engines (which while still jet engines) which produce most of their thrust with a fan rather than expanding combustion gases. The problem is that they are very large, and thus produces a lot of drag. And going supersonic the central part of the housing would have to be much larger than the mouth and exhaust. Turbofan - Wikipedia, the free encyclopedia
Im not too sure that a small hole to a larger cavity will decrease the air speed much. In a rocket nozzle, after the gas passes the waist, the expansion decreases the pressure and temperature but keeps the speed of the gas high. Though at the outlet you should have something like a nozzle i assume. But the inlet should be larger than the outlet. probably you just need the air to bounce on something instead of going directly in.
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May be like this, but with fan instead of combustion and a slightly larger intake: http://en.wikipedia.org/wiki/Ramjet#mediaviewer/File:Ramjet_operation.svg
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May be like this, but with fan instead of combustion and a slightly larger intake: http://en.wikipedia.org/wiki/Ramjet#mediaviewer/File:Ramjet_operation.svg
My discussion of a mouth and large central cavity are correct. You HAVE to slow down the air so your fan blade tips don't go supersonic. This means decreasing the air flow significantly below Mach. To do this the only way is to increase cross sectional area inside your shroud/duct. Sure it won't be as simple as a hole in a big box. There will be internal baffles, and other aero surfaces to prevent stagnant air pockets inside the fan. All this goes away if we start talking subsonic flight, or are using combustion to greatly increase the air mass ejecting from the engine.
Basically a supersonic fan needs to be the opposite of a venturi tube (Venturi effect - Wikipedia, the free encyclopedia). Instead of necking down, and increasing fluid flow; you widen out, slow the fluid flow. At this point you impart your electric fan/compressor, increase the air flow; before necking down again and getting even heightened exhaust flow.
New article. There is more going on than I knew about.
http://rt.com/news/203687-electric-aircraft-commercial-stage/
http://rt.com/news/203687-electric-aircraft-commercial-stage/
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Very interesting article. From one of the links from that article I read about solar powered drones, that can fly for years on solar power alone. These will become common in the future. Google buys web-beaming solar drones capable of flying for years at a time — RT USA . Reminds me of the fictional "Indian solar drone" from the movie Interstellar.
deckofficer
Member
Electric propulsion in aviation
Talk about a ripe market, $40,000 old tech engines $20,000 rebuild at 2000 hours and 100LL at $6.00 per gallon and who knows how much longer leaded fuel of any kind will still be refined.
Right now you can purchase a Czech made ultralight with a 16 kw motor and 6.7 kwhr battery good for 2 hours of flight.
Song
ElectraFlyer.com - The World Famous ElectraFlyer-C
Just around the corner, GA trainer electric aircraft that is expected to reduce the cost of training by greater than 50%.
Sun Flyer by AEAC Aero Electric Aircraft Corporation
I come from flying hang gliders, prefer the quiet while flying over my time spent in Cubs and 150/152s. I'm thinking of getting the Song electric as it has decent glide of 24 to 1, so quite soar-able in ridge lift and thermals.
Talk about a ripe market, $40,000 old tech engines $20,000 rebuild at 2000 hours and 100LL at $6.00 per gallon and who knows how much longer leaded fuel of any kind will still be refined.
Right now you can purchase a Czech made ultralight with a 16 kw motor and 6.7 kwhr battery good for 2 hours of flight.
Song
ElectraFlyer.com - The World Famous ElectraFlyer-C
Just around the corner, GA trainer electric aircraft that is expected to reduce the cost of training by greater than 50%.
Sun Flyer by AEAC Aero Electric Aircraft Corporation
I come from flying hang gliders, prefer the quiet while flying over my time spent in Cubs and 150/152s. I'm thinking of getting the Song electric as it has decent glide of 24 to 1, so quite soar-able in ridge lift and thermals.
ToddRLockwood
Active Member
In larger aircraft, I wonder whether a hybrid jet engine would have some advantages: use conventional jet fuel for takeoff/landing and electric for cruising.
Yep. Unfortunately, though, we still need battery power density to multiply substantially before you can start to build some compelling and practical transportation GA aircraft.
Take a fairly efficient GA plane, the Piper Mirage, for example:
The Mirage carries about 1000# of 100LL. If you were to remove the fuel, replace the 350hp engine and associated systems with an electric motor, you might be able to allow for 1500# of batteries. If you assume the current battery power density that you have in the Tesla that would give you about 130ish kwh of power.
If you assume that the Mirage typically cruises at 65% power, then you'd need 350hp * .746 * 65% = about 175kw of power to provide equivalent cruise performance. On a 130 kwh battery that gives a grand total of 45 minutes of flight. And that doesn't include allowance for takeoff & climb power.
Further, if you're going to spend $2M on an aircraft you want to be able to go on some long trips. That means we need to be able to fuel up and keep going. Say, for the moment, that we can someday produce a 1500#, 600kwh battery. Assuming some other improvements in aircraft design, that might lead to a compelling unit with reasonable range. Further assuming that an 85kwh Tesla takes an hour to fully charge (not quite true I know but I'm sure we will have some improvement down the road), then you'd need the equivalent power output of 600/85 = 7 supercharger cables charging the aircraft simultaneously to charge the plane in an hour. Wow!
There are likely some aircraft that are better examples - maybe a Cirrus SR20 - but take a look at the numbers and I think you'll come to the same conclusion. Much as I hate the 1950s technology, ear splitting piston bangers that we have in current GA aircraft, it will be awhile before electrics become a serious candidate for replacing them.
Someday!
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At the risk of sounding like an anti-EV'er from 10 years ago, batteries just aren't ready for prime time in electric aviation (or boats).
The are 2 issues for planes:
I'm looking at the pilot's operating handbook (POH) for a Cessna 172S. Some relevant specs:
EDIT - Sandpiper beat me to the punch. Oh well. :smile:
EDIT 2 - The Electraflyer has always interested me. I've always thought it would be pretty cool to build an electric ultralight trike. I haven't heard of the Sun Flyer, although I wonder how far off it is looking at their site (is it anything more then vaporware?). And putting solar cells on a GA plane makes about as much sense as putting solar panels on you Model S and expecting any really gain in range (this thing isn't Solar Impulse).
The are 2 issues for planes:
- High continuous power demands
- Weight
I'm looking at the pilot's operating handbook (POH) for a Cessna 172S. Some relevant specs:
- Basic empty weight: 1642 lbs, max takeoff weight (w/ fuel, baggage, and passengers): 2550lbs
- Engine is a Textron Lycoming 180hp IO-360
- Cruise parameters range from 45% power, 94ktas@6000ft, using ~7gph to 75% power, 121ktas@6000ft, using ~10gph
- We'd burn through the pack in an hour or less (range would drop by 80%)
- More importantly, the plane would never get off the ground, since it would be several hundred pounds overweight.
EDIT - Sandpiper beat me to the punch. Oh well. :smile:
EDIT 2 - The Electraflyer has always interested me. I've always thought it would be pretty cool to build an electric ultralight trike. I haven't heard of the Sun Flyer, although I wonder how far off it is looking at their site (is it anything more then vaporware?). And putting solar cells on a GA plane makes about as much sense as putting solar panels on you Model S and expecting any really gain in range (this thing isn't Solar Impulse).
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Companies are looking at hybridization, and companies are also working on jet engine efficiency. It's not like it's stood still. I read somewhere that modern jets are 80% more efficient than the 50's technology and that planes have had improving safety records while doing it. With their advanced logistics, I'm sure that airlines will take advantage of any economical gains that hit the market, whether new materials, hybrid or electric engines.
The EPA is pushing hard to phase out 100LL, so short- to mid-term we'll see high octane unleaded replacements (100 octane race gas won't work, because of vapor pressure/vapor lock issues at altitude). Mid- to long-term, diesel engines running on Jet-A will probably become more commonplace (they are already gaining popularity outside the US where 100LL is more expensive than Jet-A or unavailable).
Long term, electric is an interesting possibility. There was a lot of talk about fuel cell powered GA planes a while ago.
Long term, electric is an interesting possibility. There was a lot of talk about fuel cell powered GA planes a while ago.
ThosEM
Space Weatherman
I have a hunch this is what the hyperloop is all about. It may be possible to travel at aircraft speeds without the high energy cost of climbing and air friction.
I think if you took a Dash 8, ripped out the turboprops and substituted them with motors from something like the AGV, then had the equivalent fuel load in batteries, you'd have around an hour's range. Useful in many applications.
Skydiving aircraft are another obvious target.
Skydiving aircraft are another obvious target.
deckofficer
Member
I guess I should have pointed out was that the idea was for fun aviation and training, not GA "go fast" type of flying. The Song soaring ultralight can be had with a 20 hp Baily 4 stroke engine. That 20 hp will give 500 fpm climb and will cruise at 40 mph on 3 hp. That is 2238 watts and the battery is 6.7 kwhr. My interest is for pleasure flying, not flying as a transportation tool. A private sailplane license with self launch endorsement gives all the privileges of PPL without needing a medical. The new Sport Pilot license allows flying without a medical but has too many restrictions such as 1320 MTOW, <10000', 120 kt top speed, can't fly out of the country except to Bahamas.
The Song UL powered glider is FAR 103 legal, so no N numbers, pilot license, annuals, etc.
The training aircraft will run 90 mph for 3 hours on batteries supplemented by solar, plenty for training needs and those required cross countries.
Long video, but explains electric aviation better than I could.
Aviations Next Quantum Leap - Solar Powered Aircraft - YouTube
Cliff notes for the above video presentation
1) Emerging technologies are converging to make this possible.
a) ultralight weight construction
b) very efficient design for slower speeds
c) thin film solar at 23%
d) batteries approaching 400 whr per kg
2) Market place
a) unmanned drones w/o heat signature.
b) perpetual flight for cost effective replacement to placing satellites in orbit.
c) training aircraft
The Song UL powered glider is FAR 103 legal, so no N numbers, pilot license, annuals, etc.
The training aircraft will run 90 mph for 3 hours on batteries supplemented by solar, plenty for training needs and those required cross countries.
Long video, but explains electric aviation better than I could.
Aviations Next Quantum Leap - Solar Powered Aircraft - YouTube
Cliff notes for the above video presentation
1) Emerging technologies are converging to make this possible.
a) ultralight weight construction
b) very efficient design for slower speeds
c) thin film solar at 23%
d) batteries approaching 400 whr per kg
2) Market place
a) unmanned drones w/o heat signature.
b) perpetual flight for cost effective replacement to placing satellites in orbit.
c) training aircraft
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