H’m. So,worst case day, you’d want about 3.5 hours endurance?
Fuel load in an electric plane is not an issue, obviously. A full charge weighs the same as depleted. So, no matter what, you could always ‘fuel’ for worst case…unless charging time then becomes the main factor, now that I think of it. Hmmmmmm.
…anyway. I’m wondering, as an interim step, they might want to try a “hybrid” airplane. One with both burner engines - jet or turboprop - and electric engines. Use all engines for takeoff until you reach cruising altitude and speed, and then throttling back the burners and cruising on the electric alone.
I’ve never seen anything like this suggested or in development, so there’s probably *something * wrong with the idea.
I think you’re conflating me with Sam Stone. I never said I thought the drag reduction from the blown wing would be “a few percent.”
I said I thought that a realistic drag reduction would be not 500% but rather 5-10% of that number. That means I expect a net drag reduction for the whole plane of about 25-50% compared to the piston-powered original.
I certainly don’t think the X-57 project is a waste of time, if that’s what you’re thinking. But you accepted the press-release claims at face value, arguing that electric planes were so fundamentally different from internal-combustion planes that 500% seemed a realistic number to you. It’s not realistic to me, and I said so. That’s as far as it goes.
Also, in fairness, I misread your post above. You said “5-10% of the press-release number” (not 5-10% total–my mistake), which would be a 25% to 50% improvement. I agree with that, and noted in my post before yours that only the 1.5x from the Mod II to Mod III is clearly only from aero. If they can only achieve a 1.25x improvement, I wouldn’t be utterly shocked.
Nevertheless, even the lower end of your range counts as far more than “a few percentage points”.
Duplicate post—NM
You responded to a post which was entirely directed at Sam Stone, who made several statements which contradict what NASA is saying. They would still contradict what NASA is saying whether the improvement is 25%, 50%, or 500%. Or 10%, for that matter. I probably should not have cited the 5x, but the actual figure isn’t crucial to the response.
We are in agreement that the 5x does not reflect the real aero improvement–that is more like 1.5x, as I noted before your post. I’d even agree that this is probably optimistic. Nevertheless, it is still not an incremental improvement.
BTW, thanks for the link above; I’d been looking for something more substantial than press releases and videos.
Well… On a worst case day, Canberra isn’t suitable as an alternate, and so you’d need more endurance to reach a further alternate. The more endurance your aircraft has, the less likely it is to be grounded by the weather forecast for the destination and close alternates.
For electric to go big, as in 100+ seat passenger aircraft, you’d need to have a way to vary the battery load and weight, you’d also need to cater for a 30 minute turn around. Having slot out / slot in (SOSI) batteries would allow for an appropriate number of fully charged batteries to be installed for a specific flight.
As for a hybrid craft, I can see it working for a turboprop but I’m not sure if an electric ducted fan would be compatible in profile with jet engines. You are not the first to think of it. Electric planes promise big benefits for air passengers and the planet
I was thinking more along the lines of, say, the Convair B-36, in a way. Picture one of those, way smaller, with the pusher props being connected to electric motors, with a couple of turbofans using basic jet fuel slung underneath the wing, say. It’s sort of an interim step to full electrically powered aircraft.
But they do. Yaw control is *entirely *by thrust differential when they’re going for low radar cross-section. Otherwise it’s done with the split flaps, which are basically just like controllable air-brakes. But because they stick out they increase the radar cross-section.
Now, when using the thrust differential, they probably don’t have a lot of control authority. The turbojets are slow to respond and being close to the center, probably have some limit to how much torque they can actually apply. But this wouldn’t be true for a whole row of motors.
That’s true enough, but the plane still has ailerons which could compensate for that. Obviously you aren’t going to control all this with hydraulic or mechanical controls; it would have to be all fly-by-wire. It may not even be a good idea in the end, but given the popularity of flying wings in concept designs (and very occasionally in real life), there’s obviously a lot of interest in getting rid of control surfaces.
You would have to reduce it, but not necessarily shut it down completely. I’m not sure even an ordinary rudder could compensate for a full motor-out scenario without doing something with the motors on the other side. It would definitely be a less efficient regime, but again this is a failure scenario.
It flew on Tuesday … for 15 minutes.
A 62-year old plane electrified. Nope, not a contrast at all.
People keep coming back to battery weight in this thread. Again, everyone I know of working on storage and propulsion for larger planes is not even considering batteries.
Electric flight. On Tuesday, commercial flight began.
Rats, beaten to it.
We appear to be talking past each other. I was not talking about the NASA plane at all.
Fair enough, and for the record I’m more or less in agreement about Eviation. Though the entirety of aviation is filled with fly-by-night (heh) startups, so I’m not sure about the overall relevance.
Nevertheless, you made a few specific, general claims, like that a highly-loaded wing is not the way to go for efficiency. But that’s very explicitly a goal of the NASA project and they expect significant improvements–not a few points, but up to 50% (combined with the other factors).
Probably Eviation will fail, but NASA isn’t limited by the poor track record of aviation startups; they’re just doing basic research. If their low-area wing pans out, we’ll see the data.
Note that this was a test flight of a new propulsion system. It’s hoped this will eventually pass certification and conduct commercial flights with paying passengers.
It’s a pet peeve of mine, as I’ve been involved in aviation for 30 years, including the homebuilt movement, and I’m getting sick of hucksters taking money off of people for fanciful planes with $40 ‘info-kits’, or funding pleas for planes that only exist as sketches or empty mockups. The kickstarter era has turned this type of scam into an art form.
This stuff is made worse by the incredibly poor tech reporting from silicon-valley ‘tech’ journals like The Verge, who seem to think that every idiotic ‘disruptive’ kickstarter project or fanciful idea existing only as CGI renderings is the next great thing to be breathlessly reported.
Eviation just has the feel of another company that is mainly engaged in rent-seeking and separating investors from their money. I’d love to be wrong, as their machine would be cool if it works. But then again, so would a Moller Skycar.
The electric Beaver looks like a much better bet, because they started with a robust certified airframe and built out the electrics to solve a very specific problem that fits within the limitations of electric propulsion. The STC process is still going to be a bitch, and they need to double the range to make it work, but at least it’s in the ballpark.
I don’t believe I said a high wing loading is inefficient. I said that a high wing loading is a tradeoff - poorer takeoff, landing, and climb performance in exchange for higher cruise speeds. It sounds like NASA is trying to use the small electric motors to overcome the takeoff and climb issues so fhat they can use a higher wing loading. I will have to read up on that plane some more,
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Probably Eviation will fail, but NASA isn’t limited by the poor track record of aviation startups; they’re just doing basic research. If their low-area wing pans out, we’ll see the data.
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Yes, but NASA does LOTS of research on things that never pan out. Hell, NASA is studying the EM drive, and it’s not even physically possible. So the mere existence of a NASA program means next to nothing when it comes to near-future products. I still support the research, and we will learn some important stuff from it that will make electric aircraft more feasible, but NASA doesn’t have to worry about little things like certifiability, comfort, cost, manufacturing difficulties, maintenance, etc.
We talked about this plane at length earlier in this thread. The current incarnation has only a 15 minute range with a 25 minute reserve. That’s not nearly enough. But they think they can repackage the batteries and bump the range up to 30 minutes with a 30 min reserve - which is the bare minimum they need for their use case of short island-hopping flights.
This plane would not be usable for much more than that. A 30 minute endurance in a plane like that would be enough for taxi, takeoff, landing, and about 15 minutes of cruise, or a range of maybe 50 miles. That’s fine for flying between two of the many islands around Vancouver, but that’s about it. Works for them, but will never be a reasonable general purpose electric airplane solution.
You did use the word “efficient” but I won’t harp on that point. Perhaps you were mentally including all the extra stuff you need to make a high-load wing have reasonable performance, such as more powerful engines and lift augmentation devices.
The distributed nature of the electric motors enables what they call a “blown wing” configuration. Any pilot already knows that you get significant lift from prop wash; the small motors enables that over the entire wing (with, they say, minimal extra drag at cruise).
Yeah, I imagine they function somewhat like leading edge slots - diverting more air over the wing to prevent boundary layer separation at high angles of attack. Is that correct? If so, it could easily be more efficient, as you aren’t diverting high pressure air flow from under the wing.
I’ll have to read more about that plane. Sounds interesting,
I think it’s really just pushing a lot more air over the wing–it’s not a “trick” to get a higher angle of attack without stalling. Whatever extra speed the props can give the air, that directly corresponds to a lower takeoff speed. Like a self-generated headwind.
Random thought from a nontechnical person: the batteries don’t weigh [measurably] less when they discharge…but they’re no longer helping, while they do add significant weight. In World War II we extended the range of aircraft with drop tanks, disposable fuel tanks whose weight and drag were eliminated by dropping them from the aircraft. Would droppable SOSI batteries be a good idea? Obviously with a recovery system, like a chute and beacon, or even drone flight back to a charging station. Fly partway out, discharge some battery packs, dump them, keep going without their weight.
Battery technology is showing a lot of promise now that interest in renewable energy has stimulated research money. Expect large improvements in the near future.