One thing about mature markets is they spawn opportunity through pure complexity. What does the press do but sit around discussing the size and depth and pimples on the bum of mature markets? But we spend so much time discussing the implications of what has already happened that we don’t give much space to what’s coming in the form of new ideas. So for the next week or so I’ll be doing a series of columns about new ideas, especially new technologies, that ought to interest us all.
Toward this end I’d like to invite any mad scientists to share with me what they’d like the world to know.
Leading by example I’ll start with a project my kids and I have been working on this summer — an electric airplane.
Electric planes are becoming more and more popular. In April there was here in Santa Rosa an international symposium on electric flight led by, of all people, my ophthalmologist. It’s a small world, eh?
As an emerging technology electric flight is full of new ideas as well as a lot of old ideas that need to be forgotten. We’ve attacked one of these old ideas in our design, throwing away the concept that an electric plane has to have enough battery capacity to get where it is going.
Remember Steve Jobs saw as his design strength always asking why things were done the way they were. The boys and I took this to heart when designing our electric commuter: why do battery packs have to be the size and weight they are?
Batteries are the major design feature of any electric airplane. They comprise most of the weight and cost and making the wrong battery decisions can easily doom any electric airplane project. Our design philosophy was “simplicate and add lightness” and toward that end we wanted to build our plane around the lightest (and cheapest) battery pack possible. Even better would be a battery pack that was seemingly inadequate to the task — so small as to be impossible. That’s the ticket!
Our electric plane (we haven’t named it yet) has the simple mission of flying from Santa Rosa to Palo Alto, a distance of 71 nautical miles (81.7 statute miles or 131.5 kilometers) carrying one person (me) and 10 lbs of stuff. The budget for this project is $10,000 or less. Our biggest cost by far is batteries so the fewer of those we need the more likely we are to stay within our budget.
But battery size goes beyond just cost, because the more batteries we carry the more airplane we have to build to carry those batteries. So even a slight reduction in battery size can lead to significant changes in the size of the overall aircraft.
The most obvious way to make batteries smaller is by using better batteries — those with higher storage density. Alas, our budget won’t allow that, because bleeding edge batteries are very expensive. We’re using very good nickel-zinc batteries from a San Diego company called Powergenix. While not quite having the power density of Lithium-ion or even Lithium-polymer batteries, the Powergenix cells are far less expensive and have the advantage of higher voltage and higher discharge rates. They are great batteries for this application. But since they don’t have greater storage density, the only thing we can do to make our battery pack lighter is to cheat.
Remember we’re carrying about 180 lbs of fighting fury (me) for 81.7 miles, which we’ll round up to 90 miles. That’s our target range — 90 miles. It’s easy to figure the weight of the airframe required to carry such a load that distance. We need energy to accelerate, takeoff, climb to cruising altitude, cover some distance to the destination, then reduce power, land and taxi to the recharging station. All this plus a reserve for higher than expected winds, air traffic control delays, or even rerouting to an alternate destination. Since this is only a 45 minute flight we’ll add another 15 minutes for the reserve.
Sparing you the calculations, this mission profile will require a nickel-zinc battery pack weighing approximately 270 lbs. The structure to carry that many batteries as well as me will weigh about another 270 lbs for a maximum gross weight of 720 lbs.
While this doesn’t seem like much weight, it was too much for the Cringely boys who demanded a more aggressive mission profile. Nickel-zinc batteries have high voltage, low impedance and can flow gobs of current (hundreds of amps). Unlike internal combustion engines, batteries don’t lose power with increasing altitude. And since drag diminishes with altitude about two percent per thousand feet and we have plenty of excess power for climbing, our ideal mission profile would be to climb as fast as we can as high as we can then head toward our destination. That’s why jet airliners fly high because the fuel efficiency is greatest at altitude.
The real design innovation came when we decided to use this new mission profile then add one more twist: we decided to run completely out of power at 60 miles — about 12 miles short of our destination.
By designing for 60 miles rather than our original 90 miles plus 15 minutes equals 120 miles, we’ll need a battery pack only half as large or 135 lbs. That would not only save half our battery budget (our most expensive component) it would reduce our structural weight by at least 150 lbs! That’s 150 lbs less to buy, build, and carry. At 570 lbs gross our tiny electric plane will be even tinier.
How do we do this without landing in San Francisco Bay?
There’s always a trick. In this case the trick starts with running out of power at 10,000 feet (maximum efficiency altitude) not near the ground. Our plane can glide 12 feet for every one foot of altitude it loses. So from 10,000 feet we can glide up to 120,000 feet or 22.7 miles. That gives us a no-wind range of 82.7 miles, just enough to reach Palo Alto.
But what if there’s a headwind? What if there’s an air traffic delay? What if?
Electric cars and hybrids gain efficiency by using regenerative braking where the electric motor is used as a generator to slow down the car, making electricity in the process which is stored back in the battery pack. But electric airplanes don’t use regenerative braking because, well, there’s no brake pedal and because regenerative motor controllers are more expensive.
Our plane uses a regenerative motor controller, though. Our mission profile is such that in the relatively steep descent to Palo Alto from 10,000 feet we’ll put enough power back into the battery pack for almost 15 minutes of low-power flight after reaching our destination — enough for a headwind and a couple go-arounds if necessary.
With this design dodge that allows us to buy only half the batteries we might combined with revolutionary fold-a-plane construction technology, our little commuter is likely to come in under budget after all.
This is an example of technologies and a technical approach that won’t change the world, maybe, but it’s cool and someone smarter than us might really turn it into something. Until then we have five little airplanes to build. Imagine a small flock of birds…
Love it… I guess the major hurdle will be bureaucracy (FAA?), not technology.
At that weight he has the option for LSA if it’s to be manufactured or the homebuilt method. The 15 minute reserve might prove to be a prove to be a problem with the FAA if the pilot ends up running out of fuel. 45 minutes is the usual expected reserve and I won’t go without at least an hour.
It’s Experimental Amateur Built — too fast for a Light Sport Aircraft. And the FAA doesn’t give a damn about reserves in this case.
I’d rather build and fly a real airplane. But I guess you get enough bang for the buck with your PR that it might be worth it for you BoBo.
I’m confused by your statement. What do you mean?
I think he means he’d rather build a car, truck, or motorcylce instead of a motorized bicycle. Besides, aren’t all real planes air-conditioned these days? 🙂
that’s using the old noggin! many little revolutions come from rethinking “core truths” like powering the flight all the way.
Interesting but I struggled with the concept of flying into Palo Alto with almost no reserves and at higher altitudes that cause airspace conflicts. Small time margins and complex airspace don’t mix in my mind. Seems like a lot of potential for things to go wrong.
Higher altitudes actually reduce airspace conflicts, since nearly the entire flight is above Class B airspace.
But isn’t Palo Alto under the Class B? I don’t remember the airspace exactly but the upper tier is pretty large. In that case you’ll still have to get cleared. Not a problem most of the time but occasionally they vector you a lot. That’s when I’d worry about the reserve.
Yes, it is under Class B but nearly the entire flight is above Class B and therefore not under positive control (unless I ask or file IFR). Only the descent penetrates Class B and that’s just a couple of miles and a couple of minutes.
How would adding a ballistic recovery system (parachute) affect things? It is obviously extremely desirable from a safety point of view giving you a plan B should things go wrong, but will presumably cost some weight (remarkably hard to find out how much they weigh) and appear to cost a few thousand dollars (cheap compared to your life).
No room and they don’t have the success rate you’d guess. I’m not dissing them, just saying it isn’t appropriate for me in this situation.
Bob, how about a parachute then? I like reading your articles! 😉
Certainly in the test phase I will wear both a parachute and a crash helmet.
I’d take the 12:1 glide ratio over the weight and your commitment to landing wherever the parachute takes you. At 10K he has a no wind glide of 20+ miles and there’s lots of fields and airports to the East (typical wind direction) of his route. Just my opinion.
I used to fly an Ultralight that had a chute. Even on such a light plane, you don’t want to deploy that chute unless you absolutely have to. It’s going to be a very hard landing that will probably break your body up pretty badly if it doesn’t kill you. When the prop-shaft bearing seized up on me mid-flight one fine afternoon, I followed the advice my instructor had given me (have at least one safe place to land that you can glide to at all times) and glided safely to a pasture. Chutes are for catastrophic structural failure, like a wing breaking off. You are much better off gliding to a landing in a light plane that has lost power. Power lines are another big hazard to watch out for in emergency landings, but with the chute you have lost the ability to steer.
Ballistic parachutes weigh about 35lb.
“… not near the ground.” Brilliant euphemism.
This sounds more like a battery-powered sailplane than airplane. What are your takeoff speed and distance? What kind of instrumentation/navaids are required for this?
Takeoff is very quick (under 500 feet), climb is at 80 mph, cruise at altitude is around 140 mph.
Excellent. This is the first really interesting piece here since the one about the new frontier. Keep the new stuff coming.
Although thinking outside the box isn’t unique to Steve Jobs … unless they have a patent on the concept. It’s definitely what Jobs should be remembered for, not his aggressive management style bandied about in the press.
Anyway regarding the plane and your ideas, it sounds fascinating and hope everything pans out well. Keep us upto date!
a patent about lying about battery life? bet they do 😉
What you really want is an airframe or skin material that can store electricity across the temperature range of your flight profile.
I want to BUY batteries, not INVENT them.
Instead of trying to turn the skin or fuselage or whatever into a battery, how about turn it into a capacitor?
Put some solar panels on the skin.
I hope in your mission profile you have accounted for the increase in drag caused by your regenerative motor controller, as opposed to simply feathering the prop which will give you a better glide ratio. There’ve been plenty of similar schemes proposed in the sailplane community over the years, but usually it turns out whatever power you recover is more than offset by the extra drag.
I have, actually. The native L/D is actually 22:1. That 12:1 number is with regenerative braking.
I loved Plane Crazy and I’m not even an aviation guy!
I always hoped there would be a sequel!
Don’t bet on it.
Nonsense!
What about some cheap-and-dirty clips on your new Youtube page?
I loved Plane Crazy, but I am sad it focused on the drama, not on the achievement. I understand the secret to reality TV shows is the drama or the conflict, even if they have to invent it. In the case of Plane Crazy there were some great moments of drama and it really did not seem fake.
I’m not a fan of reality TV shows, but Cringley, you keep coming up with these insanely great ideas like flying to the moon, building a plane in under 20 days, building an electric plane, launching satellites into space and the really, really good ideas you can’t talk about because of non-disclosure.
It would make really good TV because it’s real, not faux drama. I hope we get more details on this project and the others.
Plane Crazy was the best TV work I have ever done, though too painful still to watch. It is also better than what passes today for reality TV. But I think my day has passed.
Any shot of Plane Crazy being available on DVD?
This list of projects sounds oddly like the Tom Swift Jr. books I read in the early 60’s.
Can you do anything to reduce necessary power at take-off? I’m thinking that by using some kind of cable attached to a motor (or car) could you get the plane up to 60 mph and start the engine from there?
Too hard. This works fine and I can recharge, turn around at PAO, and come home.
What about a launch vehicle at the airport? One that will bring your vehicle up to speed and altitude so that you can continue the journey on your electric energy. I guess this portion of the journry should be very energy intensive. I may be wrong.
Solomon has very good point here, what about using a ground based launch mechanism? This is used by gliders (sail planes) all the time? The largest fraction of the energy requirement will be during take off so why not out source the effort to a winch?
Nope. If you have to have a launch vehicle (and a pilot) everywhere you fly, how practical is that? Believe me, it would be more expensive and not gain all that much over such a short range.
JATO! Now we’re talkin’ 🙂
once at altitude, you should need less power, so why not use a mix of batteries? ni-Zn for take-off and Lion for cruse mode? there should be a point where the lighter lion would gain you distance?
Too expensive. The logical mix you describe would be mainly Li-Ion and a LOT more money. Besides the advantages of Ni-Zn (1.65v versus 1.2v) really shine at this short range. Lithium would be lighter but performance wouldn’t be better and the plane would cost twice as much to build.
The design to which he refers is the Rutan Quickie. It’s a very efficient design. By having a significant canard in front of the center of gravity, in addition to a wing, you get stability in the vertical axis AND lift with relatively little drag.
I’ve been pondering this issue myself. I decided I’d need two battery packs: one with relatively low power density but significant energy density and another with less energy density but greater power density. Takeoff and climb-out would draw from both. Cruise would only use the low-power pack. Descent and landing would use regenerative settings, trading altitude for energy in the high-power pack. That way, if you have to how around, the high-power pack is charged and ready.
As such, it would have to have a variable-pitch propeller. It would use minimal rotational speed and maximum pitch across the speed regime, with a computer adjusting the pitch. This would reduce energy consumption across the flight.
If at all possible, the main gear would have hub motors/generators in them. They would probably be more efficient in the initial acceleration than the propeller. That would further reduce the energy consumption on takeoff and taxi.
You’re closer to having something in the air than I. If you can do the whole thing with one, high-energy battery pack, go for it.
Clever idea powering the wheels but it only makes sense if the prop is completely stalled and you have no static thrust (NOT the case with my prop, which by the way is not variable pitch — just properly designed for the mission). With all your multiple battery packs you’ll find low-loss cables consuming more and more of your empty weight — too much I decided. And about using computers to control angle of attack, etc., well you can certainly do that but the marginal improvement it MIGHT give you probably won’t be worth the added complexity. My wrist is a pretty smart computer.
How hard would it be for the batteries to double as another component of the aircraft, say for example the skin?
Too hard to bother. Skins are 7781 e-glass. We did the calculations with carbon fiber and it wasn’t worth the bother since we’d still need two plies just to handle hangar rash.
I can think of two alterations that might help you with reserve power.
1. A small turbine powered generator that could be deployed during the descent phase of flight to give you additional battery power. Shouldn’t increase drag that much and would give you some power reserve.
2. Small solar panel on wings or above cockpit to keep instruments and radio charged.
Neither part should add much weight to the design and they provide power without adding too much weight. Alternatively, you could have the generator powered by the resonance of the wings as they mechanically flex up and down during flight. Or, the wings could transfer the energy to a flywheel attached to the generator.
Just a few ideas that could be killed by reality.
John
A turbine’s redundant with the regenerative prop.
I already have a LARGE turbine-powered generator on the front of the airplane and a small auxiliary battery pack that can provide hours of instrument and radio power.
Simplicate, remember?
Now you tell us. Well, as old pilots say, you never have too much fuel unless you are on fire. Good luck with your plan. You will need it.
This sounds exactly like what happened to John Denver. Flying over the ocean in a new, unusual airplane, running out of fuel, then getting smashed up. They say he was so badly smashed they couldn’t identify the body from dental records, and had to use his fingerprints from his DUI convictions.
So anyway, good luck with the project, it sounds like a remarkable great idea.
Wow, what a bummer! I like to think your analogy is way off. John Denver didn’t build the airplane he died in and had owned and flown it for less than a day. He ran out of fuel, as you say, there was an auxiliary fuel tank (many pilots run the main tank dry to use all the fuel) but he couldn’t reach the valve from his seat and so Sayonara. My plan to run out of electrical power is different. If happens on every flight. There is no valve to reach or miss. The systems are totally automatic. All you do is glide down and electrons are there waiting to help you land the plane.
A bummer I can top: Denver’s children were fully grown when he died. I’m surprised that a devoted father such as yourself would even contemplate this. Is the great Soap Box Derby no longer enough? Here’s an alternate suggestion: live closer to Palo Alto. Santa Rosa is nice, but not nice enough to die for.
Aviation is about risk management and thankfully it’s mostly under your control. Yes you can get killed and it has it’s unforgiving aspects. That said, you can mitigate a lot of the risk. By going electric Bob is removing a certain amount of risk over a piston powered plane although he may be adding some others. He can decide to go or not go on a given day.
80% caused by pilot error is the most used number related to aviation accidents. I suspect it’s even higher than that. What that means is most accidents are preventable. Frankly I’ll take the risk of my judgement over depending on someone to not run into me on the road.
Thanks for your concern but having been a pilot for 42 years so far (since before I was licensed to drive) I feel fairly comfortable with this risk profile. So do my kids. Remember they are building this with me. So does my wife, who wants to fly it too. This is not to say I’m unaware of potential safety issues (I long ago sold my Norton 850 Commando, for example), but as the designer, builder, and pilot I have far more control over those issues than you do as a passenger. Don’t lose any sleep over me.
I believe the idea for the airplane is sound. However, I think on the maiden flight you may want to consider flying somewhere that allows plenty of places to land (not urban or mountains). This way, if there was something that was overlooked (for some unforeseen reason), you wouldn’t have the issue of missing the airport by a few miles and having to land on the highway.
And what about Steve Fossett?
Sorry but not even close. John Denver’s accident was a stall at low altitude because he was distracted by running out of fuel. It was pilot error on many levels. Not enough fuel, low altitude, unfamiliarity with and forgetting to fly the plane. There may have even been a little alcohol involved. It’s not the same thing. I am a little uncomfortable with some of the risk margins Bob is talking about but didn’t realize there was a 22:1 glide ratio with the prop feathered. You might as well say you’re afraid of driving because James Dean was killed in a car crash. Smashed him up pretty good.
also trying to use the incorrectly located fuel switch tap forced a full rudder movement, hence the stall, spin, you know the rest
Stall-spin? In a Long-EZ?
Well at least a high speed mush into the water. He was only a couple of hundred feet up so there wasn’t much room to work with.
yup, carnards stall too. Wright brothers found that out. No height for a spin it seems, so another commentors suggestion of deep mush seems appropriate. My source is an air crash investigator.
*Love* the flow of optimizations you’re coming up with. But, oh man, the hubris to commute with such low margins.
I recall the guy that commuted with his Vari-Easy (?) from some air park in the Sierra foothills, for years, till he finally ended up out of fuel, a half mile from the PAO (SQL?) 30 dike, upside down with his head 1 foot under water. Years of experience made him more and more comfortable with lower and lower margins. Just saying.
I recall, PAO is under the TCA, right? So you do have to extend to the south or penetrate it and suffer vectors. Do that for a few years and I’ll bet you $100 you declare a low-fuel emergency at least once. 🙂
I remember that guy. He commuted from Placerville. Yes, it was senseless.
I had a hangar at PAO for 20 years and know it well. Penetrating Class B (formerly the TCA) is no big deal.
And here’s the thing to remember: if I have to loiter all I have to do is slow down to 80 and maintain altitude which requires just a little more than ONE horsepower to do — less power than it takes to run a hair dryer. I can wait quite a while even on regenerative power.
If you could get light enough, cheap enough (I don’t know how well you can do on light AND cheap), cells, I’d think it would be worth it, you could have enough to get 1hp (15w per square foot, and you can use the fuselage as well), that would extend your loiter to almost as long as the sun is up, flying to Los Angles would be quite doable.
Most of the drag on the wing comes from the wingtip vortex. So eliminate the wingtips. Sweep the forward wing aft, the rear wing forward, and connect the tips in a box-wing arrangement.
Yes, joined wing aircraft enjoy some efficiency advantages but MOST of the wing drag DOESN’T come from the tip vortices. You are completely neglecting induced drag, parasitic drag, intersection drag, and trim drag. And while what you suggest is probably feasible, it isn’t easy. I’m basing this plane on a 30 year-old very proven design that has already been optimized to hell and back by 1000+ builders. I am at most an incremental daredevil.
The phrase “incremental daredevil” is damn near poetry. Loved the article and loved the followon comments.
You didn’t mention any power requirement for avionics, radios, and lights. Is all that negligible?
Would some solar cells on the wings be worth the trade-offs? My guess is No, but I have no way of knowing for sure.
We haven’t decided about the panel. It may well end up being a handheld radio in a panel clip and an iPad, in which case the power requirements are zero, zilch, nada. Solar panels are nice for keeping batteries topped-up while tied-down but as a source of primary power they make sense only for VERY big aircraft.
I wasn’t thinking about primary power from the solar cells, just a way to extend battery life a bit. As I said, I have no clue what the tradeoffs would be, but it seems to me that the wing area filled with solar cells might be able to contribute to the power equation.
Could you replace a directional gyro with an iPad app? You couldn’t use one for altimeter, airspeed, or turn & bank, as far as I know, but the steam gauge types of those in the panel wouldn’t use much, if any, electricity. You won’t have any vacuum you could draw from the engine, though, for any gyros. LED nav lights (if they’re available and approved) should use little power.
There are plastic solar panels from companies like Solarmer that could be used but I still don’t think it would be worth the bother given the mission profile. There’s only 46 square feet of wing area. Given the short range I’d rather use the weight and cost for more batteries.
No steam gauges.
46 square feet of wing area is a pretty decent amount – Given some nice silicon solar cells, like Sunpower’s C60 cells, on Sanyo HIT cells, you could probably get >750W of generation on the wings alone. I’ve got an ex-solar-car buddy who is manufacturing MPPTs for applications like this, I could get you in contact with him if you’re interested… The solar cells would definitely break your $10,000 budget, though, unless you got them donated.
Bob, properly integrating solar cell into the wings surface takes some work and skill — See Eric Raymond’s Sunseeker or our very large Swiss Solar aircraft. I doubt it is within the budget. Otherwise talk to Eric and/or Alan Cocconi (ex AC Propulsion). He also has a very nice direct drive motor design and electronics know-how.
BTW, I’d look into the effects of flying slower thus using less power.
Good Luck
I can’t wait to see what the final production price is for a Synery box wing aircraft. Fuel efficient, easy to fly, low noise, and yes a lower (by aircraft standards) price. https://www.synergyaircraft.com/
Bob,
unlike most power pilots you seem comfortable to risk not having engine briefly. Already electric powered sailplanes so already a proven concept until you get to regenerative power recovery. Good to see someone pushing the envelope a bit. I don’t see your plans as dangerous as you seem to have done risk analysis and mitigation before building and flying. I’ll stick to aircraft with no engine though. Makes flight management more intense.
I learned to fly first in Slingsby wooden gliders courtesy of the RAF as part of my service in the Combined Cadet Force (high school ROTC equivalent) so yes, I’m fairly comfortable landing on potential energy. Power pilots generally don’t get it. On the other hand, biplane pilots (I’m one of those, too) DO get it because L/D is so low that every landing is effectively without power unless you need to go around. While there is always risk, I’ve landed in enough weird places in my flying career that provided I’m flying the right aircraft on the right mission I’ve always seen a way to get the job done. When it’s the wrong aircraft or the wrong mission, I stay in bed.
As my ultralight instructor taught me, gliding down is the fun way to land!
Wow! What a bunch of nay sayers. I would have loved to have someone like you for a father!
Hi Bob!
When I read: “we spend so much time discussing the implications of what has already happened that we don’t give much space to what’s coming in the form of new ideas.”
That reminded me that in 1967, Marshall McLuhan wrote: “The past went that-a-way. When faced with a totally new situation, we tend always to attach ourselves to the objects, to the flavor of the most recent past. We look at the present through a rear view mirror. We march backwards into the future.”
Show us some picutres!
Great article!
Ciao,
Bob
> I’d like to invite any mad scientists to share with me what they’d like the world to know.
OK, here’s my suggestion: Please tell you your take on Bitcoin, which–as far as I can tell–you’ve never written about. There’s a change-the-universe potential there I think. When I was a child I clearly remember an old guy telling me that he was never going to use this thing called the “Internet” because it was just hackers and smut. A different old guy recently told me that Bitcoin was for hackers and (paying for) porn.
A lot of the power for short flights goes into climbing. So what about an electric railgun at the airport? The plane sits in a shuttle, the railgun accelerates the shuttle with plane up a ramp like a roller coaster in reverse, the plane is shotgunned up into the wild blue yonder.
The budget is $10K, remember?
Have you considered using A123’s Life batteries?? Fisker is using them in cars. Depending on the cell size you can get small ones at a good rate by purchacing dewalt drill packs and then cracking the case and joining them up. Using small batteries would get you more flexibility in placement. The batteries being LiFe, you get 80% the storage of a standard Lipo and slightly lower voltage but the charge/discharge rate is tremendous. You charge them through a direct wire connection to a car battery! Also, have you considered the moral equivalent to a battery based drop tank? Military jets carry fuel in tanks that are dropped after consumption. You could do the same with batteries and add a parachute for recovery. This would allow extra capacity that you only have to carry part of the way through the flight.
Nickel-Zinc batteries have almost the energy density of Lithium, higher voltage, lower impedance, they cost about the same as NiCd (cheap) and are simply better all around than what you suggest. No breaking open drill packs, either: you just order what you need and they build it out of 1.65-volt cells. And remember this is intended to be a PRACTICAL system, so dropping little battery packs is just plain silly. Not only does it add greater system complexity and cost, it won’t achieve your goal of (I’m guessing here) increasing range. You see jettisoning weight at altitude is throwing away potential energy that could have been recovered through regenerative air braking. That extra weight also increases penetration speed, which can be useful and is why high-performance sailplanes carry water ballast.
Since you seem to be implying you want this to be practical NiHz may work up front but from what I hear they don’t get through many charges. So after 50 or so flights you may have to replace the whole battery assembly. I am probably wrong about this but that’s the word on the street. On the flip side I hear NiHz perform better in cold which may be a good thing. However, I would imagine with the work load you will not have to worry about cold much. Is the motor going to be direct drive brushless/AC motor? This would make sense because the motors can natively handle the regenerative braking you plan on using. .
Edison had that problem with his Nickel-Zinc batteries but PowerGenix doesn’t. That’s the major problem they’ve solved so 1,000-2,000 deep cycles are now feasible.
Robert, I’m sorry I’ve been throwing crap ideas at you.. Powergenix seems to have a bad rap in a few areas but then again many companies get confusing reviews. I will be interested to see the results you have. If they are good I am tempted to give them in a try in my RC planes. Just our of curiosity could you give me the specs on the motor you are using? Kv (rmp/v), Weight, Max Current, Resistance and Max Voltage? What is the battery setup you plan to use? Voltage and amps would be nice. I would like to try and model this in RealFlight. It is probably one of the few sim’s where you can simulate electric setups. Not sure if it will scale but maybe.
Another odd idea… ditch the landing gear. Have and under carridge that you use for takeoff that separates from the blane. Beef up the underside of the fusalge and land her in the grass. RC pilots have been doing this for a long time. This will reduce drag and weight. Again another cheat.
You’d save six pounds minus the weight of any detachment mechanism. And how do I land at the other end? Will I need to build a new propeller for every flight? Simplicate!
The landing gear isn’t purely about weight it’s also about parasitic drag caused by the landing gear. Also, with your regenerative braking you have to consider this will reduce your glide rate because the prop will not be spinning freely therefore causing drag. This is a tough one and clearly you have given this a lot of thought. I’m just speaking freely so forgive my silly ideas.
This is covered in a comment above. The glide ratio is 12-to1 DURING regenerative braking (22-to-1 normally). You overestimate the impact of landing gear drag. While dropping the gear made sense for Wiley Post on his stratospheric flight in the Lockheed Vega it makes no sense during my 45 minute flight to Palo Alto.
Hey it worked great for the ME163 – oops – maybe I better do a little more research…
Ditch the landing gear, land in the grass … and then what? Be utterly stranded? Remember, Bob said he wants to be able to land, recharge, and then fly back.
In essence this makes the landing gear become the detached / disposable “launch vehicle” others have mentioned.
Wow.. Foam core wings.. how about bigger wings and turn the thing into a glider?
With a native glide ratio of 22:1 it IS a glider. And I’m not building it with foam core wings. These wings are built in female molds. Remember I’ll eventually build five of these things so some production tooling is in order to save time and improve consistent quality.
You know the more I look at this you are building a really large RC plane. I mean the plane you are building is tiny. So the next thing to consider is a better wing. Looking at these pictures of this plane I bet the airfoil is not optimized for efficiency. Also, have you considered using electronic servos for the control surfaces? Advantage is that you will eliminate the control linkage. You can locate the servos near the control surfaces and only have wires between you and the control surfaces. You will need multiple servos per control surface so you will get redundancy.
Let’s not reinvent the wheel here. Your assumption about unoptimized airfoils is completely incorrect. The canard on this design uses a Roncz airfoil custom designed for this application and highly optimized. The Eppler airfoil on the back wing is more generic but also more lightly loaded and so less critical. There’s not that much to be improved here, folks. Fly-by-wire is a possibility but it would be more expensive, save very little weight, and would introduce new (and additional) failure modes. Mechanical controls work just fine, thanks.
Hooray for someone else who’s glad to stick with boring, reliable mechanical options rather than fancy, new gizmos (especially ones which introduce potential problems).
Quite true, especially when it comes to non-military applications. Back in the early eighties I was looking for a control system for a pool/spa. Fortunately they did not exist so I had to design my own using the most reliable tech I was aware of…mechanical relays. Still working great after 30 years. Every other gadget using ICs and transistors has maintenance/replacement issues. In the 90s they came out with dc-transistor-drive motors instead of capacitor start…what a disaster for consumers of air-conditioners, washer, and dryers.
wonder about rigid composite material made from carbon fiber to keep weight down, and strength/rigidity up? then there’s lighter than air approach – perfect for electric motor (or peddle motor?!) first one person commuter “plane” was done by Henri Giffard – he was flying out and about Paris in 1852. It’s wonderful way to fly. Was flying down Ruhr Valley in a “Zepplin” made by WDR and piloted by a World War One Zepplin pilot. Japanese passenger asked pilot what would happen if engine died. Pilot non chalantly shut engine down. Japanese passenger turned “white” but color returned when he noticed airship just kept floating along.
I answered this question earlier in the comments. Carbon fiber WOULD produce a lighter structure but also one that’s more fragile. Since this is an aircraft intended for daily commuting it has to be tough and reliable. That means even with carbon fiber using more than a single ply. If you are using a minimum of two plies for toughness you may as well use plain old e-glass at 10 percent the price of carbon. Yes, a racer could be made lighter but this is a commuter.
I first read about electric planes a couple years ago. My own take is that electric cars really make little sense compared to gas-powered vehicles, but electric planes make a LOT of sense, especially if the cost can be kept low.
Electric planes are terrible for flights in excess of about one hour which makes them not very good for typical air transport. But for a commuting application like this they are hard to beat. They are quiet, cheap to build, cheaper still to fly, have very low maintenance requirements, and you could stash FIVE of these in a typical airport t-hangar.
Are you planning on making this plane? What about releasing the design specs for the hardware if not?
Of course I’m building this plane (five of them, actually) but I have no intention of publishing a design that would just expose me to liability. Aviation is useful for turning big fortunes into small ones and my fortune is small to begin with. Go design your own electric plane.
I actually meant, are you planning on building this plane for sale, but I understand the liability concerns (sad that a moonshot is an easier project liability-wise). What about the electronics then? Would you be willing to divulge your component choices? You’ve already mentioned your battery source. What about the motor and controller? The prop?
Your design decisions seem wise and well-thought out. I hope your family enjoys the project (five, one each for you, your wife, and kids, presumably). It sounds like a lot of fun. And something to write about.
The motors come from India but are modified in France where I am buying them. Yes THEM, there are two motors at 15 kw each. The motor controller is from Germany. Instrumentation will probably be an iPad. The battery pack is custom-built. The propeller was designed by the late Paul Lipps. I’ll carve the props myself.
Fascinating.
It brings up the possibilities for the next generation electrical aircraft.
While cruising at high altitudes the power required is reduced and the solar power available (in daylight) is increased. An aircraft with enough solar cells to cruise at high altitude would have an unlimited range.
To land safely it would need enough batteries to fly at lower altitude for (say) fifteen minutes. These batteries could be charged in the descent from high altitude.
To take off it would need more power but that power would only be needed at takeoff.
The boost to high altitude could be something like an electric linear motor catapult or a hydrogen rocket (with solar hydrogen from fixed plant round the airport). Once you are going fast enough to get the rest of the way to high altitude with the fifteen minutes batteries (which start charged) the booster can drop off and return to the airport for the next takeoff. The heavy bit (the catapult) stays on the ground/gets reused a lot.
This is, of course, not the aircraft you are building (not this time anyway) it’s just my thought experiment.
Joe
Electric flight doesn’t work well for long distances unless, as you say, you can use solar charging. But I see that as simply too darned hard to do. If money was no obstacle I could build a substantially larger aircraft that, as you say, would cruise at very high altitudes using more advanced battery technology. Something like a U-2 might work.
Hi Bob
Someone is doing just that in Switzerland with Solar Impulse (http://solarimpulse.com/). They want to fly around the world on solar power.
Good luck.
Really cool! Can you tell us about the motor and variable speed drive components? Is the propeller direct drive from the motor? Is the motor a comutated DC type, or AC type with a variable frequency convertor? What’s the peak horsepower used?
These are 15 kw permanent magnet air-cooled DC motors that can turn up to 3600 rpm. There is no reduction drive of any sort. The motor controller is one of the more expensive ones used in some European electric cars. The props are fixed-pitch but very cleverly designed. There’s no real reason to make them variable pitch, by the way. It wouldn’t help with regenerative braking. Electric motor torque characteristics are robust enough not to require variable pitch or a gearbox. And even feathering can be simulated by carrying about three percent power in a glide to unload the prop airfoils.
With the energy storage, wiring, and electronics, I think it would be a good idea to design-in a fire extnguisher, just in case.
There’s no place to put one. And what’s going to burn? There’s no volatile fuel and the motors don’t get anywhere near hot enough to ignite anything. But we’ve designed the battery pack to be right on the CG and capable of being loaded from below for a quick change if necessary, so if you insist I could make the battery jettisonable, though it is still not clear to me why. This isn’t lithium, remember. There’s nothing to burn.
Even though it’s not necessary, the “jettisonable” idea ist just way too cool 🙂
I like the cut of your jib, Mr Cringely!! (to mix metaphors!!) There’s a madness here that might just pull it off!
More seriously, I don’t suppose “autogiro” has any place in an electric plane? Especially one designed to “coast” the final leg. I’m guessing your take-off speed is going to be way to high for such an encumbrance but it would be such a reassuring add-on…
Autogyros make terrible gliders. I flew Little Nellie, the James Bond autogyro and it was a blast to fly but had a near 1-1 glide ratio.
Any chance of condensing water at altitude to gain more potential energy?
If you want to go a little far out with ideas… maybe one could follow up on Ben Franklin’s kite experiment to see if there’s any way to siphon electrical potential from the atmosphere before, ya know, it’s lightning?
Make a turret halfway to blast you with an (light/microwave) energy beam mid-flight? Better aim well 😉
Pedal powered generator… get your workout while you commute.
Those compressed air-car guys seem to have something interesting?
Crazy ideas I know… but it seems like the rules have changed.
Now you are just yanking my chain. It’s a little airplane intended to fly less than 100 miles. All these optimization ideas won’t improve performance and will guarantee that it never flies. The design is frozen, friends. Wait a year and see how it flies.
Someone lend Mr. Cringely a pair of Google’s fancy glasses next year so we can all go along for a test flight! 😉 Maybe that breaks the no passengers rule?
As far as never getting off the ground… you wouldn’t be surprised to hear I’m fighting feature-creep myself at the moment; or maybe I just took on too big a project.
It’s a small airplane and all so why not just for the fun of it add a gopro.com camera or something.
This is something Mr. X is not simply passionate about, but has indepth knowledge and experience in the subject. I was alarmed when you started on econimising battery capacity but obviously you know your stuff, very intimately!
I’m only a pilot wannabe, but here are a few questions i’m sure you’ve considered, but whose answers might be interesting…
1) any chance of altering the “mission” (at least for the 2nd or 3rd iteration of the plane) to include carrying a passenger along with the pilot? I think that would vastly increase the usefulness — at least beyond the Cringely squadron…
2) will the “regenerative braking” cause any weird flight characteristics? I’ve flown a sailplane a couple times, and I know that when you add an engine, you have to deal with the “p factor”(?) of the propeller/engine spinning causing the plane to want to roll in the opposite direction. If the propeller is being “pushed” by the relative wind (as opposed to “pulling” the plane through it) will that cause any unexpected or unusual performance?
3) will you need to carry oxygen if you (or kids) regularly fly at or above 10k ft?
4) what about using a facetmobile design for your airframe? don’t know what the glide ratio is, but I’ve always thought it was an interesting aircraft.
I love your columns — especially the aviation related ones!
Thanks!
Adding a passenger would blow the budget and make this project unfeasible in the Mrs. Cringely economy. Regenerative air braking just makes it descend more steeply, nothing else, and that effect can be throttled. No oxygen needed to fly for less than half an hour at 10,000 feet.
Planned product improvement – isn’t there a company in San Jose that was going to “print solar cells like newsprint” so cheap you could drape it on your roof? If and when that makes a go of it, bond some on top of the wings and add a little in-flight recharge.
Someday I would like to try to build a solar glider that uses heat for thrust – and get perhaps 85% of the insolation energy rather than the 15% or so a solar cell gets.
There are several such companies. I already mentioned Solarmer, down in L.A. Yes, this is possible but not necessary for this mission.
hmmm. My bi-weekly commute is 90 miles each way through the cornfields of Indiana. I’m just a few miles from small public airports at either end. I could keep a battery pack charging at each end of the trip. I suppose the unpredictable mid-west weather would catch me out a few times a year.
How am I going to talk my wife into this? Too bad I have no flying experience.
My thoughts exactly. If you figure it out, let me know 😉
For you and your family, Cringe, it will be just as thrilling as when Curtiss took the Albany Flyer down the Hudson (except without the pursuit train).
Having used PowerGenix AA batteries in wireless intercom gear for about a year I have to issue a warning here. If you plan to deplete the batteries below the recommended level there will be a failure rate that I will guess at about 4% or higher. This may not be a problem if the remaining cells receive more of the descent charge and can therefore carry any required load but it will need to be considered. Recharging before a certain voltage drop reduces failures to almost nil.
Thanks for the heads-up. Some of this comes down to the quality of the cells. If you smile nicely they’ll sort through thousands to give you a more reliable battery pack that runs nearer 1.8 volts than the promised 1.65 and doesn’t have the asme failure modes, either.
A few articles ago everyone was guessing what Cringely was going to do next—now we learn that he’s building a “commuter plane” to get to Palo Alto. I haven’t seen anyone make a connection between the two articles yet; is this a clue?
Clever reading there — 130 comments before someone noticed. I have a couple projects that will be taking me south on a regular basis. One is a startup I’ll announce in September and the other is a new feature documentary. Both will require me to regularly be in Mountain View where I suppose I could land at Moffett but I don’t have the same pull as Page and Brin.
You are officially my hero, haha. Other than game programmer (which I’m doing now), you are living my other dream job now. 🙂
If the battery doesn’t have to be rechargeable, use an aluminium-air battery.
http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery
Very high energy density. Some electric submarines use this battery technology.
A company in Kingston Ontario was founded by some ex-Alcan engineers to make these for powering electric cars, but they folded some years ago.
That’s the problem. I need something off-the-shelf.
I wonder if you could power an airplane by and electrostatic motor? These motors work on very high voltages and very small amperage. They are easy to build. A high voltage develops between an object at altitude and the ground. Maybe enough to power an electrostatic motor? Drag a very thin and light weight wire under the plane?
https://www.only1egg-productions.org/AltSci/ElectrostaticMotors/electrostatic_motors.htm
Electrostatic motors you can build were written about in “The Amateur Scientist” section of Scientific American, October 1974 (I guess I do have a good memory after all, with a little help from google).
Here is a pdf of the article by C. L. Stong:
https://www.meridian-int-res.com/Energy/ESMotors.pdf
It’s hard enough finding time to build airplanes without building their motors, too. I’d actually like to finish this thing…
Not that it’s needed but reducing the 180 lbs of fighting fury to 170 lbs of fighting fury should add a few miles 😉
BTW I recognize the image of the Burt Rutan’s Q2 at the top of the article. I almost built one. Maybe in another lifetime . . . 🙁
Wow. I just learned more about aerodynamics, avionics, batteries and electrical motors than any science book ever taught me.
I’m a total nincompoop about most of this technology, so I have nothing to add. Just a question, however. In theoretical future, larger electric planes, would fuel cells be a potential battery replacement? Or is that an over-promoted, dead-end technology?
A humorous suggestion is to add a little bicycle crank generator to the cockpit so you can pedal and add power to the batteries while you fly. You could get some exercise at 10,000 feet and add to your power reserve… 🙂
🙂
I’m guessing, but I’d bet that even if you were Lance Armstrong, you’d never be able to pedal enough to make up for the weight penalty.
Lance produces about 300 watts.
Which means I could do about 3.75.
this is interesting:
http://1.bp.blogspot.com/_ua8ycqfc4ok/SlymU76zHDI/AAAAAAAABoE/4QK-D3z4fyA/s1600/Tour+winner+power+to+weight.gif
What about using a fuel cell instead of a battery? There’s no need for it to be rechargable.
What about using a fuel cell instead of a battery? There’s no need for it to be rechargeable.
I don’t see any accounting for a bathroom there…
What else would you like? A galley with a microwave? A beverage cart? 🙂
Looks like a shake-up is coming at Powergenix, CEO just left this month. Better buy your batteries soon.
https://www.greentechmedia.com/articles/read/powergenix-loses-ceo-dan-squiller-to-gt-advanced-technology/
I would suggest taking along a really big rubber band as a back-up. Could be useful if you have to land somewhere without a recharging station.
That reminds me of the Rubber Bandit project. http://articles.latimes.com/1998/may/11/news/mn-48645
Does anyone know what happened to it?
How about considering some sort of ground tow to reduce battery cost at taxi and takeoff. I’d guess at the weight you’re targeting your take-off speed will be low.
Is there a temperature range you have to fly in for the battery efficiency to be sufficient for your mission?
I take it the cost of $10000 is for the whole thing, and not per flight. what do you anticipate as being the per flight cost?
Great idea!! Even better is that NASA has done all the work for you. Google “NASA” and “Puffin” and look at what pops up. No doubt exists that NASA will share all of their engineering with your team and if you ask them nicely, they’ll probably build the prototype for you in their workshops out back behind the Johnson Spacecraft Center.
I look forward to buying one of your electric aircraft and speeding over the miserable Houston traffic to my backyard landing pad. Thank you for starting this project.
Probably Bob isn’t actively looking at these postings anymore, but I’m surprised nobody mentioned solar paint. Sure, it provides little power, but if you’re going to paint it anyway, there’s really little downside other than cost. But since nobody is producing it commercially, you’d have to score some with some university friends probably for almost nothing anyway just for the publicity. Which reminds me, if you run out of money, you could probably get some crazy tech companies to front some by selling some logo space. Product placement! 🙂
I can see that inflight refuelling would be a little tricky for a lot of e-flight cases but how about some inflight DE-fuelling?
Make a suitable fraction of the battery pack into a parasite craft that attaches to the bottom, like a remora. Use cheap retail drone electronics (really, lots of gps related auto-nav stuff out there for modellers) to have said remora-batt return to launch point where it gets recharged for tomorrow. Have second remora-batt at destination – a rental market could be developed and you have your very own profitable eco-ecosystem 🙂
After take off and climb and reaching cruise, release the remora-batt and potter along on inboard power. Just possibly the energy budget might allow dropping the drag and complication of regenerative systems and give yo back the better glide performance. And if not, it’s a way cool Thunderbirds way of doing things. Gerry Anderson would be proud of you!
Will we be able to follow this project somewhere? Here?
I think the Runway Seeker VP-400 is just the avionics you need to optimize the glide. Contact Austin Meyer from X-Plane, its his idea, based on his fabulous sim software. He might support your project, his sim approach could result in spending your battery-power in the most efficient way. Maybe not only for the glide, but for the whole mission. Optimal levels depending on winds at altitude, climb profile, deviate to take advantage of some thermal activity, etc, etc. See his story at http://www.x-plane.com/x-world/hardware/seeker-avionics/ or the avionics implemantation of verticalpower.com/vp-400/
Good luck
Having a lot of experience with electric airplanes and regenerative charging (see AVinc.com) I can tell you that a flight propeller is a remarkably ineffiecient wind turbine….Our props are ~90% efficient but more like 10%-20% as a wind turbine to recharge batteries….
Oh and see if you can dig up any of the old Quicky Builders Association newsletters….They will be….educational….
Ping me if you want to talk about this…..
DaveG
Bob –
What about using a balloon to get to altitude? Those new lifting-bodies have a short takeoff, use little fuel, and take minimal personnel to launch/recover. Removing takeoff and ascent from the equation and you would have more of a safety margin.
Les Voitures…
[…]Electric flight of fancy[…]…
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