mdrejhon

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  1. The million dollar question is what “very short time” means. There are some lithium batteries, where upon short circuiting it, it takes a long time before it becomes a conflagration — the chemistry, the construction, etc. Whereas, others (some unprotected lipos) will just simply expand / explode almost right away. If you have any experience watching some of the battery tests of the more slow-cascading lithium battery designs, you’d realize that it is possible to design it in a way that it would take long enough before temperatures/expansions raised to structure-failure levels. There are designs that give enough time for landing before structural failure, at some cost of battery density. Lithium battery self-destruction rapidity varies all over the map. Sometimes a Tesla screen have displayed a warning more than half an hour before the first flames occurs; so there is some precedent to the ability to warn in advance of a potential impending battery fire as well; those are often reported more often than fuel fires which also happens to airplanes as well; (also consider many vehicle lithium batteries — not just Tesla — apparently has had way, way more active monitoring of all the battery sensors than the lithium battery in the first flawed A380 design). But yes, this will probably be a major item of FAA approval. The fire incidence must be acceptably low with a wide margin of safety for the public to accept electric aviation — both from a frequency perspective and also a warn-in-advance perspective.
  2. That's going to be a big purpose of advocacy. We need more accountants, pilots, mechanics, etc, working on this -- testing out scenarios, crunching the numbers, visiting Magnix, monitoring the news, etc. Then that way, I can shut up, and let everybody's numbers speak for themselves. P.S. (edit) One thing to keep in mind is that jump capacity scaleback, if any, is likely temporarily minor. For a "trial" it is probably only 1 electric jump plane at a major dropzone such as Perris or Deland. Preferably 2025 intead of 2030. By the time a whole jump plane fleet goes electric, it would be long into the 2040s or beyond where there is no longer notable capacity compromises.
  3. That's fair. Let's get more data over the coming months/year to back up this better. I agree that we need a lot more data. The other point I want to point out is it's not exactly that irresponsible to say this, is that at $6 per load, one can scale back the skydvers quite a bit to restore a lot of climb performance and then still make a profit. Still hugely more proftiable than a C182... A 9-person slightly-slower climb (11-minute instead of 8-minute) Electric Caravan could perhaps work just fine on dropzone accounting if the fuel-up is only a few dollars (whether $6 or $30). Yes, slower turnover than an avgas carvan that way -- but sooo much cheaper operationally when also considering the lower maintenance. The goldilocks spot is simply calculated by the cost vs time, which might turn out to be a number similar to that -- less than max load, but quite usable. Something that climbs fast enough with those Early Version 1 Jump Batteries. Which can be later be replaced in five years (in subsequent ePlanes, and in battery replacements in a decade) with a lighter Version 2 to increase jump capacity later. The improved profits can be saved towards such inevitabilities, in theory. By 2030 it looks highly probable that no skydiver-load-scaling-back is necessary.
  4. This is a good point. That said, keep in mind that battery fires start more slowly than fuel fires -- enough time for people to exit the car many minutes before exiting the airplane. Regardless, the design of a battery fire should be sufficient to allow the plane to quickly glide to landing before the battery fire consumes the plane. They will likely avoid lithium polymer (lipo) for an electric airplane because they can be more explosive. Most other lithium batteries (the Li-On ones used by Tesla) slowly heat up and smoulder gradually, so it would take more than 10-20 minutes of smoldering before fires. Design of a battery fire safety will be important. [replying to the other points out of sequence, keep tuned]
  5. Lithium batteries are already highly modular and this is probably a shoo-in feature. Left wing battery, right wing battery. (Ooops, forgive the political puns -- I know this ain't Speaker's Corner). Keep in mind that a Tesla car has more than 1,000 separate laptop batteries in it, and a charge controll activates/deactivates each and every one of them based on imminent failures. An airplane will need more partitioning/firewalling of this, but a large lithium battery is already automatically modular -- they just will have to tree-subdivide it appropriate for aviation: - Cell level & individual cell sensors - Pack level & individual pack sensors - Cluster level (cluster of packs) & their emergency cutoff switches It's only a simple architectural detail for modern large lithium batteries nowadays, as a simple subdivision matter. Three clusters is probably ideal -- left wing, right wing, and underfloor. The underfloor could be a reserve battery. Also, the Magnix motor can theoretically be used as generator for regen descents, recovering between 5%-10% of the energy. The electric trainer already can capture up to 13%, although student pilots find it scary to dive that deep. But jump pilots don't mind doing steep descenbts, so wouldn't mind a bit of regen (if the location's electricity rates are expensive). The kicker: The Magni500 consumed about $6 worth of electricity during the Grand Caravan’s 30min test flight, he adds. At those prices, we could essentially forget about regen. Even a 6-skydiver Caravan load can already be profitable -- since motor longevity is stellar, assuming good battery longevity. But by the end of this decade, I don't think we even need any capacity reductions.
  6. I'm not surprised. Weight is a super-fast moving target. It's not a problem to have a light battery but you want a long-lasting battery, so you need a great cooling system. A 750kW-output capable battery needs great longevity. The technology for such lonevity has finally arrived, but the devil is in the details. The point being -- supercar electric cars are already racing at sustained 750kW on the racetrack using a battery lighter than the fuel load of a fully loaded Caravan!!! The first megawatt supercars came out six years ago. (One megawatt = 1340 horsepower). Since then, they've finally found ways to sustain-output more than half a megawatt for many minutes (>10 mins) -- long enough for a jump lift! The "C" problem a solvable problem; the problem is making the battery longevity good through creative cooling systems and heat monitoring systems (Tesla has succeeded in durable 1C-3C batteries on the racetrack, but we need twice that for sustained Magnix operations). The Tesla battery has more advanced temperature monitoring and charge monitoring than the Airbus A380 battery does. It's quite dismal how Airbus designed that first version compared to Tesla did to their batteries -- several thousand temperature sensors & several thousand charge controllers -- in those older 18650-based Teslas. The safety industry standard is 1 temperature sensor per cylindrical battery AND 1 temperature sensor per battery pack, as a double-redundancy, and always leaving a healthy SoC at the top/bottom ends of the range. And a Tesla (original) consists of thousands of 18650 laptop battery cells -- so that's thousands of temperature sensors. The Tesla charge controller quickly isolates bad cells in a best-effort. Also, there were some major charge management mistakes done in the A380 batteries. Now Tesla's moved to 2170's and soon 4680's. Other battery manufacturers are finally copying the incredible battery monitoring breakthroughs that Tesla paved, and will be important for ePlane safety. It's amazing how beat-up Tesla batteries are; no wonder they catch fires (but less often than gas fires of gas cars). Airplanes are treated more gently than cars, not having to deal with shocks of potholes and curb-bumps as often -- so just like electric cars catching fire less often than gasoline cars -- but, yes, they need to design electric airplanes to catch fire less often than avgas planes -- for trust of the public. Given length of aviation approvals, it will take time, and one will have to migrate to safer lithium chemistries, and build enough safety margin. However, experimental trials should proceed sooner than later in preparation for the incredible economics of an electric jump planes so advocacy should begin sooner than later. We don't have to use Tesla batteries but we have to compliment the brilliance Tesla brought to the table for other lithium battery manufacturers. You can already cram the weight of 2 Tesla batteries including cooling weight equivalent (~200 kWh for 1.5 megawatt surge output, easily 750 kilowatt sustained) for the same weight as a fully tanked Caravan load. Obviously, we would use something else other than Tesla, as not as much cooling weight is needed due to cold altitudes -- but it all mathematically checks out already. Supercar batteries are often lighter for higher power output, since their longevity doesn't matter as much as a Tesla, I simply use Tesla as a gold standard since they're pretty long-longevity batteries. Now, power-wise, if we assume full max throttle 750kW for 8 minutes for a hurry-to-altitude, that will consume ~50% of a 200 kWh battery that fits within the weight of fully fueled caravan assuming we go by the latest weight data (lighter 4680 based architecture, under 2200lbs for 200kWh including water cooling -- unlike 2760lbs for the 18650 based architecture at 2x1380lbs for a Tesla P100D battery doubled-up). That leaves 100kWh for emergency reserve. This is only napkin math at this stage -- but it shows this is all really within a stone's throw already, with even the lower capacities. That's today's technology, only 200kWh per kilogram, including cooling. We haven't begun talking about tomorrow's 300-400kWh per kilogram implementations, yet. Consequently, I'm pretty confident a long-lasting jump battery is a very solvable jump lift problem before 2030 -- the writing is on the wall. Yes, the battery weight is a fast moving target due to many variables (chemistry, cooling, etc)
  7. On this point, I agree, more information from the industry will be welcome to execute better mathematics. Are there any pilots here that would be willing to help me run the mathematics on various types of battery packs (Tesla scenario, LiFePo4 scenario, current 250kWh/kg scenario, future 300kWh/kg scenario, future 400 kWh/kg scenario) I will get partial data from Magnix but because battery technology is an amazingly rapidly moving target (Thanks to Tesla lighting a fire under everybody who makes lithium batteries), we will have to do calculations separately on the hypothetical battery packs. On this point, I disagree it is inconsequential because the mass difference will become much more major as 2020 progresses towards 2030, as explained in three previous posts -- In a "Designbattery for one skydive + 30min reserve" scenario (between-jump fast-recharging), the amount of battery for one skydive will become smaller/lighter, as an increasingly tinier percentage of a fully fueled load. Yes, it will still be heavier than the equivalent fuel for one skydive (partially fueled plane), but regardless, a full or near-full flight with full load of jumpers should be achievable, in this "design for one skydive" scenario. The sufficiently powerful motor is already here, and there likely should be advocacy / trials even before the expected battery improvements that dramatically changes the mass savings. This isn't nuclear fusion perpetual "won't happen for another 20 years" fantasyland stuff.
  8. That assumes sustained average (steady highway speed, like level flight) A Tesla pack can discharge at approximately 5C to 10C in Ludricious acceleration mode, and typically discharges at 2C-3C during brisk acceleration starts by regular drivers. Yes, you heard me right -- a Tesla 100 kWh battery output more than half a megawatt! And that's using the laptop batteries they used before the 4680 battery. It's mainly the battery temperatures you have to worry about but the climb to altitude is short enough, with plenty of cooling opportunity afterwards during the descent. Teslas are also used at the racetrack now, with the Racetrack Package (on the existing battery pack), which allows sustained high-C operations far longer than a jump lift. Besides, Magnix already confirms that output is not the weak link for a fast climb to altitude. The descent also allows enough time for the battery to cool down before being charged, assuming the use of battery cooling mechansims including good heatsinking to the wings. The Tesla Model 3 Racetrack Package allows a Tesla to do sustained >1C output, typically 2C-3C output with automatic battery heat management -- color coded battery heat is shown on the screen during racetrack use. That's the same Tesla battery, unmodified. The Racetrack Mode pushes the battery very hard for much longer than a Magnix will need. For a faster climb, you will have to size the battery for more frequent sustained 750hp (500kW) to use the full power of the Magnix, but it's quite within the realm of today's batteries. A Cessna Caravan accomodates about 2224lbs of fuel. One Tesla battery pack (capable of 750 kW surge output) is only 1000lbs-1400lbs. (List of Tesla battery weights, including cooling systems). The older P100D (100kWh) battery pack was 1380 pounds using the laptop 18650 batteies capable ot outputting half a megawatt aggregate in Ludricious Mode -- but the 2170 battery based ones were lighter, and now newer Tesla 100kWh batteries using the 4680s are reportedly far closer to 1000 pounds for 100 kilowatt hours including cooling. Obviously, it is not an apples-vs-apples, but the point being is -- batteries lighter than the fuel load is capable of fully powering a Magnix motor -- including the weight of water cooling. Now that specific doubt out of the way: If they design to instead heatsink to the airframe with a bit lighter water cooling, then some weight savings can be had, given the higher airspeeds of colder air at altitude (precisely where the battery begins to heat up -- a while after takeoff and on a fast climb to cold altitude). Perhaps it pushes today's batteries hard, but 750kW is definitely within the envelope of "Tesla style" battery architectures -- though one may want to upsize by 2x while including the water cooling that Tesla battery packs use -- to allowed about 5 minutes of sustained 750kW. But even airplanes don't always sustain maximum horsepower for 100% of the climb, as pilots often taper that of a bit after the takeoff roll, for turbine longevity purposes (so not all 900hp is all in use for the entire duration of climb to altitude). But you see, the "C" problem is already actually mostly solved -- however, battery longevity might be down (e.g. like maybe too few flights -- i.e. only 3-5 years of flights) until upsized a bit -- though the improvements made by 4680's longevity and other similar lithium battery technologies by others (competitors propelled by Tesla innovations). One problem is that Tesla is a bit ahead of competitors in charge management and battery heat management. It's a bit hard to get large off-the-shelf lithium batteries that can charge/discharge as fast as a Tesla battery (multiple C) without longevity-shortening effects. With the great battery management they use to detect and isolate bad cells within packs -- the Tesla battery management systems behaves like many thousands of concurrent battery chargers. Such technology is now being introduced into other batteries The cooling tech is part why batteries last longer in many electric cars longer than the batteries in R/C airplanes. That said, battery technology is improving extremely rapidly. Over the course of 2020-2030 will solve any remaining "C" problem (heating, cooling, supercharging, easier to downsize battery, etc) of a one-skydive-sized battery that doesn't need to be bigger/heavier than it needs to be. However, the suitable jump plane electric motor is already here, and it should be tested/experimented by pilots for simulated jump ops. Tests can be done while the skydiving world awaits jump operations. See my Advocacy post.
  9. I never said that -- you remember incorrectly: Scroll back to the post, and re-read: "That battery, today, already appear to weigh less than a full fuel load, for some aircraft specifications" So repeating the points: We only need between-load recharging of the batteries between loads; We only need one skydive's worth of batteries, plus 30 minutes reserve; Yes, the partial-batteries will weigh more than the equivalent partially-fueling; However, the partial-batteries will weigh less than a fully fueled airplane. For more concrete numbers, there are questions I need to ask the electric aircraft makers. Roei (CEO of Magnix) has agreed to be interviewed for the Parachutist electric jump aircraft article I want to collaborate on -- so before I send them, I have to discuss with co-authors if they're good questions. Don't worry, I won't be publishing anything unsubstantiated in that article. (Additional coauthors and proofreaders welcome, contact me)
  10. ...I should also add that the fuel weight lightens as you burn, the battery weight does not. But the efficiency gains over the short time period of getting to altitude are apparently significant enough to overcome that variable. It is a big factor for longer flights, rather than the few minutes to altitude where plane lightening is often only essentially a low single-digit percentage of plane total mass, and in many cases under 1% for some fully loaded airplanes. For the short 8 minutes to 10 minutes to altitude, plane-fueload-lightening is sufficiently small enough (as % of plane mass) that the sheer efficiency of an electric plane motor wins out, by affording pilot more flexibility to milk the airframe/prop settings instead. A turbine can go much less efficient at certain airframe settings despite being physically airflow efficient, but RPM/torque inefficient for the turbine (burning more fuel). Thus, the goldilocks airframe/prop settings range is smaller on the same airframe for a turbine than for an electric re-engining on the same airframe. The electric stays efficient at a wider range of torques & RPMs, so you can work the propulsion efficiencies more physically (pitch, flaps, etc) than worrying about hitting the motor-efficiency sweet spot. Worry about milking the laws of physics of your airplane, more than worrying about fuel buen. The efficiency gains of optmium settings far exceeds the 1% airplane mass lightening from fuel load burn over the short timescales we’re talking about. We lose out over avgas for longer flights, but this becomes a mathematical win-win for jump operations which are just short flights. The assumption made for longer flights is silly as the sheer shocking short-flight efficiency of an electric flight wins out. So battery deadweight is far less of an issue for a smaller 1-skydive-designed (+30min reserve) battery than for trying to mimic a fully 100% fueled airplane.
  11. Scientific fact: It’s worth noting — ignoring airplanes — that the energy required to lift a mass X against gravity Y from height A to B — is mathematically a fixed amount of energy in the ideal case regardless of the velocity of lift from altitude A to altitude B. Things like friction (air friction, water friction, rolling friction, etc), acceleration/deceleration differences (at beginning/ends of the gravity journey, if acceleration energy is not recaptured), and also motor efficiencies make the gravity-lift math less ideal. Also, for simplicity, we can effectively ignore gravity gradients (high altitudes have a tiny bit less gravity) or theory of relativity as they are not meaningful error margins at current physical speeds and current altitudes being discussed. Now in the case of airplanes — improve the variables (e.g. efficient flexibility of motor at all power settings) so absolute airframe & propeller efficiencies can be better milked. A plane cannot solve all weak links breaking the ideal (friction is always with us) but it also explains the concept of less battery differential versus fuel differential — getting a tiny bit closer to the ideal formula dictated by laws of physics. This may not be significant for some airframes but is more for others, but regardless, it’s generally possible to achieve a smaller consumption difference (% difference of slow-vs-fast altitude gain) for an electric for a given altitude gain A to B on the exact same airframe.
  12. (re: noisefloor = I meant “lost in the midpoint of the varying time-to-altitude statistics of all dropzones worldwide”. I should not have tried to summarize that into one word, apologies) For the specific 10%-20% (yes, wholeheartedly unscientific estimate) is based on previous world experiences in other electrifications — electric cars, radio control airplanes, etc. They drive similar speed and fly similar speed and climb similarly performant at similar weights. In lots of cases, the electrics outperform in raw performance (witness the electrics beating petrol speed records in some domains). Also, skydivers will become impatient if the plane climb noticeably slower than other planes in the fleet. 10% slower climb isn’t really noticed by everyone in the load, but a 50-100% slower is definitely noticed by the whole load. But here’s some scientific observations, that actually brings credence to the point I’m making: The math is a sudden viability line: Change the battery numbers a bit, and things suddenly go from “Can’t meet MTOW” to “I can fly quickly to full jump altitude”. Given the small envelope of a single jump lift, the fuzz region is actually much smaller than many people think, since a slow-vs-fast climb isn’t that terribly a large watts-hour delta in the Magnix tests (you consume less power but consume longer ... It is less variable in “power-consumed-per-foot-gain-of-altitude” with electric than with avgas, simply by virtue of the electric motor being efficient at all RPMs. (Yes, you have to correctly set your flaps and optimal prop pitch and all, to avoid wasting power in an inefficient climb, but once optimal, it is more balanced than for avgas. A slow optimal climb vs fast optimal climb isn’t as much battery watt-hours consumed differences as the fuel-consumed differences because of the efficient-at-all-RPMs behaviors that make it easier to dial the optimal climb. Putting more of the motor’s energy more efficiently into the climb — Turbines are most efficient at a specific settings, while electrics are efficient at nearly all settings, giving pilot more flexibility to focus more on adjusting the plane’s surfaces to optmium prop/airframe settings, rather than optimizing the plane to meet the efficiency at the performance settings of a specific turbine motor. So, the slow-vs-fast climb matters less since it’s a fixed altitude gain, you’re paying energy a more stabilized amount of energy per foot of gain, you’re paying energy a more stable amount of power for a given altitude gain, thanks to the brilliant efficiency of the electric motor in virtually its entire performance range. There is still a difference (it’s not linear) but the watt-hours difference is not as big as the fuel difference of a fast-vs-slow climb. For the first plane, if it climbs too slow, you remove passengers or wait for battery tech to become viable. The power difference of a fast climb versus slow climb from altitude X to Y (0feet to 13500feet) isn’t going to double the battery size. The napkin numbers are touchy: A minor improvement in battery tech suddenly allows the electric airplane to have no disadvantage. The “fuzz” between not practical and suddenly fully practical (at no climb performance degradation or jump capacity loss), is actually rather a tight twilight zone that may last only a few years, possibly only a year. So the moral of the story is when the battery gets good enough, it only needs a little more refining to quickly zero out the remaining performance-related disadvantage. But a dropzone will bite the ePlane bait a bit before that, i.e. tolerate a 10-20% climb performance decrease to decrease the size of the battery, to gain the other advantages (like major cost savings). But yes, replace the “10%-20%” unscientific numbers with your favourite low-percentage threshold where somebody bites the ePlane carrot. I would bet DZOs also won’t bite at 100% slower climb performance. That’s what we saw happen in other electrifications. Anyway, the point being is that the tech fuzz zone between “Not practical” and a “ePlane climbing at full velocity to jump altitude” is actually shocking small, because of the reasons above described. Improve the tech just enough and — bam — it’s practical without a compromise. If we’re going to have compromises, it will only be very short-term like removing 1 or 2 or 3 passengers to meet volume/weight envelopes, but only for as long as battery tech improves even a few percent in a “we-only-need-a-battery-for-1-skydive-plus-reserve” scenario. Anyway, I just heard back from Magnix CEO he’d be happy to be interviewed for the Parachutist article. Now to formulate the right questions. (which may also answer some of these questions too, as well as correct any details in some of my answers, I’ll admit to being wrong sometimes. But really, there are a lot of details people don’t realize about electric motors, like “high-efficiency-at-all-power-settings” behaviors).
  13. True, but that may not be a problem — it assumes the lighter motor & other factors don’t fully cancel-out. Also — depending on plane — many dropzones don’t always absolute-max throttle their jump ship. Backing off a bit, especially after takeoff, to a mutually-agreed redline indicator on the dial, for climb performance that makes it easier for the airplane maintenance department & dropzone accountants for avgas consumption. Some do push it beyond, especially if you’re trying to push loads fast on a busy day, but that can be brutal on the engines of some planes if you’re near the performance envelopes. In reality, if slower, we are probably nitpicking only tiny percents (e.g. 10% or 20% slower climbs for same plane type) which is within the noise floor of the jump ship variances between dropzones. And even that assumes we’re using today’s batteries, not tomorrow’s. Fortunately, from the early tests, it already looks like we’re not going to be seeing 22-minute Cessna 182 style climbs with electric airplanes.
  14. Actually, probable reduced flight time. The Magnix can actually climb to altitude faster than the original turbine because you don’t worry about the redline as much — the battery difference between a slow climb and fast climb isn’t too terribly major for the current small envelopes asked of a 1-skydive battery sizing. At full 750hp throttle, a >93% efficient Magnix generates only 35 kilowatts of waste heat which is easily cooled by sheer airspeed, and I heard it climbs more vertically than a 900hp for the same weight because of less HP loss (direct shaft drive, no differential). But yes, the extra battery weight may cancel this out. Battery heating is also a factor but the quick climb moots this out; electric car have output more wattage than a Magnix doing a full Nurburgring Loop in Germany. For practical purposes, I expect no difference between turbine and Magnix electric for a typical jump plane climb. HP for HP, electrics can outperform avgas, as noticed by R/C hobby airplane pilots. Electric R/C airplanes perform spectacularly. Sure, the battery capacity is an issue, but you only need to size for a fast climb for 1 skydive load + 30min level flight reserve, which will still weigh less than a full fuel load. The kWh per kilogram may need to improve a bit more, but that’s just details from 2020-2030 at this stage — the fast climbing electric jump motor is already here...
  15. True in that this “seems” more apples vs apples. On the other hand, a Magnix electric direct drive engine (297lbs) is smaller and weigh less than the original turbine (of apparent lesser performance, despite same or slightly higher horsepower). And a lot less than piston engines and older turbines (and their respective gearbox/differential that are no longer needed thanks to gearless direct drive). This frees up a portion of weight for the minimal 1-skydive fast-10min-charge battery + 30min reserve flight capacity, with potentially zero loss of skydiver passenger capacity. The battery undoubtedly will weigh more than the fuel load of one skydive, but looks like a one-skydive battery can still now fit within max-takeoff with a full load of skydivers. Extra “fuel” weight is vastly far more than compensated by the massive cost savings. ($300 of avgas cut by 90% to 98% in cost to just $6 to $30 depending on your commercial electricity rates) (DZO accountants.,,. yes..... potentially under $1 “fuel“ per skydiver to 13500 feet!!!!) With the good instant rev torque that Magnix-trying pilots go wow at — even a near-MTOW load does not feel as dicey as with in a turbine. I think the napkin math is starting to look impressive this decade.