mdrejhon

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  1. Ugh, I made minor measurement-unit boo-boos in my original post that I didn't notice until "Edit Post" time limit expired. Such as "watts" vs "kilowatts" and "kilowatts" vs "kilowatt-hours" in a couple of sentences. However, the post remains exactly the same as before otherwise: Self correction: I meant 500 kilowatts-hours theoretical thermodynamic efficiency. My point was, rheoretically ask yourself: How the freaking hell can 500 kilowatts-hours-equivalent of liquid unleaded fuel be so well-matched by an 82-kilowatt-hour electric battery in a Tesla for exactly the same 350 mile car range!? Even aerodynamic efficiency differences of two compact cars don't explain that chasm (my Hyundai compact versus the 4680-based Tesla Model 3). Simply put, much of this from sheer efficiency of electric. What this leads, subsystem properly designed, electricity leads to a 5x-10x more efficient system (more "fuel" energy converted to actual useful work instead of heat) when all real-world losses are accounted for. This leads good credibility to that I heard that the equivalent of one near-max-weight trip to typical jump altitude consume a mere 50 kilowatt hours of electricity (give or take). Automotives don't directly translate to aeronautics, but electricity subsystems are generally more efficient in quite a large number of industries, and will likely translate very well here. You get the idea of sheer smaller-battery-requirement and the realisticness of that battery being smaller than a full fuel load. While battery is not practical for long hauls of A380 lore, the "one-jump-plus-30-min-reserve" battery is potentially perfect for jump planes once they pass the critical 400+ kWh/kg power density threshold. Here, I meant "watt-hours-per-unit-of-altitude-gain". That would be a more accurate phrasing, since that's a more important metric. Nontheless, most smart readers probably figured out what I actually meant and saw these obvious unit slip-ups.
  2. Yes, that’s another benefit of electric motors. With high efficiency and no combustibles / atmosphere requirements, there is far less temperature differentials too, to wreak havoc with materials. Biggest concern is cooling as even ballparks of approximately ~95 percent efficient on 500kW is still 25kW heat, but that is far less waste heat than a turbine, and most electric power needed is much less than that. Easily cooled by airflow of flight. Also, electric motors in factories are designed to safely operate well above boiling temperatures and the air cooling of 25kW keeps it in operating ballpark.
  3. Thanks. And @nwt do you have questions too? (Don't forget to pre-read my new reply first) Right. Just to point out; I never said "maintenance free". I did say various synonyms of "much less maintenance" or "lower maintenance". And that they don't require traditional engine overhauls. Many subway trains are running on original electric motors for more than 50 years, with a very low % of motor replacements for damaged motors/etc. Unless defectively designed, the electric motor component generally only require relatively simple maintenance (comparatively speaking) Sure you still have to maintain them (cleanings, lubricant maintenance, inspecting/refreshing the shaft seals, etc) but they generally don't require the extent of overhaulings that many petroleum motors require. With no gears and pistons, the majority of electric motors typically only has one moving assembly (rotor+shaft) and far fewer entries for external contaminants (e.g. dirt, sand, salty sea air, etc). With no pistons, tailpipe, extraneous orifices, fuel lines, for contaminants to leak in and foul up the system. Sure you have to worry about the shaft seal and applicable lubricants / protections, etc -- and other things -- but compared to petroleum subsystems, it is much simpler. (You can still damage the motor like cracked shafts or damaged rotor from a propeller strike during a crash, but let's put those things beyond scope of "maintenance"). Meeting FAA and Transport Canada maintenance requirements is much easier with ePlanes, since there is much fewer parts in an ePlane subsystem, and the individual parts themselves require much simpler/quicker/easier-to-detect maintenance. Wire wear and tear is probably even a bigger concern, you don't want cracks to show in wire coverings, potentially later leading to sparks etc. Inspection procedures will be required for that, but at least you're doing that instead of worrying about fuel lines and relateds. Yes, the maintenance intervals may be the same frequency (legal requirement) but thanks to the simpler maintenance, fewer moving/foulable parts, any legally-required maintenance to the fullest required extent is completeable in less time. Transport Canada and FAA needs to keep us safe, but even the higher-rigorousness (at the beginning) appears to be likely less human-hours of maintenance. So the total number of human-hours of maintenance is likely far lower.
  4. Or use those storage batteries to power the ePlane charger. There's some losses involved, but it eliminates battery-swapping overhead. And in theory -- those very same batteries could potentially be hand-portable (~50lbs-100lbs military suitcasey things with handles on them for two people to lift), to be used as dead-heading batteries for loaning the ePlane to other dropzones. You unplug the storage-batteries from the ePlane charger, put them into the hold, strap them down as cargo in the main cabin, to power an extended-distance flight between dropzones. When at the destination dropzone, these batteries are removed for the duration of the jump operations and trickle-recharged for a few days (the duration of the boogie / event). These are just cellphone-powerbanks-on-steroids. Those exist already for military uses, etc. and smaller versions already exist for camping uses, and it's expected they will scale to these sizes for aviation-industry convenience. Excellent data. This is generally a non-issue for electric engines. Amortized over the loads, that's a lot of money that doesn't happen on an ePlane. Any thermal stress (e.g. loosened cable connections that need to be re-tightened, etc) are a simpler maintenance matter. And lithium batteries are quickly plummeting in costs. I just heard recently a 10-gigawatt-hour lithium battery in Australia gets built. That's more capacity in one battery farm than an entire year's of battery manufacturing just about a decade ago (or so). The battery factories are strongly scaling up to terawatt-hour-per-year manufacturing. Specialized aviation batteries may remain expensive but even at ~25x-50x avation-markup of projected year 2030 cost ($62 -> $1500/kWh-$3000/kWh) would still be only $300K for a battery replacement once every ten+ years. That's not too shabby -- that's today's cost of an engine overhaul. The electric airplane motors never need overhauls themselves (just relatively inexpensive maintenance), so the overhaul expense is shifted to the battery pack instead -- and possibly less frequently. And could be even less, if the packs are more easily modular/removable, given potential future boom of approved aviation-battery suppliers. Probably beyond 2030 battery replacement -- even at aviation inflated prices -- will be much cheaper than that. So even the major maintenance expense (battery pack replacement every 10-20 years) becomes less cost than the cost of an turbine engine overhaul that is not needed for electric engines as they are good for far beyond life of the airframe. Now conversion prices are an open question, but as long as they are competitive to engine replacement, it likely becomes an attractive/viable option. And those batteries will still be good enough to be recycled as solar-storage batteries after no longer good enough for airplanes.
  5. Good data. Doing further research -- right now 0.41 Euro per L is pretty cheap, partially due to covid. The savings may not be as much fuel wise as expected if your Caravan only burns 60-70L for a full load to 13500 feet. Canadian/American jump tickets are closer to approximately 25-30 dollars per jump (Perris sells them between $25-$29 depending on quantity and discounts). But avgas is also cheaper per liter in North America (1gal = ~3.8L). Now searching down for prices, I'm seeing this. It's pretty clear (excluding maintenance savings) -- that 2020 fuel prices doesn't justify electric very well -- fuel is unusually cheap due to collapse of demand. That is mitigatable: - You only need to charge intermittently, rather than continuously - A ground-scale lithium power bank can help downscale the power utility connection. Suitable power banks are getting cheaper. - Local generation is also viable too (hangertop solar, etc) especially as these are getting incentivized/cheaper. - Some airports already have good supplies. Not all dropzones, but some of them already have the necessary supply. One would only need 1 candidate dropzone to be the first. You only need a few EV-vehicle-sizes' worth of battery to surge-output into intermittently charging a skydiving plane by perhaps X% (one jump's worth) using only a ~25% depth-of-discharge (the benchmark of shallow discharge needed for a decade(s) lifetime ground battery so you don't have to replace it after three years like a worn smartphone battery). One need only two or three true-EV-car-equivalents worth of ground lithium batteries (low few hundred kWh), to significantly downsize the necessary utility connection by 50% or more, depending on the charge:idle ratio of the electric airplane charger. Also, small airports can frequently have significant power supplies already, so cherrypicking the right airport can justify the business case automatically. It might not be for every airport (at first). It's not like a cheap electric vehicle -- an airplane is a much more expensive vehicle where a conversion makes sense sooner than for cars. In another industry, my local city (Toronto)'s regional transit agency, Metrolinx, decided to replace a gaspeaker plant plan with a lithium battery farm as the backup/UPS to power an upcoming electric subway called Eglinton Crosstown LRT. The subway was already under construction when they actually cancelled the gas plant and replaced it with a battery farm. Clearly, the economics suddenly clicked thanks to the scorching price drops. Now, to smaller-cost items such as airplane, which are durable assets that can last decades, conversions are always on the table versus re-enginings. Conversion cost has to be weighed against engine replacement too. There may come a point where conversion becomes economically feasible, and I expect that to be feasible by 2030s . This, I have some data (some confirmed, some unconfirmed), and this is where I need to ask for confirmations. A very fast lift to 13500ft at near max weight consume approximately ~50 kilowatt-hours for one electric airplane I heard about (not sure if it was a small one or eCaravan sized one) -- need to confirm as I obviously cannot parrot unconfirmed numbers in a Parachutist article. Also, thermodynamic efficiency of an electric airplane and without gears, is more than twice as high as a turbine. Electric motors routinely exceed 90% efficiency, while petrol motors are under 50% even before the gear loss (if any gears are used). So horsepower for horsepower, a lot less horsepower to reach altitude is needed -- one can throttle back the horsepower more for an electric to maintain a brisk climb. In some cases, efficiency apparently exceeds 3x for some power settings for the same amount of thrust. The best ones are a good Garrett engine at 50% efficiency, but many aged turbines are only 30% efficiency. I don't know what the PT engine thermodynamic efficiency is, but it's a lot less than a fresh new Garrett. Also the turbines is one-third less efficient at full jump altitude (give or take) than at ground. Electric motors don't degrade as it doesn't need the oxygen to burn fuel, only degradation from less air pressure. Also, over their lifetimes electric motors don't degrade quite like a turbine gradually does, and fuel mixtures can easily go suboptimal by maintenance issue more easily (i.e. 10% less efficient, here and there). And you have the additional gear inefficiency. When all of this combines up -- I wouldn't be surprised to see the ballpark of 1/3rd to 1/4th efficiency of a Magnix at full jump altitude is quite realistic. It's far less -- not sure if it closer to 1/2 as much or 1/5th as much -- but it's quite massively far less. They certainly remotely didn't need a significant fraction of 750hp of a Magnix to climb fast. Some questions to be added to interview... Now, optimizing for minimum-kWh-per-jump which takes a few minutes longer to climb than max-horsepower. Surprisingly less power needed if you're optimizing for the electric sweet spot from what I hear. Don't forget electric motors can remain far more efficient at nearly all speeds/torques, whereas a turbine has a sweet spot. So you have more range of adjustment -- pilot can adjust flaps a bit and rev up/down a bit -- to find a different sweet spot electrically than with a turbine, since you no longer need to optimize for the turbine's sweet spot to get the maximum actual climb power possible for a given propeller power. Instead, you're optimizing to the sweet spot of watts-per-altitude-gain, milking your electric motor's ginormous near-full-range sweet spot -- so pilot only need to focus on optimizing for aerodynamics. Which is still briskly fast even below maximum throttle; Now, we know 1 liter diesel is equivalent to 10 kilowatt-hours in theoretical efficiency. Real world is only 30% and that's before a lot of losses that aren't applicable to electric -- there's additional losses -- gearing loss, altitude loss, being away from sweet spot, etc. This is also consistent with the fact that a 50 liter gas tank only needs 1/5th to 1/10th the battery size for a similar range -- in a gas car versus electric car. Let's split the middle for automobiles -- a 75 kilowatt-hour EV battery versus a 50 liter gas tank (~500 watt-hours theoretical) for about the same driving range from full-to-empty. The new Teslas 4680s are enabling 350 miles on a mere 82 kWh (source). That's similar to the range of my 50 liter gas tank in my current car, so that gives you the automotive-industry comparision numbers -- 50 liters is theoretically almost 500 kilowatts of electricity in 100% pure joules laws-of-physics. But we don't get that efficiency out of fuel because of conversion losses. Now you're getting the efficiency-split idea, and battery-sizing idea. So seems 50 kilowatt-hour jump altitude is within a conceivable stone's throw. I might be off by double, but not by that much more. Assuming 50kWh, to consume only 33% per lift, requires a 150 kilowatt-hours battery. Let's be a bit more generous, and assume it's closer to 75 kilowatt-hours per lift, and we tighten the margin to say, 35%, we'll need a 200 kWh battery. Earlier 200 kWh battery of a decade ago -- at yesterday's power density 200Wh/kg weighs 1000kg, about 2000 pounds. A full Cessna caravan fuel load is ~2224 pounds (source). Now, the 4680 is already almost 400 watt-hour per kilogram. (380 Wh/kg, source) So today, we now already have a required battery half the weight of a full Caravan fuel load for a single jump load at 33% SoC discharge. But that assumes 50 kWh/lift. But if we're off by a lot and the power use is closer to 100 kWh/lift, we have to upsize the battery quite a bit, or wait for kWh to become better, then we'll need to wait longer for numbers to make sense. Nontheless, the real jump altitude numbers are well within the battery sizing ballparks & mass envelopes achievable. That said, it is true it is deadweight that eats into jumper capacity. So first conversion may have fewer jumpers, until battery efficiency improves. Also, it excludes potential regen recapture from the typical fast dive by a jump pilot (Let's say ~10% -- since the trainer regen recaptured up to 13%) but let's ignore that for simplicity. And energy consumption to 13500ft may go down too (for a dedicated airframe instead of a re-enginiing/conversion). Work is being done to keep increasing capacity; including 1000 wH/kg (NASA.gov 1440Wh/kg research as one example). Yes, we need the battery safety measures (shock absorption cage etc), which lowers the power density numbers somewhat. But it really truly seems the numbers are going to be able to check out well before the end of the decade even if we only improve a little bit more (to allow the battery safety structure weights). Now, a projection example -- imagine the numbers are correct or conservative and it's only 40 kWh per jump cycle after all said and done, and we want a 25% SoC per jump, then we only need 160 kWh battery for a 25% discharge. The remaining capacity (120 kWh) is more than enough for level flight of 30 minutes, we're simply shallow-SoC simply for battery-longevity consideration (a battery that lasts more than a decade). And let's say at 500 wH/kg by 2030 including battery-safety structures (crush zones, cooling, etc) -- 320kg battery or 700 pounds -- that battery now becomes between one-quarter to one-third a full Caravan tank (2224lbs). If we settle for 33% SoC cycling, the battery can be downsized even further, but I'm sure we rather see a 25% SoC for one jump just simply because of sheer safety margin -- for cold weather, for battery wear, etc. Then again, these numbers may be wildly optimistic. Nontheless it seems the venn diagrams certainly overlap into feasibility, even for the less promising numbers. I would like to supply a list of questions to Magnix CEO early next year for some Parachutist article, as even I make mistakes, but the battery capacity numbers definitely seems to be checking out for a "one-jump-load-sized" battery. Please supply additional "hard questions" that I could use to formulate interview questions to ePlane industry contacts (Magnix's CEO has offered to be interviewed for Parachutist) -- I welcome the hard questions. Even if that means downsizing some numbers. But obviously, it's clearly all looking promising.
  6. 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.
  7. 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.
  8. 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.
  9. 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]
  10. 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.
  11. 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)
  12. 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.
  13. 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.
  14. 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)
  15. ...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.