The little tech firm gunning for an airspeed record | Hacker News Reader

The little tech firm gunning for an airspeed record

bbc.co.uk

37 pointsm-i-l23 comments

> Electroflight's aircraft will need to sustain almost all of that power output for its entire record-breaking run - around eight minutes.

I'm sure this will be an amazing achievement but it seems to be a lot of effort for something that isn't that important - the problem with electric aircraft is endurance rather than top speed. The article seems to acknowledge that at the end:

> "For longer flights we are going to need hydrogen or alternative green fuels for a long time yet.

Not sure what you're trying to say? Light, dense and very powerful electric powetrains need to keep evolving. As we've seen there are very good use cases today for fully electric passenger planes, even for short flights and very good uses case for hybrid planes as well. It's the paramount aspect of electrification, it draws attention, saves weight and reduces costs exactly like battery tech innovations. The reality is that take off is very power intensive as well as other parts of flight. It's very very important.

Electric flight for commercial passenger service will never happen at commercial passenger scale.

Why? Energy density.

Lithium ion batteries store 0.8 MJ per Kg which is fifty three times worse than kerosene.

Before you say "oh well but battery tech is getting better every day" - NiMH, a technology now well over forty years old, is about 0.4MJ per Kg. Forty years of battery research has...doubled battery capacity per weight. What seems to be state of the art in commercial battery technology - LG's NCMA - is only about 15-20% ahead of what's in use right now.

It gets even more depressing when you realize that Lithium Ion is only barely getting to be one order of magnitude better than lead-acid batteries, a technology that has largely gone unchanged in over a hundred years. We need to have batteries that are a five-fold improvement from what lithium ion brought versus lead acid.

You also need a massive amount of power during takeoff and landing. GE's GE90 made about 18MW of power. The most current passenger get engine, the GE9X - produces thrust levels close to the original Soyuz rocket.

https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...

Kerosene hangs out along with other liquid hydrocarbons as the most energy per weight fuel available to us, around 43MJ/Kg. LNG is a bit better but still in the same ballpark; hydrogen is a three-fold improvement but is a net-negative fuel requiring far more energy to produce than it provides, and a royal pain in the ass to handle. It's safe because it dissipates so rapidly - but the shit loves to permeate everything. Including metal, which usually becomes brittle in the process, something severely incompatible with aviation.

Lithium ion battery packs? Barely coming off the Y-axis.

Oh, and the aviation industry can't even figure out "lithium ion battery packs for the electrical bus." Fires from said batteries in both Boeing and Airbus are surprisingly common.

The article didn't make mentions of commercial flights. The cool thing about electric drivetrains is that you can put this specific plane motor in a train... A GE90 is not a rocket engine, nor anything else. Electric powertrain densification, wether electrical, mechanical or electromechanical is a good thing for everybody on earth, similarly to how planes have allowed alot of us to go anywhere. Electric scooter, cars and bikes are helping millions get places reliably, quickly and economically with a clear advantage

"The cool thing about electric drivetrains is that you can put this specific plane motor in a train..."

Because clearly the railroad industry has been sitting around twiddling its thumbs going "man, how on earth could we make the electric motors we've been using for a century or so, better?"

Clearly an electric motor designed for coupling to a turbine or propeller at significant rotational speeds with low/no starting torque, typical lithium ion battery pack voltages, and optimized at great cost for weight....has relevancy for a train where weight and size don't matter, there may be almost zero airflow, the motor often needs to provide massive amounts of starting torque, etc.

The railroad industry uses multiple types of electric motors for different applications. The resources companies like Siemens have in refining railway and industrial motors are far greater. The notion that they need a bunch of morons developing a one-off speed record airplane to help them improve their motor tech is absurd.

"A GE90 is not a rocket engine, nor anything else. "

And what do you suppose the GE LM9000 is? Answer: the aeroderivative gas turbine version of the GE90. Aeroderivative turbines are used extensively in electric power generation and naval power applications.

Please stop talking.

Ge90 is not a lm9000 :) go to school

> The most current passenger get engine, the GE9X - produces thrust levels close to the original Soyuz rocket.

That's off by an order of magnitude. The GE9X produces about 500 kN, while the original Soyuz produced about 4.5 MN at lift-off.

Although I would pay to see a ge9x running on rocket proplant

It depends on what you exactly mean by rocket propellant. RP-1 is just refined kerosene and a GE9X won't really notice the difference.

Probably should have said soyuz rocket engine, my bad...though I guess it would have been more proper to say "one of the Vostok-K booster engines" of which there were four.

Or maybe GE is really stretching things and referring something other than the first stage engines.

https://www.ge.com/news/reports/its-official-guinness-world-...

“hydrogen is a three-fold improvement but is a net-negative fuel requiring far more energy to produce than it provides”

I am not sure how fair that is. Does that look significantly better for kerosene, if you have to construct it out of water and CO2?

As to take off, the power to reach take off speed could come from batteries that don’t move at all. A catapult as on aircraft carriers likely won’t be a good idea (requires stronger and thus heavier airplanes, acceleration will be ‘a bit’ on the large side), but electric trains can be powered at 500km/hour, so a third/first rail could work. I fear, though, most power is spent not on acceleration, but on lifting the plane to cruising height. That would make such a construction fairly useless.

Takeoff power is not only needed at takeoff. It is needed at go-around (if the landing is not working out) or in emergencies (what do you think will happen when 1/2 engines quits?)

Catapults address one of those cases, and you die in the other two. No thanks.

> Electric flight for commercial passenger service will never happen at commercial passenger scale.

I've heard it argued [1] that once we have proper carbon taxes, we'll see commercial electric flights on sub-250-mile routes like Denver to Aspen.

I agree that we're nowhere close to electric transatlantic flights, of course.

[1] https://youtu.be/aH4b3sAs-l8?t=456

We are nowhere near the battery tech to make this happen. That distance is 108nm, throw in the IFR departure/arrival, a hold due to sequencing, a missed approach due to weather, and we're looking at 180nm flown. Add in the flight time to the alternate airport, and the legally-required reserves, and we're looking at a required range of maybe 260nm. Do not forget that lithium batteries SUCK in the cold, so you'll also waste some power on heating them. We have no batteries right now that will take 100 people 260nm on a plane. We only have toy demonstrators that, with careful tuning, can take one or two people almost about that far.

I completely forgot about how immensely challenging it would be to keep the battery packs (and passengers) warm enough at the altitudes jetliners operate. Good point.

Similar to the soyus rocket? What numbers are you looking at? The old soyus weighed 700,000lbs and its engines could lift that. The GE90X is a toy by comparison at less than a fifth that thrust.

> You also need a massive amount of power during takeoff and landing

assuming a dedicated (specialised) takeoff/landing strip/apparatus - this could be solved by land-based assistance? Like (friken') lasers or something?

Already done with gliders via ground-based winches, which once "bootstrapped" with enough height and forward momentum are usually self-sustaining, but you have to be in weather conditions suitable for it - thermals and such.

It's wildly impractical at scale. It's not just takeoff, either. It's climb. There is no way to assist a flight up to 30,000+ feet.

For what it's worth, there are several EV aircraft companies going through the approval process as we speak to get their aircraft certified for human transport. These are not cross country flights. Most of them are trying to pick up the short distance "taxi" markets. i.e. office to airport, home to near-by ski resort, hotel to ski resort, home to office, etc... sub-60 minute flights. The approval process is long and most of these companies won't see human passengers until 2024 or later even if they get approved. Maker eVTOL is one such example. [1] United Airlines is also getting into this business. [2] Here [3] are 5 more air taxi's. Virgin and American have also been working on this effort for a few years. [4] I would expect the range to get a little bit longer with time, but by no means cross-country any time soon. Here [5] is a certified non-vtol EV LSA. Tesla will have one out soon and I expect it to have a longer flight time.

[1] - https://www.youtube.com/watch?v=5Rtoqs6BbCo [video]

[2] - https://www.youtube.com/watch?v=J797IZyAeRU [video]

[3] - https://www.youtube.com/watch?v=EXA6gQ2tchU [video]

[4] - https://www.youtube.com/watch?v=paC_eHwhmYY [video]

[5] - https://www.youtube.com/watch?v=uMrLHeKJA80 [video]

These are all carefully engineered marketing exercises built to extract investor/SPAC money, with little to no chance of ever reaching the market.

So, let’s set aside the commercial applications and just focus on general aviation for a second. Avgas, which fuels over 160,000 small planes in the US alone, contains lead [1]. Even if electric flight is only practical in the general aviation sector, it would remove one of the last remaining sources of lead pollution in our environment. A pretty big win all on its own.

[1] https://www.faa.gov/about/initiatives/avgas/

100LL is a scourge, I completely agree - but I think the sense of scale is off. 160,000 planes that spend most of their lives sitting on the ground? I just don't buy that 100LL is a significant source of lead pollution beyond people who work at airports. The pollution pales in comparison to just one single cruise ship or one coal-fired powerplant.

Anyway.

A fifty-times-worse energy density is fundamentally incompatible with most powered flight as we know it, including GA. I know I earlier said "it will never work for commercial aviation" but really, it's the vast majority of aviation. It comes down to planes only being attractive because they're fast and go far, or carry people/shit somewhere more easily than one can via ground.

Commercial aviation makes things possible that aren't as possible in GA due to efficiency from scale and volume. For example, turbine engines are very efficient during flight (they're horrible idling, which is why you see them run as little as possible when not in flight), reliable, light, and powerful. They require little warm-up time so they're great for "we gotta go NOW" (emergency services helicopters for example), shock cooling isn't a problem so they can fly descents piston aircraft can only dream about, and of course they excel at high altitude operation which leads to even greater efficiency. They also scale very, very well.

They are also mind-boggling levels of expensive to purchase compared to a piston engine. They run for long periods between needing overhaul but those overhauls are expensive. They're ideal for uses where that cost can be amortized over a lot of use/sales.

There is no benefit of scale for battery flight. There is no benefit to near constant use; lithium ion degrades rapidly with cycling.

What needs to happen is a phase-out of 100LL, which should have happened decades ago; there's already plenty of piston aviation engines running on unleaded gas, like Rotaxes. I'll be amazed if it ever happens, because the aviation industry are far, far too invested into ancient engine technology and AOPA is a very powerful owner and industry lobby.

Their insistence on duplicating everything about 100LL except for the lead shows nobody's actually interested in progress, but stalling progress. If they were interested in progress, they wouldn't be trying to perfectly duplicate 100LL or using government funds to further subsidize aviation, which is already massively subsidized.

What should have happened is the EPA should have said "you have ten years until 100LL is illegal to purchase unless you're a museum operating a historically significant aircraft for the purposes of public demonstration. You have until then to develop retrofit parts to make your engines compatible with commercially available 100 octane gasoline, parts which your customers can easily install during one of the several overhauls they will have between now and then." Fuck doing Continental and Lycoming's homework for them. The air-cooled piston aviation industry are a bunch of absolute dinosaurs who have seen little advancement in technology in close to half a century.

"The Electric NXT or E-NXT is a single-seater aircraft developed by Electroflight and the aerospace giant Rolls-Royce"

Not so little.

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