4 ms·

Airplanes are sadly not infinitely scalable in this way. If you attempt to naively scale up an airplane you need stiffer materials, eventually you run into the

Airplanes are sadly not infinitely scalable in this way. If you attempt to naively scale up an airplane you need stiffer materials, eventually you run into the issue of the weight of the structure increasing more rapidly than the area, and this is exacerbated by heavy batteries. We sadly cannot make large battery powered airplanes with a usable range and speed unless we get up the gravimetric density.

rsj_hn 5y ago
I don't think battery airplanes are going to be a big thing, but I think hydrogen powered airplanes could well be a big thing. It's certainly something I'd invest a lot of R&D into. Also, the airplane manufacturer business is ripe for disruption. You have an extremely bureaucratic and dysfunctional Airbus battling an even more dysfunctional and mismanaged Boeing. Surely there is room for a hydrogen startup to come in and devastate these two monopolies. Often I wonder how much the world would be different if we had 100 Elon Musks instead of just one.
- sudosysgen 5y ago
  I agree that hydrogen in airplanes has some potential, though there are certainly issues - you need cryogenic cooling to avoid super heavy pressure vessels, and if it fails..., but there are similar fuels that could work. As far as disruption, the issue is that there is no opportunity for competition. Countries are rabidly protectionist about their airplane industries, and any newcomer even with a completely superior product (See: Bombardier C-Series) will get absolutely destroyed by sanctions, tarrifs, or even secondary export controls (Gripen, Avro Arrow, etc...). You cannot succeed unless you are American, and even in America Boeing has massive undue influence.
  - rsj_hn 5y ago
    All true. I do think there is a window to succeed in the U.S. In Europe it's just much harder to innovate more generally. Also the SAFs are looking pretty good. Point is, I don't think we should decide that planes are bad of all sudden, that doesn't seem like a very wise thing to do given the massive benefits of air travel. Rail is also great but rail shines for cargo and large volume traffic between urban cores
    - hef19898 5y ago
      One of the fields that isn't true is civilian aerospace. Innovation cycles are long, regardless of country, regulations are more or less the same. Nobody only certifies according to EASA or FAA, everyone does both. And with Airbus and Boeing forming a duopoloy on civilian aircraft, both sides have equal interest, and funding, for innovation. Throw in all the current eVtol start-ups and I don't see that much difference between the US and Europe.
- dustintrex 5y ago
  Airbus and Boeing have plenty of competition in the smaller jet range: Embraer, Comac, Sukhoi, until recently Bombardier. If it was easily to scale up, it would have happened by now. I do agree that an electric/hydrogen jet is the kind of disruptive tech that could upend the market, but due to the long lead times, stringent certification and very political markets it's an arguably even tougher market than cars or rockets.
  - hef19898 5y ago
    Bombardier Aviation was bought by Airbus, Embraer almost by Boeing. Funny enough, there was always a lot more competition in the regional market then for bigger single aisle planes (B737 and A320).
Robotbeat 5y ago
No, this is false. The stiffness issue is a second order issue (which is why larger conventional planes actually have LOWER dry mass per passenger than 9 seat passenger aircraft) and IT AFFECTS ALL PLANE TYPES, and can be addressed via truss braced wings as I said. There are more important minimum gauge type issues at small scale that tend to dominate and make small scale worse performance than large scale. The claim that larger size in particular is a problem is false. Efficiency, including structural efficiency, actually tends to improve with scale beyond 100 seats. > We sadly cannot make large battery powered airplanes with a usable range and speed unless we get up the gravimetric density. This, again, is often repeated but false from a technical standpoint. 9 seater and 100 seater, for the same range, scale just fine between them and with clean sheet design we can use existing 200-400Wh/kg gravimetric density. Scale. Isn’t. The. Problem. Large planes tend to be used on longer routes, in fact. Smaller planes are needed for their granularity on short routes. The reason we see 9 passenger electric planes first is pretty obvious: cheaper and faster to develop small planes than large. Big aircraft manufacturers are much more risk averse as well. A large new clean sheet aircraft can take literally decades to develop. Not true for small aircraft. And again, generally the granularity of small planes means they’re more useful than large planes for shorter routes. This all reinforces the false notion that there is some technical reason why we “CAN’T” make large electric planes when there really, truly isn’t. For instance, consider the Learjet 70/75. 8 passenger, dry mass of 6 some tonnes. Over 700kg per passenger. 14 passenger Falcon jets do better at about 500kg per passenger. 737 Max8 with 210 passengers gets about 215kg/passenger. So if anything, overall structural efficiency improves with scale! At least up to ~200 passengers. (Caveat is that these are typically private jets with a different seating arrangement... but so are the example electric aircraft. So they'd similarly benefit from scale up to larger seat capacity.)
- sudosysgen 5y ago
  I think you seriously underestimate the mass of a 100 seater with 500 mile range. The 737 Max8 has a massive advantage over the LearJet of massively lower surface area per passenger. It's not comparable at all. In an electric aircraft where the bottleneck is the battery as far as weight goes this is not a relevant comparison. You have two regimes. One where the dominant factor is structural efficiency is mass. One where the dominant factor is area. You cannot compare the two. It is simply a completely deficient comparison. Do you want an actually correct comparison? Keep the 737 Max 8. Now compare it to a PAC P-750XL, dry mass of 1.6 tons over 9 passengers. That's 181kg per passenger, less than the Max-8. Now that's the aluminium version. The Max-8 uses a massive amount of composites - the composite version of the P-750XL is expected to be significantly lighter still. It's absolutely not a fiction. A 787 Max-8 consumes 18 liters (!!!) of kerosene at >60% thermal efficiency, per passenger, per hour. That's 175kW of useful energy consumption per passenger. To fly one hour at 400Wh/kg assuming 100% energy efficiency you need to add 437 kg of batteries PER PASSENGER.

rsj_hn 5y ago

I don't think battery airplanes are going to be a big thing, but I think hydrogen powered airplanes could well be a big thing. It's certainly something I'd invest a lot of R&D into. Also, the airplane manufacturer business is ripe for disruption. You have an extremely bureaucratic and dysfunctional Airbus battling an even more dysfunctional and mismanaged Boeing. Surely there is room for a hydrogen startup to come in and devastate these two monopolies. Often I wonder how much the world would be different if we had 100 Elon Musks instead of just one.

sudosysgen 5y ago
I agree that hydrogen in airplanes has some potential, though there are certainly issues - you need cryogenic cooling to avoid super heavy pressure vessels, and if it fails..., but there are similar fuels that could work. As far as disruption, the issue is that there is no opportunity for competition. Countries are rabidly protectionist about their airplane industries, and any newcomer even with a completely superior product (See: Bombardier C-Series) will get absolutely destroyed by sanctions, tarrifs, or even secondary export controls (Gripen, Avro Arrow, etc...). You cannot succeed unless you are American, and even in America Boeing has massive undue influence.
- rsj_hn 5y ago
  All true. I do think there is a window to succeed in the U.S. In Europe it's just much harder to innovate more generally. Also the SAFs are looking pretty good. Point is, I don't think we should decide that planes are bad of all sudden, that doesn't seem like a very wise thing to do given the massive benefits of air travel. Rail is also great but rail shines for cargo and large volume traffic between urban cores
  - hef19898 5y ago
    One of the fields that isn't true is civilian aerospace. Innovation cycles are long, regardless of country, regulations are more or less the same. Nobody only certifies according to EASA or FAA, everyone does both. And with Airbus and Boeing forming a duopoloy on civilian aircraft, both sides have equal interest, and funding, for innovation. Throw in all the current eVtol start-ups and I don't see that much difference between the US and Europe.
dustintrex 5y ago
Airbus and Boeing have plenty of competition in the smaller jet range: Embraer, Comac, Sukhoi, until recently Bombardier. If it was easily to scale up, it would have happened by now. I do agree that an electric/hydrogen jet is the kind of disruptive tech that could upend the market, but due to the long lead times, stringent certification and very political markets it's an arguably even tougher market than cars or rockets.
- hef19898 5y ago
  Bombardier Aviation was bought by Airbus, Embraer almost by Boeing. Funny enough, there was always a lot more competition in the regional market then for bigger single aisle planes (B737 and A320).

Robotbeat 5y ago

No, this is false. The stiffness issue is a second order issue (which is why larger conventional planes actually have LOWER dry mass per passenger than 9 seat passenger aircraft) and IT AFFECTS ALL PLANE TYPES, and can be addressed via truss braced wings as I said. There are more important minimum gauge type issues at small scale that tend to dominate and make small scale worse performance than large scale. The claim that larger size in particular is a problem is false. Efficiency, including structural efficiency, actually tends to improve with scale beyond 100 seats. > We sadly cannot make large battery powered airplanes with a usable range and speed unless we get up the gravimetric density. This, again, is often repeated but false from a technical standpoint. 9 seater and 100 seater, for the same range, scale just fine between them and with clean sheet design we can use existing 200-400Wh/kg gravimetric density. Scale. Isn’t. The. Problem. Large planes tend to be used on longer routes, in fact. Smaller planes are needed for their granularity on short routes. The reason we see 9 passenger electric planes first is pretty obvious: cheaper and faster to develop small planes than large. Big aircraft manufacturers are much more risk averse as well. A large new clean sheet aircraft can take literally decades to develop. Not true for small aircraft. And again, generally the granularity of small planes means they’re more useful than large planes for shorter routes. This all reinforces the false notion that there is some technical reason why we “CAN’T” make large electric planes when there really, truly isn’t. For instance, consider the Learjet 70/75. 8 passenger, dry mass of 6 some tonnes. Over 700kg per passenger. 14 passenger Falcon jets do better at about 500kg per passenger. 737 Max8 with 210 passengers gets about 215kg/passenger. So if anything, overall structural efficiency improves with scale! At least up to ~200 passengers. (Caveat is that these are typically private jets with a different seating arrangement... but so are the example electric aircraft. So they'd similarly benefit from scale up to larger seat capacity.)

sudosysgen 5y ago
I think you seriously underestimate the mass of a 100 seater with 500 mile range. The 737 Max8 has a massive advantage over the LearJet of massively lower surface area per passenger. It's not comparable at all. In an electric aircraft where the bottleneck is the battery as far as weight goes this is not a relevant comparison. You have two regimes. One where the dominant factor is structural efficiency is mass. One where the dominant factor is area. You cannot compare the two. It is simply a completely deficient comparison. Do you want an actually correct comparison? Keep the 737 Max 8. Now compare it to a PAC P-750XL, dry mass of 1.6 tons over 9 passengers. That's 181kg per passenger, less than the Max-8. Now that's the aluminium version. The Max-8 uses a massive amount of composites - the composite version of the P-750XL is expected to be significantly lighter still. It's absolutely not a fiction. A 787 Max-8 consumes 18 liters (!!!) of kerosene at >60% thermal efficiency, per passenger, per hour. That's 175kW of useful energy consumption per passenger. To fly one hour at 400Wh/kg assuming 100% energy efficiency you need to add 437 kg of batteries PER PASSENGER.