3 ms·

A NASA Engineer Discovered a World of Semi Truck Aerodynamics by Accident

61 points by PaulHoule 9mo ago

amelius 9mo ago
> would increase fuel economy by 15-25% Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.
- n4r9 9mo ago
  Those figures are from the 1970s, when presumably there was a lot more low-hanging fruit. Still, I wouldn't be surprised if they invest a decent chunk into computation aerodynamical work as part of their body design.
  - roysting 9mo ago
    You’re also touching on a rather large ignored issue in this article, that this NASA truck aerodynamics project was directly connected to the 1973 oil crisis and a government wide effort to reduce oil consumption, not just some epiphany by some guy on a bike.
    - irishcoffee 9mo ago
      Both can be true. Sounds like the classic: necessity is the mother of invention I don't understand why you put such a negative spin on this. Who loses when trying to become more energy efficient?
- cucumber3732842 9mo ago
  They absolutely do design trucks for aerodynamics. Fuel economy is a huge avenue of competition for semi trucks. The reality is just that with the drive cycles and costs and tradeoffs of implementing all this it's not worth it to go this far. Second, this sort of "round the whole thing" approach has mostly been replaced with "the simulation says we can do a 90/10 if we just do X, someone print up a block and toss it in the wind tunnel and see how it does" type approach so the result tends to be more surgical modifications and use of dead air and less "smooth out the whole thing with fairings".
  - embedding-shape 9mo ago
    > They absolutely do design trucks for aerodynamics I know next to nothing about trucks, and vehicles in general, but something I've noticed, and probably everyone else, is that trucks in the US looks very different from trucks in Europe, it's very easy to identify which one is a US-like truck vs a Europe-like one, because of the shape of the "cab" or whatever that part is called. So one design has to be clearly better than the alternative, given that aerodynamics works the same all around the world, but still the designs are uniquely... unique. But why is it like this? If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now, or are they truly equal in terms of aerodynamics?
    - pjc50 9mo ago
      Did a bit of research: https://news.ycombinator.com/item?id=47121031 https://news.ycombinator.com/item?id=47121031 - different countries have different legal requirements, despite air being the same everywhere.
      - embedding-shape 9mo ago
        Judging by the images only, those are all the ones I called "European" trucks though, the American ones are much longer. Is that also regulated so European trucks aren't allowed in the US and American ones aren't allowed in Europe? Because here in Europe it's really uncommon to see the US ones, and I'm guessing it's the opposite in the US? One of them must be better aerodynamically though, must'n it?
        masklinn 9mo ago
        Europe has length limits on the entire thing, so US trucks would require shorter trailers, which nobody really wants. Euro trucks also have significantly smaller turning radii, which makes navigating european cities and country roads… feasible. Furthermore Europe has relatively strict speed limits on trucks, which makes aero something of a lesser factor since drag grows to the square of speed: european trucks at european speeds have a pretty significantly higher efficiency than US trucks at US speeds.
- quickthrowman 9mo ago
  They do, look for some semi-trucks on long haul routes, they have trailer skirts and/or trailer tails.
- mapt 9mo ago
  Part of the issue is the extreme constraints imposed on designers by road regulation, another is simply that the majority (75%?) of drag reduction is in a fishtail that needs to go on the container, the part of the truck that gets left behind at the loading dock, that is often not "owned" by the person who owns the truck.
- trashb 9mo ago
  Because the individual logistics companies are not developing the trucks. The aerodynamic properties of a truck are mostly determined by the model/brand, and this is a huge consideration at companies like Scania, Volvo or Mann. Not so much at the individual logistics companies.
pjc50 9mo ago
Bit of googling suggests this is a whole, fascinating world of little improvements. However it's also both constrained and pushed forward by what's road legal. https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2025/may/behind-volvo-trucks-latest-updates-in-truck-aerodynamics.html https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2... : removing mirrors allows for much smoother cab airflow https://go2stream.com/blog/aerodynamic-truck-legislation-ready-to-improve-fuel-efficiency-reduce-emissions-and-improve-road-safety-in-the-uk/ https://go2stream.com/blog/aerodynamic-truck-legislation-rea... : UK legalization of fishtail-like devices https://www.kudauk.ltd.uk/aerodynamics-explained https://www.kudauk.ltd.uk/aerodynamics-explained : Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab. I'm sure there's a lot more out there. The eventual switch to electric will probably come with another round of aerodynamic improvements to maximise range, as with cars.
- trashb 9mo ago
  > removing mirrors allows for much smoother cab airflow On brand new trucks (designed without mirrors) yes. However on older trucks the mirror design might be an essential part of the aerodynamic design and required for a low drag coefficient.
- masklinn 9mo ago
  > Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab. Cab-top deflectors are extremely common on every truck where the cab is not tall enough to cover a standard trailer (which is common, usually only the highest end sleepers are that tall e.g. Scania's highline cab on the R and S, Volvo's globetrotter xl and xxl, ...) For instance on this hero image from scania's site every truck but the very shortest and the very tallest have a deflector: https://www.scania.com//group/en/home/products-and-services/trucks/_jcr_content/root/responsivegrid/responsivegrid_copy/responsivegrid/heroimage.coreimg.85.1920.jpeg/1585221957546/18317-001.jpeg https://www.scania.com//group/en/home/products-and-services/... Obviously if you run higher than standard trailers, you need a custom deflector.
svilen_dobrev 9mo ago
also check Luigi Colani's quite bold designs: https://www.colani.org/luigi_colani_Product_design_museum/Trucks.html https://www.colani.org/luigi_colani_Product_design_museum/Tr...
- netsharc 9mo ago
  Meanwhile in Hollywood: https://www.fortressofsolitude.co.za/the-highwayman-reboot-the-worlds-coolest-truck-should-return/ https://www.fortressofsolitude.co.za/the-highwayman-reboot-t... In one episode the helicopter actually detached and flew!
jcgrillo 9mo ago
Another development in trucking efficiency that seems really interesting is the Achates opposed piston two stroke. If their materials are accurate, through fluid modeling they've achieved a massive efficiency boost and emissions exceeding regulatory targets without urea injection. In a piston ported two stroke. https://www.ccjdigital.com/regulations/article/15291029/achates-nearzero-diesel-fighting-for-production https://www.ccjdigital.com/regulations/article/15291029/acha... This is the most recent news I can find about them, though, so unclear if these engines will ever be produced for road vehicles: https://www.govconwire.com/articles/ga-asi-david-alexander-achates-power-opposed-piston-engine-tech https://www.govconwire.com/articles/ga-asi-david-alexander-a... See also: https://achatespower.com/resources/ https://achatespower.com/resources/ I was hoping we'd see these engines running generators in Edison trucks one day.
mikeayles 9mo ago
As someone who works in commercial fleet fuel economy (powertrain, not aero, but you keep an eye on the whole stack since technologies compound), it's worth noting how far the industry has moved since the 1970s NASA Dryden work. The sheer amount of "snake oil" bolt-on products sold to fleets in the 90s and 00s means the industry now demands rigorous third-party validation. The best open source testing I've seen comes from Mesilla Valley Transportation Services (https://www.m-v-t-s.com/certified-technologies/ https://www.m-v-t-s.com/certified-technologies/). They don't rely on ECM dashboard readouts or pump receipts. They run a control truck and test truck simultaneously on a track or controlled highway loop so weather, air density, and wind are identical. Anemometers on the trucks algorithmically factor out wind speed/direction, tyre temp, and weight. Tests are designed to answer the actual question rather than tick a standard's boxes. Their chief test engineer was ex NASCAR, IndyCar and F1. My team actually tested a dual-fuel system with MVTS. The engineering was sound, testing proved a slight thermal efficiency improvement, but cheap US diesel versus the cost of the alternative fuel meant the ROI was non-existent. The physics worked, the math killed the project. (The economics work in Europe, thankfully.) A lot of what's being discussed in this thread is already standard too. Mirrorless cabs are more the rule than the exception now (as pjc50 linked above), close-coupled trailers with gap fairings, wheel covers, under-trailer aero, all commonplace. A couple of current ones worth knowing about: the Scanias with the "Super" powertrain run a really aggressive overdrive at around 900rpm at the 90km/h (56mph)EU limit, where a conventional truck sits around 1200rpm. Requires huge low-end torque but claims 5-8%. The Mercedes Actros L claims 3% from its slippery front end alone. It is absolutely hideous though, so make of that trade-off what you will. The biggest factor though is driver variability. All the aero and powertrain hardware in the world doesn't matter if the driver thinks they are the stig. The biggest shift in the last decade has been removing human inconsistency from fuel economy entirely. Automated Manual Transmissions are now completely dominant in modern fleets. They shift perfectly for fuel efficiency every single time, totally capping the penalty of a bad driver. Layer on top of that Predictive Cruise Control. Modern trucks use GPS and 3D topographical maps to "see" miles ahead. The truck's computer knows exactly when to back off the throttle before cresting a hill to coast over the top, and exactly how much momentum to carry into the next dip. A human driver relying on their eyes simply cannot compete with a powertrain that knows the exact gradient of the road three miles ahead.
trashb 9mo ago
I don't know too much about the USA side of trucking but in the EU the cab over trucks have been able to steadily improve their aerodynamics, and there has been a lot of effort into improving this. Obviously there is more frontal area compared to a passenger car but comparatively modern EU trucks are quite aerodynamic. (even though they may not look it) There are other things to consider as well when building a truck, as mentioned the maximum length limits, comfort, power price and more.
cestith 9mo ago
One of the comments on the original article plays aerodynamics off as unimportant, saying only up to 0.4 miles per gallon difference. Even if that number was true, this is an industry that gives drivers patches on their shirt or hat for averaging above 7 miles per gallon of fuel for the year. An extra 0.4 miles out of every gallon is insignificant at all.

61 points by PaulHoule 9mo ago

> would increase fuel economy by 15-25% Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.

n4r9 9mo ago
Those figures are from the 1970s, when presumably there was a lot more low-hanging fruit. Still, I wouldn't be surprised if they invest a decent chunk into computation aerodynamical work as part of their body design.
- roysting 9mo ago
  You’re also touching on a rather large ignored issue in this article, that this NASA truck aerodynamics project was directly connected to the 1973 oil crisis and a government wide effort to reduce oil consumption, not just some epiphany by some guy on a bike.
  - irishcoffee 9mo ago
    Both can be true. Sounds like the classic: necessity is the mother of invention I don't understand why you put such a negative spin on this. Who loses when trying to become more energy efficient?
cucumber3732842 9mo ago
They absolutely do design trucks for aerodynamics. Fuel economy is a huge avenue of competition for semi trucks. The reality is just that with the drive cycles and costs and tradeoffs of implementing all this it's not worth it to go this far. Second, this sort of "round the whole thing" approach has mostly been replaced with "the simulation says we can do a 90/10 if we just do X, someone print up a block and toss it in the wind tunnel and see how it does" type approach so the result tends to be more surgical modifications and use of dead air and less "smooth out the whole thing with fairings".
- embedding-shape 9mo ago
  > They absolutely do design trucks for aerodynamics I know next to nothing about trucks, and vehicles in general, but something I've noticed, and probably everyone else, is that trucks in the US looks very different from trucks in Europe, it's very easy to identify which one is a US-like truck vs a Europe-like one, because of the shape of the "cab" or whatever that part is called. So one design has to be clearly better than the alternative, given that aerodynamics works the same all around the world, but still the designs are uniquely... unique. But why is it like this? If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now, or are they truly equal in terms of aerodynamics?
  - pjc50 9mo ago
    Did a bit of research: https://news.ycombinator.com/item?id=47121031 https://news.ycombinator.com/item?id=47121031 - different countries have different legal requirements, despite air being the same everywhere.
    - embedding-shape 9mo ago
      Judging by the images only, those are all the ones I called "European" trucks though, the American ones are much longer. Is that also regulated so European trucks aren't allowed in the US and American ones aren't allowed in Europe? Because here in Europe it's really uncommon to see the US ones, and I'm guessing it's the opposite in the US? One of them must be better aerodynamically though, must'n it?
      - masklinn 9mo ago
        Europe has length limits on the entire thing, so US trucks would require shorter trailers, which nobody really wants. Euro trucks also have significantly smaller turning radii, which makes navigating european cities and country roads… feasible. Furthermore Europe has relatively strict speed limits on trucks, which makes aero something of a lesser factor since drag grows to the square of speed: european trucks at european speeds have a pretty significantly higher efficiency than US trucks at US speeds.
quickthrowman 9mo ago
They do, look for some semi-trucks on long haul routes, they have trailer skirts and/or trailer tails.
mapt 9mo ago
Part of the issue is the extreme constraints imposed on designers by road regulation, another is simply that the majority (75%?) of drag reduction is in a fishtail that needs to go on the container, the part of the truck that gets left behind at the loading dock, that is often not "owned" by the person who owns the truck.
trashb 9mo ago
Because the individual logistics companies are not developing the trucks. The aerodynamic properties of a truck are mostly determined by the model/brand, and this is a huge consideration at companies like Scania, Volvo or Mann. Not so much at the individual logistics companies.

pjc50 9mo ago

Bit of googling suggests this is a whole, fascinating world of little improvements. However it's also both constrained and pushed forward by what's road legal. https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2025/may/behind-volvo-trucks-latest-updates-in-truck-aerodynamics.html https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2... : removing mirrors allows for much smoother cab airflow https://go2stream.com/blog/aerodynamic-truck-legislation-ready-to-improve-fuel-efficiency-reduce-emissions-and-improve-road-safety-in-the-uk/ https://go2stream.com/blog/aerodynamic-truck-legislation-rea... : UK legalization of fishtail-like devices https://www.kudauk.ltd.uk/aerodynamics-explained https://www.kudauk.ltd.uk/aerodynamics-explained : Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab. I'm sure there's a lot more out there. The eventual switch to electric will probably come with another round of aerodynamic improvements to maximise range, as with cars.

trashb 9mo ago
> removing mirrors allows for much smoother cab airflow On brand new trucks (designed without mirrors) yes. However on older trucks the mirror design might be an essential part of the aerodynamic design and required for a low drag coefficient.
masklinn 9mo ago
> Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab. Cab-top deflectors are extremely common on every truck where the cab is not tall enough to cover a standard trailer (which is common, usually only the highest end sleepers are that tall e.g. Scania's highline cab on the R and S, Volvo's globetrotter xl and xxl, ...) For instance on this hero image from scania's site every truck but the very shortest and the very tallest have a deflector: https://www.scania.com//group/en/home/products-and-services/trucks/_jcr_content/root/responsivegrid/responsivegrid_copy/responsivegrid/heroimage.coreimg.85.1920.jpeg/1585221957546/18317-001.jpeg https://www.scania.com//group/en/home/products-and-services/... Obviously if you run higher than standard trailers, you need a custom deflector.

svilen_dobrev 9mo ago

also check Luigi Colani's quite bold designs: https://www.colani.org/luigi_colani_Product_design_museum/Trucks.html https://www.colani.org/luigi_colani_Product_design_museum/Tr...

netsharc 9mo ago
Meanwhile in Hollywood: https://www.fortressofsolitude.co.za/the-highwayman-reboot-the-worlds-coolest-truck-should-return/ https://www.fortressofsolitude.co.za/the-highwayman-reboot-t... In one episode the helicopter actually detached and flew!

jcgrillo 9mo ago

Another development in trucking efficiency that seems really interesting is the Achates opposed piston two stroke. If their materials are accurate, through fluid modeling they've achieved a massive efficiency boost and emissions exceeding regulatory targets without urea injection. In a piston ported two stroke. https://www.ccjdigital.com/regulations/article/15291029/achates-nearzero-diesel-fighting-for-production https://www.ccjdigital.com/regulations/article/15291029/acha... This is the most recent news I can find about them, though, so unclear if these engines will ever be produced for road vehicles: https://www.govconwire.com/articles/ga-asi-david-alexander-achates-power-opposed-piston-engine-tech https://www.govconwire.com/articles/ga-asi-david-alexander-a... See also: https://achatespower.com/resources/ https://achatespower.com/resources/ I was hoping we'd see these engines running generators in Edison trucks one day.

mikeayles 9mo ago

As someone who works in commercial fleet fuel economy (powertrain, not aero, but you keep an eye on the whole stack since technologies compound), it's worth noting how far the industry has moved since the 1970s NASA Dryden work. The sheer amount of "snake oil" bolt-on products sold to fleets in the 90s and 00s means the industry now demands rigorous third-party validation. The best open source testing I've seen comes from Mesilla Valley Transportation Services (https://www.m-v-t-s.com/certified-technologies/ https://www.m-v-t-s.com/certified-technologies/). They don't rely on ECM dashboard readouts or pump receipts. They run a control truck and test truck simultaneously on a track or controlled highway loop so weather, air density, and wind are identical. Anemometers on the trucks algorithmically factor out wind speed/direction, tyre temp, and weight. Tests are designed to answer the actual question rather than tick a standard's boxes. Their chief test engineer was ex NASCAR, IndyCar and F1. My team actually tested a dual-fuel system with MVTS. The engineering was sound, testing proved a slight thermal efficiency improvement, but cheap US diesel versus the cost of the alternative fuel meant the ROI was non-existent. The physics worked, the math killed the project. (The economics work in Europe, thankfully.) A lot of what's being discussed in this thread is already standard too. Mirrorless cabs are more the rule than the exception now (as pjc50 linked above), close-coupled trailers with gap fairings, wheel covers, under-trailer aero, all commonplace. A couple of current ones worth knowing about: the Scanias with the "Super" powertrain run a really aggressive overdrive at around 900rpm at the 90km/h (56mph)EU limit, where a conventional truck sits around 1200rpm. Requires huge low-end torque but claims 5-8%. The Mercedes Actros L claims 3% from its slippery front end alone. It is absolutely hideous though, so make of that trade-off what you will. The biggest factor though is driver variability. All the aero and powertrain hardware in the world doesn't matter if the driver thinks they are the stig. The biggest shift in the last decade has been removing human inconsistency from fuel economy entirely. Automated Manual Transmissions are now completely dominant in modern fleets. They shift perfectly for fuel efficiency every single time, totally capping the penalty of a bad driver. Layer on top of that Predictive Cruise Control. Modern trucks use GPS and 3D topographical maps to "see" miles ahead. The truck's computer knows exactly when to back off the throttle before cresting a hill to coast over the top, and exactly how much momentum to carry into the next dip. A human driver relying on their eyes simply cannot compete with a powertrain that knows the exact gradient of the road three miles ahead.

trashb 9mo ago

I don't know too much about the USA side of trucking but in the EU the cab over trucks have been able to steadily improve their aerodynamics, and there has been a lot of effort into improving this. Obviously there is more frontal area compared to a passenger car but comparatively modern EU trucks are quite aerodynamic. (even though they may not look it) There are other things to consider as well when building a truck, as mentioned the maximum length limits, comfort, power price and more.

cestith 9mo ago

One of the comments on the original article plays aerodynamics off as unimportant, saying only up to 0.4 miles per gallon difference. Even if that number was true, this is an industry that gives drivers patches on their shirt or hat for averaging above 7 miles per gallon of fuel for the year. An extra 0.4 miles out of every gallon is insignificant at all.