Do Cars Really Need to Look Like UFOs to Save Gas?
With the world focused on fuel economy, advanced car design seems to be converging around one point in space. And I do mean, literally, a point in space — a point sometimes seen flying over Roswell, or crashing in the Bermuda triangle.
Regardless of what you think about this type of design, it begs the question: do cars need to look like alien spacecraft to get decent fuel economy?
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Recently, when I posted about the newly announced Honda Insight’s uncanny resemblance to the Toyota Prius, I sparked a rather *spirited* debate with fellow blogger and former Gas 2.0 writer, Ben Jones (ecomodder) regarding aerodynamics and why all high mileage cars are starting to look the same.
His point was that if we want good fuel economy, we shouldn’t be upset when all cars start to take on the same shape. Basically, we shouldn’t whine about cars looking more and more like flying saucers if we want to save gas.
But I wasn’t convinced that in order to get good fuel economy all cars will have to look like the Prius. I remembered reading about a Mercedes concept car based on the shape of a Box Fish that looked nothing like the Prius and had an unexpectedly better aerodynamic profile. Also, the Aptera Typ-1, which looks more like a mutant sperm than the Prius, has much better aerodynamics too.
So, you’re probably saying, “Yes, both the Typ-1 and the Mercedes Box Fish Concept have better aerodynamics than the Prius, but they’re so strange looking that they’ll only appeal to a very small portion of the population.”
And you’d be right. Which brings us back to the question of the Prius shape, but now framed in a different manner. Perhaps the answer is that the Prius shape is the most aerodynamic design you can have and still appeal to a large enough market to make a profit (and an environmental difference).
But is the Prius design really a good compromise? Does it do itself justice by trying to accomplish so much in one vehicle?
To get to the root of this, I decided to seek out an expert opinion and contacted MIT professor, Mark Drela. Dr. Drela is a professor of fluid dynamics in MIT’s Department of Aeronautics and Astronautics and has been an adviser to MIT’s Vehicle Design Summit regarding vehicle aerodynamics. In a response via email, Dr. Drela had this to say:
“All common cars, including the Prius, are aerodynamic bricks. The lowest drag shape that you can wrap around a passenger cabin resembles the front half of a sailplane fuselage. The Aptera comes pretty close, assuming they designed it properly.”
What he’s saying is that the Aptera Typ-1 probably represents the ultimate achievable aerodynamic shape for an enclosed vehicle with tires. He goes on to say:
“We know how to make extremely low drag vehicles (e.g. the Aptera), but the main problem is making them acceptable to consumers and making them ’safe,’ however that is defined. I see it mainly as a marketing and lawyering problem, not an R&D problem.”
So there you go. The Prius is not the most aerodynamic shape, it’s the most aerodynamic shape that’s also visually acceptable and safe enough to meet standards. But does aerodynamics even matter that much? I mean, some cars today are getting excellent mileage and don’t look like the Prius or the Aptera.
The issue comes down to the fact that achieving good fuel economy on the highway is an entirely different beast than achieving it in the city. Trying to make one vehicle that excels at both creates a vehicle that doesn’t do well at either. As Dr. Drela says:
“At steady highway speeds, low air drag is most important. If you’re braking frequently, then low mass is most important. A hybrid squeezes the two very different missions into one vehicle, and you sort of get the worst of both worlds. It doesn’t do either mission as well as a targeted vehicle, and is more complex to boot.”
Instead Drela suggests that a better solution would be to have two targeted-mission cars:
- An extremely light plug-in electric car for city driving
- An extremely low drag internal combustion car for highway driving
He points out that, obviously, owning two cars is more expensive up front, but that the lifetime economics and energy use of this arrangement might prove that it is the best solution.
Purchasing two vehicles up front might be out of reach for most people, but, if Dr. Drela is right, perhaps we should be looking at ways to make this easier for everybody to do? Government incentives?
Certainly the car companies would be happy to sell you two cars at once — perhaps they could work up a discount on the second car purchased if purchased at the same time? Does this seem like a fantasy world that sounds great on paper but would never fly in reality? What do you think?
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Image Credits: Toyota, Honda, Aptera
We need to get away from car ownership and into easy short term rentals. Then, if you’re going on a long trip you can grab a minivan, but if you’re just going to the local grocery, an all electric works fine. This would work best if the cars could drive themselves to the location, and people would get a discount by allowing the cars to be stored in their driveways.
At a 55 mph speed limit, this aerodynamic styling is wasted - at least as far as fuel mileage is concerned. It’s for show, not function. An argument could be made that its good for noise abatement though. An aerodynamic car is probably quieter inside. Of course as soon as you crack a window, all that is lost.
Personally, I’m disgusted with current car design. Designers just worship at the altar of aerodynamics. Windshields are raked so far back they’re damn near horizontal. But any appeal to return to sensible styling gets trashed as being “retro”.
The Prius is butt-ugly. But then again, so is that stupid looking Aptera.
Modern cars are pretty far away from the original Model T Ford; heck, they look completely different from the 1970s, let alone the 1950s. The Aptera’s form is dictated by its function and design goals; the only reason to dislike its look is hidebound conservatism. (Although this isn’t surprising; car enthusiasts are some of the most conservative people on earth.)
>Larry said on September 16th, 2008 at 2:25 pm
>So tell me why a light weight car can’t have an aerodynamic
>shape? Seems aircraft designers have to deal with that
>problem every day.
Anytime you add non-structural requirements to something it will get heavier. Assuming the same materials, e.g. composites, a very minimal “shrinkwrap” body like on the tiny city cars can be made a lot lighter than the long tapering body, sloped windshield, and wheel fairings of the Aptera.
My thanks to Dr. Drela for providing input in the comments section! It’s a rare day when the person quoted in the article cares enough to chime in
the vast majority of consumers will buy based on price. All sorts of ugly cars are sold today. when total cost to own is low, they will sell like hotcakes.
Several points:
1) the Fiesta does in fact look remarkably like a Prius. Oh and its a diesel so you need to deduct 11% from the mileage for comparable energy efficiency, which is about 65/56 mpg on a comparable basis, still impressive. Also it is quite evidently a significantly smaller car than the Prius. Finally is the mileage determined on the same basis as US mileage ratings?
2) The notion that the Aptera is unacceptable to consumers because it looks weird is absurd. On that basis you would have predicted that the Toyota Camry would never sell had you made that prediction circa 1920. Tastes change. I would be very surprised if anyone will be selling a “brick” in 2028.
3) Dr. Drela should stick to aerodynamics and you would be well advised to source your articles from more than one expert.
4) An extremely light plug-in electric car sounds like an oxymoron to me. Batteries are very heavy. If your argument is that you only need short range and thus small batteries then why not a plugin hybrid? If you want an IC aerodynamic car for long distance then why not an Aptera plugin hybrid. In fact in what way is the typ-h Aptera not the ideal short and long distance solution for two passengers?
Scott,
1) The overarching point of my comparison is lost in your analysis of minutia. Yes, for the Fiesta article I posted a while back, they are US mileage ratings. 73 hwy, 63 city.
2) Future looking: yes people’s tastes may change, but unless you have a time machine, companies are selling things to people in 2008. If you don’t think the Aptera looks weird to 90% of today’s consumers, then (a) you likely are surrounded by, and interact with, people on a daily basis that don’t represent the majority and (b) I don’t think I can help you understand my point. Btw, personally I like the Aptera.
3) And you’re an expert in? I may only have quotes from one person, but that doesn’t mean my article wasn’t sourced from many points. The article is long enough as it is. Dr. Drela is a well-known MIT professor and has some valid food for thought. I’m not sure why you’re getting this dig in here, it kind of makes you look like a prick.
4) I think his point is that the more missions you try to include in one vehicle, the more complicated and expensive it gets. Having two targeted mission vehicles may be more efficient than having one complex multiple mission one — but he’d be the better one to answer that. Dr. Drela, do you have any thoughts on this last one?
The battery’s power handling capability is the limit on an ecar’s ability to scavenge momentum from regenerative braking. Given a sufficient capacity to take on a charge quickly without cycle limiting heating, the mass of a town car isn’t too important because the energy needed to accelerate is recaptured by the regenerative breaking. After coefficient of friction for highway driving, the battery’s energy density is the most compelling city driving enabling technology.
Nick,
Several of Dr. Drela’s comments touch on subjects that are far removed from aerodynamics specifically these two quotes: “…but the main problem is making them acceptable to consumers and making them ’safe,’ however that is defined.” and “…If you’re braking frequently, then low mass is most important. A hybrid squeezes the two very different missions into one vehicle, and you sort of get the worst of both worlds. It doesn’t do either mission as well as a targeted vehicle, and is more complex to boot.”
In neither case does a doctorate in aerodynamics suggest any special validity of his opinions. The later quote in particular is in direct conflict with my day-to-day experience as I explain below. But your right, Dr. Drela has every right to voice his opinion and your insinuation that his opinion may be more valid than mine, while a non sequitur, may well be right. My apologies to Dr. Drela. The fault is of course yours for quoting him as if he were expert in those two cases.
My own expertise lies merely in having owned a Prius for 6 years and having a engineering degree. That experience in particular should allow me take exception with the Doctor’s pronouncement that “It doesn’t do either mission as well as …”. As a matter of fact my Prius does do both tasks better than almost any other production automobile available over the time I have driven it. And when the Aptera becomes available it also will do both tasks better than any vehicle available or projected to be available, if the performance data offered to date can be believed.
In fairness to Dr. Drela, I think his point that a specially designed vehicle would be more efficient all other things being equal, is valid. However, in point of fact it is vastly impractical as evidenced by the fact that it has almost never been done in the history of the auto industry and in those cases where people have come out with such specialized vehicles they have proven to be unpopular niche vehicles. Furthermore, the notion that own two cars could be more efficient than owning one strikes me as very unlikely.
The fact is that except for very short runs presuming efficient regenerative breaking, all other things being equal, aerodynamics is the primary factor in determining a vehicle’s energy efficiency. Thus as economic and environmental forces drive us to vehicles with significantly higher energy efficiency aerodynamics will assert it self as a preeminent design criteria.
So in answer to your title question: Yes!