9/15/08 - Do Cars Really Need to Look Like UFOs to Save Gas? - gas2.org

[n_dawg]

Original article with hyperlinks to more information: link (http://gas2.org/2008/09/15/do-cars-really-need-to-look-like-ufos-to-save-gas/)

http://gas2.org/files/2008/09/aptera_prius_insight_mashup.jpg

Do Cars Really Need to Look Like UFOs to Save Gas?

Written by Nick Chambers

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?

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 drivingAn 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?

[c0mp13x]

Nice article n_dawg... thanks.

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
Wait a second Dr. Dre(la)... you haven't done all your MIT research on what the Aptera is. It is both a extremely light plug-in electric car and a low drag highway car. Right?!

:happy0017:

[n_dawg]

Yeah, pretty much. See my comment on their site.

It seems like it would be far easier to persuade people to change their aesthetic judgements of technically superior vehicles like the Aptera than to make everyone buy two cars. After all, advertisements convinced us to buy the Hummer. Get the hunk/babe du jour to love it, drive it, be photographed in it, etc. It's sleek, it's curvaceous, it's got room for two. Technical merits aside, any ad agency that can't sell this thing isn't worth its weight in molybdenum.

Thanks for cleaning up the quote – I'm way too lazy to have done it myself.

[qpham63]

There is no need to try to convince people of anything. If demand continues to outstrip supply, fuel cost will continue to rise.

As the Aptera log on actual miles in the real world and continue to drive by gas station without stopping for fuel it will sell itself to the cost conscious consumers.

I am not wising for this but the construction of the Aptera with its integrated sandwich structures and use of foam and one piece body construction would do quite well in real world accidents and as people fare well through these events, its safety will appeal to the safety conscious crowd.

Eventually, it will gain acceptance as the smaller compact cars has been accepted and was first laughed at when they were introduced in the mid 70s while gas prices was $.69/gal. I see that the general public will be skeptical of the Aptera for a decade or so or $10/gal gas...but that is just my guess.

[KarenRei]

Hey, qpham -- long time no see :) I agree completely that style preferences will change. They always have. Back in the era when this car was the latest thing:

http://imagecache2.allposters.com/images/pic/PTGPOD/253831~1934-Ford-Deluxe-Four-Door-Sedan-Posters.jpg
(1934 Ford Deluxe)

The streamlining on this car was considered way too radical:
http://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/1934ChryslerAirflow.jpg/200px-1934ChryslerAirflow.jpg
http://www.9sn.net/resim/1934-Chrysler-Airflow.jpg
(1934 Chrysler Airflow)

It looks so tame to us now, but this was the Aptera of its day (it and its sister car, the DeSoto Airflow). And in so many ways, it was technologically superior to its competitors. It used a full steel body instead of steel and wood. It had a better power to weight ratio than most cars on the road. It got better mileage. It had more passenger room. It was one of the first unibody-cars, and was a lot safer because of it. It had a far better weight balance (back when most cars were FWD with 65%-75% of their weight in the rear), and thus better handling.

And it tanked in the marketplace.

[curbowman]

I do agree with the article contents. For me, the perfect urban or commuter car is the Tango. All electric, good range, and slim enough to filter between other cars as motorcyclists do:

http://www.instablogsgallery.com/gallery/2007/12/17/tango-4_179.jpg

of course, it is WAY overpriced because they build it with carbon fibers and to be able to run very fast 0-60 mph times, but for city driving a fiberglass body and more modest acceleration would be just fine.

[wpatters]

We all need to remember that Dr. Drela was responsible for the MIT Deadalus (sp) human powered flight from Crete to Santorini. As a human powered nut my self (www.calpoly.edu/~wpatters/) I do respect his ideas.

Another way to go would be the all electric car for the city. Then we would have an aerodynamic trailer in the garage that has a engine/generator/gas tank. The generator in the trailer would keep the batteries charged without using an extension cord. We hook up the trailer for long distance travel and we don't need to own 2 autos.

Bill Patterson

[n_dawg]

And it tanked in the marketplace.

My point exactly. Thanks for bringing up the Airflow – it's exactly what I don't want to happen to Aptera. I don't want this to remain a niche car forever, and for that to happen in years, not decades, will take some marketing.

The tanking was also related to the fact that the manufacturing of unibodies wasn't well developed yet, so they had a habit of having their engines break away from the mounting. Let's hope nothing like that happens to the Aptera.

[KarenRei]

I brought it up just to illustrate that a level of streamlining that looks rather tame these days used to be such a radical concept that it scared people off ;) But yes, I sincerely hope that Aptera doesn't suffer the same fate. Thankfully, I see a lot of modern factors pushing toward a confluence in favor of vehicles like the Aptera (high gas prices, global warming, urban pollution, "green" becoming trendy, etc), and a market that's surprisingly accepting of its style (at least half the people I've seen comment on it love it... that's a pretty good ratio for such a radical design in my book! I doubt you'll get those kind of percentages on, say, the nmg)

[speculawyer]

Do Cars Really Need to Look Like UFOs to Save Gas?

In one word . . . Yes.

In longer form:

If you want to have a car that can drive fast then, yes, it needs to designed aerodynamically to save gas. If you are willing to drive very slow . . . less than 25mph or so, then you can shape your car however you'd like. But when you are driving at freeway speeds then, yes, it is absolutely essential to shape the car aerodynamically to save gas.

[speculawyer]

Another way to go would be the all electric car for the city. Then we would have an aerodynamic trailer in the garage that has a engine/generator/gas tank. The generator in the trailer would keep the batteries charged without using an extension cord. We hook up the trailer for long distance travel and we don't need to own 2 autos.

Yeah, I would really like to see someone commercialize this idea. I suspect someone will within a few years after a ton of Chevy Volt owners realize that they can go weeks or months without ever using the gas engine.

This would allow for various business models. The car and trailer could be sold seperately to reduce the initial price of the car. It would be nice if a Chevy Volt option were to give it a bigger battery and put the engine on a trailer this way. The trailers could be made available for rental by people who can use electric-only most of the time but do occasionally want to go on weekend trips or long family car trips.

Here is the famous AC Propulsion Tzero that was an inspiration for the Tesla with such a generator trailer. (I think that is Alan Cicconi (sp?) himself filling it up.
http://upload.wikimedia.org/wikipedia/commons/9/9d/Acp_tzero_DSC00467.jpg

[qpham63]

To a smaller extent even at 25MPH you are still doing a lot of work in punching a hole through the air to move through it. You feel it most when you are on a power limitted situation like a bicycle.

Get on your bicycle (well tuned and tires inflated to highest recommended pressure), ride on flat ground (less than 2% grade) and at zero wind (less than 2-4 MPH) at 20MPH or 25MPH, it is very difficult even without wind and notice that if you are just keeping the constant speed all that you are putting on the pedal is going to nothing but overcoming wind resistent with very small amount of energy towards overcoming rolling resistance of the drive train and the wheels.

In cruising, aerodynamic rules. In stop/go traffic of high density cities, light weight rules but that is not to say that weight is a non issue at higher speed or aerodynamic does not play a role at lower speed.

This is why the Aptera vehicle is such a great approach. It is a nice slippery package that is very aerodynamic, and it takes advantage of the high strength/stiffness to weight ration of comosite material and use it in a clever sandwich structure design with integrated foam core that further enhance the composite's ability to carry load and the fact that variation in thickness can be buit in to the structure to use the material efficiently.

The result is a vehicle that is slippery at high speed (low speed as well) but still light weight so that in stop and go traffic, it take less energy to slow down the car and also less to accelerate it.

The foam, a key component in the structure acts as lost tooling in some cases, shear carrying component in a sandwich structure in others but overall it will attenuate sound, something that even the most expensive luxury care only add in the form of expanding foam, carpet padding and insulated door panel to manage noise as added weight.

The stamped steel or aluminum approach of the current car makers can not achieve these compound curvatures well without being made from many pieces that increases cost and weight. Shapes like the Aptera lends itself to the flexibility of the composite material as the reinforcement components is simple flexible cloth.

I envision that there will be modifications in the future for the Aptera and like vehicles like the Tango, tandem seating would reduce the frontal area a big component of the drag equation.

I have envisioned a 3 seater that has staggered seating so that the vehicle is narrower than side by side but longer to accomodate 3 (3 in our family this is why I am on the list for two Apteras), the driver dead center, the two passenger in staggered formation behind the driver so that they are closer side by side but one of the seat is ... 12-18 inches behind the other.

Ah...I went off on a tangent and started to ramble...Sorry.

Well, low drag and light weight, the aptera has it all. The Tango is a nice design as well but counts on lots of weight from batteries to keep its CG low to keep from flipping over. What I have read on it indicates pavement scorching performance...nice but I like the Aptera better although the tandem seating packages well but perhaps not the most aerodynamic but with power out put like the Tango, aerodynamic is not a big problem for them...just draw more amperage and have more batteries available.

[NeilBlanchard]

Hello,

Have you ever tried to drive a small, light car with a (relatively) heavy trailer?

Years ago, I saw a storage "papoose" that locked onto the car at two points (it only pivoted vertically) that had one "caster" wheel to support it's weight. It stays aligned with the car at all times, so you can back up without much effort.

I think that the Typ-1h (or whatever it is now called) shows that this kind of power-supplying trailer is not really needed: the battery is 2/3 the size of the all electric version, and yet it can power itself for 600-1,000 miles! Sounds pretty awesome to me.

The inconvenience of having to add the trailer (and store the trailer) seems to be onerous. What if you have to change your plans while you are away from home? I think that if the trailing papoose was used for additional storage, would be a better idea.

[Edit: I did a Google image search for "one wheeled trailer" and this is as close as I came up with: http://www.aircooledtech.com/single_wheel_trailer/1950swt-12-30-2.jpg

http://www.singlewheel.com/Auto/Coffman/Brian/58&trailer.jpg
If this was shaped to fit the form of the back of a hatchback car -- it could even form a boattail and improve the aerodynamics of the car.]

[speculawyer]

Have you ever tried to drive a small, light car with a (relatively) heavy trailer?

Years ago, I saw a storage "papoose" that locked onto the car at two points (it only pivoted vertically) that had one "caster" wheel to support it's weight. It stays aligned with the car at all times, so you can back up without much effort.

The AC propulsion folks dealt with this in their 'backtracking' feature. Basically, they made the wheel of the trailer steerable.

AC Propulsion also produced a portable internal combustion powered generator mounted on a trailer known as the Long Ranger that could be towed behind the car and feed power to the batteries during travel. The trailer used a 500 cc Kawasaki engine with a 9.5 U.S. gallon (40 liter) fuel tank and achieved 30 to 35 mpg over at least 20,000 highway miles. It is rated at 20 kW DC output and can maintain 60 to 80 mph. Video footage of the backtracking feature, which allows drivers to easily back a trailer through a set of slalom cones, can be seen here.
Link to the movie:
http://www.acpropulsion.com/videos/backtracker.mov

I think that the Typ-1h (or whatever it is now called) shows that this kind of power-supplying trailer is not really needed: the battery is 2/3 the size of the all electric version, and yet it can power itself for 600-1,000 miles! Sounds pretty awesome to me.

The inconvenience of having to add the trailer (and store the trailer) seems to be onerous. What if you have to change your plans while you are away from home? I think that if the trailing papoose was used for additional storage, would be a better idea.
An electric-only with trailer option is certainly not a solution for everyone, but it seems like it would be a nice option. Make both and let consumers pick what is best for them. There have already been threads here talking about a trailer for the Atera with a charger or an add-on at the back of the Typ-1e.

[KarenRei]

2/3rd the size? The official range of the Typ-1h is "40-60 miles", versus 120 for the Typ-1e. If it's 2/3rds the size, most is either not in use or kept in reserve.

[NeilBlanchard]

Hi Karen,

2/3rd the size? The official range of the Typ-1h is "40-60 miles", versus 120 for the Typ-1e. If it's 2/3rds the size, most is either not in use or kept in reserve.

I read that the Typ-1h would have ~80miles all-electric range; but I guess this has changed?

[KarenRei]

http://www.aptera.com/details.php

With the Plug-in Electric Hybrid version of the Aptera(typ-1h) the mileage of the vehicle is difficult to describe with one number. For example, the Typ-1h can drive 40 to 60 miles on electric power alone. Perhaps for such a trip, the engine may only be duty-cycled for a few seconds or minutes. This would produce a fantastic number, an incredible number that, though factually true, would have no useful context, i.e. it's just a point on a graph.

[gg222]

Hi Karen,

I read that the Typ-1h would have ~80miles all-electric range; but I guess this has changed?
Neil,
Maybe you heard it from here http://en.wikipedia.org/wiki/Aptera_hybrid_car
As with any series hybrid, fuel economy of the Aptera Everywhere depends on trip length and battery charge. For trips of less than about 50 miles (80 km) after a full charge the engine may not turn on at all, resulting in ‘infinite’ fuel economy.
km and not miles. It would be nice though. :)