Slashdot Mirror

I want SkyTran: http://www.skytran.us/

Why doesn't Google skip the obsolete car and support skyTran?

http://www.skytran.us/intro/

Self driving cars are pointless. They do NOT solve the traffic problem. They do NOT solve the crappy road problem. Hauling a ton of steel & plastic along with a few hundred pounds of flesh from point A to point B is NOT very efficient.

Now, imagine if Google helped build a skyTran network in any major city. A new fiber/power/gas/wifi network could be easily added to the build-out to break the last mile strangle hold.

I RTFA and the company, SkyTran, is based in California, USA. In fact, the CEO is a former Navy Seal (he also has a lot of international experience, but none previously involving Israel, from what is listed).

They do have an attorney in Israel.

http://skytran.us/skytran-team...

This doesn't explain why Tel Aviv was chosen as the first build out.

I'm not talking about a long hood so much as a tall hood relative to the rest of the vehicle - the car starts, then suddenly it's nearly as tall as the roof. Example: here's the concept mode for the Chevy Volt. I took one look at it and smacked my head, anyone who knows aerodynamics can see that that thing is going to have the aerodynamics of a rolling brick (spoiler: that's a whopping 0,43 drag coefficient on a supposedly "efficient" car!). Nobody should have been the least bit surprised when it changed dramatically going from concept to production. Yet that concept look is supposed to mimic the look of a "chopped" car (despite not reducing the frontal profile) and thus be "sexy", "muscular-looking" and desireable. It just ruins it for me. I know that I'm weird in being turned off from a car by seeing its awful aerodynamics.

Basically, there's no reason that your "long hood" has to quickly flare to full width/height in the front, then remain relatively constant height up to the windshield. That's highly suboptimal for aerodynamics and achieves nothing in terms of giving you a long distance to decelerate in. The optimal aerodynamic front end is roughly elongated-egg shaped.

Beyond that, you don't need a long hood at all, either, for crash protection, just a long deceleration distance. Hood length and deceleration distance, though related, are not equivalent. One factor, for example, is where the driver / passenger are located inside the vehicle. If you have a highly raked windshield (optimal aerodynamics) then the driver and passenger have to be located a bit further back from the front of the car for headroom reasons, so there's still plenty of room ahead of them to the foremost point on the vehicle. Also at play is how the vehicle deflects force in an accident - whether it crumples straight back or whether the nose rides up during a collision (the latter gives extra deceleration distance). A greater rake on the windshield also decreases the chance of windshield penetration.

It should also be pointed out that such a design also enhances pedestrian safety in a number of respects. The lack of an abrupt flare means a pedestrian is more likely to be hit at an angle and accelerated over a greater length of time (reduced G-forces). The matching rake between the hood and windshield additionally means they're not going to suddenly decelerate at the windshield. To be fair, of course, some pedestrial-safety features, such as low bumpers, run counter to aerodynamics.

As for that SkyTran PRT: Judging from the image on the cover, it looks like a reasonably good shape up front, but the rear end sucks. Contrary to popular misconception, it is *not* good to have a rounded rear end. Once your angle gets too steep, the flow will detach from your vehicle, leaving a low pressure wake. You want to not exceed the critical angle (aka, use a roughly constant taper angle) and prolong the detachment as long as you can (aka, as gentle of a taper as your design parameters allow), and when you can't delay the detachment any more, you want a relatively abrupt cutoff, potentially with a vortex generator to draw down the stream. The actual details vary depending on the situation, and one always needs to do CFD work, but that's a rough "in general" for aerodynamic optimization

Update: I searched more and found some rather different looking PRT images. These are of an excellent aerodynamic form, with an appropriate taper in back (though I personally prefer a vertical taper to a horizontal taper for cars... theirs makes sense for their particular application, however). I'd be willing to wager that their cover image was an early artistic concept, while the latter was something they actually did CFD work on.

I'm not talking about a long hood so much as a tall hood relative to the rest of the vehicle - the car starts, then suddenly it's nearly as tall as the roof. Example: here's the concept mode for the Chevy Volt. I took one look at it and smacked my head, anyone who knows aerodynamics can see that that thing is going to have the aerodynamics of a rolling brick (spoiler: that's a whopping 0,43 drag coefficient on a supposedly "efficient" car!). Nobody should have been the least bit surprised when it changed dramatically going from concept to production. Yet that concept look is supposed to mimic the look of a "chopped" car (despite not reducing the frontal profile) and thus be "sexy", "muscular-looking" and desireable. It just ruins it for me. I know that I'm weird in being turned off from a car by seeing its awful aerodynamics.

Basically, there's no reason that your "long hood" has to quickly flare to full width/height in the front, then remain relatively constant height up to the windshield. That's highly suboptimal for aerodynamics and achieves nothing in terms of giving you a long distance to decelerate in. The optimal aerodynamic front end is roughly elongated-egg shaped.

Beyond that, you don't need a long hood at all, either, for crash protection, just a long deceleration distance. Hood length and deceleration distance, though related, are not equivalent. One factor, for example, is where the driver / passenger are located inside the vehicle. If you have a highly raked windshield (optimal aerodynamics) then the driver and passenger have to be located a bit further back from the front of the car for headroom reasons, so there's still plenty of room ahead of them to the foremost point on the vehicle. Also at play is how the vehicle deflects force in an accident - whether it crumples straight back or whether the nose rides up during a collision (the latter gives extra deceleration distance). A greater rake on the windshield also decreases the chance of windshield penetration.

It should also be pointed out that such a design also enhances pedestrian safety in a number of respects. The lack of an abrupt flare means a pedestrian is more likely to be hit at an angle and accelerated over a greater length of time (reduced G-forces). The matching rake between the hood and windshield additionally means they're not going to suddenly decelerate at the windshield. To be fair, of course, some pedestrial-safety features, such as low bumpers, run counter to aerodynamics.

As for that SkyTran PRT: Judging from the image on the cover, it looks like a reasonably good shape up front, but the rear end sucks. Contrary to popular misconception, it is *not* good to have a rounded rear end. Once your angle gets too steep, the flow will detach from your vehicle, leaving a low pressure wake. You want to not exceed the critical angle (aka, use a roughly constant taper angle) and prolong the detachment as long as you can (aka, as gentle of a taper as your design parameters allow), and when you can't delay the detachment any more, you want a relatively abrupt cutoff, potentially with a vortex generator to draw down the stream. The actual details vary depending on the situation, and one always needs to do CFD work, but that's a rough "in general" for aerodynamic optimization

Update: I searched more and found some rather different looking PRT images. These are of an excellent aerodynamic form, with an appropriate taper in back (though I personally prefer a vertical taper to a horizontal taper for cars... theirs makes sense for their particular application, however). I'd be willing to wager that their cover image was an early artistic concept, while the latter was something they actually did CFD work on.

Honestly, I'll be happy if we can just get people's style preferences to shift away from naturally high-drag forms like those ridiculous oversized front-end things where you can barely see over the hood.

Part of the reason cars still look like this is for crash protection. Even mid-engine cars like Ferraris, as well as Teslas which have the motor in the back and batteries on the bottom, have long hoods, for crash protection. If you stick the passengers at the front of the car, you'll have no crumple zone and therefore no survivability in the event of a frontal crash.

If you want to see a vehicle with REAL aerodynamics, check out SkyTran PRT. Since these vehicles are designed for maximal efficiency, and don't have to worry much about crashes since they're on rails, the people pods are designed for optimal aerodynamics.

I'm sorry, I don't consider driving 2-ton vehicles around in traffic with incompetent drivers and living in subdivisions to be a "high quality of life". Better than Mexico perhaps, but not the ideal. You're making the mistake of equating the amount of resources consumed to be directly proportional to "quality of life", and that's crap. So if someone trades in their gas-guzzling 1970s jalopy for a new Nissan Leaf (or a used Honda Insight), and then quit their job that's 60 minutes away for a new one that's 5 minutes away, suddenly their quality of life has fallen because they're not consuming so much energy any more? People could live far more efficiently, and far better, than they do today with better technology (like Personal Rapid Transit) and habitats), but it would take investment, discipline, and a change in society and values to get there.