SkyTran : A good idea or pie in the sky?

When I first joined this forum, I posted a thread on the Hyperloop, a proposed rapid transportation system that would allow for rapid and energy efficient transit between cities. It sounded great in the press copy, and I wanted to know engineering reasons why it wouldn’t work.

A lot of posters came on with useful criticism : notably, Sam Stone spotted a serious flaw that would raise the cost and difficult of constructing the system considerably.

The real problem with the hyperloop is that it does not solve the actual problem. Wide body airliners work just fine for rapid transit between cities. You do have to waste a lot of time at the transit station (airport), but you would have to waste about the same amount of time at a hyperloop station. Airliners do have the significant drawback that they consume large quantities of expensive fuel that theoretically is of finite supply, but this is not going to be a problem for a while yet.

The actual problem with transportation is 2-fold :

  1. Human drivers on the streets cause traffic waves and all sorts of other slowdowns as a result of the vehicles being driven by humans. As a society, all this time people lose driving their cars is irreplaceable productive hours that could be spent on useful tasks.
  2. Cars powered by internal combustion engines create significant localized air pollution and burn a very expensive fuel. Also, accidents cause them to be very expensive for a society (due to medical expenses/lost productivity).

Mass transit solves #2 (trains/buses use a lot less fuel per mile and can be electric) but does not solve #1. While trains and buses in dedicated lanes don’t have to deal with traffic, you have to wait for them to stop at places that are not your destination. In practice, they are often slower than driving a car and waiting in traffic.

So, an idea system would be extremely energy efficient (ideally running on electricity), automated, and would take riders directly to their destination with no stops in between.

Well, here it is :

There’s a tremendous elegance to this design. You don’t have any mechanical friction because the car is not touching the track. (although you do have electrical resistance through the coils in the track but it is a smaller energy loss than rubber on concrete)

Aerodynamic friction is also minimized by the streamlining, which can be ideal since the pod does not need wheels, mirrors, a windshield, or the ability to survive high speed impacts with other pods. (you’d rely on redundant control systems to prevent collisions instead)

The pods are extremely light weight, a few hundred pounds at most. The lower weight also reduces the strength of the magnets needed, which in turn means less losses to electrical resistance in the track coils

This in turn means that the track to support them doesn’t need heavy supports - you could probably just anchor it to the frame of nearby buildings or use lightweight support poles. It certainly looks like a factory could construct a field deployable “kit” that could be trucked in, containing all the pieces of the system ready to assemble on the bed of a semi.

Riders will reserve a slot via cell phone app that will tell them when the next pod available to take them to their destination will be at the station. This means no waiting at the station for an undetermined amount of time. Riders aren’t trapped with people they don’t want to ride with, the pods are 2 person at most. Presumably, the pods will all have wifi and charging plugs.

As an engineer, this system feels like an optimal solution. Why hasn’t anyone built one in 25 years? Except for this prototype.

It would cost a bonkers amount of money to install the rails and power them. Far, far more than existing mass transit.

Did you bother to read any of the links, at all? There’s no reason to come to that conclusion.

You’ll forgive me it I’m a bit jaded. Personal monorail projects have been proposed left and right for decades. This one has a nice Web site, perhaps with a bit too much marketingspeak.

It all seems technically feasible (to my untrained eye), although the cost projections seem optimistic. It’s probably still cheaper to build than a subway, at least in warm climates.

It’s unclear if people would give up their cars for it. Probably not in North America, but I don’t know enough about Israel.

I did read them. The projections are the promoter making ridiculous claims to try and get people to buy into his idea. Realistically the costs will be far higher than advertised.

Where are these things supposed to be installed? In my low-density residential, suburban neighborhood? In high-density central cities where every available inch of space is being used?

How do you resolve the capacity problem of people all wanting to ride during morning and evening rush hours? If the waiting time for a pod is too long, people will go back to their own cars. If you design for peak demand, you have a tremendous amount of rolling stock idle most of the time.

And, just like light rail, you’re talking about a route that operates on a set course. What happens when a major employer moves from its spot to another location that’s not on the grid? Those kinds of changes doomed the streetcar lines. Buses allow for more flexible scheduling.

Ok, then point out a flaw instead of declaring “bonkers amounts of money”.

There’s no information in that post. Given the cars are each far simpler than modern cars, and the track is much lighter (albeit higher tech) than existing roadways, it seems possible to me that, with mass production, this technology would be cheaper than what we currently use.

  1. Everywhere.

  2. Parallel stations and lots of pods. Yes, that does mean the rolling (well, hovering) stock will spend the majority of it’s time idle. However, this is not any different than current mass transit or our personal cars, which are idle in parking lots most of the time. The pods would need to be relatively cheap to manufacture.

  3. You install more pod tracks to cover this. Since you do not need to block lanes in the road, there’s no reason you can’t do this. Ideally, business could pay for a pod connection to their premises so that they would not have to wait for city funding to pass. (the pod station would be inside the building, ideally. Only riders on a preapproved list kept by the business would be permitted to go there)

It was consideredin Google View, er, Mountain View, Ca. Some real world/practical back and forth in the article.

Even at the advertised cost of US$10M per mile of track, it is as expensive or moreso than the construction of new roadways (per lane of road). The “greenness” of the system is only expressed qualitatively, but such a large, high powered grid is certainly likely to have high power distribution losses. The supposed “lightweight supports”, while perhaps lighter than bridge structures, are still going to have to be robust enough to withstand not only to mass of the pods themselves but also dynamic and wind loads, as well as carry the weight of permanent magnets and high power electrical lines on the rail; no one is going to be attaching these to unreinforced building structure (and the legal and liability consequences of that notion are shudder-worthy).

With that being said, there is nothing technically infeasible about the system. I doubt it will cost anywhere near the advertised costs; based upon prior maglev systems, the real costs are probably 5-10 times what is estimated. Inserting it into existing dense urban infrastructures with sufficient throughput to reduce highway congestion without significant modifications seems unlikely at best; nor is it a workable replacement for automotive transportation for a suburban or distributed urban environment. The system would be most workable in a dense urban environment which is built (or rebuilt) around it as a core transportation infrastructure; say, a business campus, or central “pedestrian only” area of a major high density city such as New York, Boston, or San Francisco.