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 :
- 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.
- 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.
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.