Friday, November 16, 2012

Grokking the Hyperloop

I've made no secret of my "man-crush" on Elon Musk. As a former mechanical engineer, I view his engineering track record as nothing short of astonishing. From developing the best car in world to the first entirely non-government space rockets, Elon has set the bar for aspiring engineers. His latest brainstorm is on a new mode of transportation, which he refers to as the "hyperloop". There has been a lot of speculation about what the idea is, but most have settled on some form of train in a tube. I have my own pet theory though that I just had to publish before Elon sets us straight.

My thinking is a fairly natural extension of the electric car. I've already been advocating that to solve transportation issues we need to seriously consider redesigning how highways operate. I've had significant doubts regarding the viability of public transportation in a country like the United States. Public transportation is certainly the best solution for dense urban environments, but it quickly falls down as density declines. With hundreds of billions on the line for high speed trains, I can't help wonder if there is a better, more technology advanced solution.

I've modeled traffic some in the past and can now clearly show how with a mixed global and local optimization solution we could eliminate traffic on highways, ensuring the maximum throughput safely at all times. Taking these ideas a little further we approach my thoughts on the hyperloop. One of the main issues with electric cars is highway driving. It's both the place of least efficient driving and longest duration. What if to address the range issue with electric cars we just brought power to highways? While we're at it, why don't we get rid of rolling friction and deliver that power through rails? Similar to how those trucks used to service railroads can drop down wheels for travel on rails, we could have cars that deploy wheels on these new powered highway tracks. You could still have all the braking and accelerating benefits of rubber tires since you can just drop down and use them anytime they are needed.

Taking this one step further for long direct routes, these rail highways could be enclosed in a tube where the air is forced along at the global travel speed. Now we've eliminated both air drag and the rolling friction. This would allow electric cars to travel at much higher speeds all the while maintaining the efficiency of mass transportation. Now slap solar panels on top of the hyperloop and you have a completely self sufficient, rapid mode of transportation. I do have concerns with getting to the speeds Elon is after (faster than a jet), but I do think the overall simplicity and convenience would be time savings enough. Below is a crude sketch of my concept idea. Now we'll just have to see what Elon comes up with.


Jonathan Lansey said...

"They’re going for records in all the wrong ways." lol,

Also pushing all the air at that speed would be crazy. The boundary layer air at the wall would be at a standstill so there would be a huge amount of friction. Anything Musk is proposing is going to happen inside a vacuum. Probably just a series of small electric trains running inside of evacuated tubes (with step up accelerator rings).

Jonathan Lansey said...

oops, just read that he said it doesn't need rails - I should have known it also has to be a maglev variant to go that fast. Like a particle accelerator for trains. Probably the key energy challenge will be keeping all the superconductors cool enough.

Bruce Skarin said...

Yeah I love that line. Elon is pretty stiff, but he does have a few good jests now and again.

He also tweeted at one point that it wasn't a vacuum tube. I can't see how he could keep it at $6 billion and energy neutral using superconductors. I hadn't seen the no rails part.

I wasn't expecting the boundary layer to be a significant issue. It's not a airfoil or building in the path of the wind. I think from a the right materials you could have pretty low friction. It's a closed loop so it is different from just blowing a stream of air.

It'd basically be like having the jet stream at ground level. The larger question I have on this version is is how you enter and exit the flow. Would going from a large diameter tunnel tapering to a smaller diameter work?

I'd love to build a model, and in fact have friends that might be able to help.

Brent Fournier said...

What if you stored the suns energy as a partial vacuum in the tube.. and allowed air into the car (from the top of the tube) and exhausted it behind..

The entire tube would store energy without batteries, and the vehicles would even be able to float on the exhausted air.

Reduced air pressure = lower drag (300 MPH would be easy)

Simple, Powerful, Elegant

Unknown said...

Bruce -- I think you're right...this is going to involve some sort of tube with moving air. Elon is probably using the term "hyper" for a reason, and a tube with moving air which removes the frictional limit on electric cars is analogous to hyperspace, where space is shortened relative to normal space which removes the light speed limit. That would appeal to the science fiction fan in him. :-)

Do you think he might incorporate some sort of passive solar element into the design? I live in San Francisco, and on a warm day in center of the California, the wind blows crazy fast here. Apparently that'd due to the temperature differential between the cold Pacific and the hot inland. What if you could harness that phenomenon and force it down a tube? It wouldn't be reliable but on many days it would supply more than enough motive force, and the extra energy could be sold off to the grid.

Maybe there's a reason he chose California for his test bed.