Autodesk’s Idea to Knit the Hyperloop Out of Carbon Fiber
November 3rd, 2013Via: Bloomberg:
The tube in Musk’s plan is made out of prefabricated steel sections that must be welded together. Critics have pointed out that could leave the Hyperloop prone to air leaks, which would undermine the internal low-pressure system it needs to run. Brandt, who studied building technology at Harvard University and holds the title of technology futurist at Autodesk, proposes making the tube out of one very long stretch of braided carbon fiber infused with an epoxy resin. The strong, lightweight material is used to make everything from jumbo jets to race cars.
There are machines that can churn out limited qualities of the braided carbon fiber. Brandt envisions building a supersize version and mounting it onto a rig loaded with reels of carbon fiber so it could roll along the Hyperloop’s route. Working at a rate of 1 meter per minute, this factory on wheels could weave a Hyperloop tube from Los Angeles to San Francisco in less than two years, and, says Brandt, require fewer support pylons. “Elon’s estimate calls for about $2.6 billion for concrete, but we’d get that down to more like $1.5 billion,” he says.
Having been a quality engineer on the carbon fiber Boeing 787, I can say that there are some technological issues with building an outdoor carbon fiber tube.
First is the stuff sags with heat, time and gravity. Without considerable strengthening with stringers and frames, or a cored dual layer, it will collapse.
Second, curing the resin typically involves an autoclave- a very large, expensive one, and vacuum bagging and a sizeable heat bill. I am sure other resins could be used, but doubt any could be mixed hot enough to produce anything but an inferno at a production rate of a meter per minute. Remember a form or mold and perhaps caul plates are needed as well until it cures.
Third, carbon fiber resins deteriorate when exposed to ultraviolet light. So the finished product has to be protective coated- it cannot be left “raw” for any length of time. And btw, this is a silly application of carbon fiber. Fiberglass will accomplish the same thing for far less money.
Fourth, while tape machines are common, the amount of tape to manufacture a tube of several hundred miles in length would be far more expensive than any profit margin will ever offset.
I love thinking big engineering projects, and it would be interesting, but not many people are going to be up for being inside of a black tunnel for more than a few minutes.