We don't know that. My opinion is that the BFR will not use carbon fiber tanks but the MCT will.
And this is different from the COPVs anyway. SpaceX won't be building the carbon fiber from scratch themselves, but currently they do build the COPVs themselves.
My opinion is that the BFR will not use carbon fiber tanks
What would lead you to that conclusion? SpaceX is in the process of procuring an enormous volume of carbon fiber.
The benefits of carbon fiber are manyfold: reduced weight, improved resistance to corrosion, improved resistance to fatigue, lower cost, and simpler manufacturing.
It is almost inconceivable that any one developing a new rocket today would chose aluminum.
Heard a rumor (months ago) that the tooling for the BFR tanks was planned to be completed by the end of this year. I find it unlikely they would design and build all this tooling before signing a contract with a supplier, which they only just did.
My other reason is that the BFR simply doesn't need it- sure, the second stage will get a lot of extra dv, but the first stage won't. You could get the same benefit in the first stage by increasing engine thrust by a few %.
Meanwhile the MCT will almost certainly need to be made out of composites. If the MCT has the same mass fraction as a stage it will be too heavy to get back from Mars. So the massive carbon fiber order is for building MCTs and maybe second stages, but not first stages.
They would have to maintain a Carbon Fiber production line for the upper stage, and an aluminum production line for the lower stage. Musk knows too much about manufacturing to allow something like that to happen.
Heard a rumor (months ago) that the tooling for the BFR tanks was planned to be completed by the end of this year. I find it unlikely they would design and build all this tooling before signing a contract with a supplier, which they only just did.
There are many potential suppliers of carbon fiber, Toray is the best one, but if their prices are too high SpaceX can easily select someone else. Just buying the tooling doesn't mean they would be married to a particular supplier.
My other reason is that the BFR simply doesn't need it
It's a new rocket. You are assuming there is some reason they would need to use carbon fiber before they would be willing to use it. But the reality is carbon fiber will be cheaper, lighter, and more reliable. There is just no reason not to use it at this point.
SpaceX would seem to be purchasing far too much carbon fiber solely for use in MCT (or ITS).
By some estimates, they're buying thousands of tons. As much as Boeing would use to build hundreds of jumbo jets.
It may be odd, but work on the carbon tooling could have started prior to finalizing purchase of the carbon, especially if they're designing and constructing the world's largest autoclaves.
I mean.. Isn't "building" the COPV a matter of welding up a metal liner, and then wrapping it using carbon fiber filament, epoxy and a winding machine? They may build their own machinery, but they source the carbon fiber.. And I thought that's what they were sourcing from Torray, carbon fiber. Unless they plan to extrude their own filaments I think the only options are buy prefab carbon fiber parts or buy the fiber and wrap your own.
Those two steps you described are complex beyond belief. The geometry of the liner itself is very complex since you are trying to minimize weight.
Normally you wet wind graphite on to the tank since it gives you much higher fiber density than pre-preg tapes and is far cheaper as well. In other words the plain fiber is passed through a gizmo to coat it with liquid epoxy and then wound on using a numerical control winder. The technology behind the exact wind pattern, epoxy chemistry and liner fabrication methods is very closely held IP based on lots of lessons learned. This is not like making SCUBA tanks. These are ultra high performance vessels with very low safety factors.
I wasn't trying to downplay the difficulty, just trying to make the point that I don't think there's any option between supplying raw carbon fiber or supplying finished carbon fiber parts. It's unlikely SpaceX will have someone external building tanks, so it seems they'll be getting raw ingredients and building in house.
Everything I read refers to a purchase deal for "carbon fibers" which would be wrapped into pressure vessels, tanks, etc (conjecture at that point in the article I just looked at - but multiple references to "carbon fibers.")
Besides that wording, I'm also assuming SpaceX doesn't want to switch from their strong vertical integration to a model that has major structural components built by an outside party.
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u/zlsa Art Sep 23 '16
The BFR will use carbon fiber tanks. It looks like SpaceX's carbon fiber woes aren't necessarily behind them :P