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Comment by amerine | Hacker News Reader

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amerine

Price.

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This doesn't seem right.

Carbon fibre is price competitive with aluminium.

I haven't really seen this to be the case personally.

For a 1/32 thickness 12" x 12" sheet of carbon fiber, it is 35 dollars. This is actually this company's cheapest carbon fiber sheet too at that size. I have seen other companies charge more iirc. https://dragonplate.com/EconomyPlate-Solid-Carbon-Fiber-Shee...

Same sheet size / thickness for aluminum is 16 dollars (although I saw a shadier website selling for 12 dollars). https://www.mcmaster.com/aluminum-sheets/aluminum/multipurpo...

Now for cubesat grade stuff you might want something better than what I linked, but still its a good illustration of the price difference. That is over half the price. I think the prices are maybe closer than in the past, but there is still a significant difference.

I should note though that due to the strength differences this analysis may not be complete. Technically carbon fiber is stronger so you can get away with a thinner sheet while having similar strength. Using a thinner sheet might save on carbon fiber costs. However, I still believe this analysis illustrates the significant cost difference.

Say it's maybe $200 for carbon fibre vs $50 for Al (the difference isn't that great but being generous).

Either way the raw material price is going to be dwarfed by the labour cost building the enclosure, which are also immaterial in your $50-100k budget.

carbon fiber doesn't come in big billet chunks that you can cnc machine into any shape you want. you either need to fabricate something from pieces of carbon fiber plate (which is available in up to 1cm thicknesses) held together with adhesives and fasteners, or custom-form a carbon fiber piece from your own custom mold, such as if making a carbon fiber road bicycle frame, which has huge upfront costs and is only economical if you intend to sell thousands of units.

Yeah that is true as well. I talked about this a bit in another comment I made about how much easier aluminum is to work with. The thing is even for the raw sheets it’s still very pricey compared to aluminum which is pretty good at illustrating the price difference. Once you look at molding them into the shape you want the price only goes up.

Maybe if you can get by with entirely COTS parts. Aluminum is much easier to cut, drill, tap and bend.

Aluminum is comparatively cheap..

Or so I thought, I just tried to Google the comparison per KG and it's completely spammed by alibaba and miscellaneous SEO.

Good luck, have fun with that. Would appreciate any industry in insider POV.

At what point are the weight savings not worth the extra delta-V offset?

When the launch costs get from $10k per kg currently get down to around $100-$500 per kg

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