New Ocean
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- Nov 19, 2009
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Composites are absolutely better than steel, both in terms of heat resistance and strength to weight ratio. Of course, that's assuming you can get your hands on the correct composites. Sadly, I can't get my hands on any truly high-temperature composites (much as I would like a rocket made of RCC, it isn't going to happen for obvious reasons), so I'm using a combination of very high Tg epoxies and ceramic coatings to hopefully get a similar effect. Interestingly though, with high Tg epoxy, you can get composites that retain strength up to around 500F, which is pretty much as good as aluminum in terms of heat resistance.
I hate to dwell on this but I see tradeoffs in any composite materials. You already mentioned one, the cost of RCC makes it basically impossible to use on our projects. CF is lighter but certainly not as heat resistant as steel in almost any conceivable layup that we can do, including your high temp layup. CF may conduct heat away from exposed surfaces faster, however.
CF is really crippled by the resins available, and I am unaware of any conditions where it can beat steel thermo-mechanically in high speed rockets. Correct me if wrong but I have not seen it.
The survivability, cost, strength to weight of steel, and other factors combined make steel the best possible choice for high performance rockets.
Also consider the fact that if a rocket project fails once and then works on the second try, it is twice as expensive. If a more expensive metal rocket works the first time, that may actually save money in the long run.