4 ms·
It's like the open source software of materials, not only is it cheap but it's fast because all the info you need is out there in industry. Steel is just so mu
by dsfyu404ed 7y ago
It's like the open source software of materials, not only is it cheap but it's fast because all the info you need is out there in industry.
Steel is just so much more workable every step of the way. You can order your special steel from close to anywhere, your fancy epoxy might have two sources. Any engineer can design for steel and be really good at it (they probably even took classes on it in college) so you can have more cheaper engineers working parallel. Your engineers that know their way around CF are gonna be much more rare and expensive. The tool and die side of things is well known. The little tricks that are tribal knowledge for CF have long been compiled and published into textbooks for steel. If you fat finger a relief radius the die maker is gonna ask you to clarify whereas with some modern material that doesn't have that body of documentation yet they'll just assume you know what you're doing. The material handling side of things is well known, you'll never have to trash a part of delay a deadline because someone somewhere didn't store one of your constituent products in the right environment. When you've finally built your rocket anyone can test it. The techniques for inspecting steel are well known and widely practiced. For exotic materials you either have to track down experts or build that tribal knowledge internally (expensive and slow).
These little conveniences compound throughout your entire "technology stack" so to speak and a rocket company has a really tall stack.
It's hard to overstate just how much easier and faster you can work in a known-known like steel vs something that's new, hot and sexy that everyone wants to treat like a trade secret (as is the case with CF).
Source: Former defense sector employee, granted on the software side but you still learn a lot of things through proximity.
- dnautics 7y agolove the description. not an expert, but I heard that spacex's steel alloy composition is a trade secret.
- airstrike 7y agoMy understanding is lots of steel grades are trade secrets. Though how to actually make it isn't necessarily a secret, others might not know which alloy is specifically employed for a particular purpose https://en.wikipedia.org/wiki/SAE_steel_grades https://en.wikipedia.org/wiki/SAE_steel_grades Same is true for aluminum https://en.wikipedia.org/wiki/Aluminium_alloy#Alloy_designations https://en.wikipedia.org/wiki/Aluminium_alloy#Alloy_designat...
- dsfyu404ed 7y agoIt's a trade secret in the way that a pizza franchise's sauce is a trade secret. The specific combination of component parts and why that specific combination was chosen is a secret but what the components do and how they interact and affect the final product is well known.
- skdjsjkhfkdsjh 6y agoI'm not sure why this is down-voted. Do people not believe that people with expertise in food can tell you what the amount of salt or sugar does to a sauce or that people in the steel industry knows what the amount of chrome does to a steel?
- lmilcin 7y agoDisclaimer: no real experience. I would also say that I suspect it is much easier to ensure and test quality of steel. Ensuring every square inch of compound material like carbon fiber meets all requirements is much more difficult. Steel can be made pretty uniform in large quantities, shapes and sizes. On the other hand carbon fiber can easily have local faults ingredient imbalances, etc. that will be difficult to detect but might significantly affect strength of the material. In case of a huge rocket it does not matter how small part of it fails, even a single substandard square inch of it might cause entire rocket to fail catastrophically. I also understand that steel fails in relatively predictable ways compared to compound material. Carbon fiber has different properties in different directions which depend on how it was layered and that is probably going to cause any calculations to have potentially very large margin of error. As building the rocket is very much about calculating how much can be shaved off, unpredictability in material performance might be a huge issue.
- nickff 7y agoThere are a variety of non-destructive test methods for carbon fiber. CF is definitely prone to defects, but it is now common enough, and sufficiently well-understood to be quite reliable.
- NikolaeVarius 7y agoOutside of Re-entry concerns, a large reason for the move away from CF was that tooling to create CF tubes at the size of Starship didn't exist, and would have to be created from scratch at large expense.
- nickff 7y agoSpaceX had CF tooling (most notably including a mandrel), and had built at least one tank. They recently scrapped the tooling, after settling on stainless steel.
- NikolaeVarius 7y ago