Is the BFR tankage a composite over-wrap of a metal liner? I thought it was pure carbon composite which I believe is the same as Electron. Could be way off here...
In short, a composite tank consists of a thin metallic liner overwrapped with a web of light-weight carbon fibres infused with resin.
So this is a fairly significant technical challenge to make deeply cryogenic tanks out of carbon fiber, and it's only recently that we think the carbon fiber technology has gotten to the point where we can actually do this without having to create a liner — some sort of metal liner, or other liner, on the inside of the tanks, which would add mass and complexity.
So does RocketLab's successful flight of Electron retire any risk for BFR? Sure, it's only the size of Falcon 1, but it's still an honest-to-goodness carbon fiber, orbital rocket.
All examples of composite use are small and warm compared to its. Good example of failure is x33. It was a long time ago by space tech standards.
Conclusion: Using composites may not be high risk based upon known experience in the industry.
Quote from: freddo411 on 02/15/2018 02:56 pmConclusion: Using composites may not be high risk based upon known experience in the industry. None of the carbon fiber projects to date have used the material to contain sub cooled LOX, hot(ish) gaseous oxygen, and liquid methane. These tanks will be cycled hundreds of times and expect to store these propellants for months on end. It will have to be operated in a vacuum, survive reentry, etc etc.R and D money has been put into these materials for decades, so there is some experience here and there in areas that will be helpful, but I think "high risk" is accurate.
Quote from: Robotbeat on 04/28/2017 12:56 amQuote from: rsdavis9 on 04/28/2017 12:49 amAll examples of composite use are small and warm compared to its. Good example of failure is x33. It was a long time ago by space tech standards.787 is not small. It's enormous. Wings also composite. X-33 was, of course, liquid hydrogen, which is proportionally further from liquid oxygen temperatures than liquid oxygen is to room temperature (referring to ratio of absolute temperatures). The BFR and a 787-10 are basically the same length.Plus my understanding is what doomed X-33 was the complex shape of the tank. Which is not appliccable to ITS.
Quote from: rsdavis9 on 04/28/2017 12:49 amAll examples of composite use are small and warm compared to its. Good example of failure is x33. It was a long time ago by space tech standards.787 is not small. It's enormous. Wings also composite. X-33 was, of course, liquid hydrogen, which is proportionally further from liquid oxygen temperatures than liquid oxygen is to room temperature (referring to ratio of absolute temperatures). The BFR and a 787-10 are basically the same length.
Quote from: matthewkantar on 02/15/2018 03:19 pmQuote from: freddo411 on 02/15/2018 02:56 pmConclusion: Using composites may not be high risk based upon known experience in the industry. None of the carbon fiber projects to date have used the material to contain sub cooled LOX, hot(ish) gaseous oxygen, and liquid methane. These tanks will be cycled hundreds of times and expect to store these propellants for months on end. It will have to be operated in a vacuum, survive reentry, etc etc.R and D money has been put into these materials for decades, so there is some experience here and there in areas that will be helpful, but I think "high risk" is accurate.I think "uncertain risk" characterizes the situation better. High risk applies to risks that are understood, and which you can, if you will, compute a probability of a problem happening. It's not as though there is no knowledge of the materials; as you say, they've been used in many ways for decades. We just don't know what will happen in new environments, and won't, until further testing is done.Labeling the situation "high risk" overstates (and mischaracterizes) the situation.
BFR isn't using LH2, lobed tanks, or honeycomb sandwiches, so it don't think it's all that relevant.
Another risk is how well will the composite structure handle reentry?Though Dream Chaser flying would answer some of these unknowns.
Haven't seen this document in the forum: Design, Manufacture and Test of Cryotank Components, it has a nice history section which lists past projects with composite tanks, plus tons of details about Boeing/NASA's recent composite tank project.
Clearly shows how much work has been done and how complex tanks are. Sometimes member comments make it sound so simple, and that SpaceX has done it all. They are standing on the shoulders of others. As we all do.
Does anyone have an idea of their current state of progress with BFR tanks? After the big press blitz with pictures of Elon standing in front of a giant tank, they hauled it out to sea for a LO2 fill test, and well.. it apparently came back like this: https://imgur.com/a/bGHR6 Nothing on the press circuit since then.
There is a long and growing experience base in aerospace with composites. As mentioned already, 787 is largely composite. The A380 has significant usage: http://www.iccm-central.org/Proceedings/ICCM13proceedings/SITE/PAPERS/paper-1695.pdfThe B2 is largely composite. All of these are very large, and they have significant service histories. RocketLab's new orbital rocket just succeed while using composite LOX and Kero tanks.SpaceX is using suppliers like Janicki that have built some of the above.Conclusion: Using composites may not be high risk based upon known experience in the industry.
787's wings are not made of carbon composites, and it is they that carry the fuel.