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BFS drops composite construction
I saw a report today that SpaceX was dropping composites for tanks and
main structure on BFS in favor of using "heavy metal" (Musk's phrase). It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#2
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BFS drops composite construction
In article ,
says... I saw a report today that SpaceX was dropping composites for tanks and main structure on BFS in favor of using "heavy metal" (Musk's phrase). He Tweeted about it in replies to Everyday Astronaut. https://twitter.com/elonmusk/status/1071578086418788352 From above: Everyday Astronaut: their new Starship and Super Heavy will be all carbon composite (mostly) Elon Musk: The new design is metal Elon Musk: Fairly heavy metal, but extremely strong Everyday Astronaut: It seems like you?ve made some really big changes recently. Is this why we didn?t get a big technical rundown at #dearmoon or IAC this year? So what?s with the big mandrels at the port? Or those carbon tanks shown off for the past couple years? Elon Musk: Yes Malcom Head: Is Super Heavy in development at all, or just starship right now? Elon Musk: Both, but demo Starship is being built now, whereas Super Heavy hardware will start getting built in spring All articles I've seen afterwards don't contain any new information, just speculation beyond the original Tweets which I quoted above. It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. Could be they decided composites posed too much technical risk, so they've retired that risk by switching to a more conventional metal design. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. I'm also wondering if the changes had to do with the thermal protection scheme for BFS/Starship. The nice thing about metal is that it conducts heat better than a carbon fiber composite would. That might be an advantage during reentry. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
#3
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BFS drops composite construction
On Dec/10/2018 at 06:54, Jeff Findley wrote :
In article , says... I saw a report today that SpaceX was dropping composites for tanks and main structure on BFS in favor of using "heavy metal" (Musk's phrase). He Tweeted about it in replies to Everyday Astronaut. https://twitter.com/elonmusk/status/1071578086418788352 From above: Everyday Astronaut: their new Starship and Super Heavy will be all carbon composite (mostly) Elon Musk: The new design is metal Elon Musk: Fairly heavy metal, but extremely strong Everyday Astronaut: It seems like you?ve made some really big changes recently. Is this why we didn?t get a big technical rundown at #dearmoon or IAC this year? So what?s with the big mandrels at the port? Or those carbon tanks shown off for the past couple years? Elon Musk: Yes Malcom Head: Is Super Heavy in development at all, or just starship right now? Elon Musk: Both, but demo Starship is being built now, whereas Super Heavy hardware will start getting built in spring All articles I've seen afterwards don't contain any new information, just speculation beyond the original Tweets which I quoted above. It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. Could be they decided composites posed too much technical risk, so they've retired that risk by switching to a more conventional metal design. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. I'm also wondering if the changes had to do with the thermal protection scheme for BFS/Starship. The nice thing about metal is that it conducts heat better than a carbon fiber composite would. That might be an advantage during reentry. I would think that you've got it right about thermal protection. Alain Fournier |
#4
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BFS drops composite construction
Jeff Findley wrote on Mon, 10 Dec 2018
06:54:42 -0500: In article , says... I saw a report today that SpaceX was dropping composites for tanks and main structure on BFS in favor of using "heavy metal" (Musk's phrase). He Tweeted about it in replies to Everyday Astronaut. https://twitter.com/elonmusk/status/1071578086418788352 From above: Everyday Astronaut: their new Starship and Super Heavy will be all carbon composite (mostly) Elon Musk: The new design is metal Elon Musk: Fairly heavy metal, but extremely strong Everyday Astronaut: It seems like you?ve made some really big changes recently. Is this why we didn?t get a big technical rundown at #dearmoon or IAC this year? So what?s with the big mandrels at the port? Or those carbon tanks shown off for the past couple years? Elon Musk: Yes Malcom Head: Is Super Heavy in development at all, or just starship right now? Elon Musk: Both, but demo Starship is being built now, whereas Super Heavy hardware will start getting built in spring All articles I've seen afterwards don't contain any new information, just speculation beyond the original Tweets which I quoted above. It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. Could be they decided composites posed too much technical risk, so they've retired that risk by switching to a more conventional metal design. Well, that would be cost/schedule. Given his wording about "heavy metal" I don't expect it will be the 'conventional' metal. Back in the dim past around here there was a guy who proposed using swaged steels for booster construction of a 'Big Dumb Booster'. There was some weight penalty over 'conventional' materials, but he calculated that it was not as much as you might think and that construction costs would be much lower. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. I'm also wondering if the changes had to do with the thermal protection scheme for BFS/Starship. The nice thing about metal is that it conducts heat better than a carbon fiber composite would. That might be an advantage during reentry. Perhaps, although I'd think a TPS would, well, 'P' from 'T' and not rely on a conducting hull, which could leave you prone to heat damage. Carbon fiber tends to be very heat resistant, which means that replacing it in exposed structures like vehicle hull will probably require some sort of refractory metal. Given the difference in density between the two, going to such a metal hull would indeed be heavy. Musk was asked several times just which metal he was referring to and avoided the question each and every time. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#5
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BFS drops composite construction
d to do with the thermal protection
scheme for BFS/Starship. The nice thing about metal is that it conducts heat better than a carbon fiber composite would. That might be an advantage during reentry. Heat capacity or thermal resilience is certainly an issue. Another is the ability to use the tanks as a hull when pressurized. Metal hulls can be possibly reduced in thickness to compete with composites. At a certain point thermal properties of metal may make metal superior. If Musk has only a fuselage material as the change then my comment does not apply. |
#6
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BFS drops composite construction
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#7
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BFS drops composite construction
"Fred J. McCall" wrote in message ... I saw a report today that SpaceX was dropping composites for tanks and main structure on BFS in favor of using "heavy metal" (Musk's phrase). It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. I'm not too surpised considering that NASA and Locked-Martin spent years trying to build composite tanks for the X-33, which then failed. But is this the change that Musk called 'counter intuitive'? |
#9
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BFS drops composite construction
On 12/10/2018 1:39 PM, Fred J. McCall wrote:
Well, that would be cost/schedule. Given his wording about "heavy metal" I don't expect it will be the 'conventional' metal. [snip] Musk was asked several times just which metal he was referring to and avoided the question each and every time. A variant of Inconel or SpaceX's SX-300? They certainly have experience with it. Maybe they plan to spin cast it in solutionized form and weld two hemispheres after age hardening? Stupid wild ass guesses are fun... Note Wikipedia references it as useful in "pressure vessels" (under Uses, see) https://en.wikipedia.org/wiki/Inconel Dave |
#10
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BFS drops composite construction
In article , says...
Speaking of dim past... Here's a gem from Paul D. reposting a passage about Robert Truax from Ed Regis on Thor vs Agena. Paul Dietz 2/17/94 Sea Dragon (was reviving saturn v) In article (Doug Jones) writes: snip So if all this was true, if engineering, lab tests, documentation and so forth didn't determine a launch vehicle's price tag, *what did*? Essentially, three things: parts count, design margins, and innovation. Other things being equal, the more parts a machine had, the more it was going to cost. The more you wanted it to approach perfection, the more expensive it would end up being. And finally, the newer and more pioneering the design, the more you'd end up paying for it. "We came up with a set of ground rules for designing a launch vehicle," Truax said. "Make it big, make it simple, make it reusable. Don't push the state of the art, and don't make it any more reliable that it has to be. And *never* mix people and cargo, because the reliability requirements are worlds apart. For people you can have a very small vehicle on which you lavish all your attention; everything else is cargo, and for this all you need is a Big Dumb Booster." -------------------- Paul F. Dietz "If I'd been in my grave, I'd have rolled over." R. Truax on the decision to build the Space Shuttle I think we're seeing some of these rules being applied today by SpaceX (simpler engines and reuse), but not to the extent that Big Dumb Booster would have. We'll see if much of this applies to BFR/BFS. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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