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.
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.
I not sure that SpaceX would fare as well since it internally funded without a large back order ledger for BFR and ITS. The question I am asking is the risk worth the reward for the interplanetary transportation system?
I did not include specific program names in this initial post. If I did the 787 would have been an example of the very concern that I have. The 787 cost twice as much to develop as originally planned (40 billion) and the initial delivery was 40 months late. Not all because of composite issues but a good part. The break even point is now the 1100th aircraft, wow! Boeing thought it understood the design issues and bet its future on that aircraft. It had the financial resources to recover. I not sure that SpaceX would fare as well since it internally funded without a large back order ledger for BFR and ITS. The question I am asking is the risk worth the reward for the interplanetary transportation system?
Composites have been around since what? the 1980's. Glock made the first composite framed pistol back in the 1980's. ... I used Glock as an example because ITS will have gravitational stresses taking off and landing. ...
Quote from: spacenut on 04/28/2017 12:37 pmComposites have been around since what? the 1980's. Glock made the first composite framed pistol back in the 1980's. ... I used Glock as an example because ITS will have gravitational stresses taking off and landing. ...It's not a great example, since those frames are made out of fiberglass reinforced nylon, not carbon fiber reinforced epoxy. The mechanical properties are very different, nearly as different as AlLi alloy and CFRP.
Quote from: envy887 on 04/28/2017 04:47 pmQuote from: spacenut on 04/28/2017 12:37 pmComposites have been around since what? the 1980's. Glock made the first composite framed pistol back in the 1980's. ... I used Glock as an example because ITS will have gravitational stresses taking off and landing. ...It's not a great example, since those frames are made out of fiberglass reinforced nylon, not carbon fiber reinforced epoxy. The mechanical properties are very different, nearly as different as AlLi alloy and CFRP.I'm pretty sure modern polymer framed pistols aren't fiberglass reinforced... just plastic, with stamped metal inserts for the rails the slide sits on. The first polymer framed pistol was an HK too, IIRC.
Quote from: ZachF on 05/01/2017 02:43 pmQuote from: envy887 on 04/28/2017 04:47 pmQuote from: spacenut on 04/28/2017 12:37 pmComposites have been around since what? the 1980's. Glock made the first composite framed pistol back in the 1980's. ... I used Glock as an example because ITS will have gravitational stresses taking off and landing. ...It's not a great example, since those frames are made out of fiberglass reinforced nylon, not carbon fiber reinforced epoxy. The mechanical properties are very different, nearly as different as AlLi alloy and CFRP.I'm pretty sure modern polymer framed pistols aren't fiberglass reinforced... just plastic, with stamped metal inserts for the rails the slide sits on. The first polymer framed pistol was an HK too, IIRC.Fiberglass reinforced as in glass-filled nylon. It looks exactly the same as nylon unless you cut it open. It doesn't look like a familiar fiberglass layup (e.g. boat hull) in any way.But composites are used in a lot of high-shock applications, including automotive, aerospace, high-performance bikes, etc.
Maybe for some rifle stocks, but pistol frames are just plastic with metal inserts...
Quote from: testguy on 04/28/2017 07:49 amI did not include specific program names in this initial post. If I did the 787 would have been an example of the very concern that I have. The 787 cost twice as much to develop as originally planned (40 billion) and the initial delivery was 40 months late. Not all because of composite issues but a good part. The break even point is now the 1100th aircraft, wow! Boeing thought it understood the design issues and bet its future on that aircraft. It had the financial resources to recover. I not sure that SpaceX would fare as well since it internally funded without a large back order ledger for BFR and ITS. The question I am asking is the risk worth the reward for the interplanetary transportation system?Worth noting that the experience of building the 787 is likely to make building the ITS easier. As with any pathfinder project, everything afterwards using similar technology is easier.
Quote from: DOCinCT on 10/24/2016 03:08 pm>One secret is where this is? I'll assume it was assembled (and possibly components manufactured) at the location. If they are going to test it on a barge, it has to be somewhere close to water and without lots of low clearance road structures.Not that much of a secret.They said it was built by Janicki Industries.So it is either in Sedro-Woolley or Hamilton Washington.
>One secret is where this is? I'll assume it was assembled (and possibly components manufactured) at the location. If they are going to test it on a barge, it has to be somewhere close to water and without lots of low clearance road structures.
It's not like aluminum doesn't have issues. Aluminum doesn't have an endurance limit under fatigue like steel does, in other words, aluminum keeps getting fatigue even with low loadings. But that's just something you take into account and move on. You don't build airplanes out of steel.I actually think half the reason for composites is the manufacturability improves for some shapes. It's not just performance.
Aluminum could be a fall back but won't because SpaceX doesn't get scared off by new technologies like NASA might.The main issue for composites is oxygen compatibility with cracks, and the fallback there is a metal liner in the oxygen tank. Musk said this himself.It's not like aluminum doesn't have issues. Aluminum doesn't have an endurance limit under fatigue like steel does, in other words, aluminum keeps getting fatigue even with low loadings. But that's just something you take into account and move on. You don't build airplanes out of steel.I actually think half the reason for composites is the manufacturability improves for some shapes. It's not just performance.
I disagree, ITS could be done with aluminum, but would loose payload ability. How much? Don't know. Remember Sea Dragon was all steel pressure fed single engine per stage two stagebut could get 500 tons to LEO. It was around 70-75' in diameter. Aluminium could be a fall back, but would affect payload.
The impressive performance numbers realized for the BFR and ITS are in part due to extensive use of composites in the vehicles structure, airframe and tanks.
Composites have been proven problematic when used in other aerospace projects in the past. Problems have been revealed in parts processing, inspection, repair and durability amongst others that I'm sure this forum can identify. SpaceX, no doubt appreciates the composite issue as demonstrated by their early demonstration of the ITS oxidizer tank and their copy experience. The very size of the BFR and ITS make it difficult to test the structures other than in flight. How else can they subject the stages to the extreme thermal, structural and dynamic environmental conditions that must be survived on multiple cycles. After all, if you think about it, each stage is the size of a small sky scraper. the Mars
My concern is that extensive composite use may once again be a rabbit hole that could sink the Mars aspirations. Could a composite issue identified during flight testing be too late to recover from?
I am not an expert, just witnessed many development problems over the years. The intent of opening this discussion is to solicit thoughts pertaining to composites for BFR and ITS. Why will SpaceX be successful this time? Should all the design eggs be in one basket? It is even feasible to have a viable less risky design. With billions needed for development, with source of funding being internal, it appears that SpaceX must get it right the first time.
I was doing little search for composite manufacturing as I was curious as to how they'd actually make the BFR. NASA ran a research program with Boeing and Grumman around 2013-2016. Boeing produced a 2.4m and 5.5m liquid hydrogen test composite tank and Grumman produced a smaller two segment tank. It was a successful project on a fairly modest budget. It does make large composite tanks feel slightly less exotic when coupled with SpaceX's success with the 12m test tank.Boeing's tank being made:
NASA ran a research program with Boeing and Grumman around 2013-2016. Boeing produced a 2.4m and 5.5m liquid hydrogen test composite tank and Grumman produced a smaller two segment tank. It was a successful project on a fairly modest budget. It does make large composite tanks feel slightly less exotic when coupled with SpaceX's success with the 12m test tank.Boeing's tank being made:
Quote from: Dave G on 10/03/2017 04:45 pmWatching this video, it seems they built the 12m test tank right next to a sea port. Anyone know where?The 12 meter tank was contracted to Janicki Industries in Sedro-Woolley, Washington. They're a composites layup specialist. SpaceX will have a learning curve building these tanks in-house.
Watching this video, it seems they built the 12m test tank right next to a sea port. Anyone know where?
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.When Electron finally made orbit, everybody was talking about the Rutherford's electric turbopumps. But I thought that the composite construction was the more significant accomplishment. Haven't carbon fiber rockets been something of a holy grail for a while now? Is Electron the very first carbon fiber orbital rocket?How similar is Electron's composite to what's expected for BFR? Is it the same type of carbon fiber? Does it have a metal liner in its LOX tanks? How much of the rocket is composite? Interstage, payload fairing, and octaweb all composite too?
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.
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: 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.
Quote from: Proxima_Centauri on 02/18/2018 09:11 pm787's wings are not made of carbon composites, and it is they that carry the fuel.The Boeing 787's wings are carbon fiber composites. See Boeing's web site: http://www.boeing.com/commercial/787/by-design/#/advanced-composite-use
Right now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELV
Quote from: john smith 19 on 02/18/2018 05:11 pmRight now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELVThis is incorrect. COPVs are composite tanks subjected to cryocycles and structural loads and carried through the entire flight. They are used in many vehicles and SpaceX has plenty of experience with them.
Quote from: envy887 on 02/19/2018 01:18 pmQuote from: john smith 19 on 02/18/2018 05:11 pmRight now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELVThis is incorrect. COPVs are composite tanks subjected to cryocycles and structural loads and carried through the entire flight. They are used in many vehicles and SpaceX has plenty of experience with them.Those are aluminum wrapped tanks, they would not scale to BFS propellant tank dimensions. Not applicable.
Quote from: envy887 on 02/19/2018 01:18 pmQuote from: john smith 19 on 02/18/2018 05:11 pmRight now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELVThis is incorrect. COPVs are composite tanks subjected to cryocycles and structural loads and carried through the entire flight. They are used in many vehicles and SpaceX has plenty of experience with them.Irrelevant. COPVs are lined with aluminum. COPVs are orders of magnitude smaller. COPVs are not subject to widely varying environment, since they are immersed in the LOX tank. One major problem with unlined LOX tanks is the energy given off when fibers break under stress. Special matrix material has been used to address this problem. The CH4 tanks are not as much of a problem.John
SpaceX also said they would line the BFR tanks with invar if necessary, but they don't expect it to be needed.
What do you mean by "widely varying environment"?
The LOX tanks will hold cryogenic LOX and will use autogenous pressurization. Autogenous pressurization means sending hot, gaseous oxygen from the engines into the tanks. Talk about "widely varying environment".
They are not Al-wrapped, they are Al-lined.
They are not Al-wrapped, they are Al-lined. The LOX-facing side is CRFP, not Al. SpaceX also said they would line the BFR tanks with invar if necessary, but they don't expect it to be needed.
The COPV CRFP is unlined on the LOX side.What do you mean by "widely varying environment"? They go from STP to cryo temps and flight pressures at negative and positive g loads (they float in LOX but sink in GHe). That's the same environments that the main tanks will see, except for entry (which is demonstrated by the interstage, legs and fairings).
I find this thread interesting Does anyone have a bona fide source that the Electron tanks are free from metal? If Rocket Lab only claim that they use carbon fibre composites for their tanks, then I suppose it could well be that the carbon fibre is used as part of the load-carrying honeycomb sandwich. At the very least, the tanks may well be lined with an Al-Li "membrane".
Propellant tanks are constructed entirely from carbon fiber composite.
Quote from: envy887 on 02/19/2018 03:03 pmThey are not Al-wrapped, they are Al-lined. The LOX-facing side is CRFP, not Al. SpaceX also said they would line the BFR tanks with invar if necessary, but they don't expect it to be needed.Weren't they implicated in 2 F9 stage failures?
Quote from: envy887The COPV CRFP is unlined on the LOX side.What do you mean by "widely varying environment"? They go from STP to cryo temps and flight pressures at negative and positive g loads (they float in LOX but sink in GHe). That's the same environments that the main tanks will see, except for entry (which is demonstrated by the interstage, legs and fairings).Except they will be "the main tank" It seems a key issue is energy release if fibers are split within the tank, and the classic way to deal with that is to "grade" the inside of the tank (and possibly the outside, depending what it's immersed in) from fiber to a pure resin "skin" layer. However the "hot" Oxygen pressurization system does complicate things. But keep in mind that the "hot" Hydrogen in the RL10 turbine drive is only about 100c, allowing turbines of Aluminum.So the question would be how "hot" is this Oxygen flow? -100c? (IE 173k) 0c? 100c?
Quote from: matthewkantar on 02/19/2018 02:43 pmQuote from: envy887 on 02/19/2018 01:18 pmQuote from: john smith 19 on 02/18/2018 05:11 pmRight now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELVThis is incorrect. COPVs are composite tanks subjected to cryocycles and structural loads and carried through the entire flight. They are used in many vehicles and SpaceX has plenty of experience with them.Those are aluminum wrapped tanks, they would not scale to BFS propellant tank dimensions. Not applicable.They are not Al-wrapped, they are Al-lined. The LOX-facing side is CRFP, not Al. SpaceX also said they would line the BFR tanks with invar if necessary, but they don't expect it to be needed.The construction method for COPVs would not scale, but the COPV experience shows that the material itself is capable of cryocycles, structural loads, and flight with suitable tank construction.Quote from: livingjw on 02/19/2018 02:41 pmQuote from: envy887 on 02/19/2018 01:18 pmQuote from: john smith 19 on 02/18/2018 05:11 pmRight now the only vehicle that's taken composite tankage through the whole flight regime to orbit is Rocket Labs Electron ELVThis is incorrect. COPVs are composite tanks subjected to cryocycles and structural loads and carried through the entire flight. They are used in many vehicles and SpaceX has plenty of experience with them.Irrelevant. COPVs are lined with aluminum. COPVs are orders of magnitude smaller. COPVs are not subject to widely varying environment, since they are immersed in the LOX tank. One major problem with unlined LOX tanks is the energy given off when fibers break under stress. Special matrix material has been used to address this problem. The CH4 tanks are not as much of a problem.JohnThe COPV CRFP is unlined on the LOX side.What do you mean by "widely varying environment"? They go from STP to cryo temps and flight pressures at negative and positive g loads (they float in LOX but sink in GHe). That's the same environments that the main tanks will see, except for entry (which is demonstrated by the interstage, legs and fairings).
nickel-iron-lead isn't light weight. How thick a layer do they need? Does it flake off? Or wear away? How much mass is that for large tanks?
AIUI the layer would be thin, mainly to protect the carbon from warm to hot oxygen generated for autogenous pressurization. Invar because of its low coefficient of thermal expansion.
I believe the shuttle lox tank used about 100 deg c GOX for tank pressurization.John
Quote from: Norm38 on 02/20/2018 03:17 amnickel-iron-lead isn't light weight. How thick a layer do they need? Does it flake off? Or wear away? How much mass is that for large tanks?Once again: An Invar liner is the last resort. Elon said that they look for a coating that can be sprayed on.
Another solution could the inner most layers of the tanks be made from something like Nonburnite which can handle -260C to +280C.This should exceed anything they'll see in service by a good margin.https://omnexus.specialchem.com/tech-library/article/nonburning-high-heat-composite-material-of-the-future
I wonder if the coating would be spray foam insulation, BFS needs insulation for deep space and Mars surface (to avoid freezing out dry ice). But urethane foam seems like it would be just as bad as carbon epoxy in the face of hot GOX. A silica fiber based insulation sounds like a better bet but I don't know if they could spray it.
Quote from: Patchouli on 02/21/2018 04:49 amAnother solution could the inner most layers of the tanks be made from something like Nonburnite which can handle -260C to +280C.This should exceed anything they'll see in service by a good margin.https://omnexus.specialchem.com/tech-library/article/nonburning-high-heat-composite-material-of-the-futureUnfortunately XCOR is now defunct. Does anyone know what happened to the nonburnite IP?Quote from: envy887 on 02/21/2018 03:21 amI wonder if the coating would be spray foam insulation, BFS needs insulation for deep space and Mars surface (to avoid freezing out dry ice). But urethane foam seems like it would be just as bad as carbon epoxy in the face of hot GOX. A silica fiber based insulation sounds like a better bet but I don't know if they could spray it.Such materials do exist and are in use for refurbishing furnaces. I've no idea how fragile or heavy they are.
Not heavy at all, but lightweight silica materials rather brittle. Aerogel and the Shuttle tiles are two examples.
Now that we've seen the actual composite section, there's an attempt at reddit to estimate its thickness: https://www.reddit.com/r/SpaceXLounge/comments/9javua/quick_bfr_structural_carbon_fiberre_calculations/, the result is 12 to 25mm.The teslarati article has a photo that gives more details, by trying to complete the circle I estimated the thickness (the white border) as 50mm.So does this thickness seem excessive? I couldn't find the thickness of the NASA/Boeing test tank. For aircraft like A350, it looks like the composite fuselage is only a few mm thick.
It could be two thin walls 50 mm apart with flutes between. This is how Boeing and NASA constructed the 5 m diameter composite test tank.https://www.nasa.gov/feature/case-study-nasaboeing-composite-launch-vehicle-fuel-tank-scores-firsts
Quote from: envy887 on 10/01/2018 01:10 pmIt could be two thin walls 50 mm apart with flutes between. This is how Boeing and NASA constructed the 5 m diameter composite test tank.https://www.nasa.gov/feature/case-study-nasaboeing-composite-launch-vehicle-fuel-tank-scores-firstsI can not find any references in the Composite Cryotank Technologies and Demonstration project towards applicability to reusable launch vehicles. As I understand it the project requirements were for disposable launch vehicle technologies.I'm no composites expert but the flutes do not strike me as a stress cycle life enhancing solution. Intuition may be wrong here but the opppaite.seems more likely. To paraphrase Dan Raskin's view from the top talk: as few miracles as possible please.
Composite sandwich panels are very common in aerospace applications, since like isogrids/orthogrids they reduce weight while increasing strength and stiffness. The savings over solid structures are massive, which means margins can be higher, which makes reuse much easier.
Quote from: envy887 on 10/01/2018 01:46 pm Composite sandwich panels are very common in aerospace applications, since like isogrids/orthogrids they reduce weight while increasing strength and stiffness. The savings over solid structures are massive, which means margins can be higher, which makes reuse much easier.Granted. How many of these sandwich constructions see use as multi-cycle mild-cryo containers? You'll notice F9 fairing is sandwich, fuselage is not, not the bulk of it at the very least. Airframes rarely carry cryogenic fluid.The savings are moot if it introduces catastrophic failure modes.
Detecting delaminations between the sandwitch faces can be a problem, as you can't simply inspect in the middle.
Alternatively SpaceX could easily and cheaply use the filament winding process to create a crude isogrid via selective thickening of some axial and helical paths during winding process. Eg 5mm average wall thickness with wide 20-30mm thick ribs over ~10% of surface area.
You don’t need to embed the ultrasonic sensors. You can do inspection with a fluid filled finger.Digital X ray sensors can also be done. Doesn’t require embedding either.Parts can be repaired with resign injection and patching techniques.
The impressive performance numbers realized for the BFR and ITS are in part due to extensive use of composites in the vehicles structure, airframe and tanks. Composites have been proven problematic when used in other aerospace projects in the past. Problems have been revealed in parts processing, inspection, repair and durability amongst others that I'm sure this forum can identify. SpaceX, no doubt appreciates the composite issue as demonstrated by their early demonstration of the ITS oxidizer tank and their copy experience. The very size of the BFR and ITS make it difficult to test the structures other than in flight. How else can they subject the stages to the extreme thermal, structural and dynamic environmental conditions that must be survived on multiple cycles. After all, if you think about it, each stage is the size of a small sky scraper.My concern is that extensive composite use may once again be a rabbit hole that could sink the Mars aspirations. Could a composite issue identified during flight testing be too late to recover from? I am not an expert, just witnessed many development problems over the years. The intent of opening this discussion is to solicit thoughts pertaining to composites for BFR and ITS. Why will SpaceX be successful this time? Should all the design eggs be in one basket? Is it even feasible to have a viable less risky design. With billions needed for development, with source of funding being internal, it appears that SpaceX must get it right the first time.My intent is not to be a naysayer because I couldn't be more thrilled that SpaceX has taken upon themselves to provide the world with a low cost interplanetary transportation system. I hope this discussion helps convince me and others that they are on the right path pertaining to composites.
Quote from: testguy on 04/27/2017 05:51 pmThe impressive performance numbers realized for the BFR and ITS are in part due to extensive use of composites in the vehicles structure, airframe and tanks. Composites have been proven problematic when used in other aerospace projects in the past. Problems have been revealed in parts processing, inspection, repair and durability amongst others that I'm sure this forum can identify. SpaceX, no doubt appreciates the composite issue as demonstrated by their early demonstration of the ITS oxidizer tank and their copy experience. The very size of the BFR and ITS make it difficult to test the structures other than in flight. How else can they subject the stages to the extreme thermal, structural and dynamic environmental conditions that must be survived on multiple cycles. After all, if you think about it, each stage is the size of a small sky scraper.My concern is that extensive composite use may once again be a rabbit hole that could sink the Mars aspirations. Could a composite issue identified during flight testing be too late to recover from? I am not an expert, just witnessed many development problems over the years. The intent of opening this discussion is to solicit thoughts pertaining to composites for BFR and ITS. Why will SpaceX be successful this time? Should all the design eggs be in one basket? Is it even feasible to have a viable less risky design. With billions needed for development, with source of funding being internal, it appears that SpaceX must get it right the first time.My intent is not to be a naysayer because I couldn't be more thrilled that SpaceX has taken upon themselves to provide the world with a low cost interplanetary transportation system. I hope this discussion helps convince me and others that they are on the right path pertaining to composites.I raised the concern about composites 1 1/2 years ago and it was well discussed in this forum. I suspect, rather than know, that problems were identified in the Starship composites that is causing the change. Thank goodness SpaceX has identified an alternative that will surprising expedite the Starship schedule while also reducing costs. Better to make the change now rather than after flight tests have begun.
Quote from: testguy on 11/26/2018 03:51 pmQuote from: testguy on 04/27/2017 05:51 pmThe impressive performance numbers realized for the BFR and ITS are in part due to extensive use of composites in the vehicles structure, airframe and tanks. Composites have been proven problematic when used in other aerospace projects in the past. Problems have been revealed in parts processing, inspection, repair and durability amongst others that I'm sure this forum can identify. SpaceX, no doubt appreciates the composite issue as demonstrated by their early demonstration of the ITS oxidizer tank and their copy experience. The very size of the BFR and ITS make it difficult to test the structures other than in flight. How else can they subject the stages to the extreme thermal, structural and dynamic environmental conditions that must be survived on multiple cycles. After all, if you think about it, each stage is the size of a small sky scraper.My concern is that extensive composite use may once again be a rabbit hole that could sink the Mars aspirations. Could a composite issue identified during flight testing be too late to recover from? I am not an expert, just witnessed many development problems over the years. The intent of opening this discussion is to solicit thoughts pertaining to composites for BFR and ITS. Why will SpaceX be successful this time? Should all the design eggs be in one basket? Is it even feasible to have a viable less risky design. With billions needed for development, with source of funding being internal, it appears that SpaceX must get it right the first time.My intent is not to be a naysayer because I couldn't be more thrilled that SpaceX has taken upon themselves to provide the world with a low cost interplanetary transportation system. I hope this discussion helps convince me and others that they are on the right path pertaining to composites.I raised the concern about composites 1 1/2 years ago and it was well discussed in this forum. I suspect, rather than know, that problems were identified in the Starship composites that is causing the change. Thank goodness SpaceX has identified an alternative that will surprising expedite the Starship schedule while also reducing costs. Better to make the change now rather than after flight tests have begun.There's no indication that the "alternative" isn't also a composite. There are many CFRPs and many, many more types of other composites.
Perhaps it is time to retire this thread as Super Heavy/Starship (BFR/BFS) will now be made of metal.
How about the booster still be made of composite.
Aside from his confirmation that SpaceX has moved to metallic tanks and structures on BFR’s spaceship upper stage and booster (Starship/Super Heavy), ...
That article sounds like it was written before Elon's "metal hull" tweet. SpaceX moving too fast for space reporting, i guess.