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.
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: 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.
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. ...
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.
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?
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?