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#21
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Were liquid boosters on Shuttle ever realistic?
JF Mezei wrote:
On 2017-10-26 16:27, Fred J. McCall wrote: And they have to be "certified" for a magnitude (or multiple magnitudes in the case of something like BFR) more fill and drain cycles if they're supposed to be reusable. When dealing with composites, while you certify based on your tests, must it not be engineered to be refillable an infinite number of times? Nothing is "refillable an infinite number of times". Your question isn't comprehensible, so it can't be answered. Yes, you engineer to a maximum pressure (validate with destructive test). But when you certify a tank for X refills, isn't it more akin to stating that after X refills, you saw no defects develop? (as opposed to stating that defects appear after each fill, but tank will hold until it has Y defects). It's a combination of both of those and you don't just build something random and then determine things by test. You design to performance targets. Carbon fibre structures quickly lose their strength/integrity as soon as there is a defect. That depends on the defect. Nothing goes from pristine to instantaneous failure. A carbon fibre bike won't last long if a crack develops. Likely won't get you home because with each bump on road, the crack will get much worse. Fortunately I don't think any carbon bikes are used in SpaceX boosters. -- "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 |
#22
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Were liquid boosters on Shuttle ever realistic?
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#23
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Were liquid boosters on Shuttle ever realistic?
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#24
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Were liquid boosters on Shuttle ever realistic?
"Fred J. McCall" wrote in message
... "Greg \(Strider\) Moore" wrote: "Fred J. McCall" wrote in message . .. There is no such thing as assembly line production 'spewing out' rocket engines. It made sense to use Merlin engines because the idea was to have three identical cores for Falcon Heavy, sort of like what Delta IV Heavy does. In the event, Musk found they couldn't do that and that they couldn't just use three Falcon 9 cores for Falcon Heavy. The side boosters are now different from the central 'core'. What are the differences? Last I knew the side boosters for the primary flight are B1023.2 and B1025.2 (i.e 2nd flight for those two boosters) It's mostly got to do with mechanical loading. The side boosters are close (but not an exact match) for what they fly on Falcon 9. They're only slightly modified so as to be able to take structural loading from the attachment points on the sides rather than straight down through the center of the core. I can see that. As you say, must be fairly slight. Interesting though. The center booster requires a lot more structural work to stand loads, both the side loads from the two attached boosters and the increased load on the front of the booster from the second stage and payload. Yeah, I figured the central core would be different. Musk himself has said that he doesn't necessarily expect the first launch attempt to reach orbit and would consider it getting far enough away to avoid pad damage a win. Yeah, he's doing a good job of lowering expectations. I'm pretty sure he's a lot more confident than that, or else he wouldn't risk a launch. Look at how many Falcon 9 launches failed before they got a success. You mean 0? Landing took some tries, but the launches were successful. According to Musk, Falcon Heavy was "shockingly difficult" to develop. It was originally supposed to use fuel cross-feed among the three cores, but that proved too difficult and was dropped. Yeah. That I knew. And makes sense. Gets some advantages, but it's a feature that can be added on later. It was originally supposed to be three 'standard' Falcon 9 cores (with Falcon 9 eating the additional structure) but now the center booster is different from the side boosters. Yes, it really is rocket science... Ayup. Or at least rocket engineering. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#25
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Were liquid boosters on Shuttle ever realistic?
"Greg \(Strider\) Moore" wrote:
"Fred J. McCall" wrote in message .. . Look at how many Falcon 9 launches failed before they got a success. You mean 0? Landing took some tries, but the launches were successful. I read somewhere in passing that the first three launches failed. I now think that author confused Falcon 9 with Falcon 1. -- "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 |
#26
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Were liquid boosters on Shuttle ever realistic?
"Fred J. McCall" wrote in message
... "Greg \(Strider\) Moore" wrote: "Fred J. McCall" wrote in message . .. Look at how many Falcon 9 launches failed before they got a success. You mean 0? Landing took some tries, but the launches were successful. I read somewhere in passing that the first three launches failed. I now think that author confused Falcon 9 with Falcon 1. Yeah, Falcon 1 definitely had teething problems. But to be honest, I did have to look it up just to make sure I remembered the Falcon 9 correctly. That said, the first 3 flights did all have test payloads, "just in case". There have only been two Falcon 9 "launch" failures (i.e. ignoring all the landing failures). The first was the inflight one where I believe a strut collapsed caused structural damage. The second was of course the fueling test on the pad. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#27
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Were liquid boosters on Shuttle ever realistic?
"JF Mezei" wrote in message
web.com... On 2017-10-27 06:27, Jeff Findley wrote: Again, SpaceX has publicly stated the first reuse of a first stage cost less than half the cost of building a new one. Is that PR speak or "auditor" speak? The first reflown stage was not the first landed stage. Say the first reflown stage uses some engines that were refurbished from other recovered stages, and their reburb costs billed to "R&D". Not saying this is what happened, but just one way to skew numbers for good PR. My understanding, but I have no reference for it is engines stay with the booster. Customers are already choosing to fly on refurbished first stages because it gets their payloads in orbit faster But lets wait until SpaceX actually delivers on a launch rate. Not doubting it will, but the sample size right now is too low to allow conclusions. Actually delivers? They've done 15 flights this year and expect at least 4 more (I'm not counting Heavy as I expect that will slip). That's a pretty damn good flight rate. They've shown an ability to have a cadence of every 15 days. This is pretty impressive and does not appear to have been a surge attempt, but simple operations. SpaceX has done proof of concept. It appears extrememy promising. But it hasn't yet proven it will deliver that launch rate. Just because SpaceX has very good image that gives people confidence it will deliver doesn't provide proof that it will deliver. We are still talking about ODDs that SpaceX will deliver being very high. So if you were betting, you'd bet SpaceX will deliver. But we're still talking about odds because this is too new to have empirical evidence. Granted, we're still at the stage where any one failure still has a statistically significant impact, but 41 out of 43 is pretty good. AND that includes 378 flight firings of booster engines (one failure was on the ground, so I'm not counting that one). And 41 in-flight firings of 2nd stage engines. This excludes all testing both on the stand and on flights like grasshopper. Actually, I just realized my numbers are too low, since I'm forgetting the refiring of the engines for landing. So the engine numbers ARE statistically significant. So they're making their numbers and giving us evidence. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#28
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Were liquid boosters on Shuttle ever realistic?
JF Mezei wrote:
On 2017-10-27 06:27, Jeff Findley wrote: Again, SpaceX has publicly stated the first reuse of a first stage cost less than half the cost of building a new one. Is that PR speak or "auditor" speak? The first reflown stage was not the first landed stage. Say the first reflown stage uses some engines that were refurbished from other recovered stages, and their reburb costs billed to "R&D". Not saying this is what happened, but just one way to skew numbers for good PR. You try far too hard to muddy things up. Must they provide you with an inventory of every ****ing nut, bolt, and rivet to assure you they're all the same booster? Customers are already choosing to fly on refurbished first stages because it gets their payloads in orbit faster But lets wait until SpaceX actually delivers on a launch rate. Not doubting it will, but the sample size right now is too low to allow conclusions. What are you jabbering about now? SpaceX has done proof of concept. It appears extrememy promising. But it hasn't yet proven it will deliver that launch rate. Just because SpaceX has very good image that gives people confidence it will deliver doesn't provide proof that it will deliver. We are still talking about ODDs that SpaceX will deliver being very high. So if you were betting, you'd bet SpaceX will deliver. But we're still talking about odds because this is too new to have empirical evidence. Then you will NEVER have 'empirical evidence' that you will expect because they could launch 100 in a row successfully and then have 20 in a row fail. It's always 'odds', you nitwit. Life is a bet at long odds. -- "We come into the world and take our chances. Fate is just the weight of circumstances. That's the way that Lady Luck dances. Roll the bones...." -- "Roll The Bones", Rush |
#30
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Were liquid boosters on Shuttle ever realistic?
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