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SpaceX just did a full duration test firing of a recovered 1st stage
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SpaceX just did a full duration test firing of a recovered 1st stage
JF Mezei wrote:
When burning fossil fuels such as Kerosene, how much does that affect resusability because of carbon/soot residue ? It depends. .. Would any such residue cause any abrasion or does combustion happen at a point where it no longer matters much? The issue isn't 'abrasion'. The issue is more 'gunk'. Also, while there was discussion of tank reusability, what about all the metal structures through which LOX flows (pipes etc) ? Apart from temperature variations that could weaken the metal, would oxydation become a problem with time ? (LOX tends to oxydize stuff, right ? ) Thermal cycling is a concern. Oxidation not so much. And it's reuse of the whole stage being talked about, not just tanks. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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SpaceX just did a full duration test firing of a recovered 1st stage
JF Mezei wrote:
On 2016-08-01 13:19, Rick Jones wrote: I suppose even one "actual" launch of the stage is not too far from crossing the Rubicon, but why wait for a successfully returned stage to do this testing? I think there is more to it than igniting engines a few times. Structural issues from impact of landing, exposure to cold of space and then land back in warm humid ocean, and I assume there is some warming of skmin due to friction during launch and re-entry. Consider this theoretical scenario: First one is fine, but they see damage to the one that landed hard and had 1 leg compress. They will want to draw some line below which damage is not expected and above which special inspections are needed. Drawing that line will require multiple landed stages to get an idea of what sort of landing G force is OK. Test firings don't help. Jesus, are you back on this again? If the compression core doesn't compress, there is no structural damage. If there's no visible fire damage, there is no thermal damage. Lines drawn. Now STFU, you ignorant yammerhead. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#24
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SpaceX just did a full duration test firing of a recovered 1st stage
Vaughn Simon wrote:
On 8/1/2016 7:06 PM, Rick Jones wrote: But will they really learn that much more from N (greater than one or two as you implied from "life leader") iterations of "fill, fire and inspect" on the ground from a stage which has been launched only once than from one that wasn't launched? I get your point but... Given that they have several recovered boosters now, why would they use a new one? And if they DID use a new one, everyone would ask "why not a recovered one? What are they trying to hide?" Indeed. My point I suppose is similar to your question at the end - why did they take so long to start when they could have started with a non-recovered stage? The only thing that comes to mind, and I suppose it is a non-trivial consideration, is that the recovered stage is comparatively inexpensive compared to a never-flown one. Some customer has already paid for its construction. Also, I am sure that SpaceX has tested enough Merlin engines on their test stands to have a very educated idea about their MTBF without even bothering to test a recovered booster. IMO, Part of the point of this present testing of a recovered booster surely is to convince customers and underwriters that pre-used boosters can be a safe bet. In other words, it's not just science and engineering that's happening here, it's also a public relations and sales campaign. Which is why I wonder why it took them so long to start it. I'd like to think that I'm at least as much "peanut gallery" as the potential customers for "Elon's Lightly-Used Rocket Stages." As such, would they actually accept ground-based static fires? I'd think they would want to see actual launches of the stage. rick jones -- denial, anger, bargaining, depression, acceptance, rebirth... where do you want to be today? these opinions are mine, all mine; HPE might not want them anyway... feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH... |
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SpaceX just did a full duration test firing of a recovered 1st stage
Rick Jones wrote:
Indeed. My point I suppose is similar to your question at the end - why did they take so long to start when they could have started with a non-recovered stage? The only thing that comes to mind, and I suppose it is a non-trivial consideration, is that the recovered stage is comparatively inexpensive compared to a never-flown one. Some customer has already paid for its construction. I thought someone had already offered a pretty reasonable explanation for that. Until you've shown you can recover a high enough percentage of boosters to make reuse worthwhile, why spend the money on the test firing program? That's not exactly cheap, either. -- "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 |
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SpaceX just did a full duration test firing of a recovered 1st stage
On Tuesday, August 2, 2016 at 5:25:38 PM UTC+12, Fred J. McCall wrote:
JF Mezei wrote: On 2016-08-01 13:19, Rick Jones wrote: I suppose even one "actual" launch of the stage is not too far from crossing the Rubicon, but why wait for a successfully returned stage to do this testing? I think there is more to it than igniting engines a few times. Structural issues from impact of landing, exposure to cold of space and then land back in warm humid ocean, and I assume there is some warming of skmin due to friction during launch and re-entry. Consider this theoretical scenario: First one is fine, but they see damage to the one that landed hard and had 1 leg compress. They will want to draw some line below which damage is not expected and above which special inspections are needed. Drawing that line will require multiple landed stages to get an idea of what sort of landing G force is OK. Test firings don't help. Jesus, are you back on this again? If the compression core doesn't compress, there is no structural damage. If there's no visible fire damage, there is no thermal damage. Lines drawn. Now STFU, you ignorant yammerhead. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn Commercial space launch providers must obtain insurance or self-insure. I am absolutely certain the insurers have some input to this process. |
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SpaceX just did a full duration test firing of a recovered 1st stage
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SpaceX just did a full duration test firing of a recovered 1st stage
Jeff Findley wrote:
In article , says... Rick Jones wrote: Indeed. My point I suppose is similar to your question at the end - why did they take so long to start when they could have started with a non-recovered stage? The only thing that comes to mind, and I suppose it is a non-trivial consideration, is that the recovered stage is comparatively inexpensive compared to a never-flown one. Some customer has already paid for its construction. I thought someone had already offered a pretty reasonable explanation for that. Until you've shown you can recover a high enough percentage of boosters to make reuse worthwhile, why spend the money on the test firing program? That's not exactly cheap, either. I believe that was me. First things first. Gantt charts and whatnot (which my managers usually take care of, since I'm a technical guy). I guess I'm still on a chicken-and-egg circle or perhaps thinking too much about wasting anything but time. Indeed, it isn't worth trying to figure-out how many times you can successfully launch a booster before you know you can reliably land one. At the same time though, there isn't much point to making it possible to land a stage if you cannot reliably launch it a reasonable number of times. Presumably, SpaceX needs (or at least "high wants") both. Starting with sticking the landings seems like a reasonable place to break the circle, but I think we are still left with the conclusion that more than a small handful of static fires of a one-launch stage is basically for show because if there was indeed value to the 4th through Nth static fire of a stage, that value would have been there with a non-flown stage and it would seem that only a question of money would have precluded doing N repeated full static fires on a non-flown stage in parallel with the landing experiments. -- Don't anthropomorphize computers. They hate that. - Anonymous these opinions are mine, all mine; HPE might not want them anyway... feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH... |
#29
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SpaceX just did a full duration test firing of a recovered 1st stage
Rick Jones wrote:
I guess I'm still on a chicken-and-egg circle or perhaps thinking too much about wasting anything but time. Indeed, it isn't worth trying to figure-out how many times you can successfully launch a booster before you know you can reliably land one. At the same time though, there isn't much point to making it possible to land a stage if you cannot reliably launch it a reasonable number of times. Both true and false. If you intend to refly them you have to design them for some minimum number of reflights. You can't add that in later. So you know they're good for at least that many flights. Figuring out how far beyond that you can go can be left until later. -- "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 |
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