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starship? but ........ROTFL ! :-)
SpaceX's new Starship prototype appeared to burst during a pressure test late Friday (Feb. 28), rupturing under the glare of flood lights and mist at the company's south Texas facility. The Starship SN1 prototype, which SpaceX moved to a launchpad near its Boca Chica, Texas, assembly site earlier this week, blew apart during a liquid nitrogen pressure test according to a video captured by SPadre.com. A separate video posted by NASASpaceflight.com member BocaChicaGal clearly shows the Starship SN1's midsection buckle during the test, then shoot upward before crashing back to the ground. Space.com has reached out to SpaceX for details of Friday's test. This story will be updated as more information is available. https://www.space.com/spacex-starshi...e=notification www.asps.it/patportions.htm |
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starship? but ........ROTFL ! :-)
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starship? but ........ROTFL ! :-)
On 2020-03-02 12:10 AM, JF Mezei wrote:
Watching the BocaChicaGal video. The flaw happens on the left of rocket and then spreads till rocket starts to lift off. The first evidence I see of an anomaly is on the right side as I see it. However, as it lifts off, the body cavitates onto itself. Assuming the bottom weld unzipped itself, allowing the nitrogen to push down and lift the rocket, what principles are involved in the nitregen wanting to go down so much it created a vaccum above it which caused tank/rocket to cavitate onto itself? The nitrogen under pressure has found an outlet and expands outwards creating a partial vacuum at the top of the tank where it is still sealed. I am presuming that a RUD was unplanned for in this case because a pressure relief valve was not opened that could have equalized pressure in the tank to outside pressure. I can understand the principle of a bottle made of paper which when you flip to let the liquid escape would cause paper wlls to cavitate instead of letting as much liquid out as air bubbles can get in t o maintain 1ATm inside. Is this a case where the steel walls are designed solely for positive pressure and have 0 capability of negative pressure? Would all rockets be designed with similar behaviour? Or can withstand only so much negative pressure before collapsing. I know Elon was planning on design changes to make the tank more of a structural member of the rocket to improve efficiency. Normally I believe a purge gas is introduced into the tank to compensate for loss of propellant. I presume for Starlink that will be nitrogen. Probably not set up that way for this test, which wasn't supposed to unravel presumably. I can't speak for all rockets, but due to a discussion I had back on the arocket mailing list some time ago I know the bi-propellant tanks of the first stage of the Titan II ICBM had to be fueled in order to maintain structural integrity of the rocket before the second stage was fueled and to maintain it afterwards once the rocket was stacked in the silo. This discussion came about because I had a question about the Damascus AK incident and how that happened. https://en.wikipedia.org/wiki/1980_D...sile_explosion One of the reasons the Air Force got rid of silo based liquid fueled rockets. I assume they are all designed to maintain at least the same pressure inside as there is outside at all times to prevent cavitation? Or would most rockets have enough strength to support a fair emount of negative pressure to maintain structural integrity? I believe the Starship is intended to use a purge gas to maintain tank integrity. I'm assuming that is nitrogen. I don't know that as a fact. Secondly, considering the rocket didn't get shot up high, and cavicvation happened early, would it be fair to state that the pressure wasn't very high in the tank at time of failure? Seems like a pretty good lift to me given that nitrogen is largely inert and did not "ignite". I would not make that assumption. Aftermath video the next morning: https://youtu.be/U4C0wfRSUNQ Dave |
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starship? but ........ROTFL ! :-)
On 2020-03-02 9:15, David Spain wrote:
On 2020-03-02 12:10 AM, JF Mezei wrote: [snip] I assume they are all designed to maintain at least the same pressure inside as there is outside at all times to prevent cavitation? Or would most rockets have enough strength to support a fair emount of negative pressure to maintain structural integrity? I believe the Starship is intended to use a purge gas to maintain tank integrity. I'm assuming that is nitrogen. I don't know that as a fact. AIUI the Starship (and probably also the SH booster) are designed to use "autogenous pressurisation", that is, returning a fraction of the gasified propellants back from the engine pumps to the tanks to maintain pressure in the tanks. Discussions on nasaspaceflight.com speculate that the recently destroyed Starship SN1 was intended to go on to test autogenous pressuration, and that this explains why it had engine mounts for only one Raptor engine although one engine would not be enough for a significant test flight and a static-firing test with only one engine would be unrealistic. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ . |
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starship? but ........ROTFL ! :-)
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starship? but ........ROTFL ! :-)
In article ,
says... Watching the BocaChicaGal video. https://youtu.be/sYeVnGL7fgw Going frame by frame (pause, and use the "," and "." to step back or forward respectively frame by frame). The flaw happens on the left of rocket and then spreads till rocket starts to lift off. However, as it lifts off, the body cavitates onto itself. Assuming the bottom weld unzipped itself, allowing the nitrogen to push down and lift the rocket, what principles are involved in the nitregen wanting to go down so much it created a vaccum above it which caused tank/rocket to cavitate onto itself? It's *liquid* nitrogen. A huge leak at the bottom of a closed liquid tank creates a vacuum inside the top of the tank. This is *exactly* how a mercury (or water) barometer works. A launch vehicle tank isn't designed to handle any external pressure (why would it be?), so it literally buckles and crushes when it encounters an external pressure greater than the internal pressure. 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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starship? but ........ROTFL ! :-)
In article , says...
I assume they are all designed to maintain at least the same pressure inside as there is outside at all times to prevent cavitation? Or would most rockets have enough strength to support a fair emount of negative pressure to maintain structural integrity? I believe the Starship is intended to use a purge gas to maintain tank integrity. I'm assuming that is nitrogen. I don't know that as a fact. Actually it will pressurize the liquid methane tank with gaseous methane and the LOX tank with gaseous oxygen. The hot gases will come from the Raptor engines. Note that the space shuttle's external tank was pressurized in much the same way (the SSME's were designed to send hot gases back to the ET for pressurization). This saves mass since you don't need separate pressurant tanks (typically helium, which is lighter than nitrogen). 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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starship? but ........ROTFL ! :-)
Il giorno martedì 3 marzo 2020 00:14:16 UTC+1, JF Mezei ha scritto:
On 2020-03-02 12:29, wrote: I think Musk is crazy because: 1) is trying to do something better than Saturn 5 2) Saturn 5 was scrapped about 50 years ago by NASA Technology has advanced a bit since the 1960s. What is being "displayed in public" at BocaChica doesn't represent the real developmenht in my opinion. Consider that the Raptor engines are being developped in a serious and private environment and are being tested with no hystericals. The glorified beer kegs build publicly at Boca Chica gives SpaceX wants to test very inexpensively some construction techniques with steel that it has no experience with. So the failure of "SN1" teach SpaceX more about how to weld steel. Maybe they will find a way to do steel, maybe they will conslude it can't be done and switch back to more modern materials. Note that when working with composites, small flaws in laying up the fibre that leave air bubbles can be "fatal" to the structure. So I suspect that SpaceX is at the same stage with learning to do flawless welds. If you have seen close up pictures, you will see welds havce a lot of arrows and markings along the welds. Good luck to Mr. Musk and his starships. We asps go in the PNN path quo fata ferunt E.Laureti |
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starship? but ........ROTFL ! :-)
On 2020-03-02 6:14 PM, JF Mezei wrote:
Consider that the Raptor engines are being developped in a serious and private environment and are being tested with no hystericals. I suspect that isn't really correct. I'd have to double check but AFAIK there isn't tons of security around the McGregor test site. I've seen plenty of test stand photos taken there. Esp. back in the Grasshopper days of Falcon 9. There isn't much hysteria because, well frankly the Raptor has been pretty much thoroughly tested these days. That isn't the same as saying there won't be Raptor failures in the future, but it isn't exactly new tech for SpaceX either. The glorified beer kegs build publicly at Boca Chica gives SpaceX wants to test very inexpensively some construction techniques with steel that it has no experience with. So the failure of "SN1" teach SpaceX more about how to weld steel. Maybe they will find a way to do steel, maybe they will conslude it can't be done and switch back to more modern materials. Way too soon to think that. Note that when working with composites, small flaws in laying up the fibre that leave air bubbles can be "fatal" to the structure. So I suspect that SpaceX is at the same stage with learning to do flawless welds. If you have seen close up pictures, you will see welds havce a lot of arrows and markings along the welds. I think you are confusing failure with progress and are too skeptical. With each "failure" you learn an incredible amount of information that can be put to practical use almost immediately. Instead of crying "fail!" after each RUD I say "progress!". Wasn't it Edison who said something to the effect that they'd learned first about 10,000 ways NOT to build a light bulb? Dave |
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