Hannu2 Posted June 16, 2020 Share Posted June 16, 2020 16 hours ago, mikegarrison said: With actual water tanks, and a lot of other pressure vessels, it's pretty standard to use a criterion known as "leak before burst". I wonder if SpaceX explicitly considered that? (Of course, they may have, and this was just an unexpected failure mode.) Is there really significant difference with rocket fuel tanks? It is certainly beneficial in this kind of tests, but if a big hole appears during launch pad operations violent fire which bursts the whole rocket may be hard to avoid. And during ascent such a leak means certainly mission failure and immediate RUD. Maybe they can get some tenths of seconds for aborting capsule but not much more. Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted June 16, 2020 Share Posted June 16, 2020 16 minutes ago, Hannu2 said: Is there really significant difference with rocket fuel tanks? It is certainly beneficial in this kind of tests, but if a big hole appears during launch pad operations violent fire which bursts the whole rocket may be hard to avoid. And during ascent such a leak means certainly mission failure and immediate RUD. Maybe they can get some tenths of seconds for aborting capsule but not much more. It's a good question. Obviously leaking rocket propellants is dangerous. But leak before burst is not primarily about tolerating leaking. It's about failure happening on a controlled scale that maybe gives you a chance of catching and fixing it. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted June 16, 2020 Share Posted June 16, 2020 1 hour ago, Hannu2 said: SpaceX's PR is based on publicity. I am sure that other companies make tests too, and fail sometimes, but behind fences without cameras. SpaceX's development pace is also probably more than all other combined in the world. Their advances in last decade are exceptional. They began from nothing and have taken largest share of world's satellite launches, their reusable rocket is overwhelmingly more advanced and economical than any other manufacturer's products and next they will begin crew transports for NASA. If they get Starship operational for heavy satellite launches in next few years they even increase their distance to others. I hope that Blue Origin can challenge them very soon, because monopoly situation is never good in long run. I do not believe that traditional big companies in USA or Europe can do it without massive political subsidizing. They has always tested a lot, two static fires for all engines before launch, one on test stand in Texas and the shorter pad static fire. But I think learning how to land first stages affected starship. As the stage was lost anyway, the only extra cost was the recovery systems so they was free to experiment. Think Elon love the idea and this was probably the main driver from carbon to steel once he got that steel was competitive. And they might play a bit too fast, they lost one starship because pressurization issues who all rockets has, and the last because the quick release who also all rockets with cryogenic fuel have. Blowing up tanks on the other hand is training, Quote Link to comment Share on other sites More sharing options...
tater Posted June 16, 2020 Share Posted June 16, 2020 Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted June 16, 2020 Share Posted June 16, 2020 5 hours ago, Hannu2 said: SpaceX's development pace is also probably more than all other combined in the world. SpaceX is doing some good things. But I think you are a little overenthusiastic about this part. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 16, 2020 Share Posted June 16, 2020 Jokes: Quote Link to comment Share on other sites More sharing options...
magnemoe Posted June 16, 2020 Share Posted June 16, 2020 2 hours ago, Hannu2 said: Is there really significant difference with rocket fuel tanks? It is certainly beneficial in this kind of tests, but if a big hole appears during launch pad operations violent fire which bursts the whole rocket may be hard to avoid. And during ascent such a leak means certainly mission failure and immediate RUD. Maybe they can get some tenths of seconds for aborting capsule but not much more. However on an fueled rocket (probably exceptions like the Soyuz and small rockets like electron) loosing pressure on any first stage tank or lower upper stage one will give you an fireball. No its not balloon tanks but they are need to be pressurized to hold the fuel and oxidizer above. Also leaks in themselves are very bad, in short its an benefit as it give the abort system more time to trigger. Its an RUD anyway. On starship, well with no escape system you might have time for very short prayer. Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted June 16, 2020 Share Posted June 16, 2020 54 minutes ago, RCgothic said: Jokes: I sawed this starship in half! Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted June 16, 2020 Share Posted June 16, 2020 Apparently they do, indeed... need a bigger boat... Spoiler Quote Link to comment Share on other sites More sharing options...
tater Posted June 16, 2020 Share Posted June 16, 2020 Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted June 16, 2020 Share Posted June 16, 2020 4 hours ago, Hannu2 said: Is there really significant difference with rocket fuel tanks? It is certainly beneficial in this kind of tests, but if a big hole appears during launch pad operations violent fire which bursts the whole rocket may be hard to avoid. And during ascent such a leak means certainly mission failure and immediate RUD. Maybe they can get some tenths of seconds for aborting capsule but not much more. There's actually a huge difference. A leak in a metal tank results either from weld bead displacement or from plastic deformation. Note that I'm not talking about polymer plastics here, but rather the permanent deformation of a solid material when its yield strength is exceeded. A rupture, on the other hand, is different. It can be initiated by plastic deformation or the loss of weld material, but the big "boom" takes place when a fracture propagates within the crystalline structure of the metal, pouring the pressurant energy directly into the metal matrix. If your tank won't leak before it ruptures, then its failure characteristics are nonlinear. You can pressure-test, but you cannot be sure that your pressure test didn't introduce small cracks that weakened the vessel. You also won't be able to know whether the tank will still hold pressure under transient loads. On the other hand, if you can design a tank that leaks before it ruptures, then you know EXACTLY how much pressure the tank can take. You can determine the level of plastic deformation that will result from a particular pressure load. You can calculate how the tank will perform under transient loads. You can pressure-test to a specific safety factor without increasing the risk of subsequent rupture. Both are equally bad when they happen on a rocket, but leak-before-burst is vastly better for being able to figure out what your rocket is capable of. Quote Link to comment Share on other sites More sharing options...
Hannu2 Posted June 16, 2020 Share Posted June 16, 2020 2 hours ago, mikegarrison said: SpaceX is doing some good things. But I think you are a little overenthusiastic about this part. It is very possible. SpaceX's publicity makes fair estimation difficult compared to companies which makes development hidden. It is difficult to know for example how Blue Origin proceeds, probably they announce ready New Glenn few months before launch. And of course traditional operators have economically huge programs too, but they have too many rent seekers and results are very small compared to costs. 38 minutes ago, sevenperforce said: There's actually a huge difference. OK, thanks for the information. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted June 16, 2020 Share Posted June 16, 2020 1 hour ago, tater said: Hyper loop is stupid, they’ll go with boats. Quote Link to comment Share on other sites More sharing options...
cubinator Posted June 16, 2020 Share Posted June 16, 2020 24 minutes ago, sh1pman said: Hyper loop is stupid, they’ll go with boats. But you could have an underwater high-speed train that is as expensive to install as the entire rocket you're riding it to! Quote Link to comment Share on other sites More sharing options...
sh1pman Posted June 16, 2020 Share Posted June 16, 2020 2 minutes ago, cubinator said: But you could have an underwater high-speed train that is as expensive to install as the entire rocket you're riding it to! No idea how expensive it is to install, but the whole idea is silly, I can’t see it being used anywhere. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 16, 2020 Share Posted June 16, 2020 37 minutes ago, sh1pman said: Hyper loop is stupid, they’ll go with boats. Tesla boats! Quote Link to comment Share on other sites More sharing options...
tater Posted June 16, 2020 Share Posted June 16, 2020 Quote Link to comment Share on other sites More sharing options...
sh1pman Posted June 16, 2020 Share Posted June 16, 2020 Just now, StrandedonEarth said: Tesla boats! No, SpaceX boats. Methalox supercavitating torpedo-boats! Still 100x more plausible than hyperloop. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted June 16, 2020 Share Posted June 16, 2020 26 minutes ago, sh1pman said: No idea how expensive it is to install, but the whole idea is silly, I can’t see it being used anywhere. This application is taylor-made for it, really. Boats need (LOTS of) maintenance, are subject to weather troubles, expensive to fuel/crew/operate, etc. High-speed tunnel transport seems much better here, all else being equal, and fear easier to justify than intercity. IIRC it's under budget, too. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted June 16, 2020 Share Posted June 16, 2020 Just now, CatastrophicFailure said: This application is taylor-made for it, really. Boats need (LOTS of) maintenance, are subject to weather troubles, expensive to fuel/crew/operate, etc. High-speed tunnel transport seems much better here, all else being equal, and fear easier to justify than intercity. IIRC it's under budget, too. Hyperloop is not just a high speed tunnel. It’s a high speed vacuum tunnel. Which is insane for several reasons, not the least of which is safety. Quote Link to comment Share on other sites More sharing options...
tater Posted June 16, 2020 Share Posted June 16, 2020 No need for a tunnel (or tube) to be "hyperloop." That requires evacuating the tube, right? 1 minute ago, sh1pman said: Hyperloop is not just a high speed tunnel. It’s a high speed vacuum tunnel. Which is insane for several reasons, not the least of which is safety. Beat me to it. Yeah, tunnels make sense, even high speed ones. Hyperloop? Meh. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 16, 2020 Share Posted June 16, 2020 And in the meantime, there’s electric floatplanes Quote Link to comment Share on other sites More sharing options...
Flavio hc16 Posted June 16, 2020 Share Posted June 16, 2020 There is a place where Hyperloop make sense: Mars, as an intermediate way of transport between colonies (100yeras from now) Quote Link to comment Share on other sites More sharing options...
zolotiyeruki Posted June 17, 2020 Share Posted June 17, 2020 On Mars, you probably don't need to worry about creating a vacuum in it, either. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 17, 2020 Share Posted June 17, 2020 (edited) On 6/14/2020 at 11:50 AM, StrandedonEarth said: Knowing SpaceX it'll be something like this.... Called it! Same brand as the pic I posted too! Same day these robo-pooches went on sale too: https://www.cnn.com/2020/06/16/tech/boston-dynamics-robot-dog-spot-sale/index.html Get yours now for only $74,500! Also: Edited June 17, 2020 by StrandedonEarth Quote Link to comment Share on other sites More sharing options...
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