Total Members Voted: 571
Voting closed: 04/21/2020 12:43 am
Quote from: Spock1108 on 04/26/2020 07:52 amIs it plausible that they are spraying antifreeze to avoid ice formation during cryo tests?Doubt it, it's not gonna stick on the surface for too long, especially once they start cryo testing. Water's going to condense on the surface. If it doesn't freeze, it's going to bead up and run off, taking the anti freeze with it. After a short time, ice is going to form anyways in that case.In very cold conditions, when they spray anti freeze on airplanes, the plane needs to take off quickly after application because it's gonna freeze up if they wait too long without reapplying it.
Is it plausible that they are spraying antifreeze to avoid ice formation during cryo tests?
Quote from: Slothman on 04/26/2020 09:54 amQuote from: DusanC on 04/26/2020 09:31 amQuote from: Keldor on 04/26/2020 09:07 amQuote from: DreamyPickle on 04/26/2020 07:35 amHaving a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)Mathematically you're correct.But engineers like to cheat 1 type of tile in 2 forms, whole and cut in half.PS: I'd like to emphasize that only 200deg of SS needs to be tiled.Does that work the same on a stronger curvature near the tip of the nose cone or will the vertical distance between the rows of half tiles be lower than 1 row?Limits of this "cheat" are defined by:1. Size of tile2. Allowed variation of gap between tiles.So smaller tiles with larger gap can cover stronger curvature (smaller radius)I'd need those 2 dimensions to say what's that radius but I presume with this cheat more than 95% of surface can be tiled, even more if we introduce cutting of tiles with waterjet to different widths to cover corner cases. To solve the problem of stronger curvatures I would introduce 2nd tile of the same type but smaller so that 3 small tiles can be placed on side of 1 larger tilePS. Correction, 3 tiles on side.PPS. Added sketch
Quote from: DusanC on 04/26/2020 09:31 amQuote from: Keldor on 04/26/2020 09:07 amQuote from: DreamyPickle on 04/26/2020 07:35 amHaving a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)Mathematically you're correct.But engineers like to cheat 1 type of tile in 2 forms, whole and cut in half.PS: I'd like to emphasize that only 200deg of SS needs to be tiled.Does that work the same on a stronger curvature near the tip of the nose cone or will the vertical distance between the rows of half tiles be lower than 1 row?
Quote from: Keldor on 04/26/2020 09:07 amQuote from: DreamyPickle on 04/26/2020 07:35 amHaving a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)Mathematically you're correct.But engineers like to cheat 1 type of tile in 2 forms, whole and cut in half.PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
Quote from: DreamyPickle on 04/26/2020 07:35 amHaving a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
Or even a separate thread for heat shield tiling. Mods?
Pretty sure all that spraying last night was likely something simple as soap for a leak check. Not sure if they would do this as part of the room temperature N2 test anyway, or they detected a pressure drop and then decided to do the test. Thing is, a very small leak on such a large vessel would be hard to detect by measurement in a short time, so I wouldn’t be surprised if this would be a standard procedure going forward with any new tank.
Quote from: Spock1108 on 04/26/2020 07:52 amIs it plausible that they are spraying antifreeze to avoid ice formation during cryo tests?More likely a soap solution looking for bubbles. I would assume they depressurized to a safe level first. It does not look to me to be a concentrated spray at high pressure.
What does “ambient pressure test” mean?
I expect the GN2 was fairly cold when they pumped it in. I saw the top and bottom frost over fairly quickly and all over (not bottom up). Then the frosting starting going away and the vending shortly after (if memory serves correctly).Would it be correct to guess that raising the cold GN2 to ambient would induce a nice even pressure gradient suitable for finding small leaks?What do they use for leak detection? I note the spraying but they moved so fast and at large quantity that I'm thinking that was really a hydrophobic coating more than a soap bubble test. Yes? No?
Most likely they were spraying soapy water rather than some sort of coating or antifreeze.
Quote from: awests on 04/26/2020 05:47 pmMost likely they were spraying soapy water rather than some sort of coating or antifreeze.Ok, but why spray water and soap AFTER the pressure test?
Quote from: GregTheGrumpy on 04/26/2020 05:23 pmI expect the GN2 was fairly cold when they pumped it in. I saw the top and bottom frost over fairly quickly and all over (not bottom up). Then the frosting starting going away and the vending shortly after (if memory serves correctly).Would it be correct to guess that raising the cold GN2 to ambient would induce a nice even pressure gradient suitable for finding small leaks?What do they use for leak detection? I note the spraying but they moved so fast and at large quantity that I'm thinking that was really a hydrophobic coating more than a soap bubble test. Yes? No?I would assume the GN2 is sourced from the big LN2 tank on the farm, either they pull from the headspace of the tank or they run the LN2 through an expansion. In either case, the GN2 will probably go through a heat exchanger to bring the GN2 up to "ambient" temperature. I do not remember SN4 tanks frosting over until after venting. The only sign of the GN2 test was smoothing of the dents, as pointed out by someone on the LabPadre stream.Most likely they were spraying soapy water rather than some sort of coating or antifreeze.
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