If these are indeed the new titanium fins, I am surprised they look so similar to the aluminum items.Matthew
Crop of above picture showing fin detail:
Quote from: matthewkantar on 06/25/2017 12:42 amIf these are indeed the new titanium fins, I am surprised they look so similar to the aluminum items.MatthewYou'd need to do a LOT of aerodynamic simulations and a LOT of R&D to change the grid fin shape, so why not make them the same shape as the proven aluminum fins?
Quote from: envy887 on 06/24/2017 11:50 pmCrop of above picture showing fin detail:The fins really don't match, why not put on a white ablative coating to make them look nice and give an extra small bit of protection?
I notice that grid fins have no apparent streamlining for the ascent. I wonder how much drag they create in their stowed position? Obviously it must not be worth putting a ramp on the upper surface of the fin edges to reduce drag or undoubtedly SpaceX would be doing that.
Comparing the Iridium-1 and Iridium-2 fins, the new ones are about 1.2 times larger, giving just over 1.4 times the cross-sectional area when deployed.
Q: Do the larger fins require more hydraulic fluid for the standard recovery profile?Elon's Response: They will, but the hydraulic system is closed loop, so no fluid lost. They do need more power & energy, but rocket has plenty of that.
Just noticed:Gridfin hydraulic fluid is closed-loop now? When did that happen?
Quote from: IanThePineapple on 06/25/2017 12:45 amQuote from: matthewkantar on 06/25/2017 12:42 amIf these are indeed the new titanium fins, I am surprised they look so similar to the aluminum items.MatthewYou'd need to do a LOT of aerodynamic simulations and a LOT of R&D to change the grid fin shape, so why not make them the same shape as the proven aluminum fins?[Putting on Engineer Hat]There's two things wrong with that. First, no you don't "need" a "LOT" of R&D or simulations to change anything about a design. What you do need is sufficient analysis to determine if it's worth making a change and a cost/benefit analysis and then a willingness to do. That's it. There's no set-in-stone rule as to how much of anything any organization needs to change designs or procedures, just institutional rules and traditions, both of which have been shown to be fairly fast and loose in SpaceX's work. The phrase commonly tossed around is "agility." SpaceX is indeed an "agile" organization and makes changes, improvements and modifications of procedures much more quickly than many comparable organizations. What SpaceX as an organization deems sufficient to change something is much less than others. Sometimes agility is great, sometimes not (e.g., AMOS-6). But ONLY SPACEX THEMSELVES can say if something requires "a LOT" of anything to accomplish. Clearly, it wasn't all too much. They've been recovering stages for 19 months or so. Changes have probably been in work since the first or second recovery. The second thing wrong with your statement is referring to"the shape of the proven aluminum fins." The current design has obvious drawbacks - thin cross-sectional webs that are prone to burn-through based on the first photos of recovered stages, for instance. For another, a bunch of probably sub-optimal aerodynamic qualities such as low aspect ratio and poor transonic performance common to grid fin designs. There are ways to change the aerodynamics of the fins without changing their overall shape/size. A few inches here or there, some tweaks to web/box cell arrangement, modifications to leading or trailing edge profile of the main members, changes to the structural materials and surface coatings ... All very significant aerodynamically in certain flight regimes and all very difficult to ascertain in detail from the unclear photo yet shown. Hopefully tomorrow we'll get better views and see if anything besides the obvious change in color is apparent.[/Engineer Hat]
Quote from: OneSpeed on 06/25/2017 04:06 amComparing the Iridium-1 and Iridium-2 fins, the new ones are about 1.2 times larger, giving just over 1.4 times the cross-sectional area when deployed.They're exactly one "row" longer. They even kept the latching point at the same location, they just extended the grid pattern past the latch.
The disturbance on the water surface does not necessarily mean the rocket was on the left. It can also mean is right above, but the exhaust is tilted to the left.I'd love to see the video too...
Yes and I suspect it was correcting for the "gust" in the final moments, tilted to get back on track, maybe overdid the correction and that's why we see the skip along the deck. Maybe too aggressive on the adjustment but hey they did it.Quote from: meekGee on 06/25/2017 07:33 amThe disturbance on the water surface does not necessarily mean the rocket was on the left. It can also mean is right above, but the exhaust is tilted to the left.I'd love to see the video too...
Quote from: old_sellsword on 06/25/2017 04:10 amThey're exactly one "row" longer. They even kept the latching point at the same location, they just extended the grid pattern past the latch.Looks like they have removed the two vertical stiffeners in the middle of the cross-hatch
They're exactly one "row" longer. They even kept the latching point at the same location, they just extended the grid pattern past the latch.
