RealKerbal3x Posted January 8, 2021 Share Posted January 8, 2021 Nice words from Chris Hadfield: Just now, Spaceception said: So what do you guys make of this? Will SN12-14 be skipped, or are they preparing for a more ambitious test flight ahead of time? I'm thinking that SpaceX didn't expect SN8 to get nearly as far as it did, so they started building a lot of prototypes so they could have several tries at the flight and left the major changes to SN15. But SN8's flight was almost perfect, and the issue that doomed it was easily fixable, so they realised that they could get away with skipping SN12-14 and move directly to higher and faster flights. Maybe SN15 will have a full heat shield and go to orbit, who knows? Quote Link to comment Share on other sites More sharing options...
magnemoe Posted January 8, 2021 Share Posted January 8, 2021 1 hour ago, Delta dart said: I think I have some kind of prediction for Superheavy which is that the whole "catching a booster with the launch arm" idea will be later on in the life of Starship since it seems a bit to overcomplicated for the first 50~ flights or so and I think we may see some sort of landing legs earlier on before transitioning to mid air booster catching. I say +50 flights, a lot depending on how fast they move forward with launches. For one the catch system will be an major construction itself and nothing they will start building before they have two orbital pads or more. Also a bit depending on there they will launch to, building this at the KSC will be hard because of existing infrastructure there and hard to launch while its under construction. Quote Link to comment Share on other sites More sharing options...
Lukaszenko Posted January 8, 2021 Share Posted January 8, 2021 I'm guessing much sooner with the catch system. What's the point of perfecting landing on legs when you can start landing on the catcher? Why not test all the things in parallel, if possible? Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted January 8, 2021 Share Posted January 8, 2021 6 minutes ago, Lukaszenko said: I'm guessing much sooner with the catch system. What's the point of perfecting landing on legs when you can start landing on the catcher? Why not test all the things in parallel, if possible? This. What’s the point of even designing legs that they know will be obsolete? Probably the leg engineer was having trouble coming up with a workable arrangement and did an end run around the problem. Besides, the plan was always to land on the mount anyways. Not to mention that just because we don’t see any sign of a catching support tower at the SH launch mount, doesn’t mean it’s not under construction in the tents and can be cranes into positions in weeks or less. Look at how fast the high bays go up... I wouldn’t be surprised to ultimately see service towers on rails to be rolled to and from the mount, allowing the launch tower to get out of the way of the hazard zone and the landing arms move in.... Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 8, 2021 Share Posted January 8, 2021 Check out the tiling arrangement on this SN15 section. Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted January 8, 2021 Share Posted January 8, 2021 1 minute ago, sevenperforce said: Check out the tiling arrangement on this SN15 section. Also, notice that there seems to be almost a whole set of tile attachment points. Maybe they're going for a full heat shield on SN15? Quote Link to comment Share on other sites More sharing options...
Spaceman.Spiff Posted January 8, 2021 Share Posted January 8, 2021 26 minutes ago, RealKerbal3x said: full heat shield on SN15? It would make sense to try the flip-landing maneuver with full mass on the starship. Or maybe it's going to be the first orbital..... Quote Link to comment Share on other sites More sharing options...
RCgothic Posted January 8, 2021 Share Posted January 8, 2021 (edited) You guys may be a little ahead of me here, but I haven't seen it spelt out explicitly - it's not SN12 in the mid-bay. It's SN15. So looks like they're skipping 12,13,14. Edited January 8, 2021 by RCgothic Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted January 8, 2021 Share Posted January 8, 2021 1 hour ago, RCgothic said: So looks like they're skipping 12,13,14. Does that mean they've 'fixed' something on 15 prior to stacking that was already integral to the earlier iterations? Something they don't want to waste time, energy or money tearing down those to fix it? Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 8, 2021 Share Posted January 8, 2021 9 minutes ago, JoeSchmuckatelli said: 1 hour ago, RCgothic said: So looks like they're skipping 12,13,14. Does that mean they've 'fixed' something on 15 prior to stacking that was already integral to the earlier iterations? Something they don't want to waste time, energy or money tearing down those to fix it? I suspect that 12-14 are going to be partial prototype tests, like SN7. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 8, 2021 Share Posted January 8, 2021 If Elon persists in this hairbrained scheme to catch Superheavy by its grid fins, I have an idea how it could be done. I like the idea of snagging Superheavy's grid fins on wires, but having the wires strung bare between towers doesn't make much sense and doesn't give much control. You aren't able to control different axes of freedom because attempting to "shock absorb" in the vertical axis will allow the booster to swing in the opposite direction. What you want is a system that controls the tilt of the booster and the vertical displacement of the booster separately. Here's what I'm thinking: The "catch" wires for the grid fins are taut across the semicircle arms, so as soon as contact is made (even if it's just one wire) it immediately tugs on the entire arm. Each arm, in turn, rotates on a single axis, held by a crane-like wire set. Finally, each entire arm platform rests on shock absorbers which can only actuate up and down. As the booster descends, the arms lay flat to stay out of the way of the rocket plume. Then, at the correct time, they are rapidly lifted into place to snag the grid fins. (Alternately, they could be folded up and lowered into place to snag the grid fins.) They are more or less locked in place by their crane wires and the entire platform provides vertical shock damping. Finally, once the engines have cut off and the booster has come to rest, the platforms are lowered gently and the arms provide fine control to guide the booster onto the launch clamps. Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted January 8, 2021 Share Posted January 8, 2021 The problem I see with a lot of these 'catch the grid fins' designs is that it requires the spacecraft to land exactly on the x. We need a solution that can catch a craft that lands a bit off center - and I like your cable thinking - but I don't think it's long enough. You need arms that can swing into positions relatively quickly and cables to snap up and take the strain / stabilize the craft - but I don't think you can do it if it's a glorified jack stand and the craft has to thread the needle to get to the pad. Suggested: pairs of arms/towers with cables spaced wide enough from the pad to not interfere with any slightly off descent trajectory. Make them capable of being moved fairly quickly into position and then tighten the cables of each pair to take the strain at the grid fins. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted January 9, 2021 Share Posted January 9, 2021 The grid fins are what, 7 meters long I heard? Nine meter core... All they need is two parallel bars thirteen meters apart, with a small dip in the center. That gives two meters clearance wiggle room on each side and much more on the open sides. I think they have much accuracy already Mounted to an arm/shock absorber assembly similar to an engine lift at a vastly larger scale. Or maybe some other mounting arrangement supporting both ends would be better. Still sounds fairly simple. The more complicated part would be allowing the bars to move closer to each other as needed, if needed, which I suppose would be easier to do supporting both ends of the bars... Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted January 9, 2021 Share Posted January 9, 2021 People are pointing out that the grid fins are designed to take very large aerodynamic loads, which is true. But those are distributed loads, not point loads. Which could be another issue. Quote Link to comment Share on other sites More sharing options...
Spica Posted January 9, 2021 Share Posted January 9, 2021 And not only are the aerodynamic loads distributed in space, they are distributed in time as well. The grid fins may be designed to take large loads, but that does not mean they're designed for impact loads. The closest thing to an impact a grid fin should feel in flight is the unstart that happens around Mach 1, which itself is distributed over the fin. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted January 9, 2021 Share Posted January 9, 2021 (edited) On rails. Massive fins sliding up and down on rails. It can adjust the rocket vertically and let it change its clearance: "land/start" - high, "park" - low. Also it can adjust CoM and CoP to save the fuel in flight. Edited January 9, 2021 by kerbiloid Quote Link to comment Share on other sites More sharing options...
Lukaszenko Posted January 9, 2021 Share Posted January 9, 2021 15 hours ago, mikegarrison said: People are pointing out that the grid fins are designed to take very large aerodynamic loads, which is true. But those are distributed loads, not point loads. Which could be another issue. Could be. But, the very things that allow them to perform their aerodynamic function also helps them perform their new structural function: they are thick and they are large. They are also made of titanium to contend with the heat. Even if I'm completely talking out of my ass, strengthening them up in order to take the loads would surely be less costly mass-wise than adding a bunch of legs. Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted January 9, 2021 Share Posted January 9, 2021 51 minutes ago, Lukaszenko said: They are also made of titanium to contend with the heat. Elon said in his 2019 Starship presentation that the Super Heavy grid fins would be made from stainless steel. It has a lower melting point (1450 C for 304L steel vs 1668 for titanium) but it should do the job. And casting titanium grid fins of the size required would be prohibitively expensive. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted January 9, 2021 Share Posted January 9, 2021 11 hours ago, kerbiloid said: On rails. Massive fins sliding up and down on rails. It can adjust the rocket vertically and let it change its clearance: "land/start" - high, "park" - low. Also it can adjust CoM and CoP to save the fuel in flight. Kind of like this I guess. Elon trolls people who responds with ideas he can use. No this is not engineered in any way at best they done some sort of feasibility study who show its possible. Quote Link to comment Share on other sites More sharing options...
zolotiyeruki Posted January 9, 2021 Share Posted January 9, 2021 Given that SH can hover, how much shock loading would we expect to see on the grid fins? Quote Link to comment Share on other sites More sharing options...
Flying dutchman Posted January 11, 2021 Share Posted January 11, 2021 (edited) Sn9 testing should resume today. Edited January 11, 2021 by Flying dutchman Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted January 11, 2021 Share Posted January 11, 2021 What ever happened with the 1/2 second raptor burn from the other day? Quote Link to comment Share on other sites More sharing options...
tater Posted January 11, 2021 Share Posted January 11, 2021 SN9 closure cancelled today (weather is nasty there, apparently). Also: Quote Link to comment Share on other sites More sharing options...
Flying dutchman Posted January 11, 2021 Share Posted January 11, 2021 Just now, tater said: SN9 closure cancelled today (weather is nasty there, apparently). there is also a power outage. not sure how that affects things.. Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted January 11, 2021 Share Posted January 11, 2021 32 minutes ago, JoeSchmuckatelli said: What ever happened with the 1/2 second raptor burn from the other day? Seemed like it was less than full duration, so they're probably going for a second attempt. However, the road closures for that have been cancelled due to bad weather. Quote Link to comment Share on other sites More sharing options...
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