Come on, lets get back on topic. ICBMs have nothing to do with it. Quote2. How much propellant (RP-1 & LOX) did they have to unload?LOX and helium is vented. The amount of RP-1 they had to unload is unknown, I don't think it would be much though (the legs cannot take a very heavy landing, and there is no need for a big reserve).
2. How much propellant (RP-1 & LOX) did they have to unload?
Quote from: Dante80 on 01/05/2016 12:32 amCome on, lets get back on topic. ICBMs have nothing to do with it. Quote2. How much propellant (RP-1 & LOX) did they have to unload?LOX and helium is vented. The amount of RP-1 they had to unload is unknown, I don't think it would be much though (the legs cannot take a very heavy landing, and there is no need for a big reserve).IIRC, the environmental impact statement for LZ-1 stated a relatively small quantity of RP-1 expected to remain after landing, something like 150 gallons, though it's hard to imagine cutting it that close.
But still, there is a limit to what the legs can handle. My assumption is that on a high-margin flight like ORBCOMM, the landing burn might be a longer one at lower thrust, to use up the propellant quicker, and that for a low margin flight the final landing burn will be shorter but at a higher thrust level.
Quote from: Lars-J on 01/05/2016 01:05 amBut still, there is a limit to what the legs can handle. My assumption is that on a high-margin flight like ORBCOMM, the landing burn might be a longer one at lower thrust, to use up the propellant quicker, and that for a low margin flight the final landing burn will be shorter but at a higher thrust level.The margin for the mission is in the second stage. The first stage is going to burn the same total amount of propellant between launch and boost back, which should leave the same fixed amount for landing. Additionally, the payload mass really doesn't affect the first stage flight profile that much, it should be fairly the same for every mission.
A new pic. Pretty cool scene I might say.
The upper nozzle blanket definitely appears to have been eroded and likely needs to be replaced. That area is right next to a turbine exhaust outlet.
Here's an enhanced image of the engine closeup. The upper nozzle blanket definitely appears to have been eroded and likely needs to be replaced. That area is right next to a turbine exhaust outlet. The white stuff in the nozzles appears to be some liquid that has dried, perhaps some leaking TEA-TEB fluid, or an additive in the RP-1. There are also many small white marks on the outside of the engine bells. Not sure if that indicates stuff that has flecked on, or scratches made by some external abrasive material.
I agree the whiter areas inside two engines opposite one another hint that those engines were the ones restarted. I assume the center engine has similar white area, but the "clocking" makes it less visible.Something like ignition fluid sure makes sense, but I'm not sure: is there a way we can prune from the causal tree the possibility that these white areas are associated with second/third/fourth engine shutdown transients?
Quote from: Steven Pietrobon on 01/05/2016 04:55 amThe upper nozzle blanket definitely appears to have been eroded and likely needs to be replaced. That area is right next to a turbine exhaust outlet.My impression was that the insulation was like a blanket, and that it didn't erode but retracted "up" into the body (or likely pushed by aerodynamic forces), thus pulling away from the lower area of the engine it should have been covering.Would be interesting to know if it is allowed to move like that.
I'm wondering whether this engine photo, which has annotation saying that it is for thermal testing -https://www.instagram.com/p/6gYIwJl8ZH/- could be to do with reflying sooty engines? The returned stage is pretty mucked up, it'd make sense they'd want to find out a bit about what that'd do to the engines.
There are also many small white marks on the outside of the engine bells. Not sure if that indicates stuff that has flecked on, or scratches made by some external abrasive material.
Quote from: WBY1984 on 01/05/2016 07:13 amI'm wondering whether this engine photo, which has annotation saying that it is for thermal testing -https://www.instagram.com/p/6gYIwJl8ZH/- could be to do with reflying sooty engines? The returned stage is pretty mucked up, it'd make sense they'd want to find out a bit about what that'd do to the engines.At the time this was explained as needing to have a constant thermal emissivity so that IR imaging could obtain correct temperatures for every surface point. Otherwise you have to calibrate for the emissivity of every different surface separately.I don't think it's related to soot.
Quote from: Comga on 01/04/2016 08:13 pmCross posting from Updates thread, (because discussion is not updates.....)Quote from: Johnnyhinbos on 01/04/2016 07:35 pmQuote from: Dante80 on 01/04/2016 06:42 pmhttp://forum.nasaspaceflight.com/index.php?topic=38148.msg1469736#msg1469736 This is a great pic! I am fascinated by the stuff revealed with the raceway cover removed. It's possible it's just the exposure of the photo, but it seems pretty sooty under that cover, which is surprising.If by "raceway cover" you mean the cowlings over the tops of the grid fin pivots, there were no cowlings on the OG2 flight.No, that's not the raceway. The "raceway" is the external piping that runs the length of the stage, highlighted in green in image #1, and you can see the whole length of it from the bottom to the top in image #2.
Cross posting from Updates thread, (because discussion is not updates.....)Quote from: Johnnyhinbos on 01/04/2016 07:35 pmQuote from: Dante80 on 01/04/2016 06:42 pmhttp://forum.nasaspaceflight.com/index.php?topic=38148.msg1469736#msg1469736 This is a great pic! I am fascinated by the stuff revealed with the raceway cover removed. It's possible it's just the exposure of the photo, but it seems pretty sooty under that cover, which is surprising.If by "raceway cover" you mean the cowlings over the tops of the grid fin pivots, there were no cowlings on the OG2 flight.
Quote from: Dante80 on 01/04/2016 06:42 pmhttp://forum.nasaspaceflight.com/index.php?topic=38148.msg1469736#msg1469736 This is a great pic! I am fascinated by the stuff revealed with the raceway cover removed. It's possible it's just the exposure of the photo, but it seems pretty sooty under that cover, which is surprising.
http://forum.nasaspaceflight.com/index.php?topic=38148.msg1469736#msg1469736