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RealScaleBooster Ariane V fix - VEB decouple node #1757
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Theysen
commented
Aug 20, 2017
- VEB currently works as interstage although it is being kept on the ESC-A
- fixed decouple node so the VEB stays attached to the upper stage and provide the fuel and guidance
Thanks for catching that one! I have some more updates to do on the Ariane 5 in the near future, especially for it's intricate double attitude control system and to fix some stupid errors of mine. |
Welp I should actually tell NecroBones about to fix in the core mod but that one single thing isn't worth a whole new release so I thought that we're patching them anyways. Just tell me about it and I can see what I can fix and add. Thanks though :) |
I have made the changes, i'll just upload the changes to GitHub for you to pull and preview once i am sure that everything is OK. Mostly mass distributions (since the adapter is now part of the upper stage) along with some RCS updates for the roll control authority. |
OK, the updates are live: https://github.com/PhineasFreak/RealismOverhaul/commit/d1efa43495a67caa64601b4d81fb59162ea41592 Do note that the RCS combination may seem very weird at first but it is actually a very clever setup: the roll thrusters (Hydrazine) control the vehicle from the moment of the booster separation till the separation of the ESC-A. After that, the SCAR thrusters (GH and GOX) activate and take care of the 3 axis stage + payload attitude control (until payload separation and CCAM). The only "problem" (realism) is that the user may need to manually disable the roll RCS thrusters after ESC-A separation. Nothing will break if they are not disabled though. Do not be alarmed by the lack of RCS plumes for the roll thrusters. For some reason both the "emptyEngine" and "lp_rcs" models (just empty engine and RCS thrust transforms - no actual model attached) do not accept any kind of FX. The thrusters work perfectly (can be also checked via the PAW RCS info). |
Great I'm loading up right now and will check it out. Sad they don't emit a plume but welp, thanks for implementing the complete correct setup of the thrusters and even the stages they start working! |
No problem at all! Do some checks though to validate the changes and ping me back. I may have missed something obvious, as it happens to me all the time... |
Alright, I think I might have goofed my understanding of all this. Due to a bad source what I mistakenly took for the VEB (the interstage) doesn't decouple at the bottom. For the plumes of the RCS thrusters I get a FX for every thruster. Even when disabling the one pair you mentioned before.? |
Well, i was the one that goofed in the first place. I though that the VEB was part of the EPC-E (to provide roll control - the ESC-A provides it's own thrusters for that) and interstage structure... Now: the VEB is mounted on the top of the ESC-A (like the Saturn IU) and the interstage is mounted on the bottom of it and it is a part of it. I got these from the Ariane 5 user's manual (it has a graphic indicating the various parts of the vehicle). Other infographics though (launch video coverage) do not show that. And using some common sense, as you point out, they would not carry the interstage with it (it may also mess with the thermal properties of the HM7 engine - it is semi-radiatively cooled). God, so much confusion! For the RCS FX: it may just be my bad computer that i am currently stuck with... |
Yes the ariane launch manual shows that the ISS (and actually many many pictures) is part of the ESC-A assembly at least and gets attached under the actual stage and manual also refers to "part of ESC-A (which could lead to the assumption that it stays attached). Then there is this: Pyrotechnical expanding tube at the top of the ISS which would actually make it like the Saturn V interstage seperator ring, ha I can't dig up any sources on that specific part but common sense tells me to not carry it with you after sep and ullage. I try to dig up more and deeper! |
That would make even more sense. Sub-assemblies of a stage are usually stacked separately before being integrated together (horizontal or vertical stack integration - the Ariane 5 uses the second one) so being "part of the ESC-A" may mean that it is part of the ESC-A stack (with the EPC-E and the payload adapter + SYLDA + fairing being the rest of them) and not of the stage. The "Pyrotechnical Expanding Tube" seems to be another naming for the pyrotechnical cords used for severing structural connections. So, the separation plane is done between the interstage and the ESC-A...back to the drawing board! Another thing that we should be added (by cloning RSB parts): the ullage motors and the Hydrogen vent valve of the EPC-E (to spin the stage after separation - similar to the Soyuz boosters). Edit: and another addition: the various configs for the EAP boosters (MPS-236, MPS-238, MPS-241/A). |
So the solution would be to give the interstage a double decoupler top and bottom where one decouples from the bottom stage, then the ullage happens and upon good HM-7B ignition the ISS decouples from the top and sets ESC-A free. EDIT: Thinking about a good way to do this. IIRC the Saturn V of his pack has a decoupler module defined to the bottom stage tank, then the actual decoupler piece has its own decoupler set to the top node then to be separated later on. I think this makes most sense in terms of usability and showing the user its actual intention. Unfortunately NecroBones stopped development before he added the ES variant, too. Edit: It seems I got confused with the ES variant of the VEB since ESA itself states that the VEB is mounted between EPC and ES upper in between those two.** |
Does the interstage carry the ullage motors or are they part of the ESC-A? I cannot find any more information about them in the webs. BTW, having a double decoupler in a single part does not allow the user to stage each of them on separate staging events. |
That's why I would put one decoupler onto the top node of the EPC-E part. Ariane Manual states that the ISS has 4 ullage motors (I'd suspect they come from Nammo as the separation motors for the EAP do). Though I'm still not convinced of the double separation, but otoh you wouldn't fit ullage onto the interstage having to accelerate the bottom tank (~12t) as well. I think we have this right with a double seperation I think. |
Oh correct, the EPC-E does not have an integrated engine module! Nice! I could give the motors some generic stats for now until we can find the proper ones. Edit: i could also merge the motors to the interstage and set a "staged" field to them. The decoupler will fire, along with the motors on the same stage. Then, the next staging event will decouple the interstage. |
Whatever you think works better, really! I'd prefer a complete "manual" sequence to get the timings correct (yes, sometimes I take it that seriously..) but that is just me! edit: I also find different masses for the ESC-A stack ranging from 17t to 21t. What did you base the complete masses on? (just making sure since with the current ~20t it's somehow getting difficult to get into GTO). |
Masses are currently wrong but they are based around the 19440 Kg mark (14900 Kg propellants, 165 Kg HM7, ~70 Kg Hydrazine). The inert ESC-A mass should then be 4.3 (and not the stated 4.87). After studying the launch time line i can see that the HM7 ignition comes ~6 seconds after MECO. Maybe the motors aren't "ullage" but "separation" ones? I searched around for launch photos but none of the interstages had any equipment mounted (read: bulges) on them. Other infographics also indicate that the interstage remains on top of the EPC-E (no dual-plane separation). |