Bornholio

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About Bornholio

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    Sr. Spacecraft Engineer

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  1. Realism Overhaul Discussion Thread

    I think you are missing two things, RL-10B is 3x expansion and less than half the chamber pressure so thats more than 6 x pressure that instability will happen at. Yes the RL-10 is very much a vacuum only engine 280:1 At/Ae Ratio 462ISP 4412kPa https://www.google.com/search?q=4412+kpa+atm https://www.google.com/search?q=4412+kpa+psia J-2X runs fine at Sea level 92:1 At/Ae Ratio 448ISP 9515kPa http://www.rocket.com/j-2x-engine IIRC its about 650kN on the stand or 228ISP. As a sustainer it could be ground lit and throttled to minimum until Just after Max Q then ramped until separation of boosters of whatever form you use. Regardless it was designed to be lit 4 times so its best role is final ascent, circularize, Injection burn and correction burn or Lunar Circ (with lots of MLI layer for tanks) for a large payload. Personally I prefer the J-2S Ascent to parking orbit and low TWR High ISP Injection stage. Oh and nukes, luv me some nukes. Feel free to look up the curve or calculate the Pc/Pe Ratio using the chart below that is good for the range of fuel mixtures the J-2X is likely to use. chamber pressure 1280psia (https://www.google.com/search?q=1%2C380+psia+kpa&ie=utf-8&oe=utf-8) = 4412 or ~93Atm See MIT's lecture on modeling nozzles MIT16_50S12_lec7.pdf as a good reference. Next Note that expansion nozzles seem to be pretty easy changes in the scheme of things and are modified to match expected mission regime. J-2X at the time was being developed as a low cost alternative to the SSME RS-25 with a High Altitude optimized nozzle. Its much greater chamber pressure due to RS-25 derived turbo machinery allows it to operate at a higher range of pressures than a similar low pressure chamber and also reduces the size of High nozzle ratio impact. Otherwise as stated above stick with a higher TWR J-2S or even J-2, or if you need a lower altitude an RS-25 Is expensive but appropriate.
  2. Realism Overhaul Discussion Thread

    @Mike`Searching the NTRS server for data! Sorry for the salt but learning how to use the Nasa Technical Report Server is awesome. Way One : Google [ site:ntrs.nasa.gov rl10b sea level isp ] Way Two: from https://ntrs.nasa.gov/ [ rl10b sea level isp ] The RL10B2 isn't a ground level engine, and real losses would greatly affect its thrust and ability to run. comparing its 15km altitude or higher ISP curve would make some sense since it is a vacuum optimized engine. Calculation curves don't have flow instability included, also watch out for numbers that are "Ideal" instead of validated numbers. Calculated ISP for a higher Ae/At ratio nozzle will show the higher values even though they are in a critically expanded region. This is a real number, it is just not useful. For KSP it is useful in that it is used for the curve versus pressure. Understand that fuel flow method can make a huge difference in ISP and ability to perform at various altitudes. The J-2X is optimized for low to high altitude operation and high thrust to weight. Strapping large SRB's and using it as a sustainer is a good role. Yes you will need to modify some part to use the resource also. The best way is using a Module Manager .cfg but you can copy or edit an existing tank. See how real fuels does it for the best way. You could also just modify real fuels .cfgs if your already using that (my assumption given we are in RO land).
  3. Realism Overhaul Discussion Thread

    Using CRP as an example make a small .cfg file adding the resource and then either modify or make new a consumer for the resource. You can make it all in one file if you want. Suggest that you separate it a custom mod folder so you can easily extricate it it you don't want to use it or it breaks things. Alternately squad/resources/ResourcesGeneric.cfg can be added to. Example see https://wiki.kerbalspaceprogram.com/wiki/CFG_File_Documentation#RESOURCE EvilAI.cfg RESOURCE_DEFINITION { name = SelfReplicatingBooleanCode displayName = SRBC Units density = 0.1 flowMode = ALL_VESSEL transfer = PUMP isTweakable = true isVisible = true unitCost = 0.5000000 color = .25,.25,1 volume = 1 } Then pick a useful module to consume or modify it in another part https://wiki.kerbalspaceprogram.com/wiki/Module.
  4. Realism Overhaul Discussion Thread

    Yes and No, the module space name must not (name=), but description names may (displayName=). If you want much more detail on CRP Roverdude and crew over in CRP land have better detail and look like they have done a huge amount of work localizing lately.
  5. Realism Overhaul Discussion Thread

    Generally they are not guesses, they are available estimates from some reliable source. Commonly this is NTRS data such as https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100034922.pdf Worrying about sea level thrust on these engines is not too much of an issue. They don't have the thrust to be useful as first stages and most of the time a modern first stage is putting them in a safe and well known altitude. Nothing in KSP handles thrust instability and flow separation so its up to the designer not to pick wrong engines. NASA and others have investigated widened range solutions via aerospikes (Annular and Linear). Even the J-2 has seen both forms for test stand runs (J-2T and XRS-2200) but commonly the solution is upping the chamber pressure.
  6. Realism Overhaul Discussion Thread

    Any electric drive will tax your patience considering that they generally need many hours of burn to be useful https://github.com/KSP-RO/RealismOverhaul/wiki/Ion-Engines. The BNTR (peewee class 500MW) and NERVA II (Phoebus class 5000MW)are useful at the 6-12km/s fuel load range, any less likely use a 455-465ISP Hydrolox. I put set of engines based on real NTR's in RO that are ground tested that have Methane configs in addition to Hydrogen https://github.com/KSP-RO/RealismOverhaul/commit/3d726589e207285825c36cd022716f71dc86960a. If Methane config nukes are an option ( only the soviet RD-0410 was ever tested) they will out perform Hydrolox in the 3-5km/s range and then Hydrogen Nukes will outperform Methane in the 7-10km/s range. https://github.com/KSP-RO/RealismOverhaul/wiki/Engine-Usage-and-Stage-Sizing If you are using Nertea's Future Prop one option if you have patience is using the Plasma RCS single thrusters as a cluster main drive, the ISP is above Nukes but relatively low allowing them to have reasonable TWR thus giving burn times that might only be an hour long for capture burns and other big dV changes. A nuke powered VASIMR is doable but generally outperformed by NTR unless you need 20km/s dV or more and then you will be doing overnight or worse burns at x4 physical timewarp. If you are looking for an advanced realistic option the highest performance up to the 20km/s range is the SNTP (a 1000MW reactor) they have a design TWR in the mid teens and an ISP of 940. With only 5 ignitions they are very optimal for a planetary injection/correction/capture. For any high ISP option Hydrogen/Cryo boiloff is the main problem so you need a solution to that for keeping any cryo fuels.
  7. [1.2.2] Realism Overhaul v11.5.1 - 06/12/2017

    Yes, lowering gimbal is usually a good thing, also I find control surfaces can be lowered a lot of authority. This is a real world problem also One place I notice it a lot is with a-9 engines, the twr is generally high because the burn time is not long enough to increase the fuel fraction any higher and the craft will do a pitch buck if gimbals and CA is not turned down. Verniers can help or hurt. If the Control loop in KSP could be tuned we could solve the problem relative to FAR and other RO changes. @Wallygator Put a github issue up for it and describe it carefully, give any supporting information and if you want add any changes you made as examples.
  8. [1.2.2] Realism Overhaul v11.5.1 - 06/12/2017

    Any time I can't find something a Github repository search helps figure it out. https://github.com/KSP-RO/RealismOverhaul/search?utf8=✓&q=aestus&type= https://github.com/KSP-RO/RealismOverhaul/blob/bf4413550e1a873f094d862d72feb2150c64c3e1/GameData/RealismOverhaul/Engine_Configs/Aestus_Config.cfg https://github.com/KSP-RO/RP-0/search?utf8=✓&q=aestus&type= Do you have the NONONRP0 folder? that can make it not show up, in dev RP-0 its assigned to '92 rocketry.
  9. What did you do in KSP today?

    Spent the day working on Getting RO running on 1.3.1 Updated the RO Golden 1.3/1.3.1 spreadsheet Guessing that RO/RP-0 will go straight to 1.3.1 now. Play some not RO first, launched Sub-Orbital tourists a bunch of times with this 8+Jeb Tourister, landing gear crushed, so they got replaced by structural. Everything recovered including the boosters. Radar Mapping Kerbin Same Radar Mapper on the way to Mun and Minmus
  10. [1.2.2] Realism Overhaul v11.5.1 - 06/12/2017

    Lots of additions to the spreadsheet and added a column for 1.3.1 availability. KSP RO Debugging (AKA: The Golden Spreadsheet) Mk1.3 &Mk1.3.1 Added links to awangs testing .dlls have started testing RSS and then RO in 1.3.1. Moar links and additions, feel free to update as it is open edit.
  11. What did you do in KSP today?

    A long lapse of play thanks to being very busy. Did a re-useable dual stage comnet to mars ship after reading a little spacex stuff Heavy SRB first stage. Landing legs and aero to bring it down on a boat. First Stage testing, battery died before legs deployed, Petal Adapter is supposed to be a large air brake once slowed down, still barely got it recovered intact. Lots of drop tanks, all disposable, jettisoned in sets of 4. Second stage d-orbits and lands upside down. Transit bus is a Methane nuke (SNTP-Full Flow Expander version) since 5 ignitions is perfect for the transit as the sat needs to enter a good orbit at mars. It does about 7k dV on Tanks shown. Parking Orbit at mars, xenon drive on sat has 15k dV for a long life orbiting mars
  12. Who is the most significant person on the forum to you?

    Mr. @NathanKell he's so dreamy. I'm getting twitchy without having his twitch lately.
  13. Thanks icedown
  14. [1.2.2] Realism Overhaul v11.5.1 - 06/12/2017

    For those requesting 1.3 update, it is work but some have it running. I'll ask awang to post his .dll's for critical things. KSP RO Debugging (AKA: The Golden Spreadsheet) Mk1.3 Or you can go look at the PR's in critical mods for submitted .dll's. as an example https://github.com/KSP-RO/RealismOverhaul/pull/1775
  15. here are the builds https://ksp.sarbian.com/jenkins/job/MechJeb2-Dev/ Read the PR listings https://github.com/MuMech/MechJeb2/pulls?utf8=✓&q=is%3Apr to see what is changing Each build will list the Version level it is on 2.6.0 for KSP1.2.2 and 2.6.1 for KSP1.3.0. Need to have due diligence and read commits to understand each builds changes. But usually latest is fine, just expect the occasional bug introduction.