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<lamont> awang: actually affects how often PEG runs, its not just UX, its about the cycle time of active guidance
<lamont> awang: does RO model non-instant engine shutdown?
<Bornholio> its more like MJ works best if it can throttle down at the end. Not that it can't handle instant off
<Bornholio> new airplane module lamont?
<lamont> airplane model?
<Qboid> [e6abb] title: Add an AirplaneAutopilotModule... by zyayoung | Additions: 436 | Deletions: 4 | https://github.com/lamont-granquist/MechJeb2/commit/e6abb63c41dd01e8adba2042371043d33cfe3b73
<lamont> that’s from upstream dev
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<awang> lamont: Ah, didn't know that. How much of a difference would reducing the PEG update time make?
<awang> And looks like RO may or may not model engine response time
<awang> Some engines have @useEngineResponseTime = True, some have = False
<awang> The particular one I'm using (X-405) has = False, but that doesn't actually show up in the MM cache, probably because the key didn't exist in the first place
<awang> I could have sworn that I've seen apoapsis/periapsis change for a little bit after the throttle indicator went to zero though, so idk what KSP does by default if useEngineResponseTime isn't present
<awang> Also, MM question
<awang> Does @MODULE[ModuleEngines*] only affect the first ModulesEngines* it comes across?
<xShadowx> awang: i think that key existed for forever, but if it isnt in MM cache it doesnt mean a lot, things in files are just "override the games default coded value"
<awang> Oh
<awang> Do you happen to know what the default value is?
<awang> Guessing false?
<xShadowx> example is lights using "ElectricCharge" resource by default, nobody really cares to change it so MM cache wont show it, but it can be changed :)
<xShadowx> and ya pretty sure false il go look quick
<xShadowx> yep false
<xShadowx> i changed all of my "ElectricCharge" using stuff to "Power" lol works 90% of time til you run into a mod who hardcodes :(
<awang> Ah, I see
<awang> Need to find a different explanation for the orbital changes I'm seeing after engine cutoff then
<awang> "power"?
<xShadowx> i dunno looked prettier ;p
<awang> Also, what's the point of setting ModuleEngines* stuff in RO configs if it gets overridden by ModuleEngineConfigs later?
<awang> It just makes editing configs for two different parts which are supposed to represent the same engine really really really confusing
<awang> Because they aren't consistent in the files
<awang> But ModuleEngineConfigs makes them consistent in-game
<awang> Well, partialy consistent, I think
<awang> Still some things are inconsistent
<xShadowx> that bit you gotta bug someone else sorry :|
<awang> No problem
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<wb99999999> heyllo friends
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<wb99999999> how is Merlin's size compared to RS-27 or H-1?
<Bornholio> merlin d is a 1/2 ton rs-27 is about 1ton
<Bornholio> think H-1 is about 1 ton also
<wb99999999> oh I was thinking about dimensions actually
<wb99999999> should've used better wording
<Bornholio> about the same for all three
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<wb99999999> so...F9 booster is actually more powerful than Saturn IB S1 then?
<wb99999999> only if I can squash the stage into a fatter shape and put S-IV on top of it
<Bornholio> lol yes, nice things you get with 9.7MPa chamber pressure
<wb99999999> well in RO it only took me 7 merlin 1Ds to lift an augmented S-IV with payload
<wb99999999> since it's T/W is way higher
<wb99999999> about double
<wb99999999> man why would you get that red-hot shock heating effect going only M3 at 30K?
<wb99999999> SR-71s don't glow red flying right?
<lamont> awang: at 8g’s an 0.02s physics tick gives a minimum resolution of 1.568 m/s
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<soundnfury> wb99999999: yeah, my rule of thumb is that F9S1 == 1x F-1.
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<Bornholio> 40 Merlin 1D+MT eninges... actually probably less since ISP is enough higher to drop fuel mass significantly
<soundnfury> Bornholio: what's that, S-IC equivalent? And how many would you need if the upper stages were M1D+Vac rather than J-2? ;)
<Bornholio> not sure, I've not gone to that extreme. Problem with a fast guess is that the ISP of the J-2 is much greater so you probably loose all advantage. Now J-2X! good stuff
<soundnfury> that was my point
<soundnfury> if you want a kerolox upper stage then your first stage has to be gruntier
<soundnfury> even taking into account that Saturn hydrolox tankage was heavy AF
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<Bornholio> I want to see a real upgrade to Pheobus II after they finish that new NASA contract for low enrichment NTR .sigh
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<ProjectThoth> Kerelox is kinda a meh upper in most situations... excluding probably the NK-43.
<soundnfury> ProjectThoth: depends what you're doing
<soundnfury> for heavy load to LEO, kerolox is great (yay density)
<ProjectThoth> soundnfury: High-energy, specifically.
<soundnfury> whereas for lighter loads to higher energies, hydrogen Isp starts to shine
<ProjectThoth> Yeah, I could see all-kero being most useful for LEO.
<ProjectThoth> Maybe with some kind of transfer stage hanging out up there for GEO+?
<soundnfury> of course, if you _really_ only want to go to LEO, you use peroxide ;)
<ProjectThoth> soundnfury: This is true!
<awang> soundnfury: Why peroxide?
<awang> lamont: That's a good point
<awang> Also, all: should science cores have ModuleScienceContainer?
<Bornholio> data storage was pretty hard in the early days, probably all the later ones yes
<awang> Oh, that's a good point
<awang> Hmmm
<Bornholio> far side of the moon was first imaged on recovered spy camera film the US lost over USSR, trimmed to fit Soviet cameras. Can't imagine argueing for data storage in that era
<awang> "later ones" isn't going to be fun to do in MM. Don't want to have to hardcode things...
<Bornholio> I add an expensive MJ ar case that does the job if i want to add it
<awang> Doesn't stock now have a science container thing?
<awang> Does that have a RO/RP-0 config?
<soundnfury> awang: glorious bulk density
<soundnfury> non-cryogenic
<soundnfury> (so no boil-off)
<awang> soundnfury: bulk density?
<awang> Like dv per unit mass?
<soundnfury> can decompose it monoprop-style to run the turbopumps, too
<soundnfury> awang: bulk density is just O:F-averaged densities
<soundnfury> there's also density impulse, which is Isp * density (so, thrust / volume flow)
<awang> Is that why black arrow was so light?
<awang> (relatively speaking)
<soundnfury> yeah
<awang> I see
<soundnfury> peroxide systems have some of the lowest tank masses around
<awang> So why does no one use keroxide these days?
<soundnfury> _and_, pumps pump volume, not mass, so denser propellant == smaller, lighter engines
<soundnfury> awang: because the Americans are scared of it
<awang> wat
<soundnfury> (at least, the NASA-ish ones. Some of the newspace guys in the 90s were very much in favour of it, but none of them flew)
<soundnfury> Basically, the Yanks had some bad experiences in the early days with peroxide exploding things (probably because their peroxide was full of impurities)
<soundnfury> and, as so often with heritage rocket technology, if it works once use it forever and never try anything else, if it blows up once it gets a bad name and never try it again
<awang> Ah
<awang> Makes sense
<awang> Risk aversion strikes again
<awang> Guess I need to remember to use the Gamma engines more frequently then
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<soundnfury> awang: fun fact: rocket engine power per mass (== TWR * Isp) is roughly constant within a technology generation http://yarchive.net/space/rocket/fuels/hydrogen.html
<soundnfury> (btw, I've never really used Gamma in RP-0, because they don't have an upward development path)
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<awang> soundnfury: That's quite an interesting read
<awang> I've been using Gamma quite a bit, but that's more because I haven't unlocked anything beyond the first orbial rocketry node
<awang> Been spending all my science on avionics/comms
<awang> So it's been between the X-405 and Gamma 2 for upper stages
<soundnfury> I quickly find myself _really_ wanting restartable upper stages ;)
<awang> Have to agree with you there
<soundnfury> my current game has had a _lot_ of Thor-Agena
<awang> Hmmm
<awang> I'll have to look into those
<awang> My more interesting rockets so far have been RD-107 first stage and either X-405 or Gamma 2 second stage
<awang> AJ-10 for TLI
<awang> Haven't gotten anything else yet
<soundnfury> I haven't used the X-405 since before the Vega config was added
<awang> I haven't unlocked the Vega config, so the stage I'm using should be the same
<awang> Vega config looks really nice though
<soundnfury> mainly because I learned how to make orbit on A-9 or Redstone engines
<awang> RD-103s for me
<awang> The Russians really knew how to make engines :P
<ProjectThoth> Peroxide's not too bad, I've finally been convinced.
<awang> Too bad there's basically two engines that use it
<awang> Does HTP have the same advantages when used for RCS?
<awang> NTO has higher ISP, but figure there's got to be a reason to pick the other options
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<soundnfury> awang: NTO is a toxic biprop
<ProjectThoth> ARCA was supposed to develop a peroxide aerospike, but now that their CEO's in the slammer...
<soundnfury> you should really compare HTP to hydrazine, which arrives at a similar techlevel (actually I think HTP comes first)
<soundnfury> HTP is denser than hydrazine but lower Isp
<soundnfury> and, again, hydrazine is toxic.
<soundnfury> If the Shuttle used HTP-based OMS it wouldn't cost _quite_ as much to refurbish ;)
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<awang> soundnfury: HTP does come first
<awang> As of now it's helium, nitrogen, NTO, and HTP
<ProjectThoth> HTP decays slowly, iirc, which is why it was abandoned for long-duration missions.
<awang> And since when was NTO on its own a biprop?
<awang> Does RP-0 have a penalty for using toxic propellants?
<awang> Some tag or another?
<awang> lamont: Is the mchenry2 tag good to use?
<lamont> yeah
<lamont> node executor is still hosed, but i’m working on that right now
<awang> Alright
<awang> Anything I should be paying attention to in particular that could indicate a bug?
<soundnfury> awang: ohhh you mean N₂O
<soundnfury> NTO is something else (N₂O₄)
<awang> soundnfury: Uh
<awang> RF UI says NTO
<soundnfury> and yeah, HTP is _significantly_ denser than N₂O
<soundnfury> awang: I thought it said NitrousOxide?
<awang> ....I think you're right
<soundnfury> (NTO is short for [di]Nitrogen Tetroxide)
<awang> idk why I thought it said NTO
<awang> I should find a way to show density-related info in the RF UI
<awang> Even better, I need to find a way to get MJ and/or RCS build aid to show stats for RF RCS
<awang> Hmmm
<awang> So the main reason to pick HTP is much smaller tankage volume?
<awang> What was the stat for delta-v density or something?
<awang> Ignition! mentioned something like that when talking about mercury-powered rockets
<soundnfury> awang: "density impulse"
<awang> Ah, yes, that's it
<soundnfury> oh and NitrousOxide is about the _least_ toxic thing there is (apart from Nitrogen I suppose)
<awang> Laughing gas!
<awang> kerosene + HTP would have high density impulse, hydrolox would have low density impulse, right?
<soundnfury> yeah
<soundnfury> but the gap is narrower than between their densities
<awang> So when do I want to optimize for density?
<awang> aka when does hydrolox become preferable?
<awang> ...I guess the answer would be figuring out payload fraction?
<awang> Or something along those lines
<soundnfury> I think it's more a "how much stage delta-V do you need?"
<awang> Oh wait
<soundnfury> also "how sensitive are you to TWR"
<awang> I'm getting into the realm of that Excel spreadsheet for stage optimization, aren't I
<awang> Oh right
<awang> Forgot about that
<soundnfury> note that, for instance, a hydrolox SSTO needs about 600m/s more than one with dense propellants, even assuming the _exact same_ lift-off TWR
<awang> Regularly have burnout TWRs of 8-12 here
<awang> Also, why are solid rocket motors so insanely expensive
<soundnfury> I thought in RP-1 they weren't any more?
<soundnfury> (sure you're comparing SRM to liquid engine plus tanks, rather than just to engine?)
<soundnfury> I've found that Castor Is are now cheap enough to use
<soundnfury> (though I don't use them much because without them my Thor-alike is slap bang on 60t and my not-an-Atlas-but-uses-its-engines gets pretty close to 150)