raptop changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Gateaux. We currently target 1.8.1, 1.9.1, and 1.10.1. <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/ | <egg> calculating the influence of lamont on Pluto is a bit silly… | <egg> also 4e16 m * 2^-52 is uncomfortably large
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<discord-> e​gg. — @WarriorSabe Let α_0 and δ_0 define the pole of the body with respect to your reference axes as in the IAU WGCCRE conventions (and as in the Principia configuration), and let Ω_eq, i_eq, and ω_eq are the orbital elements of some satellite in the* equatorial reference system of that body.
<discord-> e​gg. —
<discord-> e​gg. — Its orbital elements Ω, i, ω in your reference axes are given by the formulæ below (where sgn is the sign function).
<discord-> e​gg. —
<discord-> e​gg. — —
<discord-> e​gg. — * The observant reader will have noted that this is ambiguous; we choose the origin of right ascensions in that body-equatorial reference system so that Q (as defined in figure 1 of the IAU WGCCRE report) lies at a body-equatorial right ascension of 90°. (edited)
<discord-> e​gg. — @WarriorSabe Let α_0 and δ_0 define the pole of the body with respect to your reference axes as in the IAU WGCCRE conventions (and as in the Principia configuration), and let Ω_eq, i_eq, and ω_eq are the orbital elements of some satellite in the* equatorial reference system of that body.
<discord-> e​gg. —
<discord-> e​gg. — Its orbital elements Ω, i, ω in your reference axes are given by the formulæ below (where sgn is the sign function). (edited)
<discord-> e​gg. — —
<discord-> e​gg. — * The observant reader will have noted that this is ambiguous; we choose the origin of right ascensions in that body-equatorial reference system so that Q (as defined in figure 1 of the IAU WGCCRE report) lies at a body-equatorial right ascension of 90°. This is so that ♈︎ for α_0 = 0, δ_0 = 90° (Earth-equatorial elements are ICRS elements).
<discord-> e​gg. — —
<discord-> e​gg. — * The observant reader will have noted that this is ambiguous; we choose the origin of right ascensions in that body-equatorial reference system so that Q (as defined in figure 1 of the IAU WGCCRE report) lies at a body-equatorial right ascension of 90°. This is so that the origin of right ascension is ♈︎ for α_0 = 0, δ_0 = 90° (Earth-equatorial elements are ICRS elements). (edited)
<discord-> e​gg. — —
<discord-> e​gg. — * The observant reader will have noted that this is ambiguous; we choose the origin of right ascensions in that body-equatorial reference system so that Q (as defined in figure 1 of the IAU WGCCRE report) lies at a body-equatorial right ascension of 90°. This is so that the origin of body-equatorial right ascensions is ♈︎, the origin right ascensions of the reference axes, for α_0 = 0, δ_0 = 90
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<discord-> C​alvin_Maclure. — > Your engines have nearly 11 minutes of fuel, that's a fairly long burn.
<discord-> C​alvin_Maclure. — @Butcher you're not looking at the right value. This burn was performed by a solid kick stage. Burn time is something like 20-30 secs??
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<discord-> e​gg. — @Calvin_Maclure not sure why you set your history to 0 but it is not helping when it comes to understanding the context here
<discord-> C​alvin_Maclure. — > @Calvin_Maclure not sure why you set your history to 0 but it is not helping when it comes to understanding the context here
<discord-> C​alvin_Maclure. — @egg Well, simply put, the predicted Pe value vs the actual Pe after the burn were somewhat different. Used a solid kickstage, instant impulse, to make the maneuver node.
<discord-> e​gg. — what value did MJ give?
<discord-> C​alvin_Maclure. — I know Principia isn't completely exact with predicting maneuvers with solids, but wondering if there's something I did wrong
<discord-> e​gg. — for the Δv
<discord-> C​alvin_Maclure. — Oddly enough, VAB value was 810 m/s, but in flight 990 m/s...
<discord-> C​alvin_Maclure. — Also, does having the Pr history set to 0 do anything... undesirable?
<discord-> e​gg. — then maybe MJ’s computation was wrong
<discord-> C​alvin_Maclure. — > then maybe MJ’s computation was wrong
<discord-> C​alvin_Maclure. — @egg this is my guess as well.
<discord-> e​gg. — @Calvin_Maclure having the history set to 0 means you see no history
<discord-> e​gg. — which means that when I look at your screenshot, I have no information about what happened before the present time
<discord-> C​alvin_Maclure. — Right.
<discord-> e​gg. — also, the history is pretty
<discord-> C​alvin_Maclure. — haha... this is true
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<discord-> B​utcher. — I found I had to under rate the dV from my solids a little to get a reasonable approximation of the behaviour.
<discord-> C​alvin_Maclure. — Yeah, this is my take on it too. MJ seems to... be generous
<discord-> [​experimentalshells?]. — maybe mechjeb assumes solids are operating at a constant thrust throughout entire burn?
<discord-> [​experimentalshells?]. — but we know that solid thrust slowly tapers off near burn end as the propellant is depleted
<discord-> [​experimentalshells?]. — but we know that solid thrust is quite variable and tapers off near burn end as the propellant is depleted (edited)
<discord-> S​tonesmile. — The dV should be correct, and instant impulse was used, so the thrust tail shouldn't be the problem
<discord-> B​utcher. — I tend to favour liquid engines, in part because solid kicks are so awkward to use.
<discord-> l​pg. — PVG is completely thrust-curve-unaware, yes
<discord-> l​pg. — but for dv values it shouldn't matter
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<discord-> n​9gaming. — KRASH sims with Principia are kind of a nightmare XD
<discord-> S​tonesmile. — Is this in regards to starting a sim around another body?
<discord-> [​experimentalshells?]. — I'm pretty sure you can start a sim in orbit of another body, yes
<discord-> S​tonesmile. — @n9gaming If so, those issues can be fixed by starting the sim in earth orbit, going into the cheat menu and turning on hack gravity, changing the orbit to the other body, and turning hack gravity off again
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<discord-> S​tonesmile. — @experimentalshells The problem is that the rotation of the target body gets messed up if you start the sim around it with Principia
<discord-> n​9gaming. — Ah thank you I forgot about the cheat menu
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<discord-> n​9gaming. — Other than turning Venus into a white sphere this works much better, cheers!
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<discord-> W​arriorSabe. — @egg idk what mathematica is, but I'm fine with a long equation. Just to clarify, those outputs are in the same system Kopernicus uses?
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<discord-> e​gg. — yes
<discord-> e​gg. — and Mathematica is the software I used to produce those equations, because deriving them by hand, while not intrinsically difficult, would be quite tedious
<discord-> W​arriorSabe. — It sounds interesting; I'm not really aware of any calculators that do much more than calculations
<discord-> e​gg. — well, it is a calculation, and a fairly straightforward one at that (but a symbolic one)
<discord-> e​gg. — (the word you are looking for would be computer algebra system, or CAS)
<discord-> e​gg. — (no relation to close air support)
<discord-> W​arriorSabe. — Yeah, that
* raptop casts "summon TI-89"
<raptop> (I guess sympy also?)
<discord-> e​gg. — or whichever HPs and Casios have CASes
<discord-> e​gg. — or whichever HPs and Casios have CASs (edited)
<discord-> W​arriorSabe. — Well, physical calculators are expensive so don't really include them usually
<raptop> Emulators/ROMS/ sympy, and tungsten-α if you have good internet then
<raptop> s/\/ / /
<raptop> er
<discord-> W​arriorSabe. — Not aware of any of those, except Wolfram which seems to require a subscription or something
<discord-> S​tandecco. — I'm still waiting for someone to create something that is as fast as Desmos but for more complex things
<discord-> S​tandecco. — even just 3d plot; firing up matlab and writing code without the fancy formatting that desmos has is much slower
<discord-> S​tandecco. — I suppose a graphical calculator would do that, but I've never used one and don't want to spend a few hundreds to find out
<discord-> [​experimentalshells?]. — Well I recommend https://asymptote.sourceforge.io/
* raptop slowly backs away from the sourceforge url
<discord-> e​gg. — yeah I don’t really get how those things are still a thing, they are comparable in price to, say, a *Mathematica* license, for a slow device that does really shitty plots and has a fairly basic CAS
<discord-> [​experimentalshells?]. — asymptote really is still compile from text, but it's free and has pretty good functionality
<discord-> [​experimentalshells?]. — matlab is garbage, considering mathematica exists
<discord-> e​gg. — I hear in some cases it is better for numerical analysis
<discord-> e​gg. — though really when I have to think about numerical analysis my tools are a combination of pen & paper and writing the damned thing in C++
<discord-> [​experimentalshells?]. — asymptote is fully integrated with LaTeX though
<discord-> S​tandecco. — I've only used matlab, is mathematica just an equivalent of it?
<discord-> e​gg. — not really
<discord-> W​arriorSabe. — Oh, mathematica costs money too?
<discord-> e​gg. — well, admittedly I’m not entirely sure what matlab is for, aside from examples in numerical analysis textbooks & courses
<discord-> e​gg. — yes, so does matlab
<discord-> W​arriorSabe. — Is there anything like that that *doesn't*?
<discord-> e​gg. — something something free lunch something
<discord-> S​tandecco. — Octave
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<discord-> S​tandecco. — I'm not entirely sure what Mathematica is for, but matlab is quite useful
<discord-> [​experimentalshells?]. — oh yeah, I forgot Octave existed
<discord-> e​gg. — yeah that’s a free matlab analogue aiui
<discord-> W​arriorSabe. — So more like a fancy programming language made specifically for doing math than an actual calculator with a UI?
<discord-> [​experimentalshells?]. — essentially that's what all of them are
<discord-> S​tandecco. — it is an actual calculator
<discord-> S​tandecco. — a calculator is not just a thing that does sums and products
<discord-> W​arriorSabe. — > with a UI
<discord-> S​tandecco. — well essentially it is, but it has more stuff
<discord-> W​arriorSabe. — "calculator with a UI" was the thing I said it didn't sound like it was, not just "calculator"
<discord-> W​arriorSabe. — At that point I feel like I might as well use an actual programming language
<discord-> [​experimentalshells?]. — I think he means like a calculator with buttons to push
<discord-> [​experimentalshells?]. — I think he means like a calculator with buttons to push, pretty similar to a real calculator (edited)
<discord-> e​gg. — > I'm not entirely sure what Mathematica is for
<discord-> e​gg. — @Standecco apparently today, answering confused questions about reference frames
<discord-> e​gg. — @Standecco ended up producing that to check my calculations
<discord-> S​tandecco. — does it have real time plots?
<discord-> W​arriorSabe. — What advantage does it have over just programming the equation in an actual general-purpose programming language? I'm assuming it has more useful prepackaged operations or something?
<discord-> e​gg. — @Standecco yeah, the sliders mess with the plot her
<discord-> e​gg. — @Standecco yeah, the sliders mess with the plot here (edited)
<discord-> W​arriorSabe. — What advantage does it (the free one) have over just programming the equation in an actual general-purpose programming language? I'm assuming it has more useful prepackaged operations or something? (edited)
<discord-> e​gg. — not sure what you mean by "programming the equation"
<discord-> S​tandecco. — easier syntax, a lot of prepackaged functions and packages, built in plotting
<discord-> e​gg. — the main thing I was doing here was trying to figure out what the equation was
<discord-> W​arriorSabe. — So it does have some level of UI?
<discord-> W​arriorSabe. — Octave that is
<discord-> e​gg. — eventually you will have to use a programming language
<discord-> S​tandecco. — well, probably not what you're thinking of
<discord-> S​tandecco. — but it has a UI
<discord-> S​tandecco. — but it has a GUI (edited)
<discord-> W​arriorSabe. — I mean in the sense that I wouldn't have to program in a renderer
<discord-> e​gg. — a renderer ? ? ?
<discord-> W​arriorSabe. — I have no experience with these kinds of things, and it sounded at first like just a language
<discord-> S​tandecco. — there is more in mathematics than algebraic equations
<discord-> S​tandecco. — and plots for them
<discord-> e​gg. — well yes all those things are programming languages, but they have built-ins for doing maths, plotting, a CAS, etc.
<discord-> e​gg. — My fancy interactive plot is just the output of that (there are a few dozen more lines)
<discord-> W​arriorSabe. — So it's like a more traditional calculator, you just have to program in the input?
<discord-> S​tandecco. — saying that these softwares are calculators is like saying that computers are calculators; it's true, but not in the sense that you'd call them a basic calculator
<discord-> e​gg. — I have no idea what your question means. What do you refer to as a traditional calculator? How do you expect to produce things without somehow specifying inputs, and how do you expect to perform a wide variety of tasks without that specification effectively being a programming language?
<discord-> e​gg. — anyway if you want to get an idea for the look and feel of those things, look up screenshots maybe
<discord-> e​gg. — https://www.wolfram.com/mathematica/ has some screenshots at the top
<discord-> W​arriorSabe. — Well, it's not too important
<discord-> W​arriorSabe. — If the only way I can find to phrase my questions is confusing I can just leave it and look into it some other time
<discord-> S​tandecco. — > how do you expect to perform a wide variety of tasks without that specification effectively being a programming language?
<discord-> S​tandecco. — this is mostly it; the need to use a programming language is evident for everything that is more complex than looking at the graph of a function or perhaps solving a system of equations
<discord-> W​arriorSabe. — Yeah, I gathered that there was one involved
<discord-> e​gg. — to be honest even a physical programmable calculator with buttons is a programming language
<discord-> W​arriorSabe. — It was more a question of how it's used
<discord-> e​gg. — just every one wherein builtin function is expressed by the press of a button
<discord-> W​arriorSabe. — But that's not too important to figure out right now
<discord-> S​tandecco. — turing complete calculators
<discord-> e​gg. — @WarriorSabe if your question is about interactivity, it varies widely
<discord-> W​arriorSabe. — I was talking specifically about the free one
<discord-> [​experimentalshells?]. — octave?
<discord-> W​arriorSabe. — Because I'm not going to spend a bunch of money on a calculator
<discord-> W​arriorSabe. — Yeah, that
<discord-> S​tandecco. — I mean, this is how it looks
<discord-> S​tandecco. — should give you an idea on how you use it
<discord-> W​arriorSabe. — Alright
<discord-> S​tandecco. — which is mostly by googling functions
<discord-> e​gg. — @Standecco Mathematica notebooks are really nice in being interactive, you type a bit of code and run that, then do some more things having seen what came out of that, etc., which is really nice to tinker with symbolic stuff (or, as I was doing today, visualizing/double-checking the 3d vector constructions you are doing)
<discord-> e​gg. — I think there is some python-based thing that has notebooks too, raptop may know more
<discord-> e​gg. — jupyter
<raptop> Yep, jupyter
<discord-> e​gg. — (the downside of notebooks is that you can easily end up with results that you no longer know how to compute because your results came out of evaluating your notebook out of order, or even evaluating some things that you since deleted :-p)
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<raptop> aaaaaa
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<discord-> S​tandecco. — uh, might look into jupyter
<discord-> e​gg. — btw if you are at a university you may want to check if they happen to have mathematica student licenses
<discord-> e​gg. — they had those at ETHZ
<raptop> [terms and conditions apply]
<raptop> jupyter is neat, though AFAIK notably slower than running the sneks directly. (This may or may not matter depending on what you're doing)
<discord-> S​tandecco. — I'll take a look, but I don't really need them for the moment
<discord-> S​tandecco. — I mostly wanted a way to thinker with multivariable functions for calculus
<raptop> On a related note, all hail matplotlib
<discord-> W​arriorSabe. — Alright, I plugged those equations you gave me into desmos
<discord-> W​arriorSabe. — The argument of periapsis seems to be getting shifted backwards by a right angle for an input orbit right on the equator; is that supposed to happen or should I make sure I didn't make a typo there? The other two elements seem fine.
<discord-> S​tandecco. — what I hate of these tools is having to define intervals every time; I just want to look at the graph, I don't need excessively fancy things, and I wish there was a "simpler" plot function that automatically defines ranges and automatically scales things up or down
<discord-> W​arriorSabe. — And if it's an expected outcome of the equation, is it the desired outcome or should I add a right angle back in after the fact?
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<discord-> b​adgermasher. — all hail matplotlib indeed
<discord-> W​arriorSabe. — I have a feeling its what the equation is supposed to be doing since that's how Principia's axis is rotated compared to Kopernicus's, but the input orbit axis is also from a Kopernicus config (tilting a moon system with the planet), so I'll add 90 to the input
<discord-> W​arriorSabe. — I have a feeling its what the equation is supposed to be doing since that's how Principia's axis is rotated compared to Kopernicus's, but the input orbit axis is also from a Kopernicus config (tilting a moon system with the planet), so I'll add 90 degrees to the input (edited)
<discord-> e​gg. — @WarriorSabe if you don’t understand what is going on, randomly adding right angles here and there is unlikely to help. What are you observing, with which values of α and δ
<discord-> W​arriorSabe. — Any pole, but I was using the simplified case of an equatorial orbit
<discord-> W​arriorSabe. — I'm pretty sure it's due to the 90 degree misalignment of Principia and Kopernicus's reference axes mentioned earlier
<discord-> W​arriorSabe. — Any pole, but I was using the simplified case of an equatorial orbit (non-equatorial orbits did care about the pole, and weren't exactly a right angle off anymore) (edited)
<discord-> e​gg. — the formulae I gave you will give different outputs depending on the choice of α and δ. Please do not try to come up with explanations and tell me what you are doing.
<discord-> W​arriorSabe. — I am taking Kopernicus configs for my moons, and modifying them to match the tilt their parent planets now have
<discord-> W​arriorSabe. — Adding 90 degrees to their argument of periapsis before plugging the elements in seems to be giving expected results
<discord-> e​gg. — @WarriorSabe you are going to have to stop expecting things without explaining what they are, this is getting irritating and almost certainly wrong.
<discord-> W​arriorSabe. — wdym
<discord-> W​arriorSabe. — I just explained what it was
<discord-> e​gg. — I mean that there is no such thing as the Kopernicus reference axes.
<discord-> W​arriorSabe. — I thought you said there was?
<discord-> W​arriorSabe. — And I don't know what you're asking me if I'm not answering your questions
<discord-> W​arriorSabe. — Not trying to be irritating or nonexplanatory, I just apparently don't know what I'm supposed to say
<discord-> e​gg. — You are not answering questions about what you are doing and seeing, you are attempting to explain why you are seeing things
<discord-> W​arriorSabe. — I just told you what I was doing and seeing
<discord-> e​gg. — give me numbers.
<discord-> e​gg. — What are the Ω, i, ω you give to Kopernicus absent principia. What are α and δ.
* raptop keeps on interpreting α and δ as RA and Dec
<discord-> e​gg. — raptop, they are, they are the right ascension and declination of the pole
<raptop> ah
<discord-> e​gg. — (also the bridge garbled your UTF-8 on the way here, it is horribly buggy)