egg changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Cardano. We currently target 1.2.2. <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/
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<egg>
(if you install it you need to start a new game, principia persists the state)
<maccollo>
ooooh
<egg>
maccollo: btw, can I share that stuff around? it's unlisted for some reason, but it illustrates our flight planning stuff quite well https://www.youtube.com/watch?v=uWTsh1KswDg
<kmath>
YouTube - KSP:Principia L5 rendezvous
<egg>
(except at the end where you start doing the actual rendez-vous of course)
<maccollo>
sure, I just keep it unlisted to avoid cluttering my channel
<maccollo>
it might give people the wrong idea though
<egg>
yeah, with rendez-vous, true
<maccollo>
I mean you don't have to do all that shenanigans to rendevouz
<egg>
maccollo: I'm *trying* to get vessel-centred frames in Cartan :-p
<egg>
that way you can do rendez-vous right :D
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<maccollo>
you would need to compare the angle of the velocity vector at intercept though
<egg>
what do you mean?
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<maccollo>
like if you do a planetary transfer without looking at the sun reference frame you may think you got it right
<maccollo>
but the intercept is a terrible angle
<egg>
maccollo: right, but it's not so much the angle as it is the relative velocity
<egg>
(the angle is the way you see that you'll get a high velocity at intercept)
<maccollo>
yeah
<maccollo>
I guess that may not work out as consistently for ships since their orbits can be much wonkier
<egg>
we'll see how it works in practice tbh
<egg>
but even if we end up having closest-approach markers, stock-style, we'll need the vessel-centred frame to compute them
<egg>
so might as well start with that
<egg>
it should be interesting to dock using those weird frames :D
<maccollo>
usually when I rendevouz I just use ksp's target system, and then make adjustments along the way
<egg>
maccollo: yeah, it will be interesting to see how it works out once you have the new frames :D
<maccollo>
the surface reference frame is amazing
<egg>
maccollo: is it?
<egg>
maccollo: feel free to send screenshots if you're doing cool things, if I know how things get used I can see how to improve them
<egg>
also it's cool to see trajectories :-p
<maccollo>
yes, makes it super easy to target a specific spot on the surface
<maccollo>
especially if you are coming in on a hyperbolic entry trajectory
<egg>
oh right
<egg>
I thought the trajectories mod did that too? never tried it though
<maccollo>
doesn't principia break trajectories?
<egg>
principia models things ballistically without atmosphere though, so might not be that accurate
<teabot>
Accuratea.
<egg>
maccollo: I don't know
<egg>
I've never tried the other one
<egg>
it's quite possible
<egg>
we break things even more now with tilt :D
<maccollo>
even if it works, it will probably use KSP's predicted entry point
<maccollo>
so it will be very wrong
<egg>
yeah
<egg>
true
<egg>
maccollo: if you target a planet you can also use the sun-aligned frame to see whether you'll land on the day side or the night side
<bees>
egg: is it possible to dynamically switch frames based on selected celestial body?
<bees>
or maybe it is already there, i dont know
<egg>
nah, you have to select it in our clumsy UI right now
<GregroxMun>
The ChanServ message still says the current version is Cantor.
<egg>
GregroxMun: argh yeah
<egg>
GregroxMun: say
<egg>
GregroxMun: phl and I were tempted to look at what the TRAPPIST-1 system looks like in principia; there's your thing, but the problem there is that it's Kerbal-scale...
<GregroxMun>
Did you try Sigma Dimensions rescaling it?
<GregroxMun>
What's the problem with Kerbal Scale?
<egg>
well scaling things doesn't preserve their physical properties
<egg>
things aren't linear
<egg>
life is complicated
<GregroxMun>
Wait, so a scaled down version of the solar system would not behave just like the solar system?
<egg>
GregroxMun: unless you scale things in nontrivial proportion, it most certainly won't
<GregroxMun>
well that's not at all what I expected.
<egg>
GregroxMun: example: take rocks proportionate to the sizes of the planets and with their densities
<egg>
and put them at the right distances
<egg>
congratulations, nothing happens
<egg>
GregroxMun: what works is if you resize things as if you were changing the units
<egg>
GregroxMun: in proportion to the exponents of the base units
<egg>
naive scaling changes the physics
<GregroxMun>
I'm really struggling to grasp why this happens.
<egg>
GregroxMun: so, say you scale lengths by some factor λ.
<egg>
so your orbits are half the size
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<egg>
λ = 1/2
<GregroxMun>
right
<GregroxMun>
planetary radii should also be scaled by 1/2.
<egg>
GregroxMun: it's proportional to the radius, at constant density!
<egg>
so it's been halved
<GregroxMun>
But I don't half the surface gravity.
<egg>
(of course it is, because when I sit on a grain of sand the grain doesn't pull 1 gee on me
<egg>
GregroxMun: then you don't divide the mass by 8
<egg>
it means you increase the density
<egg>
by 2
<GregroxMun>
that's correct, I believe.
<egg>
so then if you've doubled the density, that doubles the mass, and halving the radius divides the mass by eight
<egg>
thus the mass is quartered overall
<GregroxMun>
So what's the problem if this happens to everything in the system equally?
<egg>
so let's summarise, for now what we've done is fixed the mass unit (by changing density), and fixed the length unit (by changing the sizes)
<egg>
hmm
<egg>
GregroxMun: maybe that works if you consider solely gravitational effects and you don't do additional silly things? because then you screw arbitrarily with the unity of time to make things right
<egg>
it still feels like I'm missing something though
<GregroxMun>
This should be something that can be figured out from experiment.
<egg>
GregroxMun: waitwaitwaitwait
<egg>
so whatever happens to your orbital periods constrains how you have rescaled time
<GregroxMun>
The orbital periods in a keplerian rescaled system are sqrtλ
<GregroxMun>
same with delta-v
<egg>
so here it's proportional to the square root of a^3/μ, where a gets halved, and μ quartered
<GregroxMun>
SLIPPIST-1 actually crashes with principia.
* bees
stares at integrator step
<bees>
still 45 minutes?
<bees>
still hardcoded?
<egg>
it's never been hardcoded, you can edit the hex in the savefile to change it, it's serialized :-p
<egg>
(ok it's not exactly doable)
<egg>
GregroxMun: ok, so time gets scaled as you say
<egg>
GregroxMun: but now come back to accelerations
<egg>
hmm
<egg>
nevermind
<egg>
yeah, it works
<egg>
scaling time is evil though
<GregroxMun>
I'm testing out SLIPPIST-1 at 10x scale. (using Sigma Dimensions)
<egg>
GregroxMun: scaling time is kind of evil in terms of the perception that you have of it: when you launch your rocket, if it takes 10 s to clear the pad, those look like 10 s
<egg>
GregroxMun: whether kerbals are 1 m or 10 m high isn't really something that you can distinguish in game
<GregroxMun>
Yeah but I already knew that.
<GregroxMun>
It's actually just "scaling the system down is evil"
<egg>
but yeah, as long as it's only gravitation, you're right, it works
<egg>
(bear in mind that atmospheric effects on the other hand are another story entirely)
<egg>
i.e. pressures should get divided by 100 in your system, by those rules :-p
<egg>
wait no, got a sign wrong
<egg>
nah, pressures remain constant, it's the density of air that needs to change
<GregroxMun>
These changes are made purely for gameplay reasons. yes, launching into space is different than real life, but launching from Kerbin is significantly different from launching from Earth.
<egg>
yes, but then I'm interested in looking at the TRAPPIST system, not some rescaling thereof
<egg>
ferram4: I am confusing myself with dimensional analysis >_>
<GregroxMun>
Sigma Dimensions will allow you to rescale the system.
<ferram4>
That doesn't surprise me.
<GregroxMun>
Well it would, except SD won't work on anything alphabetically after "Sigma"
<egg>
...
<bees>
KSP modding at its finest
<egg>
GregroxMun: maybe I'll just yoink your models and make myself some configs >_>
<GregroxMun>
Resize = 10, Rescale = 10, Atmosphere = 1.143, dayLengthMultiplier = 3.16227766, should give you more or less the TRAPPIST-1 system within real world instrumental error bars.
<GregroxMun>
But if you insist...
<bees>
10?
<bees>
not 0.1?
<egg>
bees: GregroxMun made a tiny TRAPPIST
<GregroxMun>
Kerbal scale is 1/10, SLIPPIST is at Kerbal Scale
<egg>
ferram4: also FAR april's fools idea: scale densities up by a factor of 10, and consistently with the other units :-p
<GregroxMun>
Oh wait no definitely don't use my SLIPPIST's orbital numbers. Eccentricity and Inclinations are wrong I think.
<ferram4>
Nah, I don't like April Fool's jokes.
<egg>
ferram4: yeah, iirc stupid_chris's was not well received
<GregroxMun>
what was that joke?
<egg>
ferram4: I feel like for a proper TRAPPIST system you'd need wind modeling
<GregroxMun>
why?
<GregroxMun>
Because eyeball planets?
<GregroxMun>
Huh. Principia also crashes with TRAPPIST-scaled SLIPPIST.
<egg>
*crashes*?
<egg>
or simply apocalypse popup
<GregroxMun>
the game crashes.
<GregroxMun>
I assume it's principia
<GregroxMun>
"KSP has stopped working."
<egg>
if the game crashes you screwed up your config probably, apocalypse should popup
<egg>
what does the FATAL say
<egg>
GregroxMun: ferram4: re. wind, because one side gets heated all the time and the other is permanent darkness
<egg>
if you have an ocean you might get away with just very strong winds, with the ocean doing thermal exchange
<egg>
otherwise, you have supersonic winds in the twilight
<GregroxMun>
Is that a real thing? Supersonic winds for eyeball planets?
<egg>
GregroxMun: principia: loudly pointing out bugs in your configs by crashing your game :-p
<GregroxMun>
Golf should be rotating. I have its config right here, says it's tidallyLocked = true, and it's not at infinite distance. Not even really all that far, period should be on the order of Munths.
<GregroxMun>
(weeks in real time)
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<GregroxMun>
ferram4: I just noticed that FAR's last version was marked as 0.15.something. I'm curious as to why it's not 1.x?
<ferram4>
Because 1.0 is for being complete.
<ferram4>
There are still wing-related aerodynamics that I want to implement.
<ferram4>
At some point.
<ferram4>
When I figure out how to do it.
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<egg>
ferram4: whereas for principia we don't have any hope of completion so it's just the unending parade of dead mathematicians
<egg>
no numbers
<GregroxMun>
the final version number will be Grunmb. He was the first guy to prove that 1+1=2. He did so by bashing the heads of anyone who disagreed with him.
<GregroxMun>
:P
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<egg>
it's alphabetical, and I don't intend to die before the H releases :-p
<GregroxMun>
Would principia have any problem with multiple Kerbin-template planets for some reason?
<egg>
I don't know
<egg>
I have no idea what's up with your system but somehow its angularV for that planet is coming to me as 0
<egg>
try setting the angular velocity explicitly?
<GregroxMun>
is that a Kopernicus feature?
<egg>
everything is a Kopernicus feature
<egg>
Kopernicus is all-powerful
<GregroxMun>
How I wish that were true.
<GregroxMun>
I've swapped Golf's template to Laythe from Kerbin. (It might be worth doing this anyway to get rid of some other minor issues) It works.
<egg>
KSP works in mysterious ways
<egg>
s/works/"works"/
<Qboid>
egg meant to say: KSP "works" in mysterious ways
<egg>
GregroxMun: now warp a bit and see if it brings you an apocalyptic popup
<GregroxMun>
Orbits are rock-solid, I can't tell that they're not conics.
<GregroxMun>
No apocalyptic popup so far after day 400
<bees>
GregroxMun: maybe because principia didnt load?
<GregroxMun>
principia window is up
<egg>
GregroxMun: how long are the orbital periods agairn
* bees
backs to the shadows
<egg>
bees: nah I don't think we'd do that
<GregroxMun>
"plugin is running"
<egg>
bees: we tend to crash when we're not happy
<egg>
or sometimes we crash Unity
<egg>
I had a bug where I segfaulted unity by feeding it nulls
<egg>
GregroxMun: timescale of days for the orbital periods?
<GregroxMun>
orbital periods are (from wikipedia, I'm running 10x realistic scale) 1.5, 2.4, 4.1, 6.1, 9.2,12.4, and 18.76 days
<egg>
you might need a timewarp mod to see any wobbling
<egg>
get bettertimewarp, set timewarp to the fastest preset
<egg>
that should be fun
<GregroxMun>
Strange, in Universe Sandbox their TRAPPIST breaks down immediately.
<egg>
maybe they don't use Jacobi hierarchical elements
<egg>
orbital elements all depend on how you interpret them
<egg>
GregroxMun: did you set the anomalies correctly?
<GregroxMun>
No I did not.
<GregroxMun>
It wasn't listed on Wikipedia.
<egg>
they need to be in the right phases if it's going to be realistic
<GregroxMun>
That's true, I hadn't considered that.
<egg>
GregroxMun: for simplicity put them all at e = 0, i = 0, lan = 0, argpe = 0, and align the anomalies
<egg>
no they aren't angles, but it's easy enough to figure things out from that
* UmbralRaptor
is run over by a rogue planet.
<egg>
ow
<egg>
UmbralRaptor: Nice
<GregroxMun>
Not if your brain is a badly built Jupiter-sized cluster of Babbage Engines that can only calculate things through a particularly daft human emulator.
<egg>
UmbralRaptor: sadly they have 67 iterations of the model to go
<egg>
>_>
<egg>
GregroxMun: the angle between transits is one full turn
<egg>
2π
<egg>
so you can pick a point (say that cute double transit on the 22nd of september) and repeat see where the others are along their orbits
<egg>
(say the two that are double-transiting are at 0 there)
<egg>
GregroxMun: arguably it might be a bit difficult for h, for which you have only one point in this diagram, but for that one you can just use the period listed elsewhere and work things out from there
<egg>
;rpn 4 5.5 / 2 π * *
<kmath>
egg: 4.569589314312426
<egg>
GregroxMun: so for instance if at that double transit f and g are at 0 mean anomaly (setting all lan and argpe at 0), a is at 4.57 rad
<egg>
(measured by ruler-to-the-screen)
<egg>
;rpn 7.5 8.8 / 2 π * *
<kmath>
egg: 5.354987477709874
<egg>
and that's b
<egg>
wait no, not a and b, b and c
* egg
stabs designations with an UmbralRaptor
<GregroxMun>
I want to do math in my spare time less than I want to have accurate anomalies for the system right now.
<egg>
that's not math, that's reading numbers
<GregroxMun>
Well that then
<egg>
it's literally reading numbers, since I'm just computing them for you
<GregroxMun>
I don't want you to do that right now.
<GregroxMun>
wait, yes I do
<GregroxMun>
What am i saying
<egg>
but I just did it so now you just have to type those numbers
<egg>
;rpn 14.7 3.5 - 14.7 / 2 π * *
<kmath>
egg: 4.78718880547016
<egg>
d ^
<GregroxMun>
I apologize for my stupidity in this regard and I thank you.
<egg>
;rpn 22.2 4.7 - 22.2 / 2 π * *
<kmath>
egg: 4.952961390794719
<egg>
e ^
<egg>
GregroxMun: f and g at 0 as mentioned above
<egg>
;rpn 18.764 9.5 - 18.764 / 2 π * *
<kmath>
egg: 3.102079976855238
<egg>
GregroxMun: and h, very roughly eyeballed
<egg>
(it bears repeating that you must set the Ω and ω of all planet orbits to 0 for the above to be correct)
<egg>
?????????????
<egg>
UmbralRaptor: puns
<egg>
GregroxMun: mind you those numbers are obtained with a ruler to the screen, so they have 2 sigfigs and not much more; if more is needed looking up actual transit dates will be needed
<UmbralRaptor>
egg: and now my school's mascot is all loopy,
<egg>
UmbralRaptor: the university of missouri is a bear?
<UmbralRaptor>
Yes (ish)
<UmbralRaptor>
Named Boomer.
<UmbralRaptor>
The school motto is "bear up"
<egg>
UmbralRaptor: ... I am glad that we don't have mascots or mottos
<UmbralRaptor>
(which can conveniently written as ??)
<egg>
......
<UmbralRaptor>
:D
<egg>
UmbralRaptor: Polytechnique in france does have a motto, it's for the country, the sciences, and glory
<egg>
UmbralRaptor: at least it's not a dreadful pun I guess :-p
<egg>
UmbralRaptor: not that they don't make dreadful jokes, e.g. the sword that's called a tangent, or the 3/2 and 5/2
<GregroxMun>
The mascot of my school is either a Titan (mythological) or a Rocketship, depending on whether you mean the Community College or the High School / Early College located within the College.
<UmbralRaptor>
Does it rhyme with libe`rté, égalité, fraternité
<GregroxMun>
(the rocket ship is my fault)
<UmbralRaptor>
???
<egg>
UmbralRaptor: nah, it it doesn't rhyme (pour la patrie, les sciences, et la gloire)
<UmbralRaptor>
ah
<egg>
UmbralRaptor: ethz has no motto, no mascot, no uniform, no weird linguo
<egg>
the swiss are dull sometimes
<egg>
it's good sometimes :-p
<UmbralRaptor>
ETHZ saves the weirdness for the students.
* UmbralRaptor
stares at Zwicky
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<egg>
UmbralRaptor: what's with zwicky?
<egg>
UmbralRaptor: also did we leak kspacademia into here :_p
<GregroxMun>
Holy macguffinite you need a lot of delta-v to move around TRAPPIST-1 system.
<GregroxMun>
T1e moves at 50 km/s. Earth moves 30 km/s.
<egg>
yup
<egg>
it's *speedy*
<egg>
GregroxMun: though how are the relative velocities
<egg>
because that's what matters I think?
<egg>
hmm, thinking about it not really, the potential difference is strong too
<egg>
but yeah, it's speedy
<egg>
you'll want to pack some serious rocket
<UmbralRaptor>
egg: Zwicky was, er, werid.
<UmbralRaptor>
And yes, kspacademia leaks everywhere we talk. >_>
<UmbralRaptor>
He is celebrated for the discovery of neutron stars. He also went on to consider nuclear goblins, which he proposed as "a body of nuclear density ... only stable under sufficient external pressure within a massive and dense star". He considered that goblins could move within a star, and explode violently as they reach less dense regions towards the star's surface, and serve to explain eruptive phen
<UmbralRaptor>
omena, such as flare stars.[25] This idea has never caught on.
<egg>
UmbralRaptor: "He told his assistant to fire a gun out through the telescope slit, in the hope it would help to smooth out the turbulence. " I should try that
<UmbralRaptor>
egg: I think you need a fixed observatory structure?
<egg>
UmbralRaptor: yes somehow shooting out the window towards the neighbouring houses sounds like a bad idea
<egg>
UmbralRaptor: also I don't have a gun
<egg>
UmbralRaptor: also this is switzerland so chances are the gun closest to me might be a neighbour's ordnance assault rifle
<UmbralRaptor>
egg: Oh, good. If it doesn't work you might well be able to try 29 more times!
<UmbralRaptor>
(STANAG magazines are usually 30 rounds, right?)
<egg>
UmbralRaptor: the default isn't STANAG I think, and apparently the default magazine is lightweight 20 rounds (there are also 5 and 30)
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<egg>
"Zwicky also considered the possibility of rearranging the universe to our own liking. In a lecture in 1948[29] he spoke of changing planets, or relocating them within the solar system. In the 1960s he even considered how the whole solar system might be moved like a giant spaceship to travel to other stars. He considered this might be achieved by firing pellets into the Sun to produce asymmetrical fusion explosions, and
<egg>
by this means he thought that the star Alpha Centauri might be reached within 2500 years."
<egg>
UmbralRaptor: ^ still more reasonable than the ignite-the-atmosphere laser sail nonsense?