UmbralRaptop changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Fano. We currently target 1.3.1, 1.4.x, 1.5.1, and 1.6.1. <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…
<UmbralRaptop>
I don't understand the illumination of observed area part, but otherwise yes.
<egg>
what's unclear?
<egg>
a graph would probably help admittedly
<UmbralRaptop>
yeah
<UmbralRaptop>
Hrm, so consistently viewing the planet under mid morning or afternoon conditions
<egg>
half of it really
<UmbralRaptop>
(or appropriate night times depending on mission?)
<UmbralRaptop>
On a semirelated note, GPM and TRMM's sensors confuse me
kiwi_76 has joined #principia
<egg>
in what way?
<egg>
TRMM is another one of those satellites for which the French wikipedia article is way more detailed than the English one
<egg|cell|egg>
Gregrox: that way I don't need to understand it :-p
<discord->
Gregrox. — egg, how would principia deal with a black hole? >:D
<discord->
Gregrox. — i imagine at a certain point vessels couldn't be integrated and either things would crash or apocalypse
<egg|cell|egg>
We don't have GR so there just is no such thing
<discord->
Gregrox. — I knew you'd say that
<discord->
Gregrox. — but GR isn't necessary to get something which has the same mass and radius as a black hole
<egg|cell|egg>
But then it doesn't meaningfully behave like one; you just get Kepler orbits
<discord->
Gregrox. — sure
<discord->
Gregrox. — but I'd expect you would not even get that
<discord->
Gregrox. — because the system would fail
<discord->
Gregrox. — when you get close enough for that to matter
<discord->
Gregrox. — @egg or egg|cell|egg let me know if you find any other systems that might be fun in principia at rss scale, by the way.
<UmbralRaptop>
Obviously we need a Schwarzschild add-on for Principia
<UmbralRaptop>
(But note that one of the tests in Principia is that it gets Mercury's orbit wrong)
egg|cell|egg has quit [Ping timeout: 183 seconds]
egg|cell|egg has joined #principia
<discord->
egg. — @Gregrox > because the system would fail
<discord->
egg. — that's not intrinsic to the system, rather it's what happens if you use the wrong numerical settings for the system; if you use appropriate settings, it will get more costly as you come closer to the very dense body, but it's still just Kepler.
oeuf is now known as egg
<discord->
Standecco. — I want a mod that adds GR to ksp
<discord->
Sir Mortimer. — GR isn’t greece i suppose
<UmbralRaptop>
I'd only add what, 1-2 orders of magnitude more computation costs?
<discord->
egg. — We'd have to start by rewriting all the geometry abstractions, because we'd need to distinguish vectors from covectors....
<egg>
the very scary thing is that if we want a reference frame where Lagrange points do not move, we really need the rotating-pulsating barycentric frame, and the "pulsating" part means that the inner product form isn't the identity
<egg>
(so we start having to care about covectors vs. vectors)
<discord->
Kobymaru. — is that the moon that's screwing with the inclination?
<discord->
egg. — fancy, GEO over a couple of months?
<discord->
Kobymaru. — GEO, but i think it's just a few weeks
<discord->
egg. — 1 Pe = 1 day, so we could count, but there are a lot
<discord->
Kobymaru. — makes sense
<discord->
Kobymaru. — it's just a "first contract" sat, so I don't care too much. For the next constallation, I'd like to try and find something more stable
<discord->
egg. — yeah it's the inclination messing with the moon
<discord->
egg. — or rather the reverse
<discord->
Kobymaru. — or do GEO sats need that much babysitting usually?
<discord->
egg. — oh yeah GEO is horrible
<discord->
egg. — GEO is quite possibly the most horrible in terms of getting pushed around; anything phased on one day is a bit messy in general (that includes GPS which is semisynch)
<discord->
Kurgut. — is tundra horrible too in this sense? I guess less?
<discord->
egg. — GPS satellites require much more stationkeeping than Galileo, ГЛОНАСС, or 北斗 MEO sats
<discord->
egg. — Tundra or молния noticeably have issues in the long term, you will notice that their longitude of ascending node oscillate a bit like the GEO ones; they are much less affected by inclination problems though
<discord->
Standecco. — shouldn't tundra be in cyrillic too?
<discord->
egg. — the moon-induced inclination mess most pronounced with GEO, because there it's a direct constraint that the inclination must be 0
<discord->
egg. — @Standecco hmm probably, I'm not sure who came up with the name
<discord->
egg. — I don't think it's been used by Russian sats though
<discord->
Kobymaru. — I find it a bit ironic that in stock KSP I used to phase my GEO sats down to .1 ° and quarters of seconds. Now that I use principia, I'm more like "eh, looks stable enough for the next few years"
<discord->
Kobymaru. — no, the whole solar system is tugging at me, so there's not much point to fighting drift 😉
<discord->
Kobymaru. — btw, if I am in a 45° orbit, will the inclination increase, decrease or stay the same but the LAN precess?
<discord->
Kobymaru. — now, the whole solar system is tugging at me, so there's not much point to fighting drift 😉
Jesin has joined #principia
<discord->
egg. — If you make simplifying assumption, you have only periodic variations in a, e, i (both short- and long-period), and long-term drift in Ω and ω
<discord->
egg. — If you make simplifying assumptions, you have only periodic variations in a, e, i (both short- and long-period), and long-term drift in Ω and ω
<discord->
Kobymaru. — i don't know what those stand for unfortunately
<discord->
egg. — @Kobymaru a = semimajor axis, e = eccentricity, i = inclination, Ω = right ascension of ascending node, ω = argument of periapsis
<discord->
Kobymaru. — oh thanks
<discord->
egg. — basically, the plane of the orbit precesses (variation of Ω), the periapsis precesses in its plane (variation of ω), and the rest just messily wobbles around, but shouldn't drift in the long term
<discord->
egg. — One of the simplifying assumptions here is that the Moon doesn't exist
<discord->
Kurgut. — btw, starting to not confound Ω and ☊ anymore makes life easier when reading stuff^
<discord->
egg. — UmbralRaptor: I don't think it really is the maccollo square
<discord->
egg. — @Sir Mortimer since it's garbled, here's what it should say: "Reference frame fixing the target vessel, the plane of its orbit around Kerbin, and the line between them"
<discord->
Sir Mortimer. — so, I'm playing with only one ground station. I cheated my way up the tech tree to get the first relay antenna, now I'm trying to build a somewhat stable relay network around Kerbin.
<discord->
Sir Mortimer. — question
<discord->
Sir Mortimer. —
<discord->
Sir Mortimer. — how stable are orbital periods?
<discord->
egg. — and its name is "target local vertical/local horizontal at Kerbin"
<discord->
egg. — hence the LVLH on the navball
<discord->
egg. — @Sir Mortimer in stock, they're pretty stable, because Kerbin is spherical (no oblateness, so the only perturbations are third body effects)
<discord->
egg. — (this means no sun-synchronous orbits sadly)
<discord->
Sir Mortimer. — ok... good.
<discord->
egg. — @Sir Mortimer if you want a relay network, you should probably go for phased satellites, that way it's easier to reason about where they are
<discord->
egg. — "phased" means the ground track repeats
<discord->
egg. — the most extreme example is geosynchronous
<discord->
egg. — or semisynchronous
<discord->
egg. — but you can also have ground tracks that only repeat over a few days
<discord->
egg. — @Sir Mortimer eventually I'll make an analyser to make this kind of orbit easier to understand, for now you can look at the plot in ECEF (KCKF in your case) and make it repeat itself
<egg>
UmbralRaptop: the maccollo square was in ECI and MCI, not EMB
<UmbralRaptop>
ah
<egg>
whereas Sir Mortimer's screenshot was just an orbit in a 4:1 resonance with the target
<discord->
Kurgut. — could be principia tutorial about Moon
<discord->
Sir Mortimer. — my first time with principia. I tried it out a few years ago, have to say it is a lot faster now. the performance is nowhere near where it was back then.
<discord->
Sir Mortimer. — but.. oh boy. I feel like walking through fog in the dark, backwards, with an empty bottle of scotch in my left.
<discord->
Sir Mortimer. — thank god I packed loads of ∆v 😃
<discord->
egg. — the emptiness of the bottle of scotch seems like a problem
<UmbralRaptop>
Yeah, the bottle should have UDMH or MMH
<discord->
Sir Mortimer. — btw, when planning a maneuver node, is there any way to find out where i have to point my rocket to actually execute that node? is there something like the maneuver marker on the navball?
<discord->
egg. — yeah you have a checkbox that puts it on the navball
<discord->
egg. — (it creates a stock manoeuvre with constant Δv; note that it *does not* go down as you burn like the stock one)
<discord->
egg. — @Sir Mortimer, UmbralRaptor: apparently there are fancy sensors that tilt away from the nadir to avoid sun glint https://www.ncbi.nlm.nih.gov/pubmed/18360519
<UmbralRaptop>
pubmed?
<UmbralRaptop>
I'm going to assume that somehow this is relevant to whitequark
<egg>
I'm not entirely sure how I ended up with a tab open on "Monitoring Algal Blooms in drinking water reservoirs" while researching satellite orbits
<UmbralRaptop>
It seems fairly obvious, really
<egg>
are we going to have to simulate algal blooms
<discord->
Ithirahad Ivrar'kiim. — Simulating planetary events for satellite monitoring actually does sound interesting, albeit also a titanic headache
<discord->
Ithirahad Ivrar'kiim. — or bits of your favorite asteroid getting flung into the sky for no apparent reason (Bennu wtf)
<UmbralRaptop>
YORP YORP YORP
<discord->
Sir Mortimer. — 20degree tilt. hm.
Wetmelon has quit [Ping timeout: 206 seconds]
<UmbralRaptop>
Kerbal planetary Science Program
Jesin has quit [Quit: Leaving]
<discord->
egg. — @Sir Mortimer I guess that kind of thing can/should be abstracted away in sensors that are less affected by glint (tolerate lower solar zenithal angles)
<discord->
Sir Mortimer. — yeah, i was just thinking as to what degree (hah!) that actually makes a difference.
<discord->
Sir Mortimer. — you’re not looking straight down. that’s about it. no idea how much of a problem that is at 20 degrees.
<discord->
egg. — especially since you're looking further along-track, it really makes no difference as to *what* you're imaging
<discord->
egg. — it's the same thing you would have imaged instants later or earlier with a non-tilting sensor
UmbralRaptop has quit [Ping timeout: 202 seconds]
UmbralRaptop has joined #principia
Jesin has joined #principia
<discord->
egg. — @Sir Mortimer it does mean that this approach to eggsperiments and satellite orbits will lead to having lots of distinct instruments, because subtle variations on what the instruments will tolerate can change where you put the satellite
<discord->
egg. — Note that instruments-as-parts is not as bad of an abstraction as one might think, there are lots of instruments that are used on multiple satellites (ScaRaB on Метеор Ресурс, and Megha-Tropiques), MODIS on Terra & Aqua, etc.
<discord->
egg. — Note that instruments-as-parts is not as bad of an abstraction as one might think, there are lots of instruments that are used on multiple satellites (ScaRaB on Метеор, Ресурс, and Megha-Tropiques), MODIS on Terra & Aqua, etc. (edited)
<egg>
UmbralRaptop: do you have other eggsamples of common instruments
<discord->
egg. — Note that instruments-as-parts is not as bad of an abstraction as one might think, there are lots of instruments that are used on multiple satellites (ScaRaB on Метеор, Ресурс, and Megha-Tropiques, MODIS on Terra & Aqua, etc.) (edited)
<UmbralRaptop>
uh, magnetometers, particle detectors, dust sensors, some sort of gamma ray or neutron silliness?
<egg>
UmbralRaptop: do you mean categories of instruments? or specific ones
<UmbralRaptop>
TBF, earth observation is just probes with low launch ΔV requirements
<egg|zzz|egg>
UmbralRaptop: yeah, though there are freshness requirements
<egg|zzz|egg>
which *generally* aren't that big a deal for other planets (obviously LRO is a thing, but even then I'm not sure how often it observes a given spot)
<UmbralRaptop>
Surely storing them in vacuum keeps them fresh!
<UmbralRaptop>
More seriously, MRO or Akatsuki would probably have greater observational freshness concerns
<egg|zzz|egg>
UmbralRaptop: trying to refine my latitude / mean solar time illustration for sun-synchronous orbits with the solar elevation (to show that they steer around sun glint in addition to basking in the sun); what zenith angle threshold should I take for sun glint?
<discord->
neph. — At some point, just go apply to JPL. It's probably easier