<taniwha>
t=orbit period, u = body gravitational parameter
<Slaintemaith>
Ergh. Where would I find those numbers? In a nice .cfg file in the Sigma directory somewhere, I hope?
<soundnfury>
you want to balance grav. and acceleration, so GM/r² = r*(angular velocity ²), iirc
<soundnfury>
Slaintemaith: if you already know the period for some other orbit, you can use Kepler's equation
<taniwha>
Slaintemaith: info panel in map view
<soundnfury>
s/equation/third law
<Qboid>
soundnfury meant to say: Slaintemaith: if you already know the period for some other orbit, you can use Kepler's third law
<taniwha>
(after focusing on the body)
<taniwha>
soundnfury: I just gave K's 3rd for circular orbits :)
<taniwha>
(but solved for r instead of t)
<soundnfury>
which is that T² is proportional to a³ (where a=semi-major axis)
<soundnfury>
taniwha: yeah but if you don't know GM...
<taniwha>
KSP tells you GM
<Slaintemaith>
Okay, I have GM.
<Slaintemaith>
2.21E+13
<taniwha>
Slaintemaith: rotation period is there, too
<Slaintemaith>
Heh. 1D.
<Slaintemaith>
=)
<taniwha>
*sigh*
* taniwha
glares at #RO
<Slaintemaith>
Sorry. I suck. I know.
<soundnfury>
Slaintemaith: is that a real day, or a 6-hour day -_-
<taniwha>
Slaintemaith: not sure if you want 86400 or slightly less
<taniwha>
or whatever the day is
<taniwha>
(86400 for earth, 21600 for stock Kerbin)
<Slaintemaith>
I'm using Kronometer.
<Slaintemaith>
I'm not sure if that helps.
<taniwha>
er, or would it be slightly more?
<taniwha>
less I suspect
<taniwha>
yes, less
<Slaintemaith>
I'm thinking it's a real day, not a 6-hour one.
<soundnfury>
yeah, for Earth it's 23h56m04s.
<soundnfury>
Correction depends on number of days in a year
<taniwha>
actually, number of seconds :)
<Slaintemaith>
Yes. Real day. At least day 1 didn't happen when I went past 6 hours.
<Slaintemaith>
(I guess this is probably a bad time to mention I failed math)
<taniwha>
Slaintemaith: nah, if you keep at this sort of thing, you will succeed at math
<Slaintemaith>
So I'm solving for how many seconds are in a year that has days of 23h56m04s?
<taniwha>
ok, stock kerbin does show a proper rotation period (5h49m9s)
<taniwha>
Slaintemaith: no, just use 86346s for your orbital period
<taniwha>
if that's wrong, then the day is different
<Slaintemaith>
What's pow, then?
<taniwha>
power
<taniwha>
common programming funciton. a^b (2^3 = 8)
<soundnfury>
taniwha: wait, where'd you get 86346 from?
<Slaintemaith>
Oh. Heh. I only break things. I'm no programmer.
<taniwha>
so pow(a,1.0/3) give cube root
<taniwha>
soundnfury: 86400-56
<soundnfury>
uh, correction is 3m56s, not just 56s
<taniwha>
soundnfury: messed up though, because I misread 56 and 59
<soundnfury>
and like I say, that's only correct for a 365-day year
<taniwha>
s/and/as/
<Qboid>
taniwha meant to say: soundnfury: messed up though, because I misread 56 as 59
<soundnfury>
sidereal day = solar day * (days in year - 1) / days in year. Or something like that.
<taniwha>
then Slaintemaith will need to look at Kerbin's SMA and the sun's GM
<taniwha>
and calculate the year in seconds
<taniwha>
and use 86400 for the solar day
<Slaintemaith>
Well, this is RSS--just 2.5x
<Slaintemaith>
2.5x Kerbin-sized. I guess that's---nevermind.
<Slaintemaith>
I don't know what an SMA is.,
<taniwha>
(or whatever the day is)
<taniwha>
Slaintemaith: semi major axis
<taniwha>
also given in map view
<taniwha>
it's the "a" (or r) in the equation
<Slaintemaith>
Not finding the SMA in map view. At least it's not anyplace I'm expecting it.
<taniwha>
focus on kebin
<ProjectThoth>
Slaintemaith: It's a function of altitude plus the radius of whatever thing you're in orbit of.
<taniwha>
oh, hang on
<Slaintemaith>
I did. I have.
<taniwha>
just remembered, it's not there
<Slaintemaith>
=)
<taniwha>
since it's kerbin, the orbit will be circular
<taniwha>
just look at kerbin's altitude and check the sun's radius
<taniwha>
add the two together
<taniwha>
Slaintemaith: anyway, t = t1*t2/(t1-t2) for sidereal -> solar (t1+t2 for solar -> sidereal)
<Slaintemaith>
It's earth, and the altitude is changing.
<taniwha>
*grumble*
<Slaintemaith>
It's a 2.5x RSS system.
<Slaintemaith>
(If I could have a working shuttle I'd just use RSS and RO and not worry about it.)
<Slaintemaith>
But that's another headache...
<taniwha>
I'd forgotten how difficult it is to get orbital data out of KSP
<taniwha>
(easy enough with a mod, but I don't know of any mod that gives the data for bodies)
<Slaintemaith>
Mechjeb is useful for ship orbital information, but not celestial bodies.
<soundnfury>
why not just look in the Kopernicus cfg files?
<taniwha>
it will certainly give GM (or just mass. G is constant) and SMA
<taniwha>
soundnfury: while there's that, people should not have to look in config files for such info
<Slaintemaith>
I'd mentioned that before--I just thought it'd live in /sigma.
<taniwha>
however, looking in BeforeKerbin's data, SMA is indeed there (semiMajorAxis)
<taniwha>
GM can be calculated from geeASL * 9.8066 * radius^2
<Slaintemaith>
Earth 1500km radius, 86400 second day.
<taniwha>
you need sidereal for geostationary
<taniwha>
that will be solar
<Slaintemaith>
That's from the 2.5x ssrss config file.
<taniwha>
yeah
<taniwha>
so grab the sun's GM using the above, and Earth's semiMajorAxis, and then you can calculate the year in seconds
<taniwha>
then use year * 86400/(year + 86400) to get sidereal day in seconds
<taniwha>
year = sqrt(2*pi*sma^3/GM^2)
<Slaintemaith>
sun GM 7.357e+18
<Slaintemaith>
We never found the SMA.
<taniwha>
look in Earth's config
<taniwha>
should be there as semiMajorAxis
<Slaintemaith>
If I'm honest, I don't even know what calculations I'm trying to calculate to get the formula I'm trying to get to anymore.
<Slaintemaith>
But I do appreciate the attempt at helping.
<taniwha>
you're trying to get the correct orbital period for geostationary orbit
<taniwha>
you use the sidereal day for that
<ProjectThoth>
2.5x scale Kerbin still has a rotational period of 24 hrs, right?
<ProjectThoth>
Er.
<ProjectThoth>
It's like the Kerbin system, just made embiggened.
<Slaintemaith>
I don't know what a sidereal day is.
<taniwha>
Slaintemaith: rotation relative to the stars rather than the sun
<Slaintemaith>
Which is making me think that this is really all above me and I shouldn't be meddling with such things.
<ProjectThoth>
Slaintemaith: Okay, so you know how a day is based off of how long it takes to go from sunrise to sunrise?
<taniwha>
Slaintemaith: nah, it is NOT above you
<taniwha>
and you very much SHOULD be meddling
<ProjectThoth>
That's what's called a "solar day." But you have to keep in mind that the Earth is also on a long journey around the Sun.
<taniwha>
yes, it is beyond your current knowledge, but there's only one way to extend the boundaries of your knowledge
<Slaintemaith>
Well, I've not seriously considered tackling any math problem since advanced algebra in college, which was in the 80's, and also which I failed.
<ProjectThoth>
So astronomers came up with this concept called the "sidereal day", which takes into account the motion of the Earth around the Sun.
<taniwha>
Slaintemaith: then just take it slowly
<taniwha>
Slaintemaith: you've got sun's GM and earth's semi major axis, right?
<Slaintemaith>
Uh.
<Slaintemaith>
No.
<Slaintemaith>
I only have the Sun's GM.
<taniwha>
ok, get Earth's SMA. look in the config file, search for semiMajorAxis
<taniwha>
(we'll do this step by step:)
<Slaintemaith>
I'm not sure which .cfg that's going to live in. If I were using linux, I'd just SAR the dir...
<Slaintemaith>
But the configs are spread out over a number of mods. Sigma dimensions, SSRSS, probably rescaled from RSS, and then I have a separate config I'm using as well.
<taniwha>
yeah, I see that
* taniwha
glares at Sigma88
<Slaintemaith>
So a side question: Anyone get Pak's shuttle working in RSS/RO?
<Slaintemaith>
I know there's configs for it, but I think the SRBs are non-RO. Or maybe the SSMEs. Or the OMS engines. I forget now, I just know I had more issues than National Geographic with it.
<taniwha>
Slaintemaith: what's Earth's radius?
<taniwha>
(in your game)
<taniwha>
oh, nm, you said 1500km earlier
<Slaintemaith>
Yeppers.
<taniwha>
I don't see where the 2.5 comes from
<taniwha>
the rescale given in the configs puts it at 600km instead of 1500km
<Slaintemaith>
The 2.5 is a separate config. one moment.
<taniwha>
oooooh, so SSRSS puts RSS at stock scale, then a second config to put it at 2.5
<taniwha>
Slaintemaith: I get 15312720.714580547s for the year
<taniwha>
giving 85915.23465927948s for the sidereal day
aradapilot has quit [Ping timeout: 383 seconds]
BadRocketsCo has joined #RO
BadRocketsCo has quit [Ping timeout: 383 seconds]
aradapilot has joined #RO
<Slaintemaith>
I gave up. Sorry. I know. I suck. "Why do you keep beating your head against the wall?" "Because it feels so good when I stop."
ProjectThoth has quit [Ping timeout: 182 seconds]
<taniwha>
Slaintemaith: one step at a time
<taniwha>
and you are not beating your head against the wall
<taniwha>
(that's just "ignorance is bliss" indoctrination speaking to you)
<taniwha>
Slaintemaith: it took me about 28 years to crack the final steps of deriving the mean anomaly equation from first principles, but it sure felt good when I did crack it :)
<taniwha>
Slaintemaith: and if you stick with the "beating your head against the wall" bit, ok, sure it feels good when you stop, but think about how good it will feel when the wall crumbles }:>
<Slaintemaith>
Well, yes. But not tonight. =) I've moved on to trying to find an autopilot that works with the Cormorant Aeronology shuttle for RSS/RO. And also why one set of SRBs work and another set doesn't.
<taniwha>
Slaintemaith: very much agreed. One step at a time.
<Slaintemaith>
Thanks again for the help. I'll try again tomorrow.
<Slaintemaith>
My next suspicion is that I won't be able to add thrust curve changes directly into this SRB.
TM1978m has quit [Remote host closed the connection]
<Slaintemaith>
Oh hai! Let's say I wanted to rescale the way a part appears in game. (Not the performance, but the size of the model) by a factor of 1.x. Is there a line I can drop in the engine.cfg to make that happen? Or is it more complicated than that?
<taniwha>
rescaleFactor = XXX
<taniwha>
default is 1.25
<Slaintemaith>
Is there a section that specifically needs to live in?
<Slaintemaith>
Module?
<taniwha>
needs to be in the main PART block
Mike` has quit [Ping timeout: 383 seconds]
<Slaintemaith>
That's where it gets trickier. Tracking down the actual part. I'm guessing RO engine configs are patches, and wouldn't have that section.
<taniwha>
RO patches will have PART[something]...
<taniwha>
so in that block
Mike` has joined #RO
<Slaintemaith>
Found it. Guessing I'll need the prerequisite %
<Slaintemaith>
Hrm. Didn't do anything. =(
<taniwha>
I'm no MM pro, sorry
<Slaintemaith>
@PART[*]:HAS[#engineType[RSRM]]:FOR[RealismOverhaulEngines] { %title = RSRM %manufacturer = Thiokol %description = A four segment Reusable Solid Rocket Motor, one of the most powerful rocket motors ever built and flown. Two of them were used by the Space Shuttle for liftoff and the initial part of the flight, providing more than 75% of the overall stack thrust. Manufactured by Thiokol and later by ATK. Diameter: [3.7 m].
<Slaintemaith>
No worries.
<taniwha>
ouch, you would not want to edit that anyway
<taniwha>
should make a new patch with the specific part you want to edit
<Slaintemaith>
Because in the launch video you cannot see the water tower.
<Slaintemaith>
And they probably move the rocket as short a distance as possible, thus it's going to be on 'this' side of the gantry.
<Slaintemaith>
SpaceX building is to the west, water tower to the SE.
<awang>
Slaintemaith: Wind directions are the direction the wind is coming from, IIRC
<awang>
So wind blowing ESE means the condensation should move west-ish
<Slaintemaith>
Well. Then. You know. The opposite of that.
<awang>
WNW, I think?
<Slaintemaith>
I'm saying the condensation appears to be moving from west-to-east.
<awang>
Oh
<awang>
Never mind then
<Slaintemaith>
There's a water tower near the gantry that one should be able to see in that video unless 1) The gantry is occluding it--which which case my point is still valid, or the tower is behind the camera, in which case it still makes for wind blowing from the westish to the eastish.
<Slaintemaith>
+2)
<Slaintemaith>
It would actually make sense if the camera was ~on~ the tower...
<awang>
There's a video taken from the VAB roof
<awang>
That should make direction really easy to determine
<awang>
!tell Bad*Co Never mind, RealHeat master has been rebuilt for 1.3.1
<Qboid>
awang: I'll redirect this as soon as they are around.
ProjectThoth has joined #RO
BadRocketsCo has joined #RO
BadRocketsCo has quit [Read error: Connection reset by peer]
BadRocketsCo has joined #RO
BadRocketsCo has quit [Ping timeout: 186 seconds]
stratochief has joined #RO
Slaintemaith has joined #RO
<Slaintemaith>
So I did the 'blunt object' approach of getting geosync orbit. I cheated and kept plugging in numbers until my orbital period was 24 hours even. I know that's not a sidereal day, but how much will that make a difference, really, in terms of this game and relay satellites?
<UmbralRaptor>
For relay purposes, and constellation in a consistent high orbit works.
<soundnfury>
yeah, KSP doesn't really model fixed-dish ground antennas as a thing
<soundnfury>
UmbralRaptor: he's using some sort of scaled solar system
<soundnfury>
"2.5x" something apparently
<UmbralRaptor>
oh
<Slaintemaith>
Which makes it wonky.
<Slaintemaith>
I can say that the 24 hour orbit solves the question of 'how does time behave in your world?' since it's -almost- geosynchronous. Only way you can tell at max accel is that the gps coordinates keep shifting west. (or east)
<soundnfury>
Slaintemaith: really the only advice I can give you is to learn kinematics so you can understand&calculate orbital mechanics stuff
<Slaintemaith>
That said, I know that 2.5x RSS geo sync orbit is -close to- 16,074,166.
<soundnfury>
it's really not very easy to explain to someone who doesn't already have the shared context of 'the mathematics of motion'
<Slaintemaith>
Ack. no that's the semi major axis.
<Slaintemaith>
True. But the fact is: I failed algebra in college. I was an English major, and I have a knack for breaking software.
<Slaintemaith>
It seems unlikely I'll develop that skill set in this current lifetime.
* soundnfury
doesn't believe there are people incapable of learning mathematics
<soundnfury>
just different people give up trying at different levels
<soundnfury>
I didn't give up until I got to finals year :P
<Slaintemaith>
I gave up college before finals year.
<soundnfury>
(I managed to scrape a pass, but barely)
<soundnfury>
but yeah, if you were to decide you wanted enough to understand it, you probably could
<soundnfury>
but if you decide that's not for you, that's also fine
Hypergolic_Skunk has quit []
Hypergolic_Skunk has joined #RO
<Slaintemaith>
I suppose it's possible. I think mathematics is largely building on stuff that one learns prior-to. In a layered format.
<soundnfury>
(I just don't want you wrongly believing it's impossible)
<Slaintemaith>
And there's a LOT of layers I'd need to learn to get to making the calculations you guys were suggesting I do last night. =)
<soundnfury>
really mathematics is more learning habits of thought & problem-solving strategies, rather than declarative knowledge ;)
<soundnfury>
but yes, there are a lot of dependencies. That's why I gave up trying to explain it and left it to taniwha xD
<Slaintemaith>
Sure. But physics adds an element to it--knowing what it is you're calculating and what you need to know -to- calculate it.
<lamont>
i always learn math backwards from how math profs teach math
<lamont>
pushing numbers around symbolically for the sake of pushing numbers around i find mind-numbing
<Slaintemaith>
Anyway... then there's 'order of operations' which I promptly forgot in 1989.
<Slaintemaith>
Sadly to be replaced by Red Hot Chili Peppers lyrics, most likely.
<Slaintemaith>
Anyway...
<soundnfury>
Slaintemaith: it's not as complicated as people make it. It's just that * binds tighter than +, and brackets are a thing.
<soundnfury>
(and / is a type of *, and - is a type of +, and you probably don't need to worry too much about exponentiation)
<Slaintemaith>
=)
<Slaintemaith>
Anyway... with a 24 hour orbital period altitude achieved, even though it's not a sidereal day, I'm calling it 'close enough for Kerbal.' Now I'm going to buy some tequila.
<soundnfury>
Just be glad you're not using principia, or you'd need something stronger than tequila
<soundnfury>
(I don't know whether such a thing exists; I'm a non-drinker ;)
<Slaintemaith>
If anyone's bored, they can check to see how close I got with a circular orbit of 14.5742Mm
<Slaintemaith>
Oh yes, many things stronger exist.
TM1978m has joined #RO
ProjectThoth has quit [Ping timeout: 383 seconds]
TM1978m has quit [Remote host closed the connection]