<wb99999999>
the outer 4 engines looks quiet different from the inner 4 engines on the Saturn 1B
<wb99999999>
anyone knows what is that big tube surrounding the bellÉ
<wb99999999>
*the bell?*
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<ProjectThoth>
wb99999999: It's how they dealt with the gas gen on the outboard engines.
<ProjectThoth>
It was called an "aspirator" in the technical lingo, but all it meant was that the gas gen exhaust would be dumped in an anuular exhaust port mounted to the aft end of the bell.
<ProjectThoth>
The inboard engines vented exhaust on the outer rim of the stage. Heating issues, basically.
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<wb99999999>
so basically they don't have enough room for all 8 engines to dump gas-gen gas on the bottom plate?
<ProjectThoth>
No, they were worried about base heating.
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<awang>
ferram4: Are flaps on the leading edge of wings worth adding to planes?
<ferram4>
Depends on your problem.
<ferram4>
Are your wings stalling because you're reaching too high an AoA during landings?
<ferram4>
If not, there isn't any reason to add them. All they do is increase the critical angle of attack.
<blowfish>
am I correct in saying that slats, as used on most commercial airliners these days, are not modeled by FAR?
<awang>
Nah, haven't been having issues with landing
<awang>
Just curious
<awang>
But glad to know that that's the effect
<ferram4>
They are modelled by FAR, just not as well as they should be.
<awang>
Should help keep some of the complexity out of my plane designs
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<awang>
What's missing modelling-wise?
<blowfish>
ferram4: how would you even create them? Put a gap between the leading edge and the main wing?
<ferram4>
awang, just general inaccuracies in the lift slope and induced drag, like the rest of the wing model.
<ferram4>
blowfish, In terms of modelling, there isn't much difference in the way a leading edge flap and a slat actually function. The slot is abstracted away completely.
<blowfish>
airliners don't fly a particularly high AoA though
<blowfish>
so how would increasing the critical angle help?
<blowfish>
unless the angle of the flaps matters too?
<ferram4>
Because it lets them land at a slower speed.
<blowfish>
so is the critical angle really low enough that airliners would hit it without slats?
<ferram4>
And then even further to have the margin to have no risk of stalling at those speeds.
<ferram4>
Think about it this way: for general airliner wing shape, the stall angle varies between 15-25 degrees.
<ferram4>
Without flaps.
<ferram4>
Deploying just flaps reduces the stall angle (because the flow near the leading edge ends up being deflected upwards, so higher local AoA for a given freestream AoA)
<ferram4>
And regulations require ~20% margin on stall angle for the design landing speed and angle of attack.
<ferram4>
So... yeah, it really is that low.
<blowfish>
huh
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<xShadowx>
the only time i ever used leading edge flaps, was so i could raise/lower altitude whilwe plane still stays at the same level flight ;3 never understood why til now
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<blowfish>
I definitely used them for high AoA designs...
<taniwha>
passenger craft landing speeds seem to be in the 60-70m/s range
<taniwha>
(from watching the m/s display on my phone (gps) during one landing, and the airspeed display on another (about 137knots))
<xShadowx>
arent you posed to turn off phone at landing/takeoff ;p
<taniwha>
airplane mode is fine
<blowfish>
not like it really affects anything
<xShadowx>
used to, dunno about modern lol
<taniwha>
cellphones being turned of is required by the fcc, not the faa
<xShadowx>
wonder if cell towers could keep up ;3
<xShadowx>
new tower every fraction of a sec lol
<taniwha>
not only that, but the 370km los vs 15km los
<taniwha>
(assuming 20m tower)
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<taniwha>
Cassini hit Saturn faster than Earth's orbital velocity
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<Probus>
I wonder what the last picture will look like...
<taniwha>
a Saturn-dear stuck in Cassini's headlights
<taniwha>
er, deer
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<awang>
At what point in the SRB thrust curve am I supposed to jettison them?
<awang>
Right after the thrust starts tapering down?
<awang>
At burnout?
<awang>
Sometime between?
<TheKosmonaut>
taniwha: The Cassini project total time from approval till now was 1 saturn year :)
<TheKosmonaut>
around 30 earth years
<taniwha>
yeah
<taniwha>
caught that bit
<hattivat>
awang: once their TWR goes below 1
<hattivat>
hard to tell when exactly that is, usually a little before burnout
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<blowfish>
Does RO have any version of Vanguard's original third stage? (the Grand Central solid motor)? I searched and didn't find one. I know it has the Altair but I think that was a bit later.
<blowfish>
The 33KS2800
<blowfish>
Oh, US rockets has one
<blowfish>
no test flight configs though
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Guest6727 is now known as BadRocketsCo
<soundnfury>
oh hey BadRocketsCo
<BadRocketsCo>
ohay
<BadRocketsCo>
soundnfury: how has life been?
<soundnfury>
Variable.
<BadRocketsCo>
I don�t think we have talked for like 3 months, heh
<soundnfury>
My hard drive died a few weeks ago; I've replaced it with an SSD
<soundnfury>
but I still need to attempt some data recovery
<BadRocketsCo>
oooh, ouch
<BadRocketsCo>
lost anything very important?
<soundnfury>
nothing _seriously_ important
<soundnfury>
but I had a whole branch of Harris not pushed, and some unfinished musical arrangements and stuff
<BadRocketsCo>
oh, atleast there�s that
<BadRocketsCo>
got any projects going on in RO?
<soundnfury>
basically it's stuff I'm _annoyed_ to have lost
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<BadRocketsCo>
Aaand back
<soundnfury>
side
<BadRocketsCo>
It must've been quite the hassle to put all this together
<BadRocketsCo>
And I am guessing that's just the beginning
<soundnfury>
well, now we probably have a long road of bugfixing ahead of us ;)
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<soundnfury>
!wpn BadRocketsCo
* Qboid
gives BadRocketsCo a furious-sounding zygomorphism
<BadRocketsCo>
Huh
<BadRocketsCo>
!wpn soundnfury
* Qboid
gives soundnfury a hydrargentium Brand New Photoneutronic Engine with a 2N3904 attachment
<BadRocketsCo>
I didn't understand a word of that...
<soundnfury>
(blame #kspacademia)
<soundnfury>
well, hydrargentium is Hg — mercury
<soundnfury>
and a 2N3904 is probably a diode, or maybe a transistor. But probably a diode, because @diodelass
<BadRocketsCo>
But what is a photoneutronic engine? :D
<soundnfury>
xkcd 28
<BadRocketsCo>
Hah, okay :D
<BadRocketsCo>
Googling that just gives me chat logs from #kspacademia
<soundnfury>
I like how "images for" is an otter.
<BadRocketsCo>
Hah
<BadRocketsCo>
Well, some googleing later it appears that photomeutrons are neutrons that are ejected from a nucleus by a high energy photon
<BadRocketsCo>
I am guessing you could use that effect to create some sort of propulsion device in space
<BadRocketsCo>
Curious
<soundnfury>
sounds even less practical than a fission fragment rocket
<BadRocketsCo>
Heh, probably
<BadRocketsCo>
Maybe that's the joke
<BadRocketsCo>
Man, kspacademia folk are advanced
<soundnfury>
yes, we are.
<soundnfury>
Also, extremely strange.
<soundnfury>
And representable chiefly in Unicode.
<BadRocketsCo>
Name me one person in history that isn't extremely strange :D
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<BadRocketsCo>
Oh, also. I am studying telecommunications now!
<soundnfury>
John Major.
<Kropotkin>
He had an affair with Edwina Currie.
<soundnfury>
He can't have been strange, because strange things are interesting and memorable.
<BadRocketsCo>
So in 3 years I will actualy understand some IT and tech stuff
<BadRocketsCo>
So that's pretty cool
<soundnfury>
BadRocketsCo: nice
<BadRocketsCo>
soundnfury: touché
* soundnfury
gives BadRocketsCo a ½λ
<BadRocketsCo>
Anyway, sleepy time for me
<BadRocketsCo>
Nighty night
<soundnfury>
ttfn
<awang>
Jeeze, just how much runway does the Bonaza need?
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<Kropotkin>
awang, it depends?
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<soundnfury>
heya nines
<wb99999999>
hello
<wb99999999>
I was playing around with a Saturn IB replica, and started to wonder how short-burning a first stage need to be to become inefficient
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<wb99999999>
you know, S-I only burns for 160s and is in charge of only about 1/3 to 1/4 of the total delta v to orbit
<soundnfury>
yes, but it has a high TWR no?
<wb99999999>
no, actually
<wb99999999>
Saturn series of rockets have VERY low starting twr
<wb99999999>
usually less than 1.2
<wb99999999>
especially when they're lifting the heavy LEO payload they're designed to launch
<soundnfury>
right but it gets pretty high over the course of the burn?
<wb99999999>
not above 4.5 anyway, NASA in the 60s treated 4.5G as the maximum for a man-rated launch
<soundnfury>
I find that long burn times matter more for upper stages, because their higher Isp means they lose mass less quickly, thus the TWR stays low for longer
<wb99999999>
yes, but lower stage being in charge of too little delta v is also bad, if I am right on this
<soundnfury>
in the limit, sure
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<soundnfury>
but it's a nice gentle curve, and so the differential is small near the maximum, so quite a broad range is 'good enough'
<wb99999999>
can you explain more of the math to me?
<soundnfury>
uhh, well, you just take the multistage rocket equation and you make the stage split ratio (mass_upper / mass_lower) a parameter, which you can then differentiate and that tells you where the extremum is
<soundnfury>
(and you know it's a maximum because the endpoints are effectively single-stage rockets, and staging is a thing that works)
<wb99999999>
right
<soundnfury>
(note: I haven't actually _done_ this so I don't know how ugly the algebra gets, but it's still "trivial")
<wb99999999>
probably it doesn't matter that much for usual application
<wb99999999>
it's just interesting if you compare maybe the Atlas V core and Proton
<soundnfury>
yeah well in practice you're usually driven more by what engines are available (or can be designed)
<wb99999999>
true
<soundnfury>
especially early on when something like an Able can only burn for 150s, so starts at TWR > 1
<soundnfury>
(which is _insanely_ high for an upper stage, even one that ends at LEO)
<wb99999999>
ah, Nathankell had this trouble before
<wb99999999>
On his stream PEG basically pitched down his upper stage 20 deg or so
<wb99999999>
and he's a bit dissapointed about this
<soundnfury>
ah see I don't tend to have that problem, because konrad (unlike PEG) can be used for launch profiles with coast phases ;)
<wb99999999>
I guess in that case just let MJ gravity turn for you and apogee-kick by hand
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<soundnfury>
ehh, if your apogee motor is an Able that burns for 150s, you can't just eyeball it without incurring a bunch of steering losses when you realise you guessed wrong
<wb99999999>
what about using a node?
<soundnfury>
doesn't help - nodes are instantaneous
<soundnfury>
this is why konrad is great, it's basically a node that integrates over your full burn
<egg|zzz|egg>
Principia does that too *slinks back into the shadows*
<soundnfury>
egg|zzz|egg: yes, but I'm guessing nines is even more scared of principia than I am
<egg|zzz|egg>
:D
<soundnfury>
!wpn egg|zzz|egg
* Qboid
gives egg|zzz|egg a Gaussian expansion
* egg|zzz|egg
throws an atomic clock at wb99999999
<wb99999999>
whatever is going on...
<egg|zzz|egg>
(the atomic clock now runs slightly late)
<wb99999999>
I am not actually scared of pincipia
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<wb99999999>
I loved it
<wb99999999>
it's just I can't use it without a bunch of slow downs until I got around to plug a pair more RAMs on my PC
<wb99999999>
and the UI is a bit of...convoluted
<egg|zzz|egg>
yeah, it is
<wb99999999>
I can't be more happy about the premise itself though
<egg|zzz|egg>
also tilt :D
<egg|zzz|egg>
n-body nyancats (ok that doesn't use principia right now, I need to get Sarbian to use better integrators)
<wb99999999>
btw was Scott Manley really involved in the retrograde POI (was this the moon that caused the break down
<wb99999999>
gosh, I pressed enter...
<wb99999999>
that was supposed to be an interrogative sentence
<egg|zzz|egg>
scott and UmbralRaptor both suggested retrobop iirc
<wb99999999>
oh right, it was bop
<soundnfury>
all hail retrobop!
<wb99999999>
got to say they're some really freaking smart people
<wb99999999>
I'm no physicist so maybe I am to dumb to get it, but It seems quite abstract
<wb99999999>
got an unstable system? have one of the moon go retrograde
<wb99999999>
problem solved
<soundnfury>
iirc moons are basically like oblateness? I dunno quite why retrograding affects that though
<soundnfury>
something something resonances
<egg|zzz|egg>
there's more than retrobopping happening here, the system was widened a bit because the moons were just too close (and resonating which didn't help)
<UmbralRaptor>
It's notably useful for tiny and distant moons (something about briefer close encounters IIRC)
<soundnfury>
egg|zzz|egg: but galilean resonants!
<egg|zzz|egg>
but then that left no room for bop, so to keep it reasonably close UmbralRaptor suggested retrobopping
<soundnfury>
(I guess the moon mass is just too high for a galilean system to work)
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<egg|zzz|egg>
well jool is ridiculously light compared to the moons (which arguably stems from the moons being impossibly dense)
<UmbralRaptor>
soundnfury: Jupiter is like >1e4 times the mass of its moons. Jool is only 80x Tylo, and 100x Laythe.
<soundnfury>
yeah, that
<egg|zzz|egg>
dump a hundred more jools in there and it'll work
<soundnfury>
energetic!
<UmbralRaptor>
If you take Kerbin to be Earth, Jool is an underweight Saturn orbited by 3 terrestrial planets.
<UmbralRaptor>
Incidentally, I think I overestimated the moon:Jool numbers. 1:100 for Tylo.