hiding behind Mun in KSP.
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- Опубликовано: 27 дек 2024
- Popular science fiction trope is to hide your spacecraft behind the Moon. But is it even possible? I am using modded Kerbal Space Program to showcase L2 Lagrange point orbit and to set this question straight!
![Felix "Unfair" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/Oswujxm2Ag0/mqdefault.jpg)
You guessed it, I am making fool of myself once again! Orbital mechanics makes my monkey brain function once again after high school! L2 point hiding theory debunked! Hera are videos mentioned in his video:
Modded KSP into KSP2: ruclips.net/video/UKbWx-bTOw0/видео.html
Perfectly Balanced Space Shuttle: ruclips.net/video/MfTfWe2uMjg/видео.html
And here a bit on scrapped Soviet Starship: ruclips.net/video/jfb4wlND0WU/видео.html
Theoretically, you could also get into a higher orbit than the moon, increase velocity to make it elliptical, but then constantly thrust radial-in to stimulate the planet having higher gravity. If you math it out right, you could have the higher orbit exactly match the period of the Moon with a fraction of a g of thrust.
That actually an interesting approach! Although I was way off with my trust statement. It is correct only when you need to swap L2 retrograde to prograde orbit every second. And that is not really necessary since L2 visual "shadow" is several days long and you can do orbital swap maneuver only ever so often with fraction of TWR.
Really interesting video, definitely improved my understanding of the Lagrange points, keep up the good work!
Thank you for the kind words Kelso!
Very interesting vid, i'd love to see more principia in future vids!
L1 and L2 are unstable equilibria true but with a bit of station keeping you should be able to stick pretty much dead on it. it's like balancing a pencil by its tip on your finger, takes constant adjustment but doable.
i want those trajectories lines and this cool galaxy background, looks solid)
it should actually be easier to do very low twr burns in principia since it takes burn time into account unlike stock maneuvers. just start burning when the ignition countdown on the flight plan window hits 0 and stop when cutoff countdown hits 0
actually never knew that, nice tip!
Doing orbital burns that way will likely produce an eccentric orbit. The best way I know of is to take the projected burn time, divide by 2, then start the burn that number of seconds before the node.
@@hegemonycricket9549 that works better for stock ksp, but if you do that with principia your trajectory is going to be way different than the one you planned. like i said, principia takes burn time into account so the planned trajectory is the one you will end up on if you follow it
You don't need a large orbit of L2. You can shrink it as much as you like. The halo orbits are intentionally large so that they can see both Moon & Earth at the same time.
Does Principia work in KSP Realism Overhaul? With the realistic planet sizes? I'm curious for I'm working on a totally-hardcore modded game for KSP 1 now that KSP 2 is out.
yes
Thank you! I'll add it soon. :)
Also JNSQ is a nice hardcore take on KSP with stock engines. RO implies usage of more powerful realistic engines, while JNSQ upscale Kerbin 2.7 times and makes stock engines in line with real ones on this scale.
yeah but make sure its on a new save cause will totally ruin one that didn't have principia
@@blockin9556 Good to know. Very important detail. Thanks.
The energy needed to hover wouldn’t be all that bad as the force is essentially the gravitational pull of the Mun from the altitude of the L2 point. I don’t know the altitude of the Mun’s L2 point, but using the mass of the Mun and 2,430 km for the sphere of influence, the continuous thrust needed by a 500T spacecraft would only be around 5.5 kN. This would be lower for the real life moon as it orbits much farther away relative to the scale of things, being closer to 700 N of thrust for the same spacecraft. 700 N of thrust is equivalent to the force a normal human exerts on the ground by standing, so it’s minuscule to output.
Oh snap never considered real thing to have higher and as a result slower orbit! Logic! Also, I was absolutely incorrect in my assumption by treating L2 retrograde / prograde swap every second as continuous burn. L2 shadow is quite big, so retrograde / prograde swap can be done every several days. And it is like 300 m/s of delta V for KSP Mun. So only limiting factor really is fuel efficiency both for IRL and KSP. So you can actually just stay in L2 and "ignore" gravity pull.
i didnt understand anything in this video but cool video and you have a really nice view from the station
Very nice video!
I noticed that you are using Principia together with BetterBurnTime... and... it is... consuming the deltaVs during the burn... My Gosh! How did you managed to get that?
According to Principia documentation that wouldn't be possible:
"Note that, unlike stock KSP, the Δv counter next to the navball doesn't count down as you burn. This is because that countdown is only useful as guidance for burns that are modelled as instantaneous (as in stock KSP), but in Principia burns are applied continuously."
This behavior happens when burning at 6m27s (video time)... but not at 08m56s... Kinda oddly...
pfff who read the instructions! I just rando installed Principia and went from there xD
@@Yakez42 lol... i didnt read either (who plays KSP doesnt needs instructions xD)... but when i realized about this behavior when betterburntime is installed, I've asked Principia creators about it...
kinda weird what happened on video... but lets move on 😅
Can I get a mod list pretty please with a cheery on top of a banana sundae! Also what settings are you using for eve?
6:33 full mod list
I wonder if Sun-Synchronous orbits are possible with Principia.
With stock system you still drift 0.8 degree daily. I am not sure does RO with Real Solar System provide obloid shaped Earth to make these orbit passive as in real life.
@@Yakez42 Ah. Maybe someone could make a config to make Kerbin reasonably oblate
Great video! (If you are interested it’s normal convention to not use nautical terms to refer to spacecraft, most of the people flying up there are ex-pilots so things like Bow and Stern get swapped for Nose and Tail, only commenting as you seemed nervous about your English but it’s very good! Just would be more correct)
Hm, that's interesting never though about astronauts / cosmonauts being pilots at first. Nevertheless they refer to port / starboard side on ISS, so this is where I am coming from originally. Also I never heard Zenith and Nadir terminology in aviation. Is it s space only thing or comes from aviation? And well I watch to much Drachinifel in my spare time xD
You could also put something in the earth-sun L2 point
James Webb Telescope chills there xD
Omg, your previous thumbnail was so good. Why did you change it. 😮
CTR was like 2%. This one went to "normal" 5-10%. I guess it was too abstract and unconnected to my KSP audience ¯\_(ツ)_/¯. If I have kept original thumb probably video would be dead at 300 views.
What mod did you get the solar panels from?
Near Future Solar
anyone gonna talk about how the moon in the thumbnail is actually dres?
My comment about Infinite Discoveries on one of your other videos randomly got deleted. RUclips must be really bugged. Anyway, Infinite Discoveries is about to have an update that adds neutron stars and stuff. You should totally do a review on it
YT bug out sometimes. I had troubles with even posting comments on other channels. Infinite circle and that's it. Infinite Discoveries are on mid term video list. Have even approximate title (this mod turns KSP1 into KSP3) ;-)
@@Yakez42 amazing title
It annoys me that dres is in the thumbnail but great video mate 👍.
Nice catch! Copy pasting from other thumbnail with both Mun and Dres went wrong xD
Him mun thumbnail dres
misa wrong copy paste
Where are you from?
Where did these crazy hovering requirements come from? To hover at the mun sea level you need 0.2g of acceleration to cancel gravity. To hover H meters above sea level you need 0.2/H^2 gees of acceleration. If a mun stationary orbit can exist you can hover above the dark side just for free.
For Moon hovering you need 0.16 gees of acceleration to hover because it's gravity is weaker. To hover 6000km above the surface (L2) you need a continuous output of 4.25e-11 gees of thrust to cancel the moon gravity that is achievable with a real world ion engine.
Selestationary orbit does not exist due to moon uneven gravitational field. L points are sort of these stationary orbits. While I was totally incorrect with my numbers, there is still partial truth to that statement. Idea was to swap between L2 retrograde and prograde orbit to keep craft in Moon visual shadow. That require said trust if you are planning keeping yourself in one relative spot of L2 orbit. Technically swapping retrograde and prograde orbit every single second. But this is so dumb of me! L2 "shadow" is like several days worth of drift, so you need to swap retrograde and prograde orbit only ever so often reducing delta V and TWR requirements drastically.
@@Yakez42 being stationary 6000km above the Moon surface doesn't require prograde or retrograde burns because there is no "prograde" or "retrograde" when the ship is stationary. It just requires 0.00000000004 gees of upward thrust to counter the gravity and prevent falling on the Moon. Due to inverse square law the gravity is this weak at such altitude.
I was wrong: the L2 point is not 6 000km above the Moon, it's 61 000 km away from the Moon. And the reason of it's instability isn't because things fall on the Moon it's because they fly away to a higher orbit around Earth. Being in a halo orbit around L2 point isn't mandatory to stay at L2, it just requires less stationkeeping burns than being in L2 point directly.
Yeah the thing just falls further into "I need to be a scientist to understand this" further you go xD
Something about the way you factored actively holding at L2 just doesn't pass the sniff test for me, but I don't have the mathematical background to really say why.
Yep, I have treated it as continuous swap between retrograde and prograde L2 orbit every second. When with real thing you have L2 "shadow" for several days requiring Prograde/Retrograde orbit swap only ever so often. Roci totally can do this. Real spacecraft more than several times, not so much.
@@Yakez42 The way you described is like flying in a tiny circle at orbital speed in order to hover just above the earth's atmosphere instead of just pointing the engine down at 1g
You shouldn't need to move at escape velocity. You need 1munar gravity or less.
Hovering is hovering. Being far away just means the influence drops off. The delta v per second to hover behind the moon is exactly equal to the acceleration of gravity towards the moon (and Earth) at that point (ignoring all other mass in the universe to simplify the calculation). Can we do it? Nope. That's a whole lot of fuel. Could Rocinate? Probably. For the duration of a given time travel story, it seems possible.
There's a rule of thumb in "hard-ish" sci-fi. You get one piece of handwavium. One technology that is way more fiction than science. For the Expanse, that tech is the Epstein Drive. It provides ultrahigh nuclear engine thrust at impossible efficiency. That's why they almost never mention fuel. So, for any normal hide behind the moon time frame, the Roci would need a tiny fraction of its max output. It might as well have infinite fuel.
I don't think I got any of that wrong.
Yeah I was probably way off with my logic and was hoping for some enlightening comments xD My logic was based on my attempts to hover in Kerbin orbit, but since it rotates you need to go in such a ridiculous burst back and forward. Mun is different for sure thanks to tidal locking and slower orbit. But wouldn't you still lag behind the Mun since your orbit higher that that of a Mun relative to Kerbin? So if you stop you are moving slower and lag behind. It feels like continuous trust is not necessary, but you still need to go back and forth accelerating and decelerating in shorter part of L2 orbit hidden from Kerbin. Basically swapping between retrograde and prograde L2 orbit?
And with Expanse they also completely ignore thermodynamics in space. Epstein drive heat buildup should be enormous! Surprisingly even Start Wars thought about adding radiators to X-Wing back in the day xD
@@Yakez42 You just need to match radial velocity with the moon/mun. Kinda like how geosynchronous orbits match the speed of the Earth's surface from way up in space. Since there's probably not a point where this is both practical and stable, you need to apply thrust to stay in synch with mun/moon's movement but I'd guess it doesn't even have to be continuous. Just regular correction burns.
The Roci, tho, could park itself somewhere that requires the engines on all the time to maintain position (like 1km from the lunar surface) so long as the instantaneous acceleration of gravity at that point was less than five kilometers per second. The instantaneous acceleration of gravity at the moon's surface is about 0.00162km/s. Roci could hold that for days or weeks, probably. The limitation would be when do they need to shut down the engine so Amos can work on it.
I believe TVTropes refers to that as "Minovsky Physics"
By the way, Epstein didn't kill himself.
I'm not a fan of the thumbnail, but the video was cool!
Have some free Engagement!
The number of vids on your channel right now is like: 💀💀💀
Do not really understand what do you mean. If you say that they are dead... well YT is not a sprint. Quality stuff rise together with viral stuff eventually. Needless to say it is better to have 10k views on my KSP video than 100k on old Path of Exile videos. Community response is way better and you always learn new stuff.
@@Yakez42 I'm saying about the number: 69
haha also though about that. Channel have around 10-15 hidden videos and from PoE and New World era tho. So technically it is more for quite some time.
just hide in l2
this shi too easy man