Why Spacecraft Are Using These Crazy Routes To The Moon - Weak Stability and Ballistic Capture.
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- เผยแพร่เมื่อ 18 ธ.ค. 2022
- For decades spacecraft would fly direct to the moon and then brake into lunar orbit, but these days most spacecraft take long circuitous routes, dancing on the edge of stability near the lagrange points of the sun-earth-moon system. These techniques save propellent at the expense of time and navigation complexity.
They use the theory of weak stability boundaries and ballistic capture in the 3 body problem, to make this possible, and it's an idea which was first discovered in the early 1990's and has now become the main route for modern spacecraft.
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Hitchhikers Guide to Lunar Orbit
Don't Panic
Gravitate to the watering hole, Drink 3 intergalactic gargle blasters and wait for the gold brick wrapped in lemon to smash your head.
Then everything seems so normal!
🖖
Do YOU know where your TLI burn towel is?
@@andrewharrison8436 if you got your thumb out, not enough time to panic.
I’m an orbital mechanics engineer at ESA and I wouldn’t have explained it better 👏🏼👏🏼
hi, do you know Prof Mark McCaughrean?
No offense but probably worse for the layman
I'm not an orbital mechanics engineer at ESA and I definitely could have explained it worse than either of you
Awesome
I'm an orbital mechanics engineer at KSC and I have no idea how to reach orbit. I just add more boosters.
This is mathematically and physically beautiful and I cannot imagine the happiness the original scientists felt when putting all of this together
As a straight man, I don't think penises are beautiful, but hey, you do you! 😆
@@conradandrew825 U not seen them tip to tip then =/
It always strikes me how complex yet simple orbital mechanics are. Like, it's absolutely complex but we can VERY easily describe the movements of the heavens with surprising accuracy far into the past or future with "simple" equations.
Belbruno almost lost his job at JPL researching this topic in the early days LOL. There's a TEDtalk he did on it quite a while back.
Never mind KERBAL space program... what about *HERBAL* space program? Take enough herbal stuff and you'll *REALLY* feel as if you're flying. It might technically be ever so slightly illegal, and you can't buy it at a chemist, but it's unforgettable.
Danuri is Korea’s first lunar satellite! It wasn’t originally planned to do these harder, efficient orbit maneuvers but they kept adding new equipments and sensors to the satellite to a point where they had no options but to take the harder approach. Crazy considering that this is our first spacecraft to the moon. Anyways, huge thanks to Scott for covering space launches and projects from Korea in your videos!
It is a really innovative solution to get an efficient orbital trajectory. Hopefully it will inspire others to get low-cost scientific payloads to the Moon.
> kept adding new eqpts and sensors to the satellite
scope creep is a hell of a drug
And here is another Korean subscriber same as me lol
Thanks for additional information!
It's kinda crazy that only 50 meters of dV is enough to go past Moon to the edge of Earth's sphere of influence.
That's gravity wells for ya
It's only enough if you do it close to the earth, when you're going fastest. Escaping a gravity well costs energy, but your fuel budget is change in velocity, with how rockets work. Since energy is proportional to the square of velocity, changing velocity when you're going fast is a much bigger difference than when you are going slowly (it's called the Oberth effect).
Thinking of the Lagrange points as low effective potential "portals" between Hill spheres is an amazing insight. Thanks for sharing it. I've seen (and derived) the effective potential contour maps many, many times in my life, but never thought of the implications in quite this way. It certainly makes the captures, whether planned or accidental, so much more intuitive.
Awesome stuff, n-body physics interactions are fascinating. Have you heard of the Interplanetary Transport Network? It's the concept that all these chaotic interactions create 'pathways' between the Lagrange points of pretty much every body in the solar system. From the Moon to Jupiter, without a single drop of fuel. You'll just need a LOT of patience. (for everything to line up, and for all the natural gravity assists...)
I think there technically is a little fuel requirement, to get the initial kick from Lagrange to the path you actually want instead of staying at the Lagrange point.
And I guess a bit to compensate for inaccuracies, but eh, details.
I think the need for patience is a problem with it, unfortunately humans get old and die, and hardware goes obsolete so its not like we can wait 50years for something to navigate it way out to Neptune riding this network just to save on fuel. (Although it may be useful within a planetary system like Jupiter or Saturn where the travel distance is much smaller so the timeframe is reduced to something much more tollerable)
The "interplanetary highway" concept is awesome, I'm pretty lucky to have gotten the opportunity to learn underneath faculty who has contributed immensely to it. So with that I have to plug his youtube channel - th-cam.com/channels/9ZvnHwvAR4XkjKzKxhYDDg.html
He's mentioned it before. Nothing in depth that I'm aware of, just as a concept.
Maybe someday, this way, one will be able to finally lend Venus a moonlet
Did my PhD on ballistic capture, worked with Ed Belbruno at Princeton University, and I'm currently an active researcher on this topic. Yet, I'm always fascinated by this concept as the first days I started studying it.
Your email address please
and still find the lunar transfer chart very phallic
I really need to try one of these with the Principia mod one of these days. Amazing stuff and the 3D diagram of gravity around the lagrange points really makes everything click into place.
principia has a 3d diagram of gravity?
@@clayel1 I don't think it does, but I feel like it definitely should! (In a limited capacity, so as not to melt players' machines)
@@Archgeek0 Thats actually a planned feature, funnily enough, simplifying the gravity diagram is where they are stuck right now from what i can gather.
Not because the PC cant render it, but because the player cant get use out of a diagram too complicated
@@clayel1 Oh no, sorry, I meant the diagrams in the video make it click into place for me.
I remember reading about Bellbruno's work a little over a decade ago. I hunted him down online and emailed him to ask if it was possible to recreate this kind of orbit on the space flight simulator called Orbiter. He actually wrote me back with all kinds of diagrams and explanations. I still haven't been able to totally recreate it on Orbiter but your video helps out a lot. Thanks.
I never thought of using Universe Sandbox to reverse engineer orbits like that. Now I have something new to play with. Thanks, Scott.
I also am quite surprised that these techniques were developed only very recently.
I'd be really interested to hear much mass (as a percentage of the spacecraft's mass) these maneuvers save the craft's designers. Seems like it has to be substantial for the time and effort they spend to perform it successfully! The calculation and risk assessment that must go into it is mind-boggling.
I don't believe these low delta-v trajectories should EVER be considered for manned space flight. Exposing astronauts to the stresses of Earth-Lunar transit for an additional 3 days, round trip, is unconscionable. It's not like they're taking extra payload.. they're not even taking a lander, FFS!
You’d be interested in the delta V difference
@@sil8127 I'm guessing he wants the mass cost of that delta-v for those real spacecraft with their real technical limitations.
@@johndododoe1411 well that depends a lot on other factors, like the dry mass, the thruster specific impulse, etc. It's easier to use the delta-v savings as a yardstick, then go from there. For instance, spacecraft propellant mass is directly proportional to dry mass. So a 1 ton dry mass craft might save a thousand times more propellant mass than a 1 kilogram dry mass spacecraft given the same delta-v savings
This one is pretty easy to make a vague guess. Scott said the apogee rise to the moon is 2800 d/v, plus 50 for the high orbit. And then you save most of the insertion burn. According to google, thats 600-700 d/v for an isertion burn you mostly save.
Which doesnt sound like much, but considering rocket size (and cost) rises exponentially compared to range, its probably worth it.
I dont think the risk and calculation is a big deal tho. Someone figured out the math, made the tools and software. From then onwards you get easy, accurate numbers in comparably little time. Just a guy trying numbers in a compture, then doubly check the course. If your spacecraft can do an accurate lunar insertion, then it can probably do this maneuver already, its just a longer mission.
I've struggled to visualize how bodies are captured into orbits without delta-V. Now it's crystal clear. Thank you.
I know someone who worked on the Lunar Flashlight mission, learning more about it is so cool :O
Kudos to your acknowledgment of Ed Bellbruno and his contribution to object deployment in the space environment.
I think if you did a video on coordinate transformations, you'd have enough material to just teach a university orbital mechanics course. Certainly better than the one I got...
honestly yes, I've certainly learned more about orbital mechanics from Scott than from the one or two lectures about it that we had in our space technology courses...
Great stuff Scott. I love your deep-dives in orbital mechanics.
My favorite line "Did any of you find this overly complicated? Don't worry it's much more complex in real life" 😂
Awesome video. Love the casual solving of a 4-body problem by 2 x 3-bidy problems!
I thought that was really interesting too. Sort of like breaking a normal physics problem into multiple vectors, then adding them up, except in 3D and with exponential relationships LOL
That's not a 4 or even 3 body problem tho? The mass of the spacecraft is negligible and the Sun - Mun interactions are not the focus of it. It's 1 body (which is the spacecraft) and a field of different forces.
I took a class this last semester that focused entirely on finding periodic and quasi-periodic orbits and orbital transfers in the circular restricted 3 body problem, as well as extending these results to find solutions in ephemeris models. Fascinating stuff and really cool to see it used in real life!!
Seeing that capture tube extend all the way out from the moon was so cool!! It really helped tie the concept together in my head as well. ❤
Who would've thunk that rocket science was this complex
That is amazing. Thank you Ed Belbruno for discovering these orbits. Genius!
THIS is why all the JPL scientists have to be locked up every night! 🤭
Every time I read or hear somebody proposing that a planet "captured" a passing body and made it a moon, I think of the delicate - and extremely unlikely - orbital mechanics required to make that possible. You'd need some sort of decelerating collision, at just the right time and place, to act as an "insertion burn". (Anybody think that tidal forces could enable the process, given enough time?)
Interesting thought on tidal forces.
This is so high level, big respect Mr. Manley!
Nice video, but you got a few things wrong.
0:19 Hakuto-R is a landing demonstration programme. The lander is simply called Series 1. The rover is Rashid and is a payload here.
12:00 Hiten is MUSES-A yes, but the smaller satellite is Hagoromo. It's not actually known if Hagoromo made it into orbit because the antennae failed and they were unable to verify its orbit :(. MUSES-B is a radio telescope satellite, not a part of the Hiten mission.
Great stuff. I heave a sigh of relief over straightforward mechanical explanations. This is a perfect public level of science. Well done!
At a high level this makes sense. At a detail level of actual calculations it's a nightmare of instabilities and corrections and changing coordinates between earth, moon and sun.
Glad someone else is doing the number crunching.
Modern computers can do the hard work of navigating for such a complicated flight.
0:30 What a very sturdy-looking orbit.
I don't think a grade 7 pupil could (/would) have done better (/differently.)
I was wondering how far I would have to scroll to find the first comment about it
Very sturdy indeed...
Good to know I wasn't the only one 🤣
Real Civil Engineer would be very proud.
Rock hard orbit
That is absolutely wild. Blew my mind. The illustrations really do it justice. Thanks for documenting this!
To really understand this stuff you need to have some background iin KAM theory (Kolmogorov- Arnold-Moser ) in the context of dynamical systems. Helmut Hofer has done some good Princeton IAS videos on the technical issues in the context of explaining what Ed Belbruno did with the Hiten probe and the concept of ballistic capture. Ed was one of Jurgen Moser's students. Dynamical system stuff is pretty deep - according to Helmut when Ed came up with his idea of saving Hiten many of his colleagues said he was nuts but his ideas worked.
I got to see Scott. I always look forward to watching your videos. Awesome stuff. Thanks for all your time and energy. Excellent job.
This is a great example on how to do terrific outreach, kudos to Scott. I am a PhD Candidate at Politecnico di Milano, Italy, and at the Deep-space Astrodynamics Research and Technology (DART) group we are currently researching on how to engineer the ballistic capture mechanism for autonomous interplanetary CubeSats with limited onboard resources. We have released in open access on Zenodo a dataset of initial conditions granting temporary capture at Mars in case you are interested!
The way I think about it is basically a bi-elliptic transfer from LEO to the moon's orbit, but using the Sun's gravity to perform the velocity change at apogee.
Thanks for the lowdown, Scott! Hello from Vandenberg Space Force Base!
Orbital Mechanics has become much more complex (and cooler) than what I studied in the 1980s!
As I watched the video, I wondered if you would get around to giving Ed Belbruno the credit he deserves. I was the Lunar GAS system engineer, Kerry Nock was the project leader, so I saw genius at work. Ed explained the math to me in the hall at JPL. I am still in awe.
I've been curious about this for my entire life. I never thought it was something I could understand. Thank you so much Scott! You are an amazing teacher.
Using L1 & L2, LaGrange Points for a Ballistic slowdown into lunar orbit is a neat idea. 🚀🌙
Better idea: Build a lunar roadhouse vacation space-station orbiting earth between the moon at the L1 point, then change the rules for the pool area.
Wow, Scott, I’ve always had a trouble getting my head around body influences, until you explained langrange points like a topological map and it blew my mind, thank you so much.
well done. tracking these satellites has required an upscaling of my orbital dynamics and this is a great discussion/explanation
hope the flying is going well. RGO
Wow... just as I feel I am starting to make my way up the second mountain, Scott Manley firmly puts me back onto the first mountain of the Dunning-Kruger peaks.
Thank you for teaching us these awesome things!
I saw many Apollo lunar landing profiles like the one at 0:43 drawn on walls in many cities. Never knew taggers are such space fans.
KSP fans everywhere!
Scott, excellent work!
Very informative for me personally!!
Some i's dotted, some t's crossed, so thank you!! 👌 🚀
Fly safe!! 🙏
Great video! Love this kind of content. Very informative and not too computation-intensive!
This stuff is so cool!
It's become perhaps my favorite area of space/science.
Thank you Scott, we are all lucky you know this so well.
Fly safe!
This video contains some of the best illustrations and explanations of Lagrange points and orbital mechanics that I’ve ever encountered. Thanks!
Fabulous video and explanation! Loved it! Thank you
Edward Belbruno
Bravo, Scott! One of your best explanations.
Somehow the video title gave me "The 10 Best Lunar Transfer Orbits and Number 8 Might Surprise You" vibes 😄
This was brilliantly explained! TYSM!
Thank you for this video. I have been wanting to better understand how the vehicles get into orbits and transfer to other orbits since the Artemis 1 mission.
How timely! I started learning in ernest about Lagrange, yesterday. This is a fantastic example! Fly safe. :)
Amazeballs video mate. I learned a new level in my education on orbital mechanics. So cool.
That is realy well explained. Thank you kind Sir
Fabulous work, really clear. 😊
Nothing like a fantastic orbital trajectory vid. Awesome, thank u sir!
Excellent video! I wondered about the Artemis mission timeline from the moment I first saw it published - since I remember hearing about Sputnik, and remember watching Vanguard 1 fall back and explode on the pad, am an Apollo junkie, and have been in the space game ever since. My very favorite book of any genre is Richard Battin's "An Introduction to the Methods and Mathematics of Astrodynamics", and despite its deep mathematical insights, it contains nothing of this sophistication. Thank you so much for this one, Mr. Manley!
Very understandable explanation, thank you, Scott!
So good! Thanks for explaining this beyond-Kerbal idea with such detail and diagrams. Drinking wine at conferences paid off, surely this justifies a bit more?
Once clearly explained like this, surfing on gravitational forces seems pretty intuitive.
I hope KSP2 will have some kind of n-body simulation. That would be so much fun to improvise a last resort trajectory around a L point to prevent Jeb being slingshoted towards the sun.
Er.
I mean.... that would be so much intellectual satisfaction to carefully plan in advance complex missions using such gravitational tricks. Of course.
LOL!
I don't remember any explanation this intuitive, ever!👍👍👍
Love this type of vid from Scott!!! xxx
I listened to everything that you said. all very interesting.
I am writing to commend you for your interest and understanding of all things space and for helping us mere mortals grasp the details.
Great explanation of a complicated subject!
Wow, well done. You answered my question! Great video.
Universe Sandbox is really amazing!
Great video!
Awesome explanation, thank you Scott!
Brilliant explanation. Thanks so much.
That was good Scott, comprehendible~
It’s honestly amazing that at 26 I basically grew up in a world where n-body simulations are trivial. I know about this stuff, but every time I hear about more of the specifics of how this stuff actually works the more it’s incredible anybody not only solved 3+ body problems by hand, but that we figured out how to make computers solve them for us. The more you learn about engineering the more you realize how insanely unbelievably useful computers have been for science. It’s not all about social media lol. The speed of computation allows brute force methods like this. You would spend a million lifetimes solving 10,000 4 body problems by hand, but nasa supercomputers can back date probably a million possibilities in a reasonable amount of time and we have these orbits that basically just would be incomprehensible without computers. We have the knowledge to understand the process without computers, we just don’t have the power to calculate that fast as humans.
This was one of the most interesting videos about space exploration i've seen!
This is brilliant Scott thanks.
I learned quite a bit from this video. Thank you for all this.
Taking advantage of the highly-complex locations where a minute bit of thrust can produce massive differences in trajectory. Simply brilliant.
Thank you, Scott!
SUPER, frist time I’ve had a explanation that made sense. Nice job.
i dont want to take anything away from this very great video explaining the complexity and challenges one takes to get to the moon... but that damn first picture.... XD
Thanks for talking about this!
Very good explanatory video. Thank you.
Thank you very much for this explanation!
the amount of computation required for these lovely dances still blows my mind
and the amount of wacky imagination required to conceive these orbits blows my mind out past pluto
This was awesome! I don't think I could do the math, but you explained it perfectly.
I was disappointed that Scott didn't point out how the "primary" body changed back to Earth for a moment during the final capture. This math is crazy, but with a wonderful result. I'm sure there's a bit of chaos function in the math for those orbits, so tracing it backwards like that probably is the best way to solve it.
I noticed! It was fascinating to see the orbit change and then flip and all that.
I could never understand how a planet can capture a body and turn it into a moon - if they're arriving they are necessarily in a hyperbolic trajectory (forwards and backward being the same) and should simply fly off. Finally I can see how a capture can happen, especially with the saddle visualisations. Thanks!
I still don't know how two galaxies can merge, again hyperbolic trajectories, but maybe that's a future video? :P
It's not quite that simple though, because as Scott pointed out, it's reversible - if you can be captured this way without spending energy, you can also be ejected again the same way... which is why these craft are still using a regular injection burn to stabilise their orbit.
Very informative.. thank you.
Would've been nice to hear about this in any of my orbits or GNC classes. Lol. Though maybe I got through before this was much known. Welp. That's why I follow people like you Scott.
Love this one. Almost makes me want to play around with this stuff. I do have a question which might also be an idea for one of your videos. With all the variables involved, I imagine that various trajectory adjustments (aka burns) have to be calculated just before they are done in order to deal with actual velocity rather than those calculated before launch. This must especially be the case with these critical paths near Lagrange points. How sensitive are they? How precise do the pointing and burn times have to be? I imagine some missions fail because they get this wrong and fall outside the envelope in which adjustments can be made.
Haven’t worked as an astrodynamicist specifically, but have worked in spacecraft GN&C design. In general, orbital trajectories are VERY sensitive, and trajectories designed using this method even more so. Even a difference of 5ms of burn (so a second or two of firing) can cause huge differences when propagated for a long time. Nowadays, though, we’re pretty good at navigating these missions, even with the almost unimaginable precision required. The key is that adjustments are constantly made throughout the journey, not just before burns. Hopefully, you never arrive at a burn at a velocity far different than what you expected, because you corrected it at 1 m/s off rather than waiting until 50 m/s off.
Thanks! That was fascinating.
this is really cool
I had the opportunity to make a thesis related to this
I could get to know a little about the work of belbruno and Ross (the green red images you showed)
great job
You really are so good at distilling down complex concepts and serving them up in easily digested bites of information.
In other words, you dumb it down real good so that even dodos like me can follow the plot. Kudos!
No, seriously, this was a really good video. Make more!
Amazing explanation
In a computational physics undergrad course over 25 years ago, we had an assignment to fire a spaceship from Earth, have it orbit around the moon, and return safely to the earth. If I recall correctly we implemented the Runge-Kutta method which took the 3 body problem and had variable time steps to give the most accurate simulation.
I took the assignment way too far, and graphed out the entire space. Given a starting angle (x-axis) and initial velocity (y-axis) what happened to the spacecraft? Impacted the moon? Lost in deep space? Skipped off the earth and ejected? The graph was not simple.
I recall one set of initial parameters had a free return trajectory that ridiculously skirted the moon's surface by about 1.5mm, then returned safely to earth.
All of this to say that your video has me really curious. All kinds of "bank shots" off those Lagrange points (L1 and L2, both sun and moon) could lead to some fascinating paths with minimal fuel. Would love to see more on this topic. (even if just a recommendation for other videos)
Brilliant talk thanks Scott
Beautiful stuff clearly explained, as usual. I remember viewing your material about distant retrograde orbits some time ago. Are there two distinct cases for DROs and for what you present in this video? Does it make sense to compare them? What are the pros and cons of each one?
Really exciting stuff!
I heard Scott say "this orbit is perfectly balanced..." and now I'm just imagining a certain TH-camr at NASA talking about how the orbit is perfectly balanced with no exploits...
Joking aside, really interesting and as always, your breaking down complex orbital mechanics into layman's guide is appreciated!
Excellent guide to how to get to lunar orbit on the cheap. A nice follow up would be how to do it all in 3 days as with the Saturn V.
Power makes it good.
Thank you for educating me.
Phew, blew my mind too.
But I get the general idea.
Ingenious.
More like this please Scott!