Why Spacecraft Are Using These Crazy Routes To The Moon - Weak Stability and Ballistic Capture.

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.

Some of the orbit visualizations use Universe Sandbox

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[MrArzorth]

I’m an orbital mechanics engineer at ESA and I wouldn’t have explained it better 👏🏼👏🏼

[duxangus]

This is mathematically and physically beautiful and I cannot imagine the happiness the original scientists felt when putting all of this together

[seunghobaik]

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!

[konstantinkh]

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.

[fratop]

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.

[Ranged]

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...)

[MartinMizner]

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.

[bprud]

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.

[I.amthatrealJuan]

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.

[williampeek]

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.

[kylenolan]

I've struggled to visualize how bodies are captured into orbits without delta-V. Now it's crystal clear. Thank you.

[cognitivefailure]

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.

[vpscttm]

Kudos to your acknowledgment of Ed Bellbruno and his contribution to object deployment in the space environment.

[MoonWeasel]

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...

[joshuahammond]

I know someone who worked on the Lunar Flashlight mission, learning more about it is so cool :O

[rpaulcelso]

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.

[jpdemer]

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?)

[AndyStarr]

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!!

[MonKeedE]

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!

[peterhall]

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.