What Is Distant Retrograde Orbit, And Why Is Artemis 1 Using It?
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- Опубликовано: 11 окт 2024
- Artemis I flew beyond the Moon into a Distant Retrograde orbit, this is a special orbit which appears to orbit the moon backwards at a distance beyond the moon's lagrange points. The orbit requires low delta-V to reach and is stable over long periods, however, it regularly passes through regions where the Moon eclipses the Sun or the Earth, which is why NRHO is preferred for the Lunar Gateway.
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There's some great technical details in this paper
ntrs.nasa.gov/...
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A square orbit. Now I've seen everything! Thanks for explaining.
Really? Have you seen a man eat his own head?
@@mrflippant you make a fair point
Now I wonder - can there be triangular, pentagonal, hexagonal, ... orbits?
@cybhunter007 Reuleaux.
@@nkronert : Find the right viewpoint, and the Earth-Moon system can provide all of them.
Really nice explanation. Reminds us that orbital mechanics involving multiple bodies starts to get really complicated really quickly, esp. when you factor in other key constraints like solar panel illumination and non-LOS-comms. Nicely done.
Orbital mechanics get almost impossible with more than 2 bodies.
The only time you can actually do the math for more than 2 bodies, is if one of the bodies is very tiny, like a spaceship compared to a moon, for example.
If you've got 3 moona, planets, etc then the orbital mechanics are impossible to work out.
@@lordgarion514it's not impossible in a practical sense, but impossible in a theoretical sense in that it's always going to be an approximation with some amount of error. there is a taylor series approximation to the newtonian three body problem which takes some hefty computational power if i remember correctly, as it converges slowly.
@@kadenze6176
From what I've read, what you're talking about is 3 bodies with exactly the same mass, and in a very specific orbit, that they chose.
While I hadn't heard of even that being done, it doesn't really help us do anything.
You can do 40000 bodies in universe sandbox 100% accuracy
@@AstronomerKSP When there are no closed-form solutions, computational errors accumulate, unfortunately.
My jaw dropped at that square orbit. Thats amazing.
There's all kinds of crazy shapes the apparent path of a third body can make when under the influence of two or more bodies, and as you saw it changes wildly depending on which frame of reference you use.
The "rectilinear" in NRHO also stands for an orbit that's sorta rectangular. (My jaw dropped when watching the earlier video from Scott about NRHO)
Rosetta did some triangular orbiting around the comet it visited, though that was (IIRC) done by thrusting at each corner of the orbit. (It takes a lot less impulse to do things like that around such a light body.)
@@IDoNotLikeHandlesOnYT Brute force. I love it.
An amazing episode. The visuals provided a whole new context for the awe inspiring majesty of moon landings, and for just a moment I was a small boy watching those brave astronauts on Dad’s b/w TV. Today’s world exceeds my wildest boyhood dreams and every episode of your show expands my universe. Thank you.
Scott, your videos are amazing. I have a family member who is an engineer. He previously worked COTS, then on developing Gateway, and now he is leading a team devolving infrastructure to maintain a permanent station on the moon. He's way, way smarter than I. If it wasn't for your videos, I would be absolutely clueless every time he talks about his job.
Some times, I say something to him that prompts a raised eyebrow and the question, "How the...[heck].. do YOU know that?" My response is always, "Tim Dodd told me," or "Scott Manley told me."
90% (or more... most definitely most likely more) of the stuff I know about space and orbital mechanics comes from Scott Manley or KSP... or Scott Manley videos of KSP.
The words "Three Bodies Problem" filled me with existential dread. The trisolarians are coming.
Damn…how was it?
@Karma Mechanic How is that a "problem"?
It should fill anyone with dread, regardless of whether they are sci-fi aware.
In the physics community, the "two-body problem" refers to trying to coördinate the next steps in one's life (such as grad school attendance) with a significant other.
@@HiddenWindshieldStamina
Scott, very clear explanation and excellent graphics - that is why the community loves you! Eamon
Love the time-lapse!!!! Thank you.
I have to admit I was feeling pretty hopeless in my comprehension until you put it into Sandbox, and then Bingo, it made sense! I guess I'm just more of a visual learner - thanks Scott!👍
Wow why has noone else properly explained this? Amazing work again Scot.
I imagine they figure, "why bother?" It doesn't involve the Kardashians and people are still not quite sure the Earth isn't flat.
Cuz noone else is Scott Manley XD
Keep going. I appreciate the humor in your sharing things that give my brain a little twist.
I love that all these new missions are planned, I just wish the time scale wasn't so long. Basically I am selfish and want to see them in my lifetime!
The planned missions are scheduled to occur over the next 10 years or so, so you might well live to see them assuming that you're not gravely ill already. My condolences if you are.
After that, we may well have a permanent presence on the Moon and in lunar orbit. I expect to live to see a lot of progress but I genuinely hope that it outlives me.
To calculate this by hand must be outrageously difficult, but I guess somebody had to.
Give that man a medal, he deserves it.
Scott, you explain these things so eloquently and with great visualizations.
The best part of all of this is that Scott Manley put the Hubble Space Telescope into Distant Retrograde Orbit.
Uninitiated viewers must've been very confused at that point.
@@u1zha Indeed.
Scott, this is one of the best videos I've ever watched. In any category.
Thank you, Scott. What a great demonstration of what these difference orbits mean and do.
Nice job explaining and visualizing DRO, Scott! Thanks for all you do.
A square orbit around the moon, well I'll be! I have to say, I was one of the doubters/haters of Artemis but since the launch and seeing all this stuff lately I've gotten pretty excited about it. The odd orbital mechanics is super cool. And so, by the way, is seeing that NASA worm logo out in deep space looking back at Terra and Luna.
I was wondering about NRHO: it's about the lunar poles! (and LOS). really nice orbital demo and explanation! Orbit safe!
The Gateway orbit is just insane. In order to make it easier to arrive and leave within certain windows, they're making an immediate abort to the station impossible unless they have the delta V to catch up, or it just happens to be that few hours orbital window when Gateway is passing over. And abort from the surface directly to earth obviously isn't possible.
The Gateway orbit is just an impossible delta V to make it easier to arrive and abort from the surface
Neither could Apollo. The ascent module had to dock with the CSM, that was out of communication with both the earth and the LEM half the time it was in lunar orbit.
@@SRFriso94 Apollo did it twice so no idea what you are thinking maybe the CSM was out of communication with the LEM and half the time it was docked with the earth
They want to keep Lunar Gateway in orbit around the Moon for years, so the NRHO is what they are using, since they will need little propellant to stay in orbit. HLS Starship has the excess propellant for a wide range of abort scenarios according to NASA.
@@steveaustin2686 No they want to land on the moon after testing and return without propellant
I've been hoping for a video breaking down this DRO orbit. Thanks for your knowledge Scott.
Great explanation for this relatively non mathematical space nut (me). Strap line: it’s a stable orbit that doesn’t take much propellant and is de-risked coz they can get Artemis back if something goes wrong. It kinda puts the huge risks of Apollo into perspective.
It’s been a long time coming but I have to admit, SLS and Artemis are pretty darn awesome.
(I honestly thought it was going to explode on the pad… but wow, it’s really delivering… just wish it wasn’t so costly)
Can you just imagine what SLS could do if it were reusable? SpaceX reusable, not Shuttle "reusable". The cost would be stupid cheap compared to one time use and would make so many more missions possible, like catching that asteroid and bringing it back, THAT would have been amazing!
@@LIVE3DPrinting
Nah. Reusability significantly reduces LEO payload, which cuts deeply into payload to anywhere else. There's a reason Starship won't be able to go past LEO in a single launch. And no, it wouldn't be that much cheaper, refurbishment costs a crap ton. It would probably be more expensive overall when you take into account the enormous extra costs of developing reusability in the first place. In terms of dollars per kilogram to LEO, an expended Falcon 9 is about the same price as a recovered Falcon 9. The real benefit of reusability is to increase launch cadence, which drives down cost over time. But with a vehicle intended to launch dozens of tons to the Moon, launch cadence is going to be low no matter what.
This is what it costs. Starship, has already cost 5 billion in tax dollars, and lord only knows what Elmo spent on the carbon fiber version before settling on stainless steel trashcans. IF, and that's a very big IF, it ever becomes a crew rated vehicle, I guarantee it will be far more expensive than SLS.
@@LIVE3DPrintingYeah… People not in industry really overestimate the savings from reusing. Artemis is already planned to reuse the Orion capsules, but for such a large payload and long distance, it’s not worth it to recover the booster.
Incredible!! Thank you Scott.👍
The pic in the thumbnail is one of my new favorites. Been using it on my phones home screen
Nerd alert
Yet another great explanation! Thanks for all you do, Scott! ❤️❤️
Thanks for the great explanation! It's so easy to forget that EVERYTHING in space is in motion and when considering the Orion's trajectory, we need to take the moon's orbit around the Earth into account too.
I'm surprised how honest and frank you're.
That is brilliant, and quite elegant. From the surface of the Moon it must look like it's dancing among the stars.
It’s been quite frustrating not to have a good conceptual explanation of Artemis-1’s orbital maneuvers the way we got that back in the day withApollo (yes, I’m old enough to have clear memories of that), but I think I now have one (sort of), The DRO is simply a prograde orbit around the Earth that - due to the Moon’s influence on the orbit - is significantly more elliptical than is the Moon’s orbit around the Earth and is in the same plane as the Moon’s orbit around the Earth. The ends of the major axis of Artemis’s orbit lie farther away from Earth than the Moon’s orbit, and the ends of the minor axis of Artemis’s orbit lie closer to Earth than the Moon’s orbit. When Artemis is in the farther part of the orbit it orbits around the Earth slower than the Moon and “falls behind” the Moon. When Artemis in the nearer part of the orbit it orbits around the Earth faster than the Moon and thus “catches up and passes” the Moon. Viewed from the Moon this would look like a retrograde orbit around the Moon at a great distance (if the distance wasn’t large, the Moon’s gravity would dominate and Artemis would orbit around it rather than around the Earth). The Outbound Powered Flyby and Return Powered Flyby are just lunar gravity assists - helped along by Artemis OMS burns - to get Artemis on its way to DRO and get it on its way back to Earth. What I would like to know is if the Outbound Powered Flyby and Return Powered Flyby burns are retrograde or prograde burns, and the same for the DRO insertion and DRO departure burns (I assume the DRO departure at least must be a retrograde burn).
The departure will undoubtedly be a retrograde burn. And if I understand it correctly the entry into lunar 'orbit' will be a prograde burn to circularize its orbit.*
_*That is, with respect its orbit around the Earth and not literally circular!_
Pretty interesting indeed! Thanks, Scott! 😊
Stay safe there with your family! 🖖😊
It's wired how much I learned from ksp. Thanks Scott
It's already such a joy to hear how you say "the mün", but "I'm gonna züm in on the mün" is the best thing ever.
thanks for your content ❤
You are welcome
Fantastic explanation of the orbits!
I would have never thought the square orbit could happen, but orbital resonance has eluded me so far.
I did, many many years ago, get a rotating triangle lissajous pattern once inserting Beatles music unto the x and y drivers of an old T.V. once (just before I shocked the living shizzle out of myself.)
Always love your videos.
I'd be interested in a short video where you go through the back of the envelope calculation for the universe sandbox simulation.
You sir are a student and a scholar. I’m a little slow. If you knew how important you are to me. Thank you. I am a aviation nerd. You make space approachable for me. Thank you again.
I don't think you should approach space in a plane....
@@arjensmit6684 Well if your plane happens to be an X-15... Or a Dreamchaser.
I hope you'll put the Hubble Space Telescope back once you've finished with it.
LOL!
0:22 This shot is so much like that famous stage separation from the Apollo era (mind you, AS-202, it was a Saturn IB, not a Saturn V)
I love those slingshot maneuvers! We might start calling the Capstone and others the Moon Moon.
I'm hoping you'll make a video covering the successes and problems/ failures of the mission. 🙂
I had imagined a DRO to be an elliptical orbit about the earth with the same semi major axis and period as the moon but with more eccentricity. So the apogee would be a distance above the moon and the perigee would be a distance below the moon. But from the moon's POV would look like a retrograde orbit since it falls behind the moon when above it and spurts ahead of the moon when beneath.
But the animation doesn't show an ellipse with earth at the focus. Looks roughly elliptical but with earth at the center. So clearly not the Keplerian orbit about the earth I had imagined.
I guess the moon plays a larger role than I had imagined with DROs.
Love the way you "spitballed" an orbit stable for 13+ years. Class.
It kept going for 400 before I shut it down.
Very interesting episode Scott! Thanks
I will have to view your sims on my desktop as I couldn’t quite make out the names on my phone!! 🤪
Take care!
Wow that square 😳 so well explained too
Every science teacher is bowing in Scott's general direction right now.
Can never get tired of Scott Manley saying "mun" 😊😊
It's pretty cool to see that now we are advanced enough in orbital navigation for these trajectories. Big advancement from the 2 body approximation and directly flying to Low Lunar Orbit that Apollo used.
It's still an approximation.
3 body problems are unsolvable except under specific situations.
The main one being if one of the 3 bodies is small enough, its gravity can basically be ignored.
@@lordgarion514 Or you can simulate it with the desired accuracy. The important part in my eyes is that we can fly these trajectories in real life now.
Thanks Scott that was very informative
I hope we still do the asteroid capture at some point.
Right, we're gonna be at moon, might as well bring a rock nearby to check out. Then if 1 trip isn't enough we can go more cause it's right there. Pretty sure a core sample from a pristine asteroid would provide a wealth of information for years.
@@JJayzX Get two or three asteroids of various types.
Well done for finding an almost square orbit. I think I'd call that one a 'toast orbit' because its shape resembled a slice of bread more than a square, with some concave sides and one convex one like the top of the toast that doesn't get toasted if the bread is too tall for the toaster.
It was great to see an eclipse of the Earth from Artemis as well - not quite the same size though. I wonder has any probe/satellite managed to film the moon eclipsing the Earth when they are exactly the same size? Or has one at or near the Earth's L2 point found the point where the Earth can eclipse the sun appearing the same size? It must happen somewhere.
I propose this will hereafter be called "The 'Scott Manley orbit' in dedication to the person who first visualized it plain and clear way for everyone to understand easily".
Thanks Scott. I'm not sure if this mission is worth $2 billion dollars, but there you are...
I do want to see a new Moon landing though.
It's better than no mission at all. lmao
Yes, it’s unfortunate we’ve had to spend billions to re-invent the wheel, but that’s because of politicians’ decisions a half century ago.
Keep in mind that money doesn't disappear when it's spent. It flows back into the economy. Thousands of engineers will spend their wages on countless goods and services, most of it within the US where it was originally gathered in taxes, and it's probably less than 1% of the federal budget (NASA's entire annual budget is less than 2% of it).
It's good to spend money on scientific advancement and international collaboration. Contrast that with more than 10% of the federal budget being spent on the military.
Humans are oddballs!
@@nagualdesign Well. If US doesn't spend that money on defense. The chinese and his friends will not hesitate to do chinese and friends things... like... invading countries.
The chinese government is a threat, along with all their friends.
@@nagualdesign
Yes, the money goes into the economy, and even more. For every dollar we spend on NASA, the economy gets about a $10 boost.
But that's because NASA does amazing shit. Just look up "NASA spin-offs".
But this is just Congress giving money to their rich friends.
I see no reason why this money would have the same economic benefits.
And as much as I'll agree with you on spending too much on the military, the benefits to the world are enormous.
As violent as people think things are now, things are a LOT less violent than in the past.
Small fights will always happen, but being big enough that big wars don't happen, is better for the world, AND America's economy.
Spending more on NASA would be a good thing, if we could stop Congress from just literally giving our money away to their friends.
Thank you. Was hoping you would do a video on this topic.
"Distant Retrograde Orbit" is what we use to describe the short christmas visits from the in-laws
Great podcast, thank you! Keep 'em coming!
Why don’t they place additional craft in standby orbits and a lander at the landing site prior to sending humans? Giving them redundant equipment and supplies for emergency or even regular use.
Those were very cool CGI orbital mechanics. The real deal too.
Keep up the good work bro.
Brilliant video, Scott
If you'd asked me 15min if a square orbit was possible, I'd have laughed in your face. But now... 3 body problems are weird. Considering the long orbit and the relatively short mission duration, how many times is Artemis actually going around the moon? That is, w.r.t. the moon, how many loops does it to around it? I've got the picture that it's only ~1.5 in total but I'm really not sure.
From what I've seen in the tracking 1.5 seems about right
Less than one actual DRO “orbit.”
The orbit is only "square" because of perspective. It's like how when Saturn is in retrograde from the earth's perspective. It looks like Saturn is temporarily going backwards. Of course Saturn is not really going backwards around the sun.
@@DemPilafian Well yeah, but everything looks like it does because of perspective! Even a regular circular orbit around the moon wouldn't look like a circle if viewed from the sun's reference frame. But viewing an orbit of the moon from the moon's reference frame is the obvious, natural choice.
@@robertbutsch1802 so something like 1/4 orbits on lunar approach/departure, and a bit less that 1 between the two burns at closest lunar perigee?
@scottmanley, do you think you can see Artemis I's re-entry from the CA coast? Or how far inland do you think one can see it from?
No he doesn't and I have nothing better to do
This will be used for other planets, moons and satellites as well !
every now and then, scott puts out a video where i go, "wtf?"
this is one of those videos
NGL, that orbit at 2:00 looks like what mine would when i've messed up a mun transfer and am now trying to catch back up lol.
I can’t imagine throwing astronauts into this thing on the first launch. Wouldn’t be prudent.
That's why they didn't. The shuttle was the last time time the put people on a first flight.
They didn’t lol.
Fascinating and mind boggling. But to put it in perspective, the averGE 1990 Hyundai had more computer power than the first lunar lander. Much of the Apollo Mission was done on a slide rule.
I really enjoyed this!
Thought arising by watching, (unrelated to the topic) "Could quantum computing give better access to working the three body problem?".
Oh I see you've been stepping up the thumbnail game :D
Great explanation thank you!!
Scott, the go to guy to explain this stuff to regular people
Thanks for the nice conspectus of this flight profile. It's odd, but Artemis is an odd program for odd times.
Although fairly controversial, the advantage of Artemis is all the cheese from mining the Moon.
Excellent presentation. Thanks Scott.
Here's a few more words for the RUclips algorithm 😁
RUclips is nothing more than Google.
Google is the AI champ.
I can assure you when you said algorithm, Google ignored your comment....
@@lordgarion514 dang
Wait, I want to be absolutely clear about this: If you could view Artemis 1 from high above the moon continuously without any obstructions, such that the movements of Artemis and the Moon seem like a 2D motion-picture - it would seem like Artemis is orbiting in a square-like orbit?
I believe he had the moon centered at the origin of the coordinate system for the square orbit to appear. There would be no movement of the moon.
omg this cut at 4:16. Im blind now Scott, thanks!!! LUL
Blinded by science!!!!
"I have a magic number I have calculated using the latest envelope and pen technology." LOVE IT!
A square 'orbit.' Absolutely fascinating!!!
Yes, but NRHO also is square-ish. You late to the game! Catch up with Scott's earlier videos! :P
How does Artemis calculate its speed in relation to Earth/Moon in order make the proper adjustments to insert itself into the correct orbit around the Moon?
Seeing that squarish tail is truly amazing
I’m more interested in what the test dummies registered in regards to radiation exposure, considering that 27 men already went around the moon during the Apollo missions and all survived.
Missions Apollo 8, 10 , 11, 12, 13, 14, 15, 16, 17 all went out of our exosphere and around the moon .
Why test dummies now when these brave men were the first test subjects to go.
Please explain.
Because they’re specifically testing a wearable vest to reduce radiation doses to the torso. www.nasa.gov/feature/orion-passengers-on-artemis-i-to-test-radiation-vest-for-deep-space-missions
Apollo crew carried simple dosimeters using photographic film, scientists wanted more complex measurements.
Good question. I’ll watch this tomorrow but then I already done this around mun
Been looking forward to this video.
You're a natural teacher
That's a actually a squircle, not a square, and mathematically the formula is the same as for an regular old ellipse--but to the 4th power. Food for thought.
My father used that equation to design placemats.
Distant Retrograde Orbit sounds cool and all, but I propose we call this the Wonderbread orbit
This was incredibly helpful!
Hey Scott you rock! I saw the clip of the abort tower pulling away and that got me thinking. The abort tower does not pull straight ahead of the vehicle but off to the side in the clip seen here. My question is, does the abort tower fire differently during an abort than it does during a nominal flight? Can it control the asymmetry of the thrust to get out of the way either of the second stage in an abort or of the crew capsule in a nominal launch.
BTW I watched this with a few people in the room and most of them were looking at their phones a few minutes into the video but I was realizing that the montage of footage that you put together there was historic and unique footage of our return to the moon. Super cool even if it is way expensive. Thank you
Both when discarded and when used for real, it pulls to the side to get it out of the path of the rocket it's abandoning. That's pretty standard for escape systems, since while there's plenty of uncertainty, the one place you *know* is unsafe is staying on the same trajectory as the failing rocket.
Ejection towers almost always go perpendicular to the path of flight if I recall correctly
@@RhodokTribesman not quite perpendicular. They accelerate forward to put as much distance as possible between them and the potential explosion, but also steering to one side to get them out of the path of the rocket they're escaping.
The launch tower actually has steering, there’s a solid rocket motor with a set of valveless that open and close to direct the thrust. So it can turn sideways at the rate la required.
Also it does fire differently in an actual abort, the main abort motor is separate from (and much more powerful than) the jettison motor.
Thanks for the explanation. Where the magical speed vector (0.679 km/s) coming from? I see 0.481 km/s from the article referenced by you
.
brilliant explanation 👏👏
“Pen to envelope” 😂 My favorite way to take random notes, too!
Still struggle with orbital mechanics that doesn’t use “ker” in front of it!
Thank you for making this video, I've been wondering about this ever since the launch!
It's like nasa was watching youtube and found video about square orbits and were like WE HAVE TO DO THAT!
Excellent Reporting 👍
shout out to universe sandbox!
When on the way or returning from the Moon what is the speed referenced to?
Friends question
"For example the day or two after launch, the speed was showing as something like 70 mph, but the distance to the Moon was decreasing at most like a mile every three or four seconds."
4:16 think fast, chuckle nuts!
1:58 WTH was that Lunar Ice Cube that shot off when Artemis first encountered the moon?
Those are the pictures/video's i was waiting for. (At least please let it not be CGI again)