Interstellar Docking Scene Analyzed by Engineer

[@Blackness_78]

Cooper is a test pilot , if you noticed it he’s actually pointing his head AWAY from the spin axis, resisting so he doesn’t black out, Anne on the other hand is pointing her head towards the spin axis, causing her to blackout.

[@genekim5101]

they were both pointing their head away from the spin axis. Coop was sitting on the left side of the lander so he tilted his head towards the left to compensate for the centrifugal force acting outwards from the centre of rotation/circle, whereas brand was sitting on the right side so she tilted her head towards the right to compensate. It's just that Cooper was the more experienced pilot so he could withstand more G's, compared to brand

[@vinnhansen]

@@genekim5101 wouldnt she have to turn her head to the left two? The spacecraft is spinning to the right so she actively 'goes with the flow'...?

[@DutchKoffie]

Forget about the wobble, there is an even bigger problem. The explosion happened on one side, and it looks like a significant amount of mass was lost. So the docking point on endurance which used to be placed at the center of gravity should no longer be in the center of gravity. Meaning that the docking point no no longer spinning in place, but spinning around the new center of gravity. This should further complicate docking significantly.

[@Six_slotted]

I think if you designed a ship like this there would have to be some capability to shift mass towards the centre or rim to compensate in case of a failure like this. Actually you would need it constantly reacting for general operation too just so that moving stuff around inside the ship doesn't cause off axis rotation. Maybe if you have 3 or 4 masses on linear rails at regular intervals or something. Bigger design flaw in this ship is that you wouldn't ever make it a requirement for any other vessel to dock with you that they are capable of rotation around the docking axis. You would have your docking mechanism on the station able to rotate independently to match the incoming ship.

[@jonsaboe2019]

Yes, that was my first thought when I saw the movie. It MUST rotate on its center of gravity -- and that is now nowhere near the center since that chunk is now gone. That docking port would be spinning in a tight circle around the new center of gravity -- like an off balance washing machine on spin cycle.

[@01234567891111994]

Exactly what I was thinking

[@sparkelstr2418]

@@Six_slotted I dont think they intended the endurance to explode due to some dumbass failing to dock, it could have multiple fuel tanks in to move fuel around to keep the center of gravity stable, it was also supposed to go at 5 rpm, which ships can match to dock easily, could they have made it so you dont have to match your rotation? Probably but it probably got overlooked while designing the ship, or maybe they just didnt care, this a movie where the protagonist jumps into a black hole and comes back afterall.

[@Karthikjpt]

The way to spoil Interstellar experience

[@ZulquarPlays0207]

Interstellar docking scene, was it possible? No, it was necessary.

[@willthedingo]

The thing that will ALWAYS get me in this scene, is the way Brand (Anne Hathaway's character) gives Cooper that LOOK as she's coming back into consciousness. Looking at him like he's completely inhuman, or SOMETHING at play, that he was able to successfully dock. Beyond her belief. And then the tears of joy - because if it were up to her, they'd all be dead and the mission would have failed. Really wasn't a time for caution.

[@ProfessorRoss]

I totally agree, that's why I left it in. What other emotion could Brand show after such terror other than joy and surprise? Cooper has done the impossible, and so hope remains. I think this foreshadows a lot of amazing things that humans will one day do in space, heroic and dangerous things, since it's such a harsh environment -- the harshest of all.

[@simplegarak]

Remember that earlier in the film Brand and Cooper have an argument over the fate of humanity with Brand accusing Cooper of willing to have us go extinct just to see his daughter again. At the end of this scene, Cooper has proven that he is willing to save the embryos even at the cost of the fuel he needs to go back home. Thus I think a lot of Brand's expression is also "wow, I misjudged you."

[@sunnysharma3401]

​@@simplegarakTotally approve❤

[@mcmandy086]

"If it were up to her, they'd all be dead and the mission would have failed". You do realize that the only reason the explosion happened was because Cooper chose to go to Dr. Mann's planet instead of Edmunds'? The whole disaster was basically Cooper's fault.

[@eugenefisher2965]

During the docking with the Agena test vehicle during Gemini 8 a thruster malfunction caused a rotation of over 70 RPM and Armstrong was able to cancel out the spin enough to undock, so such things have happened before.

[@ProfessorRoss]

Eugene, thank you! I didn't know about this event before. I'm going to be including it in my class from now on.

[@soisaus564]

this is such an insane story to think about

[@IgnitionSource]

This movie in many ways was a nod to science fiction as much as it was to men and women involved in NASA and events that occurred during the space program. The Agena incident was one of them. Many of the names of the astronauts as well as the robots we're also named after real astronauts. Had a lot of respect for the director, I'd heard he made a deal with Kip Thorne when he approached him on designing the special effects for the black hole. Kip used what known science and theory was available at the time to design the black hole; Nolan was asked to stay within the bounds of known science during realistic scenarios and scenes. Potential Spoilers Ahead: Obviously the at the end of the movie, Nolan was allowed to use his imagination to resolve the story. 😀

[@nickc9070]

The Smithsonian video says Armstrong undocked before canceling out spin. But this event does still show an ability to manage well under blackout spin conditions.

[@af.tatchell]

@@ProfessorRoss that incident is depicted in this scene from the movie First Man - kzbin.info/www/bejne/rIOun59me6h4nas

[@alexdi1367]

Coming from a mechE background, I couldn't imagine the docking tube would be able to withstand either the torsional or compressive force from the thrusters. They'd never have designed that sort of strength into it. As soon as he hit the retros (at least with the implied impulse from the film), the tube would have twisted right off.

[@ProfessorRoss]

That's another excellent point -- it would make an interesting exercise for students in structural dynamics related to space structures. But of course, you realize Cooper did all the calculations in his head and figured the odds are against him (or maybe it was the robots that did that), but he had to take the chance 😀

[@vindolanda6974]

yeah this was what I wanted the video to cover

[@anticom6099]

This was my thought as well. Maybe if the deceleration was much slower, or they were controlling the Endurance’s thrusters in concert with the Ranger’s, but using the Ranger’s thrusters alone to slow the Endurance down at the speed shown, it would have resulted in immediate catastrophic failure.

[@AntonLennikov]

If they would not add loss of orbit to the scene for extra emergency of the situation then they could use gyroscopes on the lander to reduce the rotation of the endurance slowly over a day without causing too much stress to the docking port. It would be quite unpleasant for the crew to survive 12-24 hours with such centrifugal forces, with such small axis of rotation lots of puke in the small craft. More realistically they could connect through docking to the ship systems and use it's own propulsion system to slow the Endurance down synchronising it with their RCS not to break the docking port.

[@SnoutyPig]

"Oh no, the science doesn't allow me to enjoy stuff. The science! The science!"

[@CityscapeMuse]

I accept that being just. An impossible situation. As a writer, I'm like "alrighty, here's how we sci-fi around these plot black holes" but realistically, I get it. I really liked that someone who is neither a physicist nor an engineer can follow what you're talking about with ease. Someone made a comment about it definitely going slower than 68 rpm. Are they still near the black hole at this point, messing with time? Are we going with a time is relative argument? Yes we are! lol. The wobble...it was a perfectly outward explosion with no "vertical" component to it *cough* final answer. Overall, I'm glad that the physics of this movie were mostly sound, and for the sake of Hans Zimmer's soundtrack, I can suspend my disbelief

[@gertsy2000]

Definitely slower than 68 RPM. Around 10 rpm based on the 3 scenes I calculated by. All of them the same.

[@chuckdawg2799]

I consider this one of the greatest scenes of any movie ever - the music definitely makes it - and the way she looks at him when she wakes up - wow. I was an AF pilot, I have often tried to guess how many g's they were hitting. he isnt in a g suit, 9gs is possible for a short bit, probably not that long no suit. 9 would really be on the high end. Also, she may not be a pilot but she is healthy, trained. so 4gs would be doable for her pretty easy. i had students GLOC at 5 to 6g - but that was mostly because of very fast pull vs a build up. so anyhow - i am guessing it would be between 5 and 7 gs.

[@ProfessorRoss]

Thanks Chuck Dawg. I think we can calculate the g's he's pulling at the beginning of the docking. The formula for the outward acceleration is a = ω²r, where ω is the angular velocity in radians per second and r is the distance from the rotation axis. When they are about to dock, they get up to 68 rpm, so converting to radians per second this is ω = 2*pi*68/60 rad/s, and from where both are sitting, let's assume r = 1 meter. So a = (2*pi*68/60 rad/s)^2*1 m = 50.7 m/s². In terms of g's (g = 9.8 m/s²), this is about 5.2 g, so your guess is very close! Now, if they pull their head slightly closer or further from the rotation axis, this number could go up or down. I'm sure it's quite disorienting. I've never been in a fighter aircraft, so the most g's I've ever pulled has probably been on roller coasters or that ride that spins and makes you slide up the wall.

[@chuckdawg2799]

@@ProfessorRoss thats the most bad ass response I've ever gotten on media

[@lohengrinknight]

Maverick and his students went to 9 G's when they bombed the nuclear facility in Top gun: Maverick. If they made it, why wouldn't Coop make it too if he had so much love to spare? lol

[@gertsy2000]

@@ProfessorRoss Yeah, but they were only doing 10 rpm, not 67-68. Trust your eyes, not the robot.

[@pavelb2051]

Soyuz T-13 executed a less-dramatic version of this maneuver when docking to Salyut-7 which was spinning out of control (but probably not at 68rpm).

[@bbsonjohn]

Also I feel like the rotational axis will be laterally offset from the docking port with the huge chunk of missing mass from the dish.

[@cyriaqueguillot1205]

Not only you help me with my current mission in programming for an ADCS, you are also a fan of Interstellar I love you 😂❤

[@ProfessorRoss]

Happy to help!

[@oliverwatson4488]

7:59 about cooper not blacking out i remember seeing somewhere that the reason he stays conscious is cause he tilts his head in opposite direction of the spin (he knows to do this cause he's an experienced pilot and whatnot). idk how realistic that is but i thought it was pretty cool

[@lsedge7280]

I'd assume the Endurance may have had a stabilisation system (though probably not sufficient to deal with the amount of wobble that thing should have had) to help counteract small effects such as the movement of astronauts around the station as well as micrometeorite impacts or any other issues that could crop up, as that'd be a risk that'd crop up with a ship meant to spin. As for the docking port no longer being in line with the centre of mass (and by extension rotation), given they're accelerating their spin to match up to the endurance they could have the acceleration be off their own centre of axis. It's worth pointing out, Cooper while doing some of the piloting and commanding, is being assisted by CASE (who I assume may have programmed a sequence of retrothruster activations to match endurance's rotation) and TARS (whose helping control and observe from the docking port), so there is some 'automated assistance' of a form. Which isn't to say it's entirely possible. As for cooper not blacking out, he's a trained test pilot unlike Brand who while a trained astronaut is first and foremost a scientist, and unlike Brand he's leaning his head out from the spin axis, while Brand is letting her head follow the spin axis, hence why in addition to her lower G tolerance she does black out, while he doesn't. Possibly a bigger issue, they're not simply docking to the endurance to then control it to activate whatever mechanisms it may have to slow down it's spin, but rather slowing down the spin with their retrothrusts, which is going to be a huge torsional force on the docking mechanism, and is going to be a very unstable way to slow down it's rotation.

[@quantumblur_3145]

A stabilization system could even be blamed for the loss of orbit

[@jinxysaberk]

Imo “it’s not possible” “no. It’s necessary” is so much more badass than “never tell me the odds” and I LOVE that solo quote. Cooper is the better pilot no cap solo could never

[@markwentz8332]

his reaction was pretty good "Yeah!" lol

[@Raptor747]

It's less badass and more a statement of fact--they HAVE to pull it off, or humanity is doomed (and so are they).

[@skogga]

Ask a trucker about balancing rings for wheels. Passive balancers that used bearings inside a hollow torus mounted between the duals, the bearings roll freely to counter most out-of balance issues. I'm not saying a handful of bearings rolling around inside Endurance would restore a stable balance but such a system could help. I seriously doubt the station would not have an active system of balance as well, and perhaps it was working at it's potential at the time after the accident. And what of station integrity after suffering that damage and now under 13g of stress?

[@ProfessorRoss]

Thank you -- these are all excellent points. I didn't know about the balancing rings for wheels. Three of my brothers-in-law are truckers; I should ask them!

[@jorgesilvarodrigues817]

08:37 „but its being stabilized by love“ 😂 Fits so well to the movie hahahah

[@ProfessorRoss]

Yes -- it was a student in the class, and had perfect timing!

[@ChrisCloudStaringAtFire]

Don’t give me your facts! It’s necessary! This was awesome

[@ProfessorRoss]

Sometimes you just gotta "get 'er done" ! Also, the robot was proved wrong. Gotta be more careful before declaring something "not possible", robots 🤖 !

[@caboosej8749]

agreed my friend, if your matthew mcconaughey you can bend the rules of physics by just being that awesome.

[@mickdambergs951]

Anyhow still a brilliant movie with music named no time for caution from good old Zimmer . physics and science are far fetched in most movies like this , its what makes them more interesting to watch.

[@ProfessorRoss]

Mick, I completely agree that this is an excellent movie -- a top space movie for me --- the visuals and music are amazing. Even the science is pretty on target. I like to use these scenes as a case study to get future engineers thinking about what's possible and what will be challenging. My engineering students might even help with the consulting for Hollywood some day.

[@akramlab6664]

I just started the course, saw the last lecture about interstellar docking scene, now going to watch the interstellar again. BRB

[@ProfessorRoss]

Do you understand the problem with the rigid body dynamics depicted in the movie now?

[@akramlab6664]

@@ProfessorRoss I do Prof, thankyou for the amazing lecture. I have masters in electrical and 4 years of experience in robotics and control. I want to do PhD in ADCS control and start a company afterwards. Can you please share your email/LinkedIn to connect?

[@saudalmutairi6928]

When cooper was trying to spin his aircraft at the same speed of the space ship he was leaning his head to the opposite way of the spinning, that helped him to not get blacked out , also shows the difference experience between cooper and dr.brand

[@emreyldz4324]

Yeah but he should have red out then negative g's are much more limited then pozitive gs but he says if i black out you take the stick

[@darkl3ad3r]

@@emreyldz4324 he's tilting his head to be pretty much perfectly perpendicular to the rotation axis. Sideways g forces have minimal impact on blood flow. Tests have shown that humans can take multiple times more gs than vertical rotations.

[@gertsy2000]

@@emreyldz4324 Yeah but minimal affect at 10 rpm. Thats about 2 Gs.

[@EL26010]

As an industrial automation engineer, I think the control algorithm must be designed for docking while rotating at the beginning: a feedforward control to counter the centrifugal acceleration needs to be implemented in the front of the acceleration PID (or other control loops) for the RCS. Besides, the thrusters need to be powerful enough, and with enough fuel to keep burning during the entire docking process.

[@truthseeker4280]

One movie that had Mathew McConaughey that actually enjoyed. Although i didn't know if docking was possible, very good music.

[@YichenWang]

Thanks for the detailed information!!! Never actually gave it a thought about the whole docking scene. It's actually more complex than it looks.

[@z8ttov]

4:01 gave a thumbs up immediately

[@KalmanHuman]

There should be some kind of failsafe rotation automatic stabilizer in the space station. The crew moving around in the long term could cause the wobbling as well, so there should be an automated mechanism to keep it always in a stable rotation

[@War_Diesel]

Solution to the wobble: because theyre using an SSTO, clearly they have some miraculous engines with, we would assume, enough fuel to last(because, why not?). So they just simply have the AI fly them in a circle (easy enough in space right? It is when you have Matthew McConaughey), constantly pitching and rolling, to maintain the alignment of the docking ports' axes, and THEN Cooper initiates his spin. (Then the AI REALLY has his work cutout for him lol). LOL. Still love this scene though. One of my genuine favorites. It is "realistic enough" if you take a bit of license for some of the technology and also make some assumptions about why there's no wobble present or how Endurance still rotated about the docking port.

[@BruinChang]

"It is impossible, but it is necessary."

[@dying101666]

lol. I let a friend borrow a cd of mine in highschool. when i got it back, a chunk was missing off the edge ( a small chunk, none of the music was mesed up). every time i played it, my cd player would vibrate. I can only imagine how offset and wobbly the ship would have been spinning. still a great scene though.

[@F_itaca9456]

There's a lot going on on this scene...compared with action movies is nothing but it is a piece of Film Narrative art, Here's my take, please comment: 1. A whole-life worth of experience and virtue expressed in two defining minutes with Cooper in the most realistic way possible. 2. A perfect example of what AI & Humans can and will do. (Opposite to 2001's HALL,...TARS & Cooper manage to achieve the impossible). 3. Hyper Realistic portrait of a Real exceptionally brave moment...and the acting of the joy afterwards is remarkable. 4. Necessity over possibility. ("Is not possible"..."no...it is necessary") 5. Miller was talking about the force of the survival impulse..Cooper represents the Going the extra-mile to see Murph again. Which confirms: Love overwrites Survival instinct. 6. The spinning Ships is a constant ethereal representation of the "Dance of Time" in 2001 Space Odyssey...In this Scene there is NO TIME FOR CAUTION. The dance becomes a Wrestling fight with the death. 7. Small details like the silent explosion at space and the gradual increase of sound when hitting the stratosphere cause there is some gas particles that can conduct sound. 8. The whole Orchestra playing. Any more Takes?

[@vishalsrivastava2874]

From docking scene I understand the frame of reference in terms of Law of Inertia where he matched the speed to dock his spacecraft .

[@ProfessorRoss]

Vishal, He can match the speed to dock the spacecraft, but that's not enough. He can get his spacecraft to match the speed of the *center of mass* of the spinning space station, but the docking point on the station is off the center of mass, so it is both (a) moving in a circle at high speed compared with the station center of mass and (b) spinning. There is no simple way he could dock in such a situation.

[@armandobuilds6137]

It wasn’t possible, it was necessary

[@PureXLoser]

Wow, this guy is amazing, he has been in space this whole time. Holding his breath with that amazing view of the Earth doing all these calculations! Thank you good sir.

[@jaypaint4855]

It is conceivable that the Endurance would have a good stability system, especially since it has to provide a stable artificial gravity. However, the big issue is the lander slowing the entire vehicle down singlehandedly and using its underpowered, heavily offset engines to boost the entire thing from a suborbital trajectory to an escape trajectory.

[@cmancuso84]

In the far shots it doesn't look like the station is wobbling, but in the closer shots the station is actually wobbling from the view point of the smaller ship.

[@isaackellogg3493]

8:36 you can see the wobble here, it’s quite pronounced for the small attachment. Let’s hope their RCS pushes in three dimensions.

[@RustenCurrie]

Great video! Very enlightening. In this thread I am more of "He's just a grunt." But I loved your explanations! Thank you.

[@ProfessorRoss]

Thank you. My hope is this explanation shows just how difficult and ‘miraculous’ space travel can be

[@jameslougheed9537]

Great video...thanks! But unless I missed his saying it, am I the ONLY one to notice that - as far as I can tell - NO WAY is that thing rotating at 68rpm, i.e. at more than ONE revolution PER SECOND?! 😞 (I guess one only has to count the FRAMES to see what speed it's actually running at...?)

[@ProfessorRoss]

You're right! It looks like it's rotating quite a bit slower, like ONE revolution EVERY 6 SECONDS, which would make it only 10 RPM. Perhaps we're supposed to interpret the scenes as in slow motion (???). Or Hollywood's trying to pull a fast one on us. (I counted half a rotation from times 3:50 to 3:53 in the video).

[@gertsy2000]

@@ProfessorRoss Yep I noticed this in my first time viewing. The music has a tick every second. 6 seconds a rotation, max. Thats 10 rpm. :)

[@21972012145525]

Omg you helped me actually understand what is happening in this scene on a whole new level! Not sure how we’re expected to know this when watching the movie. Thanks! Also, plz let me know if you have more explanatory scenes like this regarding interstellar! Would love to watch more

[@ProfessorRoss]

I’ve been given suggestions of scenes to analyze, so stay tuned for future videos

[@21972012145525]

@@ProfessorRoss cool! Looking forward to it. Btw you look like John Oliver

[@21972012145525]

@@ProfessorRoss haven’t been able to reach out again until now. Have there been anymore interstellar related videos? Please link them If so. Thank tiu

[@jakerobeck669]

Now this guy knows how to dock

[@IgnitionSource]

Regarding the comments about the wobble generated by the moment: definitely seems like there was some Liberties taken for the sake of telling a story. The scientists and engineers in the movie stated that the Endurance was the most versatile ship ever designed. One could assume the ship had self-stabilizing programming built into the guidance system to self-correct any unplanned events such as a wobble, since this would be detrimental to an astronaut's function while onboard. Most modern fighter jets require computers to help manage control surfaces; without them Pilots would not be able to operate the aircraft. I wouldn't be surprised if the endurance was covered with small chem rocks for maneuvering and stability purposes. However the events shown in the film don't provide enough time for the ship to take any such action to use such devices. Other things in the film that tend to get glossed over are the ability for these Rangers to enter and exit a planet's atmosphere without assistance from boosters and staging. The three planets visited all had similar amounts of gravity that would require relatively similar escape velocities needed to escape Earth's atmosphere. Each of the vehicles same to do it effortlessly and multiple times. If these vehicles were designed with this much fuel efficiency, I can look past not seeing much (if any) wobble I. The docking scene.

[@sailorman8668]

After the explosion, the stations's center of mass would have been offset to a huge degree, so it's docking port wouldn't have been rotating in the central position any longer, but would have been moving in an elliptical path, which would have made the docking manoeuvre impossible.

[@Rick_Schott]

No. But it was necessary.

[@ProfessorRoss]

Indeed! There was no alternative but to take the chance.

[@thatdudefromthefuture3346]

I know this has been a year, but It got me thinking.. is it possible to also match the wobble while the station is spinning?

[@ProfessorRoss]

Theoretically, yes, but you would need the small docking craft to move (not just spin, but move its center of mass using thrusters) in a circle that matches the movement of the docking port on the space station. Given some reasonable assumptions for the Endurance, its docking port would be moving in a circle with a diameter of a few meters and moving at about 20 mph (about 10 m/s). Of course, it would *also need to spin* to match the spinning rate of the spinning docking port. Maybe in the future, dudes like you will figure out how to do this. I think some kind of flexible docking ports that attach via magnets or something could help solve the problem.

[@patje89]

Besides all the missing mass people talk about in the comments, there would be an enormous torsion stresses on the docking port/tube if they tray to slow down this massive station with the ship while they are around 6 - 8 meters away from the center of mass. There is no way that docking port would be design for a scenario like this.

[@simplegarak]

Minor correction possibly. You said that the Endurance "was" spinning at 5 rpm. Now you can see at the start of the film the ship is stationery until all ships have docked and then it begins to spin once it proceeds into space. Given that at this point the crew believed they had found their planet and were setting up base camp there it would follow that when the ship is no longer in motion or has the crew on board, they would STOP the rotation of the Endurance. (Or i figure at least slow it down enough.) Especially if they have transports going up and down frequently at the time, wouldn't it use up less fuel if the Endurance was mostly still rather than the ships having to match rotation everytime they needed to dock and get another load of supplies? All that to say, i don’t think the Endurance is doimg 5 rpm at the start of the scene. But i could be wrong. EDIT: I mean i also assume if you were going to move all your luggage out of that thing, you would appreciate shutting off even simulated gravity.

[@alirezajafari4194]

Hi. I recently used your lectures on Hamiltonian, Hamilton Jacobi, action angle variables and several others in the area of analytical mechanics. I had an exam and needed to prepare for. Just wanted to say thank you. You did a really good job. So good that I was almost tricked into thinking that they are easy subjects!

[@ProfessorRoss]

Thank you so much for the kind words. I'm glad the videos helped you on the exam and hope they have showed you the beauty of this subject.

[@elnico5623]

Isn't 60rpm already over a rotation per second???

[@ProfessorRoss]

Yes. It's very fast.

[@tamizharasan7623]

Dr Mann docking point was different while cooper docked it at the center of the craft where it was docked previously, If you doubt it recheck the entire movie

[@hunterjohnson7393]

Great comments below. Yes, explosions are horribly messy, with forces going all over the place, not simply along the plane of rotation--there were bits a pieces flying off well off the ecliptic. Wobble/procession indeed. One of the 12 pods is gone; 1/12th of its mass missing will make the Endurance shimmy like a son of a bitch--a wheel/tire that weighs 30+ lbs that's out by 1/2 ounce will make the steering wheel shake pretty bad--and at a frequency (correct me, because I'm wrong) at at least 2x the 68 rpm--that's 2 Hz which doesn't sound like much, but it wouldn't allow a "perfect dock" which caused the explosion in the first place. And I agree--the docking armature would never be able to absorb the torque of retro rockets slowing all that mass down that quickly--it'd shear right off. And why is Endurance suddenly falling out of orbit into the atmosphere? That implies that the explosion imparted significant negative delta-V. This is the kind of scene that you just have to bin science and enjoy the show.

[@SynthD]

Doesn’t the weight of the top of the space station help stabilize the center at the bottom through centripetal force? Isn’t that why a top is shaped the way it is, so it can maintain a stable spin? My mind immediately went to the torque that docking shaft had to withstand to slow the station back down.

[@ProfessorRoss]

You've got some good intuition there. But a top is spinning usually about a fixed point on the ground, and the effect of gravity is important. In this case, we've got something spinning effectively in free space (the effect of gravity is negligible since it's acting equally all over the space station). This is also the same situation as a spinning a plate or a frisbee, if you ignore air resistance. In this case, the object spins about its center of mass, but it will still wobble, like discussed here kzbin.info/www/bejne/rKWmo5aMgNWKeZI

[@anorthosite]

Problem # 2: What are the odds that the rover's center of mass (and yaw rotation) would precisely match that of its (central, dorsal) docking mechanism. Instead, rotation would center near the aft (main) propulsion - and the nose (and cabin, and dock) would spin WIDE, like the tip of a compass needle. Problem #3: If only the rover's engines were fired (beneath the main ship, and oblique to its center of mass), it would simply make the whole (re) assembly do a Backflip, not "push" it out of a decaying orbit.

[@twelvewingproductions7508]

Bigger problem isn't the procession but the fact that the loss of mass means its barycenter changed. The loss of mass on one side of the station would mean that regardless from the procession, anyone trying to dock would be looking at the dock rotating in an ellipse when viewed from above.

[@ChainsawMan1989]

i needed this video....please make more videos like this..please.....

[@ProfessorRoss]

Thank you very much! I will try. Amazing stories and films like this not only shape our dreams and hopes but are a good way to get people interested in the science behind science fiction.

[@rizqyagung7319]

Cool! That's why we love the dynamics 😂

[@HawkGTboy]

Or how about the outrageous amounts of torque being applied to the Endurance’s airlock tube module after the Ranger docked and used its thrusters to slow the whole assembly down.

[@ProfessorRoss]

Excellent point! The torque could've led to a torsional break somewhere. There's probably an appropriate low range of thrust that would work, and maybe the AI robots could help with that.

[@geofftech]

@@ProfessorRoss I’m assuming this is where the “ease it out” comment is reference to

[@Mindraker1]

Well! That's enough physics for one day.

[@shane1039]

All-time fave movie. Thanks for this.

[@ProfessorRoss]

You're welcome. Awesome name, by the way.

[@anekdoche7055]

my problem with the scene is that the lander was burning its engines and said engines are literally perpendicular to center of mass so it would make it spin out of center

[@AntonLennikov]

I'm surprised that you did not mention the scene where main engines of the lander are being utilized for a prograde burn to return the Endurance spacecraft to stable orbit. However, this action would result in the entire station rotating around itself because the lander's engines are not aligned with the thrust axis of the Endurance. To make it work, the lander's docking port should be located at the front, and the engines at the back. Once this configuration is achieved, gyros and RCS can be utilized to rotate the entire system, and then perform a prograde burn with the lander's engine. This method differs from how it was portrayed in the movie. Unless as you mentioned endurance have some extremely and unrealisticly powerful gyroscopic system keeping it stable. It would be more realistic if the lander after docking would connect to the Endurance engines and used them to perform the prograde burn.

[@edilturdumambetov389]

How is it 67-68 rpm? On the video Endurance barely makes a revolution in over 3 seconds.

[@ProfessorRoss]

You're completely right. From the scene around 6:45 you can count the time it takes for a revolution, and it's closer to once every 3 seconds, so a rotation of about 20 rpm. But I'm working within the "world" of the movie, so I'm trusting the robot's assessment of 67-68 rpm. If we can't trust our AI robots in a clutch situation like this, who can we trust? 😏 I don't think the actual number matters to Cooper, but it makes a difference in terms of the energy of the rotation. The difference between ω=20 rpm and ω=68 rpm is about (68/20)^2 ≈ 10, so a factor of 10 difference in rotational energy.

[@ohheyitskevinc]

Nice video! I had a look back earlier in the movie to see which direction the station rotates - it’s clockwise (when looking at the station from below where the engines (and the dock) are). The station appears stationary when Mann arrives - and it should be since no one is on it. When Mann breaks the ship - the explosion (and presumably air escaping) causes the station to rotate clockwise again. They then mention that the station is losing altitude and entering the atmosphere. The main issue I have is - yes the axis will be off as the explosion and departing air wouldn’t have caused a perfectly flat spin - it’s.. how did the station lose orbital velocity when the spin should have sped it up? And if it did lose orbital velocity - it would have been as a result of the explosion departing the ship upwards, pushing the ship down.. but that wouldn’t have been a uniform push - one side would go down and then we have the axis issue again. That said - orbital mechanics show that even if you’re going at the same orbital velocity - the closer to the center of the planet’s gravity you get - the ship would slingshot off away from Mann’s planet anyway - not go down. And then there’s the center of gravity problem. My head hurts. To be honest - logic left the building when they launched the ranger on top of a Saturn V (from a building with windows in it) from a planet with 1G yet the ranger later leaves a planet with 1.3G under it’s own steam.. :) Edit: I will add that Gemini 8 had a rotation of 60rpm after the thruster stuck when Armstrong had to jettison the Agena, so this rotation to match that of the ship could be possible, but as Armstrong and Dave Scott said after Gemini 8 - they had vision issues at that rpm.

[@vpsnautilius]

Actualy it might be kind of possible but instead of rotating the ship u use a larger docking collar on the ship then the station that closes down on the station collar and enough resistance to wistand the hudge friction forces between the station and the ship in the moment of impact , basically that will be the point when the ship will start spinning

[@ProfessorRoss]

A large docking collar is a good idea -- it's worth looking into in more detail. Thanks for the suggestion!

[@RobertoRockyMan-fp2cj]

Great mathematical / mechanic analysis!!!

[@fazer8201]

gotta respect brand for doin the salute even when she blacked out

[@ProfessorRoss]

Agreed. Back in my day, we would say "give props" to mean respect. So I give props to Brand.

[@schrodingerscat7218]

This was a great scene in a thought provoking movie. Someone should now show the math on the gravitational and relativistic time dilations for the trip.

[@_A.d.G_]

I don't get what vectors would cause the wobbling, and which ones would keep the station wobbling instead of adding further rotation on another axis.

[@kelimike]

If they are near the spin axis, even at 68 rpm, they are experiencing very small G force. Telescoping and articulatable ports, capable of articulation at a rate barely above 1hz. Automated to align itself exactly to the constant changing procession. Then I would believe it possible. Then you could spin your ship up and extend the docking probe along that axis.

[@hotdogsplinter]

Perhaps the Endurance has spin stabilizers to help cancel wobble. Shrug. Movie stuff!

[@ProfessorRoss]

Yes, good point--that's possible. But viewing this as a real-world scenario, even spin stabilizers have their design limits, and being able to stabilize after an explosion of this magnitude might not have been part of the design specifications.

[@CarlosGBair]

Wouldn't stabilizing a wobble of a huge mass require huge energy from somewhere, on every rotation?@@ProfessorRoss

[@quantumblur_3145]

Regardless, I appreciate this movie creating tension using the real horrors of space travel, however exaggerated, to create spectacle. The tinnitus ringing of Endurance's ruined segments, and sudden blast of noise once it repressurizes.

[@ProfessorRoss]

I agree, it is an excellent movie. I don't mean to take away from that at all. My students and I love this movie and this particular scene inspired a lot of speculations and questions, which creates the perfect platform for discussing the topics they're learning.

[@russellmillett5642]

On the part about passing out during the docking, Brand turns her head away from the rotation and passes out. Cooper with his training however turns into the forces to better his chances of staying conscious.

[@BradiKal61]

Interstellar was billed as being scientifically accurate but it wasnt. The movie accurately described some scientific CONCEPTS but the numbers were completely fudged for story purposes. That station as you say was spinning over 10x faster and was also spinning around its original axis even though the balance would have been way off due to the destroyed modules. In the first place Matt Damons shop could not have docked with the station even if it was only spinning at 5 rpm . He would have had ro dock at the central dock port that Cooper used. Also, the water planet with the huge waves would have been a molten ball of lava due to the tidal forces that created those waves I emailed Kip Thorne about the water planet problems to see why they went with that idea and he replied back that I should buy his book. Interstellar was an important sci fi mivie for introducing concepts that were new ro many people, but it can't be called highly accurate on several levels

[@geomacaulay]

It's conceivable to engineer individual modules with automated isolated thruster systems for similar scenarios. If station is modular in design, we WOULD have redundant emergency cold gas thruster and stabilisation control - assuming multi decades of station development. Its not farfetched even with current tech.

[@lindsayheyes925]

Surely, whatever torque made the station spin so fast would have to be applied in the opposite direction. Since that force already ripped the station apart, and it is now damaged, it would cause a great deal further damage.

[@its_Criminal1]

Regarding the Wobbling there is one factor I feel like you didn't really take into account and that's how small the explosion is compared to the entire spaceship. The endurance is insanely massive and the explosion that occurred was only concentrated in the place of docking where Dr Mann failed to lock in correctly. Because of that small area where the explosion took place, it's highly unlikely that it was powerful enough to force the entire structure into a wobbling state. Only one small portion of the ship was actually destroyed and the way it's designed that is like a clock makes it so most of the mass is centered in the center, so one of the 12 sides of the ship exploding, far away from the center of mass shouldn't force the ship into a violent Wobble. Maybe an ever so slightly one or just no Wobble at all

[@rookiemoves]

Just rewatched this scene and remembered this always bothered me about the movie. Looked for this and here it is, glad I wasn’t the only one haha. Such a great scene but my nerdy brain wouldn’t let me stay in suspended disbelief.

[@pterodactylptroll]

This is great stuff. Thanks dude!

[@TheNoddy987]

I disagree about the precession ‘wobble’ analysis. If we suspend belief as to how the explosion managed to speed up rotation to 68rpm from 5rpm - the station is spin stabilised, any precession wobble imparted by the explosion is going to be cancelled out pretty quickly (stabilised like a frisbee in flight 😊). So the station does have a powerful stabilisation system- the spinning itself. As others have noted, a change in centre of mass from the explosion will cause a different kind of wobble as the station rotates around a new (‘off-centre’) centre of mass.

[@MrTchou]

The endurance wasn’t always rotating, they did stop it to have a visual on the wormhole for example.

[@brianmoore5498]

dont forget the fact that the endurance has its own internal gyroscopes that keep it stable. That system didnt fail post explosion

[@henryptung]

Hmm, re: artificial gravity experiments, I wonder - has anyone actually done artificial gravity experiments _in microgravity_ rather than on earth? It feels like any artificial gravity experiment on earth is going to be limited by the addition of a constant G acceleration (which, AFAICT, means that the "apparent" gravity inside the chamber is going to not just change between head to toe, but _change direction_ ). In microgravity, even if acceleration changes over one's body, it would largely stay in the same direction along the "vertical"; I wonder how that might affect the results.

[@paolazr]

Absolutely, without taching this video

[@happydog3422]

Isn't a spinning top more stable the faster it spins?

[@ProfessorRoss]

Yes, but a spinning top is a different situation than an object spinning in space, because of the effect of the ground "pushing" on the top, the friction at the contact point, and the effect of gravity. In particular, the effect of friction is to make the top stabilize so it wobbles less (angle between spin axis and gravity). An object spinning in space has no ground to push off of, no friction, and no gravity (or very little--the effect of the gravity gradient is negligible over the timescale shown; kzbin.info/www/bejne/naucpnaNmNmBb6s )

[@rev0cdevs38]

Can you give me the list of mathematics that serious engineers should learn? I am a Ph.D. from a signal processing major. I can learn from your lectures like nonlinear and chaos but I feel like I am a bit lack in math backgrounds. I would like to have the solid math background you have. Thank you in advance.

[@ProfessorRoss]

At the undergraduate level in the United States, mathematically serious engineers should learned the following: ➡️ Calculus of a Single Variable ➡️ Linear Algebra ➡️ Multivariable Calculus ➡️ Computational Methods ➡️ Ordinary Differential Equations ➡️ Fourier Analysis ➡️ Sturm-Liouville Theory ➡️ Partial Differential Equations ➡️ Vectors and Vector Calculus ➡️ Complex Analysis

[@CityscapeMuse]

@@ProfessorRoss And this is one of the reasons I'm a marine science and biology major... ^_^

[@gertsy2000]

Umm, I don't know how to say this so, I'll just say it. All good theory and assumptions around the shifted centre of "gravity" (I think you mean inertia) and axis wobble. But you missed a gaping hole. Case (I think) analyses the Endurance's spin at 67-68 RPM. But clearly the station is only doing one full rotation every 6 or so seconds: on the 3 scenes I calculated by (nice of the music to have a tick every second). 1 minute divide by 6 seconds = 10 rpm. Whaaaat?. 10 rpm? What happened to 67-68 rpm? Did Case make an error? Anyone who's watched a 45-record spin at 45 rpm would be able to eyeball rotation speed, and clearly this is nowhere near 45 RPM. It's 10 rpm. Sometimes we get so wrapped up in the theory we don't question the observable evidence!

[@randyzeitman1354]

He did the impossible ... and when he arrived at the station he was celebrity non-grata ... not even his family was happy to see him. He saved the human race so they gave him his house that was so ignored he could sit on the porch and drink a beer. That was insulting to the character. He finally sees Murph ... and leaves in what, ten minutes? What the hell was that!!!

[@ProfessorRoss]

Yes, that was a bit weird. The family didn't really say ANYTHING to him, other than Murph. The runtime was already a bit long at almost 3 hours, so I guess they chose not to develop this part of the story. Maybe in an Interstellar 2?

[@CarlosGBair]

There's a long line of reasoning that everything after the tessaract was just a dream... he really didn't get back to Murph, etc. And a lot of clues in the movie that (apparently) back it up . But still somewhat ambiguous.

[@teenspirit1]

9:10 I wouldn't trust the docking pipes to stand the kind of torque that comes with braking the spin of the space station.

[@nadiakhan904]

Yes yes. I get it all BUT it was still Epic. The scene is perfect cinematography

[@HorrizonLP]

What I hate is that the spinning speed shown in the movie is certainly not 68rpm. 20-30 max

[@ProfessorRoss]

Yeah, it's not. I guess they didn't plan on people analyzing the video in such detail. Don't get me wrong-- I think it's a great movie! Still waiting for a sequel.

[@HorrizonLP]

​@@ProfessorRoss When watching the movie I didn't really think of the 68, but after watching your awesome video it's really weird that they didn't think you could differentiate between it taking on e secind for a spin vs 3.

[@The0Yapster]

What if it had an automatic mechanism to regulate that, and the auto-pilot had that on automatic mode

[@ProfessorRoss]

I suppose it could have a system to regulate that. I used this as an example in a class I teach on spacecraft dynamics. So we were interested in what kind of control mechanisms would be in place. I think it would be odd that the control system could handle *keeping the rotation symmetric* after a gigantic explosion, but would have no ability to *slow down the rotation* which is the much easier thing do do (using either thrusters or reaction wheels). In terms of the universe of the movie, the response from the AI computer, TARS, suggests that their calculations might also be suggesting that docking successfully is unlikely.

[@KARANVANIYA]

I read most comments.. Why do people forget that the rotating body was an active space craft..? It can have a functional automated stabilization systems, similar to hydrolic stabilizers in modern aircrafts, in order to maintain its center of gravity at its geometric center.. Not a difficult task for a small computer program and right type of actuators to nullify any wobble.. I personally don't find any difficulty in agreeing with all that was happening in the movie scene apart from the disastrous angular velocity and the mechanical strength of the docking mechanism while applying large forces..

[@sailorman8668]

Given how much of the structure was now missing after the explosion, it would have been impossible for the 'system' to compensate for the huge degree by which the center of mass had been offset. In reality, the station's docking port wouldn't have still been spinning in the central position, but would have been offset and rotating in an elliptical path, making any docking manoeurve impossible.

[@KARANVANIYA]

@@sailorman8668 Have you seen the balancing eagle decorative piece?? Time being I can agree with center of mass being at offset from geometric center before it can be corrected but rotating on elliptic path..!! seriously?? Which planet did you learn physics from??

[@zhanggodfather8053]

I politely disagree with the motion diagram shown 6:04 . The motion u use imitates a spinning top with unevenly distributed mass. 2 conditions have to be true for an object to rotate like that: 1. It can only rotate about the center of object 2. The mass is unevenly distributed around the center of rotation. For Endurance, due to the mass lost, its center of mass is no longer the perfect center. Also there’s no contact to the ground either, so it doesn’t have a fixed center of rotation like the spinning top. There will be a new center of mass based on the now unevenly distributed mass and that’s gonna be the new axis of rotation. The best example I could think of is tossing a coin into the air. We can use tensor method to describe the instant torque resulted from the explosion. Draw a line between the new center of mass and location where torque is applied and set it as the z-axis. Now u have Fz, Tx and Ty. Tx and Ty result in rotation and Fz results in linear motion. For rotation analysis we only need to look at Tx and Ty. We borrow the technique from aircraft rotation analysis. There’s gonna be roll and pitch but no yaw. (Fz goes through the center, no torque about z so no yaw) It kinda hurts to imagine this in my head but u get the idea. 😂 Personally, I’d argue that the Endurance stability control system probably detected the pitch and used its thrusters to cancel it. Maybe the flight computer then malfunctioned so it didn’t get a chance to fix the roll and fall?😅

[@Michael-it6gb]

What about all the debris falling of the station and potentially hitting the spacecraft itself?

[@Quickstep1716]

My two biggest problems with this scene are: 1. Endurance is clearly not rotating at 67/68 rpm, which is more than one rotation per second. By glancing at the visuals, it looks more like 20-30 rpm. 2. There's no way the explosion would generate enough delta v to deorbit the space station in a matter of seconds. That would mean the orbit is dangerously unstable in the first place. Moreover, a few seconds of thrust from the shuttle couldn't possibly stabilize the orbit especially considering it has to accelerate the mass of the entire station in addition to the shuttle itself.

[@simplegarak]

That's something I hadn't thought about... Maybe the long term plans with Endurance would be that it would have a decaying orbit. You bring down essentials and get a base camp started then the entire rest of the thing comes down and provides you with the rest of the supplies. Interesting idea...

[@Quickstep1716]

@@simplegarak It has no heat shield though, so I fail to see how that's possible. I think it's just a plothole

[@simplegarak]

@@Quickstep1716 True about the heat shield, but if it requires specialty, esoteric knowledge to realize it's not really a plot hole. (I mean how many movies take place in the past have the wrong breed of chicken in them? 99.9999....% of them. But almost nobody notices or cares.)

[@snakearts6309]

you forget about the two robots that are assisting in the docking, all cooper is doing is piloting the docking part, they are I am assuming advanced ai machines who are doing all the calculations to do this am sure without them he could not of done it alone.

[@ProfessorRoss]

Yes, good point. It isn't just Cooper -- it's a human-machine interaction. Makes me wonder, "Could the machines do it on their own?" I think C.A.S.E.'s expressed doubts about the probability of success suggest the machines wouldn't try it on their own. The humans have that necessary will to survive.

[@orebabaalibaba]

One question about this Sir, after docking, when they apply thrusters in the reverse direction, there would possibly be enormous torque getting applied on the docking mechanism. Would it be possible to calculate approximately how much? And whethere there is any material on earth that is capable of withstanding such enormous sheer forces without breaking

[@kelseyobrien543]

Yes but, yes but TARS did it! Fantastic movie though and as close to real science combined with holllywod we’ve ever had. This movie ignited my passion for space science

[@kevinboyce-n1w]

I ❤Interstellar, whether possible or not it's fascinating!!

[@kevinboyce-n1w]

Oh and cooper had 2 Ai robots helping him... 😯

[@ProfessorRoss]

Oh yes, it's a great movie. Any movie that can inspire people through its storytelling and on the technical side is quite an achievement. Nolan is awesome!

[@roughlygalaxy]

Amazing explanation, many thanks ;) What is your take on how strong the docking mechanism would have to be for the spacecraft to be able to slow down the rotation of the Endurance?

[@ProfessorRoss]

That's a very important question, but it's more on structural engineering (or strength of materials) that goes beyond my expertise.

[@Piemur1]

I must also ask, what about translation of relative planar location while spinning? With fixed periodic reaction thrusters, they would have to only thrust when they are facing the correct orientation else you would have wobble while translating to align with the docking port. Once aligned before spinning it would probably be a bit easier, but if its just the slightest bit off, it would be difficult to align with it again because you would also have to kill your velocity vector when you're aligned again, and that would be assuming the thrusters are able to fire at such a precise amount at the right precise timing with the exact precise power. (Yes I am repeatedly repeating precise).

[@shannonmcstormy5021]

The above is the only time my Suspension of Disbelief was broken while watching Interstellar. My mind went, "Ummm.....something may not be right about this....." I'm glad my pathetically small amount of physics and hard science wasn't wrong. On the other hand, when it came to "black holes," my mind just switched to "it's basically magic, plus supposedly it's very scientifically accurate, so it must be fine." The docking scene had an exploding space station, debris, and how neither the space station nor Mathew's ship would be designed to "take in stride" such a catastrophic accident. Most people don't know how vulnerable things like the ISS Space Station actually are. From an earth perspective, it's pretty flimsy.

[@richardmcgowan1651]

Some of the shots you can see a wobble and others you cant. Not a big one just a tiny bit. Maybe just to trick the viewer into thinking it is without bringing that issue into the scene.