In the press leading up to this season, the Showrunner Naren Shankar owned up to this mistake, hinting that there was one episode involving a difficult docking attempt where they fudged the physics a bit
That's one thing that did confuse me. In the book, the Chetzemoka had multiple engines, and Naomi shut one off. This created a net force on one side of the ship that kept it going in a circular path. Not only that, but the centrifugal force it created was enough for Naomi to feel spin gravity onboard.
In the show she can actually feel "the spin gravity". You can see her walking at an angle as well as right after using that hruster when she takes off her helmet it's rolling towards the airlock even though it should stop because it wasn't round. A lot of people missed it because the helmet fact was hard to catch as well as people thought she was walking like that because she was hurt
Also I think they changed it because if in the books it looked like that then ship would jump keep spinning faster and faster because that would be constant force.
@@paxon57 actually constant force is what would be needed to maintain a circular path, although it would have to be constantly perpendicular to the ships current velocity, this could most certainly be achieved by turning off a thruster on one side of the ship, if that force imbalance is enough to keep the ships main engine roughly perpendicular to it's velocity vector it would move in a circle EDIT: Shit no you are right, I thought about it some more, a constant force imbalance like that would cause the rotation speed to increase continuously so you still wouldn't get circular motion, so a brief foreign of the thruster could actually have the desired effect, what he showed in this video was the thruster firing too hard causing too fast of a spin, but if he limited the thrust so the ships rotation was slower you actually could get the thing to go in a circle. I'm supposed he didn't mention that even if the ship fired the thruster just right to get the rotation at the perfect speed to keep the main thruster pointed inwards and the ship going in a circle the scene still would be wrong, when she leaves the ship she would fly away from it at a tangent to the circular path that it is on, she physically could not end up in the center...
I mean, the ship would still fly in a circle. It is spinning around its center of mass and the main engine constantly moves the center of mass forward, making it look like the ship is flying in a circle to an observer not locked to the ship.
I mean that sounds cool, but Epstein drive cones don't gimbal. Imagine you're already burning at 10g, and then the drive gimbals. goodbye organs, goodbye crash couch mounts, goodbye limbs
Naomi's ship only made one rotation every minute, in your example it makes a rotation every 2-3 seconds. Makes it kinda hard to compare, the ship just seems to spin around its axis which doesn't look like the growing spiral it should be. But you're correct and I didn't realize the situation in the expanse was wrong on so many levels.
The speed of the spin makes no large scale difference. Since there is no continuous net force acting toward the centre of the circle, the ship will end up flying off on a rather bizarre trajectory.
@@RyanRidden shes, its a bizarre trajectory, but she will move in a straight line once she moves off, so she will fly along the ship as it spins around her depending on where she jumps off, again, you're thinking in the wrong frame of reference.
@@RyanRidden couldn't the thrust of the main engine be that force toward the center? As the ship is rotating, the direction of thrust is rotating also.
Totally right IMO. The slow rotational force remain while the non gimbaled thruster continued to fire. This would lead to a circle. In this video the rotation ist way to fast to illustrate this, but if you look closely the circle is there, but smaller than the ship itself. Redo this with much much less impulse from the sideway thruster and yo get your circle.
TBH It is possible to form a full circle orbit with just the main thruster, granted you already applied torque to initiate the turning motion with a side thruster. Imagine it like the satellites, if we ignore the air resistance, there's only one acceleration affecting them, gravity. So if you match your thrust with your turning ratio, you can mimic this motion around a virtual centre. This is something we have practiced in Elite Dangerous. Also, it can be replicated in KSP. For example you might find an asteroid and try to maintain a relatively stable orbit around it by adjusting your main thruster. It's not easy to get the turning speed and main thrust force right, but it's possible in theory. You only need to create that centripetal acceleration. However, in Naomi's case, if Naomi gets out after we have obtained this orbit, she would have to intentionally push herself towards some range of direction with some amount of force in a range to stay inside this circle, and even in the best case scenario, this entrapment would be temporary, since she wouldn't be able to adjust her direction of motion after jumping.
0:20 well yes, but my issue with that scene is that the corkscrew is going around the ships travel path, we only saw naomi activate one thruster so no matter which side it was on it should have made the ship face towards then away from the travel path and not circle around it. for it to get to the point we see in the show she would have needed to activate one then activate the opposite one to stop the movements at the right time to get it to stop ~90 degrees perpandicular to the travel path then activate a third one to get it into that corkscrew spin. Oh and naomi wouldnt have just stopped in the centre of the corkscrew, she wouldnt of even gone inwards, the centrifugal force of the spin would have thrown her away from the ship unless she somehow timed it right and with enough force threw herself in just the right direction to overcome this centrifugal force but even then she would just come out the other side as nothing is holding her inside the ships corkscrew.
I think you are sort of wrong. I agree she would get flung away. But you can still see it as a circular path if you have the correct frame of reference, like an imaginary point that the ship is pointing and accelerating towards as it is rotating around it, i.e. the center of the circular path, like at 4:39. The speed that the ship already has relative to earth or whatever doesn't matter. If it's rotating at 1 rpm, don't see why the acceleration in any given moment wouldn't get canceled half a period later when it's pointing in the opposite direction. Memories of early kerbal rendezvous come to mind where I realized continuously pointing towards the target and slowly burning constantly can make it so you don't get any closer, you just sort of orbit it. Now if it's a ship you're targeting in the center of that path, you need the correct relation between rotation and acceleration for it to be circular relative to that target ship. But the center of the path can be an imaginary point. If your ship spins very fast and burns very slowly, that point is closer to the center of mass of the ship, but the slower you rotate the further in front of the ship that point will be.
This is the correct answer. Maybe the ship was oriented wrong for that - I don't know because I haven't seen the scene yet - but even if it is, Dr. Ridden should have at least mentioned it. It's really obvious when you know the net force needs to be towards the center of the circle and the only force is the main engines: F(centrifugal) = F(thrusters) You just need the side thrusters briefly to start the ship rotating in sync with the circle you want. And as you say, just like that picture at 4:39 - how can he miss that?
There was a 3D display of the spiral and fwd motion (like a spring) of Naomi's ship inside the Razorback... Also the one time firing of the side thruster will certainly not sustain a circular motion. Naomi jumping out of the ship would be moving tangentially away from the circular trajectory (if the ship could indeed moved in spring like trajectory as the display showed in the razorback) Lastly if they(Alex and Lady Tank) already spotted Naomi outside the ship in mid of the spiral spring, they could have easily entered the spring from one of the 2 openings... There was no need to try the interstellar like docking move to get Alex killed. May be it was a scientifically inaccurate hustled move to get Alex out of Expanse... I read some news that Alex dying was an edit made to the story as they were letting go of him in real life... Is there a way, Razorback's or Naomi's gravity interect with Chetzemoka's gravity and help sustain that curcular motion? Still I feel in that case, Naomi should be orbitting the Chetzemoka and not the other way around...
Your quite right, even if it was possible, once Naomi jumped she would no longer have the centripetal force acting on her to be contained in the spinning system. The gravitational pull of all objects in that system are way too small to make any noticeable impact. The main engine would have been burning at around 0.3g which is much larger than any other force in the system.
Rotation speed will make no significant difference. This would be the expected trajectory, if you are curious! ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
Alex dying irritated the shit out of me. This is a case of knee-jerk 'Social Justice'(tm). I am NOT defending the actor's "supposed" activities, but Alex Kamal (THE CHARACTER) is beloved AND integral to the story. If Arjun (Chrisjen Avasarala's husband) could be recast due to scheduling issues with an actor...a recast due to supposed actions taken by Cas Anvar (the actor) AFTER SEASON 5 would have most likely been accepted by the fans to keep the continuity and move on. The WAY this was done was complete and total horseshit, and pretty obvious that it wasn't done organically as the editing of the final scenes (as well as his death scene) were garbage. Oh well. (Critical Drinker voice).
Hey there! Could you answer me a question that I - for some reason - couldn't find a definitive answer to? How long would it take accelarating at 1G (I presume that's close to how quickly they accelerate/decelerate in the Expanse) to reach let's say.... 90% of the speed of light? Essentially my question arises from the idea, that if your method of creating gravity was using continuous 1G acceleration, first off, using conventional fuels, you'd empty the tank REAL quick, but let's say that's not an issue, how long could you travel, before reaching super fast speeds. Where even time dilation starts to become at least somewhat noticeable.
@@gregsomlai297 The speed of light is 2.998e^8 m/s, 1g is 9.80665 m/s^2. 2.998e^8/9.80665 = 30570000s, 509500 minutes, 8492 hours, or 354 days. So about 320 days to reach 90% c at 1g.
@@thentil Thank you! Yeah, that's what I figured, it's just that I've seen someone calculate it screwing up an order of magnitude, making it a month or so. But still, that's pretty damn crazy. Wouldn't take that long...
In the first example, the ship does end up in a path that is analogous to a moon orbiting a large planet: the moon spirals while the planet goes in a "straight line" (or whatever orbit ot happens to be on). If the rotation was much slower than your example, (which is plausible based on the scene) wouldn't the ship appear to take a circular path in a reference frame similar to the planet in my analogy?
What makes problems like this hard are reference frames. After one full rotation of the ship, all the thrust vectors cancel out. If you set your reference frame to the average velocity of the ship, then the ship will appear to be moving in a circular motion. Like with with any object moving in a circular motion, if a passenger detaches from the ship, she will be flung away from the center of the circle. From Naomi's perspective, she would be floating in space as the rocket spirals away from her. The other big physics mistake in that scene was that she wasn't incinerated by the Epstein drive when it came around to point at her :)
I'm hoping that the success of the Expanse and The Martian will make it clear to movie/TV producers that there is a real appetite among the public for more realistic sci-fi and could lead to a fictional series where they actually do the science justice and don't compromise the realism for cheap thrills.
First time SAS was OFF, and on the second time it was ON.. u can even see the main drive correcting itself. Try again, like the first config, but with a weaker and shorter side booster and with the SAS OFF.... *SAS = When active, SAS will provide input to stability systems to dampen craft rotation and, depending on capabilities, lock onto a specific orientation. The user can override the current rotation for any axis. Since it controls heading, it can be extremely useful for lander missions. When active, the SAS itself doesn't drain electricity, though reaction wheels may continue fine-tuning even in space. It will utilize all active control systems to achieve this, like the user would by pressing the keys.
Whoops I missed switching it off in that recording, though it doesn't make any difference to the end result. As I said in the video the net force must act continuously, which no burst can produce.
Can u try again with SAS off, and with a shorter RCS burst? Because, in my head, if you put a rocket with locked gimbal main engine and then start a rotation moviment, with the RCS, with no force to stop the rotation, it will make a spiral as in the series.
No need to test in KSP since we have the power of mathematics! I ran through the calculation, and this is the path you would expect from the scenario depicted in the show: ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
Your wonderful illustration of the ship’s actual trajectory is a type of cycloid, which would be an ellipse in an alternate frame of reference. Perhaps the computer graphics aboard the Razorback were crunching this? Eh? 😏 What bothered me far more was that Naomi **jumped straight into the frickin drive plume!**
Actually this guy is wrong in almost every way. A short thrust does in fact induce a permanent spin, inertia means it will continue to spin until some force stops it. There is no friction to stop it. If the thruster were to fire constantly, the spin would accelerate until centripetal force pulled either ends of the ship apart. A short burst means there is a constant, unchanging rate of spin. The spin in the books and in the show is relatively slow at maybe 1 spin every 40 seconds. Not 1 every second or higher as shown in this video. Add constant thrust perpendicular to the the axis of spin. This constant thrust will not stop the spin or slow it down. It will drive itself in a circle, inducing artificial gravity both along the line of constant thrust and perpendicular to it. Also before spinning, it was accelerating along a path dictated by orbital mechanics, its velocity constantly increasing. After the spin begins it is no longer accelerating, because as it goes in a circle it cancels the acceleration at the point opposite on the circle. This means it is orbiting on a ballistic trajectory along a path dictated by its velocity when the spin began. If you were to view this from a point in space that wasn't moving relative to the sun, the ship would be flying in an overlapping corkscrew pattern. If you were going along the same orbit as it, it would look like it was flying a perfect circle. It really depends on your frame of reference Naomi being in the middle is wrong though.
@@Skunkwurx , Dr. Ryan made a subsequent video in which he corrected himself, and I accidentally responded to this one instead. Your “overlapping corkscrew” path was the cycloid I spoke of, which he illustrated in that video. For some reason his cycloid was very tall, which led me to believe that the alternate frame would yield an ellipse instead of a circle - I just trusted his math. Though I can’t think of an intuitive reason why it would be elliptical instead of circular.
Yay! I was actually right in my assumption that a single thruster firing a short burst at the front of the ship wouldn't cause the ship to enter a barreling motion. While I didn't play this out in KSP, the Jebediah in me thought this wrong from the get-go.
Actually this guy is wrong in almost every way. A short thrust does in fact induce a permanent spin, inertia means it will continue to spin until some force stops it. There is no friction to stop it. If the thruster were to fire constantly, the spin would accelerate until centripetal force pulled either ends of the ship apart. A short burst means there is a constant, unchanging rate of spin. The spin in the books and in the show is relatively slow at maybe 1 spin every 40 seconds. Not 1 every second or higher as shown in this video. Add constant thrust perpendicular to the the axis of spin. This constant thrust will not stop the spin or slow it down. It will drive itself in a circle, inducing artificial gravity both along the line of constant thrust and perpendicular to it. Also before spinning, it was accelerating along a path dictated by orbital mechanics, its velocity constantly increasing. After the spin begins it is no longer accelerating, because as it goes in a circle it cancels the acceleration at the point opposite on the circle. This means it is orbiting on a ballistic trajectory along a path dictated by its velocity when the spin began. If you were to view this from a point in space that wasn't moving reletive to the sun, the ship would be flying in a corkscrew pattern. If you were going along the same orbit as it, it would look like it was flying a perfect circle.
Another problem was naomi only did one maneuver which should have set the ship to spin in a way to speed up and slow down but it shows the ship doing a cork screw which should have took 2 maneuvers. She was traveling in the wrong direction.
The KSP ship is spiraling the moment the thruster gives it rotation. Any body separating from the ship at its center of mass will stay next to the ship (or on its larger spiral path, if you rotate slower). Naomi's jump exited the ship in the direction of the rotation, putting her inside the spiral, traveling (slowly) along the diameter of the spiral. Naomi "fell" towards the rear of the ship at 0.3g (the ship's acceleration), so it moved away from her, but will eventually circle back to the place they separated.
The path depends on the initial forward speed, speed of rotation and the force of acceleration of the back thruster. It wouldn’t make the circles like in the movie, but there is a speed of rotation that would make some kind of spirals moving forward with inilial speed. Naiomi should be left out of the spiral with the initial ship speed before rotation starts I guess
Thanks for doing this! I was bugged by this when I saw it and had some discussions on some other vids. It would be nice to have a trailing line to see how the ship was still moving through space to demonstrate what the show was portraying with it's display for comparison.
The script implied that the ship was "in a spin" but then the graphic shows it in a spiral. It's unlike the show to get the physics in space majority wrong, so I wonder if there was a miss communication between the effects team and the show runners that was then too late to fix.
In your Kerbal model the perpendicular thruster was very powerful and in fact I think too powerful. In the episode the thruster was clearly pretty weak and I think that's important for the model. To me it seems like what Naomi did was set her ship into a fairly slow tumble. With the main drive burning away at an unknown thrust level but likely less than 9.8m/s/s (because Belter ships likely wouldn't want to burn at 1G ever) I think it's possible for the ship to trace a spiral path as depicted in the show. That would of course likely gradually grow over time as the main thrust slowly ate away at the rate of tumble. I think the key is the rate of tumble. The ship needs to tumble slowly enough for the main thrust vector to precess over time so as to put the ship in a spiral. What I'm saying is your Kerbal ship tumbled too fast because you used too much thrust. Model it again with less than 1 g of main thrust and a much slower tumble rate and see what happens.
If you slow down the angular velocity the ship will describe a circular pattern around a hypothetical point on the orbit at the time of side thrust ignition(note that the orbit is constantly changing when thrust is applied), the only error was on the plot at 1:18 where the spaceship is pointing wrong, but if the immage is generated by a computer thar shows instant velocity than it would be a correct representation of data. BTW if Naomy didn't run outside the ship she would bump on the ship st the next rotation
If she just released herself softly, she would travel a straight path leaving the circle created by ship's circular motion with the ship's circular velocity at that time.
Your spin radius was along the center of the craft, in the show it was roughly a kilometer across because the angular thrust applied was much much smaller than what you are doing here
The corkscrew trajectory, shown in the display of the Razorback, could make sense, if it was relative to the Razorback, who at the time was in the process of matching its trajectory (and hence velocity) with the ship of Naomi.
It's an interesting idea that they could be in similar reference frames, however this is not the case as we see the Razorback is still on a normal, fairly linear trajectory, while the other ship is very non-linear.
The physics in The Expanse works selectively. When Roci shot Pela by a disarmed torpedo they found later this torpedo was stuck in a board. But at the moment of collision the torpedo should have 20 km/s of relative speed (accelerated at 100G for 20 seconds). You know, artillery shells penetrate heavy armored tanks at a speed of about 1 km/s. So the torpedo had to penetrate all the ship decks like heavy railgun projectiles and completely destroy Pela and crew only by kinetics.
Love this although you sent your poor guy into the sun! My son loves Kerbal and I fully trust him if he ever needs to plan a launch and sustainable orbit . Please keep making videos during the long desert between season 5 amd 6 . Also glad to see some ads w your videos yay! Congrats on YOUR expanse(ion) !
KSP is an amazing tool to help learn about physics and orbits. I first started playing it while I was doing my undergrad physics courses. Although I had a good idea of the theory putting it to practice broke my brain in the beginning! Don't worry, I keep making videos, mostly on whatever aspect of science catches my interest. That said these last view videos on the Expanse has really made a big impact, its quite amazing!
Your thruster was too strong and your main engine wasn't strong enough. Also the frame of reference is important. She would get left behind like in your example but that's because the arc of the ships spin is like thousands of miles in diameter and would take a while to turn around and come back.
In your example, the camera is fixed to the center of mass of the rocket, so obviously you wouldn't see anything else than a ship spinning around itself. The camera is spiraling with the ship. Might as well just shut the main engine down for a similar conclusion. You should've left another kerbal floating outside just as you started the spin for a valid point of reference. I agree that Naomi should've been flung outside of the spiraling ships trajectory, but the ship definitely would've spiraled around a point in space that moves in the approximate direction that the ship was travelling before the spin was induced.
I have a question: If the ship is spinning around, shouldn't after a single spin the net force on the space ship = 0 (velocity is still large, but acceleration is 0)? When the Kerbel jumps off the space ship, shouldn't his net force (acceleration) also = 0Why doesn't the ship and the Kerbal travel at effectively the same velocity? The second question: The ship would have a net force / acceleration of 0 at the END of each rotation, but during the rotation, they would have an accelation in the direction of the ship (which is in a circular motion), therefore *Compared to the previous velocity* , wouldn't it travel in a circular path from the perspective of the Kerbal?
1 = the ship is still accelerating from the rocket engine. Once the Kerbel is out it will stay at current velocity and the ship increases its. So Kerbel is left behind. 2 = The ship (first example) are traveling in a circle, but due to high initial velocity there cercal is so large you can't perceive it on small distances like we see in the vid. In the second vid the ship's velocity has translated a few degrees to the left but as there is no continuous course (like spin) to create a circle around a common point, it is still traveling in a straight line just adjusted a few degrees to left.
Without watching it, you can do in space whatever you want manouver-wise if your RCS Thrusters are strong enough, have inifnite Fuel and if your Main Engine has infinite Fuel and enough Thrust. Star Citizen manages to do it quite well, your RCS Thrusters are strong enough to "fly" like an Airplane.
Hello Physics major here. TLDR: if you spin slow enough so your main thrust always points outwards to your circular path you can fly in a circle. What happed in the show is very possible and not inaccurate to the physics at all. The key is getting the correct rotation speed relative to your thrust. In your experiment you conducted in KSP you spun up your ship much faster then Naomi with the Chetzemoka. It is possible to make a perfect spiral pattern if your rotation speed is such that the engine is always pointed tangentially to your path you would travel in a perfect circle. I admit that you would need to time the thruster perfectly to do it right, however unlikely it is possible. one cavoite to this is that Naomi would probably be just flung outside of the path due to centrifugal force as soon as she stepped out of the air lock so that's one thing. Also the reason the sip in KSP appeared to be moving in a straight line and just spinning was because ksp always follows the reference frame of whatever ship your focused on, while in reality the ship was flying in a curly loopy pattern that would look like the way you draw a spring in 2D. Its kind of like how an orbit works but gravity is always pointing tangent to your path by default great vid otherwise. (If I'm wrong please point it out, I love to learn form my mistakes)
After nose force is applied and rocket begins to spin around its mass center, rocket will no longer accelerate. That's because main thrust direction will rotate along with the rocket, so the speed of the rocket at the end of each rotational cycle will be equal with the speed rocket had before it started to spin. If the passenger jumps out when tip of the rocket is oriented in the direction of rocket initial velocity, passenger will continue to move in the same direction with the rocket + the perpendicular speed vector Naomi had right before the jump. Jumper will get farther apart from the rocket (carried by the kinetic momentum of the jump) but rocket and jumper will have almost the same speed from an outsider's perspective (speed of the rocket being obviously far greater than the speed generated by Naomi's run).
Out of curiosity, is there a way to replicate the path observed on the show? Let’s assume that there may be some autopilot functions involved that reacted further after Naomi’s control input. The “spinning in circles” seems like it could have some utility as a “parking” pattern where constant gravity is maintained by a constant engine burn (or by just being a functional “centrifuge drum”). Wouldn’t be shocked to find that aberrant control inputs force the autopilot into a “safe” holding pattern where relative forward motion is stopped.
if instead of a single rcs burn you'd do two burns to point the ship sideways and then have a leak constantly venting a small amount of air at a perpendicular angle, that might result in a spiral, i think. you would then have to jump out of the ship in such a way that you'd end up inside the circle, because otherwise you'd either get crushed (exiting at the front) or burned (exiting at the back) or first crushed then burned (exiting on the wrong side).
There is another aspect to the maneuvering of a spacecraft that you did not consider. Reaction wheels, that generate torque onto the main axis. Combine this with thrusters and you can in fact “fly in a circle”.
Wouldn't it be possible to create a circular trajectory by giving the ship a specific angular momentum such as the thrust force is always pointing at the center of the circle?
I think that spiral motion is possible. You assumed that the ship was burning along it's velocity vector, but what if it was changing course? Imagine the 3D cooridnate system where Z means up/down. Now let's say that velocity vector was towards Y+ axis but ship was changing course so it was thrusting at 90 degrees towards X+ axis. Let's say that the thruster that fired was aiming at Z- axis and put the ship into a slow spin (in your video spin was wayy to fast). In that case I think ship would start moving in a spiral like in the show and if Naomi jumped out from the side facing inside of that spiral she would be inside of it (at least for some time unless she made perfect calculated jump to cancel out the velocity offset :p )
If the spin rate was sufficiently slow, and only in a single axis, and the thrust sufficiently high, yes it would spin around in a circle with respect to an observer moving at the same initial speed, though Naomi would most definitely not end up in the centre of that circle, rather she'd be flung out away from the spinning ship (and probably burned up in the drive plume, ouch). The thrust vector is in one direction in relation to the ship, but as the ship is spinning, that thrust vector is changing direction with the ship as it spins around, ergo a centripetal force. Key point is, though, it would not be a corkscrew as shown in the show, because the initial direction was in the direction of travel, and thus the rotational axis must also cross the direction of travel.
If the ship is rotating while the engine is burning, the ship acceleration should basically cancel out. It goes forth and back... while following the linear velocity it had before going into torque. But once torquing it doesn't accelerate/de-accelerate anywhere anymore. When you eject a person, there may be a difference of the current velocity the ship had at the moment of exit vs. the forward and backward acceleration the ship is doing while it is spinning. So I'm not yet totally convinced that a scenario as seen on screen is physically impossible by one KSP simulation.
I don't know why, but I didn't get from the show that Naomi's ship was circling (even though it's clear on Alex's screen). I completely missed it. I just assumed she set off a thruster and it put the ship into a spin so the Razonback couldn't dock with it. Strange that they wrote the show that it put it in a circular path. I mean, I'm not a physicist (took Physics 101 at University but nothing more) but I would have never thought firing a random thruster, no matter where it was on the ship, would make the ship circle. Thanks for explaining everything. And rest in peace good Mohat.
Yeah, with the ship tumbling it would have been impossible for Alex to doc, depending on how the airlock is located. I think one of the best docking scenes is in Interstellar. Mindblowingly crazy.
What about the main drive thruster in your first example? Since it is continuously firing what about about the huge influence it will have on the direction of the craft?
The main drive doesn't shut off on the show either. If the main drive was off in the first case, then the ship would have just started spinning around the centre of mass as it continued at constant velocity.
if you fired the thruster in a way that left the ship spinning so it always faced 90 degrees to its theoretical path in a straight line and kept the rocket going at low thrust, that would produce a small circle wouldn't it? In your demonstration, you fire the thruster at an unknown length of time and newtons. Think of the ISS, it is always facing the earth in a particular way like the moon. So when the ISS need to speed up they fire their thrusters and increase their apoapsis. As their spin rate is relatively slow unchanged from the thrust they don't need to adjust. Could you try this please?
Now here's the thing though. Reduce that massively oversized and overpowered side thruster of yours by a factor of 100 or so, so the rpm is like 0.5 and have the kerbal slightly push off from the opposite end of the thruster. Something tells me that's gonna be a bit more realistic.
I am just a petty simple earthbounded engineer. So Sorry if miss some of my physics class in Uni. Q: What if we assume, Naomi's ship flew in a straight vector with a slight rotational motion around the flight axis? That could explain the spiral. Can some one point out if I am wrong/right here?
I'll disagree with you on this. I might be completely wrong so correct me please. The mass of your ship is far to low for the thruster you use. If you alter the forces on the ship, mass of the ship and the burst of thrust, so the ship has a spin of .5 rpm or .3 rpm while having a continuous .2g acceleration from the main drive, you will have a resulting motion much closer to what we see in the show. The part where Naomi is in the middle of the spin still doesn't work.
Are you able to do a video on the decoupled physics in star citizen during the upcoming free fly event (try the game for free) ? Their are two modes of flight in game, one has the computer control your thrusters to try to determine where it thinks you want to go and apply them that way. The second mode is basically manual control by the pilot. After watching this video on the expanse I wonder if star citizen does a better job. One thing people manage to learn to do in dogfights is circle their enemy while firing at them, a little like what the expanse did here.
All that's needed to create circular motion is a consistent force directed perpendicular to the direction of motion. A spinning ship can't produce that since the direction of the force is always changing around the ship.
2:38 the ship seems to follow a straight line despite the main engine firing and the ship rotating. We should see the ship wiggle left and wright from the unlucky Kerbal's point of view, should we not?
Probably has more to do with the thrust to mass ratio. The thrust is too low to perceive change in velocity given the frequency of rotation. Try that with a mainsail and a slower rotational speed, then you should see quite a difference.
Your test does not reproduce the conditions of the show. Clearly, the unfortunate ship was much heavier and the main drive very powerful compared to the thruster that only induced a slow spin.
Still,a small burn from your thruster would just change your course slightly, less than a degree to the right or left. It wouldnt induce flying a circle. You would need continous fire from engines and thrusters to fly a perfect circle, which would burn a shit ton of fuel, your main engine would need to be at almost zero thrust to not flly off .
@@Intrepid17011 that’s not true. You induce a spin by firing a thruster that results in a force component perpendicular to the axis of the spacecraft and offset from the center of gravity. With a continuous firing of the thruster you would keep increasing the amount of spin, probably until the occupants are transformed into chunky salsa and continue to increase until the spacecraft came apart.
Considering you dont know the mass or how much thrust is produced by the ships rcs thruster or whether or not it is using any gimbal, this isnt an very accurate experiment. I get what your trying to do but it would have been better to see what it would take to make it happen. It is possible, after all, if the correct forces are applied. Now as far as her staying in the middle, your right lol. She would need to be tethered to the thing or something for that effect. Love the use of KSP though.
May be that your initial main engine burn was too strong ? Did you try some other variation of parameters to get somewhat similar spin to one that happened in the show?
The result comes out the same since the nose thruster only introduces torque around the centre of mass. The ship will always end up spinning around the centre of mass, and won't reproduce what we see in the show.
@@RyanRidden if a ship had thrust constantly sent out in a circular motion (engine orbiting the ship and thrusting outwards) the ship would clearly take a circular path your spinning ship seems to have no thrust, only momentum. that engine is spinning around quite quickly, surely it could result in a spiral if thrust is large enough compared to initial momentum if we think of the length of Naomi's spiral as the direction of initial momentum, the spiral could result if during her maneuver the engine became perpendicular to initial momentum, and spinning motion can result from sideburst as there is no friction to stop the spin; engine acts as though it is orbiting the ship as per first example here, resulting in circular motion of ship if thrust is large enough vs spin speed. . .
The space walk is pretty easy to do since it was a straight line between ships, but unfortunately their helmets stay locked on in space, so no true recreation is possible there.
@@RyanRidden I'm not too familiar with the game, but I thought there is Oxygen supply, so couldn't you force one minion to run out of oxgen and then do the walk? On the other hand these are little green aliens so I'm not sure how well they translate to human biology. And you probably also can't do the breathing out and injecting yourself with hyoeroxygenated blood parts.
@@Lionfire1998 I think with mods these sorts of things are (probably) possible, but in the vanilla game, the Kerbals only seem to need a seat (and not too much heat) to survive indefinitely.
@@Karsaroth In a enclosed cockpit kerbals will live indefinitely. If they are outside with just a suit they will last five years. Clearly kerbal suit recycling technology is quite advanced.
You're definately wrong on this one, ship in the expanse was turning slowly, angular momentum will keep the ship turning unless a correction thrust is applied. Thrust from the drive combined with the ships rotation would cause a chiral deviation from it's original flightpath. Here the ship is simply spinning like a top. While in the show it takes minutes to complete a rotation. Edit: Thinking about it a little more the thrust would have to be offset from the centerline to rotate the ship in this manner, otherwise the deviation will be sinusoidal.
Hold on now: Your first Kerball example spins (tumbles?) in a way that appears identical to if it's main thruster were off, passively somersaulting end over end, yet it's main engine is burning the whole time. Your pencil analogy fails to account for the constant push from the ... eraser. Without a correcting counter directional thrust to stop the axial tumble, this should cause it to travel in a circle! Though no, there would be no reason for Naomi to stop in the center of the circle. What am I missing?
I dont get it. In the first case the rocket is rotating with the main thrust still active. Wouldn't that count as the starship doing circles? Very small circles but I guess that if you would to adjust the lateral thrust to be a lot weaker, it would rotate slower and so result in a circle with a bigger radious.
How could we hear Bobbie's voice through the space suit when sound requires a medium to travel through? Outside of the suit is a vacuum, right? So the sound waves would transmit through the helmet and then cease. What am I missing?
Sounds vibrations can pass through contacting objects. It's like putting your ear up to a wall to hear what's happening on the other side. That said the sound vibrations you would get from suit to suit would be pretty weak, which is why Bobbie sounds so muffled.
@@andysmith6975 They have shown helmet-to-helmet talking in vacuum a few times before that. Naomi and Holden talked privately outside the ship before their "stripping down" scene in the airlock at the beginning of season 2. Bobbie also talked to one of her Marines this way while their radio comms were jammed on Ganymede.
@@pwaks It’s the main thrust that would cause it to circle faster and faster. If you use side thrust to hold the size of the circle, the main thrust has nowhere else to go. Everyone on board gets squished eventually by the two thrust vectors accumulating.
One Question, have you taken into account that the main engine constantly accelerated the ship for quite a while already and it must have traveled thousands of kilometers per hour in one direction when Naomi set off the thruster? From what I understood, the ship was tilted in its axis and kept the movement from the tilt through conservation of momentum in space. While still moving in the initial direction and then adding acceleration to a rotating vector, could that be the answer? I'm neither a physicist nor do I have a PhD, just an average interested autistic logician with a great imagination, hence asking if that could have been the case in order to make a quick reality check. Cheers!
The only moment in The Expanse that was teeth-grindingly, embarrassingly WRONG was when Bobby recognises Naomi in a spacesuit, and instead of instantly hitting thrusters immediately, they footer around indecisively, completely out of character. Wish they would reshoot that imagining these two were Martian military...
Recalculate it. This time the rotation speed of the craft is relatively small. The direction of the thrust is constantly changing causing the craft to move along a curve. With the proper ratio between the rotation speed and the thrust vector, the craft will move along a circle. Think about an object moving in the gravitational field. You should always be able to mimic gravity with acceleration.
Ok, you are also making some "errors". In the show, the ship was ENORMOUS, and the size of the circle would be determined by the rate of the spin. So, the circle was created because unlike in your example, where the rocket tumbled rapidly, it would have taken one complete circle to complete one rotation. (they would be the same thing). Now, your rocket still did closer to what naomi would have experienced, which would be a sine wave. as the rocket tumbled, it would accelerate forward while pointed forward, and sideways while pointed sideways. This would give it a wobble. HOwever,,, that wobble would only be along a 2d plane if the rocket rotated perfectly parallel to it's trajectory. Instead, the wobble caused by a corner thruster firing, would be a spiral. The image presented to us in the expanse is highly compressed,,, if naomi were going somewhere with an epstein drive, and then induced a tumble at that slow of a rate of rotation,, the spiral would only be perceivable if highly compressed to show the shape. but, actually, it could happen BASICALLY like the show. (since when jumping out of the craft, naomi would remain on the same trajectory as the craft,,, but,, the craft would be accelerating, but,, not very efficiently, since it would be wasting it's thrust. assuming a high specific impulse and low overall thrust, it's imaginable that during the time that naomi would survive without air, the ship could present a navigation hazard for someone hoping to get close enough to her, depending on just how much thrust the ship was under.
I would add that Naomi breaks the thruster nozzle, causing it to continuously fire, not a short burst. We can even observe that in the show. The physics are still wrong, and that little RCS thruster doesn't have anywhere near the power to maintain a 1/3 g thrust (that's what I assume the Epstein main drive was pushing at). Also, SPOILER FOR THE BOOKS: they got the physics of this part right in the book.
In your spinning experiment, you completely forgot the fact that the ship in expanse is way, way larger and heavier and that the thrust from the main engines is immensely high compared to RCS that is only a fraction of that thrust. If you indeed built something more similar in weight and size you would see that the motion was indeed similar to expanse.
It's funny how they accelerate for weeks and month with 0,3g and then use a couple of `hard' 10g manoevers for a bit to change their course significantly. In the books these manoevers take 10 days 'in the juice'.
10 days seems a little excessive. Even at "moderate" acceleration like 5 G, you would only need just a few hours to brake from a week at 0.3 G. A week being enough to travel to any place in the solar system without the flip in the middle.
ok, please look above at Oscar Swida's graph, it looks a lot like your outcomes, depending on the relative translational speed of observer and ship. However, there is also a relationship of Vnaomi to Vship, where she sees circles. If mohat would have jumped out at a different moment, would he not see circles? www.desmos.com/calculator/fmwcghblm0?lang=de
There is no case where Naomi will see the ship follow circles. It seems lots of people are struggling with the physics on this one, so I will put out a video just going through the physics tonight or tomorrow.
I disagree. Spiraling is possible, tho it should have been a very loose spiral. The forward velocity prior to the spin is the horizontal translation across the screen. Then you have to spin the vehicle such that the engine never faces the forward velocity. It isn’t a sideways push on the top, it is an angled push on the top causing a / \ / \ / spin.
You sure she shut the booster off? You can see one of the later shots the side booster is still running. If it was a continuous force the circle would be correct.
@@kedrednael As KSP player... if the hatch is rotating.. it is defacto impossible to dock. (only in Interstellar they had this awesome luck, the center of rotation was exactly in the center of the docking port, then yes you can line up rotations, but if it isn't and you lost control of the ship that is rotating, it's game over for that ship, no docking ever.)
With a little weaker thruster impuls you would get Naomis spin trajectory. Since the main drive is on and the ship being in a slight spin, you get exactly that motion. Dont see why this shouldn't be realistic. Try a weaker thruster impuls, main drive does the rest.
I'm no rocket scientist, but when I saw that episode I felt that she should have been yeeted away from the ship. Controversial opinion; I didn't like this season. Having alot of it take place of earth robbed me of the space setting I got used to. Maybe all of the character development, viewing it from a first person like it probably was in the books, would have it more enjoyable or easier to follow. Like it was frustrating to watch Naomi trapped on a ship, and only having a vague idea of what she was trying to do because we saw it in 3rd person and not 1st person. I just felt that the pacing of the season was very inconsistent. And in the the last 10min of the season finale a lot of important stuff happens that they didn't explain, or spend much time earlier in the season foreshadowing.
The spin was only quite slow, and they showed her helmet rolling away as a result of the spin. I thought that was absolutely great. Though you are right she should have been far away from the ship after she jumped off it. I agree the Naomi scenes were way too slow and hard to understand. I'm quite obsessed with sci-fi and have played hundreds of hours of kerbal space program, and I had no idea what she was doing. For example, apparently the airlock was not fully functional, so every time she used it she lost the air that was inside the airlock. That's why she was marking how many times she went between the hull of the ship.
The acting when Naomi was stuck on the ship was bang on.... Dominique Tipper nailed those scenes when she was holding her breath and fiddling with the Chetzemoka.
I found the stuff with the Mars fleet having worked some deal out with Inaros was pretty well established, leading up to it. I wasn't surprised at all. I didn't know they already had a planet they were claiming though. Just thought that we'd see the Maritans working along side the Free Navy while other Martians would go through the ring to colonize new worlds. Like the way it all turned out, but yes, seems like some things were off with the pacing for the last 3 episodes. Pete Peppers has a good video on the difference between the book and the show and it seems like it would be harder to convey for the show.
@@alistairmerrifield5035 Ya her acting conveyed that she was desperate and exhausted, probably better than if it was read from her POV chapter. But I'm guessing that her POV chapter had her thoughts, and we could follow what she was trying to do better.
like sure the physics are whack but why the forward thruster as in the drive thruster not the adjuster thruster is is still burning wouldnt that cause it to slew or is that an aerodynamic function that requires drag and atmosphere?
The regular spiral is wrong, but Naomi's goal of deterring dock would still be fulfilled
TARS get ready to engage the docking mechanism.
Only if the Razorback still spotted the adrift Naomi, now nowhere near the ship instead of in the center of it's spiral.
In the press leading up to this season, the Showrunner Naren Shankar owned up to this mistake, hinting that there was one episode involving a difficult docking attempt where they fudged the physics a bit
Yea that's probably it!
That's one thing that did confuse me. In the book, the Chetzemoka had multiple engines, and Naomi shut one off. This created a net force on one side of the ship that kept it going in a circular path. Not only that, but the centrifugal force it created was enough for Naomi to feel spin gravity onboard.
Wonder why they changed it.
In the show she can actually feel "the spin gravity". You can see her walking at an angle as well as right after using that hruster when she takes off her helmet it's rolling towards the airlock even though it should stop because it wasn't round. A lot of people missed it because the helmet fact was hard to catch as well as people thought she was walking like that because she was hurt
Also I think they changed it because if in the books it looked like that then ship would jump keep spinning faster and faster because that would be constant force.
I was expecting him to come up with a configuration that would somewhat achieve the helix motion.
@@paxon57 actually constant force is what would be needed to maintain a circular path, although it would have to be constantly perpendicular to the ships current velocity, this could most certainly be achieved by turning off a thruster on one side of the ship, if that force imbalance is enough to keep the ships main engine roughly perpendicular to it's velocity vector it would move in a circle
EDIT:
Shit no you are right, I thought about it some more, a constant force imbalance like that would cause the rotation speed to increase continuously so you still wouldn't get circular motion, so a brief foreign of the thruster could actually have the desired effect, what he showed in this video was the thruster firing too hard causing too fast of a spin, but if he limited the thrust so the ships rotation was slower you actually could get the thing to go in a circle.
I'm supposed he didn't mention that even if the ship fired the thruster just right to get the rotation at the perfect speed to keep the main thruster pointed inwards and the ship going in a circle the scene still would be wrong, when she leaves the ship she would fly away from it at a tangent to the circular path that it is on, she physically could not end up in the center...
In my headcanon the Chetzemoka's main engine bell was stuck on Gimbal lock outside of linear parameters after the side thruster spurted to life.
I mean, the ship would still fly in a circle. It is spinning around its center of mass and the main engine constantly moves the center of mass forward, making it look like the ship is flying in a circle to an observer not locked to the ship.
@@seafighter4 but that's not true... physics doesn't lie.
I mean that sounds cool, but Epstein drive cones don't gimbal. Imagine you're already burning at 10g, and then the drive gimbals. goodbye organs, goodbye crash couch mounts, goodbye limbs
Naomi's ship only made one rotation every minute, in your example it makes a rotation every 2-3 seconds. Makes it kinda hard to compare, the ship just seems to spin around its axis which doesn't look like the growing spiral it should be. But you're correct and I didn't realize the situation in the expanse was wrong on so many levels.
The speed of the spin makes no large scale difference. Since there is no continuous net force acting toward the centre of the circle, the ship will end up flying off on a rather bizarre trajectory.
This would be the expected trajectory, if you are curious! ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
@@RyanRidden shes, its a bizarre trajectory, but she will move in a straight line once she moves off, so she will fly along the ship as it spins around her depending on where she jumps off, again, you're thinking in the wrong frame of reference.
@@RyanRidden couldn't the thrust of the main engine be that force toward the center? As the ship is rotating, the direction of thrust is rotating also.
Totally right IMO. The slow rotational force remain while the non gimbaled thruster continued to fire. This would lead to a circle. In this video the rotation ist way to fast to illustrate this, but if you look closely the circle is there, but smaller than the ship itself. Redo this with much much less impulse from the sideway thruster and yo get your circle.
Love the use of KSP.
I'm so happy you made this vid and it got recommended to me, it's so cool to see a real astrophysicist's take on this show, great vid!
I'm glad you found it interesting!
TBH It is possible to form a full circle orbit with just the main thruster, granted you already applied torque to initiate the turning motion with a side thruster. Imagine it like the satellites, if we ignore the air resistance, there's only one acceleration affecting them, gravity. So if you match your thrust with your turning ratio, you can mimic this motion around a virtual centre. This is something we have practiced in Elite Dangerous. Also, it can be replicated in KSP. For example you might find an asteroid and try to maintain a relatively stable orbit around it by adjusting your main thruster.
It's not easy to get the turning speed and main thrust force right, but it's possible in theory. You only need to create that centripetal acceleration.
However, in Naomi's case, if Naomi gets out after we have obtained this orbit, she would have to intentionally push herself towards some range of direction with some amount of force in a range to stay inside this circle, and even in the best case scenario, this entrapment would be temporary, since she wouldn't be able to adjust her direction of motion after jumping.
I'm starting a petition to get that kerbal-head-collision 'bong' sound added to KSP!
Yeah, it felt wrong and my inner self knew it. My full attention came from the circling graphics, immediatelly "No way!" reaction.
0:20 well yes, but my issue with that scene is that the corkscrew is going around the ships travel path, we only saw naomi activate one thruster so no matter which side it was on it should have made the ship face towards then away from the travel path and not circle around it. for it to get to the point we see in the show she would have needed to activate one then activate the opposite one to stop the movements at the right time to get it to stop ~90 degrees perpandicular to the travel path then activate a third one to get it into that corkscrew spin.
Oh and naomi wouldnt have just stopped in the centre of the corkscrew, she wouldnt of even gone inwards, the centrifugal force of the spin would have thrown her away from the ship unless she somehow timed it right and with enough force threw herself in just the right direction to overcome this centrifugal force but even then she would just come out the other side as nothing is holding her inside the ships corkscrew.
I think you are sort of wrong. I agree she would get flung away. But you can still see it as a circular path if you have the correct frame of reference, like an imaginary point that the ship is pointing and accelerating towards as it is rotating around it, i.e. the center of the circular path, like at 4:39. The speed that the ship already has relative to earth or whatever doesn't matter. If it's rotating at 1 rpm, don't see why the acceleration in any given moment wouldn't get canceled half a period later when it's pointing in the opposite direction.
Memories of early kerbal rendezvous come to mind where I realized continuously pointing towards the target and slowly burning constantly can make it so you don't get any closer, you just sort of orbit it. Now if it's a ship you're targeting in the center of that path, you need the correct relation between rotation and acceleration for it to be circular relative to that target ship. But the center of the path can be an imaginary point. If your ship spins very fast and burns very slowly, that point is closer to the center of mass of the ship, but the slower you rotate the further in front of the ship that point will be.
This is the correct answer.
Maybe the ship was oriented wrong for that - I don't know because I haven't seen the scene yet - but even if it is, Dr. Ridden should have at least mentioned it.
It's really obvious when you know the net force needs to be towards the center of the circle and the only force is the main engines: F(centrifugal) = F(thrusters)
You just need the side thrusters briefly to start the ship rotating in sync with the circle you want.
And as you say, just like that picture at 4:39 - how can he miss that?
There was a 3D display of the spiral and fwd motion (like a spring) of Naomi's ship inside the Razorback...
Also the one time firing of the side thruster will certainly not sustain a circular motion.
Naomi jumping out of the ship would be moving tangentially away from the circular trajectory (if the ship could indeed moved in spring like trajectory as the display showed in the razorback)
Lastly if they(Alex and Lady Tank) already spotted Naomi outside the ship in mid of the spiral spring, they could have easily entered the spring from one of the 2 openings... There was no need to try the interstellar like docking move to get Alex killed. May be it was a scientifically inaccurate hustled move to get Alex out of Expanse...
I read some news that Alex dying was an edit made to the story as they were letting go of him in real life...
Is there a way, Razorback's or Naomi's gravity interect with Chetzemoka's gravity and help sustain that curcular motion?
Still I feel in that case, Naomi should be orbitting the Chetzemoka and not the other way around...
Your quite right, even if it was possible, once Naomi jumped she would no longer have the centripetal force acting on her to be contained in the spinning system.
The gravitational pull of all objects in that system are way too small to make any noticeable impact. The main engine would have been burning at around 0.3g which is much larger than any other force in the system.
Could a slower rotation put it in something closer to a circle, or at least a spiral?
Rotation speed will make no significant difference. This would be the expected trajectory, if you are curious! ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
It absolutely was a late change. They edited him out of some scenes and created a death scene in post.
Alex dying irritated the shit out of me. This is a case of knee-jerk 'Social Justice'(tm). I am NOT defending the actor's "supposed" activities, but Alex Kamal (THE CHARACTER) is beloved AND integral to the story. If Arjun (Chrisjen Avasarala's husband) could be recast due to scheduling issues with an actor...a recast due to supposed actions taken by Cas Anvar (the actor) AFTER SEASON 5 would have most likely been accepted by the fans to keep the continuity and move on. The WAY this was done was complete and total horseshit, and pretty obvious that it wasn't done organically as the editing of the final scenes (as well as his death scene) were garbage. Oh well. (Critical Drinker voice).
RIP Mohat Kerman
Edit: before you comment about the choice of thrust to induce rotation look at this: ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
Hey there! Could you answer me a question that I - for some reason - couldn't find a definitive answer to? How long would it take accelarating at 1G (I presume that's close to how quickly they accelerate/decelerate in the Expanse) to reach let's say.... 90% of the speed of light?
Essentially my question arises from the idea, that if your method of creating gravity was using continuous 1G acceleration, first off, using conventional fuels, you'd empty the tank REAL quick, but let's say that's not an issue, how long could you travel, before reaching super fast speeds. Where even time dilation starts to become at least somewhat noticeable.
@@gregsomlai297 The speed of light is 2.998e^8 m/s, 1g is 9.80665 m/s^2. 2.998e^8/9.80665 = 30570000s, 509500 minutes, 8492 hours, or 354 days. So about 320 days to reach 90% c at 1g.
@@thentil Thank you! Yeah, that's what I figured, it's just that I've seen someone calculate it screwing up an order of magnitude, making it a month or so. But still, that's pretty damn crazy. Wouldn't take that long...
In the first example, the ship does end up in a path that is analogous to a moon orbiting a large planet: the moon spirals while the planet goes in a "straight line" (or whatever orbit ot happens to be on).
If the rotation was much slower than your example, (which is plausible based on the scene) wouldn't the ship appear to take a circular path in a reference frame similar to the planet in my analogy?
@@gregsomlai297 That other person probably took time dilation into account. Orgborg did not.
What makes problems like this hard are reference frames. After one full rotation of the ship, all the thrust vectors cancel out.
If you set your reference frame to the average velocity of the ship, then the ship will appear to be moving in a circular motion.
Like with with any object moving in a circular motion, if a passenger detaches from the ship, she will be flung away from the center of the circle.
From Naomi's perspective, she would be floating in space as the rocket spirals away from her.
The other big physics mistake in that scene was that she wasn't incinerated by the Epstein drive when it came around to point at her :)
I'm hoping that the success of the Expanse and The Martian will make it clear to movie/TV producers that there is a real appetite among the public for more realistic sci-fi and could lead to a fictional series where they actually do the science justice and don't compromise the realism for cheap thrills.
First time SAS was OFF, and on the second time it was ON.. u can even see the main drive correcting itself. Try again, like the first config, but with a weaker and shorter side booster and with the SAS OFF.... *SAS = When active, SAS will provide input to stability systems to dampen craft rotation and, depending on capabilities, lock onto a specific orientation. The user can override the current rotation for any axis. Since it controls heading, it can be extremely useful for lander missions. When active, the SAS itself doesn't drain electricity, though reaction wheels may continue fine-tuning even in space. It will utilize all active control systems to achieve this, like the user would by pressing the keys.
Whoops I missed switching it off in that recording, though it doesn't make any difference to the end result. As I said in the video the net force must act continuously, which no burst can produce.
Can u try again with SAS off, and with a shorter RCS burst? Because, in my head, if you put a rocket with locked gimbal main engine and then start a rotation moviment, with the RCS, with no force to stop the rotation, it will make a spiral as in the series.
No need to test in KSP since we have the power of mathematics! I ran through the calculation, and this is the path you would expect from the scenario depicted in the show: ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
Your wonderful illustration of the ship’s actual trajectory is a type of cycloid, which would be an ellipse in an alternate frame of reference. Perhaps the computer graphics aboard the Razorback were crunching this? Eh? 😏 What bothered me far more was that Naomi **jumped straight into the frickin drive plume!**
The Epstein drive is more efficient. The nozzle must be very effective at directing all the exhaust fairly straight.
Actually this guy is wrong in almost every way. A short thrust does in fact induce a permanent spin, inertia means it will continue to spin until some force stops it. There is no friction to stop it. If the thruster were to fire constantly, the spin would accelerate until centripetal force pulled either ends of the ship apart. A short burst means there is a constant, unchanging rate of spin. The spin in the books and in the show is relatively slow at maybe 1 spin every 40 seconds. Not 1 every second or higher as shown in this video. Add constant thrust perpendicular to the the axis of spin. This constant thrust will not stop the spin or slow it down. It will drive itself in a circle, inducing artificial gravity both along the line of constant thrust and perpendicular to it. Also before spinning, it was accelerating along a path dictated by orbital mechanics, its velocity constantly increasing. After the spin begins it is no longer accelerating, because as it goes in a circle it cancels the acceleration at the point opposite on the circle. This means it is orbiting on a ballistic trajectory along a path dictated by its velocity when the spin began.
If you were to view this from a point in space that wasn't moving relative to the sun, the ship would be flying in an overlapping corkscrew pattern. If you were going along the same orbit as it, it would look like it was flying a perfect circle. It really depends on your frame of reference
Naomi being in the middle is wrong though.
@@Skunkwurx , Dr. Ryan made a subsequent video in which he corrected himself, and I accidentally responded to this one instead. Your “overlapping corkscrew” path was the cycloid I spoke of, which he illustrated in that video. For some reason his cycloid was very tall, which led me to believe that the alternate frame would yield an ellipse instead of a circle - I just trusted his math. Though I can’t think of an intuitive reason why it would be elliptical instead of circular.
@@Skunkwurx some people presume without evidence, that the short thrust was sideways on the nose when it may have been another angle.
Yay! I was actually right in my assumption that a single thruster firing a short burst at the front of the ship wouldn't cause the ship to enter a barreling motion. While I didn't play this out in KSP, the Jebediah in me thought this wrong from the get-go.
Actually this guy is wrong in almost every way. A short thrust does in fact induce a permanent spin, inertia means it will continue to spin until some force stops it. There is no friction to stop it. If the thruster were to fire constantly, the spin would accelerate until centripetal force pulled either ends of the ship apart. A short burst means there is a constant, unchanging rate of spin. The spin in the books and in the show is relatively slow at maybe 1 spin every 40 seconds. Not 1 every second or higher as shown in this video. Add constant thrust perpendicular to the the axis of spin. This constant thrust will not stop the spin or slow it down. It will drive itself in a circle, inducing artificial gravity both along the line of constant thrust and perpendicular to it. Also before spinning, it was accelerating along a path dictated by orbital mechanics, its velocity constantly increasing. After the spin begins it is no longer accelerating, because as it goes in a circle it cancels the acceleration at the point opposite on the circle. This means it is orbiting on a ballistic trajectory along a path dictated by its velocity when the spin began.
If you were to view this from a point in space that wasn't moving reletive to the sun, the ship would be flying in a corkscrew pattern. If you were going along the same orbit as it, it would look like it was flying a perfect circle.
Another problem was naomi only did one maneuver which should have set the ship to spin in a way to speed up and slow down but it shows the ship doing a cork screw which should have took 2 maneuvers. She was traveling in the wrong direction.
Mohat Kerman....
We salute thee!
for the rescue, you should ask matt lowne and his blunderbirds!
The KSP ship is spiraling the moment the thruster gives it rotation. Any body separating from the ship at its center of mass will stay next to the ship (or on its larger spiral path, if you rotate slower). Naomi's jump exited the ship in the direction of the rotation, putting her inside the spiral, traveling (slowly) along the diameter of the spiral. Naomi "fell" towards the rear of the ship at 0.3g (the ship's acceleration), so it moved away from her, but will eventually circle back to the place they separated.
The path depends on the initial forward speed, speed of rotation and the force of acceleration of the back thruster. It wouldn’t make the circles like in the movie, but there is a speed of rotation that would make some kind of spirals moving forward with inilial speed. Naiomi should be left out of the spiral with the initial ship speed before rotation starts I guess
Thanks for doing this! I was bugged by this when I saw it and had some discussions on some other vids. It would be nice to have a trailing line to see how the ship was still moving through space to demonstrate what the show was portraying with it's display for comparison.
The script implied that the ship was "in a spin" but then the graphic shows it in a spiral.
It's unlike the show to get the physics in space majority wrong, so I wonder if there was a miss communication between the effects team and the show runners that was then too late to fix.
In your Kerbal model the perpendicular thruster was very powerful and in fact I think too powerful. In the episode the thruster was clearly pretty weak and I think that's important for the model. To me it seems like what Naomi did was set her ship into a fairly slow tumble. With the main drive burning away at an unknown thrust level but likely less than 9.8m/s/s (because Belter ships likely wouldn't want to burn at 1G ever) I think it's possible for the ship to trace a spiral path as depicted in the show. That would of course likely gradually grow over time as the main thrust slowly ate away at the rate of tumble. I think the key is the rate of tumble. The ship needs to tumble slowly enough for the main thrust vector to precess over time so as to put the ship in a spiral. What I'm saying is your Kerbal ship tumbled too fast because you used too much thrust. Model it again with less than 1 g of main thrust and a much slower tumble rate and see what happens.
If you slow down the angular velocity the ship will describe a circular pattern around a hypothetical point on the orbit at the time of side thrust ignition(note that the orbit is constantly changing when thrust is applied), the only error was on the plot at 1:18 where the spaceship is pointing wrong, but if the immage is generated by a computer thar shows instant velocity than it would be a correct representation of data.
BTW if Naomy didn't run outside the ship she would bump on the ship st the next rotation
If she just released herself softly, she would travel a straight path leaving the circle created by ship's circular motion with the ship's circular velocity at that time.
without a centripedal force, the centrifugal one doesn't seem to exist
Your spin radius was along the center of the craft, in the show it was roughly a kilometer across because the angular thrust applied was much much smaller than what you are doing here
The corkscrew trajectory, shown in the display of the Razorback, could make sense, if it was relative to the Razorback, who at the time was in the process of matching its trajectory (and hence velocity) with the ship of Naomi.
It's an interesting idea that they could be in similar reference frames, however this is not the case as we see the Razorback is still on a normal, fairly linear trajectory, while the other ship is very non-linear.
This would be the expected trajectory, if you are curious! ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
The physics in The Expanse works selectively. When Roci shot Pela by a disarmed torpedo they found later this torpedo was stuck in a board. But at the moment of collision the torpedo should have 20 km/s of relative speed (accelerated at 100G for 20 seconds). You know, artillery shells penetrate heavy armored tanks at a speed of about 1 km/s. So the torpedo had to penetrate all the ship decks like heavy railgun projectiles and completely destroy Pela and crew only by kinetics.
Love this although you sent your poor guy into the sun! My son loves Kerbal and I fully trust him if he ever needs to plan a launch and sustainable orbit . Please keep making videos during the long desert between season 5 amd 6 . Also glad to see some ads w your videos yay! Congrats on YOUR expanse(ion) !
KSP is an amazing tool to help learn about physics and orbits. I first started playing it while I was doing my undergrad physics courses. Although I had a good idea of the theory putting it to practice broke my brain in the beginning!
Don't worry, I keep making videos, mostly on whatever aspect of science catches my interest. That said these last view videos on the Expanse has really made a big impact, its quite amazing!
You talk much faster and better paced in this video. Thank you! And it's a very interesting one too!
Your thruster was too strong and your main engine wasn't strong enough. Also the frame of reference is important. She would get left behind like in your example but that's because the arc of the ships spin is like thousands of miles in diameter and would take a while to turn around and come back.
In your example, the camera is fixed to the center of mass of the rocket, so obviously you wouldn't see anything else than a ship spinning around itself. The camera is spiraling with the ship. Might as well just shut the main engine down for a similar conclusion. You should've left another kerbal floating outside just as you started the spin for a valid point of reference.
I agree that Naomi should've been flung outside of the spiraling ships trajectory, but the ship definitely would've spiraled around a point in space that moves in the approximate direction that the ship was travelling before the spin was induced.
I have a question:
If the ship is spinning around, shouldn't after a single spin the net force on the space ship = 0 (velocity is still large, but acceleration is 0)?
When the Kerbel jumps off the space ship, shouldn't his net force (acceleration) also = 0Why doesn't the ship and the Kerbal travel at effectively the same velocity?
The second question:
The ship would have a net force / acceleration of 0 at the END of each rotation, but during the rotation, they would have an accelation in the direction of the ship (which is in a circular motion), therefore *Compared to the previous velocity* , wouldn't it travel in a circular path from the perspective of the Kerbal?
1 = the ship is still accelerating from the rocket engine. Once the Kerbel is out it will stay at current velocity and the ship increases its. So Kerbel is left behind.
2 = The ship (first example) are traveling in a circle, but due to high initial velocity there cercal is so large you can't perceive it on small distances like we see in the vid.
In the second vid the ship's velocity has translated a few degrees to the left but as there is no continuous course (like spin) to create a circle around a common point, it is still traveling in a straight line just adjusted a few degrees to left.
Without watching it, you can do in space whatever you want manouver-wise if your RCS Thrusters are strong enough, have inifnite Fuel and if your Main Engine has infinite Fuel and enough Thrust.
Star Citizen manages to do it quite well, your RCS Thrusters are strong enough to "fly" like an Airplane.
Hello Physics major here.
TLDR: if you spin slow enough so your main thrust always points outwards to your circular path you can fly in a circle.
What happed in the show is very possible and not inaccurate to the physics at all. The key is getting the correct rotation speed relative to your thrust. In your experiment you conducted in KSP you spun up your ship much faster then Naomi with the Chetzemoka. It is possible to make a perfect spiral pattern if your rotation speed is such that the engine is always pointed tangentially to your path you would travel in a perfect circle. I admit that you would need to time the thruster perfectly to do it right, however unlikely it is possible. one cavoite to this is that Naomi would probably be just flung outside of the path due to centrifugal force as soon as she stepped out of the air lock so that's one thing. Also the reason the sip in KSP appeared to be moving in a straight line and just spinning was because ksp always follows the reference frame of whatever ship your focused on, while in reality the ship was flying in a curly loopy pattern that would look like the way you draw a spring in 2D.
Its kind of like how an orbit works but gravity is always pointing tangent to your path by default
great vid otherwise.
(If I'm wrong please point it out, I love to learn form my mistakes)
After nose force is applied and rocket begins to spin around its mass center, rocket will no longer accelerate. That's because main thrust direction will rotate along with the rocket, so the speed of the rocket at the end of each rotational cycle will be equal with the speed rocket had before it started to spin.
If the passenger jumps out when tip of the rocket is oriented in the direction of rocket initial velocity, passenger will continue to move in the same direction with the rocket + the perpendicular speed vector Naomi had right before the jump. Jumper will get farther apart from the rocket (carried by the kinetic momentum of the jump) but rocket and jumper will have almost the same speed from an outsider's perspective (speed of the rocket being obviously far greater than the speed generated by Naomi's run).
Out of curiosity, is there a way to replicate the path observed on the show?
Let’s assume that there may be some autopilot functions involved that reacted further after Naomi’s control input. The “spinning in circles” seems like it could have some utility as a “parking” pattern where constant gravity is maintained by a constant engine burn (or by just being a functional “centrifuge drum”).
Wouldn’t be shocked to find that aberrant control inputs force the autopilot into a “safe” holding pattern where relative forward motion is stopped.
if instead of a single rcs burn you'd do two burns to point the ship sideways and then have a leak constantly venting a small amount of air at a perpendicular angle, that might result in a spiral, i think.
you would then have to jump out of the ship in such a way that you'd end up inside the circle, because otherwise you'd either get crushed (exiting at the front) or burned (exiting at the back) or first crushed then burned (exiting on the wrong side).
There is another aspect to the maneuvering of a spacecraft that you did not consider. Reaction wheels, that generate torque onto the main axis. Combine this with thrusters and you can in fact “fly in a circle”.
In the expanse it was a smaller thruster and likely was offset to be used in combination with other thrusters
Wouldn't it be possible to create a circular trajectory by giving the ship a specific angular momentum such as the thrust force is always pointing at the center of the circle?
Is that a ground hum on the microphone thoughout the video, or part of the background music? Makes this hard to watch.
KSP Hangar music
I think that spiral motion is possible.
You assumed that the ship was burning along it's velocity vector, but what if it was changing course?
Imagine the 3D cooridnate system where Z means up/down.
Now let's say that velocity vector was towards Y+ axis but ship was changing course so it was thrusting at 90 degrees towards X+ axis. Let's say that the thruster that fired was aiming at Z- axis and put the ship into a slow spin (in your video spin was wayy to fast).
In that case I think ship would start moving in a spiral like in the show and if Naomi jumped out from the side facing inside of that spiral she would be inside of it (at least for some time unless she made perfect calculated jump to cancel out the velocity offset :p )
Sweet. Lining the kerbal up for the glancing blow must have been a pain in the azz ;~)
It took a few takes!
If the spin rate was sufficiently slow, and only in a single axis, and the thrust sufficiently high, yes it would spin around in a circle with respect to an observer moving at the same initial speed, though Naomi would most definitely not end up in the centre of that circle, rather she'd be flung out away from the spinning ship (and probably burned up in the drive plume, ouch). The thrust vector is in one direction in relation to the ship, but as the ship is spinning, that thrust vector is changing direction with the ship as it spins around, ergo a centripetal force. Key point is, though, it would not be a corkscrew as shown in the show, because the initial direction was in the direction of travel, and thus the rotational axis must also cross the direction of travel.
Why is this video unlisted and why i can still see it?
The TV has been known to make some mistakes when the physics are left up to the effects artists.
If the ship is rotating while the engine is burning, the ship acceleration should basically cancel out. It goes forth and back... while following the linear velocity it had before going into torque. But once torquing it doesn't accelerate/de-accelerate anywhere anymore.
When you eject a person, there may be a difference of the current velocity the ship had at the moment of exit vs. the forward and backward acceleration the ship is doing while it is spinning. So I'm not yet totally convinced that a scenario as seen on screen is physically impossible by one KSP simulation.
I don't know why, but I didn't get from the show that Naomi's ship was circling (even though it's clear on Alex's screen). I completely missed it. I just assumed she set off a thruster and it put the ship into a spin so the Razonback couldn't dock with it. Strange that they wrote the show that it put it in a circular path. I mean, I'm not a physicist (took Physics 101 at University but nothing more) but I would have never thought firing a random thruster, no matter where it was on the ship, would make the ship circle. Thanks for explaining everything. And rest in peace good Mohat.
Yeah, with the ship tumbling it would have been impossible for Alex to doc, depending on how the airlock is located. I think one of the best docking scenes is in Interstellar. Mindblowingly crazy.
What about the main drive thruster in your first example? Since it is continuously firing what about about the huge influence it will have on the direction of the craft?
The main drive doesn't shut off on the show either. If the main drive was off in the first case, then the ship would have just started spinning around the centre of mass as it continued at constant velocity.
if you fired the thruster in a way that left the ship spinning so it always faced 90 degrees to its theoretical path in a straight line and kept the rocket going at low thrust, that would produce a small circle wouldn't it?
In your demonstration, you fire the thruster at an unknown length of time and newtons.
Think of the ISS, it is always facing the earth in a particular way like the moon. So when the ISS need to speed up they fire their thrusters and increase their apoapsis. As their spin rate is relatively slow unchanged from the thrust they don't need to adjust.
Could you try this please?
Now here's the thing though. Reduce that massively oversized and overpowered side thruster of yours by a factor of 100 or so, so the rpm is like 0.5 and have the kerbal slightly push off from the opposite end of the thruster. Something tells me that's gonna be a bit more realistic.
I cover the math in more detail here: ua-cam.com/video/vBkZ6-5vHlY/v-deo.html
Okay, that's fair enough.
I am just a petty simple earthbounded engineer. So Sorry if miss some of my physics class in Uni. Q: What if we assume, Naomi's ship flew in a straight vector with a slight rotational motion around the flight axis? That could explain the spiral. Can some one point out if I am wrong/right here?
I'll disagree with you on this.
I might be completely wrong so correct me please.
The mass of your ship is far to low for the thruster you use. If you alter the forces on the ship, mass of the ship and the burst of thrust, so the ship has a spin of .5 rpm or .3 rpm while having a continuous .2g acceleration from the main drive, you will have a resulting motion much closer to what we see in the show.
The part where Naomi is in the middle of the spin still doesn't work.
Are you able to do a video on the decoupled physics in star citizen during the upcoming free fly event (try the game for free) ?
Their are two modes of flight in game, one has the computer control your thrusters to try to determine where it thinks you want to go and apply them that way. The second mode is basically manual control by the pilot. After watching this video on the expanse I wonder if star citizen does a better job. One thing people manage to learn to do in dogfights is circle their enemy while firing at them, a little like what the expanse did here.
Ok. So my question is, is there a scenario you could set up to reproduce a circular motion as depicted?
All that's needed to create circular motion is a consistent force directed perpendicular to the direction of motion. A spinning ship can't produce that since the direction of the force is always changing around the ship.
2:38 the ship seems to follow a straight line despite the main engine firing and the ship rotating. We should see the ship wiggle left and wright from the unlucky Kerbal's point of view, should we not?
Probably has more to do with the thrust to mass ratio. The thrust is too low to perceive change in velocity given the frequency of rotation. Try that with a mainsail and a slower rotational speed, then you should see quite a difference.
Your test does not reproduce the conditions of the show. Clearly, the unfortunate ship was much heavier and the main drive very powerful compared to the thruster that only induced a slow spin.
Still,a small burn from your thruster would just change your course slightly, less than a degree to the right or left. It wouldnt induce flying a circle.
You would need continous fire from engines and thrusters to fly a perfect circle, which would burn a shit ton of fuel, your main engine would need to be at almost zero thrust to not flly off .
@@Intrepid17011 What leads you to the conclusion the ship would stop spinning without continuous thruster fire?
@@Intrepid17011 that’s not true. You induce a spin by firing a thruster that results in a force component perpendicular to the axis of the spacecraft and offset from the center of gravity. With a continuous firing of the thruster you would keep increasing the amount of spin, probably until the occupants are transformed into chunky salsa and continue to increase until the spacecraft came apart.
ksp is amazing, but you should really increase the ambient lighting slider when trying to record pics/vid away from kerbin :)
You're quite right there, I only noticed how dark it was once I recorded everything!
The rate of spin in the show was much smaller so the spiral should occur, but naomi would still be flung out abet at a lower speed.
Considering you dont know the mass or how much thrust is produced by the ships rcs thruster or whether or not it is using any gimbal, this isnt an very accurate experiment. I get what your trying to do but it would have been better to see what it would take to make it happen. It is possible, after all, if the correct forces are applied. Now as far as her staying in the middle, your right lol. She would need to be tethered to the thing or something for that effect. Love the use of KSP though.
May be that your initial main engine burn was too strong ?
Did you try some other variation of parameters to get somewhat similar spin to one that happened in the show?
The result comes out the same since the nose thruster only introduces torque around the centre of mass. The ship will always end up spinning around the centre of mass, and won't reproduce what we see in the show.
@@RyanRidden noooo... I just want this show to always be accurate :D
You're ruining that here haha
@@dredeth sorry! Overall it does an incredible job.
@@RyanRidden if a ship had thrust constantly sent out in a circular motion (engine orbiting the ship and thrusting outwards) the ship would clearly take a circular path
your spinning ship seems to have no thrust, only momentum. that engine is spinning around quite quickly, surely it could result in a spiral if thrust is large enough compared to initial momentum
if we think of the length of Naomi's spiral as the direction of initial momentum, the spiral could result if during her maneuver the engine became perpendicular to initial momentum, and spinning motion can result from sideburst as there is no friction to stop the spin; engine acts as though it is orbiting the ship as per first example here, resulting in circular motion of ship if thrust is large enough vs spin speed. . .
Now I'm just sitting here wondering if you can recreate Naomis Space walk in KSP. [Book Spoiler coming] Or Bobby sufing a torpedo.
The space walk is pretty easy to do since it was a straight line between ships, but unfortunately their helmets stay locked on in space, so no true recreation is possible there.
@@RyanRidden I'm not too familiar with the game, but I thought there is Oxygen supply, so couldn't you force one minion to run out of oxgen and then do the walk? On the other hand these are little green aliens so I'm not sure how well they translate to human biology. And you probably also can't do the breathing out and injecting yourself with hyoeroxygenated blood parts.
@@Lionfire1998 I think with mods these sorts of things are (probably) possible, but in the vanilla game, the Kerbals only seem to need a seat (and not too much heat) to survive indefinitely.
@@Karsaroth In a enclosed cockpit kerbals will live indefinitely. If they are outside with just a suit they will last five years. Clearly kerbal suit recycling technology is quite advanced.
You're definately wrong on this one, ship in the expanse was turning slowly, angular momentum will keep the ship turning unless a correction thrust is applied. Thrust from the drive combined with the ships rotation would cause a chiral deviation from it's original flightpath.
Here the ship is simply spinning like a top. While in the show it takes minutes to complete a rotation.
Edit: Thinking about it a little more the thrust would have to be offset from the centerline to rotate the ship in this manner, otherwise the deviation will be sinusoidal.
Hold on now: Your first Kerball example spins (tumbles?) in a way that appears identical to if it's main thruster were off, passively somersaulting end over end, yet it's main engine is burning the whole time. Your pencil analogy fails to account for the constant push from the ... eraser. Without a correcting counter directional thrust to stop the axial tumble, this should cause it to travel in a circle! Though no, there would be no reason for Naomi to stop in the center of the circle. What am I missing?
I dont get it. In the first case the rocket is rotating with the main thrust still active. Wouldn't that count as the starship doing circles? Very small circles but I guess that if you would to adjust the lateral thrust to be a lot weaker, it would rotate slower and so result in a circle with a bigger radious.
isnt that thruster on your ship to strong?
My new PC with upgraded graphics card arrives tomorrow. Gotta dust off the old KSP!
How could we hear Bobbie's voice through the space suit when sound requires a medium to travel through? Outside of the suit is a vacuum, right? So the sound waves would transmit through the helmet and then cease. What am I missing?
Sounds vibrations can pass through contacting objects. It's like putting your ear up to a wall to hear what's happening on the other side. That said the sound vibrations you would get from suit to suit would be pretty weak, which is why Bobbie sounds so muffled.
Thank you. I wasn't thinking that the helmets were touching. Thanks for clarifying and for the super interesting content that gets people thinking.
@@andysmith6975 They have shown helmet-to-helmet talking in vacuum a few times before that. Naomi and Holden talked privately outside the ship before their "stripping down" scene in the airlock at the beginning of season 2. Bobbie also talked to one of her Marines this way while their radio comms were jammed on Ganymede.
@@krbkrbkrbkrbkrb And Holden and Drummer when she wanted him to tell Naomi she was sorry she tried to kill him, but not to him... LOL.
I wonder if you could deconstruct Alex’s slingshot around the Jovian moons in season 3?
Wouldn't a constant lateral nose thruster burn result in the circle?
It would just spin the ship up faster and faster around the centre of mass.
@@RyanRidden Even under main thrust?
@@pwaks It’s the main thrust that would cause it to circle faster and faster. If you use side thrust to hold the size of the circle, the main thrust has nowhere else to go. Everyone on board gets squished eventually by the two thrust vectors accumulating.
One Question, have you taken into account that the main engine constantly accelerated the ship for quite a while already and it must have traveled thousands of kilometers per hour in one direction when Naomi set off the thruster? From what I understood, the ship was tilted in its axis and kept the movement from the tilt through conservation of momentum in space. While still moving in the initial direction and then adding acceleration to a rotating vector, could that be the answer? I'm neither a physicist nor do I have a PhD, just an average interested autistic logician with a great imagination, hence asking if that could have been the case in order to make a quick reality check. Cheers!
The only moment in The Expanse that was teeth-grindingly, embarrassingly WRONG was when Bobby recognises Naomi in a spacesuit, and instead of instantly hitting thrusters immediately, they footer around indecisively, completely out of character. Wish they would reshoot that imagining these two were Martian military...
Brilliant one again.
Recalculate it. This time the rotation speed of the craft is relatively small. The direction of the thrust is constantly changing causing the craft to move along a curve. With the proper ratio between the rotation speed and the thrust vector, the craft will move along a circle. Think about an object moving in the gravitational field. You should always be able to mimic gravity with acceleration.
Rotation speed makes no difference
My mistake. The rotation speed would only define the radius, but this would be a circle (in this reference plain)
You better get Jebediah out there to save them!
I think you're neglecting the fact that the main drive is still burning.
The show never said it was a perfect circle. One character said "circling" conversationally and we got a simplified diagram (like most in the show).
Ok, you are also making some "errors". In the show, the ship was ENORMOUS, and the size of the circle would be determined by the rate of the spin. So, the circle was created because unlike in your example, where the rocket tumbled rapidly, it would have taken one complete circle to complete one rotation. (they would be the same thing). Now, your rocket still did closer to what naomi would have experienced, which would be a sine wave. as the rocket tumbled, it would accelerate forward while pointed forward, and sideways while pointed sideways. This would give it a wobble. HOwever,,, that wobble would only be along a 2d plane if the rocket rotated perfectly parallel to it's trajectory. Instead, the wobble caused by a corner thruster firing, would be a spiral. The image presented to us in the expanse is highly compressed,,, if naomi were going somewhere with an epstein drive, and then induced a tumble at that slow of a rate of rotation,, the spiral would only be perceivable if highly compressed to show the shape. but, actually, it could happen BASICALLY like the show. (since when jumping out of the craft, naomi would remain on the same trajectory as the craft,,, but,, the craft would be accelerating, but,, not very efficiently, since it would be wasting it's thrust. assuming a high specific impulse and low overall thrust, it's imaginable that during the time that naomi would survive without air, the ship could present a navigation hazard for someone hoping to get close enough to her, depending on just how much thrust the ship was under.
I wish there was a good mod for showing your path of flight.
I would add that Naomi breaks the thruster nozzle, causing it to continuously fire, not a short burst. We can even observe that in the show. The physics are still wrong, and that little RCS thruster doesn't have anywhere near the power to maintain a 1/3 g thrust (that's what I assume the Epstein main drive was pushing at). Also, SPOILER FOR THE BOOKS: they got the physics of this part right in the book.
In your spinning experiment, you completely forgot the fact that the ship in expanse is way, way larger and heavier and that the thrust from the main engines is immensely high compared to RCS that is only a fraction of that thrust. If you indeed built something more similar in weight and size you would see that the motion was indeed similar to expanse.
Weight makes no difference to the end result, no consistent force is applied toward the centre of the circle.
@@RyanRidden of course you're right. I did not realise that they said that the ship kept flying in circle but rather in a spiral flying away
Damn These real Life physics
It's funny how they accelerate for weeks and month with 0,3g and then use a couple of `hard' 10g manoevers for a bit to change their course significantly. In the books these manoevers take 10 days 'in the juice'.
10 days seems a little excessive. Even at "moderate" acceleration like 5 G, you would only need just a few hours to brake from a week at 0.3 G. A week being enough to travel to any place in the solar system without the flip in the middle.
Thanks a lot for the explanation. It is a bit counter-intuitive, but with the explanations, now better understood.
ok, please look above at Oscar Swida's graph, it looks a lot like your outcomes, depending on the relative translational speed of observer and ship. However, there is also a relationship of Vnaomi to Vship, where she sees circles. If mohat would have jumped out at a different moment, would he not see circles? www.desmos.com/calculator/fmwcghblm0?lang=de
There is no case where Naomi will see the ship follow circles. It seems lots of people are struggling with the physics on this one, so I will put out a video just going through the physics tonight or tomorrow.
haha oh those poor Kerbals
I disagree. Spiraling is possible, tho it should have been a very loose spiral.
The forward velocity prior to the spin is the horizontal translation across the screen. Then you have to spin the vehicle such that the engine never faces the forward velocity. It isn’t a sideways push on the top, it is an angled push on the top causing a / \ / \ / spin.
You sure she shut the booster off?
You can see one of the later shots the side booster is still running. If it was a continuous force the circle would be correct.
Since she broke the valve, it should have fired until it ran out of water. However long that might have been.
Bobbie said there was a "short burst" from the thruster.
Sci-fi, science AND jazz and 3D modeling! Are you my soulmate? :)
Your jawline is stronger than my marriage
I swear to god I though she fired the thrusters to keep the spinning in a spiral... for whatever reason. Why did she even do that?
So that she could jump off the ship, or she would be disintegrated due to the heat of the epstein drive.
I thought she wanted to make it impossible for anyone to dock. Even Bobby didn't want to dock to the ship when it went into that spiral.
@@SergioBQ87 maybe. i kinda found that whole scene with her on board confusing as hell.
@@kedrednael As KSP player... if the hatch is rotating.. it is defacto impossible to dock. (only in Interstellar they had this awesome luck, the center of rotation was exactly in the center of the docking port, then yes you can line up rotations, but if it isn't and you lost control of the ship that is rotating, it's game over for that ship, no docking ever.)
With a little weaker thruster impuls you would get Naomis spin trajectory. Since the main drive is on and the ship being in a slight spin, you get exactly that motion. Dont see why this shouldn't be realistic.
Try a weaker thruster impuls, main drive does the rest.
Thrust power makes no difference to the result. Here is the expected path ua-cam.com/users/postUgz4-IE6-H6b_o5Ootp4AaABCQ
I'm no rocket scientist, but when I saw that episode I felt that she should have been yeeted away from the ship. Controversial opinion; I didn't like this season. Having alot of it take place of earth robbed me of the space setting I got used to. Maybe all of the character development, viewing it from a first person like it probably was in the books, would have it more enjoyable or easier to follow. Like it was frustrating to watch Naomi trapped on a ship, and only having a vague idea of what she was trying to do because we saw it in 3rd person and not 1st person. I just felt that the pacing of the season was very inconsistent. And in the the last 10min of the season finale a lot of important stuff happens that they didn't explain, or spend much time earlier in the season foreshadowing.
The spin was only quite slow, and they showed her helmet rolling away as a result of the spin. I thought that was absolutely great. Though you are right she should have been far away from the ship after she jumped off it. I agree the Naomi scenes were way too slow and hard to understand. I'm quite obsessed with sci-fi and have played hundreds of hours of kerbal space program, and I had no idea what she was doing. For example, apparently the airlock was not fully functional, so every time she used it she lost the air that was inside the airlock. That's why she was marking how many times she went between the hull of the ship.
I didn't not like it, but it was far from the best season. I'd put it on par with 1, which I also found rather slow and unengaging.
The acting when Naomi was stuck on the ship was bang on.... Dominique Tipper nailed those scenes when she was holding her breath and fiddling with the Chetzemoka.
I found the stuff with the Mars fleet having worked some deal out with Inaros was pretty well established, leading up to it. I wasn't surprised at all. I didn't know they already had a planet they were claiming though. Just thought that we'd see the Maritans working along side the Free Navy while other Martians would go through the ring to colonize new worlds. Like the way it all turned out, but yes, seems like some things were off with the pacing for the last 3 episodes. Pete Peppers has a good video on the difference between the book and the show and it seems like it would be harder to convey for the show.
@@alistairmerrifield5035 Ya her acting conveyed that she was desperate and exhausted, probably better than if it was read from her POV chapter. But I'm guessing that her POV chapter had her thoughts, and we could follow what she was trying to do better.
Good stuff as always! 🧑🚀🧑🚀🚀🚀
like sure the physics are whack but why the forward thruster as in the drive thruster not the adjuster thruster is is still burning wouldnt that cause it to slew or is that an aerodynamic function that requires drag and atmosphere?
It should be possible with the right spin rate.