my exact thoughts, at the moment when it happens, at 4:50 - seconds before reading this comment, and the reason for reading the comments in the first place.
I've been wondering about how gravity assists work for about two years now, my teachers couldn't explain it to me, and now suddenly I understand. I think gravity assists are one of the most interesting elements of orbital mechanics, a field of which I hope to make my career one day, so thank you for teaching me this. The math still went over my head but at least now that I understand the concept I have a better basis for beginning to understand the math
Yet another couple great euphemisms for lithobraking... "Spaceship attempted a gravity assist at an impact parameter below the object's radius", "spaceship interacted strongly with the object's matter (as it unfortunately was not made of W.I.M.Ps)"
I'm guessing that spacecraft was moving with like 0.999999 c before initiating the lithobraking procedure. Otherwise it's just boring electromagnetic interaction.
I literally googled a week ago "How Gravity Assists Work", I found few videos including your 4 year old video about gravity assists. I never understood how this works, but now I do understand this, thanks to you!
It's okay. That amount of kinetic energy matters to the planet as much as a penny does to Scrooge McDuck. The difference is that planets aren't money-loving ducks.
I'm not so sure. Maybe that's how 51 Pegasi b ended up so close to its star - so many spacecraft used it for gravity assists that it lost orbital velocity and fell into a closer orbit.
you can make anything look like a perpetual motion theory if you have low enough precision lol that said, gravity assists were my favorite part of my astronautics exam
I am imagining a scifi universe with an *Intergalactic Commission of Planetary Conservation,* who passes laws that ban Starships from using gravity assists on specific planetary bodies. "This commission dictates that no Starship shall use the planet Omicron Persei 8 for Gravity Assist Maneuvers, out of concern that its orbit will decay within a few eons if reckless pilots do not respect our system's fragile planetary system"
BlankPicketSign That could be a possibility. For starships that are sufficiently large to affect the orbit of smaller dwarf planets they could be altered enough to cause a significant change in their orbit. Although the way i understand it, the larger the difference in mass between the planet and the ship the more efficient the ships gravity assist would be at accelerating.
@@ThePWCT well, the effect to the orbit could be essentially negated if a ship of similar mass did a similar manoeuvre in the opposite direction. Also, yeah, large ships wouldn't really benefit much from doing a gravity assist on such small bodies.
Feel like if a planetary body is small enough for its orbit to decay from a few million gravity assists, then you wouldn’t get much off of the size of that body. Just a thought though.
Can you do an example in KSP where you fly a spacecraft to another planet with and without using a gravity assist and compare the delta v required to reach the planet?
Just get a gravity assist from the Mun for an example. It's super easy to do. Now, adjusting the ejection angle is harder, but you can easily leave Kerbin orbit with only the delta-v required to reach the mun. You can also capture yourself around Duna using Ike and it's huge soi.
Slight mistake. WIMPs flying through a planet would not get extra deflection because the gravity interior of a planet is not that of a point mass (which is good because nobody wants a black hole in their planet's core). In the most extreme case, a WIMP that goes right through the center of a planet is not deflected at all.
Mostly true, depends on the composition of the planet. On Earth, the gravitational acceleration increases until a certain depth, as most mass is in the core.
Nobody wants a black hole in their planet's core. Except in Super Mario Galaxy, everyone seems to be cool about it there. (→Game Theory th-cam.com/video/EcmzKbJsWtw/w-d-xo.html)
Awesome! Thanks for this! I filmed the OSIRIS-REx flyby last week with a few scopes and I'm putting together a video on it. I don't have time to cover the physics of gravity assists properly, but I'll definitely mention this video. Thanks for making complex orbital mechanics understandable, as always.
This is the same effect as a tennis ball hitting front of a train like this: train is moving towards you with a speed of 100 km/h and you hit a tennis ball towards the train with a speed of 100 km/h. Ball hits the front of the train and bounces (without elastic loss) back to you. What is the speed of a ball compared to you? It is 300 km/h. How? Ball moves toward the train with a speed of 200 km/h (100+100) and in the frame of a train after collision ball has this same speed relative to the train but in opposite direction. Since train moves with a speed of 100 km/h and ball moves away from the train with a speed 200 km/h relative to the train, speed of the ball relative to you is 100+200=300 km/h. In this example you assume ball bounces with the same speed back. This is theoretically not the case, this speed is smaller, proportional to the mass ratio of ball compared to the train. But since train has much bigger mass than a ball this effect is rather small. Same goes for spacecraft. In this scenario, momentum that spacecraft gains is equal to the momentum planet loses but since planet is so much bigger than a spacecraft this is negligible.
Scott!!! At my university I just got put on a senior design (aka capstone) project to design a prototype payload for a satellite for Air Force Research Labs that can de-orbit space debris in important sun synchronous polar orbits. I have found that thanks to KSP and your videos, I have a pretty deep understanding of orbital mechanics and how these things need to work that even our advisors with doctorates in mechanical engineering don't really have much of a grasp on. For example, even really simple basics like you need to thrust retrograde to de-orbit not thrust straight down at Earth. Thanks for all the education videos Scott!!!
"Unfortunately space ships, at least in my experience, don't tend to fly through intact" - Scott Manley I don't think you and I play the same Kerbal Space Program
That was a very technical explanation. For a simplified version, think of it like your spacecraft is being pulled towards the planet but the planet is moving away from it at the same time. Positioned properly, you never hit the planet but you gained some speed, stealing energy from the planet's orbit. You're literally being tugged by the planet's gravity.
EmperorCookie That makes sense, but I've never understood how it works out to speed you up. Once you've passed the planet should it not end up doing an equal amount of deceleration as it did acceleration?
I think that with respect to the planet you're getting close to, you will decelerate the same on the way out as you accelerated on the way in. But, with respect to the Sun, you gain speed. Also, I think that any object performing a gravity assist technically alters the larger body's orbit an extremely slight bit. So they act on each other relative to each other's mass.
true that is kind of the short version! the reality is since the planet is moving away you kind of spend more time being pulled towards and away even if you final speed does not change, you actually did gain some! the "shape" of your orbit changes! (to change it uses fuel hence the major gain!) one way to look at it is on one axis you would do 100m/s,150m/s,100m/s but the other axis (the direction the planet is advancing) you would do 100m/s,125m/s,150m/s you would not seem to be falling towards the planet since you follow it but when it is gone, the speed stayed with you. well that a not so short way to put it ;P (medium length?)
Think of it as sitting in front of the planet’s trajectory for a bit, the planet is pulling you, and you’re pulling the planet, so you end up slowing the planet down. That orbital energy is transferred to your spacecraft. So while gravity is a conservative force, you’re stealing some of the planet’s orbital (with respect to the sun) velocity, and using it to add energy to your craft. A better way to think of it is that it’s basically magic. You’re using magic.
assomeone with a passion for astronomy, but no career in it, videos like this are massively helpful. while I have science training, its in biology mostly. relativistic physics, newtonian mechanics, al so fascinating, but all to often just slightly out of reach for me. this is exactly what I needed to know. thanks!
Mr. Manley, would you think about making a video or video series specifically about applying calculus (particularly the first semester) to orbital mechanics and Kerbal space program? I understand that you have made such videos in the past, and it might be easiest to simply organize your videos such as this into a playlist, however, I think it might be worth noting that your original orbital mechanics video is both hard to understand and hard to follow. If you already have a video playlist, would you (or someone else in the comments) mind linking it please? Thank you for all your videos Mr. Manley. Keep making them!
use the KSP Trajectory Optimisation Tool. I used it to perform few nice gravity assists that saved at least a kilometer per second of delta-v, so it's pretty useful.
Take a craft with lots of deltaV ang go to the jool system, play around with geavity assists ( especially tylo and laythe) and you will get better at it with time.
But a gravity assist that gets me into the plane of another body, after a burn somewhere mid-way on my way to the gravity assist body? When I do gravity assists, I make sure I am as close to the plane of the planet as possible, preferably tool-assisted, to then get a push out of the the encounter without being flung off into nowhere. Also, burns in the middle between two orbits are mostly quick and dirty fixes for when I couldn't get the maneuver right with a single burn. Not carefully planned actions to save delta-v. What's even the best point to make such maneuvers? I always make them about ...... there (meaning I fiddle around a bit with the maneuver node until it looks kinda right and not too wasteful).
Wow Scott! Admittedly it's been a long time since my Uni engineering days... but I'd hate to see what you think is complex math Lol! Well done mate. Always a pleasure to watch your channel... (all the way from Smokey Sydney/AU)
THANK YOU!- I’ve always thought that somehow it’s been magic that gravity pulling you toward a body was somehow more than the gravity when you’re escaping on the other side! 🤪
In comparison to other youtubers who do space videos, Scott actually understands physics and math to a level that's beyond appropriate. He is legit and I really like his channel!
Thank you so much for doing this video! I had 2 semesters of Astronomy but I still couldn't figure out why gravity assists helped! Now I finally understood it :D
I come back to this video each time I restart playing Kerbal and get to the more interplanetary contracts, and each time I have a new moment of revelation!
Yesterday I was thinking "I can't find any accessible well-edited way to understand gravity assists in KSP. I wish Scott would make a video specifically about that". I'm glad I only had to wait about 24 hours.
Thank you! I study physics and we had a short course on orbital mechanics but we didn't talk at all about gravity assists, and I couldn't wrap my brain around the fact that a system actually gained energy during an assist
The system as a whole gains no energy. In the planet-spacecraft frame of reference (FoR) the spacecraft leaves with the same amount of speed it entered with, so no net energy gain. In the Sun's FoR the amount of energy gained by the spacecraft is equal to the amount of energy lost by the planet, so again no net energy gain.
The easiest way to think about gravity assists is that gravity is just the coupling force and what happens is an exchange of momentum akin to a perfectly elastic collision. The momentum being exchanged is that of the bodies around their mutual parent object. In the case of space probes this is the Sun. The probe gains/loses some momentum with respect to the Sun and the body used for gravity assist loses/gains the same amount with respect to the Sun.
The last part always sounded to me like an intro of a nonexistent Bernard Werber novel where Jupiter has slowed down so much over time that it started to fall towards the sun and people had to gravity assist the hell out of it to speed it up back again.
one of the most famous gravity assist was Apollo 13 when they flew by the Moon to return to earth after their service module was damaged in an explosion.
3:20 - 3:54 (straightforward explanation with velocities of 1) and you arrive at a conclusion of 0.76 and say that's easy. I couldn't see your formulas so that me feel like an idiot, then when I was able to see the screen I still feel like an idiot. I'm sure it's easy to you but could you explain each step?
It's using pretty basic trigonometry. Firs step is to use the cosine and sine of 45° to find the axial components of the vector, then you subtract the x components of the probe and the planet (in this case 0.707-1) which gives you the relative velocity in the x axis. Then you can use trig to go backwards to recombine the new x component and y component into a single velocity. For the second part, you just add or subtract the relative velocity to/from the planet's velocity
For some reason the media seemed to think it was a more exciting story for there to be a scam. This caused a lot of funding sources to dry up and well that slowed things down significantly.
Cody'sLab I just forgot that MarsOne project even existed. I searched on youtube what happend, and some people said that it was a scam. So I checked their twitter and did some research, it looked like it wasn't then I got really confused...Thanks for clearing it up.
Mars One didn't do themselves any favours by picking participants based upon how much merchanidise they could encourage their followers to buy, and then not providing much in the way of public details on their designs.
Hey Scott. I've been wondering about slowing down when entering a system, and using gravity assists. You've shown how here - by approaching the body who's gravity you want to assist you from the other side than the side you would've chosen if you'd wanted a slingshot, (but the same angle of approach.) I wonder if this corresponds in some way to this other idea I had: namely, that with slingshots you angle your spacecraft towards the gravity well of a certain body. But if I visualize wells, I also visualize that 5 L-points diagram, and the L-points are hills instead of wells. So, maybe, if you angle your spacecraft towards the Lagrange points, you can use them to decrease speed somehow? Appeals to my logical side, but my 'get real!' side can't picture it. Can you help?
Off topic but Interested in one of your notes at 4:39 . Top left you mention how your coordinates seem backwards because plants orbit anticlockwise. Curious where that perspective started. If you flip the solar system upside down. It all just becomes clockwise doesn't it? (with a few exceptions in RL) Curious where this is based. I could probably spend hours tryin to research this instead of just streaming and learning stuff in KSP through trials. xD
Pretty nice video on the slingshot effect. But doesn't Gravity Assist also include the Oberth effect? I find the later one much harder to understand then the former and would really appreciate a video on that.
I always thought gravity assist was when a space ship followed a planet on it's orbit and then flew off perpendicular to it. It would spend longer falling towards the planet (because the space ship is chasing it) than it does escaping from it, hence it would gain energy, effectively taking it from the planet's orbit. And today I am a little bit wiser ... :)
Thanks! I am dumb. I think I failed to see that the planet's vector IS the resulting vector... After that, of course out_vector - in_vector = delta_v_vector...
I'm in a graduate level orbit mechanics class but this video genuinely helped me realize some fundamental ways I was thinking about assists wrong. Thanks Scott, hopefully now I won't fail my exam tomorrow :D
Scott. slightly off thread. why does not spacex use on their landing barges.. a video recorder to record the landing with and transmit it 10 or 15 seconds later to the live feed when the signal has been reestablished after the movement from the landing.
"In this universe we respect the conservation of energy" Yea, except dark energy. There's new space being shoved into the space that's already here and all of it has some energy.
does this mean that we're just re-shaping the orbit from somewhat circular to more elliptical? and the velocity we gain is actually just taken from say the Y axis and added to the X axis during the deflection maneuver?
I love how whenever I search a space thing there's a Scott Manly video about it
He should get a cool hat and call himself Manly Scout 😀
Y
E
S
That's what I just did 😅
Even better is hes using KSP to demonstrate it
"Now that we've cleared that up" Shit I should have been paying attention.
ITS NOT CLEAR AT ALL ( oДo)
my exact thoughts, at the moment when it happens, at 4:50 - seconds before reading this comment, and the reason for reading the comments in the first place.
He almost laughed when he said that.
Planetary matter affecting spacecraft too much? 10,000x Time warp and you fly right through that bugger!
Periapsis: 300m
*Sudden explosion noise accompanied by sudden appearance of planet*
Catastrophic failure!
Sort of like a "Holdo Maneuver"!
I've been wondering about how gravity assists work for about two years now, my teachers couldn't explain it to me, and now suddenly I understand. I think gravity assists are one of the most interesting elements of orbital mechanics, a field of which I hope to make my career one day, so thank you for teaching me this. The math still went over my head but at least now that I understand the concept I have a better basis for beginning to understand the math
Yet another couple great euphemisms for lithobraking... "Spaceship attempted a gravity assist at an impact parameter below the object's radius", "spaceship interacted strongly with the object's matter (as it unfortunately was not made of W.I.M.Ps)"
I'm guessing that spacecraft was moving with like 0.999999 c before initiating the lithobraking procedure. Otherwise it's just boring electromagnetic interaction.
We've got a physics terminology Nazi here :p
A strong interaction would be quite a hard impact, wouldn't it?
@@jdotoz Inertial fusion is a thing, yes :D
"The magic of Microsoft paint" AND comic sans no less!
i feel like Kerbals would use MS Paint to make the plans for their rockets :)
No, they would use it to actually make the rockets. How else could they build the rockets so fast?
Atleast not the chinese language as i thought, but its still a korean language to me.
Shouldn't we be using Cosmic Sans for that? ;-)
Fred
dont you mean COSMIC sans
I literally googled a week ago "How Gravity Assists Work", I found few videos including your 4 year old video about gravity assists. I never understood how this works, but now I do understand this, thanks to you!
"Lisa, get in here . . . in this house we obey the laws of thermodynamics!"
Ha ha it's mine now! I'm not giving it back!
It's okay. That amount of kinetic energy matters to the planet as much as a penny does to Scrooge McDuck. The difference is that planets aren't money-loving ducks.
That's my favourite Simpsons joke!
TheEqualsE you're actually stealing a little bit of the planet's energy
I'm not so sure. Maybe that's how 51 Pegasi b ended up so close to its star - so many spacecraft used it for gravity assists that it lost orbital velocity and fell into a closer orbit.
you can make anything look like a perpetual motion theory if you have low enough precision lol
that said, gravity assists were my favorite part of my astronautics exam
I've watched this video 4 times over the past few years, and every time I watch it, I understand it a little bit more, it's super interesting
I am imagining a scifi universe with an *Intergalactic Commission of Planetary Conservation,* who passes laws that ban Starships from using gravity assists on specific planetary bodies. "This commission dictates that no Starship shall use the planet Omicron Persei 8 for Gravity Assist Maneuvers, out of concern that its orbit will decay within a few eons if reckless pilots do not respect our system's fragile planetary system"
BlankPicketSign That could be a possibility. For starships that are sufficiently large to affect the orbit of smaller dwarf planets they could be altered enough to cause a significant change in their orbit. Although the way i understand it, the larger the difference in mass between the planet and the ship the more efficient the ships gravity assist would be at accelerating.
GIVE US SINGLE FEMALE LAWYER MCNEAL OR WE'LL LAY WASTE TO YOUR CITIES ༼ つ ◕_◕ ༽つ
I saw the Futurama reference
@@ThePWCT well, the effect to the orbit could be essentially negated if a ship of similar mass did a similar manoeuvre in the opposite direction. Also, yeah, large ships wouldn't really benefit much from doing a gravity assist on such small bodies.
Feel like if a planetary body is small enough for its orbit to decay from a few million gravity assists, then you wouldn’t get much off of the size of that body. Just a thought though.
Can you do an example in KSP where you fly a spacecraft to another planet with and without using a gravity assist and compare the delta v required to reach the planet?
I did it with Outer Planets Mod. Going to Sarnus with a gravity assist at Jool saved me almost 1km/s.
Scott talks about exactly this in his "sending trash to the sun video": th-cam.com/video/uNS6VKNXY6s/w-d-xo.html
Just get a gravity assist from the Mun for an example. It's super easy to do. Now, adjusting the ejection angle is harder, but you can easily leave Kerbin orbit with only the delta-v required to reach the mun. You can also capture yourself around Duna using Ike and it's huge soi.
This would be interesting
Yup
Slight mistake. WIMPs flying through a planet would not get extra deflection because the gravity interior of a planet is not that of a point mass (which is good because nobody wants a black hole in their planet's core). In the most extreme case, a WIMP that goes right through the center of a planet is not deflected at all.
Mostly true, depends on the composition of the planet. On Earth, the gravitational acceleration increases until a certain depth, as most mass is in the core.
Nobody wants a black hole in their planet's core. Except in Super Mario Galaxy, everyone seems to be cool about it there. (→Game Theory th-cam.com/video/EcmzKbJsWtw/w-d-xo.html)
However, the density of most planets is lower near the surface, so there would still be gains to be made up to a point.
Ah yes, there will be a maxima somewhere between the surface and the core that is a function(al) of the density function.
I came down here looking for this exact comment XD
UPDATE FROM THE FUTURE:
OSIRIS-Rex has arrived at Bennu and captured a sample larger than anticipated. Estimated date of return is September 2023
Hopefully, the pandemic will have been over by then.
I always thought gravity assist is just a nice way of calling people fat.
In physics, that fattest people are the most attractive.
I'm imagining a very... large person coated in a dozen smaller people who cannot achieve escape velocity, with babies orbiting the collective mass.
*Gravity ASS-cyst.
Fat kids are harder to kidnap
I am not fat, I have a high inertia coefficient. i.imgur.com/I9Rek84.jpg
I was just waiting for a video that shows how to change inclination through gravity assist in ksp and your video is a gift to me , thanks !!
Awesome! Thanks for this! I filmed the OSIRIS-REx flyby last week with a few scopes and I'm putting together a video on it. I don't have time to cover the physics of gravity assists properly, but I'll definitely mention this video. Thanks for making complex orbital mechanics understandable, as always.
Now that we've cleared that up, yeah, didn't get any of that.
This is the same effect as a tennis ball hitting front of a train like this: train is moving towards you with a speed of 100 km/h and you hit a tennis ball towards the train with a speed of 100 km/h. Ball hits the front of the train and bounces (without elastic loss) back to you. What is the speed of a ball compared to you?
It is 300 km/h.
How?
Ball moves toward the train with a speed of 200 km/h (100+100) and in the frame of a train after collision ball has this same speed relative to the train but in opposite direction. Since train moves with a speed of 100 km/h and ball moves away from the train with a speed 200 km/h relative to the train, speed of the ball relative to you is 100+200=300 km/h.
In this example you assume ball bounces with the same speed back. This is theoretically not the case, this speed is smaller, proportional to the mass ratio of ball compared to the train. But since train has much bigger mass than a ball this effect is rather small.
Same goes for spacecraft. In this scenario, momentum that spacecraft gains is equal to the momentum planet loses but since planet is so much bigger than a spacecraft this is negligible.
You're still one of my favorite youtubers Scott. Years already. Love these video's.
Scott: “This is all pretty simple”
Scott: **maths words**
Me: 😳
You can tell the new comments because they all look like the comments on every other video :(
😭
Scott!!! At my university I just got put on a senior design (aka capstone) project to design a prototype payload for a satellite for Air Force Research Labs that can de-orbit space debris in important sun synchronous polar orbits. I have found that thanks to KSP and your videos, I have a pretty deep understanding of orbital mechanics and how these things need to work that even our advisors with doctorates in mechanical engineering don't really have much of a grasp on. For example, even really simple basics like you need to thrust retrograde to de-orbit not thrust straight down at Earth. Thanks for all the education videos Scott!!!
"Unfortunately space ships, at least in my experience, don't tend to fly through intact" - Scott Manley
I don't think you and I play the same Kerbal Space Program
Had to watch this couple times but i finally grasp the basic mechanics of gravity assist. Makes total sense! THANKS!!!
That was a very technical explanation. For a simplified version, think of it like your spacecraft is being pulled towards the planet but the planet is moving away from it at the same time. Positioned properly, you never hit the planet but you gained some speed, stealing energy from the planet's orbit. You're literally being tugged by the planet's gravity.
EmperorCookie That makes sense, but I've never understood how it works out to speed you up. Once you've passed the planet should it not end up doing an equal amount of deceleration as it did acceleration?
I think that with respect to the planet you're getting close to, you will decelerate the same on the way out as you accelerated on the way in. But, with respect to the Sun, you gain speed. Also, I think that any object performing a gravity assist technically alters the larger body's orbit an extremely slight bit. So they act on each other relative to each other's mass.
true that is kind of the short version! the reality is since the planet is moving away you kind of spend more time being pulled towards and away even if you final speed does not change, you actually did gain some! the "shape" of your orbit changes! (to change it uses fuel hence the major gain!) one way to look at it is on one axis you would do 100m/s,150m/s,100m/s but the other axis (the direction the planet is advancing) you would do 100m/s,125m/s,150m/s you would not seem to be falling towards the planet since you follow it but when it is gone, the speed stayed with you. well that a not so short way to put it ;P (medium length?)
Think of it as sitting in front of the planet’s trajectory for a bit, the planet is pulling you, and you’re pulling the planet, so you end up slowing the planet down. That orbital energy is transferred to your spacecraft.
So while gravity is a conservative force, you’re stealing some of the planet’s orbital (with respect to the sun) velocity, and using it to add energy to your craft.
A better way to think of it is that it’s basically magic. You’re using magic.
EmperorCookie. Thank you so much for that explanation.
It may be an over simplification, but it's one that I can work with.
I'm sorry, but I laughed my head off when you said you were turning to the magic of M.S. Paint.
assomeone with a passion for astronomy, but no career in it, videos like this are massively helpful. while I have science training, its in biology mostly. relativistic physics, newtonian mechanics, al so fascinating, but all to often just slightly out of reach for me. this is exactly what I needed to know. thanks!
Mr. Manley, would you think about making a video or video series specifically about applying calculus (particularly the first semester) to orbital mechanics and Kerbal space program?
I understand that you have made such videos in the past, and it might be easiest to simply organize your videos such as this into a playlist, however, I think it might be worth noting that your original orbital mechanics video is both hard to understand and hard to follow.
If you already have a video playlist, would you (or someone else in the comments) mind linking it please?
Thank you for all your videos Mr. Manley. Keep making them!
I've always been looking for a video on this! Thanks again Scott : )
Hi Scott, thanks for the video. After watching it and paying close attention, I'm wondering: how the hell do gravity assists work?
Whats the software starting at around 5:00? Thanks a lot if you could share that
I'll never be able to plan an orbit in KSP like the one OSIRIS REx took 😢
use the KSP Trajectory Optimisation Tool. I used it to perform few nice gravity assists that saved at least a kilometer per second of delta-v, so it's pretty useful.
Take a craft with lots of deltaV ang go to the jool system, play around with geavity assists ( especially tylo and laythe) and you will get better at it with time.
But a gravity assist that gets me into the plane of another body, after a burn somewhere mid-way on my way to the gravity assist body? When I do gravity assists, I make sure I am as close to the plane of the planet as possible, preferably tool-assisted, to then get a push out of the the encounter without being flung off into nowhere. Also, burns in the middle between two orbits are mostly quick and dirty fixes for when I couldn't get the maneuver right with a single burn. Not carefully planned actions to save delta-v. What's even the best point to make such maneuvers? I always make them about ...... there (meaning I fiddle around a bit with the maneuver node until it looks kinda right and not too wasteful).
The Aziz, I will definitely try out that mod, thanks!
Wow Scott!
Admittedly it's been a long time since my Uni engineering days... but I'd hate to see what you think is complex math Lol!
Well done mate. Always a pleasure to watch your channel... (all the way from Smokey Sydney/AU)
I was just wondering how they work after watching one of Matt Lowne's videos where he did a bunch of them to get to Eeloo. Perfect timing!
THANK YOU!- I’ve always thought that somehow it’s been magic that gravity pulling you toward a body was somehow more than the gravity when you’re escaping on the other side! 🤪
I've always wondered how this works! Fantastic videos for the space enthusiast, I watch these one after another.
scott teaching us about space and maths more than anyone else in the world
"This is just a very basic lesson"
Maths were never my strong suit.
In comparison to other youtubers who do space videos, Scott actually understands physics and math to a level that's beyond appropriate. He is legit and I really like his channel!
Thank you so much for doing this video! I had 2 semesters of Astronomy but I still couldn't figure out why gravity assists helped! Now I finally understood it :D
3:43 what is Scott subtracting x and y from to get 0.765? He says it's super easy but idk where the numbers are coming from lol
Great videos as always! Thank you Scott!
I come back to this video each time I restart playing Kerbal and get to the more interplanetary contracts, and each time I have a new moment of revelation!
Haven't played KSP in a bit.
Now I feel like starting a new campaign and experimenting with gravity assists. I never really knew how to use them.
Thank you Scott, this video was perfectly well explained
Yesterday I was thinking "I can't find any accessible well-edited way to understand gravity assists in KSP. I wish Scott would make a video specifically about that". I'm glad I only had to wait about 24 hours.
This video explains why I never became a rocket scientist. Thank you.
Your science videos are awesome Mr. Manley!
I've been studying physics since 5 years now and noone could answer me this ... thank you Scott Manley
Thank you Scott. For the longest time, my tiny non-physicist brain thought that gravity assists violated conservation of energy.
Thank you! I study physics and we had a short course on orbital mechanics but we didn't talk at all about gravity assists, and I couldn't wrap my brain around the fact that a system actually gained energy during an assist
The system as a whole gains no energy. In the planet-spacecraft frame of reference (FoR) the spacecraft leaves with the same amount of speed it entered with, so no net energy gain. In the Sun's FoR the amount of energy gained by the spacecraft is equal to the amount of energy lost by the planet, so again no net energy gain.
Andrew Steel Yes I understood, thanks
The easiest way to think about gravity assists is that gravity is just the coupling force and what happens is an exchange of momentum akin to a perfectly elastic collision. The momentum being exchanged is that of the bodies around their mutual parent object. In the case of space probes this is the Sun. The probe gains/loses some momentum with respect to the Sun and the body used for gravity assist loses/gains the same amount with respect to the Sun.
It's all about that _Special Theory of Relativity_ !
Discovered ur channel nice
After the truly useless video by the CSA about gravity assists, I was delighted to see a video from a REAL educator!
Needed this video! Thanks!
6:51 - Or a Delta IV, which is even _more_ expensive.
The last part always sounded to me like an intro of a nonexistent Bernard Werber novel where Jupiter has slowed down so much over time that it started to fall towards the sun and people had to gravity assist the hell out of it to speed it up back again.
I've been waiting for this for a long time. :)
When you want cheap velocity try the trajectory explained: plus.google.com/u/0/+BartDooper/posts/U7E4GsThTiD
one of the most famous gravity assist was Apollo 13 when they flew by the Moon to return to earth after their service module was damaged in an explosion.
Holy hell the final animation of ... "Cassini Trajectory"? There's SO MUCH gravity assist calculation there , definitely!
3:20 - 3:54 (straightforward explanation with velocities of 1) and you arrive at a conclusion of 0.76 and say that's easy. I couldn't see your formulas so that me feel like an idiot, then when I was able to see the screen I still feel like an idiot. I'm sure it's easy to you but could you explain each step?
It's using pretty basic trigonometry. Firs step is to use the cosine and sine of 45° to find the axial components of the vector, then you subtract the x components of the probe and the planet (in this case 0.707-1) which gives you the relative velocity in the x axis. Then you can use trig to go backwards to recombine the new x component and y component into a single velocity.
For the second part, you just add or subtract the relative velocity to/from the planet's velocity
"Ye cannae chance the laws of physics, Jim!"
Or was it, "I cannae change the laws of physics, Cap'n!" ?
Fred
"I need THIRTY MINUTES!"
This might be a random topic to say in here but what exactly happend to MarsOne project?
For some reason the media seemed to think it was a more exciting story for there to be a scam. This caused a lot of funding sources to dry up and well that slowed things down significantly.
Cody'sLab I just forgot that MarsOne project even existed. I searched on youtube what happend, and some people said that it was a scam. So I checked their twitter and did some research, it looked like it wasn't then I got really confused...Thanks for clearing it up.
Mars One didn't do themselves any favours by picking participants based upon how much merchanidise they could encourage their followers to buy, and then not providing much in the way of public details on their designs.
SpaceX ITS
They didn't have anything material so it was probably a scam, media craze or not
Thanks for clearing this up Scott! It was always a topic that I had absolutely no idea of. 😂
Hey Scott. I've been wondering about slowing down when entering a system, and using gravity assists. You've shown how here - by approaching the body who's gravity you want to assist you from the other side than the side you would've chosen if you'd wanted a slingshot, (but the same angle of approach.) I wonder if this corresponds in some way to this other idea I had: namely, that with slingshots you angle your spacecraft towards the gravity well of a certain body. But if I visualize wells, I also visualize that 5 L-points diagram, and the L-points are hills instead of wells. So, maybe, if you angle your spacecraft towards the Lagrange points, you can use them to decrease speed somehow? Appeals to my logical side, but my 'get real!' side can't picture it. Can you help?
Off topic but Interested in one of your notes at 4:39 . Top left you mention how your coordinates seem backwards because plants orbit anticlockwise. Curious where that perspective started.
If you flip the solar system upside down. It all just becomes clockwise doesn't it? (with a few exceptions in RL) Curious where this is based. I could probably spend hours tryin to research this instead of just streaming and learning stuff in KSP through trials. xD
Pretty nice video on the slingshot effect. But doesn't Gravity Assist also include the Oberth effect? I find the later one much harder to understand then the former and would really appreciate a video on that.
+tonberrytoby it only includes Oberth effect if the spacecraft fires engine near closest approach.
Space craft: It’s free Delta V
you somehow made comic sans look comforting
Didn't understand shit of the description of the hyperbolic stuff but sounded fascinating, thank you.
2:28 Speed, not velocity. The change in velocity is the whole point.
You keep saying “velocity” when you mean “speed”. Speed is a scalar, while velocity has a direction.
Ty for helping me with my physics assignment
I always thought gravity assist was when a space ship followed a planet on it's orbit and then flew off perpendicular to it. It would spend longer falling towards the planet (because the space ship is chasing it) than it does escaping from it, hence it would gain energy, effectively taking it from the planet's orbit.
And today I am a little bit wiser ... :)
I love how you write math as excel formulas... I get that reflex too
Nice vid, Scott! But how did you arrive at vrel = 0.765?
+DailyFrankPeter sqrt ( 0.707^2 + 0.293^2)
Thanks! I am dumb.
I think I failed to see that the planet's vector IS the resulting vector... After that, of course out_vector - in_vector = delta_v_vector...
I'm in a graduate level orbit mechanics class but this video genuinely helped me realize some fundamental ways I was thinking about assists wrong. Thanks Scott, hopefully now I won't fail my exam tomorrow :D
Literally watched every video about gravity assists in ksp today.
Your old video was pretty bad, so glad you made a new one about this topic :)
BTW, the parameters they use in industry are C3 (characteristic energy) and altitude from slingshot body.
You deserve more recompense for this level of quality information than just some thumbs up
Hey Scott,
can you make a video about Parker Solar Probe?
Espacially the heat shield sounds interesting, but I could't get much information on it
This is all well and good. But how fast can you calculate it on a slide rule?
Scott. slightly off thread. why does not spacex use on their landing barges.. a video recorder to record the landing with and transmit it 10 or 15 seconds later to the live feed when the signal has been reestablished after the movement from the landing.
This video, the astronaut orbiting space station video, and the event horizon/schwarzchild video all loop together through autoplay.
I love your intro so much
Scott, any chance you can explain how Euler's algorithm was used in the movie Hidden Figures to assist in the planning for the Atlas program?
what software do you use to get those amazing 3d paths renders?
I think your next challenge should be to see how close you can pass by the mun without hitting it.
Im trying to find a video about the solar gravity assist / "fry-by" thing where you also fire the engine on the way around.
"In this universe we respect the conservation of energy"
Yea, except dark energy. There's new space being shoved into the space that's already here and all of it has some energy.
Hey, Scott, how'd ya think - can be asteroid matter/unwanted spacecraft components used as propellant in sort of ion/nuke/magic engine? IRL of course
Slight malfunction at 2:15 using the term "Warp" totally triggered the trekkie in me... :D
Simple stuff? I think I need a lie down after that!
Thanks, excellent video.
Didn't you do a video on this sometime back?
I was waiting for this video👌
This is very cool software.
If it can be teached in the primary school, student would be love to study Physics when they are in high school.
It’s crazy how you can just steal part of a planet’s kinetic energy for yourself.
02:19 - "... the same velocity." You meant speed, right ?
obviously....
What is the name of the software you used at the beginning of your video?
I’m so glad Osiris Rex was my first launch I saw. Pure science baby. None of that mamby pamby communications satellite.
does this mean that we're just re-shaping the orbit from somewhat circular to more elliptical? and the velocity we gain is actually just taken from say the Y axis and added to the X axis during the deflection maneuver?
I've had arguments with friends on gravity assist. This is the best explanation I have ever heard. Thank you. I was right! (For once).