well, the engineering tolerances in the 1960's were around 30% and no one confused metric and imperial measurements. Given that the material sciences of the 1960's also gave us silver mica which today is better known as silver mica disease, and carbon composite resistors that today give us the sizzle and pop background sound to vintage gear, and PN junctions that suffer hole drift it's more amazing that anything we put up in the 1960's is in fact still up and going.
I use electron microscopes for a living, so I am kind of used to tight tolerances. But the amount of precision involved in even a "simple" orbital docking maneuver blows my mind.
There are mid-course corrections, so they aren't depending in being so precise from the launch, plus the laws of Newton are sufficient to travel anywhere in the Solar System.
Nice video Amy! Only thing that I would like to see added to a video on this topic are specific numbers on how much velocity a spacecraft gains when doing a flyby/slingshot/gravity assist. It made the concept of how these work and why they are so useful & important when I learned that Voyager 2 gained about 10 km/s at Jupiter, about 5 km/s at Saturn, about 2 km/s at Uranus, and lost about 2 km/s at Neptune. Keep up the good work Amy! Can’t wait for your X-Planes series!
Both VOYAGERS were incredible! They were amazingly successful at a time when we in the USA really needed something of ours to cheer for even if it WAS a robot probe we had sent far, far away in a galaxy we're just beginning to explore.
I love listening to you speak. Your voice is exactly what my hearing range picks up. Too many rock concerts growing up in the 70’s but the music was so good. Plus you’re smart. It’s always interesting. Whatever you’re talking about, it’s something I’m learning. I went into a completely different work environment with a different education. So I enjoy this channel.
Long time listener, first time caller! By that I mean I have watched and enjoyed your channel immensely for many, many years, but I think this is the first time I have commented. I find you fascinating and greatly admire what you have done with your passion. You have created your channel from scratch and powered your career all by yourself. I just finished your first book and it was amazing. I love the topic and your writing skill is excellent. Your next book is on my shelf, soon to be opened. I know I will love it as well. And I look forward to book three, which I'm sure is cooking in your lovely head. I just love how you have created your career out of your passion and your own initiative. Well done!
Your a hero to my 10 year old daughter, she was tired of geeky Men. She wants a career in aerospace and you helped make her feel its all possible... thank you
It is not accurate to say it is easier to get to Venus because it's closer to the Sun. Mercury is also in the sunward direction and it is HARD to get to. The problem is that in order to go sunward, we need delta-v to counteract some or all of the 30km/s we get "for free" just by launching from Earth - already screaming around the Sun at 30km/s orbital speed. The reason it's easier to get to Venus than to Mars is simply because it's orbit is a little bit "closer" in terms of how much delta-v a minimum delta-v Hohmann transfer requires. These principles, as well as the critical Oberth effect, were well understood at the time of the Apollo missions. (In contrast, the Oberth effect was not so well known a decade or two earlier, and at that time space technology enthusiasts didn't think chemical rocket propulsion would be able to reach other planets.) It's just random chance that it takes a little less delta-v to get to Venus than to get to Mars. That said, it's actually not obvious how you use a gravity assist at Venus to get to Mars. It's far more obvious how to use a gravity assist at Venus to kill off some sun-centric velocity because your transfer orbit will already have a faster sun-centric velocity than Venus. This is what the Parker Solar Probe did, as well as MESSENGER. But it is indeed possible to use Venus flybies to help go "outward", even if it's a bit harder to comprehend.
@@RideAcrossTheRiver Yes, but the sophistication of the simulation calculations required to derive those navigation plans was far beyond the capabilities available around the end of the Apollo program. The Voyager plans were simple and straightforward in comparison, doable with manual patched conics calculations.
best explanation ive heard of a really complex thing to do. I kinda understood it before, but you put it so well. such a superb orator. Excellent books, love em. keep it up! And dang, that is a cool dress....
I love the explanation of gravity assists in the context of early spaceflight. But two slight physics corrections: 1) A transfer going toward the sun does not necessarily cost less delta-v than a transfer going away from the sun. They both involve changing your speed (kinetic energy) relative to the Sun to affect your orbit (potential energy), a trade-off required by conservation of energy. In other words, the orbital speed from Earth prevents the craft from reaching areas closer to the Sun. A dive into the sun would require canceling out Earth’s orbital speed (30km/s), which is much more than a simple escape from the solar system (42 - 30 = 12 km/s required). Note that starting in Earth’s gravity well actually makes both of these values cheaper because of the Oberth Effect, also related to kinetic energy. 2) Gravity assists don’t just affect the speed “and” deflect the trajectory. They affect the speed “by” deflecting the trajectory. Conservation of energy states that from the planet’s perspective, the craft is approaching and departing with the same speed (kinetic energy), just with a deflection because of the hyperbolic trajectory of the flyby. But when switching to the Sun’s reference frame, a deflection of the craft’s trajectory toward the planet’s direction of motion (which you can see in the Voyager gravity assists) makes the speed more additive with the planet’s orbital speed. So the added speed is made possible by the deflection of the trajectory, but the video does a good job explaining that both of these are independently useful for the mission planning.
And a more minor nitpick: New Horizons passed closer to Pluto than Charon gets, but did not go between them, it passed the far side of Pluto from Charon.
I love this stuff. Used to work out these trajectories in the Orbiter Spaceflight Sim a lot. It's desirable to get to Mars faster than a Hohmann transfer to avoid the long 9 month transit with its freefall and radiation, but the quicker you want to get there the propellant needed ramps up fast. So, instead, you launch the Mars ship unmanned into a solar orbit and then, about a year later, use the Earth itself to do a gravity assist to put the Mars ship on a faster trajectory to Mars, and at the same time, you launch the crew in a lightweight capsule to transfer over to the Mars ship for the long ride.
I don't think what you said about the Sun's gravity is correct. "But even though the Sun has such a powerful pull, it's surprisingly hard to actually go to the Sun: It takes 55 times more energy to go to the Sun than it does to go to Mars." Planets are closer to solar escape velocity. It takes much more fuel to decelerate a spacecraft such that it will fall into the Sun than to get it to move outwards away from the Sun. We have objects leaving the Solar System now, but no man-made object has ever made it to the Sun.
Thanks for another entertaining and informative video! This is a minor thing, but I want to point out an issue: It is not actually any easier to move 'down' a gravity well than it is to move 'up' it, at least if you're already in orbit. It takes a LOT of energy to get something into a circular orbit around the sun, so a lot of energy needs to be removed to lower an orbit. For example, the orbital velocity of Earth is 29.8km/s while solar escape velocity from Earth's orbit is only 16.6km/s. In other words, you have to slow down more to reach the sun than you have to speed up to leave it entirely. The Mars/Venus situation is a similar story. Despite being closer, Venus is more difficult to reach. The reason for this is pretty straightforward, really. Gravity increases according to the inverse square of distance, so orbital speeds must also increase proportionally. Rather than thinking of gravity like water circling a drain, think of orbits as representing energy levels. As you move inward, the difference in energy between levels gets exponentially larger, and as you move out the differences are exponentially smaller. In this sense, gravity becomes more like climbing a mountain than going down a drain. At least when you're talking about moving between different orbits. There's really no analogy that perfectly captures the weirdness of orbital mechanics.
yes exactly, the water falling a drain analogy is really bad because it implies an orbit could degrade naturally just because of the sun's gravity, which is the opposite of how that works
Once again Amy, another stand out video. I always look forward to your videos, I could listen to you all day. You are clearly very intelligent, such a great memory, professional and captivating presentation, clear speech and an obvious passion for this field. You always provide a wealth of information on all of your videos and go over and beyond and in such fine detail. Thanks for all the work you put into these videos for us. Dean.
The crucial phrase is "speed relative to the Sun," otherwise some people get confused wondering why a spacecraft climbing away from a planet doesn't lose all the speed it gained when falling in. Teacher Dude noted Heinlein's "The Rolling Stones." But that "gravity assist" involved a burn at perigee, thus dumping some of the mass involved during approach, as well as the value of the burn itself.
Hi Amy, glad you mentioned the Horizons Pluto Probe. It did show Spectacular images of Pluto last year. Also, glad you know of the Hohmanns Transfer Gravity Assist and I also think this assist using Venus Gravity to either go to Mars or return, in shorter time. If the delivery of Astronauts or of course 1st supplies, fuel, air and equipment as well as secondary gear. To return samples and Astronauts. Incidentally, I think there should be a separate craft to return the samples. To keep Astronauts craft light weight and safe for them to carry sustainable rations for return. Back to Venus if Mars is on far side and Venus is Trailing slingshot to Mars a quarter of the distance. Explorations, and return within a fewer months back to Earth as it catches up to us. Though, still think should go to Mars Moon and explore the Obelisk. Thanks Amy awesome presentation ❣🚀🙋👍🛰🪐🌌🌠☄
Fantastic episode. I have bought both of your books because you really can tell a history of the people doing the cutting edge of scientific endeavour. I also recognise your excellent fashion sense. You make every episode a journey of intrigue and I most humbly thank you .
What's amazing to me is that the concept of "Gravity ASSIST" was mentioned all the way back in STAR TREK TOS when KIRK remeets the gaseous entity which almost killed him and his fellow crewmates when he was a young Ensign on his first deep space mission.
Id say the coolest part of all this, is now I see you on the History Channel Too! Hell Yeah space stuff. They just need a space based show with just you and Alex Fillipanko and id be content
You know, this one was really helpful and interesting! It's just unbelievable that we can do this! BTW, my daughter loves the various outfits as much as she loves the space talk! Thanks for making it fun!
I don't think it's delta-v that is needed for an object to slingshot around a planet instead of falling on it. That is, it doesn't need to create delta v (=accelerate) itself. If the initial velocity (just plain v, no delta) is high enough, it won't fall to the planet. Saying that a spacecraft needs just the right amount of delta-v may be interpreted as if it needs to actively accelerate with it's engines, and I think most spacecraft passively enter a gravity well and don't need to use their engines (except for small corrections or to slingshot out at a shallower angle). I'm not that familiar with physics, so if anyone can confirm or refute...
In his 1952 book, The Rolling Stones, Robert Heinlein describes the idea of 'gravity assist' repeatedly. Alas, we are not about to holiday on Mars or Venus any time soon
Most of the ballistics in Heinlein's books are either correct, or plausible. The problem with his books is they almost all depend on nuclear fission or fusion propulsion in some way, and the engines in his book are not really feasible. Bob was really anal retentive about all his ballistics, including those in _The Moon is a Harsh Mistress_ and _The Cat Who Walks Through Walls._ However they don't really work unless you have super efficient engines (In _The Rolling Stones_ he mentions that the engine is nearly 100% efficient.) with unreasonable specific impulse.
But this leaves unanswered a question: I can understand how this changes direction, but how does it change it's speed? Wouldn't it lose all the speed it gained on the approach when it escaped?
Good question/observation. The answer being that what gives the acceleration (or deceleration) isn't the the gravity of the planet itself, but the velocity of that planet around the sun.
Oh yeah. The orbital mechanics are amazing on its own. Figuring out how to use that and the masses of the planets to accurately pinball spacecraft around the solar system is more than amazing.
Great explanation of a complex subject Amy. Perhaps you could make mention of Michael Minovitch, who in 1961 while working for JPL published his theory of Gravity Propelled Interplanetary Space Travel. He enabled the exact calculation of gravity assists and opened up the Solar System for exploration.
Hi Amy, another way to save propellant/fuel is aerobraking. I wonder if you'll cover that. Rather than use fuel to slow down a spacecraft to enter an orbit, you just approach a planet such that a speeding spacecraft crashes through the upper atmosphere at just the right angle so that it doesn't slow down enough to land but just loses enough velocity due to the atmospheric drag/heating such that it passes through the atmosphere and re-emerges into space around the planet now in a stable orbit at a lower velocity . I do this all the time when I play Kerbal Space Program so I don't have to use rocket fuel slowing down to enter an orbit. :-) Of course you can only do this on a planet with an atmosphere so it wouldn't work on the moon. As long as your heat shield is good enough you can put a spacecraft on a super-fast trajectory to a planet and angle it really deep into the atmosphere to really get it to slow down and the only fuel you use is a very minor trajectory burn when you're way out instead of a braking burn. I remember the film/book 2010 depicted this maneuver and it works fine in Kerbal. Would it work in real life?
0:54 the thing about it being easier to go to Mars via Venus than going direct to Mars is often misunderstood. It’s not actually easier to get to Mars that way. But, a round trip to Mars and back has a shorter duration if one leg (but not the other) goes by Venus. A shorter duration crewed mission requires fewer supplies, and consequently less mass, and so the total mission is easier. But, for a 1-way mission to Mars, it is almost always easier to go directly to Mars without a Venus fly by.
Being very familiar with your topics, (I lived thru several), your delivery is FANTASTIC! A good balance of whimsy and hard science. If your in the Wichita, Kansas area again, please contact me. I would like to take you stargazing.
Questions I didn't know I had, indeed. I didn't even think to question why we don't use Venus assist instead of Hohmann Transfer. It makes sense, though, the way you explained it.
In the simple sense you don't get caught in an orbit if your relative speed is "low". Mathematically if you have above zero "surplus of escape velocity", which you do by definition when you are arriving, you will exit the gravity well at the same relative speed. The reason you can get caught is if you hit something inside the gravity well or are affected by uneven gravity field, like the effect of moons or tidal effect of the sun - which has more to do the "where" than "how fast". The most instructive way to think about gravity assists, IMO, is to realize that you leave the gravity well of a planet at the same speed you entered with relative to the planet, all you can do is change the direction by deciding how close and on what side of the planet you pass. The benefit after leaving the planets gravity well is derived from the fact that the planet is moving, which means that if you change direction along the axis of motion of the planet, you will change your orbital energy in the outside system. If you take a look at the Voyager gravity assists, you should notice that the common theme on this outbound trajectory is coming up to the planet from below and leaving out front of it in it's orbit. Slowing down means you come in from the rear and bend in some other direction, thus slowing down in the surrounding system. Scott Manley, of course, has a video that explain it well.
I just made a video montage of David Bowie's song I took a trip on a Gemini Spacecraft with Gemini clips, I was already happy, Amy uploads a new video, I feel much happier :3
@@TheStuport Oh, yes, it's in another channel, search for "Mister X I Took A Trip On A Gemini Spacecraft", for some reason I cannot post the link here.
Hi Amy, Sorry to say, but your explanation of gravity assist is not quite correct. Basically, gravity assist is very simple. A gravity assist just a change of the directory of the velocity vector of a spacecraft relative to a planet. If the vector of a spacecraft is changed in the direction of the planet's velocity then the velovity of the spacecraft is increased. If the vector of a spacecraft is changed in the opposite direction of the planet's velocity then the velocity of the spacecraft is reduced. That's exactly why the apollo 11 made a 8-ciffer like flight to the moon. The purpose was to reduce the velocity to help the spaceraft to go into orbit of the moon; otherwise the spacecraft would have been catapulted somewhere else. This said, I love your historical expertise in all your videos. Thanks a lot.
Yes, I wondered about this for years. I would always hear some knowledgeable space reporter talk about how Voyager would "gain speed" as it would "slingshot" past Jupiter. And I would think, won't it lose all the speed it gained going "in" as it passes the planet and goes back "out?" It has to. Finally, after playing with Orbiter and studying the Bate book, I figured out that it's the change in direction that is what matters. You're going the same speed as before but that speed is pointed in a direction that is going to get you further out in the Sun's sphere of influence.
I’m not sure if you ever covered vintage computers or the people that did the computing before the machines. Keep up the great work. I love the math and science parts in your vintage space.😁
It seems to me that one other disadvantage of using a Venus gravity assist to reach Mars is that more delta-v (or more strenuous aerobraking) would be needed to slow the spacecraft for orbit or landing. It would work for a fly-by, but that wouldn't provide much time for useful observations.
Outstanding as always. My wife and I wish you the best. Pete? Where's that furry little space ball of fuzz? My cars are his biggest fans.....Be safe and thank you...
Hi Amy, Vintage Space is awesome, I do enjoy your channel. You say that "vintage" is your thing and no doubt the 50s and 60s space effort was fascinating. I myself am a child of Apollo. I'm in. A friend of mine, a physics prof in Boston, told me recently that in one of his courses he talks about how designs and concepts have trended backward with the advent of SpaceX using modern technology. It had never occurred to me before. Of course he's right when you think about it and that made me think of your channel. The entire look of the Starship and Super Heavy stack looks a whole lot like something Von Braun might have come up with. The reusability angle also I think would have appealed to Werner. If only he had had access to guidance and control systems that we have today, not to mention the alloys SpaceX is using, what might Werner have been able to do? Also, I think you'd look badass in one of those vintage clothing get-ups alongside a Starship! 😊 So maybe a cool video topic might be "Would Werner Von Braun have made Starship?" That's a lot to unpack. That's my two cents. Thanks for the great information you supply to the public!
Great topic. I had to bail at about a minute because the audio was pretty uncomfortable to listen to. Confirmed on good headphones and home theater system.
Brilliantly explained to us nonscientists/engineers by a lovely communicator. Thank you Miss Amy! Well done.
Always amazes me they can calculate things so precisely to get to a tiny dot in space at the right speed to gently land
well, the engineering tolerances in the 1960's were around 30% and no one confused metric and imperial measurements. Given that the material sciences of the 1960's also gave us silver mica which today is better known as silver mica disease, and carbon composite resistors that today give us the sizzle and pop background sound to vintage gear, and PN junctions that suffer hole drift it's more amazing that anything we put up in the 1960's is in fact still up and going.
And also knowing exactly where that dot is in space and how fast it's going in order to make the necessary corrections.
I use electron microscopes for a living, so I am kind of used to tight tolerances. But the amount of precision involved in even a "simple" orbital docking maneuver blows my mind.
There are mid-course corrections, so they aren't depending in being so precise from the launch, plus the laws of Newton are sufficient to travel anywhere in the Solar System.
@@G5rry Not true, relativity has to be take into account otherwise you'll end up off course.
Yeayyyy..Amy is back ❤️
😛
all I see is her front
Voyager missions are seriously underrated considering how colossal of achievements these are...
Nice video Amy! Only thing that I would like to see added to a video on this topic are specific numbers on how much velocity a spacecraft gains when doing a flyby/slingshot/gravity assist.
It made the concept of how these work and why they are so useful & important when I learned that Voyager 2 gained about 10 km/s at Jupiter, about 5 km/s at Saturn, about 2 km/s at Uranus, and lost about 2 km/s at Neptune.
Keep up the good work Amy! Can’t wait for your X-Planes series!
Both VOYAGERS were incredible! They were amazingly successful at a time when we in the USA really needed something of ours to cheer for even if it WAS a robot probe we had sent far, far away in a galaxy we're just beginning to explore.
New video from Amy hell yeah!
I love listening to you speak. Your voice is exactly what my hearing range picks up. Too many rock concerts growing up in the 70’s but the music was so good. Plus you’re smart. It’s always interesting. Whatever you’re talking about, it’s something I’m learning. I went into a completely different work environment with a different education. So I enjoy this channel.
Amy, I have learned so much from your little corner of the internet! Thank you so much for these wonderful videos.
Long time listener, first time caller! By that I mean I have watched and enjoyed your channel immensely for many, many years, but I think this is the first time I have commented. I find you fascinating and greatly admire what you have done with your passion. You have created your channel from scratch and powered your career all by yourself. I just finished your first book and it was amazing. I love the topic and your writing skill is excellent. Your next book is on my shelf, soon to be opened. I know I will love it as well. And I look forward to book three, which I'm sure is cooking in your lovely head. I just love how you have created your career out of your passion and your own initiative. Well done!
Your a hero to my 10 year old daughter, she was tired of geeky Men. She wants a career in aerospace and you helped make her feel its all possible... thank you
It is not accurate to say it is easier to get to Venus because it's closer to the Sun. Mercury is also in the sunward direction and it is HARD to get to. The problem is that in order to go sunward, we need delta-v to counteract some or all of the 30km/s we get "for free" just by launching from Earth - already screaming around the Sun at 30km/s orbital speed.
The reason it's easier to get to Venus than to Mars is simply because it's orbit is a little bit "closer" in terms of how much delta-v a minimum delta-v Hohmann transfer requires. These principles, as well as the critical Oberth effect, were well understood at the time of the Apollo missions. (In contrast, the Oberth effect was not so well known a decade or two earlier, and at that time space technology enthusiasts didn't think chemical rocket propulsion would be able to reach other planets.)
It's just random chance that it takes a little less delta-v to get to Venus than to get to Mars.
That said, it's actually not obvious how you use a gravity assist at Venus to get to Mars. It's far more obvious how to use a gravity assist at Venus to kill off some sun-centric velocity because your transfer orbit will already have a faster sun-centric velocity than Venus. This is what the Parker Solar Probe did, as well as MESSENGER. But it is indeed possible to use Venus flybies to help go "outward", even if it's a bit harder to comprehend.
Galileo probe used one Venus assist and two Earth get to Jupiter. Cassini probe used an Earth assist.
@@RideAcrossTheRiver Yes, but the sophistication of the simulation calculations required to derive those navigation plans was far beyond the capabilities available around the end of the Apollo program. The Voyager plans were simple and straightforward in comparison, doable with manual patched conics calculations.
Amy does a great job of explaining things that are easy to understand without getting into the complexities of orbital mechanics.. Thank you Amy.
Hi Amy, nice to see you back. Another great video, thanks.
Well my day just got better by quite a bit!
Thank you so much!!
Side note: That lamp is nice!
50's Amy, so cute, so clever and a world class communicator, mastered so much and given your cat the best name ever!
Give Pete a pet for me.
As always a really informative & polished video. You never fail to teach me something new. Thanks, Amy! :)
So glad to have watched another one of your videos. It's been a while. Good one as always. Thanks for sharing.
Excellent video!! Very well thought out and presented, as usual. Cheers!!
Always exemplary stuff from Amy. Terrific!
Yes. Now I know a lot of stuff I didn´t know I didn´t know, which is precisely why I come to this channel. Thanks, keep it up, I am a captive fan.
As usual, this is been a very interesting video, Amy. Very nice to see you back.
Enjoy your take on this. You are a great communicator Amy.
best explanation ive heard of a really complex thing to do. I kinda understood it before, but you put it so well. such a superb orator.
Excellent books, love em. keep it up!
And dang, that is a cool dress....
I love the explanation of gravity assists in the context of early spaceflight. But two slight physics corrections:
1) A transfer going toward the sun does not necessarily cost less delta-v than a transfer going away from the sun. They both involve changing your speed (kinetic energy) relative to the Sun to affect your orbit (potential energy), a trade-off required by conservation of energy. In other words, the orbital speed from Earth prevents the craft from reaching areas closer to the Sun. A dive into the sun would require canceling out Earth’s orbital speed (30km/s), which is much more than a simple escape from the solar system (42 - 30 = 12 km/s required). Note that starting in Earth’s gravity well actually makes both of these values cheaper because of the Oberth Effect, also related to kinetic energy.
2) Gravity assists don’t just affect the speed “and” deflect the trajectory. They affect the speed “by” deflecting the trajectory. Conservation of energy states that from the planet’s perspective, the craft is approaching and departing with the same speed (kinetic energy), just with a deflection because of the hyperbolic trajectory of the flyby. But when switching to the Sun’s reference frame, a deflection of the craft’s trajectory toward the planet’s direction of motion (which you can see in the Voyager gravity assists) makes the speed more additive with the planet’s orbital speed. So the added speed is made possible by the deflection of the trajectory, but the video does a good job explaining that both of these are independently useful for the mission planning.
And a more minor nitpick: New Horizons passed closer to Pluto than Charon gets, but did not go between them, it passed the far side of Pluto from Charon.
Nice to see the new video style. I enjoy more in-depth videos like this.
More superb info from the Amazing Amy. Many thanks for taking the time to make these vidios.
Love the vintage lamp Amy. I had one like that in the 70s. 🇨🇦👍
What vintage lamp?
I love this stuff. Used to work out these trajectories in the Orbiter Spaceflight Sim a lot. It's desirable to get to Mars faster than a Hohmann transfer to avoid the long 9 month transit with its freefall and radiation, but the quicker you want to get there the propellant needed ramps up fast. So, instead, you launch the Mars ship unmanned into a solar orbit and then, about a year later, use the Earth itself to do a gravity assist to put the Mars ship on a faster trajectory to Mars, and at the same time, you launch the crew in a lightweight capsule to transfer over to the Mars ship for the long ride.
I don't think what you said about the Sun's gravity is correct. "But even though the Sun has such a powerful pull, it's surprisingly hard to actually go to the Sun: It takes 55 times more energy to go to the Sun than it does to go to Mars."
Planets are closer to solar escape velocity. It takes much more fuel to decelerate a spacecraft such that it will fall into the Sun than to get it to move outwards away from the Sun. We have objects leaving the Solar System now, but no man-made object has ever made it to the Sun.
Thanks for another entertaining and informative video!
This is a minor thing, but I want to point out an issue: It is not actually any easier to move 'down' a gravity well than it is to move 'up' it, at least if you're already in orbit. It takes a LOT of energy to get something into a circular orbit around the sun, so a lot of energy needs to be removed to lower an orbit.
For example, the orbital velocity of Earth is 29.8km/s while solar escape velocity from Earth's orbit is only 16.6km/s. In other words, you have to slow down more to reach the sun than you have to speed up to leave it entirely. The Mars/Venus situation is a similar story. Despite being closer, Venus is more difficult to reach. The reason for this is pretty straightforward, really. Gravity increases according to the inverse square of distance, so orbital speeds must also increase proportionally.
Rather than thinking of gravity like water circling a drain, think of orbits as representing energy levels. As you move inward, the difference in energy between levels gets exponentially larger, and as you move out the differences are exponentially smaller. In this sense, gravity becomes more like climbing a mountain than going down a drain. At least when you're talking about moving between different orbits. There's really no analogy that perfectly captures the weirdness of orbital mechanics.
yes exactly, the water falling a drain analogy is really bad because it implies an orbit could degrade naturally just because of the sun's gravity, which is the opposite of how that works
Once again Amy, another stand out video. I always look forward to your videos, I could listen to you all day. You are clearly very intelligent, such a great memory, professional and captivating presentation, clear speech and an obvious passion for this field. You always provide a wealth of information on all of your videos and go over and beyond and in such fine detail. Thanks for all the work you put into these videos for us. Dean.
The crucial phrase is "speed relative to the Sun," otherwise some people get confused wondering why a spacecraft climbing away from a planet doesn't lose all the speed it gained when falling in. Teacher Dude noted Heinlein's "The Rolling Stones." But that "gravity assist" involved a burn at perigee, thus dumping some of the mass involved during approach, as well as the value of the burn itself.
Hi Amy, glad you mentioned the Horizons Pluto Probe. It did show Spectacular images of Pluto last year. Also, glad you know of the Hohmanns Transfer Gravity Assist and I also think this assist using Venus Gravity to either go to Mars or return, in shorter time. If the delivery of Astronauts or of course 1st supplies, fuel, air and equipment as well as secondary gear. To return samples and Astronauts. Incidentally, I think there should be a separate craft to return the samples. To keep Astronauts craft light weight and safe for them to carry sustainable rations for return. Back to Venus if Mars is on far side and Venus is Trailing slingshot to Mars a quarter of the distance. Explorations, and return within a fewer months back to Earth as it catches up to us. Though, still think should go to Mars Moon and explore the Obelisk. Thanks Amy awesome presentation ❣🚀🙋👍🛰🪐🌌🌠☄
@Amy Just in case you're interested. The Canadair Sabre in 1/48th scale is now available from Airfix.
Fantastic episode. I have bought both of your books because you really can tell a history of the people doing the cutting edge of scientific endeavour. I also recognise your excellent fashion sense. You make every episode a journey of intrigue and I most humbly thank you .
Gravity assist was used for the Apollo moon landings, hence the famous "free return trajectory".
Wow, Excellent explanation of a not-so-simple subject.
I set the YT video to 144p, so I can listen like it's an audible book, with an optional video. GREAT audio quality, AST.
Awesome explanation of how Flyby's work!!
Thank you for covering one of my favorite space tech topics.
Thank you Amy, Pete & others! I very much appreciate the amount of time and effort you put into this channel. Looking forward to the next one.
I was trying to teach this just yesterday. Wish I'd spotted this video earlier!
What's amazing to me is that the concept of "Gravity ASSIST" was mentioned all the way back in STAR TREK TOS when KIRK remeets the gaseous entity which almost killed him and his fellow crewmates when he was a young Ensign on his first deep space mission.
You've got the best videos. Keep up the good work.
I've wondered about whether gravity assists could and were used as breaking maneuvers, thank you so much for covering that aspect of it.
Thanks Amy - this was excellent 😃
Id say the coolest part of all this, is now I see you on the History Channel Too! Hell Yeah space stuff. They just need a space based show with just you and Alex Fillipanko and id be content
Thanks Amy, this makes more since when you explain it. Keep the video's coming. 🚀
Fantastic video! Thanks for your effort and information!❤🙏
You know, this one was really helpful and interesting! It's just unbelievable that we can do this! BTW, my daughter loves the various outfits as much as she loves the space talk! Thanks for making it fun!
I don't think it's delta-v that is needed for an object to slingshot around a planet instead of falling on it. That is, it doesn't need to create delta v (=accelerate) itself. If the initial velocity (just plain v, no delta) is high enough, it won't fall to the planet. Saying that a spacecraft needs just the right amount of delta-v may be interpreted as if it needs to actively accelerate with it's engines, and I think most spacecraft passively enter a gravity well and don't need to use their engines (except for small corrections or to slingshot out at a shallower angle). I'm not that familiar with physics, so if anyone can confirm or refute...
You're a wonderful teacher Amy
and love your posh too 😼
Very interesting topic, thanks for the time to make the vid.
Great episode, never knew about the propose Apollo era Venus fly-by proposal. Thanks!
In his 1952 book, The Rolling Stones, Robert Heinlein describes the idea of 'gravity assist' repeatedly. Alas, we are not about to holiday on Mars or Venus any time soon
Most of the ballistics in Heinlein's books are either correct, or plausible. The problem with his books is they almost all depend on nuclear fission or fusion propulsion in some way, and the engines in his book are not really feasible. Bob was really anal retentive about all his ballistics, including those in _The Moon is a Harsh Mistress_ and _The Cat Who Walks Through Walls._ However they don't really work unless you have super efficient engines (In _The Rolling Stones_ he mentions that the engine is nearly 100% efficient.) with unreasonable specific impulse.
But this leaves unanswered a question: I can understand how this changes direction, but how does it change it's speed? Wouldn't it lose all the speed it gained on the approach when it escaped?
Good question/observation. The answer being that what gives the acceleration (or deceleration) isn't the the gravity of the planet itself, but the velocity of that planet around the sun.
Best thumbnail ever❗️
Love The Galaxy Gal we all know as Amy...She Is Cosmic Comfort! Cheers Everyone
Thx u rock 😄
Galaxy Gal!!! Amy is!
She's never looked better!!! But still it's the quality of the videos still remain top notch
Great explanation, Amy.
None of this would be possible with out proper mathematics. I find Mankind's ability to conquer such feats absolutely fascinating.
Oh yeah. The orbital mechanics are amazing on its own. Figuring out how to use that and the masses of the planets to accurately pinball spacecraft around the solar system is more than amazing.
All thanks to Kepler and Newton.
And it's a shame with all that ability we can sort out everything thing that's wrong with mankind.
Mathematics is the language in which God has written the universe
If Amy was a teacher, her students would become the leaders we need to MAGA
Excellent and informative as always!
Great explanation of a complex subject Amy. Perhaps you could make mention of Michael Minovitch, who in 1961 while working for JPL published his theory of Gravity Propelled Interplanetary Space Travel. He enabled the exact calculation of gravity assists and opened up the Solar System for exploration.
I know this vid's about space, but: that Micheline Pitt dress is out of this world.
Superb channel. Or as Bogie 78 years ago said to Ingred Bergman's character in "Casablanca"... "You... your very good!"
Hi Amy, another way to save propellant/fuel is aerobraking. I wonder if you'll cover that. Rather than use fuel to slow down a spacecraft to enter an orbit, you just approach a planet such that a speeding spacecraft crashes through the upper atmosphere at just the right angle so that it doesn't slow down enough to land but just loses enough velocity due to the atmospheric drag/heating such that it passes through the atmosphere and re-emerges into space around the planet now in a stable orbit at a lower velocity . I do this all the time when I play Kerbal Space Program so I don't have to use rocket fuel slowing down to enter an orbit. :-) Of course you can only do this on a planet with an atmosphere so it wouldn't work on the moon. As long as your heat shield is good enough you can put a spacecraft on a super-fast trajectory to a planet and angle it really deep into the atmosphere to really get it to slow down and the only fuel you use is a very minor trajectory burn when you're way out instead of a braking burn. I remember the film/book 2010 depicted this maneuver and it works fine in Kerbal. Would it work in real life?
a delightful surprise on a Friday afternoon - ty Amy - 🛸👽💚
Oh, the beautiful ballet of physics!
Very well explained! Thanks for that!
This is a fantastic video, thanks Amy you are teaching my son and I so much! (Also your books are awesome!)
0:54 the thing about it being easier to go to Mars via Venus than going direct to Mars is often misunderstood. It’s not actually easier to get to Mars that way. But, a round trip to Mars and back has a shorter duration if one leg (but not the other) goes by Venus. A shorter duration crewed mission requires fewer supplies, and consequently less mass, and so the total mission is easier. But, for a 1-way mission to Mars, it is almost always easier to go directly to Mars without a Venus fly by.
Great explanation! thank you!
Oh YAY! Mini series about X Planes. I look forward to that one.
Being very familiar with your topics, (I lived thru several), your delivery is FANTASTIC! A good balance of whimsy and hard science. If your in the Wichita, Kansas area again, please contact me. I would like to take you stargazing.
A lot of information transferred to my brain from being so close to your video. Thanks
Thanks Amy for your video
Another fine job, Amy. Really good! Thank you! ✌️❤️🍕
Well done, Amy, and yes, i learned more than I expected.
Questions I didn't know I had, indeed. I didn't even think to question why we don't use Venus assist instead of Hohmann Transfer. It makes sense, though, the way you explained it.
This was great, I will recommend it to my co-workers.
In the simple sense you don't get caught in an orbit if your relative speed is "low". Mathematically if you have above zero "surplus of escape velocity", which you do by definition when you are arriving, you will exit the gravity well at the same relative speed. The reason you can get caught is if you hit something inside the gravity well or are affected by uneven gravity field, like the effect of moons or tidal effect of the sun - which has more to do the "where" than "how fast".
The most instructive way to think about gravity assists, IMO, is to realize that you leave the gravity well of a planet at the same speed you entered with relative to the planet, all you can do is change the direction by deciding how close and on what side of the planet you pass. The benefit after leaving the planets gravity well is derived from the fact that the planet is moving, which means that if you change direction along the axis of motion of the planet, you will change your orbital energy in the outside system.
If you take a look at the Voyager gravity assists, you should notice that the common theme on this outbound trajectory is coming up to the planet from below and leaving out front of it in it's orbit. Slowing down means you come in from the rear and bend in some other direction, thus slowing down in the surrounding system.
Scott Manley, of course, has a video that explain it well.
Thanks for sharing!
Playing KSP helps you visualise gravity assists really well. Also, don't forget the Oberth Effect! Also known as the Manley Effect. 😜
Orbiter is a more accurate sim, and you can recreate historical missions pretty accurately.
@@RCAvhstape KSP + proper mods (such as Principia) can be accurate enough.
Thank you Amy. I learned something.
What's with the audio? Is my codec broken or is the audio constantly clipping?!
Excellent job!
I just made a video montage of David Bowie's song I took a trip on a Gemini Spacecraft with Gemini clips, I was already happy, Amy uploads a new video, I feel much happier :3
I went to your channel to see The Thin White Duke in this Montage Video....is it posted somewhere else?
@@TheStuport Oh, yes, it's in another channel, search for "Mister X I Took A Trip On A Gemini Spacecraft", for some reason I cannot post the link here.
Nice work @@misterx168
Thanks Amy! That was great!
Good stuff. Voyager 1 an 2 are fascinating.
you may need more sound treatment, the audio seems to saturate in the high frequency range.
Agree. Clipping?
Hi Amy,
Sorry to say, but your explanation of gravity assist is not quite correct.
Basically, gravity assist is very simple. A gravity assist just a change of the directory of the velocity vector of a spacecraft relative to a planet. If the vector of a spacecraft is changed in the direction of the planet's velocity then the velovity of the spacecraft is increased. If the vector of a spacecraft is changed in the opposite direction of the planet's velocity then the velocity of the spacecraft is reduced. That's exactly why the apollo 11 made a 8-ciffer like flight to the moon. The purpose was to reduce the velocity to help the spaceraft to go into orbit of the moon; otherwise the spacecraft would have been catapulted somewhere else.
This said, I love your historical expertise in all your videos.
Thanks a lot.
Yes, I wondered about this for years. I would always hear some knowledgeable space reporter talk about how Voyager would "gain speed" as it would "slingshot" past Jupiter. And I would think, won't it lose all the speed it gained going "in" as it passes the planet and goes back "out?" It has to. Finally, after playing with Orbiter and studying the Bate book, I figured out that it's the change in direction that is what matters. You're going the same speed as before but that speed is pointed in a direction that is going to get you further out in the Sun's sphere of influence.
Watching Space X RUclips videos: Space flight is easy.
Watching The Vintage Space: Holy Crap! Space flight is f***ing hard as hell!
Thanks, Amy!
Great video Ma'am.
I love the vintage fashion. The giant sexy brain is just the icing on the cake.
Thanks Amy and very nice dress. Congrats.
I’m not sure if you ever covered vintage computers or the people that did the computing before the machines. Keep up the great work. I love the math and science parts in your vintage space.😁
It seems to me that one other disadvantage of using a Venus gravity assist to reach Mars is that more delta-v (or more strenuous aerobraking) would be needed to slow the spacecraft for orbit or landing. It would work for a fly-by, but that wouldn't provide much time for useful observations.
Outstanding as always. My wife and I wish you the best. Pete? Where's that furry little space ball of fuzz? My cars are his biggest fans.....Be safe and thank you...
Hi Amy,
Vintage Space is awesome, I do enjoy your channel. You say that "vintage" is your thing and no doubt the 50s and 60s space effort was fascinating. I myself am a child of Apollo. I'm in. A friend of mine, a physics prof in Boston, told me recently that in one of his courses he talks about how designs and concepts have trended backward with the advent of SpaceX using modern technology. It had never occurred to me before. Of course he's right when you think about it and that made me think of your channel. The entire look of the Starship and Super Heavy stack looks a whole lot like something Von Braun might have come up with. The reusability angle also I think would have appealed to Werner. If only he had had access to guidance and control systems that we have today, not to mention the alloys SpaceX is using, what might Werner have been able to do?
Also, I think you'd look badass in one of those vintage clothing get-ups alongside a Starship! 😊
So maybe a cool video topic might be "Would Werner Von Braun have made Starship?" That's a lot to unpack. That's my two cents. Thanks for the great information you supply to the public!
Great topic. I had to bail at about a minute because the audio was pretty uncomfortable to listen to. Confirmed on good headphones and home theater system.