Orbital mechanics can be oddly unintuitive at times, so I set out to cite a few examples where the most natural thing to do it the opposite of what you want to do.
Uejji Especially the good ones, because before Kerbal there was nothing unrealistic enough to halt the suspension of disbelief. After Kerbal there's not a single SciFi movie that has nothing wrong enough with it to suspend disbelief. Ignorance about orbital mechanics is bliss.
Understanding of orbital mechanics: Completion of physics A-level: 5% Completion of astrophysics masters: 15% Completion of first KSP "orbital rescue": 75%
I'm afraid I'm still at the 5% level. After that I went into electrical engineering. Much simpler for my simple mind. I stand in awe of those who understand orbital mechanics.
I complete most of my orbital rescues by pointing directly at the target and having an engine powerful enough that my orbital velocity doesn't really matter that much. Might be less efficient, but it is way faster.
Playing KSP is an amazing way for simple orbital mechanics to click. It gets really intuitive when you can visualize the resulting orbit in your head and understand how burning prograde at apoapsis raises periapsis etc
They'll sacrifice realism for dramatic effect any time they perceive that profit can be made from telling a good yarn. And any time that realism costs more than inaccurate but spectacular special effects.
the thing is, realism can often _add_ dramatic effect. remember the scene in hunt for the red october, where ramius turns the sub to face the torpedo (which was stupid for several reasons, but technically correct)? reality is full of great plot twists waiting to be used.
I can live with unrealistic technology that allows something like flying with speeds near the speed of light, HOWEVER, a film should never disobey physics too bluntly. Is it ok if we can disable gravity, or have infinite energy? YES. Is it okay to point towards the earth with existing technology to deorbit? NO.GOD:PLEASE:NO:NOOOOOOOOOOOOOO
And really everyone making any kind of animation of a rocket launch/deorbit. I remember watching an animation on the news of the Soyuz capsule leaving the space station and landing, only to groan as the little animated rocket fired away from Earth and then proceeded straight down.
Buzz Aldrin is the man. He had a plan worked out to navigate using handheld instruments taking sightings out the windows and doing the math himself. A true astronaut.
I like how Scott keeps it very professional and explains everything, ignoring the passive agressiveness and rudeness of the comments who think they know more than him
Aldrin was an orbital mechanics bad-ass. After the Apollo program he worked out the math behind Aldrin Cyclers, hypothetical craft that would permanently orbit the sun and periodically pass by Earth and Mars. Passengers to Aldrin Cyclers would randezvous with tiny craft to then enjoy the bulk of their trip to Mars in luxury. On close approach to Mars the travellers would use their tiny craft for the final leg while the Cycler would continue in its sun orbiting.
I'd be curious to see how that's supposed to work. Seems like rendezvousing with the cyclers would require getting up to the same speeds they were already at. I guess with a light a light rendezvous craft, the proposed savings might be in launching a relatively small craft to those speeds without the need to haul a couple year"s worth of supplies. But those supplies would eventually have to be launched and received.
Even during the Apollo program he was a badass, his PhD thesis on orbital rendezvous formed part of the NASA flight procedures- tranquilitybaseblog.blogspot.co.uk/2012/12/dr-buzz-aldrin-and-orbital-paradox.html
The main advantage is that you can make the cycler nice and spacious with mass intensive things like centrifuges or gardens, and not worry about having to move that stuff around every flight.
The idea would be that the large cycler ship would have all of the life support systems and everything else needed to maintain a crew in comfort and safety on their voyage and it would only need to be launched once. After that crew and resupply missions would be much cheaper to launch because they don't have all that extra hardware
It's all in the amount of mass that needs to be brought up to speed (and brought down from speed on arrival). As to the consumables: a sufficiently advanced cycler could be self-sufficient. Rather than bringing years worth of consumables in the randezvous craft the cycler could be equipped with a closed-loop life-support system. The randezvous craft would then only need to pack enough consumables to tide the passengers through the randezvous, a few days worth perhaps. This concept was used as a plot point in 2312 by Kim Stanley Robinson. The central characters spend considerable time on cyclers the size of O'Neill cylinders as they make their way from Mercury to Venus, Earth and Saturn. It's a multi-year commitment and they're encouraged to take up jobs on the cyclers and live alongside permanent residents.
Mr Manly all that this means is: a spaceman/woman could jump off the spacestation, do 1 round around the planet and get back on the station after that. If the math was done right and there would be no depris... i think you just descriped a new futrue extremsport ;)
Skyven Razgriz: I doubt that the two would meat at the intersection points of the two orbits at the same time, because their speed are not in sync. They generally would miss each other.
Skyven Razgriz Does not work. As you jump of the space station, eg retrograd (which means in the opposite direction of movement), your orbital velocity slows down a little bit. This has the effect, that gravity will pull you closer to earth, which has 2 effects: you are speeding up again and since you are now closer to earth the path around earth is shorter. Yes, after 1 orbit you will end up in the same spot you left the station. But it takes the station more time to reach that same spot. Thus you will miss the station, you are back too early. If you jump prograde (in the same direction as the movement) the oppsite happens: you increased your orbital velocity which has the effect, that your centrifugal force increases. Thus you will drift outwards, away from the earth. This has the effect, that your orbital velocity will decrease again and that the path around earth is longer then the path of the station. Yes, after 1 orbit your ellipsis will bring you back to the spot you left the station, but the station will have passed that spot before you. You are too late to meet with the station. This is what Scott was talking about. If you want to catch up with an object in orbit before you, you actually need "to pull the breakes" to coast into a lower orbit in order to move around earth in less time (because your path is shorter) then the other object.
I remember reading a Clarke story about some folks who tried to strongarm a crew by taking the lead scientist out in a space suit, shutting off his radio and pushing him down toward the planet. The crew panicked and went along with the demands, but of course he showed up again instead of plummeting down to the planet (this is why they shut off the radio, as the scientist would otherwise have explained it to them). I was just a kid when I read this, and did a fair amount of research and thinking, before coming to an almost-correct conclusion. I realized that by pushing him down, they'd changed his orbit's eccentricity, making it more elliptical. What I didn't realize was that the center of the ellipse wouldn't be the same as the center of a circular orbit, that center (the planet) would just be at one focus of the ellipse (something your graphics show nicely).
so when youre doing work on the iss and you float away toward the earth you dont fall into the earth, you come back and hit the station? thats weird.. is that sort of like creating a lagrange point?
@@thothheartmaat2833 Yes, you're still moving at orbital velocity, the same 7600m/s the ISS is, but you've added a small change in direction (probably less than a meter per second). This makes your orbit slightly more (or less) elliptical, but the two orbits will still cross at a couple of points.
@@Eclipsed_Archon Sorry for the delay, it took a while to dredge it up from a bunch of related stories. It's called "Jupiter Five" (1953), originally published in "If" magazine, and in several collections ("Reach for tomorrow", "The Collected Stories of Arthur C Clarke", "Across the Sea of Stars" and "Sentinel"). Several of the concepts in it (but not that plot point) showed up in Rendezvous With Rama, published 20 years later.
@@johnrehwinkel7241 Thank you so much! I feel like I've heard the title before. Definitely going to give it a read, The Collected Stories looks like it'd be a great addition to my bookshelf either way.
1:00 -- In a Larry Niven novel, the mnemonic used was, "Down takes you East; East takes you Up; Up takes you West; West takes you Down. North and South bring you back."
Anvilshock With Up and Down you also get large changes in the East/west velocity, whereas with North and South, there isn't. It takes a very precise velocity on something thrown Up or Down to get it to come back close to you an orbit later. To get the same result with something thrown North or South requires much less precision.
This kind of stuff is why I would love to have a space battle game that would be situated in orbit around a planet. Maybe scale down the planet's size to increase the effect of these kinds of mechanics.
You should totally check out Children of a Dead Earth then! It's pretty much exactly the thing that you are describing here, and Scott Manley has done a couple of videos about it in the past as well.
Kerbal space program has kinda ruined sci fi space ships for me for this reason. Real space battles would be insanely difficult, basically impossible. Also it's pretty easy to rendezvous in KSP once you get the hang of it but I'm sure it would still be insanely difficult to do in real life without all the planning tools and attitude alignment indicators.
One of the plans for longer duration Apollo missions that never flew featured a Lunar Escape System (LESS) if astronauts got stranded on the moon due to failure of the lander. The plan was to siphon fuel from the lander into an escape vehicle, which consisted of essentially a 2 person rocket-chair to manually fly up into orbit. They would not have had a guidance computer or altitude indicator. They would have had radio communication, an attitude indicator and a sextant. They would track the CM and fire themselves into an orbit after it has passed over head, using a sextant to guesstimate alititude etc. The CM would then enter times and angles that the LESS had been seen, which it could do from 10-15 miles away, plus further with radar. The LESS would have to put itself in a pretty descent orbit in order to be picked up. If they managed it, then the CM would do two burns with the help of the guidance computer to put itself into their orbit and rendesvouz before they ran out of air.
+soylentgreenb The book version of "The Martian" had the "hero" travel to a return-to-orbit booster that had been abandoned at a different location, that didn't have enough fuel left for a normal liftoff, tear off every bit of extra weight he could, resulting in basically a rocket propelled chair. He thought it nuts too. But wait, it gets worse... The rocket chair cut off just a bit too early, The recovery ship (the ship that left him on the moon thinking him dead)'s orbital burn was going to miss him by just a bit too far. So they impromptu blew an airlock door and let the air in the ship blow out give a bump in the right direction. But wait it gets worse... Still not enough, so an intrepid crewmember jumped out of the recovery ship on a rope to grab him, but wait, it gets worse .... but the rope was too short... So he let go of the rope (with the captain screaming at him not to), hooked "The Martian" out of his chair, and boosted back towards and caught the rope.... Sucky mission plan. But it was fun reading. Niven and Barnes' Descent of Anansi is good fun with orbital mechanics.
@@395leandro It's actually very much correct to use the word "literally" as an exaggeration of something that isn't actually literal even Shakespeare did it in his plays.
@@395leandro It does have that meaning but it's been used by many writers as a hyperbole for centuries, many words can have multiple meanings depending on context.
Well mentioned! Buzz's PhD thesis was a fantastic help for myself and I'm sure, others in getting the hang of catching other objects while in orbit (in KSP and Orbiter). Thanks, Buzz!
Scott, could you allow the community to create subtitles for this video in the video settings? I'd love to translate it so I can share it here, your explanation was great!
This video reminds me of something I did in KSP a while ago, about an expansion to a space station: I jettisoned the booster from the module when I got it in orbit, which in hindsight is its own terrible idea as debris builds up really quickly in KSP. I then set up a maneuver node to get the craft closer to a space station I wanted to dock it to, which involved waiting a full orbit. As you've shown in this video, the orbits have the same period and intersect with each other, so it's pretty obvious that the booster would crash back into the rocket. And that's how I lost 148,000 funds in career mode. Another story with things that go boom, but I think this one goes better as an argument between Jeb and some idiot on Ground Control (GC): GC: "Detach the nosecone!" Jeb: "No I have a prograde burn soon and if I detach it now I-" GC: "Shut up and push the button!" Jeb: *A button is pushed and a decoupler fires* GC: "Begin maneuver." *Throttle up, GC hears the engine over the comms.* *GC then heard an explosion* GC: "What was that?" Jeb: "The nosecone you made me detach. You didn't even let me angle the craft to put it in a differently inclined orbit." GC: "Ohh..." *Jeb hears a facepalm over the comms.*
Here's a fun idea; see what it would take to (in KSP) achieve a Mun landing, while doing exactly the intuitive thing that goes against orbital mechanics. i.e, thrust straight down to lower orbit, thrust straight up to raise it, and generally perform your maneuvers in what is usually the worst way.
yeah, the thing that this video doesn't really mention is that some manoeuvres that don't work only don't work from an efficiency perspective in terms of our current level of technology. For example, burning radially in/straight down rather than retrograde actually gets you to a body's surface in about half the time, pretty handy if you're running late for your date with a Martian; however, it is a very expensive (about twice as) method of doing so, and you still need to burn to an acceptable landing velocity assuming that body has no atmosphere or, if it does, that the craft has adequate shielding so that such a burn is not necessary.
If you throw enough energy/deltaV at the problem you can fly in close to a straight line, it's just that with the same amount of deltaV you'll get more done with the less intuitive orbital manoeuvres than with attempts at direct flight that forget/ignore that you're not in an inertial reference frame and have substantial relative velocity in another direction.
Transfer time is a major factor to consider when choosing if you want to go efficient or not. The main example where you'd take time over efficiency is interstellar travel.
If you thrust 'down' (towards the body of mass you are orbiting) at perigee (or anywhere in your orbit), then all you are doing is basically rising your apogee.... For any of you who don't understand this concept, try it in Kerbal Space Program, physics is a pretty fascinating thing :)
Give KSP a go. I probably wouldn't have understood this before I played the game, but now I find it extremely simple to understand - so much so that it becomes difficult to understand that others do not understand this. Kinda like how if you can swim it's hard to understand how somebody else, who is not a child, cannot swim at all, or is unable to move or simply not sink.
Actually, I do have it in this box of bits and bytes but there is only one of me and only so many things I can do in a day with my health being the mess it is and even with as much as I like space things if given the choice between being able to do a bit of KSP or Trainz railroad simulator I will do the trains first.
This was literally my favorite video to date. At first, you wonder why throwing something directly towards earth and its gravity wouldn't work. Your explanation was very precise and made perfect sense, including slowing down and speeding up (in your space station example). I love being challenged and this forces you to take many things into account. Absolutely awesome video!! Ty!
Many years ago a friend asked me a riddle: Forward is up, up is backwards, backwards is down, and down is forwards. Where are you? The answer, of course, is "In orbit."
@@meh.7640 In an ambulance, though, typically while forward is up, up is forwards. Down is backwards, and backwards is down. They _usually_ put you in head first. If they put you in feet first, however, you'd be dead on!
I had never guessed that you can't throw a ball from ISS down to the Earth. I would've guessed that the ball had followed ISS around the Earth for a while before it entered the atmosphere, depending on the force of the throw, but I failed to realize that the vector of the ball will be in reference to ISS and not to the Earth. I'm a bit shamed to admit that I didn't knew that ISS turns around its own axis as it orbit the Earth. I've never thought of it. You did a great job explaining this. Thank you!
Scott, thank you for your excellent explanation! I found this in a magazine: In 2007, US astronaut Clay Anderson “[…] grasped the reservoir after Russian astronaut Yurchikhin disconnected it, rode the arm to a point below the station and pushed it off like a basketball. The station was flying backwards at the time, allowing Anderson to send the non-longer-needed reservoir and another piece of junk […] in a retrograde orbit relative to the station to avoid recontact later on […] the station used its thrusters […] to re-boost its orbit above the retreating debris […]”. Frank Morring, “In Orbit”, AW & ST (July 30, 2007), 15.
KSP is definitely one of the best tools for re-programming our intuition on gravity and orbits. I'm guessing that almost all of us tried shooting our rockets straight up at first =p I never got used to the lateral adjustments in orbit, I probably should go back and toy with that some more.
This is EXACTLY the same thing that happens when you throw stuff while standing on Earth. It's just, you know, the planet and atmosphere tend to get in the way very quickly.
Minute Physics did a video on why it's not faster to travel against the direction of Earth's rotation, then with it, and that's about what it boils down to. Physics will little note, nor long remember, our ability to add or detract from our speed compared to the Earth and its atmosphere.
Well you know what you gotta do now. You gotta jump with a Kerbal from the space station and see if they'll swing around the planet and land back to where they started!
Larry Niven came up with the basics of this in his Smoke Ring series: If you apply a thrust eastward (in the direction of your orbit), you put yourself in a higher orbit (you move Out); If you apply a thrust Westward (against the direction of your orbit), you put yourself in a lower orbit (you move In); If you apply a thrust outward, you put yourself in a slower orbit, so you move West relative to everything else in your old, faster orbit; If you apply a thrust inward, you put yourself in a faster orbit and you move East relative to everything else in your old, slower orbit. If you thrust to the left or right, you move to an orbit that is at an angle to your original orbit, but which intersects your original orbit at two points, one of which is the point at which you applied the thrust - hence you come back to where to started after one orbit.
It's kind of funny that a few days ago I mentioned to my brother that firing away or towards earth would do exactly what you explained. It's nice to know my understanding of orbital mechanics is fairly good. Actually came up because of an episode of the old Mission Impossible series, where one of the characters gets thrown away from a space shuttle. I mentioned if she went at 90 degrees to the orbit she'd come back after an orbit. The only problem would be that she came back on the wrong side. In the show she vents oxygen from her suit to get back, which isn't exactly something you want to do while trapped in space.
Wow...so when we see these movies where the astronaut gets untethered from the ship and falls toward the planet where we assume he's going to burn up, all the ship had to do was wait for an orbit or two and he might be able to grab back on?
exactly. from what I remember the film Lockout 2012, the protagonist & the girl re-entered the Earth's atmosphere from an orbital prison (something like that). I don't remember if they burned any fuel in retrograde but from I recall they simply "fell" back to Earth despite lack of slowing down their horizontal velocity. A side note; from low Earth orbit [LEO] your velocity can be 6.9 km/s or 6900 m/s, from which you'd burn up simply from friction with the atmosphere (the typical reddening in re-entry depictions). good luck surviving that in an EVA suit.
Unless the ship was in a suborbital hop before achieving orbit (not sure if any spacewalks have ever taken place before circularization). For the most part movies do the "doomed astronaut" stuff pretty badly with either "falling to earth" from a sudden downwards motion or "getting flung out of orbit" with an upwards one (though getting stuck in a spacewalk for an entire orbit like that is still a lot of time without good radiation protection and limited air).
nomine you don't burn up from friction, but from compression heat. While moving through the atmosphere at high speeds, the air in front of you cannot get out of the way fast enough, so it gets compressed. And if it gets compressed, it heats up. Heat from friction plays a minor role.
Maybe. In an orbit or two he'll either be far away from the station, doomed to drift in orbit until someone picks him up or he dies, or he will bonk into the ship. It would, however, be trivial for the _ship_ to pulse its RCS a bit in the right direction and then our astronaut could grab back on.
Thx Scott, I have noticed you increased the amount of Vid posting over the last couple months.. I really do want to make it clear, that the service your providing helps a rather large amount of us.
The apparent paradoxes of orbital mechanics can be somewhat resolved by keeping in mind that there are TWO ways of "orbiting faster": the angular velocity, that is, the degrees per second (or whatever) around the parent body, and the tangential velocity in km/s or whatever. Increasing the latter decreases the former, so a craft travelling with a higher tangential velocity goes into a larger orbital path, which in turn results in a lower angular velocity.
I think, it is worth to mention Saturn moons Janus and Epimetheus here. Those two moons share orbit, but as they get closer and start gravitationally attract each other, they change so they change orbit heights and start to drift further apart.
Great explanation of orbital mechanics! Long before Kerbal, Orbiter, etc. and before the internet I had a NASA book, Exploring in Aerospace Rocketry, and went through lots of paper and calculator thumping doing the math I found in the book and trying to wrap my head around orbital mechanics. After a while it finally clicked. More of an "Ah" moment rather than an 'Aha" moment since that's when my brain stopped hurting. You've saved 22,000 people from a lot of pain, Scott.
This is just a lesson in relative motion. Throwing something backwards off a spacecraft does not mean it's moving the other way around the planet. Once you realise and can generalise that idea, planetary transfers make much more sense.
not just that. the presence of a gravitational field (i.e. the quadratic decrease with distance, although for low-earth orbits we first-order approximations do well) does make it more difficult to wrap your head around the dynamics orbital velocity (for circular orbits) gets _lower_ as your orbit gets _higher_
I love this... although the content of this video is not new to me. I am a total nerd that even worked for ESA (the European NASA) I really like how you explained it.
Excellent explanation of this piece of orbital mechanics. Manley studied astronomy and physics at Glasgow University so he knows what he is talking about.
Finally, i get it. Totally failed to understand the previous video. But it rises an other question to me: Can you shoot the object upwards, so after a half orbit it reaches the atmosphere and deccelerats?
think in vectors, gets quite obvious then. If you add a certain velocity it's added to all of the positions the spaceships will come to, so basically you shift the orbit in the different direction from that shown in the video.
Yes, essentially you're turning the orbit into an ellipse, if you can make that ellipse cut enough of the earth's atmosphere then the object will de-orbit possibly by burning up.
That was a great explanation. It also explains a lot about "circularization" of an orbit, that is, this same effect can be used to remove the elliptic from an orbit.
My initial reaction to the ISS ball thing was "that's not unintuitive at all, it makes perfect sense!" And then I realized that that's only because Scott did such a great job of explaining this stuff back in the day that my brain is used to thinking about things this way. So thanks for making this complicated stuff seem so intuitive that it feels obvious!
Wow! Finally..., I remember my father explaining this phenomenon to me so long ago... and I never really could grasp it. Great visuals. Hadn’t thought about it in 30 yrs. thank you Scott.
Thanks for the diagrams, I have wondered what would happen if a Spacecraft were to point away from the earth and fire the engine, I thought that perhaps it would result in an Orbit that had 2 high spots and 2 low spots, but it really just results in a less efficient way to change from circular to elliptical and back
Very good explanation, I just wanted to point out a couple things: 1) At 2:02 that resulting orbit of the ball is obtained when the station is moving clockwise. If the motion was counterclockwise the orbit of the ball would be the same, but shifted to the right and not to the left. Just try adding the velocity vectors as he explains later on and you see how it works. 2) For those interested, the maneuver shown around 5:15 is named Biellittic Transfer, and it allows to minimize the dV when the semimajor axes of the starting and ending orbits are very different. The drawback though is a huge increase in the time needed for the transfer.
"Don't be sad if you don't understand it, even astronauts have been confused by this feature of orbital mechanics." *Scott explains it in a couple sentences with KSP* =Everyone instantly gets it! 😀❤️
You mentioned that beyond a certain point, it's more efficient to first increase your apohelion and then drop your perihelion when you reach apoapsis, than to simply drop your perihelion right away. Is there a way to "eyeball" that threshold, or does it require significant calculation?
If the orbit youre going to is ~11 times larger or smaller than the orbit youre in, then this method (bi-elliptical transfer) can be more efficient than a traditional hohmann transfer. The apoapsis of the intermediate transfer needs to be sufficiently larger (~ 2x destination apoapsis) for this to be the case unless the size difference of the orbits is greater than ~18. In this case, the bi-ellpitical transfer is always more efficient than a hohmann transfer
Anvilshock, that number refers to the ratio of the orbital radii. So say, for example, youre in a parking orbit with a radius of 7000 km, if you wanted to use the bi-elliptical transfer, youd need to be going to a 77,000 km orbit, for it to be more efficient.
Anvilshock, perhaps its also worth it to note that the orbital radius is measured from the center of the central body to the object in orbit. So in my previous example, the altitudes of the two orbits would be closer to 250 km and 70,000km because the earth's got a roughly 7000 km radius.
Nononono, you don't understand. There is a difference between "times larger" and "times as large", and Anglophones appear to be particularly enjoying the confusion of the two, so I just wanted to make sure which one you meant. Also, "times as small" or even "times smaller" is completely and utterly incomputable because the "smallness" of the original isn't quantified at all, so you how could you even remotely reliably convey the result by applying a multiplier to something that is undefined in the first place?
Just remembered where I first came across this concept of performing a retrograde burn to achieve a faster orbit: 'The Descent of Anansi' by Steve Barnes and Larry Niven (1982). It's been lurking in a little visited tumbleweed area of my head ever since, and it speaks volumes about how my mind works to even remember 'Anansi' for me to Google it now, so it's great to finally have it so beautifully illustrated in your video
I hear the fireworks outside and my neighboors cheering as we just passed in 2022, while I'm watching this video and getting mindblown by these simple yet amazing explanations.
i might be saying sth very non-nuanced, but Scott built his channel on KSP. How new do u have to be to this, if u think throwing a ball straight at the planet will result in it falling to it and not just shifting the orbit, like Scott has done multiple times, as have we?!
I just saw the Homemade Documentaries presentation of Ed White's attempt at rendezvous with the booster. Orbital mechanics is hard. Anyway, well done on the explanation. I have so much to learn!
Great video, it seems so counter intuitive that you increase speed when slowing down into a lower orbit but once you’ve grasped the concept and played a few simulations it starts to make sense.
Lawrence D’Oliveiro Or put it in tiny pellets and inject into cancer tumors to kill them. But aim carefully to limit the damage to the patient while still killing the cancer! Fortunately, we have entire hospital departments dedicated to the task.
Finally clicked for me on a more intuitive level seeing the orbital diagram with the velocity vector added. I think despite being able to do the math, I was still mentally picturing a rotating frame where "down" was "down the gravity well" and not "the direction that happened to be down when I applied the Δv". Thanks for that!
When I first started playing KSP rendezvous with other objets really confused the hell out of me, until I watched your videos suddenly it all made sense.
So if two objects are orbiting the same planet at the same altitude, will they always have the same velocity? Will a 10 ton object at 100km orbit just as fast as a 50 ton object at 100km?
TheWindigomonster Yes. Mass of the satellite is not a factor in orbital motion. The mass of the main body and distance from its center are the only variables in the equation.
You are correct. The 50 ton object and the 10 ton object will orbit at the same speed if at the same orbiting altitude. Really the only way the mass of the objects matter is fuel and force. It takes way more fuel and force to get the 50 ton object to the same altitude as the 10 ton object due to the larger mass.
yes and no. If you replaced the moon with mars, it wouldn't keep orbiting the earth just like the moon does, since the two would orbit around each other. If you look at the math, you will find that the trajectory depends on the sum of the masses of the two objects. As it turns out, mass of the earth plus 10 tons is so close to mass of the earth plus 50 tons that those 40tons of difference are negligible. Thats also why a feather and a rock fall at the same speed in a vacuum.
Yes. See Galileo. Did you ever wonder why every low orbit satellite takes about the same 90 minutes to go around? All of them, from Sputnik 1 to some of the monsters that the Air Force launches, as long as they are in a roughly circular orbit.
Here is a SpaceX question I'd love you to answer some time: How many (and which) pre-bock 5 boosters might I one day be able to go see in a museum? SpaceX have landed lots of pre-block 5 boosters, but they've adopted a policy that pre-5 can only be launched twice, and they then don't recover them after the second launch, so lots of potential museum pieces are falling into the ocean. However, there are some exceptions: the first booster they ever landed is on display at SpaceX HQ. The two side boosters of the Falcon Heavy launch were both pre-flown, and have been recovered, so can't fly again (unless SpaceX chane their mind). I think the first time they flew a pre-flown booster they recovered it, as the throw-away-on-second-flight policy was not then in place. Am I right on all of these? Are there any other boosters that have been recovered after a second flight? Have SpaceX ever indicated what might happen to these?
There was at least one Falcon 9 that was recovered on its second flight. It was from a NASA CRS mission. spaceflightnow.com/2017/12/20/photos-falcon-9-lifts-off-from-cape-canaveral-then-its-booster-returns-for-landing/
There are a number of block 2, 3 and 4 boosters that were used on high energy missions and recovered, some of these are still in approximately one piece and could end up in museums. There are also the three Falcon Heavy boosters - one of them was seen today, missing a few engines but otherwise intact.
The wikipedia page lists how many boosters have been retired after landing, somewhere around a dozen. en.wikipedia.org/wiki/List_of_Falcon_9_first-stage_boosters The first successful landed booster was retired and set up outside SpaceX's headquarters in California. The next landed booster was recovered, reflown and landed again, then donated to Canaveral where it's probably on display somewhere (they also have one of the falcon heavy boosters near the Atlantis.). After that theres 1 more retired , then both boosters which were reused for the falcon heavy flight. Then 4 more retired Falcon FT's. After that theres 3 recovered block 4's awaiting launch, and 1 in storage. As well as the first block 5 which no doubt is being taken apart as we speak. I didn't count any boosters which have been lost or expended however.
wow!!! I always thought I know a ton about orbital mechanics because I seem to know more than anyone that i've met. But this video showed me sooooooo much more than I didn't know! it's hard to wrap your head around but I can definitely somewhat understand how it works.
Gotta keep those instruments on nadir. Never even realized this until now - has stared at more aerial imagery that most people. That's so cool. Thanks.
Lol, people thought that to drop from an orbit you need to move downwards? I learned that that's false, like, in my first attempt to go home in ksp... Oops Legends say the souls of forgotten kerbals still flow on orbit
Those souls sometimes manifest in debris floating the orbit of kerbin and use those debris as incubators to form a new kerbonaut thus, rescue missions.
NoName you shouldnt forget that people have different levels of exposure to these things. i know it doesnt work that way too, but that is becouse i was interested in the topic, we didnt really cover this is school or something. there are probably areas where we two think really wrong stuff too.
Sounds like those kerbals would have encountered a fiery death if you indeed decided going home would require accelerating downwards. Assuming you used a lot of fuel to deorbit yourself by accelerating downward.
You could, except for the fact that it's only 200 miles up orbiting a rock that's 8000 miles across every 90 minutes. When the ISS goes behind the Earth, it's in night, whatever the crew might wish. And when it's in front of the Earth, it's illuminated by the sun on one side and the Earth on the other. That 90-minute cycle is going to dominate everything else. Not to mention that spinning the ISS is going to make getting the solar panels, radiators and antennae all pointing in the right direction a little more difficult.
it'd be much easier to turn the lights on and off, and open and close a set of blinds on a 24 hour cycle than it would to even attempt to spin the entire station in hope of achieving this effect.
Walker, yeah I forgot about this. Is there a term for how a polar orbit meshes with day/night cycles? Because I know they aren't all the same. I've done polar launches that have resulted in a satellite being perpetually in the sun (for a while anyway, I guess this effect changes similarly to moon cycles?), great for scansat missions, but equally I've done missions where the satellite wasn't in the sun long enough and scanning took MUCH longer than it should have.
I first started to understand orbital mechanics as a child when I read Larry Niven's novel "The Integral Trees." The saying taught to all children born in the gas torus, "East takes you out, out takes you west, west takes you in, in takes you east, port and starboard bring you back."
"This was just a joke in poor taste." - Only depends on the beer. Better beer, better taste. No Bud, no Coors, no Becks, no Fosters, no Corona, no Heineken, and it can only get better from here.
nah, if you calculate every force on a spinning object or an object in orbit it all makes sense. Intuitive it makes almost no sense, as example: you prob know the vid where someone can barely lift a fly-wheel but when he spins it he can lift it with no troubles above his head.
It really helps to remember they are thousands of years ahead of us in terms of technology, might as well have found a way to redirect a spacecraft without using thrust
Sebastião Mendonça I like to imagine, in most sci-fi settings with spacecraft, that they have a way to “anchor” a point in space, thus letting the rest of the craft swing around that point like a hinge. This doesn’t really make much sense with our current science, but it’s an explanation at least
One cannot truly appreciate just how much of a valuable teaching resource (when it comes to orbital mechanics) that Kerbal Space Program is until you actually play it. It is amazing
