The MASSIVE difference between orbit and sub-orbit

Today we’re going to dive into the differences between space and orbit, dive into orbital velocity and the Karman line, some rundowns on orbital mechanics and things like apogee and perigee, how, when and why exactly astronauts experience zero g.
Here's an article version of this video - everydayastronaut.com/space-v...
00:00 - Intro
02:05 - Space vs Orbit
02:55 - Zero G and Weightlessness
05:15 - Is there gravity in space?
07:28 - Where does space begin?
08:45 - Kármán line
11:05 - Apogee and Perigee
13:55 - Orbit vs Sub-Orbit
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19:15 - Summary and final thoughts

[@samsonsoturian6013]

Speaking of sub-orbital: The SR-71 was once passing through Los Angeles airspace and asked for clearance to fly over at 70,000 feet. The air controller didn't know who they were and irritatedly asked how exactly do they plan to get up that high. The pilot said: "Sir, we were hoping to DECEND to 70,000 feet."

[@quantum_martian]

Wow how did the atc respond next

[@pixselious]

@@quantum_martianUnderstandable, descend and maintain FL700, have a nice day.

[@maazasad]

What a flex

[@Crutch_Media]

That reminds me of the speed check story

[@ColinJonesPonder]

I heard the same story from a UK perspective when I was with the CAA, "SR-71 requesting FL700". "ATC: if you get get there you can have it!". "SR-71: Descending to FL700."

[@sebringb]

“There is an art, it says, or rather, a knack to flying. The knack lies in learning how to throw yourself at the ground and miss. Clearly, it is this second part, the missing, which presents the difficulties.” ― Douglas Adams, Life, the Universe and Everything

[@B4ckup]

I was thinking about this quote the whole video, LOL.

[@freerangemtb]

I understand the basics of orbital mechanics, but it's always fun to have them explained again. I really appreciate your work, Tim, and encourage you to keep it up. Thanks for making this and your other videos.

[@nirbhayatiwari5425]

Are you a rocket engineer/scientist ??

[@heretichazel]

​@@nirbhayatiwari5425probably a ksp player XD

[@FrikyMediaLP]

You were not kidding with the amount of animations in this video O.O they look sooo good!

[@WhiskyCanuck]

I probably would not have chosen a Russian MiG-29 as the plane in aircraft animation sequence, given what's going on, but yes, the animation game is strong here.

[@TaurusSpace]

@@WhiskyCanuckMiG-29 is a Soviet aircraft

[@WhiskyCanuck]

@@TaurusSpace And continued to be produced by Russia post Soviet dissolution, so it's Russian now.

[@brettjones5336]

Best explanation of an orbit I've ever seen the ball throwing example makes it so clear!

[@paulcordingley3434]

Agreed. This has been the clearest explanation I’ve also seen.

[@xixixao]

That explanation and graphic are wrong. Imagine if you just let go of a ball at the top of a shaft that goes through a planet. The ball is not gonna stop at or near the planet’s center. It should oscillate between the two ends of the shaft. That’s basic kinematics (high school physics).

[@snuffeldjuret]

@@xixixao but dropping it and throwing it is not the same thing, so why would you expect the same result?

[@TheBrendonian]

@@snuffeldjurethe’s right. The orbit goes straight past the centre of the earth, and passes straight out the other side. Tim’s orbit assumes the Earth’s mass is a single point at the centre, which is a fair approximation when calculating orbits above ground. In reality, gravity tends towards zero as you approach the centre of the planet because anything here is equally attracted in all directions by the mass of the surrounding planet.

[@snuffeldjuret]

@@TheBrendonian I mean, he is right except for the part where he is wrong. Sure :P.

[@whitslack]

Tim really needs to learn the difference between inertia and momentum. I've heard him make that same mistake in live streams as well. Inertia is an object's resistance to acceleration due to a force. Thus, inertia is effectively synonymous with mass. Momentum is the product of mass and velocity. An object of a constant mass will have a constant inertia, regardless of its velocity. A highly massive object at zero velocity will still have a lot of inertia. Inertia is why, even in a zero-G environment, an astronaut pushing on a massive, free-floating object will still feel that object pushing back on their hand, even though it has no weight. Momentum, not inertia, is what carries an object on a ballistic trajectory, as momentum incorporates velocity.

[@thecodewarrior7925]

I feel like it’s ambiguous though and both work in many situations. Momentum is *how much* it’s going, and inertia is why it *keeps* going. “It keeps going up because of its momentum” and “its inertia keeps it going up” are both correct, they just come at the problem from different perspectives.

[@whitslack]

@@thecodewarrior7925: Right, but a rocket actually has _less_ inertia when it's flying through the air than it had when it's sitting on the launch pad.

[@milutzuk]

@@whitslack "Right, but a rocket actually has less inertia when it's flying through the air than it had when it's sitting on the launch pad." I think you're contradicting yourself: "Thus, inertia is effectively synonymous with mass.", with the second affirmation being true. Inertia is a different category (as it is defined in philosoply) than mass or momentum. Inertia is an observable property/phenomenon, mass and momentum are measurable properties. You have kg as unit for mass, kg*m/s as unit for momentum, what is the unit for inertia? Anyway, I totally agree with you that Tim needs to learn the difference between inertia and momentum. Being here, I don't understand why he thinks that firing the engine at one point of a circular orbit will elongate the orbit at the opposite point is counter-intuitive. If one thinks of an orbit as a budget of energies, an orbit is a sum of potential and kinetic energy. Heck, even a relativistic orbit can be seen this way. If you fire the engine at one point of a circular orbit, tangent to the orbit, at that point the kinetic energy will increase/decrease, obviously, but the potential energy would stay the same; the altitude will not magically increase/decrease. Because the sum of the kinetic and potential energies should stay the same at any point of the orbit, that kinetic energy will be transformed into / deduced from potential energy and what is the point would that happen? The point that is situated the furthest from the point the engine fired. That point would become, for an orbit around Earth, an apogee/perigee.

[@Mushielabs]

I feel like that is a great explanation of the difference...nice thank you

[@xtnuser5338]

@@milutzuk Doesn't seem to be a contradiction to me. The mass of a rocket rapidly declines as it accelerates upwards. The mass is left behind as the products of fuel burn, and fuel can be a significant percentage of a rocket's total mass prior to launch.

[@notmyname327]

I'm glad you highlighted Shatner's response to his flight, I was really touched when I saw his reaction and heard him describe the experience. It made me appreciate suborbital flights much more.

[@ardag1439]

"We didn't tell the recovery crew you would be staying, so they are still looking. Good job!" +20,000 Funds +10 Science +5 Reputation

[@Guardrailkid]

{insert Jebediah dance}

[@BnORailFan]

I finally understand how and why there are two burns to get into orbit. I didn't know about how the first burn creates an elliptical orbit and the second burn at apogee creates a circular orbit. Thanks for a great video.

[@_mikolaj_]

Actually there is one usually. Its matter of tuning your trajectory, but you dont see any sort of coast phases during initial orbital launches. Second burns usually are to get out of the parking orbit.

[@Noughmad]

You usually do two separate burns when playing Kerbal Space Program for the first time. But that is inefficient, it's better to combine them into a single continuous burn, as real rockets do. They start burning upwards, and then gradually pitch over from 0 to 90 degrees, accelerating upwards and sideways at the same time.

[@williamtsmith9668]

​@@NoughmadToo, rocket engines have 2 major types, one works good in the atmosphere, and one is more efficient in a vacuum. That, only becomes import ANT, with very large mass, like the Superheavy and Starship's future iterations. 👻☠️🗽💯🙏

[@computernerdtechman]

This was probably one of the best explanations I have ever heard about orbit and sub-orbit and how to achieve orbit. Thank you very much.

[@johnburr9463]

Evergreen as always. Keep doing what you're doing! You are on a good trajectory.

[@mouser58907]

Tim: Hey Casper, I need you to animate a person in a SpaceX pressure suit in a New Shephard capsule, shooting a sniper rifle out the window. Casper: Tim: Casper: Wait, seriously?

[@StanleyCreative]

These were some of the funniest animations to create, I was constantly like "what am I doing how is this my job, this is incredible" 😆

[@glennsvanberg9023]

Great work. This is by far the best explanation of orbit I have ever heard

[@EmyrDerfel]

That old Douglas Adams line: throw yourself at the ground and miss. Also Shatner's experience reminds me of the Total Perspective Vortex.

[@tylerw13]

Your videos are so informative and easy to understand for us layman types. Thanks so much for all your work and videos!

[@corwinchristensen260]

Dr. Don Lind explained to me (as part of a class) once the need for the term "microgravity." In large structures (like the ISS), you can get far enough away from the structure's center of gravity that there is a constant stable microgravity. While tiny, it is enough to affect sensitive experiments. Also, he said that in every spacecraft, if you misplace something and it's free to move, there's a location where air currents (filters) and microgravity (extreme front, back, nadir, & zenith) will push it to. Just give it time and what you're looking for will make its way there.

[@tonywells6990]

The ISS is also rotating slowly as it circles the Earth, so things inside tend to float up towards the ceiling (or the floor depending on where you are inside) too.

[@phil4826]

You will only feel this centrifugal force if you're tied to the rotating structure, which an experiment will be (and everything floating inside as it moves away from the center of rotation. But even in freefall, there is still a tiny tiny force you could theoretically measure: gravity gradient. Near Earth, its almost undetectable for normal sized objects like people. Get close enough to a black hole and it would stretch you into a human spaghetti.

[@m16ty]

Anything with mass has gravity. Theoretically a person doing a spacewalk could get into a orbit around the ISS. As far as forces moving stuff around inside the ISS though, air currents have a bigger control than anything. There is a pretty big turnover of air constantly in the ISS to scrub the air of CO2 and to maintain climate control. Without a lot of air movement inside a spacecraft, it is also a possibility that astronauts staying in one position for a long time (such as sleeping) that you could suffocate on your own CO2 that would accumulate around your head.

[@uritamminga1]

I still like Tim‘s complaint about the term “microgravity.” Gravity refers to the field generated by a mass, eg from earth. However, there is nothing micro about the field at the distance of the ISS. But if you’re referring to forces generated by orbits (of the ISS itself) and air currents (within the ISS)…well that’s just not gravity. The term “microgravity” is misleading…it causes the general public to think they’re referring to the little bit of earth’s gravity left from earth since the ISS is floating around in space so far from earth. Totally unhelpful

[@krshna77]

@@m16tyi doubt it. CO2 should diffuse into the whole room quite fast enough (especially as it's being exhaled with a higher temperature than the rest of the air). Also the breathing itself is enough to generate a very slow current around the room, enough to mix the entire volume of gases.

[@anthonyblacker8471]

You really have come a long way in just a couple (few?) years Tim. I am astonished how much you've learned (and shown us) in this time, even with the help of all your supporters, it's just astonishing to me to see how fast the world has changed with the internet. Thank you so so much for taking your life and sharing what you've done with it with the world! You truly are one of a kind!

[@johnkmiec9207]

Tim, spectacular work as always. You and your team truely have a gift at making ultra complex space related content understandable to us mortals. Keep up the fantastic work. I've watched every one of your videos and can't wait to see what you planned next. God speed good sir!

[@drkslayer00]

As an engineering major, who is new to learning about space travel and flight, the Apogee and Perigee explanation straight up gave me chills. How the first people who discovered this just blows my mind

[@o.m.b.demolitionenterprise5398]

play kerbal

[@JWQweqOPDH]

Many are aware that falling object follow a "parabola", but just imagine if something fell from much higher going much faster sideways. To continue the parabola would mean accelerating indefinitely away from the Earth (after you missed it), so it becomes apparent it's not actually a parabola. Astronomers have tracked and predicted the movement of celestial objects with both nearly circular orbits as well as very elliptical orbits (comets). So, it's arguably obvious given enough thought that going fast enough sideways and maintaining that speed will achieve orbit. It's just a matter of figuring out how that can possibly be done. It was a difficult enough task that it only happened with funding for delivering nuclear weapons.

[@matty7834]

Probably theorised for a very long time, it's just circular motion

[@odysseusrex5908]

yeah, that would be Johannes Kepler.

[@Th3_Gael]

Play swing ball. This was intuitive to kids decades ago

[@ShawnWebster19]

This was utterly amazing and I can see myself watching it over and over

[@rob.dowson]

Great video Tim. The ball/gun illustration is the best explanation of orbit I've seen - brilliant! Makes total sense now!

[@Trolligi]

As an orbit I can confirm this is true

[@clayel1]

oh shush

[@Andrew-Kerr]

As an Azimuth, oh shush

[@nimrodquimbus912]

So then gravity must come from the acceleration of the expansion of the Universe......KJV Bible is right again.

[@jotto64]

👍 Extremely good explanations of topics that many people don't know so much about 👍 You are literally bringing space down to everyday people!

[@TheOnlyFeldy]

Great video Tim! Very helpful in understanding orbits.

[@PsychoMuffinSDM]

I have watched A TON of these kinds of videos, and the apogee/apoapsis was a good chuckle (being a KAP guy layer myself), but the apalune and perilune was a new thing I learned, so thank you so much for including that!

[@offdagrid877]

Like the fact you put a spaceX space suit in the blue Sheppard. Experienced brief weightlessness when in the bough of a tall ship in a force 8 gail.

[@luckosteve12]

Excellent as always. Great animations and thorough explanations. Thank you Tim.

[@hirvielain9013]

Excellent video, Tim! Very clear, superb animations and not too long.

[@14rs2]

16:54 “As you can guess, getting something big to orbit out of a big gun is really hard” Engineers on project Babylon: “He’s right you know”

[@rocketman1969]

Great video as always Tim! We appreciate your work.

[@Bwizzie_Reborn]

I wish to say two things: 1). The team you have assembled has resulted in your most polished video. You can easily use this video’s production value and re-establish educational passion into the underfunded science specialties. I remember watching Wild American, Carmen Santiago, The amazing Sesame Street and Mr. Roger’s, and more. I also envision embracing this new modern young world of social video games and foresee Kerbel being a “Oregon Trail” like phenomenon once a week in elementary school again…. 2) I admire your spiritual, passion for education, self-taught intellect and most importantly….you seem to have finally balanced your health and workaholic nature to make your channel a movement for all to admire and embrace with proud vigilance. Well done Tim and @everydayaustronaunt team! Have a blessed day y’hall!

[@scottre3220]

I got a feel for all of this in Kerbal. Went on a zero g flight because I knew (for a much cheaper price) I would get 7 minutes of zero g (20-30 seconds at a time) as well as experiencing Mars and Lunar gravity in suborbital flights.

[@saadusmani78]

That's so cool. What was the experience like? How much did it cost? Do you have to wait long between booking and the flight? Sorry if this seems like too many questions.

[@wertawonka]

The way to expand and contract with apogee and perigee is very interesting. I now would like to know more about velocity generating heat when there is less atmosphere above the kepler line. That bit was a little too fast for me to take in

[@charleslivingston2256]

The air produces drag forces for an object moving through it. If the drag forces are high enough, they actually produce high heat as the air molecules are being compressed on the leading side. The drag force is proportional to density and to the square of the speed. Therefore, if the density were a million times less, the velocity would have to be a 1000 times faster to have the same heating effect. Given the orbital speed at the Karman line (7.85 km/s, 28.3K km/hr, 17.6K mph) and the fact that the density is a factor of about 4 million less than at sea level, the heating effect would be the same as an object at sea level moving fairly slowly (14.5 km/hr, 8.8 mph). The air density falls roughly exponentially with altitude. That would be precise if gravity stayed constant (it is about 3% less at 100 km) and temperature stayed constant (it decreases for a while and then starts increasing, then decreases again and then increases steadily). The International Space Station is about four times the altitude of the Karman line and so atmospheric density is a lot less there. It decreases by about another factor of a million from the Karman line. Even so, the drag on the ISS causes it to lose about 100 meters per day (more when intense solar activity heats up the outer atmosphere and it expands). They have to periodically boost the ISS to keep it at its altitude. BTW, those same drag forces are related to the aerodynamic forces on the control surfaces of an airplane. As the atmosphere gets thinner, it is harder to change the plane's attitude by deflecting a control surface. With lower density, the force on the control surface is lower, but the plane's inertia to be overcome is still the same. Kármán computed the altitude where inertial forces (orbital dynamics) exceed the aerodynamic forces.

[@Ender240sxS13]

If you're talking about the bit with the X-2 and the velocity needed to maintain lift vs the velocity at which heating is an issue, it has to do with the kinetic energy involved. There is a simplified but technically incorrect way to think about this and the more correct but more complicated answer. So simple answer first, way less atmosphere hence needing to fly faster in order to generate lift, as your speed relative to the air increases each collision with an air molecule carries way more kinetic energy, which ends up generating heat, basically friction heating with the air, at these speeds the heat from each air molecule colliding with the plane is enormous and there are fewer of them to carry the heat away so the plane heats up. Now the more correct but more complicated answer. So the speeds needed to achieve lift here are way above the speed of sound at that altitude. This means that what little air IS there ends up generating a shockwave at the leading edges of the vehicle. A shockwave is generated anytime a supersonic flow has to either slow down or change flow direction. Shockwaves are regions where there is a sudden discontinuous increase in pressure which is proportional to the flow Mach number. Because of the physical properties of gasses their pressure, temperature and density are all related, when one changes so do the others. Therefore there is also an increase in the air temperature that is also proportional to the Mach number. The temps in the shock front are high enough that the thermal radiation emitted by the air molecules in the shock begins to heat the vehicle faster than the air around the vehicle can carry that heat away. For vehicles moving over Mach 2 this shock heating exceeds the skin friction heating (the simple explanation) by a couple orders of magnitude. For very high Mach numbers (varies but for this conversation we are talking like 4+) the temperature spike in the shock can be so extreme that the air decomposes into a plasma. If you would like some sources to learn more about this I can give you the names and authors of the textbooks I used when getting my aerospace engineering degree, there are older versions of them that can be found for no cost if you know where to look.

[@wertawonka]

@@Ender240sxS13 man that is super interesting

[@williamtsmith9668]

​@@Ender240sxS13Post the sources. I will sic my Chat GPT on them. 😊

[@Ender240sxS13]

@@williamtsmith9668 Modern Compressible Flow by John D. Anderson this first one is probably the best for understanding shockwaves, their formation and effects on gas properties. These touch more on the ramifications of effects and what needs to be considered to deal with them. Aircraft Structures for Engineering Students by T.H.G. Megson Spacecraft Structures by J.J. Wijker

[@jeremymatthews1667]

Great job Tim! Amazing explanation and awesome graphics to help understanding.

[@rezagholghasri8869]

You have noooooo idea how much I enjoyed watching this. One of the best videos I’ve ever watched. You really explain the hardest matters in the simplest way in your videos and this, was the best of them. Thanks Tim. 👍👍🙏🙏🙏❤️❤️❤️

[@mkleuskens]

Great video! One detail: a bullet would only fly around the center of the earth if you assume the mass of the earth packed around the center. In reality, the g force would decrease to zero when approaching the center of the earth, causing the bullet to fly straight through the earth, reaching the point in space exactly opposite to the capsule. But since this explanation complicates thing too much, it is enough to say that you assume a point mass

[@ericfielding2540]

That would be theoretically true if there were some tunnel through the Earth but the extreme pressures inside the Earth make such a tunnel impossible.

[@krshna77]

@@ericfielding2540 An orbit is defined by an object's initial velocity and direction of motion. Whatever friction or collision happens along the path is only an alteration of that orbit. The thing is, an entire section of this video is just wrong (from 14:40 to 17:00 ) because orbits never go "just around the center" when lateral movement is insufficient.

[@krshna77]

A bullet would never fly (just) around the center, no matter how you pack the earth into a point. It will always have an orbit that ends at an equal distance from the center, on the opposite side. Even a simple fall with no lateral movement does the same (barring all friction and obstacles)

[@Yooshist]

Simply the best space channel on youtube.

[@PhotoArtBrussels]

Thanks for the video Tim! Always look forward to any new posting.

[@davidjhyatt]

I did a mission design for Europa in school and there wasn't a dedicated name for the apoapsis and periapsis so they became apopa and periopa. Apopa sounds like a nickname for a grandma and I love it.

[@AlexKnauth]

I think part of the confusion comes from people interpreting "Zero-G" as if it meant "Zero Gravity", but the "g" in "0g" is a unit of acceleration, not a shorthand for gravity as a force. Maybe a better term to clear up that confusion would replace that "g" with another word like "acceleration", not replace the "zero" with "micro" while leaning into the confusion of "g" with "gravity".

[@Ender240sxS13]

Even that has problems though, because you ARE experiencing an acceleration, gravity IS an acceleration. The inward acceleration of gravity is what is keeping you and everything around you in a circular orbit rather than continuing off in a straight line. You don't feel any acceleration because everything around you is experiencing the exact same amount of acceleration, your acceleration relative to your surroundings is zero. Personally I think the best term to use is free-fall as it fairly accurately describes the mechanics of the situation. Language is tricky and sucks at accurately and succinctly describing complex phenomenon in just single phrases.

[@krshna77]

@@Ender240sxS13 gravity is NOT acceleration. Acceleration is a force, gravity is not (despite being described as one in classical mechanics). In reality gravity is the bending of spacetime towards objects with mass, and free fall (aka no acceleration in any direction) is simply the manifestation of inertial rest in spacetime coordinates. Gravity only APPEARS as acceleration from the perspective of the planet's center of mass (therefore its surface) Language is indeed tricky especially when teachers themselves don't explain or even understand the tricks well enough

[@Ender240sxS13]

@@krshna77 mate you got things backwards there. Acceleration is NOT a force. Forces result in acceleration. The common misunderstanding is that gravity is a force, which is incorrect, as then the acceleration objects experienced due to gravity would vary depending on their mass. Yes the acceleration is due to spacetime curvature, however this doesn't change the fact that the effect of gravity is a constant acceleration. And free fall is not "no acceleration in any direction" free fall is literally when there is no force acting to oppose the acceleration. Being in free fall is not inertial rest in spacetime coordinates, rather it is an object moving in a straight line through curved space time.

[@keffordt]

I’ve a degree in aerospace engineering and this is such an informative video. Wish I’d had this type of resource at the time. Great work Tim and team 💪🏻👏🏻

[@mrnnhnz]

Hi Tim, well said. I think there was one thing you forgot to extrapolate: you mentioned that you don't keep falling when you're on Earth because Earth stops you - hence you DO feel the 1G. It would be helpful, I think, to carry that observation on for a point in space at the top of the Karman line. Perhaps like this: Imagine you're at the Karman line, but you're NOT following a free-fall trajectory - perhaps you're on a balloon up there. The balloon's not going up or down or side to side. It's holding itself in place with it's lighter-than-air contents, and positioning thrusters. You're walking around - in a spacesuit - on the top of that balloon (let's imagine it has a flat top.) Do you feel gravity? Yes. Almost 1G, because a) you're not that far from Earth, and b) the fixed height of the balloon you're on is, like Earth, keeps you from falling. (Incidentally, this is what makes - to my mind - Venus a better pick for colonization than Mars. We could live at the top of the Venusian atmosphere where we're high enough to be out of the heat, acid rain and extreme pressure, but low enough that there's still some atmosphere above us to burn up incoming meteorites. And that's important, because we'd be living on big inflatable balloons that keep us floating in place. Gravity is almost Earth gravity there (much better than anywhere else in the solar system, other than Earth,) it's a shorter trip to get to Venus than to Mars (and shorter comm.s distance,) solar power is a lot more effective as we're a lot closer to the sun. And other benefits. Psychologically not as nice as living on the ground, but I reckon the engineering challenges aren't any harder than making Mars work, and the benefits of Venus outweigh the benefits of Mars.)

[@byronfester7941]

Finally the video explanation I’ve been waiting for, amazing job!

[@ColinJonesPonder]

Remember, according to General Relativity the reason we feel gravity is because the ground is accelerating us upwards at 9.81m/s². Freefall is non-accelerating. It sounds counter intuitive until you realise that we're being pushed against the flow of the geodesic you'd be naturally following through spacetime.

[@whitslack]

Correct. To expound on this: if you're following a geodesic (i.e., ballistic) trajectory, your velocity relative to some external center of gravity will be changing over time, but relativity says you're experiencing zero acceleration. According to general relativity, acceleration isn't a change in velocity over time but rather a deviation in an object's path from the geodesic. If you're standing "still" on the surface of the earth, you are most certainly not following a geodesic path, and thus you are accelerating in the relativistic sense. If you are falling straight "down" in a vacuum, you are *not* accelerating, even though your velocity is increasing, because you *are* following a geodesic path through spacetime.

[@whitslack]

This is why it always grates on me whenever commentators say things like, "It may look like Dragon and the ISS are barely moving, but we have to be very careful in our maneuvers because we're actually traveling at 17,500 mph." I facepalm because the vehicles' velocities relative to the center of gravity of the earth are irrelevant up there for purposes of avoiding collisions. What makes on-orbit maneuvering so difficult and dangerous isn't the vehicles' velocities relative to the center of gravity of the earth; it's the curvature of spacetime caused by the earth's gravity, combined with the fact that any tiny acceleration imparted by a thruster will actually be significant since the vehicles are otherwise under zero acceleration. The same acceleration by a vehicle sitting on the ground would be relatively insignificant since the vehicle is experiencing such great acceleration imparted "upward" on it by the ground. So, in other words, it's not the velocity that's so perilous up there; it's that the acceleration produced by the thrusters is actually very meaningful, relative to the zero acceleration that the vehicles are otherwise experiencing. Another way of saying this is that the curved spacetime due to the Earth's gravity well has much more noticeable repercussions on objects in free-fall than it has on objects under significant acceleration, such as everything intuitively familiar to us on the ground. That's why orbital maneuvering is so counterintuitive to us.

[@PlushGrenade]

Your videos create the overview effect with what feels like no perigee for the imagination, Tim:) thanks.

[@charleslord2433]

Off-topic, but that mug has to be the coolest merch you've come up with!

[@davidlabedz2046]

Tim, this explanation us great! Thanks for making the complex easier to understand!

[@richardzeitz54]

Micro-gee is an excellent suggestion! When the term microgravity was adopted, it was a major case of quibbling. But if you're going to quibble, you should quibble accurately! Zero-gee is good too. People are too careless with language - knowledge is power and we know things using language.

[@GreenBlueWalkthrough]

I mean I would go with Micro-Acerlation as that is what your really doing.

[@petersolymosi8977]

The question isn't about micro-this or micro-that. The question is: Is it micro or zero? And yes, it's zero - if our body is zero dimensional. Fortunately we are three dimensional, only the center of gravity of our body will experience zero gravity. Every part of our body, which is a little bit nearer to or further from earth, will experience a very small amount of gravity upwards or downwards. This is micro gravity. I'm with you, Tim, I hate this term, it's terrible misleading, but it's correct.

[@uritamminga1]

@@petersolymosi8977if a word is so “technically” correct that it is misleading and doesn’t communicate, then it is worthless and shouldn’t be used. Language is about communication. If a word doesn’t communicate correct meaning, why use it?

[@gregorychaney7604]

Another beautiful Everyday Astronaut video! It was so clear and relatable. Excellent. PS it would be really awesome if you could do another collaboration with Ellie in Space. You two have a similar positive outlook that works well together. Cheers from Alaska

[@michaellloyd2489]

Awesome content Tim. Keep on educating us.

[@kenmactiernan4290]

Another great video Tim and Team! Keep up the great work.

[@michagrill9432]

And for KSP players its completely obvious. Its amazing how through a _game_ orbital mechanics become natural.

[@GreenBlueWalkthrough]

I mean it's a sim not the most complex or realistic but still.

[@realulli]

@@GreenBlueWalkthrough Actually, the orbital mechanics are pretty much spot on. The atmosphere and gravity numbers for Kerbin are nowhere near how Earth behaves (especially the atmosphere doesn't peter off, at some point it disappears entirely). However, there's a mod that will change the constants to values that make it behave more earth-like (except for the Atmosphere effect). I don't know KSP2, so I can't say if they fixed that behavior there.

[@parnikkapore]

two-body OM at least, although there's yet _another_ mod if you want n-body fun

[@realulli]

@@parnikkapore I guess they took a few shortcuts there, too. IMHO the decision is OK most of the time, unless you want to do *really* wild swingbys...

[@donjones4719]

No worries, Alan Shepard & Gus Grissom's astronaut wings are in no danger anyways, they *orbited* in Apollo & Gemini. Shepard even walked on the Moon.

[@cyclesingsleep]

Tim, you and your crew knocked it out of the park...out of orbit!!! Fantastic video!!!

[@DerkMiester]

That was a great explanation of orbital mechanics! I understood everything you were sharing, and think more people can appreciate this!

[@AstronautMiller]

Keep up the great work! You have helped me learn so much about space!

[@mikal4452]

Very good video! Easy to understand and follow, and well produced. I would have enjoyed seeing a better comparison of the difference in energies required to achieve sub-orbital versus orbital flight, to illustrate the extreme challenges involved for each. Thank you!

[@Ender240sxS13]

Using energies to explain orbits is a bit more complicated and can be misleading because the energy required is dependent on the mass involved. More energy is needed to get 10kgs into orbit than is needed to get 1kg. Additionally when you begin to factor in the mass needed to generate that energy, how efficiently your system can convert the mass into energy etc. it just gets very complicated very quickly. There is a reason that at universities basic orbital mechanics is often a 200 level course and getting into actual energy calculations and rocketry is typically a 300 or 400 level course. You can use specific energy but again, it gets complicated and is much less intuitive than starting with the basics of just velocity requirements.

[@mikal4452]

@@Ender240sxS13; that's completely understandable, but some simplistic examples would be nice. The speeds required are a good start, but I don't think it fully illustrates the vast difficulty in accomplishing full orbit.

[@mikal4452]

I can also understand if this was left out to avoid disparaging the accomplishment of suborbital flights.

[@williamtsmith9668]

​@@Ender240sxS13Thank you for your kind explanNation.😊

[@GwahirW]

This is one of those things that goes to the back of your mind once you're familiar with the topic. It can be easy to forget how weird it can feel from personal experience. Well done!

[@juliusreischauer345]

Incredible video! Thanks Tim! And thanks to your team!

[@donjones4719]

I was really hoping Tim would cover how hot or how little heat the New Shepard capsule experiences during its straight-down reentry. Nowhere near what an orbiting capsule does, I know, but how tiny is it? Does it rely on a thin aluminum bottom alone? Related: In an abort does the whole bottom blow off so the abort motor can fire?

[@ATH_Berkshire]

No it will need some form of thermal protection. Nothing like what’s needed for orbital flight but not just thin aluminium skin.

[@donjones4719]

@@ATH_Berkshire That's what I figure. My best guess is a piece of steel thick enough to absorb the heat. That also makes sense with the base of the capsule functioning as the "landing gear" since it directly impacts the ground. Even after the little retrorockets fire that's still a thump.

[@SatoshiKitagawa]

Great work as always! I've learned so much thanks to you. Have you ever thought about making a video about nuclear roket propulsion?

[@slug..]

I'm liking these VS. Episodes 😊

[@NaeroSpace]

Evening knowing most of this info as a huge space nerd, this video made me really happy :) Thank you Tim. We love you.

[@xavermaier9625]

Orbit is falling with style

[@lbogaardt]

Could Blue Origin use their escape (solid) rocket right after seperation to gain extra speed and time in space? It's no longer needed once seperated, after all. How much could be gained?

[@theOrionsarms]

Actually is needed, because is not replaced with each flight, so buying another one every time would increase the cost. And about the speed not much gain, would be maybe 180 m/s deltaV for three seconds at 6 g.

[@simongeard4824]

Not much. The purpose of the escape system is simply to get the capsule far enough away from the booster that it can deploy a parachute safely. As such, it has a lot of thrust, but doesn't burn for long enough to make a real difference to velocity (on orbital scale, that is).

[@inwen8258]

Thanks Tim for your continued effort to - well, bring space to everyday people! Sitting here at 10am on a Saturday, sipping coffee and learning things that are in no way related to my work or my life in general. Yet you present it in a way that makes me feel that I have to know it! Cheers!

[@andrebecker7350]

holy cow. this is one of the best space-explaining videos ever! Tim & Team, what an incredible work. Thank you!

[@gfranpe]

Excelente explicación sobre estos conceptos básicos de mecánica orbital. Muchas gracias. Todo muy interesante.

[@tobiasweiher7786]

Hey Tim, great video!! Could you do a follow-up talking about the mechanics that took the James Webb Telescope to its destination? Getting an explanation from you about the Lagrange would be very nice! :)

[@peter_a.6651]

Fantastic video - really liked the explanation of how to change orbit altitude - graphic really made it clear - well done to you and your team!

[@MrHichammohsen1]

Was waiting for this do drop! Much needed video since so many people are interested in space now!

[@CookiePepper]

15:08- only if all earth mass is at the center of the earth. The ball will go the opposite side of the earth at the same height in this case.

[@stellans.2146]

With your talent and knowledge of space and rockets and the logical way of explaining things you should be supported by Nasa to do even more stuff like this. It has a huge value to them to educate people like you do for upcoming generations to be excited about space. Sadly, the ones with smaller wallets help you to make this. I wish you the best! All your videos are amazing!

[@z2kk]

Thanks for teaching me things I didn't know I didn't know. Good stuff!

[@BrianStDenis-pj1tq]

This was a great video. It explained many concepts in a clear and dense way. Great videos as well, thanks.

[@georgehill8285]

I heard Shatner speak about his experience at a Wrath of Khan screening a few months ago. Given the themes of life and death in that movie, hearing him talk about how life is clinging to this tiny speck in vast emptiness, and how death is coming, the climate is changing, it was very powerful, even secondhand just hearing him talk about it.

[@RidiculousRocketry]

I never realized what a trail blazer Jeff Bezos was until I watched him fly his phallus rocket for 10 minutes to the height of a weather balloon while wearing a goofy cowboy hat.

[@gusphoto]

That was awesome, Tim! The description of apogee/perigee, creating the elliptical orbit, then raising to a circular, and vice versa, was the first time I've learned that! Really awesome and thank you!!! Navigating with gravity! Fascinating!!! ..and so critical for us all to learn as we slowly evolve into the interplanetary species. Perhaps as more of us understand further, the more we will manifest this destiny. Beautiful!!!

[@johndoepker7126]

All we need now is Capt. Sisko on a Dragon ! That....would be....AWESOME!!!! But in all seriousness....learning the distinctions of wat 0g, micro-gravity, zero gravity are was very cool !!! I kinda had an idea....but was also kinda wrong too....Thanks Tim, for learning me some science!!!! I can't wait for another installment of awesomeness 🤟

[@danwylie-sears1134]

The one thing that's potentially confusing in this video is the idea of a ball tossed out the hatch of a suborbital spacecraft doing a nearly-instantaneous U-turn near the center of the earth. The reason is that the orbit is plotted with Earth as a point mass. When the ball is very close to that point, all of Earth's mass is pulling on it from very close range, so the acceleration is extremely large. If it just had a tube descending deep into the planet along its trajectory, the acceleration would decrease as the force of gravity exerted by rock above acts in the opposite direction from that exerted by rock below. At the very center, the forces would exactly balance, so there would be no acceleration at all, i.e. no sharp turn.

[@grasshopper-ln9us]

Too bad Jeff bezzos actually made it back to eartj

[@ges7991]

Excellent! Your graphics are always amazing.

[@DeryckThompsonChasingtheDream]

Brilliant video thankyou you have answered so many of my questions on this subject, and your dictation and explanations are spot on. so good. I am so happy for you to be going up into space, your knowledge about space is phenomenal.

[@johnlynch5007]

Great Video as always Tim. Thanks for all you do.

[@darylmunton6262]

Brilliant video. I learn new stuff everytime and I love that. Thanks

[@How_Many_Monkeys]

Awesome video! So many little tidbits of information surrounding a very clear-cut easy to understand lesson in orbital mechanics 👌

[@lmd37]

A brilliantly informative video. Thanks so much for sharing.

[@gsdjparaeventossocialesdjg9679]

Great work Tim!! You solved lots of questions for everyone interested in this topic. Keep up with the good work Greets from Buenos Aires, Argentina.

[@vatyunga]

The animations and the overall design of this video are awesome!

[@OzScalemodeling]

Thanks for this informative video that answers a lot of questions. Cheers

[@Braskil]

Great summary! Explaining orbital speed with throwing a ball was very elegant!

[@WuffiePhoenix]

Your videos are phenomenal. Thank you!

[@pastorjerrykliner3162]

I'm having flashbacks to reading the "Hitchhiker's Guide to the Galaxy" (in "So Long, and Thanks for All the Fish") where Artur Dent learns the secret to flying is to "throw yourself at the ground, but miss."

[@bobmusil1458]

👍😂

[@MBdrummer3288]

You are one smart dude, Tim. You make some great and very informative videos and I love them. Keep it up man 👍🏻

[@rearview2360]

Amazing as always Tim.

[@JaviAirwraps]

Everyday astronaut knocks another one out of the park! =)

[@binderchannel9454]

Many thanks Tim, very informative video.

[@JohnSostrom]

Very good show. I love how you make suborbital vs orbital simple. In the Navy, Fire Control techs have to study this subject to some degree. After all, the velocity of a cannon round determines the arc that it follows to reach its target.

[@wolre]

I think this may have been the best and most intuitive explanation of orbital mechanics I've seen so far! Thanks!

[@maotseovich1347]

On those opening questions: I think the bigger question for people who don't understand this yet is more along the lines of "The one that's staying in space isn't firing its engine still?" "How does it stay up without using its engine again if the other one falls straight back down?"

[@GreenBlueWalkthrough]

An episode of Gravity and is it real? perhaps?

[@Ender240sxS13]

Did you understand the answer from the rest of the video or are you still unsure? Or are you just positing that these are the questions that people with a lack of understanding would be more likely to ask?