The MASSIVE difference between orbit and sub-orbit 

Wow how did the atc respond next

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

What a flex

That reminds me of the speed check story

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."

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

Are you a rocket engineer/scientist ??

​@@nirbhayatiwari5425probably a ksp player XD

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.

@@WhiskyCanuckMiG-29 is a Soviet aircraft

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

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

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).

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

@@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.

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

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.

@@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.

@@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.

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

@@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.

{insert Jebediah dance}

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.

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.

​@@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. 👻☠️🗽💯🙏

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" 😆

oh shush

As an Azimuth, oh shush

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

play kerbal

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.

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

yeah, that would be Johannes Kepler.

Play swing ball. This was intuitive to kids decades ago

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.

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.

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.

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

@@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.

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.

@@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.

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)

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.

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.

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.

@@Ender240sxS13 man that is super interesting

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

@@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

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

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.

@@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?

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.

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.

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.

@@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

@@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.

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

@@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.

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

@@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...

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.

@@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.

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

​@@Ender240sxS13Thank you for your kind explanNation.😊

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

@@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.

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.

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).

An episode of Gravity and is it real? perhaps?

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?

👍😂