Deep Space Questions: What Is Max-Q? Strange Lights In The Sky? Orbital Grammar?

[@georgemorris7947]

I venture to suggest that the phrase 'on orbit' is most usually used to declare that a spacecraft has achieved a specific orbit that is being aimed for - eg the spacecraft is now on orbit and can begin the planned acquisition of data - whilst the mire generic phrase 'in orbit' merely conveys that a craft is neither going to fall back nor escape.

[@Michaelonyoutub]

Yeah this seems to capture the nuance of the phrases to me, and explains why their usage differs for professionals and the general public. For the general public, getting into orbit is what matters and it is rare that getting into a specific orbit truly matters to them. For professional purposes, generally distinguishing that something is in a specific orbit, and things are done on that specific orbit, is often important as not every arbitrary orbit will do.

[@DrDeuteron]

It usually is used in the context of design or activity: 1) at 10 GHz sample rate, we’ll have to average on orbit (vs ground processing) 2) we won’t know the exact nature of the background until we measure it on orbit.

[@mariobernard5583]

My thought exactly! "On a specific orbit" / "on its assigned orbit" vs "in orbit somewhere".

[@T_Mo271]

Agree. I took "on orbit" to imply reaching a duty station, where operations will proceed. You could be "in orbit" but not ready for active use yet.

[@IanValentine147]

Scott thanks for answering my question. In the second part of the question (there on screen if u pause the video), I postulated that on orbit was in orbit and 'on line' - ie it implies (as other commentators have suggested) nominal operations in orbit. But I guess your answer is the most correct, it's just interchangeable depending on the audience? Thanks again and Fly Safe (get your IR)

[@keithrange4457]

12:32 "Im sorry, noone wants to mate with you" Cracked me the F up lololol lollers 😂

[@scottmanley]

The book on the desk is the "A City on Mars: Can we settle space, should we settle space, and have we really thought this through?" by Zach & Kelly Weinersmith - releasing next week: amzn.to/40mbf9J

[@QuantumHistorian]

Any chance you're going to write/record a short review of it?

[@floatthecreek]

I haven't watched you in a while, sorry for that, I've been busy. Just wanted to know how many hours you have logged flying. Also, have you started your IFR training? I'm an A&P IA Private Pilot. Just wondering. "Fly Safe."

[@azgarogly]

As we all know from the documentary named Gravity (2013), The Orbit is a dark flat place sized about 100 kilometers by 46 minutes.

[@bbgun061]

I've also seen the Starlink flares from the air, over North Texas, looking north around midnight. They were there every night, always in the same spot on the sky. They usually flash about once every 30 seconds. (It was early summer when I was last there, so I might be misremembering the timing. The flash was too slow to be anticollision lights, but too fast to be an aircraft in a holding pattern.) The fact they were there night after night led me to suspect that I was seeing each successive satellite in a single orbital group.

[@Kineth1]

welfuk I bought into wienersmith's religion series, so i outta buyinto this one.

[@stuartgray5877]

For the MER Rovers they entire payload needs to be very carefully "spin balanced". This was because the third stage of a delta II rocket is "spin stabilized". The second stage points in the direction you want the third stage to go, then it spins up the third stage (payload and solid rocket motor) to about 60 RPM on a bearing using little solid rocket motors. It then releases the third stage which ignites the SRB and the third stage goes shooting off into space using nothing but the "dumb" spin stabilization to keep it pointed. When the SRB burns out, the stage releases "Yo-Yos" that deploy like the arms of a spinning ice skater and the spin slows to near zero. The payload then separates, and both are on a trajectory (mostly) in the direction of Mars (in the case of the MER rovers). If the payload is out of balance (or mass shifts during ascent) it can cause the upper stage spin-up to spin in a way that sends the payload off in the wrong direction (or too little velocity) imagine an unbalanced washing machine being launched by a rocket.... I have launched 6 of my seven spacecraft on Delta IIs and five of those had spin stabilized third stages for deep space trajectories: Mars Global Surveyor, Stardust, Genesis, Deep Impact, and Kepler Space Telescope. NOAA-20 also launched on a Delta II (2nd to last one) but did not require a third stage as it is an earth orbiter.

[@stuartgray5877]

When we did the "Spin balance" on Stardust they considered the stowed solar arrays to be too big of a disturbance to properly measure the spin balance with the vehicle spinning at 60 RPM in atmosphere. So.... We did the spin balance IN A VACUUM. We had to procure a spin balance table that could survive a rough vacuum. We put a giant bell jar over the whole spacecraft and spin table , pumped it down to rough vac and performed the balance measurements without "atmosphere".

[@ManBearPigCreative]

Scott manley is always a reliable pick me up on a dreary afternoon!

[@realulli]

2:32 just to put things into perspective: that fairing is slightly smaller than the fuselage of a Boeing 787. At Max-Q, it's flying at the operational altitude of that 787 (around 38.000-45.000 feet). However, it's going through the air at Mach 1.5-1.8, accelerating really hard and climbing really fast, hammering through the air with raw power.

[@Ithirahad]

As I see it: In-orbit is just a physical fact; it means you're somewhere circling something via gravity. On-orbit is more of a logistical statement; it generally means you're in a useful stable orbit, where equipment can be used, other things can approach you if needed, and you don't need to maneuver except for station keeping, collision avoidance, or a mission change/new phase of operations.

[@johnhanson6039]

I think On orbit has a connotation that a particular orbit is required, exactly, whereas in orbit will just accept any old orbit

[@christiangrantz6906]

I always got the feeling that "in orbit" refers to anything in any orbit, while "on orbit" referred to a more specific idea, i.e an object could be in orbit but on the wrong orbit. That's just me though

[@budgiefriend]

You spin me right round....😯

[@DrDeuteron]

An on orbit activity is anything that occurs after an instrument on a space craft has been delivered to an operational orbit. In orbit can be anything that goes around at least once.

[@SupGaillac]

fwiw, it's the same distinction in french: "en orbit" (like "in") is for stuffs wandering around the earth, and "sur orbit" (like "on") is when the payload has reach the specific targeted orbit

[@trm4life]

I remember twice maybe even 3 times when I was younger. Living in Central Wisconsin, i was looking to the south and saw lights. One light then 2, then 3, almost evenly spaced. As a 4th lit up the original light faded. It did this pattern a few times before disappearing. Always wondered what that was.

[@davidlabedz2046]

Scott, your viewers ask the most interesting questions! Thank you for the answers!

[@roqua]

11:30 I'm convinced that about 80% of the interest in muon catalyzed fusion is centered around the fun of saying "muon catalyzed fusion" :)

[@scottmanley]

I do enjoy the way it rolls off the tongue.

[@roqua]

@@scottmanley mu mu!

[@zeg2651]

1:04 As far as I can recall from my fluid mechanics course: Dynamic pressure is the difference of stagnation pressure and ambient pressure. I.e. if you have a moving fluid hitting an object, there is a point, where the velocity of the fluid becomes zero. If you were to measure the pressure at this point, you'd get the dynamic pressure + ambient pressure.

[@CarletonTorpin]

20:26 - "obliquity" is an amazing word and the well-eloquted-sentence which contained it, equally so.

[@ericlotze7724]

The “In Orbit” vs “On Orbit” discoourse is a perfect mix of my love for Space Stuff and NPR’s “A Way With Words”, and i am 100% here for it.

[@mathewherges397]

I'm not saying I'm right... however, your satellite reflection theory could explain A LOT of the aerial phenomena we've seen as of late. Stuff that seems to fly at insane speed when appearing out of no where... It may not explain all, but I've seen a recent one where there are 4 or so lights flying in formation, disappear and then reappear. Could be a set of satellites in formation reflecting back off clouds or other parts of the upper atmosphere or ice crystal double refraction, etc. Thanks Scott!

[@major__kong]

You can get as-designed CG and mass moments/products of inertia from any CAD program. You can actually do it with a spreadsheet if you know the component values well enough. Of course, you need the as-built values for the control system. And that's where the tables and swings come in. But that isn't perfect either. So you can do parameter identification using flight test data.

[@benjaminshropshire2900]

IIRC at least one of the spin stabilized Pioneer probes chose to explicitly ignore where the CG ended up because "who cares if it wobbles back and forth a few feet a billion miles that way?!" (I suspect they did still care about the orientation of the principal axes.)

[@bbgun061]

I'm sure the engineers do their best to get the CG close to the center of the spacecraft. For minor errors, most rockets have gimballing engines, and the guidance system can steer onto the correct trajectory as needed. Return capsules usually have an off-center CG so that they can be steered during re-entry.

[@kindlin]

Unless all cables and everything are hardline, which I guess is possible, it would be hard to really capture everything in such a complex assembly. Probably possible, but hard. And then the things Scott talked about starts to come up. Even if you do all the calcs, you'd still want to test it, anyways.

[@rh9909]

Which is exactly what we do during making and trajectory/aerodynamic simulation of students rockets.

[@major__kong]

@@bbgun061 The real problem is the products of inertia - Ixy, Ixz, and Iyz. Those cause the principle axes to not align with the spacecraft's axes. Even with gimbaled thrusters, the thing might wobble if those products aren't small. And you don't try to get the CG as close to the center as possible. You try to get it as close to the designed CG and principle axes as possible.

[@Videoman2000]

I live in Norwa. If I go to a dark enough place I will constantly see satellites on polar orbits passing overhead.

[@therichieboy]

I've missed these Q&As so much! This is maximum dynamic Manley!

[@michaelemmert3922]

As a layman, to me, in orbit implies success (insertion, its up there, going round). On orbit implies great specificity (on track, exactly where it should be, following the path)

[@ale131296]

Regarding the sound of engines being very particular relative to others... As one of the commentators for NSF, I could give the usual snippet of "neat info" that the Merlin engines are the only ones that make the VAB doors squeal with their resonance frequency. Not sure why that engine and only that engine creates that effect and why it has that certain frequency but definitely interesting to think about regarding that question you had. Wish there was a way to look into it!

[@RyeOnHam]

The Delta IV uses ablative cooling for the exhausts, which means that the interaction between the gas and the bell nozzle are more energetic than, say, an RS-25.

[@padders1068]

Scott, great video as ever. Thanks for sharing! 🙂😎🤓

[@dancingwiththedogsdj]

I loved how you described the sound of the rockets.... I have never heard a real launch of a rocket, but I love listening to engine tests and a high quality Saturn V launch is incredible. Just crank up the volume and turn up the bass so the house shakes violently when the Saturn launches then watch a few different videos and it should provide a pretty reasonable comparison. :-)

[@BrianFedirko]

yeah, i'm with you on that. the sound has always intrigued me as I have studied synthesizers my entire life. i would love to experience the actual event, as I imagine you feel the air get sucked in/out of your lungs... incredible. ☮

[@gordonstarship]

I love this channel.

[@Mr2winners]

Spoting sats in dark nights is always fun , can even spot some debrees that flashes irregular reflections

[@obsidianjane4413]

@15:20 "Potatoe Potato" On orbit- Spacecraft is in its final planned orbit it was intended to achieve where its doing its mission. In orbit- General term for anything in an orbit about something else. Could be maneuvering or not.

[@GigAnonymous]

15:00 As far as I understand, "in orbit" is a location, "on orbit" is a trajectory. Pedantically, tt could be argued that "in orbit" only makes sense in some frame of reference, whereas "on orbit" is always technically correct.

[@SimonAmazingClarke]

Centre of Mass. At last a question that I can answer as an expert. Within aerospace design we have the weight for all standard parts, and calculate the weight of all manufactured components. This what I do as a Weights Engineer, also known as a Mass Properties Engineer. We collate all of this information and ensure that the aircraft, spacecraft stays within limitation. For spacecraft especially we also look at Self Inertia as well as the Inertia of the spacecraft. Once built items can be tested to ensure the calculations match what has been built. For aircraft this can be as simple as weighing and calculating the CG. All very interesting work especially with modern CAD.

[@adrianf.5847]

16:35 Correcting for a misalignment may cause inefficiencies by increasing the air resistance due to the slightly tilted state of the rocket.

[@fredcrayon]

Q - very handy when designing 🔊 subwoofers too!

[@MonkeyJedi99]

Scott is lying to us! We all know Max-Q is when the Astin-Martin has a passenger ejection seat AND machine guns behind the headlights.

[@DrDeuteron]

That is a totally different Q, but you know that

[@fredcrayon]

@@DrDeuteron Yes, indeed, in that application Q stands for quality factor, but it ‘s still Q!😂

[@colinfield981]

Yep, Ive got the Michael Hutchence Max-Q on vinyl. Good album

[@MCsCreations]

Thanks for all the answers, Scott! 😊 Stay safe there with your family! 🖖😊

[@sulijoo]

I have a question...about KSP. We all know it's possible for the Mun to cause eclipses....but what about Minmus? Is it too far away? I'm guessing it could only happen at the AN/DN and after the right Sun/Kerbin alignment; how frequent would that be? But even it's too far away, wouldn't it be like the Phobos/Deimos eclipses seen from Mars?

[@sycodeathman]

Minmus is far too small and distant to cause a total eclipse, instead it would transit the Sun. Wouldn't be visible to the naked eye, because the sun is so bright (this is why you need eye protection to see a partial solar eclipse, too)

[@Michaelonyoutub]

I am pretty sure you are exactly correct, when passing the AN/DN, when Kerbin and the Sun are lined up correctly, there should be an "eclipse", though it wouldn't block much of the sun, merely dimming its apparent brightness to casual observers on the ground. It would be more similar to a planet "transiting" in front of the sun than a total lunar eclipse, though with a more significant effect on the apparent brightness. Phobos/Deimos eclipses as seen from Mars would be a good comparison. I am pretty sure minmus was meant to be a sort of Phobos/Deimos analog, like what would Earth have been like if we had a small moon like Mars's moons? What would it look like from Earth's surface and how would it affect the space race?

[@Br3ttM]

According to the Wiki, The Mun shouldn't cause a total eclipse, just a partial one, because the sizes and distances in game aren't evenly scaled down compared to real life. That means that the way it looks from Kerbin is altered/faked to make the eclipse look a certain way. Other bodies might not have specially coded in eclipses, so it might not be visible at all even when math says it should.

[@adrianf.5847]

2:03 I don't get why the pressure would be evenly distributed, and from which numbers you infer that the pressure-active area of the fairing is about 27m^2, and why the fairing is the only thing that should count for the total force.

[@adrianf.5847]

In fact, the area of the fairing looks like it's significantly larger than that. But in order to do the geometry, I'd have to know more precise specifications.

[@michaelmurray2595]

Once more, a great video. Many thanks...

[@adrianf.5847]

5:45 If you do it optimally, you'd do the burn in the lower (in terms of altitude) part of the orbit, so that at first, you would move lower down and increase your Oberth effect efficiency, and only after half the burn (or slightly after it if you perform the optimisation you mentioned), the Oberth effect efficiency would go down again.

[@hanschristianben505]

good day good sir! future video suggestion I remembered that episode you did a few years back when you assembled a scale model of the Saturn V using the Revell kit, as well as your livestreams of lego projects… why not do an episode, or episodes, dedicated to scale models of spacecraft, and X-planes, featuring works done by you, your viewers, patrons, and subscribers? just a simple featurette discussing your viewers’ works, what impressed you, project ideas etc… you can ask people to submit photos/videos of their projects to your email address or tag you on their social media account(s)… I think it’ll be fun for all, a bit of a new twist to your video subjects

[@davidkavanagh189]

Even in Ireland, in the summer you can often see each night fly over of the ISS, sometimes seeing it as many as 4 times in one night because it has line of sight of the sun over the pole.

[@IMGd]

Hey Scott. Regarding "on" or "in orbit": From my understanding of the language, "on orbit" means, you actually are in the orbit that you desire, as opposed to "in orbit" just means that you somehow fall around a heavy object, without getting close enough to deorbit unintendedly fast, disregarding what the exact parameters of that orbit might be. Examples: "on target" "on spot" vs. "in the area" But that's just a hunch. With kind regards Clyde

[@iankester-haney3315]

Orbits are technical. In Orbit could mean any orbit. On Orbit implies the intended/correct orbit.

[@adrianf.5847]

8:40 Maybe they want to have more space on Starship for voluminous, but low-weight materials (such as oxygen).

[@StevePemberton2]

"just look at the rocket and see the color of the exhaust", true for most rockets, however with SpaceX you have to also know the sounds because they don't mind launching (and landing) things in pea soup fog.

[@bipolarbear9917]

Wouldn’t the phrase ‘on orbit’ apply to the first person (e.g. ISS astronaut), while ‘in orbit’ is spoken from third person perspective? That would be my guess. I’ve heard the same query about this interchange of prepositions with ‘in the road’ or ‘on the road’. The quirks of language.

[@mytube001]

"On orbit" is obviously meant as an equivalent to "on course" for a ship that is on its intended course. It conveys that the current orbit matches the intended parameters. It shouldn't be used to describe the general state of orbiting something. That is what "in orbit" is for. Always has been and should be going forward. This whole "on orbit" thing started just a few years ago. You would never hear it before that outside of the specific meaning, where it is correct and appropriate.

[@adamreznik6374]

This is incorrect. Not new. Astronauts have been saying "on orbit" for a long time. The layperson will say "in orbit" just like they call parts of the airport surface the "tarmac." Astronauts say "on orbit," just like airline pilots say "ramp" or "apron," or "taxiway" or "runway." We NEVER say "tarmac." Of course, laypeople use "tarmac" to act like they know what they are talking about.

[@OregonOrcadian]

Fab discussion of muon catalyzed fusion Scott! Love your channel.

[@jackalcrackle]

I think On orbit = on target orbit trajectory, and In orbit = is orbiting on any trajectory that is a stable orbit

[@adrianf.5847]

20:36 No, you're seeing reflections of the sun on satellites. Apart from that, it doesn't seem to have anything to do with the polar cycle, and furthermore, the satellites may also be not exactly in the direction facing away from the sun, so that they are not yet (or not any more) in the shadow of the earth.

[@avitiello100]

Scott, has anyone tried variable rocket bell sorta like the way an after burner works in a jet engine. Seems to me this would be more efficient when transitioning from the atmosphere to space? Love your videos. Thank you so much for doing them.

[@bbgun061]

The upper atmosphere is low enough pressure that a vacuum-optimized nozzle works well enough for upper stages. A variable nozzle might be more efficient but would also add a lot of weight. All designs have trade-offs.

[@GavinEarnshaw]

This is kinda why people love aerospike design. Stoke space is doing something a bit different to get the same effect.

[@bngTaylor]

If a booster had sea level optimized motors surrounding a cluster of vacuum optimized motors and all fired at liftoff wouldn't the central cluster (vacuum motors) be burning in a low pressure environment produced by the surrounding sea level motors? This would allow the outer motors to cut off when the ambient pressure and propellant mass have decreased.

[@AndrewScott83815]

I fly for delta and it’s almost a nightly discussion on guard. I have pretty good videos of it. Let me know if you want the video. It definitely looks spooky even to a veteran skywatcher.

[@Feszy_]

Thanks scott

[@arminulrich2319]

2:10 The pressure on the fairing is not homogenous. We have that q (or q_max) only in the stagnation point of the rocket.

[@Thorazine1112]

I grew up in the 60’s, and everyone said “in orbit”. It wasn’t until the 80’s that I heard the phrase “on orbit”. Somewhere along the line someone decided to change it. To me it sounds strange. It’s similar to the situation where I, who lives in the Midwest US, say “I stood in line for the movie tickets”, whereas a New Yorker would say “I stood on line for the tickets”

[@quantumblur_3145]

You met a weird youker

[@Lightkie]

18:53 "There.. are.. *four* lights!"

[@adrianf.5847]

You can actually find the center of mass by shifting it until it drops off a cliff. You have to do it twice in two linearly independent directions. If your satellite shall survive that, choose the cliff to be very small.

[@richb313]

Thanks for explining this.

[@DUKE_of_RAMBLE]

Shout out to the engine nozzle, for being so thin, but also a cup, and so holding up to the reentry pressure! 🤘

[@arctic_haze]

The phrase "on orbit" seems to me a calque (literal borrowing) from Russian "на орбите". The reason may be the amount of stuff translated from Russian in the early days of the space race.

[@christophervanmeier1648]

Great video. As a teacher, in orbit means that the craft has reached a specific altitude. It could be any of an infinite number, but all the same distance from the center of the earth. While on orbit would mean the craft has reached a specific orbit...the only one of of the infinite possibles. Mahybe?

[@bbbenj]

Thanks a lot 👍

[@General12th]

Hi Scott! Fly safe!

[@patrickmchargue7122]

For fusion-powered thrust, look into using a dense plasma focus device.

[@dougaltolan3017]

Starlink satellite "flare"... Starlink orbital height is ~ 550km. Horizon at 550km height is ~ 2700km. Most southerly location that an illuminated starlink satellite can be viewed (spherical cows in a vacuum calcations) is 5400km south of the Arctic circle. So at midnight on summer solstice, anywhere more than 16 degrees north *could" see an illuminated starlink satellite to the north.

[@BackYardScience2000]

3:50 , Reminds me of Max Headroom. Lol

[@bwjclego]

I may be wrong, but my understanding of 'on orbit' is that it is used to describe the state of something that is doing something, whereas 'in orbit' simply describes a place. Basically, you *do* things on orbit, but you *are* in orbit. 'On orbit' seems to be almost exclusively used like an adverb. "After engine shutdown, the spacecraft was in orbit" "The antenna was used on orbit to transmit diagnostic data to ground stations" "The facility was operated on orbit" Or even, to show the different, "While in orbit, the astronaut spacewalked" VS "The astronaut spacewalked on orbit". Of course, I don't think it is hard and fast, but I generally see them being used in this way.

[@GabeJChorabik]

On Orbit: On (an) orbit(al trajectory) - a reference to an achieved vector, an intentional / designated condition, specific to man-made objects - in orbit: in a state of orbit, be it intentional or by chance, encompassing man-made and natural objects....?

[@adrianf.5847]

4:35 Zero is a finite number.

[@twistedmovies8782]

I submitted a pretty good question about the items in space and how they dodge the shit trying to get through it, and how more and more makes that harder. How long until we cant get through?

[@TheEvilmooseofdoom]

Usually the easiest avoidance move is to slow down or speed yourself up a tiny bit. How long until we can't get through? A long time yet.

[@twistedmovies8782]

@TheEvilmooseofdoom it's just a giant game of frogger.

[@Br3ttM]

It depends on how much the amount of things in space increase compared to how much our tracking improves in both precision and minimum size of the objects. Better sensors and records mean we can make more accurate predictions, and make them farther ahead of time, making it easier to change orbits to prevent collision.

[@erinw6120]

I do remember the Michael Hutchence "Max Q". Think I still have that album on cassette in a closet somewhere.

[@ImNotPotus]

For a Rocket on an escape trajectory is there any possible instance where MAX Q can occur before MACH 1?

[@Benoit-Pierre]

A long comment explains that yes but hardly. Maxq is almost always just above mach 1 due to sound cone ...

[@stevenverhaegen8729]

Blanco lirio did a great video explaining satellite flaring seen from the flight deck 👍

[@Tom_Hensley]

Scott, we like to see your view on UAPS, UFOS, ETC...

[@Vatsyayana87]

I feel like the difference of in orbit to on orbit is perspective, even though both are correct from both perspectives. Kind of like saying from an outside perspective "This happened to these people while in route to said destination" and a person in the situation might write "This happened to us while on route to said destination"

[@keshzal]

What happens when a following spacecraft or satellite flies through the exhaust cloud left from the engines in space?

[@TheEvilmooseofdoom]

It gets bathed in exhaust gas, has to be pretty damn close for that to happen.

[@Michaelonyoutub]

Better probably to think of an exhaust gas less as a "cloud" and more as tiny rapidly moving particles, and given their speed they will either reenter the Earth's atmosphere or escape the Earth's gravity, there should be basically no in between, meaning no stable orbits. As for what happens when a satellite meets another spacecraft's exhaust gas, the particles can be almost thought of as fast moving bullets that either pierce through/into the satellites or bounce off, depending on the size, mass, and momentum of the particles. Satellite are generally built to be resilient to random fast moving tiny interstellar/interplanetary particles, up to the size of micrometeorites, so they should hold up to a little bit of some random rocket's exhaust gas shooting at them, but the more they are exposed to it, the more damage/deterioration they would sustain. I don't know if it is a significant enough threat for space agencies to worry about and take significant precautions against, Scott might be better able to answer that.

[@Br3ttM]

There's already sparse gas above the official edge of the atmosphere. A little rocket exhaust doesn't change that if you're not close enough to risk two spacecraft colliding, so it really only matters for staging or docking.

[@simongeard4824]

@@TheEvilmooseofdoom Did you see that RocketLab launch video some time back where you could *hear* the upper stage pulling away, due to the sound of the engine transmitting through the exhaust plume...

[@roberthiers3460]

It is important to realize that maximum forces do not occur at max q, but rather in the neighborhood of max q. A great example is some Saturn data (google: saturn flight manual SA 507 and see Figure 2-4.) Mach 1 occurs about 15 seconds before max q, and the axial force peaks almost exactly in the middle between Mach 1 and max q. The actual maximum axial force is almost 30% greater than the force at max q.

[@AndrewHillis_2024]

What is a Gravity Turn & how does it work?

[@NormReitzel]

From Alvarez' paper, "Another benefit of muon-catalyzed fusion is that the fusion process can start with pure deuterium gas."

[@randygreene5977]

On the question from David Foote, I think he may have seen an Iridium satellite. They are known for flaring. Most of the time I have seen them flare they have been in the north.

[@steveskouson9620]

Scott, a few months ago, my roommate called me outside. He wanted me to see this string of lights, going from the left, to the east. About a dozen or 20 or so, stretched out in a line. The line looked to be about 2 feet long, at an arm's length. Later that evening, (like right after) I looked for a Starlink launch. Yep, there was one, earlier that evening. steve

[@DrDeuteron]

Nyet!

[@scottvandezande5874]

Thanks for answering my question! My daughter says I’m famous now 😊

[@LeCharles07]

I tend to agree with many of the comments that say 'on orbit' must be more specific and means a craft is in the target orbit similar to how the military uses the phrase 'on station'.

[@lanceferraro3781]

What is the matertial that falls away from Chinese rockets as they climb from the pad?

[@JohnWilliamNowak]

I believe some Chinese boosters with cryogenic fuels are cladded with insulation designed to peel off in the airstream.

[@marcmcreynolds2827]

@@JohnWilliamNowak Likewise for France's first orbital booster Diamant. The (non-cryo) first stage was cladded or not depending on ambient conditions.

[@lanceferraro3781]

Thanks. That makes sense.@@JohnWilliamNowak

[@snappycattimesten]

Whether it’s god or the bomb, It’s just the same. It’s only the fear under another name - Max Q. (Great song!)

[@brucegoodwin634]

24:29 Ballzon images of a shuttle launch; Space porn. I learned a bunch in this vid, Scott. How does faring (nose) shape affect dynamic pressure?

[@mamulcahy]

Scott, the sh*t you know always amazes me. It makes my brain hurt! Lol

[@dogmaticpyrrhonist543]

The sound would depend on a lot of factors. And, while I don't doubt you could nail down any known rocket engine, I doubt you could tell the difference in an unknown engine between say UDMH v Hydrazine or NTO v RFNA or so on. If the exhaust velocities are roughly similar, it would be a hard damned task. Picking a Hydrolox from a Kerosene+LOX is probably totally doable though. But as Scott mentioned, just looking at the flame tells you that much faster (without ripping your ear drums apart)

[@donaldsimonds7513]

Thanks

[@Spedley_2142]

In orbit sounds permanent. On orbit sounds like a rendezvous.

[@npbiggs4382]

Great show. How do they get fuel to the engines in zero G and when the rocket is dropping through the atmosphere? Would like to know if the ambient radiation of space could be harnessed to create energy for the spacecraft? Seems like there is limitless radiation available in space. Thanks again.

[@TheEvilmooseofdoom]

The rocket dropping through the atmosphere is not in free fall it's slowing down steadily.

[@npbiggs4382]

@@TheEvilmooseofdoom Never said it was! Yet a rocket that lands has to do both. Slowing down would still leave the liquid inside subject to momentum as well as gravity

[@h.dejong2531]

Getting fuel to the engines in 0 g: there are a few methods. One is to do an ullage burn: run some small thrusters to provide enough acceleration to settle the propellants at the bottom of the tanks. This is usually done for large engines. Another is to have fuel in a bladder under tension, or to have a structure in the tank that the fuel will tend to adhere to, which can wick the fuel into the engines. These can be used for small thrusters.

[@npbiggs4382]

@@h.dejong2531 Thank you.

[@therickson100]

In orbit is a preposition--you are "in" orbit. On orbit is an adjective--you are doing something (a verb) while "on orbit." I cooked a meal while on orbit in a space shuttle which was in orbit.

[@richiehoyt8487]

Sorry if this is a dumb question (not to mention that I'm putting it a bit late in the day), but in the discussion and graphic about satellites flaring, it seemed that a high degree of importance was placed on avoiding satellites inadvertently flashing solar reflections back to the Earth... Why? The only thing that comes to mind personally is the danger of dazzling pilots, a bit like with the laser pointers flashed by fools with too much time on their hands at aircraft. I suppose the light reflected by a large array of solar cells in a worst case scenario might be significant, but I still have difficulty in imagining that such a flash could be bright enough to be hazardous, even if prolonged. No one worries about reflections coming _up_ from the ground, off of rooftop solar cell arrays, after all! (Though that _would_ be during the day, of course!) Or am I barking up the wrong tree with my idea about aircraft safety?

[@wildbill228]

Hello Scott. I've just rewatched the 1986 film "Spacecamp". I've not seen it since it first camp out. Please, please, please can you have a watch and make a video about it. Was spacecamp a thing? Was space station deadleus a thing? I'm sure most of the film was just fiction, but rewatching as an adult(after a bottle of wine) was great. Love the channel. Keep up the great work.

[@TiberiusMaximus]

can someone give me the link of that service that shows the solar system and all the orbits of planets and space probes?

[@Rorschach1024]

How is COM found? Quite easily, every object going on the vehicle is weighed and modelled in 3d. Then the models are placed in the craft in the cad system andcthe cad system sorts out where the com is.

[@kristensorensen2219]

Keep flying safe and working on your Instrument rating🎉

[@arturoeugster7228]

Dynamic pressure is strictly just the product ½ density times V², while it has the dimension of pressure, in compressible flow it is not the stagnation pressure, It is the specific kinetic energy of the relative approaching flow. As prof. Burgers points it out.

[@Benoit-Pierre]

Some comment explains that max q occurs most often just above mach 1 due to the physics of the sound barrier ... And is weekly related to fairing shape and altitude. It was one of the first 12 comments ....

[@RICK82873]

Question well more of a thought experiment. If there is a earth like planet out there with a civilization with the same technology as we have today. However the gravity was higher and the atmosphere proportionally thicker. At what point would that civilization be unable to access space or at least be unable to access space with a payload worth sending. Curious because I keep hearing about these earth 2.0 with 3x the earth’s gravity. Thank you.

[@iamjcarl]

i have a question: in end of service of the ISS. is it possible to boost it to the moon as a moon station for future missions?

[@simongeard4824]

Remember that when you say "end of service", you're talking about something that's sufficiently worn out that it's no longer usable. So while, yes, in principal you could spend a vast sum of money relocating it to the moon, you'd be spending it on something that was already deemed unfit for purpose...

[@TheEvilmooseofdoom]

What do we need a moon station for?

[@thomasbrown5738]

Just curious, are any or all of the Space Shuttle's big red fuel tanks still in orbit? Or have they all been de-orbited?

[@h.dejong2531]

They never reached orbit. The Shuttle used its OMS to add the last few m/s of speed to get into orbit.

[@chrisbragdon5901]

22:36 time to dump chemical propulsion rockets and just use warp drive. Go cleaner, farther, faster, and safer with warp drive.

[@scottmanley]

Let me know when you make that work.