Deep Space Questions: What Is Max-Q? Strange Lights In The Sky? Orbital Grammar?
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- čas přidán 29. 10. 2023
- A new installment answering questions from my supporters over at Patreon, answering questions with minimal preparation, and maximum speculation, and maybe sometimes getting things right.
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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.
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.
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.
My thought exactly! "On a specific orbit" / "on its assigned orbit" vs "in orbit somewhere".
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.
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)
I think On orbit has a connotation that a particular orbit is required, exactly, whereas in orbit will just accept any old orbit
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.
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".
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
You spin me right round....😯
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.
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
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.
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
Any chance you're going to write/record a short review of it?
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."
As we all know from the documentary named Gravity (2013), The Orbit is a dark flat place sized about 100 kilometers by 46 minutes.
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.
welfuk I bought into wienersmith's religion series, so i outta buyinto this one.
Scott manley is always a reliable pick me up on a dreary afternoon!
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.
I live in Norwa. If I go to a dark enough place I will constantly see satellites on polar orbits passing overhead.
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" :)
I do enjoy the way it rolls off the tongue.
@@scottmanley mu mu!
"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.
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.
Scott, your viewers ask the most interesting questions! Thank you for the answers!
I've missed these Q&As so much! This is maximum dynamic Manley!
Thanks for all the answers, Scott! 😊
Stay safe there with your family! 🖖😊
Scott, great video as ever. Thanks for sharing! 🙂😎🤓
20:26 - "obliquity" is an amazing word and the well-eloquted-sentence which contained it, equally so.
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.
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.)
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.
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.
Which is exactly what we do during making and trajectory/aerodynamic simulation of students rockets.
@@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.
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!
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.
Once more, a great video. Many thanks...
Spoting sats in dark nights is always fun , can even spot some debrees that flashes irregular reflections
Fab discussion of muon catalyzed fusion Scott! Love your channel.
Thanks for explining this.
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
Q - very handy when designing 🔊 subwoofers too!
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.
That is a totally different Q, but you know that
@@DrDeuteron Yes, indeed, in that application Q stands for quality factor, but it ‘s still Q!😂
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.
I love this channel.
Orbits are technical. In Orbit could mean any orbit. On Orbit implies the intended/correct orbit.
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.
Thanks scott
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
"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.
Inches of mercury??? No, no, it is millimetres of mercury, please. 😂
I have bad news about flying planes.
Fuck it *Barleycorns of Quicksilver*.
Why stay on the fencepost and use moderately sensible units, or be proper and use Metric/SI, be CONFIDENT in your choice of obsolete units. Have the people reading your paper shudder in fear!
@@scottmanleyfeet just feel better when flying.
Microfurlongs of Mercury sounds better
@@Forest_Fifer true, although I’d recommend using a non-base 10 (or even base 6 or 12…or even bases all together) system for the different sized units.
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.
I think On orbit = on target orbit trajectory, and In orbit = is orbiting on any trajectory that is a stable orbit
Thanks a lot 👍
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. :-)
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. ☮
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.
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.
Hi Scott!
Fly safe!
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!
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?
Yep, Ive got the Michael Hutchence Max-Q on vinyl. Good album
@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.
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.
Thanks for answering my question! My daughter says I’m famous now 😊
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.
From Alvarez' paper, "Another benefit of muon-catalyzed fusion is that the fusion process can start with pure deuterium gas."
Thanks
I love ur content
18:53 "There.. are.. *four* lights!"
For fusion-powered thrust, look into using a dense plasma focus device.
Scott, we like to see your view on UAPS, UFOS, ETC...
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.
Shout out to the engine nozzle, for being so thin, but also a cup, and so holding up to the reentry pressure! 🤘
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.
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)
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”
You met a weird youker
Blanco lirio did a great video explaining satellite flaring seen from the flight deck 👍
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.
i came for space questions, i stayed for trivia from Australian alt rock bands in the 90s.
Keep flying safe and working on your Instrument rating🎉
Scott, the sh*t you know always amazes me. It makes my brain hurt! Lol
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.
I do remember the Michael Hutchence "Max Q". Think I still have that album on cassette in a closet somewhere.
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"
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.
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.
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.
In orbit sounds permanent. On orbit sounds like a rendezvous.
I love the conversation Dimitri Moisevitch and Dr. Heywood Floyd have at the beginning of 2010: The Year We Make Contact.
Whether it’s god or the bomb,
It’s just the same. It’s only the fear under another name - Max Q. (Great song!)
I'm going to start measuring dynamic pressure in mmH2O now.
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.
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'.
Aren’t there also a Max Q that’s a computer generated floating head on TV in the 80s’?
That was Max Headroom.
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)
8:40 Maybe they want to have more space on Starship for voluminous, but low-weight materials (such as oxygen).
Ah you slipped! You said Maths! (10mins in). Welcome back! 🇬🇧
Well now I want to make a band named Max-Max-Q
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
Nyet!
I have that MaxQ cd 👍Great album
In Robert Forward’s “Dragon’s Egg” the human starship is propelled by a muon catalyzed fusion drive.
I see "in orbit" as any orbit trajectory, and "on orbit" as being on a specific targeted orbit trajectory.
16:35 Correcting for a misalignment may cause inefficiencies by increasing the air resistance due to the slightly tilted state of the rocket.
On orbit, suggests that a spacecraft is in its designated orbital parameters, ie on a nominal orbit.
I agree. And I think "on orbit" typically describes where operations take place. So not in a transfer orbit, for example.
Ur the best
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.
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.
You've gotta drop a stage when the fuel runs out. Nobody's going to design a spacecraft which requires you to carry the empty first stage all the way to space just because they want to use a variable nozzle.
If you drop the stage, you drop the nozzle. The next stage will have the correct nozzle for that altitude.
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.
This is kinda why people love aerospike design. Stoke space is doing something a bit different to get the same effect.
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.
muon, electron, proton - you spent years on those boxes ;-)
I get that reference
@@scottmanley
Not been on in a while though :-)
Last On : Tue Aug 19 02:58 '03
3:50 , Reminds me of Max Headroom. Lol
@scottmanley I suspect that "on orbit" means that an object means that the target is "on" the intended target orbit, not just "in any orbit"?
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.
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.
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?
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)
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?
@@sycodeathmanSun? Kerbol! 😃
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.
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.
They call it dynamic pressure because the pressure is dynamic and not constant, there can also be parts of the rocket that eddys or vorticies which make very high pressure points unevenly around the rocket... even more so dynamic... max Q is just a famous singer from the nineties I thinkl.
"In orbit" is generic, whereas "on orbit" connotes "in a specific, or planned" particular orbit. I think.
So apparently I'm a helium nucleon. Thanks Scott
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.
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 ....