Why Are Airplane Engines So Big?

[@EasiLeo]

That plane at the end looked adorable.

[@nates9536]

Look up the Boeing X Plane

[@brandonvelde5774]

That's the Stipa Caproni airliner edition.

[@BatDan513]

Henry - Great video! One minor clarification: The core of the engine does actually produce a significant amount of thrust in a high-bypass turbofan - when at altitude. It's about 50/50. This is due to the density of the air being much lower at 30+ k feet, the fan is not drawing as much mass flow so it can't impart as much momentum. As such, the fan's power consumption isn't as high, which leaves more enthalpy available to convert to thrust coming out of the core nozzle (the turbine driving the fan doesn't need as much at cruise). At takeoff, though, you're trying to squeeze every last drop out of the fan and therefore there will be very little energy left over to make thrust out of the core. At this point, the fan absolutely does produce the majority of the thrust (~ 85/15).

[@kaczan3]

I want the last plane.

[@Crick1952]

Me too

[@kaczan3]

+tver I came.

[@redhairdavid]

+kaczan3 i want some science on why that last plane wouldnt work.

[@QuantumLeclerc]

+kaczan3 KSP

[@redhairdavid]

kerbals are always the answer

[@WhyDoesMyCodeNotCompile]

Another reason for bigger engines is noise. Because the velocity of the air travaling through the engine is proportional to the sound produced by compression shocks inside the engine. If you want to build quiter engines, you have to reduce the velocity of the air, but in order to compensate for the reduction in thrust, you need a higher mass flow rate. This is archived by a bigger diametre of the engine. Another limitation for the size of airplane engines are the standard sizes of airport hangars, that one reason why in recent development for example, of the Trent 900, the casing for the air-intake is elliptical rather than round.

[@Prometheus2508]

+Sinan Al-Khadra While not true, it should be noted that a surface with air moving different velocities on either side will generate induced drag as well as a lot of noise from the vortices.

[@filiposvald1861]

does it applies to cats as well?

[@ErebusTheDragonn]

Sinan Al-Khadra what?

[@Taladar2003]

There are also various tasks performed on the ground that get more difficult the higher up the main fuselage of the airplane is off the ground and engines mounted below the wings are the main factor influencing how high that has to be. Not to mention that the landing gear causes more drag and needs to be more sturdy if it is longer too.

[@GundamZeroSeven]

The large turbine is also referred to as a bypass fan. In addition to trust, it also helps to create a cushion around the jet exhaust, helping to reduce noise vs a regular jet engine.

[@sciencetoymaker]

Great example of the difference between momentum and kinetic energy! It's difficult to intuitively grasp why one has a linear increase with velocity and the other the square of the velocity; and there is not much on KZbin. That would make another wonderful video. In any case, I consider myself so fortunate to be able to watch your videos; keep up the good work!

[@22BIKS]

1:31 The last plane is so cute

[@ejitp6cl6]

+22BIKS I just want to comment that XD

[@JBTheMighty]

+22BIKS There was a plane made in 1932 that if worked may have become the one he drew. its called the Stipa-Caproni.

[@22BIKS]

JBTheMighty Thanks for letting me know XD

[@DirtMankee]

+Fallen Exe Oh yeah that is true. That plane isn't a airplane it is bird killer

[@JBTheMighty]

***** It would never be as good as the planes today.

[@rafiahmedchowdhury7977]

1:31 I died XD:

[@tren-y2m]

R.I.P

[@simonriley849]

Rest in RIP bro

[@indjev99]

+Simon Riley RIP in peace is better.

[@TaliesinMyrddin]

+Rafi Ahmed Chowdhury Ah yes, the Kirby 707 was a good attempt at aviation, but unfortunately it sucked too much.

[@ILovePeanutButer7181]

+TaliesinMyrddin that was one of the better puns i've heard in a while. gg

[@TheXtremeunleashed]

most people have no idea how incredible air planes really are.

[@herkusr01]

Ikr

[@diondredunigan2583]

+TheXtremeunleashed ikr

[@apburner1]

ikr pdq kp lmfao tits

[@cloroxbleach1200]

+TheXtremeunleashed Whenever I get in a plane I think about how incredible machines they are.

[@diondredunigan2583]

Shaheer Syed I know, it took me so long to learn about aerodynamics.

[@DesktopArtsHD]

By far one of the best "to-the-point" videos broken down to my simpleton level. Bravo minutephysics ;)

[@FirePandaGames]

There are a LOT of reasons as to why engines are like they are, what I find funny though is he focused on the larger commercial planes, but had a tiny side note for ramjet and turboprop, but very little to none on the prop planes, the Boeing aircraft use large engines for efficiency and speed, while the Dash 8 Q400 and ATR72 have tiny little engines that are much smaller and slower, but have a bigger range then some airliners and have massive fuel savings as being the most fuel efficient aircraft available, all Boeing and Airbus make are aircraft to shove people into and get them from point A to point B quickly, and most engines on those aircraft are limited by wing-ground clearance not just limitations of the engines themselves

[@jibeneyto91]

I'm an aspiring MSc Aero Engineer and must say, I'm impressed. The video explains a complex topic very well in just 1 minute. Some minor "imprecisions", but very well done!

[@ChrisDeBruinMrAwsomeGlopGlop]

What a great intro to that Audible ad!

[@paco4668]

Love these videos more please :D

[@karendixon2250]

agreed

[@villager1831]

Daddy Sakurai nerfed you, hihi!

[@abyssalreclass]

Modern fighter jets have dropped turbojets in favor of turbofan engines, for the same reason as the commercial airlines. They just tack on afterburners for more thrust when needed.

[@cockatoo010]

Low bypass turbofans

[@whoyoulookingatabs1028]

Nope. Fighter Jets use Turbojets because using a Turbofan with an Afterburner will just defeat the purpose of the Afterburner, if you don’t know Afterburners are used to burn the remaining Oxygen that exits the engine so they can create more thrust. But only one Jet in history used a bypass system and that is the Lockheed SR-71 Blackbird where tubes connected to the 4th Stage Compressor took air and sent it directly into the Afterburner

[@vladivosdog]

@@whoyoulookingatabs1028 nope

[@fransisigos]

@@whoyoulookingatabs1028 Very wrong

[@creeper6530]

But they have lower bypass ratio than airliners

[@AkhilPisharody]

can that last plane carry me to Global Elite?

[@smartguy9765]

+AXE PIDY Underrated comment.

[@malnutritionboy]

silver 3

[@sebimoe]

+AXE PIDY It would need a bigger engine

[@Cd5ssmffan]

Fucking csgo tryhards

[@Cd5ssmffan]

Melting Clocks I don't play cod, salty kid.

[@DestinyQx]

finally was able to understand equations at 1:25 when realizing |sec didn't mean LINE SECANT.. but ONE SECOND.. sigh..

[@TheBluePhoenix008]

Oof

[@nadiyayasmeen3928]

Ideal engine diameter

[@Gibbo263]

Its all to do with bypass ratio. You can also increase thrust by producing an engine with a much smaller core but the same fan diameter. Assuming you can create a core that has the same power output

[@rmta-8524]

a rough estimation

[@karapapaxatzidimitrakopoulos]

XD XD XD

[@shutdahellup69420]

Mr_____ - dead asf

[@Bazo1337]

1:20 yes, yes, I understand some of those characters...

[@TheBluePhoenix008]

All of these are mostly taught by the 8th grade Source: Just passed 8th

[@wellshit9489]

@@TheBluePhoenix008 education ain't universal like that

[@VincentGuillotine]

1:15 "then it starts to cause too much DREG"

[@VincentGuillotine]

+Kivtej Rakhra he says dreg

[@itskelvinn]

Dont do dregs

[@АлександрБелкин-п7м]

@@itskelvinn хюжэзмэжп

[@elijahsimmons2900]

Interesting because in spacecraft its all about high exhaust velocity, which means more efficiency... Having air everywhere is such a valuable resource!

[@22yhjjjj]

omg ENDERS GAME. I loved that book. Its what got me into space games.

[@kasyu1101]

This system actually works in reverse when talking about things with high vacuum efficiency, since the faster the exhaust moves the higher the specific impulse (about 100s for every Km/s of exhaust velocity), since the energy wastes don’t matter when rockets don’t have fans.

[@1dimosssss]

I understood the machine-gun part! I'm smart!

[@TheGamerzTown]

+DimesTR I didn't.

[@PumpkinsAmongUs]

+Jonathantje / Bammerbom XKCD Refrence? I'm not sure

[@Neowattmk4]

+Jonathantje / Bammerbom Drastically over simplifying, a machine gun is like a very inefficient rocket engine, but instead of shooting out hot fuel and oxidizer it shoots bullets. Due the recoil produced by most guns being rather small to a car it doesn't move the car much.

[@penguin9941]

I hope so

[@jessicaking1667]

DimesTR no you're not

[@wax88]

Good video, but just 1 thing, modern fighter jets also use turbofan engines, mainly because you still want your fighter jets to be able to be able to fly for an appreciable amount of time. The main difference between a jet used for fighters and commercial jets is the bypass ratio. In general fighters use a lower bypass ratio because there is a bypass ratio limit after which after-burning (or reheating) becomes difficult to achieve.

[@UniverseGOD2525]

Never been so early in this channel

[@hedlosa9574]

Same

[@0deadLP]

+Shiben Chakravorty Same

[@droptable1610]

+Shiben Chakravorty Agreed

[@vincentm.2458]

+Shiben Chakravorty wow... and i just woke up too... early ftw

[@denhafiz1860]

+Shiben Chakravorty Me 2

[@rkpetry]

[01:05] becomes confused as to which delta is a derivative, and whether wasted energy is amount or change... 2. What became of the 1980's research into unducted fans (UDF) and 3. why didn't they use propeller/fan-tips (like wingtips)...?

[@SnowfeetUS]

1:16 "dreg"

[@snowcie]

Goddamnit hahahaha

[@mihailazar2487]

b-but now that you said that i can't unhear it ... before reading your coment i heard drag ... but now i hear dreg everytime .... WTF ?

[@theultimateprogrammer6932]

NOOO it happened to me to

[@theultimateprogrammer6932]

dreg dreg dreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dregdreg dreg

[@Nugcon]

Greg

[@TheR0ry]

One of best minute physics videos in a while, really interesting, well explained and concise. But most importantly it was on a topic that isn't known about very widely.

[@emperorSbraz]

when in doubt though, remember to always add moar boosters.

[@CakezEdits]

+sbraz and if its too wobbly just smack a few more wings on it

[@zuthalsoraniz6764]

+LeagueOfCakez And if it behaves like a wet noodle, add struts.

[@captainheat2314]

Fuck jet engines we have infinite fuel so we are gonna use rocket engines!

[@DoctorX149]

+Zuthal Soraniz Yup. Try simple planes today, I think you've got the basics down.

[@augczr]

I was trying to follow the equations on the rough estimate (01:25) and I could understand most of it, but I still have some questions... can anybody help? 1) where does that ∆v come from? On the "Efficiency: ∆v = [...]" 2) sometimes a pure v is mentioned. What is that exactly, initial velocity? 3) why did they choose to use "1 sec" rather than t to refer to time? Number 1 is the question that bugs me the most though

[@moritzl7065]

That image at 1:32 made me laugh for 2 minutes straight. P.S. Why is audible sponsoring pretty much every KZbin channel now?

[@faphanachet1430]

Yay! Another Ender's Game fan. This like my favourite book of all time. Some random quotes off the top of my head: "I’ve watched through his eyes, I’ve listened through his ears, and I tell you he’s the one. Or as close to the one as we're going to get." “I'm putting you in Dink Meeker's toon. From now on, as far as you're concerned, Dink Meeker is God." "Then who are you?" "The personnel officer who hired God.” “He could see Bonzo's anger growing hot. Hot anger was bad. Ender's anger was cold, and he could use it. Bonzo's was hot, and so it used him. ” "For Ender, I burn candles on his birthday, but for Peter, I fulfill his dreams" "Salaam" "Alas it is not to be" “I also remembered that you were beautiful." "Memory does play tricks on us." "No. Your face is the same, but I don't remember what beautiful means anymore.” "Sometimes lies were more dependable than the truth." "Early to bed and early to rise makes a man stupid and blind in the eyes" "I've lived so long with pain, I wouldn't know what to do without it" "You don't understand" he said "Yes i do" "No you don't. I don't want to beat Peter" "Then what do you want?" "I want him to love me”

[@blackattack1840]

It just dawned on me that this series was influenced by the Blue's Clues notebook segments. Just listen to that music.

[@memberberry5860]

+Anthony Pendley my god I just had that same realization as well xD

[@galaga2416]

Piss.

[@flyhighpizzapie]

Cashing in on the 2 minute videos which 1/4 consist of a sponsor message. GREAT! If any other type of channel did this they would be hated on to no end.

[@-yttrium-1187]

Good explane-ation Planely the best video Jet!

[@jakemiller4291]

Bah-dum-tss 😂

[@stephanvelines7006]

Additionally the size of the fan is limited by the centrifugal and rotational forces on fan blades (both normal stresses and bending stresses). Furthermore, longer fan blade tips can reach supersonic speeds at the tips, leading to shocks and flow separation. Of course innovations in blade materials and design can push these boundaries.

[@Ag8MrE]

How is a "pure jet engine" (as used for fighter jets) different from a rocket engine? Is the difference that rockets carry an oxidiser?

[@nathanchetram287]

Basically, yes.

[@techmage89]

+Ag8MrE A jet engine typically has a compressor to compress ambient air as oxidizer, as opposed to pre-compressed oxidizer. The compressor is generally driven by a turbine connected to the exhaust, only without a fan that bypasses the combustion chamber (as in a turbofan). Even fighter jets these days generally use turbofan engines, albeit much more biased towards the jet than the fan compared to airliners.

[@ironcito1101]

Typically, fighters use low-bypass turbofans, most likely due to size restrictions, while airliners use increasingly-higher-bypass turbofans.

[@devilsoffspring5519]

Fighters use low-bypass, high-pressure turbofans, because the high fan pressure makes them suitable for use with afterburners, allowing very high thrust for their size and weight, but still allowing good fuel economy below the speed of sound when not afterburning. Passenger jets use high bypass, low-pressure engines because of their very high fuel efficiency. Per passenger, modern-day airliners burn about the same amount of fuel per unit of distance traveled as a subcompact economy car--and they do it while travelling 8 to 10 times as fast!

[@Richard.Andersson]

I really liked the derivation of the formula at the end. I assume that this is a well known equation within the aeronautics field? Can you recommend any other video or textbook where the design of an engine in terms of efficiency is discussed in greater detail?

[@Ninterd2]

That plane with an engine belly looks adorable. I'd have it as a pet in the future.

[@tinglydingle]

+Ninterd2 There was a real Italian plane before WWII that looked like that called the Stipa-Caproni. It wasn't jet powered though.

[@anthonihaus]

yes :3

[@dondangler2458]

Wow, I came to this channel to boost my understanding of just how quantum mechanics plays into our everyday lives, and what it means for the future of technology. This channel is highly educational and I recommend watching every video.

[@Mackeye_]

1:24 thats a very rough estimate.

[@vapenation7061]

Ikr haha

[@LongNguyen-pv9sm]

well, it would take forever to write it out, and it not too big of an estimate anyway

[@General12th]

It is, actually.

[@ZipperOfficial]

It has the Approximation symbol written within the actual equation. So.... ya...

[@modelmanjohn]

If they ever made a plane like the last one you drew, I'd fly on that, no problem. So cool.

[@matthewadams3565]

I kinda laughed a little bit at the point when he said "kinda like using a machine gun to propel your car"

[@mulymule12]

watching stuff about stuff you already know in great detail and is in fact my career, yet still enjoyable to watch.

[@rancidmarshmallow4468]

1:14 Is that a nod to xkcd? what-if.xkcd.com/21/ (Scroll down to just above the end.)

[@TlalocTemporal]

+TheRancidMarshmallow -- I'd say yes, but guns have been used as rocket analogues far before XKCD.

[@drmaudio]

Yup, we usually refer to that as "Bypass Ratio." The amount of air driven by the fan relative to the amount driven by the core. High bypass engines (sometimes as high as 10:1) are much more fuel efficient and quieter, while low bypass engines (nothing really uses a pure-jet anymore, but jet fighters can have bypass ratios as low as 0.3:1) generally have a better thrust to weight ratio, making the more suitable for applications where performance trumps economy and range.

[@MrWhataboss23]

I never asked myself that question in my life

[@PrincipalAgents]

1) "As you may have heard"

[@roshankeni2]

KZbin. sponsored by audible.com

[@kishc4509]

+roshan keni Glad I'm not the only one to have noticed! However, I've fallen victim to their marketing - currently on the Audible free trial xD

[@Xenro66]

+Kishan Chandrakumar What's it actually like? I've never listen to an audio book, and I don't really like books in general. Is it even useful?

[@kishc4509]

Xenro66 I think you'll enjoy Audible if you don't like reading! It's great for me since I commute, and you can listen while doing menial work eg washing up/driving, so don't need to set any time aside for reading alone. Currently I'm reading a book called "the power of habit" which is really relevant in my life right now so I enjoy it - you just need to find a book you'll enjoy, really. It is, however, £8/month...

[@razveck]

+Xenro66 Listen to this video but don't look at it. Just the audio. Did you like it? If so, you'll like audiobooks.

[@Xenro66]

Kishan Chandrakumar Only issue is there's nowhere in the day that I can comfortably sit down and listen to an audio book. I don't commute for long, I can't exactly listen while in classes, and at home, I have youtube! xD. But ouch, 8 quid a month, that's damn well expensive. razveck Hmm, it's not that simple for me. I rely heavily on visuals to get immersed in a story.

[@justinwong9182]

always love these short clips of actually interesting topics

[@azlan194]

Also you forgot to mention the bigger the engine the bigger the propeller, and the bigger the propeller the faster the tip of the propeller will spin up to a point it will reach a sonic boom which is very detrimental.

[@Jet-Pack]

+dontknowdontcare The fan blades already are supersonic at the tip I think. Thats what they told us at the university anyways -

[@miguellopez3392]

they are already super sonic but a company just resent ly figured out how to have the fans run slower to reduce fuel consumption.

[@koenmeier8553]

+Miguel lopez airlines already fly with fuel consumption in mind the winglets on b737 reduce fuel about 4% per flight but a massive cost reduction. They use cost index to determine speed zero means save fuel while 300 means burn alot because we are experciencing strong winds.

[@bejoypradeep]

Captain: Unfortunately some birdies got sucked into the engine Flight attendants will be coming around with complimentary appetizers

[@bryanwan6169]

1:25 when physicists take a rough estimate

[@garyermann]

+Cryp Tic Yeah, fluid dynamics is really complicated, especially when you're talking about compressible fluids like air. Almost any calculation you perform would involve making some assumptions that simplify the problem from the real world solution. The fact that the calculations even fit on a single frame of the video means this is a very simple and rough estimate with a lot of assumptions. The trick is knowing the right assumptions to make the calculation manageable while still being accurate. That, or knowing the right computer software to model the problem, which in itself takes a good deal of experience. Really, that's true for a lot of physics and engineering sciences in general.

[@bryanwan6169]

+Gary Ermann ^^^when physicists explain things in simple terms^^^

[@acruzp]

That's a rough estimate by any engineer's standards as well. And it's not complicated at all. You can learn all the basics for this in a day.

[@fulcrum2951]

Physics.. Its usually like that

[@ЮліяГрабар-м4г]

I really i fell in love with your channel. Thank you for doing such a great job by making these videos!

[@0Raik]

Bigger is better, up to a point. You don't want to tear her love place in two.

[@Stinkmeaner420]

to 10000000000000000 decimal places.

[@yousorooo]

+Raik That's what she said

[@naeagle1285]

@@yousorooo he*

[@mr2octavio]

great video, short fun and with lot of information that I won't probably use in my life haha, good job!

[@raykent3211]

4 metres is only optimal at a certain rotational speed. In the general case larger, slower rotating propellors produce less turbulence and are more energy efficient. I think the treatment here is specifically to do with jet turbines, which prefer to turn fast. It doesn't apply to other motors.

[@Foxfool228]

+Ray Kent I would expect that this video oversimplifies things a bit :)

[@Rdifycuvi]

Can we get an explanation/source of the first two equations you used at 1:22 ? deltaP = ? deltaKA = ?

[@power-max]

That last plane looks like kirby eating something sorta kinda! :D

[@MasterMario14]

+Power Max New copy ability confirmed? :D

[@vinodkumar-wm3oq]

I have a question - aeroplanes fly at high altitudes where air is thiner so that they can reduce the drag force but they also require the air to be denser so that the wings(airfoils) produce enough lift. So is there any special hight in our atmosphere where flying aeroplanes is the most efficient or where the most aeroplanes do fly for efficiency?

[@541er]

I want to point out that the Airbus A350 only has 2 engines while the Boeing 747 has 4. This is why the A350 has bigger engines than the new 747. If the A350 is powered by 4 engines, like the A340, it will have smaller engines than the 747.

[@BikashJena2304]

Awesome video, as always Good Work Henry!

[@xINVISIGOTHx]

jets are really cool :)

[@bobbysanchez6308]

1:23 Can someone tell me what each of the variables represent and why those formulae are correct, please?

[@ChaimLeibHalbert]

I'm trying to figure it out too. Here's what I've got so far: Let's make sense of the first equation. In it, we calculate the net change in momentum (∆p) due to the airflow of the engine: ∆p = (ρAv * 1 sec * ∆v) - (1/2*ρ*C_d*Av^2) It appears this is based off of this equation: ∑F = Thrust - Drag ∑F = T - D Since the technical definition of Force is not the familiar F=ma, but actually F = ∆p/∆t, we can multiply through by ∆t: ∑F∆t = T∆t - D∆t ∆p = ∆p_T - ∆p_D ∆p = ∆(momentum due to thrust) - ∆(momentum due to drag) So, the first half of the first equation will be the momentum due to thrust: ∆p_T = ρAv * 1 sec * ∆v Our variables are: ∆p_t: change in momentum due to thrust ρ: (Greek letter rho) density of air, kg/m^3 A: surface area of engine inlet, m^2 v: airspeed, m/s ∆v: change in incoming airspeed due to thrust To break down this part: ∆p_T = ρAv * 1 sec * ∆v ρA = density of air in one dimension, along the velocity vector, in kg/m. Multiply by distance to get mass of the air in kg. v*1 sec = distance air moves in 1 sec, in m. So, the mass of the air moved in one second is m_air = ρA*(v*1 sec) Since we sped it up by ∆v, our momentum is ∆p_T = m_air * ∆v ∆p_T = (ρAv * 1 sec) * ∆v All right! Now for drag. The change in momentum due to drag was: ∆p_D = 1/2*ρ*C_d*Av^2 I'm guessing that C_d is some sort of drag coefficient. This will depend on the relative size of the engine inlet and outlet, the dead area around the turbofan, and other things. I'm not an aerospace engineer, so I dunno. To derive ∆p_D, let's talk about force again. The drag force is: D = ∆p_D / ∆t (from the definition of force: F = ∆p/∆t) D = ∆(m_D_air*v_D)/∆t D = m_D_air*v_D/∆t Note that the drag speed of the air v_D are NOT the same as we used for thrust. Since this is drag, this means still air is hitting the engine and getting sped up to a speed v_D, which is some fraction of the aircraft's airspeed v, before getting knocked out of the way. We'll call this unit-less fraction K, so the drag air speed is: v_D = Kv Actually, the amount of air getting knocked away from the active zone of the engine m_D_air is also not the same as the mass of the air entering the active zone m_air. But, it is proportional to the size of the engine inlet just like m_air, so let's absorb that into our unit-less factor K, too. Since K is our own little constant, it's ok to change it: v_D = Kv (not using this anymore) m_D_air * v_D = Kvm_air (redefined K) Back to drag: D = (m_D_air * v_D)/∆t D = Kvm_air/∆t What's m_air? We calculated this above as m_air = ρA*(v*1 sec) Let's just say our ∆t was 1 sec all along: m_air = ρA*(v*∆t) D = (m_air) * Kv/∆t D = [ρA*(v*∆t)] * Kv/∆t D = KρAv^2 To get back to drag momentum, multiply through by ∆t(=1 sec): D∆t = ∆p_D ∆p_D = KρAv^2 * ∆t ∆p_D = (K∆t) * ρAv^2 From the video, we had: ∆p_D = 1/2*ρ*C_d*Av^2 ∆p_D = (C_d/2) * ρAv^2 So the mysterious drag coefficient is: C_d = 2(K∆t) C_d = K*2 secs Not sure why the 1/2 and hence the 2 secs, but hey. The units match!

[@ChaimLeibHalbert]

Hi @MinutePhysics, just looked up Drag coefficient on Wikipedia. Looks like I found an error in the video; C_d is supposed to have no units. I think you forgot to add a * 1 sec at the end of the first equation.

[@TangToms]

I think the last one with big "X" on the last slid might work! at 1:30

[@Raveman540]

+Jianyue Tang Yeah, I see nothing wrong with that design.

[@TangToms]

+Da_NKP it might need a larger fuel tank

[@Raveman540]

+Jianyue Tang entirely fair, as well as larger wings.

[@noble00006]

A jet fighter version of that already exists and has existed since 1946. Look up the Mig-9.

[@Raveman540]

Basically, but it wasn't big enough. We're talking something around the size of, say, an AirBus 320.

[@chromemaster3519]

Guys I can attest to that ad. If there is one book you should read in your whole life it should probably be a physics book but if there is another book it should really be Ender's Game. It's the best Sci-Fi in town and I've read Hubbard, Asimov, Clarke, Heinlein, Wells, Orwell and Gibson and Dick.... and .... and ... While you're at it read his fantasy too. The lost gate is the best accounting of any mythology I've ever heard. And if you're into audio books go into this forgetting any other audio you've ever heard. This is ten times better. Top tier.

[@alekmoth]

"As I might have heard?" Only like seventeen billion times. I love Audible. I use their product, in fact I have been a subscriber for years. I also love the fact that they pay for much of my online content through their advertisement. But comes to a point where I am soooooo friggin sick of hearing the same ad time and time again. And what if I DO what to support this youtube channel or podcast? I can't follow their merchant link to sign up, because I already am signed up. And if I wasnt, I would still be only able to support one of the dozens of creators that I like that are supported by Audible. I dont know if there is a solution, maybe audible is the only one willing to support creators, or maybe they just are the only ones with really good taste (aka same as mine)...

[@Infinit3Enigma]

Those equations though!!! Took me back to my vehicle performance lectures. Oh how fun that was!

[@McRocket]

Very interesting. I was wondering why commercial jet engines were getting fatter and fatter. Now - apparently - I know why. Thanks.

[@future62]

Do you have a link to the derivation of that ideal diameter formula.... looks pretty cool

[@luvjzx100]

the last plane looks cute for some reason lol

[@CesarElizarbe]

I had forgotten how awesome your channel was.

[@vaibhavjain3998]

has anyone noticed that in this video there is no pen....!! i

[@tamaratardos725]

omg i didnt

[@vaibhavjain3998]

+Tamara the Sloth dont worry... notice it next time...

[@tamaratardos725]

+Vaibhav Jain ok

[@vaibhavjain3998]

+Tamara the Sloth thumbs up....!! ;-);-);-)

[@1101]

wow. i didnt too

[@salmansaleem505]

Amazing content! explains a lot in small amount of time, other youtubers would lengthen the video to 10:00 just to get extra money

[@alexquacksal0t]

That very last drawing XD

[@Drestanto]

Can you make a video about the last part 1:24 ? Or at least a shareable explanation? It is interesting but I don't get the most part of it.

[@micmastodon]

plus the engines have gotten so reliable they can get away with 2 instead of 4

[@hardaynal5318]

Thank you man I love explanation videos with these type of art

[@scottrc5776]

Its not a 'modern jet engine' it is a turbo fan. There are also turbo prop and turbo jet engines

[@Lornoor]

Someone: -Why is 4 meter the optimal engine diameter? Me, pointing at 1:23: -Because math... and physics... Which is just fancy math.

[@rwaida2418]

Thanks for the translation into Arabic .

[@isaiahm99]

1:23 being a senior in AP physics, I understood about 40% of that, but thanks for including the math! I hate it when people go "I'll spare you the math..." lol

[@DeLePlays]

I dont like the new style of not physically timelapse drawing like you used to. im sure this is easier and more efficient and ill always watch but im just not a huge fan.

[@jordanjohnson714]

You may not be a huge fan, but what about a huge engine?

[@DeLePlays]

Jordan Johnson #roasted

[@luipars]

+Jordan Johnson (Mighty Burger) You just made my day.

[@raptorjesus3894]

Did you just make that ENTIRE comment for 1 shitty wordplay?

[@Roxor128]

+Jhawk 163 If he did, he's in good company. Isaac Asimov wrote an entire short story just for a terrible pun. It's called "Shah Guido G".

[@codonbyte]

The interesting thing is that this is the exact opposite of how it works for rockets. With a rocket, you want the exhaust velocity to be as high as possible so that the propellant mass fraction can be minimized, hence why ion engines are so efficient.

[@KASASpace]

It depends. He's actually not 100% correct. Jet engines these days don't shoot out their exhaust at high speeds. Most rocket engines shoot their propellants out nearly ten times faster. The reason they're efficient is that they use the air around them. Most Isp/effective exhaust velocity data for jets is actually skewed, since Isp is impulse per kg of propellant in the vehicle. Some of the airplane's propellant is outside of the vehicle.He's right about the energy issue, though. It takes more energy to shove a small amount of mass really fast than a lot of mass really slow. The math shows it.

[@danielw9542]

1:23 A rough estimate...

[@PeterBarnes2]

Area of about 12.5 m^2, take the square root, it's about 3.53...

[@PeterBarnes2]

QuakyJunior Whenever I'm on the computer and it's late at night, I make really stupid mistakes. However, you are wrong. It's pi*(r^2) ,this is area, not circumference. I was also wrong, but you were, too. 12.5, divide by pi, take square root, get radius. Multiply by 2, get 3.9894228040143267793994605993438. Pretty close, I'd say.

[@ThirdVillarey]

Very clear explanation and illustration!

[@iamanai3004]

Ender's Game is amazing

[@Firzenick]

So how would this be affected if we wanted planes to go slower? Would they then be allowed to have even bigger fans, like that last one? Or does changing the preferred velocity not change anything in the design (seems unlikely)?

[@jackdonkey13]

Why are you asking me these questions?!

[@DerPilotMann]

I actually recently spent a week at GE Aviation with their new GE9X. 11 feet 2 inches in diameter at the blade tips! It was huge!

[@DerPilotMann]

+Ethan Education No, however I do have some photos. If you're legitimately interested I can compile then and post them

[@DerPilotMann]

+Ethan Education Sure thing. I'll forward what I'm allowed to.

[@trekyncc1071]

Like just for the Ender's Game reference.

[@kuronosan]

When I see Orson Scott Card's name mentioned anywhere, I can't not think "bigot".

[@Foxfool228]

+Gregory Sherman Doesn't change that he has written some very influential youth literature. Try to not let an author's irrelevant personal beliefs sour their contribution to literature.

[@309387421]

Yes! More Minute Engineering!!

[@matsv201]

Compare a A350 with a B747 was really a bad example.... Firstly, the B747 is marginally larger. Looking at the 747-400 compared to the A350-900, the Airbus actually got larger wing span and its only 4 meters shorter.. so yes, the 747 is larger, but only just. The A350 is actually a huge plane And the uppcoming A350-1000 will actually be longer than the 747-400. (of cause the 747-i8 is longer still, but its the 747-400 in the picture.) The issue is that B747 have 4 engines and the A350 have only 2. The thurst of the A350 engines is maximum 350kN, but for the B747-400 only 280kN. Actually the engines of the A350 is even stronger than the one of the A380. There is one additional error in the video. its over theoretical compared to the actual reality of aircraft engines. All (or almost all?) turbofan engines is direct drive engines. Because the fanblade have a maximum speed the rotation velocity most be keeped. This make it so the turbine engine have to have huge torque. The compromise to this is that the turbine engines is a loot larger than it need to be, and the fan ist still smaler than is optimal. This is why engine manufacture dont make the fan at optimal size. Because then the torque would be to much. The solution to this is of cause to introduce gearing. And there are some prototypes under development. This not only makes it so the fan can be any size (that is the optimal size for every given aircraft, but it also make it so the turbine engine can be the optimal size to.. that is a lot smaller. This will decrease the fuel consumpsion more than making the fan bigger. But the comibnation will cut the fuel consumption quite a bit.

[@jibeneyto91]

+matsv201 You're right, but this is a video for laymen and in 2 minutes. I think they did a pretty good job.

[@matsv201]

jibeneyto Well.. i would still think they should compare two aircraft of similar size. Say a A330 and a 787. Also i think the issue about geard and ungeard turbine is to important to just skip over..... .... i would think this is more a matter of that the videomakes know the theoretical background, but not the current limitations of the engines that is in service. There is a glaring whole in the video. If they know the optimal size (and it been known since the 1900-century)... why don´t they just makes the engines optimal size... This is a question that is unanswered.....And the answer is quite simple.. there is no gearing.... so they cant.

[@jibeneyto91]

You're right as before, but gearing in turbofans has not really been implemented in any aircraft. Maybe in the future it will. I don't think it's important to consider such a "new" concept in a 2-minute video.

[@matsv201]

jibeneyto No.. but it answers the question why the turbin gradaly grow, and why they don´t make it optimal from day one.

[@gl1500ctv]

Okay, anyone know if the big plane on the right at around 1:32 (the engine with wings) would work? Could you make an engine with wings that could fly, damn the efficiency? Obviously you'd need somewhere to put fuel, as the wings don't look like there's enough room for wing tanks. Neat idea.

[@Prometheus2508]

+Stephen Furr Yes, and some jet aircraft, largely early ones, do do this. You're sacrificing top speed and aerodynamics greatly, though.

[@Bejitabro]

But that fatty plane looks cool...

[@jwhyte67]

0:17, describes a turbofan jet engine which has all the 'bypass' air going around the jet core as opposed to a turbojet in which all of the air goes through the jet core and turbine itself.

[@sadmanh0]

I kinda wanna see that last plane with a ridiculously big engine lol

[@Iamtheguyuhate]

build it hahah 😂😂

[@minhkhangtran6948]

+sadman hoque Second that.

[@minhkhangtran6948]

What you just said is called a Baka, a kamikaze plane just like it name (idiot)

[@sadmanh0]

moomoomoomoo .moomoomoo interesting, but perhaps that plane just had a really high engine size to passenger space ratio but the actual size of engine wasn't that big? Like in the interest of having a fuel efficient long range airplane with a tiny seating place to save weight.