How Could a 747 Fly Around Jupiter? - Deep Space Questions

[@longshot7601]

Listening to Scott ask "How long is your rocket?" had me in stitches.

[@whophd]

Avoid zipper accidents: FLY SAFE

[@LikeOnATree]

😂😂😂

[@danlock1]

Levi's button-fly 501 jeans: fewer stitches potentially required

[@longshot7601]

@@whophd Levi button flies have an inherent problem when putting them on straight out of the dryer. Ask me how I know. 😲

[@fluuufffffy1514]

Yum yum

[@BradDavis_vr]

The 747 on Jupiter is starting to sound more like a submarine than a plane.

[@AverageAlien]

Pretty much yeah. You go deep enough, you're basically going through a liquid

[@TheNecropolis20]

it could be a submarine that collects from jupiter and burns Hydrogen for fuel.

[@davidaugustofc2574]

These Carbon Fiber subs are getting out of hand man

[@AverageAlien]

@@low-lee cringe

[@mathewritchie]

@@davidaugustofc2574 make it out of metal.

[@NeonVisual]

A plane crash on Earth is bad enough, but slowly being crushed to death by the atmospheric pressure of Jupiter on the glide down is nasty

[@RCAvhstape]

@@221b-l3t At least submarines can surface. A 747 cannot "surface" and escape Jupiter, it must fly forever.

[@221b-l3t]

@@RCAvhstape No I mean like the Tresher, a submarine going down approaching crush depth.

[@GenuineBucket]

Would the plane not float at some point? They float in water, so presumably at least at that density of atmosphere it would stop descending.

[@JoshuaC923]

@@221b-l3texactly what i thought

[@ChemEDan]

@@GenuineBucket If it's maintained by internal pressure, the air inside has a molecular weight and would be heavier at any pressure. If it gets crushed the volume decreases which increases density. If it breaks open, it will be flooded with extra mass from outside. If it melts / sublimes from the heat, the droplets, particulates, and offgasses will also be heavier than the hydrogen. One of those things will definitely happen - even initially gaseous helium ends up getting transported to the core as rain.

[@Zeinzu2]

The 747 was such a good question!!! I want more of these "what if" questions. Keep it coming chat!!!!

[@dat_chip]

That one was my favorite too!

[@TedMan55]

i would listen to an aeronautical engineer answer just that question for an hour

[@alanstrathern]

I skipped straight to this question

[@MAGGOT_VOMIT]

400hrs eh?? Count me out. There's only so many "Hell Yeah!!" Ramones songs out there to enjoy, while pulling G's and skipping across the Jovian atmosphere. I mean, you can only rock-out and bite stuff so many times in 400hrs, before it gets redundant. 😳😵‍💫😂

[@Zeinzu2]

@@MAGGOT_VOMIT I’ll meet you in the middle. Ramones the whole flight!! Buuuuut I’d be there for the long haul!!

[@yourfriendlyneighborhoodwe5215]

4:58 osaker spotted!

[@Hezy]

I was invited to dinner with Scott last summer, let me just say I understood about 30% of the conversation but it was super fun. Still watching your videos Scott 🤙

[@dakotasloan1]

Another consideration that I thought of for Dragon detaching the trunk before the deorbit burn would be in case the trunk fails to separate. If the capsule is already on its deorbit trajectory and something goes wrong with separating the trunk, there's only a finite amount of time before entry interface to diagnose and jettison, otherwise re-entering with the trunk would probably doom the capsule.

[@HiyuMarten]

*definitely doom the capsule. Vehicle would reorient nose-first and burn up. I’d guess this is actually the primary reason for separating it before burn.

[@DenisLupakhin]

This actually happened to one of the Soyuz missions. Hard landing, but the cosmonaut survived. en.m.wikipedia.org/wiki/Soyuz_5

[@RCAvhstape]

Yes, this is mission design. Before a mission is flown the planners have to work out things like this to ensure that in the case of contingencies there are fallback options. There's an old but great movie called "Marooned" about an Apollo CSM that gets stranded in orbit while returning from a space station because the service module's main engine fails to ignite. It's a great movie but it always bugged me that the fictional mission designers didn't budget enough propellant for the RCS jets to allow for the crew to use them for deorbit or to return to the space station and await rescue.

[@StevePemberton2]

They actually had a couple of close calls with Soyuz because of that. Including TMA-11 in 2008 with Peggy Whitson on board, which resulted in a ballistic reentry because the software is programmed to go into that as a failsafe mode in case of separation problems. A really harrowing account is Soyuz 5 in 1969. It started reentering nose first just as @HIYU indicated. Fortunately the straps holding the modules together burned through just prior to the hatch melting, and the descent module reoriented itself.

[@Br3ttM]

@@HiyuMarten I've had that happen a number of times in KSP due to unusual designs, generally when making a ship out of small parts that carries multiple crew, having a lower density passenger module below a higher density capsule, which is a similar mass distribution and shape to a capsule and service module.

[@LuftKrigare]

There is nothing like a C-5A’s engine sound because of this. I could hear it and identify instantly. This from an old crew chief. Love it!

[@johncnorris]

I had the pleasure of standing on the edge of the flight line when a C-5A pulled in to park. I assumed it would taxi by me but instead it pulled a hard left hand turn and I caught the exhaust end of the engines ( plus a ton of sand ). I still wonder if the pilot really needed to goose the engines near the end or if there was some kind of bet that he could knock me off my feet.

[@nocturnalmayhem0]

we had a few c17s fly over my work place last week and they were insane. like i didnt think theyd be that loud. shook the building and set off car alarms were like a half mile off the end of the run way at CLT where the national gaurd cargo wing flies out of.

[@johncnorris]

@@nocturnalmayhem0 - The fighter jets are very exciting but watching big cargo planes takeoff from one runway and immediately bank to land on the crossing runway really freaked me out. (Dover AFB) They look like they are simply hanging in the air with nothing but magic!

[@rwboa22]

Same here, except when fishing with my dad (a Vietnam veteran in the Army) in Delaware near Dover AFB.

[@Prophes0r]

@@nocturnalmayhem0 Jet engines and guns are two things for which the media have given "civvies" a hugely distorted idea of loudness. It was always fun to watch the error-rate on spinning-disk drives jump up every time an alert-pilot took off with full after-burner. Note: All fighter pilots are assholes and they can get away with breaking the rules. The system weeds out anyone who isn't willing to out-dick the competition for the right to pilot the flying-race-car. Trying to get them to do ANYTHING that doesn't involve them getting another "fix" of flying is literally a full-time job.

[@TrickyClaw]

Fly safe Scott!

[@duran9664]

On Jupiter 🤪

[@windowboy]

YLF EFAS

[@somethinggeeky]

Can confirm the buzz saw sound. I live right by the end of a runway. Always wondered what that buzzing sound was that preceded the boom of the jet going overhead. Now I know.👍

[@Lucius_Chiaraviglio]

Definitely not only audible, but VERY LOUD to the passengers on some planes, especially ones that were commonly used in the 1980s and 1990s.

[@iitzfizz]

@@Lucius_Chiaraviglio The CFM-56 make this sound, very loud on take off.

[@vbscript2]

@@iitzfizz Most big turbofans do. One that notably does not is the new Pratt GTF, since the gear reduction allows the fan to spin slower than the N1 spool.

[@rtqii]

In his book, Skunk Works, by Ben Rich, he talks in detail about jet engine intake designs. He did the SR-71 intakes. The Pratt & Whitney J58 engines had an "unstart" problem that caused violent changes in the supersonic airflow.

[@nmccw3245]

Excellent read. Highly recommended. 👍🏻

[@NeroontheGoon]

Yes, the unstart, a complete loss of compressor gas path bleed control.

[@Heisenberg2A]

The cones cause the air to go subsonic at the engine inlet by compressing it. I read this book, it was awesome. I think unstart was a failure of this system to react to quick engine/environment changes.

[@NeroontheGoon]

@@Heisenberg2A Actually, the cones on the inlets of the J-58’s capture the shock wave before it can enter the inlets and disrupt the airflow into the compressor. Capturing the shock wave in this manner was an extraordinary way the engineers at Lockheed and Pratt&Whitney used the properties of the shock cone to slow the incoming air into the engine inlet to below supersonic. Doing this, and with Bernoulli’s principle, as the airflow velocity decreased, it’s pressure rose. This had to be accomplished in 6’8” from inlet lip to the inlet guide vanes of the compressor, some damn fine engineering. The J-58 was a dual cycle turbo ramjet engine as the speed of the aircraft caused a transition in engine operation between Mach 2 and Mach 3.2, pure turbojet to almost pure ramjet. Mr. Johnson explained that above Mach 2.75 and change, the inlets were actually doing all of the work. At Beale Air Force base in California, we used to watch the J-58 run in the test cell in afterburner and it would get so hot you could actually see the shadows of the internal turbine frame through the incandescent turbine case and afterburner section. If one word were used to describe the J-58, then the word ‘BEAST’ would be most appropriate.

[@bertblankenstein3738]

Yep, the sr71 engines had variable geometry to deal with the airflow. It would be a good case studio.

[@jimsvideos7201]

The intermediate and high pressure spools on engines so equipped might well appear to have blade tips that are very highly supersonic, but keep in mind the increase in the speed of sound with temperature; at 1500 celsius it's about 2.5 times faster than it is at 20 C.

[@General12th]

That's a really interesting point, actually.

[@geraldhenrickson7472]

I like it!. Yet does the speed of sound decrease in the presence of higher pressure? Perhaps it is a wash? This is all making my head hurt.

[@jimsvideos7201]

@@geraldhenrickson7472 The speed of sound varies only with temperature, but temperature does vary with altitude. Lower temperature does mean you can add more heat (up to a given maximum temperature somewhere in the engine) which is why there have been high-performance versions of some airliners for hot or high airfields.

[@SeanCMonahan]

​@@jimsvideos7201 my gut reaction to your comment was _there's no way air pressure doesn't affect the speed of sound_ ! But then I looked it up, and sure enough, air pressure has negligible affect on the speed of sound! Learning something new every day.

[@oldfrend]

@@SeanCMonahan that's surprising cuz i know the speed of sound goes *up* with density. that's why it's much higher in water than in air, like six times higher.

[@SecularMentat]

Your talk of the intakes reminded me of the variable geometries of the intake of the Pratt and Whitney J58 of the SR-71 blackbird. It has to move the cone around to maintain airflow while protecting from shockwaves. I can't wait for a Scott Manley special on this discussion.

[@221b-l3t]

I don't know if using the Hindenburg as a symbol for hydrogen is appropriate but I laughed pretty hard.

[@iitzfizz]

I did nazi that one coming!

[@bugturd00]

Too soon?

[@Flesh_Wizard]

​@@iitzfizz it hitlered me too hard

[@baconcleaner]

4:55 OH MY GAH!

[@iowa_don]

When I was working at AiResearch/Garrett, I designed a 9:1 centrifugal compressor that had a relative Mach Number at the inlet tip of 1.25. Also at the exit of the compressor impeller the average Mach Number is above one and the vaneless space ( between the impeller exit and the vaned diffuser leading edge) is used to get the exit Mach Number below 1 before the air goes into the vaned diffuser.

[@sidv4615]

wow, I did not understand anything that you said. Still, wow amazing

[@paulschulte1064]

My turbine experience was with steam turbines. I was working on a small 1,500 horsepower GE turbine, under the supervision of a GE engineer I asked him if the airfoil shape of the buckets meant that the steam path passing over the top of the bucket meant that there was lift being imparted to the bucket. (buckets in some circles might be called “blades” but the term comes from the fact that turbines were preceded by water wheels) He got all excited and was glad to be asked such a question and went off on a long dissertation about steam turbines. It is interesting that the inlet steam might be as hot at 1200 degrees at over 2000 PSI and on a power plant turbine the inside diameter of the delivery pipe might be a foot or better. By the time the steam reaches the condenser it might be a partial vacuum. All within a distance of a few yards on a large turbine. Moral of the story, learn from whom ever you can whenever you can.

[@ecnivo]

What? I can't hear you over the TPE331

[@MarkiusFox]

@@paulschulte1064 It's cute getting an engineer excited.

[@RCAvhstape]

@@paulschulte1064 So what was the answer? Is there lift being generated?

[@MistSoalar]

747 on Jupiter is such a wonderful thought experiment! Thanks for taking that question (and Darryl for posting the Q as well)

[@ibxgameryt9449]

How about Venus??

[@djrbaker1]

I love the noise jet engines make during takeoff when youre sitting in front of the wings. The 737 NG sounds the best.

[@manojjagan5514]

Thanks

[@tarmaque]

You could literally do a whole series on jet engines and the various permutations of them, from centrifugal compressors to axial, can versus annular burners, compressor design, injector design, and a whole host of other things. Gear boxes and generators, and why turboprops are more efficient than turbojets. For that matter, talk about the difference between turbojets and turbofans. Certainly some of us understand those differences, but not everyone.

[@QuantumHistorian]

Yes, that would be great! I'm one of those who has some idea of the vague theoretical difference between them, but absolutely no clue what it means in practice. Things I've tried to read on them online are either so superficial to be meaningless, or bury me in jargon. Scott has a knack for putting in just enough physics for everything to click into place without it feeling like a lecturer desperately trying to get students to pass an exam.

[@tarmaque]

@@QuantumHistorian Scott is pretty good at that. I'd do it myself but I can't be bothered. 🤣

[@BossSev38]

15:50 You read somewhere? It's probably What If by xkcd behind your back - The Interplanetary Cessna question

[@DanielLiNeutrinos]

Used to intern at a jet engine overhaul shop many years ago. Would love to hear more about engines and how they have changed over the years

[@richb313]

Thanks Scott for answering a varied but interesting set of questions.

[@StuSaville]

18:50 Look at the debris hitting the water, that's crazy!

[@LongPeter]

4:31 That infrared shot of the plane taxiing is pretty sweet 😏

[@dmytropetukhov325]

10:30 Water ice and organic compounds are actually reasonably plentiful in the asteroid belt. Ceres has water geysers, for instance. This could help solve the problem of organic polymer synthesis in situ. 14:20 A nuclear-powered propeller-driven aircraft would not need to haul tanks of oxidizer along, and thus would have a considerably higher endurance in the Jovian atmosphere

[@spacemanmat]

It was actually the Afghan cosmonaut that realised the clock was still running. The Russians were just relaxing waiting to be told by control what they should do. Embarrassing for them as the Afghan was really just a token that was not really supposed to contribute. The Russians also had another landing where the propulsion module failed to seperate and reentered upside down, the sole cosmonaut hung upside down watching the door glow red hot, very glad that they had used titanium for it. Fortunately at this stage the propulsion unit burnt off and the capsule self righted, but it was deep in the atmosphere and wildly off course. I believe it broke the chute and the retro rockets didn’t really do anything, it hit the ground hard enough to rip the cosmonaut out of his restraints and he knocked out a tooth but did survive. So you definitely don’t want to enter with the trunk attached.

[@davidglover3802]

That's it! BUZZ SAW perfectly describes that supersonic prop tip sound I heard the first time I was near a P-51. It was 1969 EAA convention in Rockford, Illinois, and I was fascinated by the sound and power.

[@leenux1707]

17:00 so you need a nuclear submarine with wing and electric jet engins ??

[@iitzfizz]

Never thought that the buzzsaw sound was from the fan blades reaching > Mach 1, just assumed it was reverberation or something, but makes total sense. Love the sound of the CFM-56

[@duck853]

Thought exercise 747 scenario, we can do .86 Mach comfortably. So 1000 kph is just about right on! Good job. I believe the original question was more of a distance question than a practical exercise.

[@colinsutherland8965]

Fun and informative as always Scott. Jet engine inlet pressure recovery can make a significant contribution to the overall thrust. On Concorde is was contributing something like 60% of the overall thrust at Mach 2. And on the subject of Mach numbers it's the velocity that changes with the gas composition not the Mach number LOL! Keep up the good work

[@berman00]

Since you mentioned it, I'd love to see a video on jet engines!

[@spacexrocks1041]

Phobos-Grunt was very promising. Phobos 1 & 2, were also exciting missions. Sadness x 3. Both Phobos probes carried "hopper" landers intended for Phobos. A software error resulted in the loss of Phobos 1, but Phobos 2 got so close, possibly within 50 m from the surface, but then contact was lost.

[@spacechannelfiver]

That'll be the Leather Goddesses

[@Zacktebo]

Great video Scott! Just a small correction. Afghani is the money in Afghanistan. The people are Afghan. Love everything you do!

[@ricoreyes6044]

It's cool you talked about the "Buzzsaw" sound! I'm a jet engine mechanic and I was always curious why the engine noise abruptly changes at a particular RPM, but the exact point it happens at varies day to day. Nobody I asked about it had an answer, but one day I did the math and realized it was when the blade tips would be going supersonic. It's a pretty neat fact.

[@pythonboom945]

Your description of the high bypass turbofan is right; when the RPM gets high enough on the CFM-56, I would describe it as “singing” to the younger aircrews and needing the engines to “sing” on a go around.

[@robertwagner6627]

Scott. You explain things better than anyone. Hands down. Thanks!

[@MrAnt-sf2sk]

4:54

[@KurEye2005]

Ok buddy baka

[@eckligt]

The Jovian Jumbo explanation was enlightening. I suppose there is a semantic point here: When a craft moving through a fluid is built with a pressure vessel designed to have higher pressure inside than outside, it's an aeroplane. But when it's designed to have higher pressure outside than inside, maybe that's a submarine? EDIT: I suppose a part of what makes a submarine a submarine is also that it has buoyancy, or at least that it's close enough to be buoyant that it can hover with little effort.

[@fnln-namaemyouji]

Worth pointing out that there's another attempt at the Phobos Sample Recovery concept, in Martian Moons eXploration or MMX from JAXA. It was recently delayed, as it was scheduled to launch on Japan's H3, which ran into issues, but it's still probably the closest to fulfilling that goal.l

[@annoyed707]

I expect the seatbelt sign for that Jovian flight would be on all of the time.

[@ArseneNaz]

4:54 SATA ANDAGI 🔥🍘

[@thefoodathome5333]

Now this looks like osaka

[@kevinfromspace]

The original machine has a base-plate of prefabulated aluminite, surmounted by a malleable logarithmic casing in such a way that the two main spurving bearings were in a direct line with the pentametric fan. The latter consisted simply of six hydrocoptic marzlevanes, so fitted to the ambifacient lunar waneshaft that side fumbling was effectively prevented. The main winding was of the normal lotus-o-delta type placed in panendermic semi-bovoid slots in the stator, every seventh conductor being connected by a non-reversible tremie pipe to the differential girdlespring on the "up" end of the grammeters. Moreover, whenever a forescent skor motion is required, it may also be employed in conjunction with a drawn reciprocation dingle arm, to reduce sinusoidal repleneration.”

[@kmech3rd]

That sounds like vintage Mad Magazine. Needs more Potzrebie though.

[@scottgilmour8392]

Hi Scott. Like the name, btw. You and Darryl just made my day! "Flying" a 747 in space was one of central devices used by Harry Harrison in his novel "Star Smashers of the Galaxy Rangers." Haryy is pretty much my favourite author and it's good to see his ideas receiving considered technical thought. (just skip Soylent Green, please.)

[@Solaris_Kou]

Can you give me the link for the novel please

[@paulschrum4727]

Getting the 747 /to/ Jupiter. That's the movie I want to see.

[@General12th]

And then getting it _off_ Jupiter. Unless it's meant to be the joyride of a lifetime... literally!

[@johndododoe1411]

There's a fictional story from 1977 about flying to Saturn in a jerry-rigged airplane (I don't remember if it was a jumbo). Story contains lots of satirical elements even in its "technical" descriptions, but it's a celebrated masterpiece of comic book writing and there's a 2008 movie version that keeps almost none of the story.

[@kieranh2005]

You'd have to go full Kerbal with stacked starship superheavies. Mmmmmmmmm...

[@FastSloth87]

@@kieranh2005 CHALLENGE ACCEPTED! (not really, I suck at making planes in KSP)

[@nikolatasev4948]

It's easy. Just open the cheat console. You know how to do it IRL, right?

[@oldmech619]

2:35 A fellow worker of mine was sucked into a B737 engine. Fortunately, for him, it was an older-style engine that had inlet guide vanes preventing him from being shredded. However, he lost an arm in the incident."

[@Marin3r101]

Why a (") at the end. Who are you quoting.

[@oldmech619]

@@Marin3r101 I was “quoting” myself. I wrote it out then let AI correct my grammar. I’m terribly dyslexic. AI will Save me

[@offspringfan89]

Jesus Christ man, poor guy.

[@SparkyOne549]

@@Marin3r101 Punctuation police alert!

[@QuantumHistorian]

Well, it only partially prevented him being shredded then.

[@benoitp303]

I think, for your first question, an interesting engine is the TP400 engine which powers the Airbus A400M military transport aircraft. The maximum speed for this aircraft is M0.72 just because of the speed at the edge of the propeller blades (you have to add the two vectors, aircraft speed compared to the air and propeller tip speed compared to the aircraft).

[@jurjenbos228]

I love you thinking on the 747 question. Thanks.

[@MCsCreations]

Thanks for the Q&A, Scott! 😊 Stay safe there with your family! And fly safe! 🖖😊

[@aalhard]

Deep dive on intakes. Sub, super, hyper, and stealth 👍 awesome idea 5:30

[@ttt3035]

osaker at 4:54

[@CameronJay]

This was fun Scott and thanks for continuing to say Aluminium correctly!

[@Wheretherivermeets]

Zero-G smelting sounds utterly terrifying

[@sheldoniusRex]

Handle everything inside pipes.

[@martylawson1638]

There are induction furnaces on earth that magnetically levitate the melted metal. I assume this would be lots easier to do this in Zero-G.

[@jessepollard7132]

depends on the implementation - very likely to be done in long tubes to allow the collection of the oxygen released.

[@baldisbasiceducationandlea6708]

Osaka at 4:54

[@bobsmith6768]

For the Dragon, I would have thought that you want to detach the trunk before the burn to avoid the possibility that it fails to detach after the burn and the dragon can’t re-enter safely with the trunk attached.

[@carlatteniese2]

Absitifascinatingly Posilutely amazing! Scott Dude! I had nooo idea! (repeated sound barrier pressure concussions making the buzz saw sound)!

[@doghouse6413]

“Now works as an accountant in Germany” must be the most random and awesome thing I’ve ever heard

[@Mtlmshr]

As Felix would say “You Rock” way to go Scott!

[@kaelon9170]

14:36 tip for the future: Most Jet airliners have their cruise speed somewhere between Mach 0.78 and 0.85. And while there are aircraft that can reach higher speeds (i.e. the Boeing 787 is certified for Mach 0.90), this is generally avoided because at mach 0.86 and higher air turbulence starts making the plane's fuselage and wings less aerodynamic, significantly increasing fuel burn.

[@FectacularSpail]

Imagine being an accountant in Germany, and you're commiserating with your coworkers about random day to day usual workplace bs, and the Afghani guy just laughs, like "Oh, you think THIS is bad?"

[@saumyacow4435]

Scott, just on that issue of landing a probe on Olympus Mons. It is entirely feasible to do this fully propulsively. Also, Olympus Mons is one place you're not going to use a parachute. A fully propulsive lander that will land anywhere on Mars surface (starting from low Mars orbit) will have a propellant mass fraction of about 0.75. That's a full 5 km/s of delta-v capability using methalox - and in most cases you actually need around 4 km/s to land on Mars from Mars orbit. That is, fully propulsively. If it's a probe then you can stage it with a small return vehicle that can also pick up a propulsion stage in orbit before returning to Earth. And of course you can use aerocapture/aerobraking to get into Mars orbit in the first place (we assume it's unmanned). The scenario is a perfect example of why we should have this capability and not simply presume that every landing on Mars must require high speeds, high heat loads and parachutes. And I'm also pointing this out because few people realise that the ideal human landing on Mars is via a fully propulsive (and reusable) crew-only lander and ascent vehicle. Such a vehicle would have the advantage of subjecting the crew to far lower g forces, would be safer for several reasons, and would have other benefits like not shedding parts and parachutes in a way that might endanger previously landed people/hardware.

[@spacexrocks1041]

Thank you. I was thinking of descent from orbit (Viking), but I think the answer assumed direct descent, which has been used for US rovers, and requires a parachute. But descent from orbit is different in several ways. Slower speed: Pathfinder (direct descent) entered the atmosphere at 7.3 km/s; Viking (orbital descent) entered at 4.5 km/s. Fuel: No need for a parachute for a caldera lander. The parachute had a mass of 110 lbs. on Viking, which had 187 lbs. fuel. That's a lot of fuel. Sample mission: requires less fuel for ascent stage, because the 22 km makes it like an "air launch", and there's less atmospheric friction at that height. I haven't done the numbers, but there a lot of trade-offs for a caldera landing & sample return.

[@saumyacow4435]

@@spacexrocks1041 If all you're doing is building an expendable descent stage for a robotic mission (and it carries a small ascent stage for sample return) then I'd propose doing something that would make sense for one-way cargo delivery (in support of human missions). Again, no ejected parts and no parachute. Instead, start from low orbit and use a (relatively light) hybrid heat shield, through which your landing engines can fire. What I'm speculating on is some form of porous material (carbon foam?) through which flows liquid methane. The nice thing about methane is that it has a heat capacity that gets a lot higher as it gets hotter - eventually dissociating. It would also keep the nozzles of the landing engines cool since they could again see a flow of cold methane. The relatively light heat shield means you don't need to eject and not having a parachute means you're reducing the risk of contamination. Perfect for bio-sampling and also perfect for landings in difficult locations. I note that Perseverance is now having to deal with bits of degraded man made materials that are complicating its ability to get pristine samples.

[@friendlyfire7861]

I never knew that about the buzz saw sound! It always sounded to me like there was something wrong.

[@pat8988]

Regarding the question about fan speeds exceeding the speed of sound, P&W makes an engine series called the GTF (geared turbo fan). Said to be more efficient due to the slower speed of the big forward fan. Probably quieter too.

[@HalNordmann]

For the Mars atmosphere sample, there has been a proposal for that. Though aimed mainly at the atmosphere itself, not lofted surface material

[@erictheepic5019]

I could've sworn Roger Wiens mentioned such a mission proposal in his book, Red Rover, but I couldn't find mention after a precursory skim of my copy. Perhaps it was another book, or perhaps I didn't look closely enough. Anyhow, I seem to remember the proposal as similar to what the Patreon member described, just that the sample collection mechanism would basically be a ramjet minus the jet, allowing a sample of the martial atmosphere to be collected at a decent pressure.

[@spacexrocks1041]

​ @Eric The Epic Speaking of skimming .... look for "Sample Collection for Investigation of Mars" (SCIM)

[@matsv201]

3:23 While the air may slow down a bit, that is not the main reason i become subsonic. The main reason is that the air heats up, like in a diesel engine, and when the air heats up, the speed of sound also increase, making the air subsonic despite still having a speed that would externally be super sonic

[@leeming1317]

2:40 OHHH ive heard this sound! haha I heard the old sound too, I love the nostalgia of the old ones

[@randoomain7485]

Absolutely would love a dedicated video to jet engines. I never quite understood how you gain power when they're open on both ends!

[@StevePemberton2]

Yes what happens in the combustion chamber is where it's all at, but not much is ever said about it. I suspect that's because it's a fairly complex topic, considering the task of getting all of the pressures just right so that the combustion gases push off the incoming compressed air and pass through the turbine blades, and not vice-versa. In fact when things go wrong the exhaust gases do flow the wrong way, which is known as compressor surge. Things I have read about what happens in the combustion chamber get into things called Raleigh effect and Brayton cycle. I also would like to know how fast the air is moving during combustion. Actually if I understand correctly the flame is somehow held stationary by balancing everything so that the speed of the advancing flame front is equal to the speed of the incoming air. Definitely something I would like to know more about.

[@zorbakaput8537]

The most graphic representation of the Starship take off and its effects I saw, are when you keep an eye on the beach and the surf and see how many debris splashes there are in the water as the rocket rises.

[@Keimzelle]

At 2:42, you see the very special viewing place for the passengers on Zurich's airport tour. You see the bus there, with dozens of spectators standing - and watching the plane take off. They're just 100 meters from the runway centerline. A sight and sound to behold...

[@kenhelmers2603]

Thanks Scott!

[@chouseification]

hullo, happy Sunday!

[@brindlebucker4741]

The words pique, pike, picador, and prick are all related, and yeah, a long time ago, if someone was piqued, they were angry or irritated/annoyed. But it gradually changed to a softer meaning of to excite, arouse, titillate in the sense of curiosity, interest or awareness. One of the nicer words we have inherited from French.

[@jimsvideos7201]

2:24 That's an F404 or a member of that family, and those are low-bypass turbofans.

[@bersig]

Japan's MMX mission (Martian Moons eXploration) is going to look at both Mars moons, then pick up a sample of Phobos and bring it back.

[@pedrocrb]

Nice use of 22/7

[@ThomasGabrielsen]

The iconic inlet cones (spikes) in the front of each of the engines on SR-71 is there to slow down the > Mach 3 air to subsonic air. There are some beautiful Schlieren photos that shows how the spike move the shock wave outside the inlet cowling.

[@NeroontheGoon]

Actually Scott, as a large commercial aircraft mechanic, the “fan jam” you are talking about is also a function of designed blade twist and compressor howl. Pratt &Whitney is about to release their geared turbofan engine, increasing efficiency from the fan. The acoustical dampening systems are fairly sophisticated using perforations on the exit side of the fan air duct and in turn, using the fan air to insulate hot gas path acoustics, dampening the sound

[@bruceyoung1343]

Thoroughly enjoyable

[@robertnichols2283]

As rare as gold etc. is in Earth’s crust, there are geological processes that concentrate them enough to mine profitably To precious metals in an iron-rich asteroid will (probably) be disseminated evenly Even if there’s a lot more more precious metals per unit mass in the iron-rich asteroid, lacking any geological process concentrating the precious metals, it’s quite possible that they cannot be extracted profitably

[@BogeyTheBear]

Gold's resistance to chemical reactions will undoubtedly come into play.

[@martinputz8010]

One Video on jet engines? We need a whole series!

[@JoshuaC923]

Jet engine spooling sounds so good though, especially like the Trent and Ge90 sounds

[@padders1068]

Scott! Great video as ever! Keep up the good work! 🙂🤓

[@konstantin.v]

15:54 *Why would a plane need air density when it has pressure?* Pressure is basically force. Is density required for pressure difference under and over the wing? 🤔

[@RichardBrake-fo4iw]

"Star Smashers of the Galaxy Rangers" by Harry Harrison has a 747 flying over Titan. A great parody.

[@Red..E.]

There will undoubtedly be a future space-faring team of engineers/daredevils that will come together and modify a (possibly multi)century old boeing 747 and fly it around Jupiter, just like we modify old cars/aircraft today. Congrats to that team in advance lmao.

[@glencrandall7051]

During Apollo manned launches there was a rescue team in a protected vehicle only about 300 or 400 feet from the Saturn V.

[@johndododoe1411]

Why weren't they in the escape bunker, the one that astronauts could reach by zipline from the tower?

[@RideAcrossTheRiver]

@@johndododoe1411 Time.

[@StevePemberton2]

Actually the M113 armored personnel carriers were stationed 1,800 feet from the Saturn V. Well within the 7,000 foot blast danger zone. During Shuttle launches the M113's were stationed 1.5 km from the pad (5,000 feet).

[@AllisterCaine]

@@StevePemberton2 Holy shit. An m113 is not what comes to mind when reading "protected vehicle". Never knew that. Guess it depends what kind of parts it would be hit by.

[@bmitch3020]

"How long is your rocket" 🤣 Didn't realize Scott would be dropping pickup lines like that.

[@kelvyquayo]

Phobos-Grunt was one of the few missions I did start to finish in KSP where I never needed to reload or hit debug debug to add fuel or electricity.. I fully expected to have messed up somewhere but it went perfectly…. That mission had a Phobos Lander and also a Chinese Mars Orbiter. I’d highly recommend any KSP player to try to reproduce it. It was very fun.

[@whophd]

Sucker for B-roll footage - I was entranced by that take-off clip

[@morgan0]

9:42 does mars have enough atmosphere for a basic glider? you could go in from below olympus mons at like a 90 degree angle, slowing down in the atmosphere you fly sideways thru before using the glider to go up enough to not hit the side, then use rockets to remove the last of the sideways velocity. and because you came in from the side, there would be very little velocity normal to the surface. the big issue could be with the mass of the wings, so they would either need to be very thin (maybe some plastic sheet held in place by wires from a pole sticking out normal to them towards the planet) or have strengthened solar panels that double as wings

[@jasondworkin6597]

For the second question part 1: there was a NASA mission concept called SCIM 20 years ago to collect upper atmosphere martian dust with aerogel: en.wikipedia.org/wiki/Sample_Collection_for_Investigation_of_Mars and JAXA has a Phobos sample return mission, MMX, in development en.wikipedia.org/wiki/Martian_Moons_eXploration_(MMX)

[@williampeek7943]

As far as landing on olympus mons it could be possible if the capsule with its heat shield dip down lower than the top of olympus mons into the thicker atmosphere. Say 10 kilometers. The capsule could change a lift vector and go up again losing more velocity because gravity will be pulling on the capsule slowing it down. Only then would it need to fire up engines when it reached twenty three kilometers or so. This would be a skip maneuver.

[@StevePemberton2]

The pictures at 10:36 suggests a need for a video about firing projectiles on the Moon and Mars (and smaller bodies). How far will bullets go at common muzzle velocities. How far will a Nerf cannon shoot. How far can you hit someone with a super soaker? Maybe some of this has been covered in a previous video. Is archery possible in a vacuum? Or darts?? Badminton might be awkward. But skeet shooting might be fun (and different). And while Alan Shepard made a valiant attempt, how far could an amateur golfer hit a golf ball on the Moon. How about a pro? Not forgetting Ed Mitchell, how far could an Olympic athlete throw a javelin? How about a discus? And shot put, or even better stone put. Or even much better a caber toss. And are there any sized artillery where the shooter would have to be careful not to hit themselves in the back of the head?

[@MaryAnnNytowl]

19:41 Oh, sweet! Thank you for the correction between peaked (as in pointed or reached top level) and piqued! I greatly appreciate it!

[@frankgulla2335]

Thanks, Scott. Terrific answers to interesting questions. How long do you spend preparing for those answers?

[@jonwatkins254]

For your jet engine and turboprop episode maybe you could include the Pratt geared fan and the 8 blade USN Hawkeye propeller. The eight blade choice surprised me because I would think it might have some of the undesirable low speed resonance characteristics of the 4 blade.

[@SirFloofy001]

You can hear it inside the plane as well, whenever the engines spool up for takeoff there is a secondary harmonic that starts about 1/2 throttle. You cant hear the actual shockwaves but you can hear the vibrations caused by the shockwaves. It sounds like a bass hum.

[@ryandugal]

Looking forward to jet engine video. Yay!