That reentry footage was terrific.

There’s one solution you’ve missed: Using the mega maid to remove earth’s atmosphere entirely, thus solving the problem of reentry!

That reentry video always gives me a strong sense of relief and appreciation for the safe embrace of earth. Even compared to ending up alone in the middle of the ocean, which is normally considered an exceedingly horrible and deadly situation, it's a warm, protective and comfortable bosom compared to space's sheer hostility to life.

Although I had seen it before, I appreciate you leaving the re-entry video up as you narrated. The vortex of superheated gases behind the capsule is mesmerizing.

You make watching UKposts more efficient by presenting two videos at the same time.

I feel like I'm in a capsule returning from the Moon and Scott Manley is on the intercom just rambling on and on about re-entry physics while I'm trying to enjoy this moment.

Is reentry really necessary? If I went to space, I would insist on coming back, so yes, it's necessary.

I love using the ballute mod in ksp. Shoot for a periopsis of around 56 Km, and deploy the ballute as soon as I'm in the atmosphere. It's so much more gentle landing.

There was one professor in the early days of Apollo that explained you could use rockets to overcome gravity to slowly deorbit but the amount of fuel was more than what it took to get to orbit. So, a heat shield was more efficient, less cost, less massive. His sketches showed multiple rockets pointing towards earth center and rockets slowing the spacecraft down to match earth’s rotation, then allowing the ship to slowly descend! Fuel requirement was enormous.

I want more of these refutations of common "Why dont they just do X" I love your content Scott, followed you since the early days of KSP, I remember being hyped every single time you released a "100% reusable space program" video because your solutions to things were so creative.

Talked to a person who worked on the US X-15 rocket plane program (1959-1968). They considered putting the X-15 into orbit, but none of their pilots could fly the re-entry profile on the simulator without burning up. A non pilot member of the program asked if he could try re entry on the simulator, and they let him. He succeeded, and was able to repeat the manuever again and again. Everyone wanted to know how he was able to succeed where others could not. Simple, he said, he watched the temperature guage. If the X-15 got too hot, he pulled up; when it cooled down he let the plane descend. He did this over and over, and showed that winged reentry from orbit was possible. The X-15's glide ratio was about 4 to 1. Constructed of inconel X alloy. An ablative coating was tried on the X-15, but was found to be unsatisfactory, and actually interferred with the plane's natural ability to disapate heat.

Scott, this episode was fantastic. I loved that you ran the video through your whole segment. It was a great idea and worked well. Bravo 👌

Being utterly mesmerized by the parachutes interplay at the moment of splashdown "sparked joy" in this heart. Thanks Scott.

A skipping rock on a pond is one of the best visual analogies to reentry that I ever heard. Really helped me understand and visualize it after that.

Fantastic footage and an excellent explanation for what’s going on. Thank you, Scott A bit of trivia about the L/D ratio for airliners: the B767 has 12 (they discovered it during the Gimli glider incident, go check it out), while the Airbus flock tend to have around 15 (yes, even that monstrosity known as the A380). The B747 and 777 also have around 15, while the original B737 was supposed to have 17 (highly doubt that, but hey). The B787 and B777X are at 20! Except the B767’s, which was actually found out by accident, the rest are all theoretical, so I wouldn’t count on them if were to have a total loss of power on all engines anywhere far from an airport safety cone. Gliders are on another planet. The first plastic gliders of the 1960s had around 32-35 at relatively low speeds, while more modern ones like the Nimbus 4 have a manufactured-declared L/D of 60+. Recently manufacturers have stopped publishing the “polar curve” of the gliders they make, so we don’t exactly know their design performance with the seams level of detail, but I’d guess is not very far from 50 to 55. The major improvement on previous iterations lies in the speed at which they obtain those L/D ratios, given by the much higher wing loading of modern gliders (55+ kg/sqm vs 30-35kg/sqm for the 1960s ones) Still not useful for atmospheric reentry Happy 2024

As you were talking, I was thinking about inflatable or temporary heat shields that spread out and create more surface area. I hadn't heard about that at all. It's super cool that it's already been developed and put into testing. I'm excited to see where that technology goes.

I am amazed by the 'skipping' of Orion. The calculations to figure that out are truly incredible.

I never saw that re-entry footage before - my goodness, how amazing is that?!?! Thanks for going through the details of re-entry Scott, you answered all my questions on that topic in one short, concise and easy-to-understand video.

Short answer: it keeps space clean and free of as many bodies as possible. Long answer: the amount of thrust it would take to actually bring an object back in without a _Dynamic Entry_ is roughly equivalent to half the thrust it took to put something up there but then you have to add thrust to putting the object and its return rocket up there. So for what's basically two tons of refined high-tech terracotta you can cut the price of the trip in half and look ballsy doing it.

That is one of the most complete and informative explanations I have heard on this, well done, I have wondered about the problems involved.

Congrats Scott for explaining complex thermoaerodynamics without having to display a single equation on the screen 👏🏻

Interestingly, I recently finished re-watching Mobile Suit Zeta Gundam (1986), which features inflatable heatshields for various spacecraft entering Earth's atmosphere. For a show about giant robots from the 1980s, they sure did their homework on ballutes.

Great talk! As a 1972 Aeronautical Engineer BS degree I knew the conclusions for both including the Blimp or Zeppelin solution. And even looked into it. So the lighter then air embodied rocket would float to a high atmosphere elevation with zero velocity effectively. Heating say hydrogen as the lift gas would help get higher but not significant. Then collapse the blimp as the hydrogen lift gas and LOX/LH2 is burned would save almost nothing in fuel considering you have to lift the blimp also. So going into orbit is at best a wash but floating to altitude and being in the correct spot and surviving turbulence etc. in the air is a higher risk then flying or rocketing to that starting height. Blimp would be so large that you would expend energy just to keep it from skipping or it would have to be a lift body that may actually be pushing towards the earth. Lift body means more weight and control surfaces, more weight. Trade off. And the gas inside the blimp couldn't be hydrogen or oxygen. Needs to be something that will not burn or be the oxidizer. Skylon fly to space with inflatable heat shield for reentry that is discarded or retracted to finish by flying for a landing. Now that is maybe the best combination since the large wings already need to be there to fly at a low mach number early in the climb into space.

Great video.. I have often wondered about this and this easily answers the questions that I had about it though I had pretty much already come to the same conclusions. This just presents it so well and clarifies some questions I had about confirming it. One thought that I had was the very idea of engine braking to slow the craft enough for a simple and safe reentry but that idea included having an abundant amount of fuel on board in order to accomplish that goal and that is a very easy one to dispel as being impractical as your video suggests. Thanks for producing this. It was very well done.

As beautiful as the re-entry footage is, it wouldn't hurt my understanding of the video to show some of the calculations and concepts you're explaining on the screen (maybe in a corner). Thanks for the interesting vid!

I remember watching a documentary about the Apollo program, and they went to an aerodynamic expert and asked, "how do we stop our capsule from melting on re-entry." And he told them "make it blunt." The reason being, as Scott said, the bow shock of air formed by a blunt object pushes the super hot air away from the capsule, and actually insulates it from the hot air. Allowing a relatively small ablative heat shield to protect the capsule from the small amount of heat that gets through. The space shuttle used the same concept, that's why it was all blunt shaped curves on the leading edges. And even then, the heat tiles were essential to insulate the interior of the craft from the extreme heating of re-entry.

What a great video Scott and thanks for posting. I really had the sensation I was along for the ride!

Awesome explanation Scott. The sound(s) are truly amazing (on the original, without commentary)...

Dude, thanks for being you. This is one of the dopest videos during your commentary I’ve ever seen. I’d have never sought this out but we’ve got you to show us something special while learning the best of human exploration

One thing missing from this video is an overlay of velocity and altitude. It would be cool to see the initial entry, climb out of the atmosphere, and reentry to final decent as plots in parallel with the video. (there's likely some national security restrictions to include, but just wishing) Regarding the L/D (Lift to Drag) ratio of space capsules. Apollo had a L/D ratio of 0.52:1 (or ~1:1.92), and a Dragon Capsule has L/D of 0.18:1 (1:5.6). Apollo reentered at 11 km/s, while a Dragon reenters at a 7.5 km/s. Huge differences in amount of kinetic energy, as notes is a factor of mass*velocity^2. Starship will be the largest (reusable) spacecraft to undergo reentry. It too will reenter at ~7.5 km/s.

I remember trying to watch the reentry video and getting bored and didn't finish it but , just having you talk over it made it so much more enjoyable for my brain to watch , you should do this format more often. It really works. Ty

I always wondered! Thank you and happy new year.

Nice to watch the re-entry all the way to the ocean!

A G-Force indicator would be a very fascinating addition to the Falcon 9 telemetry displays of both stages.

Scott, what a great talk. I don't know how many stayed with you, but since I teach an engineering Thermo-Science lab,I was with you every step of the way. Great Job.

Amazing footage, and as always Scotts exceptional video composition and delivery. thanks bro. HNY! :)

Scott talking about rocket science to a backdrop of stunning footage. I love this format!

I WANTED THIS QUESTION TO BE ANSWER FOR SO LONG, THANKS SCOTT FOR THIS. Very interesting and the ratio of lift and drag explained everything

I have always enjoyed your depth of knowledge in these videos ... this one in particular with the step-by-step math included was insightful. Thanks!

I often wondered about that very same question. Thanks for the clear explanation!

Hi Scott the science is fascinating and the video of the Artemis re-entry was really good thanks for sharing! Happy new year 🎉

Excellent video. Setting it over the full reentry video, with some tie-ins, was a great idea. I didn't have the patience to watch the full Orion video when it first came out, but had no problem sitting through it this time. The topic of discussion is fun, and is the sort of thing that gets people interested in space and physics, without being too esoteric.

Before i watch the video, this is a question i have had for probably 25yrs. And you are the first person i have seen bring it up other than myself to one other person about a year ago. So i am curious on what you are about to show me. On to the video... Ok, im back... Thank You Sir. I now understand this even though im not a rocket scientist or engineer and hate hard math :) Very good explanation. I had figured some of it out like more weight for reentry fuel so more fuel and weight and kinda zeros out the idea and the slower you come in the harder the drop without powered entry. But i never thought to DIP in and out like skimming a pond to have time to cool off for a minute and then back in again and so forth.

I was asking a question about this on another channel and they commented back saying you just posted the answer to my question on your channel. So here I am. And thank you for explaining this.

Thank you Scott! I have often considered why we did things the way we do and why not try X- you explained a lot of it in this video.

Little bit surprised you didn't mention (unless I missed it) for the second part, the Japanese project back in 2008 to drop paper airplanes from the ISS. It didn't go anywhere, but the paper planes would've enjoyed a relatively low velocity, survivable-to-paper reentry courtesy their large surface area for drag (and some lift) against their very low weight.

This just blows my mind. I already understand that re-entry is a rough experience to go through but the mathematical knowledge that is understood about it is just beyond me. The way Scott talks about it, although i don't understand the most of it leaves me in awe of how much understanding there is about the subject. How much Scott must put in as regards research & actually understanding then making it into such high quality videos is amazing.

Thank you - I didn't understand specific impulse previously (in spite of KSP), your explanation was great.

Love the content. Loved watching the parachutes and their aerodynamic effect on each other. Scott!? Can you do a video on how parachutes are calculated with regards to size, passtrough vs letting air pass outside it? In the video you can see the air passing outside the chute interacting with its siblings, was mesmerising to watch

Hi Scott. The best gliders are now more than 70:1. My own 40 year old glider does 45:1 without even fitting the tip extentions.

Good Video. I once read about the aerodynamics of reentry capsules and their testings back in the days. It was great to see the different designs and their 'surprise' that the now normal design would be better than something pointy.

Scott, You add so much value to the world! Thanks

that is fascinating. As deadly as the atmosphere can be against us, it is so frikkin thick and it protects us. Just fascinating to listen to. I love to learn stuff. But I am also bewildered because I ain’t no physicist or mathematician. Thank you for re-learning me this concept that I remember learning in high school but here, in a much more detailed manner!

I like the inflatable heat shield idea. I was always intrigued by that style of system being deployed by the ship Leonov to aerobrake in Jupiter's atmosphere in 2010: The Year We Make Contact (Space Odyssey II).

Oh man I've never seen that reentry before that was the full meal deal and it was really cool thank you for sharing

I have absolutely no idea what you talked about. I was too transfixed by the re-entry footage. Amazing!!!

I can’t believe how complicated and precise the reentry maneuvers are for Orion. You can say what you want about SLS, but the Orion capsule has been pretty damn impressive (and RELATIVELY on-time and on-budget) since the start - which is incredible given its size and complexity vs. the Apollo capsules. It is literally the only spacecraft in the world capable of doing what it’s doing.

Love this one! Thank you for reminding me of some basic physics!

That re-entry video is really cool. What I would find most scary if I was riding that would be towards the end, watching those inflated main parachutes hitting each other, wondering if they'd get tangled or otherwise collapse...

Thanks for pulling all this together. It fits together what I knew, confirms my understanding, and adds a bit of math - in an enjoyable way. I guess we'll have to re-enter with a lot of heat until 3010. Maybe we'll have a space elevator running by then!

Like anything in aviation and space travel, the tricky part is not getting up there but rather figuring out to get back on the ground in one piece! Scott great work here, I plan to use this video in my physics classes for work and energy unit and my thermodynamics unit. CP

Love these thought experiments. We should be careful not to say that alternatives are “not possible” when we actually mean not economical or practical. ;)

Just think, if you brought along enough spare fuel that you could decelerate back down without heat re-entry, every ton of that extra fuel you're carrying means 1 ton less of actual payload you can take. If you needed an extra 40 tons of fuel to do this and your payload capacity was like 45 tons, your actual effective payload becomes only 5 tons, and that turns it into an incredibly cost-inefficient vehicle, since your cost/mass ratio goes WAY up.

Now it all makes sense, thanks for explaining it Scott.

I’ve had this question since I first learned about rockets existing - never had a career in any scientific field so never really quested to find the answer but I am ever so grateful to finally get it. Thanks Scott 🙏☺️✌️

Last time I was this early Starliner was still on schedule

Thanks! I had been wondering about this for quite some time.

Many thanks for that analysis. It exactly answered (sadly!) various ideas I've toyed with in my idle moments over the years.

I tried that in KSP 1 a few years ago, and I came with the same conclusion, using the heatshield is the best solution.

A futuristic solution is an orbital spaceport plus a space elevator to get back down to the surface. Maybe in a century or two, if we haven't blown the place up by then . . . sigh. All the best for 2024, Scott. Fly safe!

Delightful re-entry video. Thanks.

I love the fact that the footage starts to look like an old ‘60s reel from the distortion. Sick

Another great video. The best gliders have an LD of 65 or 70. It would be great to see your take on sailplane performance and I'm sure you'd love the experience of flying a Nimbus 4D.

Hullo, Scott Manley here... makes my day. would love to see a video of you describing the physics of skipping off the atmosphere. great vid and happy new year sir. fly safe

I always like these videos - and I chuckled a bit when at 0:30 you point out that the spacecraft has 15 times the energy content of TNT! That certainly sounds more impressive than saying that it has 3.5 times the energy of table sugar, or half again as much energy as bacon grease (sugar and fat have 17 and 37 kJ/g vs. 4 kJ/g of TNT).

This has answered something I'd wondered about for years! Didn't appreciate how much fuel would be used to slow stuff down

In the general scheme of things, the resin composite used for ablative heat shields is the same as that of most automotive brake pads. So it's relatively inexpensive compared to other possible approaches of slowing down. Although it may be modified a bit, it's not like some super exotic material either.

What if you attached butter toast to cat, with butter side being side not attached to cat and other side attaches to back of cat. Since cat always lands on legs and toast butter side up either it spins super fast or levitate which both would provide necessary lift (this is joke)

An informative video with exhilarating visuals~~ thanks so much!

Always wondered this. Thanks for answering a question ive had for 30 years.

Scott did an excellent job of explaining why its not practical to slam on the breaks and slowly drop back into the atmosphere. However once humanity moves past the whole needing a rocket to get into space issue and can travel up out of earths atmosphere like seen in most scifi movies, then yea you can just fly down to earth at slower speeds. But currently, the way re-entry is done is the most practical method.

Forgetting all the impracticalities of creating one, would docking with a space elevator then travelling down solve the issue. I have seen videos on how they are impossible to build, it would be great to have one on how the orbital physics would work if one was built. Great video!

Good video. Good explanations about delta V and what it takes to slow down or stop in space.

Great Scott! Simply 1st rate, man, and wish I could teach physics to the point sharp like that. In any case, reentry physics will become part of my spring semester. Figure I gotta since we live in the Golden Age of Rocket Science

SpaceX Starship would be a good example for the blunt way to do re-entry, using the biggest surface you have to hand. Happy New Year🖖 and thanks for your work, time and passion.

I think this kind of stuff is what KSP teaches in a certain deep way. It lets you try your original thoughts and fail. It makes you *feel* it.

This was an enlightening video. I was trying to come up with some esoteric designs for smoother reentry and the zepplin concept is not far off from what I came up with. I was actually thinking of something like the ships from Arrival, which are zepplin shaped, but are oriented perpendicular to the ground, rather than parallel.

Great video. As an observer of heat shield reentries since the early Apollo days, I learned a lot of specifics in this. And I now know it won't be a hoax if I see a reference to a "Space Zeppelin."

Happy pre new year everyone.

1:30 makes most KSP players smile. But before playing KSP i might have asked that as well. Knowing this stuff vaguely in theory and seeing it (amazingly) visualised on KSP's map screen is a big difference. Kind of relates to people asking why we can't have a Pluto orbiting mission.

Yeah, I also found JP aerospace's concept intriguing, even ordered their book "Floating to Space'. Would be great, to watch a whole video about that, Mr. Manley

I think for the first question it is important to mention that this is basically what the falcon 9 booster does during reentry burn. It's not completely removing reentry, but rather just making it a bit easier on the booster. Now, the reentry speed of the booster is of course much lower than orbital reentry or even lunar, but it is the same basic principle.

I think Scott found a great way to encourage more people to watch the Orion reentry video. I already watched the original but I'm sure many took a pass not realizing how amazing the view was.

So, if plasma is what is formed at the front of the vehicle, can you push against it with some EM fields? That way the vehicle stays clear of the plasma and you get the slowing effect.

Awesome explanation of what is going on during Reentry....all my life watching the Gemini and Apollo missions...I always would say...."just slow down the Reentry speed" and do away with the heat shields.....thank your for putting it in a understandable way....until the next one....👍👍

Great analysis Scott. I'd add one thing. The atmosphere boundary, if you can call it that, isn't exactly uniform. Things which affect the shape and density include the Van Allen Belts (dependent on current magnetic pole position and axial tilt relative to plane of orbit/insertion) large weather systems, ie low pressure regions are rising which push the stratosphere towards the thermosphere which pushes the exosphere, which is what you make make contact with. Then there's solar winds, which push the atmosphere towards the Earth on the sunny side and away on the dark side, such that the exosphere can be over 100km higher on the dark side, depending on the recent strength of the solar wind, which we can't always predict though we are getting better at it. An example of this was when SpaceX lost a large number of Starlink satellites during a launch due to solar wind pushing too much atmosphere in their way during the first few hours after deployment where they don't use their thrusters to avoid damaging each other... I'm going to assume their firmware has been adjusted to shorten that waiting period if they detect delta-v while not operating thrusters!

You can either come in X15 style like a wasp waisted dart (narrower at the wings to reduce vibrations) or like the Shuttle with a surface area to cause drag and reduce speed. Either way if you get your angles slightly wrong you’ll be in trouble.

It’s so cool seeing the capsule coming from orbit to ballistic re entry in a snap, I was trying to wrap my head around the amount of energy shed in this maneuver but still out of my league.

Just subscribed. You have interesting reality based content that i want to see. I actively look for your kind of channel but the YT al-go-rythm wants me to watch reruns or clickbait. Happy i found you and All the best for a Happy New Year!

Whoa , having morning coffee and came across this gem. Fantastic and we'll done. Amist the sea of crap that makes up 99% of UKposts content , this was absolutely wonderful , big thumbs up , an thankyou.