HN Theater @HNTheaterMonth

⬐ asciimike

One of the most amusing books I've read on the subject is "Ignition! An Informal History of Liquid Rocket Propellants" (PDF: http://www.sciencemadness.org/library/books/ignition.pdf, Amazon link: https://amzn.to/2WXzWcp), which discusses how science used to be more fun and chemists basically just mixed lots of super dangerous chemicals together all the time to see what worked.

Related-ish: https://www.discovermagazine.com/environment/in-russias-spac... (again, most rocket propellants aren't exactly great for you).

⬐ tectonic

Looks like you just submitted it to HN too: https://news.ycombinator.com/item?id=23192651 :) Love that book!

⬐ umvi

> which discusses how science used to be more fun and chemists basically just mixed lots of super dangerous chemicals together all the time to see what worked.

Reminds me of the book "Uncle Tungsten", which I highly recommend.

⬐ KineticLensman

Nice. If I could change one thing it would be to rotate the different vehicles as they ascend to emphasise that they are trying to achieve high horizontal speed rather than just altitude. That means they are in orbit when the engines cut off, otherwise they would just drop back to Earth.

⬐ SlowRobotAhead

Which to me is why it’s crazy these have so much fuel and burn so hard - while Virgin’s “plane” gets as high as it does.

Virgin isn’t trying to leave orbit, but it’s still really an interesting comparison to rockets.

⬐ dotancohen

Orbit requires about 7.8 km/s. That an "s" on the end, not an "h". Orbital vehicles travel almost 8 kilometers every _second_ so as to miss the Earth when they fall.

You're right, Virgin's plane gets very high, about one quarter as high as the international space station. But some missions require actual orbit.

⬐ mnw21cam

Yeah. See the first two pictures in https://what-if.xkcd.com/58/ for an illustration. It only takes a small amount of fuel to reach space. It requires a huge amount to reach orbit.

⬐ KineticLensman

> Virgin isn’t trying to leave orbit

It isn't even trying to reach orbit. As soon as the fuel is exhausted it cannot help but fall back to Earth because it hasn't achieved orbital velocity. The passengers get a few minutes at high altitude, enough to experience weightlessness and see the stars.

It's a suborbital lob, a much more polished version of the X-15 in the 1960s.

[Edit - clarity]

⬐ SwiftyBug

What's the purpose of the plane-like rocket? It looks like something that was built to fly in an atmosphere, but it's designed to be in space. Does it eventually re-enter the atmosphere, thus the need to be able to fly in it?

⬐ 9999px

I got very excited to see someone who hasn't heard of the Space Shuttle. It's quite the feat of engineering.

https://en.wikipedia.org/wiki/Space_Shuttle

https://www.theatlantic.com/photo/2011/07/the-history-of-the...

⬐ dotancohen

And I got to feel that I've very old.

My four year old plays almost daily with his model of Atlantis. Both his older sister saw Atlantis at the KSP museum after watching a Falcon 9 launch.

⬐ g3e0

Relevant xkcd https://xkcd.com/1053/

But I also have to admit I cannot fathom how someone could have not heard of the space shuttle? It was only retired in 2011?

⬐ zenexer

The same way someone might not have heard of Yuri Gagarin, the first person to reach outer space.[0] In the US, we only hear about the first person to step foot on the moon. I certainly didn't know Yuri Gagarin's name; I had to Google it. I wouldn't even recognize it if I heard it.

Or the One-China policy.[1]

Or that the United States doesn't have a prime minister. Ever told someone you're from the US and been asked who your PM is? They're not referring to your project manager.

Or that they might actually be the Virgin Islands' president without realizing it.[2]

Or any of the following websites, which are among the top 10 most visited websites according to Alexa:[3]

3. Tmall

5. QQ

6. Baidu

7. Sohu

8. Tmall login

9. Taobao

10: 360.cn

In this case, it sounds like the person who made the comment knew of the space shuttle; they just didn't know much about it or recognize it by name. I bet many readers here could say the same for many of the aforementioned items.

Yet if you went to China and asked about Tmall, I bet you'd get some funny looks. I don't really know for sure, though; I'd never heard of it until today. Sure, I know of Taobao, and I could've guessed that the T in Tmall stood for either Tencent or Taobao, but heck if I know what they do. I misspelled it as `Tmail` initially and only realized my mistake after Googling it.

[0]: https://en.wikipedia.org/wiki/Yuri_Gagarin

[1]: https://en.wikipedia.org/wiki/One-China_policy

[2]: https://www.snopes.com/fact-check/trump-president-virgin-isl...

[3]: https://www.alexa.com/topsites

⬐ PuffinBlue

9 years ago. I have a 9 year old who wouldn't know what it was exactly if asked. But she'd recognise a Falcon landing.

I'm sure there are teenagers out there who are discovering the shuttle just now. This thread might have been started by one.

⬐ NikolaeVarius

Would those same teenagers also not know that the ISS exists or that humans went to the moon 50 years ago?

⬐ ncmncm

Try asking random strangers what stars are, and which is farther away, the stars or the moon.

Prepare to be disillusioned about humanity.

⬐ PuffinBlue

What kind of odd question is that?

If, as your tone implies, you believe that every teenager knows everything and it's not possible for some of them to have not heard or these things, then you must in fact be a teenager yourself.

⬐ wondringaloud

I don't think it's unreasonable to be surprised that a teenager (at least, an American teenager) isn't aware of such a thing. They've managed to get through school without once being shown a photo of the space shuttle? Not one blurb? Never seen it in a TV commercial? Photograph?

⬐ zenexer

It was certainly never mentioned when I was in school. I knew about it, but I bet some of my classmates didn't. And it hadn't even been retired yet.

Challenger was mentioned, but only because I brought in a newspaper clipping for the 20th anniversary.

⬐ SwiftyBug

I have seen it before, but I'll admit I didn't know its name. In my language we call it the "space bus". Maybe my question sounded like I didn't even know what is the Space Shuttle because I'm not a native English speaker and couldn't think of a better way of asking "why does this spaceship look like a plane while others don't?".

⬐ g3e0

Ah I see, my apologies! For what it's worth, your English is so good that it didn't even cross my mind that you weren't a native speaker.

Yes the space shuttle was designed to be partially re-usable. The "plane" bit would come back down to Earth and land on a (very long) runway https://www.youtube.com/watch?v=YOxZsbyjSb8

⬐ CarVac

The Space Shuttle was designed to be able to steer itself during reentry to a large extent, over 2000 kilometers. This is why it has such large wings.

The military wanted to launch it in a polar orbit, gather intelligence, and then land back where it started in a single orbit, which moves 2000 km east of where it was at launch.

⬐ SwiftyBug

So it just falls gracefully rather than actually fly?

⬐ wondringaloud

It is an unpowered flight, not a graceful fall.

⬐ Ididntdothis

It looked like a falling brick when it landed. The angle it came down at was incredibly steep.

⬐ db48x

Slightly less steep than the landing angle of an actual brick though.

Edit: glide slope is the word I was looking for.

⬐ Ididntdothis

I watched it come down over Orlando and it looked like this could never work out. Much steeper than any airplane I have ever seen.

⬐ jaywalk

Depends on the forward velocity of the brick.

⬐ Gwypaas

Really love this paragraph on the Shuttle Training Aircraft wikipedia page.

To match the descent rate and drag profile of the real Shuttle at 37,000 feet (11,300 m), the main landing gear of the C-11A was lowered (the nose gear stayed retracted due to wind load constraints) and engine thrust was reversed. Its flaps could deflect upwards to decrease lift as well as downwards to increase lift.

https://en.wikipedia.org/wiki/Shuttle_Training_Aircraft

⬐ Sharlin

Really drives home how you need to drag any normal airplane kicking and screaming into a regime where it’s as bad at staying in the air as the shuttle was :)

⬐ evgen

A fun little talk that describes the whole process: https://www.youtube.com/watch?v=Jb4prVsXkZU

⬐ JshWright

Aw man, I went to go find this to link it, got caught up in watching it again, and by the time I got back you had beaten me to it...

⬐ macksd

https://en.wikipedia.org/wiki/Space_Shuttle

There's a few things that led to this. Culturally, the American space program has tended more towards the ideal of the "hero" astronaut than others, and there's been some tension between the technical/automated approach and the pilot-astronaut approach to things. I see this as an extension of that. They even considered having pilots manually control the pitch, etc. of the rockets on their way to orbit with the pilots hand on a joystick just following a "recommended" course to orbit.

NASA had explored various ideas for very precise landings, believing that to be useful especially for rapidly-reusable aircraft. There was very serious consideration to having Gemini capsules land with a glider and the astronauts facing forward similar to an aircraft: https://en.wikipedia.org/wiki/Advanced_Gemini#Gemini_Paragli....

⬐ KineticLensman

The book Digital Apollo [0] is fascinating on this subject. It describes the tensions that had to be resolved in terms who had overall authority, e.g. mission control vs. the crew vs. automation.

[0] https://mitpress.mit.edu/books/digital-apollo

⬐ asudosandwich

Tom Wolfe’s The Right Stuff talked about this too, with the Mercury astronauts being called spam in a can.

⬐ JackFr

In the movie version, there’s a scene where the test pilots are deriding the Mercury astronauts as being no better than monkeys that had been sent up in earlier rockets. Yeager shuts them up by pointing out that a monkey doesn’t know he’s sitting on a bomb.

⬐ pjc50

The Space Shuttle was massively handicapped by the Air Force giving it unreasonably difficult requirements. They were the ones who wanted it to be most plane-like. Especially the requirement to take off, capture a satellite (friendly or hostile), and land again at Vandenberg in a single orbit.

⬐ Robotbeat

The Shuttle looks inefficient until you try to design a multi-purpose spacecraft that can return large payloads from orbit. If you tried to do the same thing with a capsule, it’d also be pretty huge and expensive.

And for as expensive as Shuttle was, it had a pretty powerful capacity that mostly made up for it... look at the cost per kg of payload on Commercial Resupply Services to ISS and the cost per seat of Commercial Crew. Shuttle could do about 10 tons of pressurized cargo and 6 (and sometimes even 8) crew, plus about that much down-mass capability, & another robotic arm and airlock. The cost to replicate that capability 1-to-1 is about the same... Of course, that level of capability wasn’t needed as much after ISS was built, and Shuttle couldn’t stay on-orbit for longer than a couple weeks or so. And most importantly, Shuttle was stuck in LEO and could never venture farther and lacked safety features like a launch abort system and was too expensive and unsafe to justify for standard commercial launches in the 21st century.

Not bad for tech developed in the 1970s, tho. The only individual spacecraft (besides Buran) that is comparable in scope and ambition and flexibility is SpaceX’s Starship.

⬐ nickik

The Commercial Crew and Cargo programs are far, far cheaper then the Shuttle.

The Shuttle was one of the most expensive ways of getting to Space BY FAR. As every flight had to be a human flight.

Having a vehicle that could do everything, even when 90%+ of the mission only required a small part of the capabilities made it untenable.

With one simple Dragon like capsule you can replicate both crew and cargo up and down transportation for most of the things you need. If you need to transport big pieces, you can just put them on top of a rocket by itself as most station outside of part of the ISS were built.

The way the Russian designed the Buran and Energia system was far more capable of doing all those things. This was mostly because most in the Russian space flight program thought that Shuttle was a terrible idea and they didn't want to handy cap their next generation rocket to a Orbiter.

Had the Soviets not collapsed, their launch capability would have outstripped the US by 4x.

> Of course, that level of capability wasn’t needed as much after ISS was built

It wasn't needed to build the ISS in the first place. Its rather that the ISS was designed TO REQUIRE the Shuttle.

It would have been far cheaper to use the cheapest commercial rockets and the Ariane to build ISS.

> Not bad for tech developed in the 1970s, tho.

A lot of the technology was great, but great technology doesn't make a great product.

⬐ Robotbeat

What is the price per ton of pressurized cargo for commercial cargo? Price per seat with commercial crew?

⬐ nickik

SpaceX Commercial Crew will cost 55M per seat for NASA. Add to that need need to amortize 2.3 billion in development financing that NASA has given out (includes 2 astronaut flights). SpaceX can sell the other seats on the capsule.

They payed almost 90M per seat for Soyuz at least in the last couple.

In comparison, the program cost of Shuttle per flight was 1.5 billion per flight. They would almost never fly more then 4 people on those flights (just as Dragon can also take 7 people, but NASA only takes 4). And the Shuttle was not getting cheaper and the flight rate was not getting faster.

NASA of course has 2 contractors the other was 4.2 billion and the per seat cost is somewhat higher, not sure exactly with the numbers, like 70M or so.

What the per seat cost overall cost are we will see over time. After the initial maximum flight Commercial Crew contracts run out, NASA can renegotiate after that initial contract and likely get a lower per seat price then.

We will see what the end-to-end lifetime per seat cost are for NASA.

I can't give you perfect numbers for perfect Cargo without a lot of research. It depends if we are talking CRS1 or CRS2 contract and there are 3 providers that are all somewhat different, different proportions of up-mass, down-mass and other capabilities, some that the Shuttle didn't have.

The Shuttle could theoretically transport a huge amount of unpressurized cargo but if you are not building a Space station its hard to actually utilize that space fully. So an analysis would have to include the actual payload and so on. That is getting to complex here.

What NASA values seems to be having much less risk on one system. Having different vehicles on different rockets and being able to deliver what they want when they want it and get it back when they want it back.

⬐ Robotbeat

SpaceX charges about $46m per ton of upmass. So for the ~10 tons of upmass per mission, that's $460m. (Plus I think Dragon is pretty volume constrained compared to the MPLM that NASA used with Shuttle.)

SpaceX's price per seat is $55m, Boeing is $90m, same as Soyuz.

And it's false that "[t]hey would almost never fly more then 4 people on those flights", as you can see from the list of Space Shuttle missions: https://en.wikipedia.org/wiki/List_of_Space_Shuttle_missions (5th column lists number of crew... To ISS it's usually 7 crew but sometimes 6 and only one time 4). The reason why is they could do a "crew surge" where they could get a whole bunch of work done on Station for a couple weeks and then the extra folk would go back down.

And it's false that Dragon can now take 7 people... They switched to 4 because of the need to change the orientation of the seats to ensure safe splashdown and the 7 seat configuration no longer fit. There were some configurations of Shuttle that would've allowed like 74 additional passengers, too, with a passenger module, but they never flew that variant either.

So again, 7 seats at Boeing's $90 million would give an additional $560 million per mission (or $385m for SpaceX), for a total of $1.1 billion (or $845m), not counting the capaiblity of the extra airlock or the extra robotic arm for servicing capability, plus the ability to take up full ISPR racks or return large pieces of external cargo or...

...So again, even with the $1.5B figure (which includes a ton of overhead at KSC and JSC and elsewhere that would probably have to be covered in some other way), it's still pretty competitive with commercial crew. And that's not counting the NASA side of the commercial crew program, which is substantial.

So I'm with you on commercial crew and cargo being good. I think two or more providers is a more robust system, and I agree it would've been possible to build a big space station without Shuttle (the Russians did it). But the more you dig in to Shuttle's capabilities, the more expensive it looks to replicate. Shuttle really wasn't that bad considering how compromised the design was by zipcode engineering and inability to effectively cost share with commercial or military stuff (later on) and being essentially a traditional government contractor run system.

...the all-in price per launch of Shuttle may have been about $1.5billion, but the marginal price was around $500 million. If they had ever used that 74 passenger module (plus 6-9 crew), that would've been a marginal price per seat of just $6 million... Not too bad, really.

But it was never cheap enough or robust enough to launch often enough to ensure safety without launch abort. Hopefully Starship will change that, enabling a marginal price per seat of something like $100,000 for a trip to orbit...

⬐ woodandsteel

Does your cost analysis factor in inflation?

⬐ g3e0

This really makes it easy to see that the SLS (far right) is derived from the space shuttle, with the orbiter removed and the payload placed on top instead.

⬐ 0xffff2

It totally does. I knew this fact already in the abstract, but the imagery in the video really drives home at a more intuitive level just how similar they are.

⬐ dotancohen

I'm sure that helped reduce the costs and timeframe associated with developing and building it, then.

⬐ onemoresoop

I enjoyed this with my 2yo son. He loves rackets and calls them Kiko. Surprisingly he had the patience to watch the video till the end:)

Thinking back, I was quite fascinated by rackets and only when I was 7-8 did I get across a book on rockets with very colorful fold out posters in it. I think it’s great to have all this educative material on youtube, I will curate some cool playlists for him to watch and learn things.

⬐ ardy42

The Saturn V and SLS engines burn for significantly longer than the Falcon 9 Heavy's. What's the significance of that? I assume it means they can lift more into higher orbits, but I'm not sure.

⬐ lutorm

The animation of the FH appeared to show that the Mvac on the second stage cut out really early. I don't think that's accurate, SECO on the FH demo flight with Starman was at about T+9 minutes.

⬐ mr_toad

It’s easier to recover the boosters when they are moving slower.

⬐ oconnor663

The Saturn V and the SLS are as big as they are because they're designed to carry astronauts to the Moon (or farther). I don't think the Falcon Heavy can do that without using multiple launches and meeting / refueling in orbit.

⬐ Robotbeat

Falcon Heavy could do a single-launch loop around the Moon with Dragon.

⬐ d883kd8

Very interesting for me to see how much shuttle legacy is present in the planned SLS. I knew it was using the same engines but based on the timing here it seems to follow a very similar flight plan with the boosters jettisoned at the same time and the 1.5 stage running out around the same time too.

⬐ marmshallow

I'd also love to see a comparison of the rockets' altitude & velocity thru the launch

⬐ wayneftw

I don't know anything about space or rockets, but...

Why is a car housed atop the third rocket? You can see it around 4 minutes after the housing is jettisoned - https://youtu.be/su9EVeHqizY?t=239

(I was just about to post this question when I decided to just look it up - I vaguely remember hearing something about this - https://en.wikipedia.org/wiki/Elon_Musk%27s_Tesla_Roadster )

⬐ None

None

⬐ wondringaloud

Because billionaires with large egos exist in the wild.

⬐ nickik

Or because they had to do a test launch and launching a block of concert would be boring. Why not do something that gets some more media attention and thus exposes far more people and kids to Spaceflight.

But its defiantly just because of his ego, not thought went into it beyond then that.

⬐ OnlyOneCannolo

Because Elon Musk launched his personal Tesla into space on the Falcon Heavy test flight.

https://youtu.be/A0FZIwabctw https://youtu.be/wbSwFU6tY1c

⬐ mannykannot

If only there were a teapot in the trunk...

https://xkcd.com/1866/

⬐ Yizahi

Maybe there was. We can't know now :)

⬐ mannykannot

Indeed, but as Russell himself pointed out, the burden of proof would rest on anyone claiming it to be so!

⬐ thatguyagain

Very cool! For someone who knows absolutely nothing about rockets, this makes it look so much more primitive for some reason. Just these tubes filled with fuel.

⬐ Ididntdothis

Fundamentally the purpose of a rocket is to throw mass behind it very quickly. The idea is pretty simple but the implementation turns out to be quite complex.

⬐ pjc50

Almost all the engineering magic and weight is at the bottom: nozzles to handle very high temperatures, high-pressure high-speed turbopumps, and so on. The falling Falcon stages have the aerodynamic stabilisation of a shuttlecock, and their low center of gravity helps them be stable on fairly small legs.

⬐ dotancohen

As someone who knows quite a bit about rockets, they really are for the most part this primitive. Just these tubes filled with fuel, with a few volts of angry pixies at the top controlling a few degrees of gimbaling at the bottom.

⬐ munchbunny

That's pretty much what rockets are: massive fuel tanks and a ton of hardware to keep the resulting explosion under control.

The really hard part is keeping the explosion intentional and pointed where you want it to go.

⬐ amelius

Yes, we'll have to find a new phrase for "rocket science" :)

⬐ twicetwice

As others have said, that's basically the case. Most of the complexity, though, is at the bottom, in the engines. Absolutely incredible machines designed to withstand—and control—incredible forces. Turbopumps spinning at tens of thousands of revolutions per second. Insane amounts of heat that need to be cooled so the engine bell doesn't melt. Handling cryogenic fuels (liquid oxygen is very, very cold!) at very high pressures, moving them at very high speeds.

One failure mode, out of the many many possible failure modes, that's particularly interesting to me is that if the pressure in the pipes going into the turbopumps (which push the fuel into the combustion chamber fast enough to keep the explosion going) is too low, then you'll get cavitation on the back of the turbopump blades, and the forces from that will destroy the turbopump in under a second. Kaboom.

Oh, also, these pumps have to spin so fast that they themselves are driven by essentially little mini rocket engines.

For a visual depiction of the complexity of rocket engines, check out SpaceX's Raptor engine, arguably the most advanced engine being produced right now: https://imgix.bustle.com/uploads/image/2020/4/6/c1349369-162...

I'm no rocket scientist, though, just an interested amateur. Real rocket scientists please correct me if I got anything wrong!

⬐ lutorm

Turbopumps spinning at tens of thousands of revolutions per second.

This is actually not true. These turbopumps are quite large and spin fairly slowly. The design RPM on the F-1 turbopump appears to have been 5500 RPM, for example. (That's not to say they aren't complicated, because they were using 55,000 horsepower to push the propellants into the engine.)

⬐ elteto

Not all of them! The Merlin turbopump spins at a whopping 36k RPM!

[0] https://en.m.wikipedia.org/wiki/SpaceX_Merlin#Turbopump

⬐ lutorm

36,000 RPM is 600 RPS, which is still aways off from "tens of thousands".

⬐ twicetwice

Oops, you're totally right, I messed that up. Too late to edit the parent unfortunately. I think it's certainly still impressive, though!

⬐ twicetwice

Yup, that's what I was thinking of... I learned most of what I know about rockets from /r/SpaceX and related places! :)

⬐ 205guy

And another TIL from reading the comments on the video:

"Question: Are inertial forces required, and incorporated into the designs of rockets, in order to keep liquid fuel at the bottom of each tank?"

Reply: "They are in constant acceleration except when staging or after a shutdown before a re-start. They use ullage motors to accelerate the rocket just enough to settle the fuel (either small solid rockets or reaction thrusters) when they are in zero g."

Reply 2: "Apart from Ullage Motors you can also do "Hot Staging" where you light the next Stage while the current one is still burning. That's why a lot of Russian Rockets don't have this open Interstage Sections where you can see the Engines instead of Interstage Fairings."

https://en.wikipedia.org/wiki/Ullage_motor

⬐ ashtonkem

Some rockets also pressurize their fuel tanks with Helium for similar reasons I believe, including the Saturn V.

⬐ shadowgovt

It's fascinating to observe how little fuel is left in the Falcon Heavy lower stages when they're jettisoned. That reentry profile really gets to take advantage of atmospheric drag to sink all that kinetic energy.

⬐ gorgoiler

This is wonderful.

I’ve never really understood how solid fuel boosters work. Are they filled with something granular like sand, that empties down the rocket tube?

The video makes it seem as if the entire tube is on fire at the same time.

It’s also fantastic that an asymmetric vehicle like the Space Shuttle was ever built. What an outlier it seems, amongst the more, I suppose traditional looking rocket designs in this video.

A very poetic leap, as well, to think that the same orbiter that climbs under so much power is the same vehicle that glides into land without power, all the way back from orbit!

⬐ franzb

As I understand it, the solid propellant is hard and hollow on the entire length: https://en.wikipedia.org/wiki/Solid-propellant_rocket. Also check this wonderful Applied Science video: https://www.youtube.com/watch?v=TLPWqCMb7DE

⬐ PostOnce

This is my all time favorite animation of how a solid rocket works https://i.imgur.com/E7J8pxF.mp4

so yeah it is all burning at the same time

In the OP's video, it looks like the fire is magically coming out of thin air... it'd be hard to do the animation style I linked at the distance in OP's video though, so I'm not sure how they could better animate a solid fuel rocket

⬐ gorgoiler

Aha! Very nice! So this is why solid fuel boosters are ejected before they’ve burned out - because they will eventually burn out to the edges of the tube and the whole thing will start to glow?

⬐ akincisor

If you've ever used a firecracker rocket it has solid fuel in exactly the same way. It just burns from the inside out (I think) to ensure that the rocket's center of gravity doesn't change as the burn progresses.

⬐ mr_toad

> traditional looking rocket designs

It’s ironic how much Starship resembles a 1930’s pulp-fiction rocket.

⬐ nickik

Its not really like sand, its more like toothpaste that is dried up. Its essentially a rocket fuel where the fuel and the oxidizer is premixed in the same 'paste'. This makes clear why its a pretty dangerous substance. You need to be very careful manufacturing those, as they can explode pretty easily.

The way it works, is that it burns from the insight out, like a hollow candle. The trajectory of the booster is basically molded into the hole in the middle. Once you light in on fire, the booster is gone fly its trajectory whatever you do.

Here you can see all that pretty well:

https://www.youtube.com/watch?v=k_JULlA_9Mo

⬐ SergeAx

Solid rocket boosters of Space Shuttle and SLS are quite similar indeed:

https://en.m.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_B...

https://www.northropgrumman.com/space/nasas-artemis-program/

⬐ deanCommie

Always a good reminder, what people think about as "rockets" is really mostly fuel tanks.

I mean intellectually people know that. Rocket = "Engine" + "Fuel tank".

But I still think that when people are imagining the awe-inspiring power of a massive rocket carrying humans into space, they're not dwelling on the fact that the majority is just a big cavernous vessel for fuel.

⬐ boublepop

Content like this and the amazing contributing comments here is what I love most about the internet. When I woke up this morning I did not expect to spend hours reading and watching videos about space rockets, but here I am all the merrier for it. Thank you!

⬐ Nokinside

Saturn 1 (SA-5) Camera Inside Kerosene Tank https://www.youtube.com/watch?v=fL-Oi9m2beA

⬐ LordHeini

Time to play Kerbal Space Program again :)

⬐ apatheticonion

Are reusable rockets more cost effective than disposable (or recoverable by parachute) solid rockets?

⬐ gloopyfork

I have always wanted to see this! Intuitive visualizations of engineering marvels are in short supply, and rockets are one of those tech that operates outside everyday (physics) assumptions.

https://www.youtube.com/watch?v=su9EVeHqizY Since space-capable launch is generally “dual use” for ICBMs, watch how the end of the world as we know it proceeds by the beautiful operation of precision engineered machines.

⬐ SeanFerree

Very cool!

⬐ unnouinceput

This animation doesn't do enough credit to Saturn V. Tell me again off them 4, which one carried people to the moon and back?

⬐ dotancohen

That is not the purpose of the video. I worship the Saturn V as much as anyone, seriously not a week goes by that my kids don't hear a story out of me featuring that rocket, but the video does it's purpose.

If you really to give more (rightfully deserved) credit to the Saturn V, then in fact you can see how much more payload and propellant is on top of the still-firing S-IVB at the end of the video.

⬐ NikolaeVarius

None of them. The Saturn 5 was discarded after launch.

⬐ dotancohen

The S-IVB performed the TLI maneuver.

And by any definition, the Saturn V carried the entire stack into orbit. From orbit you're halfway to anywhere.

⬐ hoorayimhelping

Red is kerosene, blue is liquid oxygen, orange is liquid hydrogen, the fuel that looks like fire is solid fuel (think compressed gunpowder).

Left to right: Saturn V, Space Shuttle, Falcon 9 Heavy, SLS (still under construction).

2:22, you hear Neil Armstrong say "inboard cutout," that is the center engine shutting off to limit the thrust, and therefore G-forces the astronauts felt. As fuel ran out, the rocket stack would weigh less and so the rocket would push harder. By the time the main engine cutoff, the Saturn V was pulling 4 and a half Gs.

Also, just noticed the SLS keeps its launch escape tower (the big needle on the top of the rocket - see this: https://www.youtube.com/watch?v=AqeJzItldSQ) - this wouldn't happen in a real flight. The flight plan calls for ditching than when it's not longer useful - you can hear the Apollo 11 call saying, "tower jettisoned."

⬐ NikolaeVarius

Wasn't sure why the SLS escape tower stayed on while the S5 was shown jetissoning it

⬐ bfieidhbrjr

So the SRBs don't burn from the bottom up?

⬐ SAI_Peregrinus

Nope, inside out. They're hollow, and the top section has a star cross section rather than cylindrical. The goal is to keep an overall constant pressure for the entire burn time.

⬐ bfieidhbrjr

TIL. That's amazing, thanks.

⬐ wondringaloud

Which piece of it is amazing?

⬐ matt-attack

If you ever used a toy rocket as a kid, the engines had a long hole down the middle. Apparently the Space Shuttle uses the same idea:

https://www.siriusrocketry.biz/ishop/images/EstesStandardEng...

⬐ dTal

Estes black powder motors are in fact end-burners:

https://farm8.staticflickr.com/7457/12472921013_aa92200267_k...

⬐ Sharlin

Nope, they burn from the inside out! The propellant does not constitute a solid cylinder but has a hole in the center going through the whole thing. Ignition happens at the top and the burning (very rapidly) spreads from there to the whole inner surface.

⬐ m4rtink

You can get even fancier things with the inner hole to inflence your burn profile. For example, it can look like a star - this will give you high initial thrust as the burn area is big. As the inner spokes burn off, the burn front will star to approximate a circle, reducing thrust. This can be important to get you rocket the initial acceleration it needs to lift off but to avoid excessive acceleration destroying the rocket later on (as it it burning the rocket get lighter but the solid motor thrust would nornally stay the same or even grom slightly, due to the circular burn front being a bigger and bigger circle).

⬐ 205guy

Other comments have already mentioned the various patterns. What hasn't been mentioned is that end-burners (as they're called) are possible, but have the downside of heat on the casing and change in center of gravity.

Coming from model rocketry myself, I had the same question, so I went straight to wikipedia to find out: https://en.wikipedia.org/wiki/Solid-propellant_rocket

Somehow I thought that the combustion of the propellant had to be inline with the thrust, but TIL there is a combustion chamber, and it's the ejection of the combusted gases through the nozzle causes the thrust.

I like hearing other people's experience with model rocketry. It's interesting because I experienced it more as model building (assembling and decorating) with a fun day of launching and running after them. I never got into the physics of the flights (other than lighter==higher) or even thought of investigating propellant properties--geometry and chemistry--as amateur rocketry does. I guess nobody told me "you can make your own engines if you want," but even then I'm not sure I would've pursued it.

⬐ clarkmoody

Fun fact: the shape of the propellant determines the thrust curve as it burns, as thrust is proportional to the surface area burning. And as material burns away, the surface area changes according to the pre-burn geometry.

StackExchange pictures and discussion: https://space.stackexchange.com/questions/4153/could-3d-prin...

⬐ EvanAnderson

I love recalling my feelings from the day somebody told me that thrust profiles related to surface area of the burn in solid fuel rocket motors. (That's kind of an odd sentence...)

It's a silly thing little, perhaps, but it helped shape my personality.

When I got involved with high power model rocketry I'd been flying little Estes kits for years. I had rudimentary understanding of aerodynamic forces and testing for stability, and had hacked around with flight simulation code cribbed from G. Harry Stine's "Handbook of Model Rocketry". I was young and thought I "knew stuff". Somebody at a high power launch remarked offhandedly about the difference thrust profiles of an end-burner vs. a core-burner. After I digested it I began to reflect on the visceral sense of how little I really knew about rocketry, and the world in general, that I felt.

It was a seemingly simple piece of trivia about a topic that's not particularly important in my day-to-day life. It was, however, one of those deeply humbling "unknown unknown" moments. I've grown to absolutely adore the feeling of learning about new, uncharted depths in my knowledge because it means there's something new to learn about. The lesson about false confidence and humility was also a really good one. I hope it was a lesson that changed me for the better.

⬐ dTal

That's funny, my experience was almost exactly the reverse of yours.

When I first got into model rocketry, I was inundated with technical material. NASA had a huge variety of short technical briefs on things like stability, drag coefficients, etc - I think they gave them out for free to anyone who asked - and I had a fair collection. Unfortunately the mathematics in in them was far too much for 8 year old me, and I wasn't really able to use them in earnest for anything. Rocket science - proper science - seemed unapproachably complex.

But a few years later I was given a copy of G Harry Stine's book, and it was like the doors were thrown open. Everything in it was hugely practical! And perfectly readable to 11 year old me. One great big book that said "you can totally do all this, and here's how". I credit the BASIC code in the appendices with helping get me into programming. I spent a long time painstakingly translating one of them into TI-83+ BASIC.

So the lesson that I learned was the opposite as yours - it's easier than it looks!

⬐ EvanAnderson

My revelation wasn't that it was difficult or easy-- it was that unknowns lurk, in vast numbers, in places you don't even know exist, let alone don't know to look.

It sounds easy, with hindsight, to say "Of course the burn profile of the fuel grain would determine the the thrust curve". The idea of fuel grain burn profile just simply hadn't occurred to me. Sure-- I knew motors had total and specific impulse but, I grew up on Estes motors as "black boxes" and never thought about motor manufacture or that performance could be engineered. I never thought about the motor as anything more than "put an ignition source in, get energy out".

I know I've had a lot more of these moments. This was just a memory evoked by the parent post. I'm having trouble coming up with another of these "deep holes that look shallow, or don't even look like a hole at all" moments immediately to relate a second anecdote.

These shallow-looking deep holes clearly exist in large numbers. By their very nature we can't know how many there are. They're fractal, too. Inside each one are more similarly-appearing (or not appearing) holes to go down.

That idea might trouble some people, but it's very exciting to me. The only troubling bit is knowing I have a finite period explore the space of knowledge and a limited capacity to understand. That doesn't discourage me, though.

⬐ _curious_

Great info, thanks for adding, you are helping ;)

⬐ SAI_Peregrinus

In the video SLS keeps its launch escape tower until 8:13, then jettisons it. I do think that's too long, I wonder where they got that. If it does stay for so long, I wonder why.

⬐ CydeWeys

I think they're retaining it until just after the final stage separation, i.e. it will be used if that stage separation goes poorly.

⬐ None

None

⬐ sandworm101

It was likely kept longer than needed/useful because they didn't want to run into it. If the rocket is still accellerating it could theoretically catch up to the ejected tower. The probably kept it until they knew its velocity after release would be greater than the capsule's orbital velocity.

⬐ endogui

Isn't the escape tower designed to have a slight radial thrust component? The problem with avoiding an oncoming booster is the same when triggering the escape sequence for human passengers. I mean, there is an automatic self-destruct, but that must not be the only contingency.

⬐ sandworm101

Yes but without the mass of the capsule that 'slight' radial thrust isn't so slight And the CG is totally different. The worry is that an ejected tower might spin/spiral or even take a pinwheel motion rather than fly properly out of the way.

⬐ m4rtink

Without the weight of the capsule the acceleration of the escape tower is also much higher. So with even a bit of radial acceleration it should get away from a possible collision course pretty quickly.

⬐ outworlder

It "should". That's not good enough.

⬐ clarkmoody

Well, the whole point of the escape tower is to accelerate the capsule away from the rest of the vehicle. So the tower accelerating by itself should have no issue getting out of the way.

⬐ catalogia

I don't know how SLS's escape tower works and I expect your right with respect to it. However that's not true of all escape towers. The escape tower used for the Mercury-Redstone missions at least was meant to only work when the rocket below it was no longer accelerating.

This became a factor during the (unmanned) Mercury-Restone 1 incident, where the launch tower flew off when the rocket was still on the launchpad, leaving the capsule behind on the rocket because the capsule was only designed to detach when the rocket was in freefall (it wasn't in freefall, because it was still on the launchpad.)

⬐ philwelch

The Apollo escape tower thrusts at an angle specifically to prevent that.

⬐ sandworm101

The lateral componant was to pull the capsule out of the flightpath of the rocket. The total accleration of the tower+capsule was miniscule compared to the rocket overall. If it didn't move left/right a bit then the rocket would easily catch up.

The thinking at the time was that, without the capsule attached, the tower might not fly as planned. It could be unstable in the thin up atmosphere. It might spin. That lateral thrust, withough the mass of the capsule, might cause it to spiral, leaving it floating out in front of the accelerating rocket.

⬐ CydeWeys

We don't need to guess about these things. They keep it until after second stage separation because they might need to actually use it for an abort up through that point. Here's a link confirming that the Saturn V launch abort system was retained until 30 seconds after the second stage separation for exactly that reason: https://www.hq.nasa.gov/alsj/CSM15_Launch_Escape_Subsystem_p... I couldn't find such detailed information on SLS, but it's a similar rocket with the same design philosophy and this logic likely applies equally.

The acceleration of the launch abort system on its own, when it's not dragging the entire capsule with it, is double digit gees. The main rocket is not going to catch up to it and run into it.